CEG Workshop on Strategic Aspects on Management of Radioactive Waste
and Remediation of Contaminated Sites
Aronsberg Conference Hotel, Stockholm, Sweden, 27 April 2006
Strategic Considerations in the Remediation of contaminated Sites
in the United Kingdom
L R FELLINGHAM
RWE NUKEM Limited, The Library, 8th. Street, Harwell International Business
Centre, Oxfordshire, OX11 0RL, United Kingdom
ABSTRACT
The active management of land and the environment, which has become contaminated with
radionuclides, is a small but growing field. Worldwide the activity has been dominated by the
rehabilitation of uranium mining and milling sites and areas affected by major nuclear
accidents, such as Chernobyl and Khystym. To date most of the sites in or associated with
the UK have been small in scale and have generally involved natural radionuclides.
However, with the decommissioning of large areas of many old nuclear industry sites and
those associated with the development and production of nuclear weapons and the
operations of nuclear submarines, the scale of these operations is set to rise very
significantly. This paper addresses key considerations in managing the rehabilitation of
radioactively contaminated sites. It illustrates their significance through examples ranging in
scale from a few hectares to thousands of square kilometres. The first example deals with a
former waste storage and processing area at Harwell Laboratory. The site is on the edge of
a village with immediately adjacent population and in a region, where the capital value of
land is high. The second covers a risk reduction rehabilitation programme at the former
British nuclear weapons test site at Maralinga in Australia. In this case the site is remote, the
population is sparse and lives a native, semi-nomadic existence, and the economic value of
the area is currently low. The third considers the area outside the 30 km exclusion zone
around the Chernobyl nuclear reactor site. The region is large with significant population and
the surrounding land is agriculturally very productive. It assesses the potential for costeffective countermeasures to reduce aggregate doses received.
1
INTRODUCTION
The active management of land and the environment, which has become contaminated with
radionuclides is a small but growing field in the United Kingdom and worldwide. The
contamination is associated with both naturally occurring and man-made radionuclides. It
has many causes ranging from poor waste management and process practices, leaks,
accidents, deliberate action as with the testing of nuclear weapons, and past lack of
appreciation of the radiological significance of many naturally occurring minerals.
The largest affected areas are associated with uranium mining, milling and tailings
operations. These are significant for all of the major uranium producers, such as the USA,
Canada, Russia, Australia, South Africa and Namibia. They are also significant for several
European countries, particularly for those in the former Soviet bloc including the Czech
Republic, Germany and Bulgaria, and to a lesser extent for France, Spain, Italy, Sweden,
Hungary, Slovakia, etc. Contamination from these sources has never been significant in the
United Kingdom, for although very low-grade uranium ores do exist, they have never been
exploited commercially.
The next major areas are sites associated with the development and testing of nuclear
weapons. For the UK nuclear weapons programme all of these sites were located overseas,
initially in Australia on the Monte Bello Islands and at Emu and Maralinga in South Australia,
then at Malden and Christmas Islands in the Pacific Ocean and finally at the Nevada test site
in the USA. Elsewhere contamination has occurred as a result of accidents involving the
handling of nuclear weapons as with the US Air Force at Palomares in Spain and Thule in
Greenland.
The nuclear power industry is itself a source of contaminated sites. Many of its sites are now
over 40 years old and as with many other mature industries contamination has occurred to
varying degrees on its sites. This contamination has frequently arisen from poor practices for
the handling and storage of unconditioned and particularly liquid wastes. Examples of this
are the leaks from the B38 silo at Sellafield, the contamination of the Seascale beach by
traces of solvents discharged through the Sellafield pipeline and more recently the particulate
contamination reported at Dounreay.
Reactor accidents have given rise to contamination in a few cases. These have been
dominated by the unique scale in area and activity release of the Chernobyl accident. This
has affected tens of thousands of square kilometres, predominantly in Belarus, Ukraine and
Russia, but it has also led to 137Cs contamination levels of ~ 1 Ci/km2 in parts of Cumbria and
North Wales. Most other reactor accidents, such as the fire in Windscale Pile 1 in 1956 and
Unit 2 at Three Mile Island, only resulted in releases of short-lived activity with no long-term
contamination problems.
Naturally occurring radionuclides have caused low-level contamination at many sites,
including several in city areas. Radium was widely used for its luminising qualities in small
workshops around the world, especially during World War II, when it was extensively used by
the military for luminous instrument dials in aircraft, ships, vehicles, etc. Thorium was also
widely used in the era of gas lighting for incandescent gas mantles and is still used in
electrical filaments, welding rods and as a hardener for magnesium alloys. Uranium has
been used in metallic form on account of its very high density in aircraft counterweights,
depleted uranium munitions, as shielding and as a recombination catalyst in some old gas
works, etc. Sites contaminated with these elements have been poorly recorded and continue
to be found. Some sites used for manufacturing and storing modern luminising sources,
such as tritium, have also been contaminated. Rare earths occur naturally in certain tin and
phosphate-bearing ores and some sites used to manufacture and store phosphates, e.g. in
detergents, fertilisers, etc, and phosphoric acid have become contaminated with uranium,
radium and thorium.
2
CHARACTERISATION
The characterisation of contaminated sites is a very important component of any
management programme. It can also be a significant part of the overall cost of any
restoration programme, typically being of the order of 10%. Guidance on best practice for
site characterisation is available from the Safegrounds project(1,2), the IAEA(3,4) and British
Standards(5,6). Characterisation can have several functions and it is important to recognise
these from the outset and to plan and optimise the characterisation programme to satisfy
their various requirements. The purposes of characterisation include:
i) determining the current level of hazard posed by the site as a precursor to
regulatory/decision making on any future action, including emergency responses;
ii) assessment of the long-term nature of the hazard posed through risk
assessments/pathway analyses;
iii) input to assessing, selecting, planning and implementing long-term management
approaches, including any potential remedial work and clearance criteria; and
iv) input to categorisation of wastes resulting from any remediation with a view to
minimising volumes and costs and utilising available disposal routes.
The first stage of any characterisation programme should include as extensive a review as
possible of the past history of the site in terms of previous activities carried out there:
i) likely radionuclides present, concentrations and distribution;
ii) other contaminative processes and industries present or around;
iii) local and regional backgrounds;
iv) geology and hydrogeology of the site and region;
v) soil types present;
vi) vegetation;
vii) land-use;
viii) population distribution,
ix) population habits, etc.
The scale of the contaminated area is also a major consideration in determining the
characterisation approach. Sites can vary enormously in size ranging from a few tens of
square metres for a 226Ra-contaminated former luminising facility through a few tens to
hundreds of square kilometres as at a former nuclear weapons test site, such as Maralinga,
to 50 000 km2 around Chernobyl. With small-scale sites foot-based surveys can be used
very cost effectively. This approach has been used for the vast majority of sites in the United
Kingdom, including the Southern Storage Area at Harwell.
As the scale increases, so the practicability of this approach decreases. Provided a
significant γ source is present, vehicle- or aerial-based surveys are very cost effective. With
aerial surveys the exposure time is very limited, even if helicopters are used as in the survey
undertaken at Maralinga by EG&G(7). The spatial control and particularly the height require
careful control. As a consequence the resolution is more limited. However, the advantage is
that large areas can be scanned relatively quickly to provide a general view of the extent and
levels of contamination. Vehicle-based surveys with GPS position location are now capable
of considerably greater precision, but are still limited to detection levels ~ 10 kBq/m2,
dependent on the natural background. Where a significant γ source is not present, then
discrete surface and core sampling have to be undertaken to obtain an estimate of the
contamination distribution. The limitations of this approach become significant, when the
contamination is a result of discrete fragments rather than a homogeneous distribution. In
this case the use of a statistical sampling approach is very important, but it may still require
very large numbers of samples, dependent on particle frequency and size.
3
ASSESSMENT OF RISKS
The next stage of any potential rehabilitation programme is to assess the risks currently
posed by the contaminated area and their likely evolution with time. To determine the best
risk reduction strategy, it is very important to determine the various exposure pathways and
their relative importance(8). This is best achieved using a focused, staged quantitative risk
assessment. The latter would examine the potential contributions made both on- and off-site
by the direct irradiation, inhalation and ingestion pathways to workers, the general public and
members of the critical group. Such studies invariably require additional data as they
proceed. Hence, the merit of a staged approach with an initial scoping study being used to
identify the key exposure pathways associated with any site. The results of this study can
then be used to focus additional characterisation work on those areas, which will yield the
key data required for a more comprehensive risk assessment. Once the baseline level of
risk posed by the current state of contamination of any site is established, the risk
assessment methodology can be applied to determine both clean-up levels required to
achieve a given level of residual risk and the level of risk posed by the site after different
rehabilitation strategies have been implemented.
Any assessment involves four main components:
i) source analysis. This addresses the problem of deriving the source terms that
determine the rates at which the contaminating radioactivity is released into the
environment. This rate is a function of the layout of the contaminated area, the
concentrations of the radionuclides present, the rates of ingrowth and decay of the
radionuclides present and their rates of removal by physical processes, such as
surface erosion and leaching;
ii) environmental transport analysis. This addresses the problems of identifying
environmental pathways by which the radionuclides can migrate from the source
areas to others where they can directly or indirectly affect human populations, flora,
fauna and indeed material property. It also determines the rates of radionuclide
migration along these pathways and hence determines the relative significance of
each;
iii) dose/exposure analysis. This addresses the problem of deriving dose conversion
factors for the radiation dose that will be incurred by exposures to ionising radiation;
and
iv) scenario analysis. The parameters, which control the rates of radionuclide release
into the environment and the duration and extent of human exposure at any given
location, are determined by the patterns of human activity. These activities include
workers in the area and residing nearby, the general public, etc., as well as potential
future scenarios for the use of the sites, e.g. for potential housing, farming, recreation
uses, etc.
The main pathways by which humans may be exposed to the contaminants are then
considered in the assessment through models. Radionuclides can migrate by each from a
source to a point, where humans, etc, can become exposed. Some of the components of
these can occur as segments in more than one pathway. Thus contaminated ground or
surface water can contribute to the human drinking water pathway. It can also contribute
through the food chain, if contaminated water is used to irrigate crops or water livestock. The
pathways include:
i) External radiation
- Ground
- Volume source
- Surface source
- Air
- Dust
- Radon and its decay products
- Other gaseous airborne radionuclides
- Water
ii) Inhalation
- Dust
- Radon and decay products
- Other gaseous airborne radionuclides
iii) Ingestion
- Food
- Plant foods, e.g. vegetables, cereals and fruit;
- Meat, e.g. sheep, cattle, goats, etc;
- Aquatic foods, e.g. fish, crustaceans and molluscs;
- Water
- Groundwater, e.g. through wells;
- Surface water, as through rivers, lakes, etc;
- Soil
- pica;
- associated with food intake;
- injection through wounds
The risk assessment can identify the magnitude of the contributions to the overall risks to
various potentially affected populations from the different sources and pathways. This
becomes a key input to the development of cost effective management strategies.
4
IDENTIFICATION AND SELECTION OF MANAGEMENT OPTIONS
If the level of risk posed by any contaminated area is judged to a first approximation after
assessment to be potentially unacceptable, various management options can be considered
to reduce those risks to acceptable levels(9,10). A very wide range of options exists.
Dependent upon the controlling pathways for exposures, options include individually or in
combination:
i)
ii)
iii)
iv)
v)
vi)
vii)
viii)
ix)
x)
do nothing;
replace part or whole of locally-derived food sources with food imported from
uncontaminated areas;
change land uses, crops, etc, to minimise impact of contamination;
restrict access to contaminated areas;
dilute contamination by mixing with uncontaminated soil, etc;
stabilise surfaces of affected areas to minimise spread of contaminated dusts,
surface run-off, etc;
cap contaminated areas with imported clean material to minimise direct
radiation, active dust generation, etc;
immobilise contamination on-site, e.g. by cementation, vitrification, etc;
retard radionuclide migration through surface and groundwaters by use of
barriers, e.g. reed beds, sorbent-loaded vertical barriers emplaced to cut-off
groundwater flows, etc; and
physically remove contamination and dispose of in an engineered repository
either on-site or elsewhere.
Dependent primarily on the areal scale of contamination and the level of risk currently posed,
sites may be cleaned up to background levels or to a predetermined level of risk. Guidance
is available on international practice(12), waste clearance(13) and disposal(14) and the UK
regulatory framework for contaminated land(15).
By far the most common approach employed in the former case is contaminant removal by
excavation often with some form of segregation. Dependent on the availability of disposal
routes and the costs of storage and disposal for the different waste categories, the latter can
be used to minimise the volumes of higher activity waste or to concentrate the activity into a
small volume with the bulk of the soil being released as essentially free of contamination.
With very large contaminated areas full clean-up is invariably impractical and it is only cost
effective to reduce the level of risk to the exposed population. The key consideration then
becomes the level of cost which it is worth spending to achieve a given dose reduction. The
latter will vary from site to site, dependent on the economic priorities. In this case clean-up
may only be a small part of the total risk reduction approach.
It is important to be realistic in what can be achieved in risk reduction and to plan the
rehabilitation to reduce the risks in the order of their magnitude. The significance of this is
very well illustrated by the approaches adopted in the Chernobyl clean-up, where very largescale excavation operations were undertaken with little impact on the doses received by the
public, but at the expense of very significant total worker doses. In addition, these actions
continued to be taken well after the time when the exposed population had already received
the bulk of its lifetime dose due to the short-lived nature of much of the contamination. Once
it was appreciated that direct exposure was only significant in the home and not on the land
and that changes in agricultural practices and crops and the importation of certain clean
foods could very significantly reduce doses through the food chain pathway, much more
effective strategies were developed(11).
5
DECISION-AIDING TECHNIQUES
In developing management strategies for radioactively contaminated sites one of the
principal aims is to ensure that radiation doses to the public from any radionuclides present,
chemical exposures to any toxic chemicals present and physical risks are minimised.
However, this does not imply that doses, exposures, etc, to the public must be reduced to
zero - the cost of such remedial action could be prohibitive. Instead, they should be reduced
such that they are as low as reasonably achievable (ALARA), and certainly to levels at which
the probability of incurring a fatal or non-fatal cancer or serious hereditary disease due to
exposure is considered ‘acceptable’. The corollary is that if contaminated liabilities already
give rise to doses, etc, that are considered acceptable, no remedial action may be justified.
This would be the situation, if the costs and other detrimental impacts of remedial action
were not justified by the limited benefits that would arise from its implementation.
Before a programme of intervention is introduced, the ICRP principles require demonstration
that the intervention will do more good than harm, i.e. it is justifiable, and that it has been
chosen so as to optimise protection. ICRP 60 considers that justification is the process of
deciding that the disadvantages of intervention, e.g. costs, are compensated for by the
reduction in dose that would be achieved. Optimisation involves selecting the method, scale
and duration of the intervention, such that maximum benefit is achieved.
An idealised scheme for decision analysis is shown in Figure 1. In many respects it
resembles the legal process. The first stage is the gathering and initial assessment of the
options and evidence by the environmental engineers and scientists, radiological protection
advisors, etc. In this stage assessments are performed independently of any value
judgements. In the second stage the information is passed to the risk assessors and
engineers, who assess the costs, benefits, etc. Finally, a decision is made on the preferred
management strategy and the way forward.
The principal steps of the analysis are:
i)
ii)
iii)
definition of objectives and goals;
identification of assumptions;
identification and measurement of risks and costs;
iv)
v)
vi)
vii)
viii)
ix)
x)
xi)
Figure 1
identification and quantification of benefits;
specification and highlighting of uncertainties;
aggregation and comparison of risks, costs and benefits;
identification of groups at risk and recipients of benefits;
addressing of inequities in the distribution of risks, costs and benefits;
development of decision criteria, including any applicable constraints;
selection of preferred management option; and
summarising and communicating results.
The Key Stages in the Overall Decision-Making Process
In order to make meaningful comparisons between different potential management options, it
is necessary to identify and quantify the various factors(16,17) in common units, which have
typically been monetary. Thus, radiation dose values can be expressed in monetary terms
by converting them to risk estimates, i.e. annual probability of death, and using values for the
cost of a statistical life. Risks from chemical exposures, including the heavy metal effects of
certain radionuclides, such as uranium and thorium, and indeed from carrying out
conventional work can similarly be assessed, much as the insurance industry assesses
industrial injury claims. In the simplest cost-benefit analyses, intervention would be justified, if
the risk reduction, expressed in monetary terms, exceeded the cost of intervention. Cost is
not, however, the only factor of relevance and more sophisticated analysis may be
appropriate.
There are a variety of techniques available to assess whether the reduction of health
detriment that would be achieved with a particular remedial action is commensurate with the
resources required to implement the remedial action. These are outlined in ICRP 55. These
techniques are often used to choose the best option from a set of possible options or simply
to decide if remedial action is justified over the option of taking no action. They range from
the application of simple common sense, through to more complex techniques, such as costbenefit analysis and multi-attribute utility analysis.
Cost-benefit analysis is the oldest and most straightforward means for comparing the health
benefits and financial detriments of a number of possible remedial actions. Cost-benefit
analysis is characterised by the expression of all factors relevant to a decision in monetary
terms. In particular, health detriments are expressed in terms of a financial amount, either to
represent the ‘value’ of unit collective dose received, or to represent the value of a ‘statistical’
life.
Cost-benefit analysis involves evaluating the total cost of a remedial action as the sum of the
cost of the protection and the ‘value’ of the collective doses that would result after the
remedial action. The optimum option is the one for which the total cost is a minimum. The
principal disadvantage of cost-benefit analysis expressed in this form is that it only compares
remediation costs with collective doses.
Multi-attribute utility analysis (MAUA) is an important decision analysis tool that has the
particular advantage that it allows the inclusion of factors that are not easy to quantify in
monetary terms(17). In broad terms, the objective in the MAUA approach is to consider a set
of remediation options, and to calculate a ‘score’ for each option. The option with the highest
score is the preferred option in terms of degree of optimisation. Similarly, if one option is
found to have a higher score than a second option, then the first option is preferred over the
second. If the two options have equal scores, then neither is preferred over the other.
Any potential management option, including the “do-nothing” option, can be characterised by
several broad classes of performance measures. Those chosen for inclusion in the decision
analysis often include the following general categories:
a) Resource requirements, including financial, labour and materials;
b) Radiological impacts on workers and members of the public;
c) Non-radiological health impacts on workers and members of the public;
d) Effects on natural and agricultural ecosystems;
e) Effects on the amenity value of the environment; and
f) Socio-economic impacts on the local economy, including effects on employment
and transport links.
This creates a decision-making process, as summarised in Figure 2.
F in a n c ia l I m p a c ts
O b je c t o r G r o u p
o f O b je c ts
R e m e d ia tio n O p tio n s
R a d io lo g ic a l I m p a c ts
D e c is io n M a k in g
N o n - r a d io lo g ic a l
H e a lth I m p a c ts
I m p a c ts o n N a tu ra l a n d
A g r ic u ltu r a l
E n v ir o n m e n ts
R e m e d ia tio n O p tio n
R a n k in g f o r
S p e c if ie d O b je c t
o r G r o u p o f O b je c ts
S o c io - e c o n o m ic
I m p a c ts
Figure 2
The Decision-making Process
The individual categories for assessment can then be refined for fuller consideration.
1)
Initial cost, defined as the total undiscounted cost incurred in the first two years from
initiation of the remediation option;
2)
Maximum annual outlay during implementation, taken to cover years three to ten after
initiation;
3)
Long-term annual outlay, defined as the average value between ten and one hundred
years, etc, after initiation; and
4)
Total discounted outlay, defined over all time following initiation with proposed
discount rates typically between 1% and 5%.
Consideration has to be given to non-radiological health impacts on remediation workers and
members of the public. These fall into two broad classes:
i)
injury or death due to accidents; and
ii)
injury or death due to exposure to toxic materials, excluding considerations of
radiotoxicity.
5.1
Financial
1)
Initial cost, defined as the total undiscounted cost incurred in the first two years from
initiation of the remediation option;
2)
Maximum annual outlay during implementation, taken to cover the years three to ten,
etc, after initiation;
3)
Long-term annual outlay, defined as the average value between ten and one hundred
years, etc, after initiation; and
4)
Total discounted outlay, defined over all time following initiation, with a potential
discount rate of between 1% and 5.
5.2
Radiological Health Impacts
1)
Maximum annual effective dose to the representative member of the critical group of
workers at any time after initiation of remediation;
2)
Maximum annual effective dose to the representative member of the critical group of
members of the public at any time after initiation of remediation;
3)
Collective effective dose to workers integrated over all time after initiation of
remediation;
4)
Collective effective dose to members of the public, relative to the do-nothing option,
integrated over the period 0-100 years after initiation of remediation;
5)
Collective effective dose to members of the public, relative to the do-nothing option,
integrated over the period 100-1000 years after initiation of remediation; and
6)
Collective effective dose to members of the public, relative to the do-nothing option,
integrated over the period beyond 1000 years after initiation of remediation.
5.3
Non-radiological Health Impacts
1)
Expectation value of equivalent fatalities from accidents to remediation workers, with
equivalent fatalities defined as fatalities plus non-fatal injuries suitably weighted for
degree of seriousness and number of years of life impaired;
2)
Morbidity and mortality in remediation workers expressed as collective health
detriment, computed by determining the expected number of cases of each health
effect, weighting these effective numbers by severity and summing the results
obtained;
3)
Expectation value of equivalent fatalities from accidents to members of the public,
with equivalent fatalities defined as for workers. In the first instance, no distinction
need be made between accidental risks occurring at different times after initiation of
the remediation option. This position may have to be reconsidered, if it is found that
substantial distinctions in the timing of these risks arise between the various options;
and
4)
Morbidity and mortality in members of the public expressed as collective health
detriment. In the first instance, no distinction need be made between morbidity and
mortality risks occurring at different times after initiation of the remediation option.
However, this position may have to be reconsidered, if it is found that substantial
distinctions in the timing of these risks arise between the various options.
5.4
Natural and Agricultural Ecosystems
1)
A qualitative measure of the impact on natural ecosystems or a quantitative cost
measure, if this can be defined;
2)
A qualitative measure of the impact on agricultural ecosystems or a quantitative cost
measure, if this can be defined;
5.5
Socio-economic
1)
Degree of job creation, characterised by number of jobs and duration of employment;
2)
Effect on local facilities and transport infrastructure.
These factors can then be weighted in the decision-making process. The chosen weightings
will depend on national and local priorities and sensitivities. The weightings may be
numerical or broad band categorisation. One example is from the remediation of uranium
mining liabilities in the former East Germany. At the beginning of every major uranium mining
rehabilitation project, the former national uranium mining company Wismut carried out a
comprehensive EIA. Those assessments included a minimum of twelve different criteria. These
were divided into three groups depending to the judged seriousness of their impact on the
environment and on human health. They were grouped as:
High Ranking Factors
•
•
•
•
Radiation Exposure
Exposure to Environmental Pollution
Conventional Risks of Accidents
Cost Efficiency
Medium Ranking Factors
•
•
•
•
Time Requirements
Socio-ecological Requirements
Influence on Biopaths
Residual Risk
Low Ranking Factors
•
•
•
•
Impact on the local Microclimate
Impact on the Biosphere
Waste Management
Emissions during Implementation
5.6
Process Selection, Best Environmental and Practicable Environment Options
Once a decision has been made on the management strategy to be adopted, the next
consideration is the selection and development of any necessary rehabilitation processes.
There is now extensive UK(19,20) and international guidance(21-26) on available remedial
technologies and best practice for radioactively and chemically contaminated ground,
groundwater, etc. There is also guidance on monitoring after remediation to demonstrate
compliance with set clean-up criteria, etc(27). In process selection a variety of concepts are
now applied to ensure that the process is optimum, particularly in respect of minimising its
environmental impacts, and the technology employed is the best. These concepts include:
i)
ii)
iii)
iv)
Best Environmental Option (BEO);
Best Practicable Environmental Option and its UK nuclear industry variant,
Best Practicable Means (BPM);
Best Available Technology (BAT); and
Best Available Technology Not Entailing Excessive Cost (BATNEEC)
The Best Environmental Option (BEO) is the option, which in the context of releases of
contaminants from prescribed processes, provides the most benefit or least damage to the
environment as a whole, irrespective of cost, in the long term as well as the short term. The
Best Practicable Environmental Option (BPEO) is very similar except that the cost has to be
acceptable(18). Where any management option or remedial process involves releases of
substances to more than one environmental medium, there is a need to determine whether
the proposed operation represents the BPEO. In the United Kingdom the Royal Commission
on Environmental Pollution described the BPEO as the outcome of a systematic consultative
and decision-making procedure, which emphasises the protection of the environment across
land, air and water. The steps involved in identifying the BPEO are:
i)
ii)
iii)
iv)
v)
vi)
vii)
define the objectives;
generate options;
evaluate options;
summarise and present the evaluation;
select the preferred option;
review the preferred option;
implement and monitor.
To determine the BPEO for any specific site a wide range of factors need to be taken into
account. These include:
i)
ii)
iii)
iv)
v)
vi)
long-term local and remote environmental effects;
short-term environmental effects, usually local to the site;
global atmospheric effects;
disposal or recycling of liquid and solid wastes;
process practicability and efficiency; and
costs of process or abatement options.
The integrated assessment of these factors is complex. Given their different characteristics,
reliance is needed on professional judgement to identify the BPEO. To ensure that the
decision-making process is carried out in a transparent and consistent manner, the
Environment Agency developed an assessment framework(18). Part of this framework
involved deriving an Integrated Environmental Index (IEI) to enable different process options
to be ranked according to their relative long-term environmental effects.
The concept also exists of Best Practicable Means (BPM). Within a particular management
option, BPM is that level of management, engineering control, etc, that minimises as far as
practicable, the radiological impact of the option, whilst taking account of a wide range of
factors, including cost-effectiveness, technological status, operational safety, and social and
environmental factors. In determining whether any option represents BPM, the UK
regulators do not require expenditure of resources, e.g. cost, time, etc, which is
disproportionate to the likely benefits.
“Best” may be taken to be the most effective option in preventing the release of radioactive
material, etc, from a process, and/or minimising or rendering less harmful those that cannot
be prevented. There can be more than one process, technique, means, etc, of achieving the
same degree of effectiveness. The “best” option is the one, which properly takes account of
the overall benefits and detriments (cost) to society. Practicable implies that the option
should be technically possible and could be used without costs or other detriments being
incurred that are unreasonable compared to the benefits gained. “Means” is the way in
which any task is carried out or an objective fulfilled. It includes the provision, maintenance
and operation of any plant, equipment or process and the supervision of any operation
involving solid, liquid or gaseous radioactive waste.
6
REMEDIATION CRITERIA
In the past the remediation or clean-up criteria were often based on dose rate, e.g. 0.3 μSv/h
compared to a typical background level, e.g. 0.15-0.2 μSv/h, definitions of radioactive
materials and limits for the exemption of materials from radioactive controls and some
qualitative consideration of the risks arising from the remaining wastes(28). However, most
current criteria are generally directly or indirectly health risk-based and normally derive from
the recommendations of the ICRP(12). The choice of limit or indeed the applicability of a limit
are influenced by whether current exposures are controlled and hence the risk reduction
works are classified as in support of a “practice” or an “intervention”, as defined under
ICRP 60. For areas affected by accidents, such as Chernobyl, intervention criteria apply,
whereas for former controlled nuclear sites practice criteria are likely to be more appropriate
with their maximum dose limits and dose constraints.
In some cases the criteria are interpreted in terms of an acceptable annual dose limit. This
approach was nominally adopted for Chernobyl, where the Ukrainian Parliament decreed
that the population in the contaminated areas should not be exposed to additional annual
doses in excess of 1 mSv above the local background, which is of the same order. It was
also adopted at Maralinga where the annual dose limit for the critical group, which was
assessed as Aboriginal children living their semi-traditional lifestyle, was set at 5 mSv. For
other sites, such as in the original clean-up of the Southern Storage Area at Harwell, the
clean-up levels for various radionuclides were set at fractions of the individual Generalised
Derived Limits (GDLs)(29) and by comparison with the surrounding backgrounds at similar
nuclear industrial sites. In its final clean-up, risk-based clean-up levels and targets were
used(22).
In each of these cases likely current and post remediation doses can be related to
contamination levels through a quantitative risk assessment using an analysis of potential
exposure pathways. Indeed, GDLs and current proposed exemption limits are now derived
on the same basis, differing only in the degree of conservatism built into the analysis and the
underlying assumptions.
7
MANAGEMENT APPROACHES IN PRACTICE – CASE STUDIES
7.1 The Southern Storage Area at Harwell
The Southern Storage Area (SSA) is a separate, security-fenced site, which is owned and
maintained by the United Kingdom Atomic Energy Authority (UKAEA) and is located
approximately 1 km south of the main Harwell nuclear licensed site. It is 7.3 hectares in
area. The grounds of Chilton County Primary School adjoin the south-eastern boundary of
the SSA. The remainder of the site is currently surrounded by farming land and a bridleway.
Soon it is to be the centre of a new housing development of 265 homes. Unit house prices
and land values in the region are high, potentially justifying substantial expenditure in
reducing residual risks. Members of the public use the paths and bridleways around the site
and also the open land to the north of the site. The land to the north and west of the site is
owned by UKAEA with some leased for agricultural use. The land to the south is privately
owned.
The site was the main munitions' storage area for RAF Harwell, which was a Second World
War bomber and training aerodrome. It was subsequently used for waste storage, treatment
and disposal operations by UKAEA. A preliminary clean-up of the site was carried out during
1988-90. This was undertaken in order to eliminate the need for the site to be licensed under
the Nuclear Installations Act, as was required for the main Harwell site. It was not sufficient
to allow unrestricted access to the site.
As a result of the historical operations on the site there were three main liabilities. These
were addressed in the remediation programme. They were the ‘Chemical’ Pits, the
‘Beryllium’ Pits and the ‘Common’ Land, which was the remainder of the site. There was
known to be contamination due to radioactivity and chemicals stored within the various pits.
This contamination, coupled with the physical state of the site, i.e. steep banks and surface
scrap, meant that the site was unsuitable for unrestricted public access. An outline planning
consent was granted for housing on Chilton Field, which is close to the SSA. It is a condition
of the planning consent, that the SSA should be remediated to a standard suitable for
unrestricted public access.
The objectives of the remedial works were:
ƒ
To design, plan, implement, validate and report a land remediation of the Southern
Storage Area. The remediation was to the specified clean-up standard, which met
the requirements of a Section 106 agreement of the planning application for
housing development on the neighbouring Chilton Field site. Fulfilment of these
requirements would enable UKAEA to sell that land;
ƒ
The work was to be designed, planned and implemented in accordance with UK
health & safety and environmental statutes, codes of practice, official guidance,
best practice and UKAEA’s safety requirements; and
ƒ
The remediation was to be such that upon completion the land would be suitable
for unrestricted public access.
The scope of the work was:
ƒ
Remediation of the “Chemical” Pits by excavation and removal of their contents and
affected immediately surrounding areas until no contamination remained above
specified, acceptable risk-based limits;
ƒ
Remediation of the “Beryllium” Pits also by excavation and removal of their
contents and affected immediately surrounding areas until there remained no
contamination above similarly specified, acceptable risk-based limits;
ƒ
Remediation of the “Common Land” (all general areas of the site) by systematic
land turning until no contamination remained above the specified, acceptable riskbased limits nor munitions, hazardous or unsuitable materials; and
ƒ
Landscaping of the site, including re-contouring and re-seeding with grass followed
by maintenance for a ‘settling-in’ period.
In order to achieve the objective of remediating the site to the level, where the residual risks
were sufficiently low to permit unrestricted public access, a suitable clean-up standard was
specified. This was primarily expressed as a risk target. The target was that the probability
of serious harm or death to the most exposed individual involved with the site should not
exceed 10-6 per annum. This clean-up standard was then expressed using Risk-Based
Clean-up Levels (RBCLs). These were modified to account for best practice, background
levels and analytical limits of detection, etc. The result was a set of remediation targets. The
remediation approach was to remove all contamination to below these remediation target
levels, except where it was impractical or excessively costly to do so. In cases, where
residual contamination was left, a further risk assessment was undertaken using more
detailed, site-specific data. In every case they confirmed that the residual risks were
acceptably low and below the agreed risk target.
The use of RBCLs accords with the latest guidance provided by the Department of
Environment, Food and Rural Affairs (DEFRA) and the Environment Agency (EA). These
RBCLs were detailed by UKAEA’s environmental consultants, Dames and Moore and the
National Radiological Protection Board (NRPB), in their Environmental Assessment. They
were derived using conservative data assumptions and pathway models identical or
comparable with those proposed by DEFRA and the EA. They were based upon ensuring
compliance with the risk target. The RBCLs for chemicals were absolute values. Those
quoted for radiochemicals were above background. They were modified as required to also
ensure compliance with the Radioactive Substances Act of 1993 (RSA 93). As part of the
remediation programme soil samples from around and on the site were analysed to
determine the background concentrations.
The achievement of remediation targets was regarded as a minimum end point. The
physical condition of the end point was specified in terms of an outline land profile and
landscaping. It was fully sufficient to ensure that physical risks from trips, falls, etc, were
minimised by appropriate choice of slopes, soil compaction, surface finish, etc, and that all
physically hazardous materials, such as any hard, sharp objects, were removed from any
possible human contact.
The basic methodology used for the remediation works is summarised below.
Stage 1. This involved the development of a detailed “Remediation” Plan for the works. This
was the key safety document for the control of the works. It covered all aspects of the works,
i.e. hazard identification and risk assessment; detailed design of the remediation; safety
management system; method statements and working instructions; waste management
system; emergency procedures; quality assurance; commissioning. It was a live document
in which changes were incorporated during the works, where necessary, in order to complete
the remediation efficiently and safely when circumstances on site were not precisely as
predicted. All changes were controlled by a formal modification procedure.
Stage 2. This stage was prior to the issue of an Authority to Operate (ATO). It involved the
clearance of the site of vegetation including trees and undertaking the surveys of the
background conditions offsite and the baseline conditions onsite.
It also involved
geophysical surveys and munitions detection trials in selected areas of the site.
Stage 3. This extended from the issue of an ATO to proceed through the commissioning of
all of the site facilities, including safety-related equipment. During this stage the site
infrastructure was installed, including the site offices, security systems, environmental
monitoring, etc, the Waste Assay Facility and the weather protection buildings and ventilated
containments over Beryllium Pits A-B-E and Chemical Pit 5.
Stage 4. This involved the remediation of Beryllium Pit A-B-E, the complete remediation of
Chemical Pit 5, construction of the weather protection building and ventilated containment
over Beryllium Pit C and remediation of the bulk of the southern portion of the Common
Land. The latter, as with all Common Land clearance, involved removal of any munitions,
waste, hazardous or unsuitable materials, and of chemical and radioactive contaminants
above the specified remediation targets. At the end of this stage the weather protection
building and ventilated containment over Chemical Pit 5 were removed and the operating
team moved to commence operations in Beryllium Pit C. During this stage a number of
remediation areas were worked in parallel. In particular, one team remediated Beryllium Pit
A-B-E throughout this period, whilst another team worked first on Chemical Pit 5 and upon its
removal transferred to Beryllium Pit C.
Stage 5. In this stage remediation of Beryllium Pits A-B-E continued, as did work on
Beryllium Pit C. Upon completion of the latter the weather protection building and ventilated
containments were constructed over Beryllium Pit D and those over Pit C were
decommissioned and removed. The operating team from Beryllium Pit C then transferred to
Pit D and following commissioning of that facility commenced remedial work there. In
parallel remedial work progressed on the Common Land over much of the northern half of
the site.
Stage 6. During this period the remediation of Beryllium Pits A-B-E and D was completed
along with the western area of the Common Land. Pits A-B-E were completed first. Their
operating team switched to remediate Chemical Pits 1-4 and 6. The weather protection and
ventilated containments for these had been constructed and commissioned previously. The
Common Land was then contoured to close to its final form. The bulk of the site
infrastructure was removed bar the Waste Assay Facility with its hygiene, laboratory and
sufficient office facilities to complete the work. The final part of the Common Land
remediation was carried out with the land first under the original office complex, then under
the remaining roads and hardstanding areas. The final validation surveys were undertaken.
The Waste Assay Facility was decommissioned and removed. Finally its concrete slab base
was removed.
Stage 7. At this stage the final contouring was completed and the site was covered with
clean topsoil. It was then grassed and other vegetation required by UKAEA, e.g. trees and
shrubs, were planted. The site was then being maintained for a further year to allow the
vegetation to become established. At this stage the project was finally completed.
The waste segregation strategy was a key component of the programme to ensure that all
waste was properly categorised and safely consigned to the appropriate disposal facility. It
was based on the following key steps:
ƒ
ƒ
Use of previous characterisation results plus in-situ and excavation bucket
monitoring for radioactive and chemical contamination by gamma, beta surface,
VOC and Hg probes to provide initial work face segregation into
exempt/Special/controlled and low-level waste streams;
ƒ
Packaging of the bulk of pit wastes bar large artefacts, etc, and some Common
Land wastes into 1 m3 cube bags, which became the de facto sentencing volume;
ƒ
Sampling of the wastes during the filling of the 1 m3 bags and other waste
containers;
ƒ
Gamma and contamination monitoring of the faces of each bag. The former
confirmed the absence of any significant gamma sources in each bag;
ƒ
Gross αβ analysis of the homogenised sample from each bag to determine whether
below the SoLA exemption limit or above the low-level waste limits. All waste
between these limits were treated as potentially exempt waste;
ƒ
High-resolution gamma spectroscopy of every bag of the potentially exempt waste
to determine the levels of the Schedule 1 elements, 40K and gamma-emitting
anthropogenics;
ƒ
Application of the SoLA exemption limit, if any anthropogenics were determined
above their background levels, with the waste sentenced as low-level, if the limit
was exceeded; and
If no anthropogenics were present at above background levels, then the activity levels of
the naturally occurring elements were compared with their Schedule 1 limits, where
applicable. If they were below those limits, the waste was classified as Special or
Controlled waste. If not, their levels were compared with those of the Phosphatic
Substances Exemption Order. Dependent upon whether the exemption order limits were
exceeded, the waste was sentenced as low-level or Exempt.
Throughout the remedial works a validation process was undertaken to confirm successful
compliance with the remediation objectives. It involved continuous sampling and monitoring
and culminated in a final validation survey. It was designed and met four objectives:
ƒ
Demonstration that the Common Land soil re-used on the site met the remediation
targets. This was achieved by ‘routine’ sampling and monitoring of the Common Land
soil during its turning over. Routine samples also identified areas that did not meet the
remediation targets and therefore needed to be removed as waste;
ƒ
Demonstration that the soil at the final excavated surface of the Common Land and in
the pits before backfilling met the remediation targets. This was achieved by
‘verification’ monitoring and analysis;
ƒ
Demonstration that the soil at the final surface before topsoiling of the site met the
remediation targets. This was achieved by ‘validation’ monitoring and analysis; and
ƒ
Demonstration that where, exceptionally, a volume of soil containing materials in
concentrations greater than any remediation target was left on the site for one of the
reasons listed above, the risk target was still achieved. This was demonstrated by
refining the risk analysis reported in the Environmental Assessment by using actual
monitoring and other site-specific information.
In addition the re-used and imported topsoil was also tested to ensure that it met the
remediation targets.
There were finally only 81 results out of a population of more than 13000 measurements,
where RBCLs were not met for reasons other than an LOD or natural background levels.
Thus > 99.4% of the measurements were directly compliant. For the remainder a revised
risk estimate was derived using the refined site-specific risk assessment methodology.
The risks arising from the residual levels of these chemicals were compared with the
acceptable risk target for unrestricted public use of 10-6 per annum. The risks were
calculated using the original risk assessment parameters detailed in the Environmental
Assessment and the observed monitoring data from the background, baseline, routine,
verification and validation sampling regimes. They demonstrated that in every area the risks
from residual levels of contaminants were smaller than the specified acceptable risk target.
To ensure the well-being of the workforce, public and environment, environmental monitoring
was undertaken throughout the works. Emissions recorded daily and monthly were within
project limits. These were set in accordance with HSE guidance. For the exposed workers
they were the long-term occupational exposure limits (OEL) or 50% of the maximum
exposure limits (MEL). For the public they were 1% of these limits. All of the field workforce
was classified as radiation workers. The maximum annual dose received by any worker was
0.52 mSv with the average being only 0.06 mSv. The total collective dose received over the
works’ duration was 5.67 man-mSv.
These are all much below accepted limits.
Environmental monitoring was also carried out before, throughout and after the works to
ensure that there was an acceptable working environment and that exposures of the
workforce and public were within UKAEA and publicly acceptable limits. This monitoring
included:
ƒ
Contamination and radiation surveys (Routine & Operational);
ƒ
Static air sampling (SAS) for radioactivity, beryllium, dust and metals;
ƒ
On-line monitoring for radioactivity, VOCs, and mercury vapour. The pits were treated as
confined spaces. The monitoring also included for flammable gases, CO, O2 and
benzene and associated compounds;
ƒ
Stack discharge monitoring for radioactivity, beryllium, metals and dust.
ƒ
Noise surveys
No unexpected radiation or contamination was found on routine surveys. The only radiation
and contamination detected during the project were from remediation operations, i.e.
operational surveys.
Particulate-in-air samplers were operated around the site and within containments. In the
latter they were operated close to the excavation face and waste handling area. On the
Common Land they were operated downwind of excavator operations. Other samplers were
operated in hygiene units, the Waste Assay Facility and whenever special operations were
carried out. In total over 7300 samples were taken and more than 102,000 measurements
made. The daily and monthly results demonstrated conclusively that the emissions from the
site were within the project limits and were much below HSE guidance exposure criteria.
A discharge authorisation was granted by the EA for the stack emissions from all of the
ventilated containments. Continuous samplers were operated in the stacks. The results
confirmed that at no time was this authorisation exceeded and that all emissions were very
low and at only a very small fraction of the authorisation.
Thus it was concluded that the remedial works did fully achieve all of the remediation
objectives with no significant impact on the public or local environment.
7.2 The Rehabilitation of the Former Nuclear Weapons Test Site at Maralinga
The second example relates to the current rehabilitation of the Maralinga test site. This site
occupies some 3,200 km2, although the areas with significant contamination are much
smaller and total of the order of a few hundred square kilometres. Maralinga is located on
the northern edge of the Nullarbor Plain in South Australia approximately 900 km north west
of the city of Adelaide. A view of the site with the major areas of contamination is shown in
Figure 2(1).
Between 1953 and 1963 the British Government carried out seven atmospheric nuclear
weapons tests and approximately five hundred and fifty small scale experiments (“minor
trials”) using nuclear materials at the site. These latter trials resulted in the dispersal of over
23 kg of plutonium, 22 kg of enriched uranium, 8,447 kg of natural and depleted uranium and
102 kg of beryllium, as well as smaller amounts of other materials at various locations over
the range. During the operation of the test site various “housekeeping” radiation surveys and
clean-up operations were undertaken. Some of the materials used in the trials were
gathered up and buried in various numbered and unnumbered pits throughout the range.
A final clean-up was undertaken in 1967 by the British Army in an operation code-named
Brumby. The aims of this operation were to reduce the levels of contamination and to
perform such other operations as were considered necessary to close the site to the
satisfaction of the British and Australian Governments. The underlying assumption behind
the clean-up was that the site would be used in future for cattle or sheep grazing with no
significant human inhabitation. The clean-up involved the burial of the most highly
contaminated materials at Taranaki in twenty-one shallow pits, which were then capped with
reinforced concrete. Much debris, including various target response items, was buried in the
crater at Marcoo, which had resulted from a 1.5 kton ground burst in 1956. This crater was
then covered with soil. Various areas were ploughed with either a disc harrow or a tractordrawn, closed bowl scraper to dilute the surface activity levels by mixing with the clean lower
soil. In some cases, particularly in central Taranaki, where the levels of contamination still
remained unacceptably high, clean soil was imported to dilute the levels further.
In 1977 a survey was undertaken by the Australian Radiation Laboratory, ARL, and the
Australian Atomic Energy Commission (AAEC) covering both the major and minor trials sites.
This survey was extended in 1984-5. In 1984 an Australian Government Commission into
the British Nuclear Tests in Australia concluded that the treatment of the Pu-contaminated
areas had been inadequate, was based on the wrong assumptions, and had left the range in
a more difficult state for any future proper clean-up. It stated that Pu-contaminated areas
must be cleaned up. The Australian Government set up a technical advisory group (TAG)
and a consultative group to evaluate and recommend an appropriate clean-up strategy. As
part of their work a helicopter-based, aerial survey was undertaken by EG&G of all of the
significant sites[7]. This survey mapped the distributions of the significant γ emitters: 241Am,
60
Co and 137Cs. The preferred strategy was option 6(c) in the TAG final report[7]. This option
was implemented by a consortium led by Australian Construction Services with site
remediation and health physics support from AEA Technology[34].
This rehabilitation programme was specified as a risk reduction exercise not as a clean-up.
The underlying assumption behind it was that the site would be returned to its former
Aboriginal owners, the Maralinga Tjarutja. They will resume living their semi-traditional
lifestyle, albeit supplemented by certain modern accompaniments, such as imported
foodstuffs, motor vehicles and health care. This semi-traditional lifestyle involves the
potential intake of much greater levels of dust than would be characteristic of western
society. Hence the inhalation of Pu-contaminated dust was identified as the dominant
pathway for dose accumulation[33]. The critical group was identified by TAG as Aboriginal
children and the rehabilitation strategy was devised to ensure that their annual dose did not
exceed 5 mSv. This dose limit was translated by the Australian Radiation Laboratory into
acceptable residual contamination levels for various parts of the site. These levels ranged
from 1.8 to 4 kBq(241Am)/m2 with 241Am being used as a marker for the Pu present.
The key components of the risk reduction works were:
i) construction of three large, 15 m deep, burial trenches at Taranaki, TM100/101 and
Wewak;
ii) removal of contaminated soil to an average depth of 150 mm from approximately
2.2 km2 at Taranaki, TM100/101 and Wewak and its placement into the
corresponding disposal trenches;
iii) removal of the concrete caps from the twenty one numbered pits in central
Taranaki, followed by in-situ vitrification of their contents using the Geosafe process
and replacement of the concrete caps and restoration of the surfaces to their natural
levels;
iv) exhumation of various other pits containing Pu-contaminated debris and
placement of the contents in the burial trenches. These included some contaminated
firing pads;
v) restoration of various other numbered and unnumbered pits by collection and burial
of surface debris, compaction, importation of clean soil, recontouring and
revegetation;
vi) installation of 100 km of marker posts at 50 m intervals throughout the outer plume
areas to warn the Aboriginal population that they may hunt and traverse the area, but
should not camp there permanently;
vii) removal of access routes to certain areas by ripping up roads and revegetating;
and
viii) revegetation of selected areas.
The bulk of the soil was removed using scrapers, supported by excavators and front-end
loaders to remove small areas requiring further treatment. In some areas the soil cover was
very limited and vacuum and rotary brush attachments were used to clean rock surfaces.
The major hazard to the operators and for recontamination during the rehabilitation process
arose from the generation of Pu-bearing dusts. A variety of measures were undertaken to
minimise such dust generation. These included modifying plant to reduce their dustgenerating characteristics, e.g. by covering loads; restricting plant operating spreads and
prewetting areas, etc., to suppress dust formation.
To minimise risks to operators, wherever possible operations were devised to avoid the need
for personnel to be on the ground during any operations involving the removal of active
materials. All plants to be used in such operations were modified to have positively
pressurised, sealed cabins with absolute filtered air supplies.
Soil removal was undertaken in lots. These lots were monitored each day following
cessation of soil removal operations. Any areas not meeting the clearance criteria were
reworked. All treated areas were independently surveyed by the national regulator,
ARPANSA, using a specially modified OKA vehicle with a boom mounted, high purity
germanium detector, to certify that all clearance criteria have been met. Finally, areas were
revegetated to return the site to a condition close to its original state.
7.3 Contaminated Areas outside the 30 km Exclusion Zone around the Chernobyl
Nuclear Reactor Site
The third example considers the contaminated areas outside of the 30 km exclusion zone at
Chernobyl. This is located in an agriculturally rich and valuable area of Ukraine, Belarus and
Russia with significant local population.
In this case the total affected area with
contamination levels greater than 37 kBq/m2 (1 Ci/km2) is on the scale of tens of thousands
of square kilometres. AEA Technology was involved in developing risk (dose) reduction
strategies for these areas for several years. This work started in 1991-92 with a study
undertaken for the Ukrainian Government with funding from the UK “Know-How” Fund[11]. It
continued with projects undertaken for Russia, Belarus and Ukraine under European
Commission funding. The scale of this problem was such that risk reduction by large scale
removal or direct isolation of the contamination was neither technically or economically
feasible within a time scale of tens of years. Hence, alternative approaches to reducing the
risks from the contamination were necessary.
This project involved categorisation of the different types of contaminated areas in the
affected countries, identification of the key exposure pathways, identifying potential
countermeasures for each category of area, including for agriculture and forestry, calculation
of the benefits to be derived from the application of these countermeasure and estimation of
their application costs.
The contaminated region was subdivided according to the contamination density to reflect
external exposures, internal doses received and closeness to forests. The significance of the
latter related to forest-grown mushrooms being the second most important contributor to
internal dose after 137Cs in milk and mushrooms. Hence, the study concentrated on rural
areas, where, due to the consumption of locally produced contaminated foodstuff (especially
privately produced milk), the internal dose is higher than in towns. Local capitals and towns
with more than 8000 inhabitants were not included.
Very detailed data were acquired for 40 selected settlements, covering the key categories of
interest. The data included information about the population, 137Cs activity per area, soil
composition, aggregated transfer factors for milk, pork, beef, potatoes, grain, mushroom
contamination, internal and external doses, as well as countermeasures, which had already
been applied. The main contributions to the ingestion dose for settlements close to forests
come from milk (43 %) and mushrooms (37 %) and from milk (68 %), pork (15 %) and
potatoes (13 %) for settlements far from forests. This information helped define the range of
parameters to be used in calculating the impact of countermeasures on the larger scale.
7.3.1
Effectiveness and costs of agricultural countermeasures
The agricultural countermeasures reviewed included land remediation and the use of
Prussian blue to attenuate gut absorption of 137Cs by cattle. They did not include the effects
of food-processing or culinary preparation. The range and a ‘best’ estimate of reduction
factor, which could be achieved with each countermeasure, were estimated. The fractional
reduction in internal dose achievable through the provision of cleaner milk was evaluated,
giving the fractional contribution to dose from exposure to 137Cs for four soil types and for
three different levels of consumption of milk. The ease of implementation and the practicality
of the application were also considered.
The countermeasures considered were:
•
•
•
•
•
•
•
•
•
•
•
•
Liming of acid soils
Adding fertiliser and/or lime
Ploughing and re-seeding (no fertiliser)
Ploughing, fertilising, liming and re-seeding (radical or surface improvement)
Skimming-and-burial, ploughing and re-seeding
Removal of turf, fertilising and re-seeding
Drainage of waterlogged soils
Drainage of waterlogged soils, ploughing, fertilising and re-seeding
Application of manure
Inclusion of Prussian blue in fodder
Use of Prussian blue in salt-licks
Use of Prussian blue gut boli
The most effective and practical means of long term reduction of 137Cs in milk was identified
as applying surface or radical improvement, i.e. ploughing, fertilising, liming and reseeding.
The difference between these two techniques is in the depth to which the soil is ploughed
which, in turn, depends on the thickness of the soil layer. This procedure was extensively
applied in Russia with good results. As it is essentially a variant of normal land management
practice, it also improved the productivity of the pasture and did not require substantial
amounts of new equipment. It resulted in the improvement of pasture for 2 to 3 years after
application. However, its effectiveness decreases with further applications.
Procedures, which involve turf removal or burial, are very effective. However, they were
impractical, since they generate large volumes of very low-level radioactive waste material,
which requires management. They also reduce soil fertility and are not applicable to all
terrains. Similarly, drainage of soils was not appropriate on the large scale, although it could
be very effective on specified sites.
To aid decision makers a methodology was developed for determining the doses, which
might be averted as a result of the application of the identified agricultural countermeasures.
It is constructed in a way to enable changes in parameters and assumptions to be made and
the consequences calculated. Typical results are:
Radical improvement
Location
to forests
Country
Belarus
Russia
Ukraine
Belarus
Russia
Ukraine
close
close
close
far
far
far
Surface improvement
Location
to forests
Country
Belarus
Russia
Ukraine
Belarus
Russia
Ukraine
close
close
close
far
far
far
Fraction of total dose averted
(ranges)
1st application
subsequent
application
2.6 % - 26 %
1.6 % - 16 %
6.7 % - 24 %
4 % - 15 %
14 % - 26 %
9 % - 16 %
4 % - 41 %
2.5 % - 25 %
10 % - 38 %
6 % - 23 %
30 % - 41 %
18 % - 25 %
Cost of averted dose
(range)
[$/manSv]
Fraction of total dose averted
(ranges)
1st application
subsequent
application
1.3 % - 13 %
0.9 % - 9 %
3 % - 12 %
2%-8%
7 % - 13 %
5%-9%
2 % - 21 %
1.5 % - 14 %
5 % - 19 %
3.5 % - 13 %
15 % - 21 %
10 % - 14 %
Cost of averted dose
(range)
[$/manSv]
4,500- 56,000
3,400- 45,000
not available
700 - 34,000
2,200- 34,000
not available
6,700- 78,000
5,600 - 67,000
not available
1,000 - 45,000
3,400 - 41,000
not available
To put these results into context the value of the averted manSv suggested in ICRP 37 is of
the order of $10,000 to $20,000. If the countermeasures remain effective for several years
after application, then the cost per averted manSv given above can be divided by the number
of years over which the countermeasure is effective.
7.3.2
Use of Clean Milk Supplies
An alternative strategy for reducing internal exposures from 137Cs in milk was to provide a
clean milk supply to the affected population. The averted doses achieved and the associated
costs were evaluated and are shown in the table below. This was an effective strategy for
reducing the internal dose, particularly in the far from forest settlements where milk
contributes about 67% of the internal dose. However the associated cost per manSv averted
was generally higher than with the previous remediation strategies considered. In addition,
no permanent decrease in pasture contamination results. Hence, the local farmers would
lose their economic benefit from producing and selling milk.
Provision of clean milk supply
Location Fraction of
Total averted dose
where
all
to forests total averted
categories internal dose
dose
>1mSv/y
[manSv]
(range)
Country
[manSv]
[%]
Belarus close
4 - 39
67
29
Russia
close
10 - 36
19
10
Ukraine close
21 - 39
153
101
Belarus
far
6 - 62
62
21
Russia
far
15 - 56
6
3
Ukraine
far
45 - 62
98
61
7.3.3
Total cost
where internal
all
dose >1mSv/y
categories
[M$/manSv]
[M$/manSv]
16
21
5.7
10.2
6.5
2.5
2.1
1.6
1.6
1.3
0.3
0.66
Resettlement
Resettlement was a potential interim strategy, either whilst remedial works were undertaken
or in cases where there is a significant short-lived component of the contamination.
Calculations of potential external dose reductions due to the resettlement of people from the
higher to the lower contamination density areas indicated that up to 62 % of the total dose
could be averted. These assumed that the internal dose distribution remained unchanged by
resettlement. This was a very significant reduction. However, it was unlikely to be an
acceptable solution at present for both social and economic reasons.
Based on the data for the 40 settlements, individual remediation strategies were derived for
these settlements taking into consideration the individual radiological situation. The model
used was modified, so that frequency distributions of the corresponding quantities and their
means were input. These distributions took into account individual dietary habits of the
population as well as the variety of the transfer factors within a settlement due to
environmental inhomogeneity and other influences. With this stochastic approach, critical
groups could also be taken into account. The result was a dose distribution among the
population for a specific settlement.
In order to work out the individual countermeasure lists for each of the settlements the most
important pathway was determined and the corresponding most effective countermeasure
applied. This method was successively repeated until one of the break-off conditions was
fulfilled. The conditions used were: the total dose did not exceed 1 mSv/a and the ingestion
dose did not exceed 0.25 mSv/a.
Agricultural countermeasures were considered, if total annual doses of 10% (critical group) of
the population of a settlement exceeded 1 mSv and if the annual internal dose exceeded
0.25 mSv. Otherwise the dose could only be significantly decreased by countermeasures
against external exposures. The countermeasures, considered in this approach, were the
restriction of mushroom consumption, application of caesium binders (Prussian blue), radical
improvement of meadows and pastures, the support of settlements with clean milk, clean
feeding of pigs two months before slaughter and mineral fertilising of potatoes.
The calculated costs per averted dose ranged from about 10 Euro/mSv to 150 Euro/mSv.
Due to the individual fitting they were about one order of magnitude lower than the cost of the
remediation strategies worked out by the large-scale approach.
7.3.4
Forest Countermeasures
Significant parts of the contaminated areas are covered by natural and cultivated forests. As
a result the prime forest resources of wood and forest food products are contaminated,
particularly by 137Cs. Radiation exposure occurs during the harvesting of trees, use the
forest products for construction and paper production, and consumption of food harvested
from forests and gardens fertilised with contaminated wood ash. Forest workers, who
represent about 5 % of the local population, are the critical group. They receive radiation
doses 2 to 3 times higher (< 5 mSv/y) than other local groups.
Three active countermeasures were evaluated in detail:
• Incineration of contaminated wood waste for energy recovery
• Using tree felling machines
• Mitigating the consequences of mushroom contamination by growing mushrooms on
clean substrate and/or supplying monitoring devices.
Incineration of contaminated wood is very expensive, particularly if the only cost considered
is averted man Sv. It has an investment cost ~$340/kW installed. However, it has benefit in
helping the recovery of forestry industries, which have been adversely affected by the
economic burden of the lost production. It also represents an alternative source of energy
production. As such it was more likely to be applied, where there is an important national
energy deficit as in Belarus.
The use of greater mechanisation, such as tree felling machines, was considered, as it could
decrease the dose to forestry workers, who presently use little mechanised equipment. The
cost was assessed at $3.8M/man Sv from which salary savings~ $9k/year should be
subtracted due to improved productivity.
7.3.5
Mitigation of the consequences of mushroom contamination
Contamination of mushrooms results in loss of forest production and radiological exposure of
mushroom eaters. Two options for mitigating its consequences were considered. Firstly, the
extra production of saprophyte mushrooms on clean substrates is expected to provide a
benefit in terms of both dose reduction and compensation for the lost forest production. The
successful application of this option, however, presupposes that people would be able to
change their dietary habits. Based on the available economical data and on CIS labour cost,
this option would lead to a cost of $2 to 3 k per man Sv. The second option was to monitor
mushrooms for contamination and only select those with acceptable levels. A simple robust
measuring device was developed in France for the non-specialist. If applied, the cost would
be $3.1 k per man Sv.
8.
CONCLUSIONS
These three examples demonstrate clearly the impact of scale, location, economic value of
land, population density and lifestyle, etc, in influencing the selection of remediation
strategies. Techniques, which remove contamination directly or in association with soil,
scale effectively linearly in cost of application with the area treated or volume of soil
removed. The volume of waste requiring disposal elsewhere scales similarly. For limited
areas of a few hectares and possibly up to a few km2, such techniques can be used to
reduce residual contamination levels to very low values within a manageable financial and
social cost, even though the cost per man Sv saved may be high. Such approaches can
effectively reduce residual risks to very low values in a very short time period. However, as
the affected area increases, the practicability of this approach decreases and the total
financial and social costs become steadily more unacceptable, requiring a change of
approach to one of seeking to manage the risks to as low a level as economically practical
on a long-term basis.
9.
REFERENCES
[1]
JARDINE, F. M., THOMAS, A. F., CHURCHER, D. W., HILL, M. D. and STANBURY,
J. Management of contaminated Land on nuclear Sites: establishing and delivering best
practice Guidance. Containment 2000 Nuclear Materials Containment and Disposal. Int.
Conf. I. Nuc. E., 9-11 May 2000.
[2]
BAKER, A. C., DARWIN, C. J., JEFFERIES, N. L., TOWLER, P. A. and WADE, D. L.
Best Practice Guidance for Site Characterisation. Managing contaminated Land on nuclearlicensed and defence Sites. First Edition. CIRIA, October 2000.
[3]
IAEA. Site Characterization Techniques used in environmental Restoration Activities.
IAEA-TECDOC-1148, IAEA, Vienna, Austria, May 2000.
[4]
IAEA. Characterization of radioactively contaminated Sites for Remediation
Purposes. IAEA-TECDOC-1017, IAEA, Vienna, Austria, May 1998.
[5]
BRITISH STANDARDS INSTITUTE. Investigation of potentially contaminated SitesCode of Practice. BS 10175:2001. British Standard.
[6]
BRITISH STANDARDS INSTITUTE. Code of Practice for Site Investigations. BS
5930:1999. British Standard.
[7]
TECHNICAL ASSESSMENT GROUP. Rehabilitation of Former Nuclear Test Sites in
Australia. Department of Primary Industries and Energy, Commonwealth of Australia,
Australian Government Publishing Service, 1990.
[8]
SMITH, G. Assessment of Health and Environmental Risks of Management Options
for Contaminated Land. CIRI-6349A, September 2002. CIRIA.
[9]
HILL, M., PENFOLD, J., HARRIS, M., BROMHEAD, J., COLLIER, D., MALLET and
SMITH, G. Good Practice Guidance for the Management of contaminated Land on nuclear
and defence Sites. CIRI-6394A, CIRIA, SAFEGROUNDS, September 2002.
[10]
USEPA. Approaches for the Remediation of Federal Facility Sites contaminated with
explosive or radioactive Wastes. EPA/625/R-93/013, September 1993.
[11]
HOLDROYD, S.D., EGGLETON, A.E.J. and FELLINGHAM, L.R. Chernobyl clean-up
strategy: Post Chernobyl remediation in Ukraine. Second Intl. Symp. on Environmental
Contamination in Central and Eastern Europe. Sept 20-23, 1994. Budapest, Hungary. pp.
500-502.
[12]
EDDOWES, M. and PAGE, N. A Review of International Risk Criteria and related
Environmental Cleanup Standards. AEA Technology, October 1999.
[13]
HILL, M. D. Clearance Levels and generic authorised Levels for Wastes containing
naturally-occurring Radionuclides. Proc. Int. Conf. On natural Radiation and NORM. 30
September – 1 October 1999. IBC Global Conferences Ltd.
[14]
NATIONAL RADIOLOGICAL PROTECTION BOARD. Statement on Radiological
Protection Objectives for the Land-based Disposal of Solid Radioactive Wastes. 1992.
[15]
HILL, M. D. The regulatory Framework for contaminated Land on nuclear-licensed
Sites and defence Sites. Version 2. CIRIA, November 2000.
[16]
IAEA. Factors for formulating Strategies for environmental Restoration. IAEATECDOC-1032, IAEA, Vienna, Austria, July IAEA. July 1998.
[17]
IAEA. Non-technical Factors impacting on the Decision Making Processes in
environmental Remediation. IAEA-TECDOC-1279, IAEA, Vienna, Austria, April 2002.
[18]
HMIP. Environmental, Economic and BPEO Assessment. Principles for Integrated
Pollution Control. Version 5.0, 1 July 1993. Paper presented at HMIP seminar, 16 July
1993.
[19]
HARRIS, M. R., SMITH, M. A. and HERBERT, S. M. Remedial Treatment for
contaminated Land. Volumes I-XII, Special Publications 100-112, CIRIA, 1995-98.
[20]
MALLET, H. Technical Options for managing contaminated Land. CIRI-6349A,
CIRIA SAFEGROUNDS, October 2002.
[21]
USEPA. Technological Approaches to the Cleanup of radiologically contaminated
Superfund Sites. EPA/540/2-88/002, August 1988.
[22]
IAEA. Technologies for Remediation of radioactively contaminated Sites. IAEATECDOC-1086, IAEA, Vienna, Austria, July 1999.
[23]
IAEA. Technical Options for the Remediation of contaminated Groundwater. IAEATECDOC-1088, IAEA, Vienna, Austria, June 1999.
[24]
IAEA. Remediation of Sites with dispersed radioactive Contamination. IAEATECDOC-xxxx, IAEA, Vienna, Austria, To be published, 2003.
[25]
IAEA. Environmental Contamination by naturally occurring radioactive Material
(NORM) and Technologies for Mitigation. IAEA-TECDOC-xxxx, IAEA, Vienna, Austria, To be
published, 2004.
[26]
IAEA. Remediation of Sites contaminated by hazardous and by radioactive
Substances. IAEA-TECDOC-xxxx, IAEA, Vienna, Austria, To be published, 2004.
[27]
IAEA. Compliance Monitoring for remediated Sites. IAEA-TECDOC-1118, IAEA,
Vienna, Austria, October 1999.
[28]
STEARN, S. M. Reclamation of non-nuclear sites contaminated with radioactive
waste: A regulator’s view. International Symposium on Remediation and Restoration of
Radioactive-contaminated Sites in Europe. 11-15 October, 1993. Antwerp, Belgium.
Commission of the European Communities.
[29]
NRPB. Revised generalised derived limits for radioisotopes of strontium, iodine,
caesium, plutonium, americium and curium. NRPB-GS8 (1987). Chilton, Oxfordshire.
[30]
FELLINGHAM, L. R., MAY, N. A. and SNOOKS, W. A. The Characterisation and
Remediation of Radiological Contamination at the Southern Storage Area, Harwell, England.
Second Int. Conf. on Environmental Restoration in Eastern Europe, Budapest’94. Budapest,
Hungary, 1994.
[31]
MAY, N.A. Radiological clearance of the Southern Storage Area, May 1991
Appendix 2 in FOWLER, J.P. Environmental impact assessment - Southern Storage Area.
Report NuSEG(94)P196, March 1995. United Kingdom Atomic Energy Authority.
[32]
FELLINGHAM, L. R., GRAHAM, A. and STIFF, S. Characterisation and Remediation
of Beryllium Waste Pits in the Southern Storage Area at Harwell. Proceedings of ICEM ‘03:
The 9th International Conference on Radioactive Waste Management and Environmental
Remediation. September 21 – 25, 2003, Oxford, England
[33]
WILLIAMS, G.A.(Editor). Inhalation hazard assessment at Maralinga and Emu,
ARL/TR087, May 1990 (Australian Radiation Laboratory, Department of Community Services
and Health, Yallambie, Victoria).
[34] RAWSON, R, PERKINS, C. and FELLINGHAM, L. R. Rehabilitation of the Former
British Nuclear Weapons Test Site at Maralinga in South Australia, Australia. Radwaste,
4(6),10-15, (1997).
RWE NUKEM
Strategic Considerations in the
Remediation of contaminated
Sites in the United Kingdom
L R Fellingham
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Structure of the Presentation
„ Types of radioactively contaminated sites in the United
Kingdom
„ The existing and developing UK regulatory framework
„ Characterisation and assessment methods for
contaminated sites
„ Clean-up targets and their development
„ Remediation approaches and techniques
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1
Types of Radioactively Contaminated
Sites
„ Nuclear industry research, fuel production, reprocessing and power
generation sites
„ Nuclear Submarine servicing facilities
„ Nuclear weapons production facilities
„ Current and former military bases and research facilities (primarily
226Ra)
„ Overseas former nuclear weapons test sites
„ Industrial, medical, agricultural, etc, research sites
„ NORM sites:
-
luminising facilities
-
oil and gas production
-
phosphate manufacture and processing
-
ore processing, smelting and waste users, etc.
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2
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3
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4
UK Definition of Contaminated Land
EA Definition for Chemical Contaminated Sites requires Source Pathway - Receptor Linkage
„ Source - Contaminant or potential pollutant in, on or under land with
potential to cause harm or pollute controlled waters
„ Receptor - Living organisms, ecological system or property, which is
likely to be harmed by contaminant or controlled waters which are or
could be polluted by contaminant
„ Pathway - One or more routes or means by which a receptor is or
could be affected by a contaminant
EA Definition of Radioactively Contaminated Site requires only
that radioactive contamination be present
NII Definition of non-Radioactively Contaminated Site is that
there should be NO danger from ionising radiation
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UK Regulatory Framework and
Guidance (1)
„
Radioactive Substances Act 1993
„
Exemption Orders
-
Substances of Low Activity, SI No. 1002, 1986 and
amendment SI No. 647 1992
-
Phosphatic Substances, Rare Earths, etc. SI 2648, 1962
„
EURATOM Basic Safety Standards Directive 96/29, 13 May 1996
„
Ionising Radiations Regulations 1999
„
Environmental Protection Act 1990, Part IIA/ Environment Act
1995 Section 57
„
Water Resources Act 1991 (re: Groundwater)
„
Control of Substances Hazardous to Health Regulations 1999
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5
UK Regulatory Framework and
Guidance (2)
„
Nuclear Installations Act 1965
„
Nuclear Safety Directorate of Health and Safety Executive: Guidance
for Inspectors on the Management of Radioactive Materials and
Radioactive Waste on Nuclear Licensed Sites; and Guidance for
Inspectors on the Decommissioning of Nuclear Licensed Sites,
13 March 2001.
„
DETR Consultation Paper 1998, “Control and Remediation of
Radioactively Contaminated Land”
„
NRPB-M728 “Radiological Protection Objectives for Land
contaminated with Radionuclides”, 1996
„
CIRIA Safegrounds: Development and Dissemination of good Practice
on the Management of radioactively and chemically contaminated
Land on nuclear and defence Sites in the UK, etc.
„
IAEA TECDOC-987 “Application of Radiation Protection Principles to
the Cleanup of contaminated Areas”
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Waste Categories and their Limits (1)
1.
2.
Waste Characteristics
Specific Activity,
Bq/g
Waste
Category
Wastes containing manmade radionuclides
≤ 0.4
Exempt
> 0.4
LLW
Wastes containing
mixtures of Schedule 1
elements only
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≤ (Schedule 1,
Column 2 limit for
each element)
> (Schedule 1,
Column 2 limits)
and ≤ 14.8
> 14.8
De minimus
Exempt
LLW
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6
Waste Categories and their Limits (2)
3.
Waste
Characteristics
Wastes containing
mixtures of man-made
radionuclides and
Schedule 1 elements
Specific Activity, Bq/g
Waste Category
≤ 0.4 (excluding
contributions from all
Schedule 1 elements
and their daughters,
provided none exceed
their Schedule 1 Column
2 limits)
Exempt
> 0.4 (excluding
contributions from all
Schedule 1 elements,
which do not exceed
their Schedule 1 Column
2 limits, and their
daughters)
LLW
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Waste Categories and their Limits (3)
4.
Waste
Characteristics
Wastes containing
mixtures of man-made
radionuclides and
Schedule 1 elements
Specific Activity, Bq/g
≤ 4 Bq(βγ)/cm3 and no
individual items with
> 40 kBq activity
Waste Category
VLLW
(“Dustbin” limit)
≤ 40 Bq(βγ)/cm3, if only
β-emitters (3H and/or
14
C) present and no
individual items with
> 400 kBq activity
5.
≤ 40 Bq/g (UKAEA
category, currently
without regulatory
approval)
6.
>4 GBq(α)/te
>12 GBq(βγ)/te
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VLRM
ILW
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7
Waste Categories and their Limits Common Activity averaging Volumes
There is no specific regulatory guidance. However, HPA
(NRPB) guidance is 1 m3/1 Te. Practice is:
„ Exempt – Skip (5-7 m3), Ro-Ro containers (10-20 m3)
„ VLLW – 100 L – 1.1 m3 (Dustbins), soil and rubble as for
Exempt
„ VLRM - Half-height ISO (HHISO) freight container (~13 m3),
„ LLW - Half-height ISO freight container (~13 m3), IP-2 220 L
drum, etc.
„ ILW – Containers up to 500 L drum and 2 m3 box
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9
Waste Disposal Options
Exempt
Commercial landfill (Typical cost £30100/Te), recycle
VLLW
Commercial landfill (Typical cost £30100/Te)
VLRM
Store on site to await regulatory approval
LLW
Drigg, selected landfills
Drigg capacity is very limited, dominated by
Sellafield operational wastes, with high cost
(£3k/m3 and nuclide specific limits)
ILW
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Condition (Nirex Letter of Comfort),on-site
storage (Typical cost £30-300k/m3)
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ICRP 60
„
Practices - Human activities which increase overall
exposure to radiation by introducing new or modifying
existing sources, pathways and individuals to radiation
exposure.
Interventions - Situations where sources, pathways and
exposed individuals exist and are not controlled, when
decisions about control measures are being considered.
In the United Kingdom site remediation activities are almost
invariably treated as practices, irrespective of the origin or
nature of the contamination. Hence standards applicable to
practices are applied.
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10
Key Principles for the Management of
contaminated Land (1)
„ Principle 1: Protection of people and the environment
The fundamental objective of managing contaminated land on
nuclear-licensed sites and defence sites should be to achieve a
high level of protection of people and the environment, now and in
the future.
„ Principle 2: Stakeholder involvement
Site owners/operators should develop and use stakeholder
involvement strategies in the management of contaminated land. In
general, a broad range of stakeholders should be invited to
participate in decision-making.
„ Principle 3: Identifying the preferred land management option
Site owners/operators should identify their preferred management
option (or options) for contaminated land by carrying out a
comprehensive, systematic and consultative assessment of all
possible options. The assessment should be based on a range of
factors that are of concern to stakeholders, including health, safety
and environmental impacts and various technical, social and
financial factors.
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Key Principles for the Management of
contaminated Land (2)
„ Principle 4: Immediate action
Site owners/operators should take measures immediately to monitor
and control all known (or suspected) contamination and continue
such measures until an acceptable management option has been
identified and implemented.
„ Principle 5: Record-keeping
Site owners/operators should make comprehensive records of the
nature and extent of contamination, the process of deciding on the
management option for the contaminated land and the findings during
the implementation and validation of the option. All records should be
kept and updated as necessary.
The key principles apply primarily to options for the long-term
management of contaminated land. The extent to which some of the
principles are to be applied depends on the scale of the contaminated
land problem.
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11
Stages in the Remediation Process
„ Review of history of site, potential contaminants and contaminative
processes
„ Site investigation to determine nature and extent of contamination
„ Development of conceptual model of contamination spread
„ Identification of potential remediation options
„ Risk assessment (workers, public now and future, environment) and
cost benefit analysis (Environmental Impact Assessments and Safety
Cases)
„ Interactions with regulatory authorities
„ Selection and design of preferred management option, including
clean-up
„ Implementation of preferred option
„ Monitoring and certification of achievement of clean-up standards
„ Close out of works and demobilisation
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12
Purposes of Characterisation
„ Determine current level of hazard posed by site
„ Assess long-term nature of risk (risk
assessment/pathways)
„ Input to planning remediation approach and clearance
criteria
„ Identify wastes categorisation/minimisation options and
disposal route planning
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13
Potential Management Options
„ Do nothing (Status quo)
„ Replace part or whole of locally-derived food sources with
food imported from uncontaminated areas
„ Replace part or whole of locally-derived food sources with
food imported from uncontaminated areas
„ Restrict access to contaminated areas
„ Dilute contamination by mixing with uncontaminated soil,
etc
„ Stabilise surfaces of affected areas to minimise spread of
contaminated dusts, surface run-off, etc
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Potential Management Options - 2
„ Cap contaminated areas with imported clean material to
minimise direct radiation, active dust generation, etc
„ Immobilise contamination on-site, e.g. by cementation,
vitrification, etc
„ Retard radionuclide migration through surface and
groundwaters by use of barriers, e.g. reed beds, sorbentloaded vertical barriers emplaced to cut-off groundwater
flows, etc.
„ Physically remove contamination and dispose of in an
engineered repository either on-site or elsewhere
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14
Remediation Approaches
„ Removal of source to a more suitable disposal or storage site
- bulk separation, conventional earth moving, scrapping, turf removal
- selective separation, e,g. physical methods (gravity settling,
screening, settling, flotation), soil washing, chemical extraction,
electroremediation, phytoremediation
„ Containment on site
- partial or complete encasement, e.g. capping, sub-surface barriers,
purpose-built vaults
- immobilisation, e.g. cement-based solidification, chemical fixation,
in-situ vitrification
„ Source dilution
„ Control
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Timing of Remediation
Leave remediation until final decommissioning of site unless:
„ Contaminated area presents operational risk;
„ Contamination is mobile and threatens:
- controlled waters, i.e. rivers,lakes,ground- and coastal waters;
- off-site properties;
- significantly increased clean-up costs
„ Contaminated area is required for new facilities
„ Remediation is cost effective in reducing security, regulatory,
licensing, etc, requirements and costs
„ Controlled nature of area affects development of adjacent land,
e.g. Section 106 agreements under Planning Law
„ Concerns over continued availability of treatment facilities,
disposal routes, stricter future standards, regulations, etc, and
associated costs.
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15
The Assessment Process
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Cost Benefit Analysis
„ Express all factors relevant to a decision in monetary terms,
e.g. health detriments expressed as value of unit individual
or collective dose received or per statistical life or injury
received
„ Evaluate the total cost of the remedial action as the sum of
the cost of the protection and the value of the individual and
collective doses that result after any remedial action
– Optimum action is one for which the total cost is a minimum
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16
Multi-Attribute Utility Analysis
(MAUA)
„ Decision-aiding Tool
„ Relevant financial, environmental and health factors
accounted for and comparable
„ Comparison of different Sites and Problems with
Categorisation of Liabilities
„ Basis for ranking remediation Options and Priorities
„ Source-Pathway-Receptor Approach
Small Site Variant
„ More qualitative Scoring on multi-point Scale
„ Greater Use of Expert Judgement to overcome Data
Deficiencies
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The Decision-Making Process
Non-radiological Health
Impacts
Financial Impacts
- Initial cost
- Maximum annual outlay
during implementation
- Long-term annual outlay
- Discounted outlay
- Accident risks to workers
- Accident risks to members
of the public
- Disease morbidity and
mortality in workers
- Disease morbidity and
mortality in members of
the public
Impacts on Natural and
Agricultural Environments
- Natural ecosystems
-Agricultural ecosystems
-International implications,e.g.
OSPAR, fishing stocks,oil, gas
Radiological Impacts
-Annual effective dose to
workers and to public
- Collective dose to workers
-Collective dose to members
of the public by timeframe,
- Operational vs. long-term
impacts, time discounting rate
(medical advances,longevity, etc.)
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Decision
Process
Socio-economic Impacts
-Employment, skill-base
-Facilities and Infrastructure
-Value of land (cost, location,
minerals,population proximity,
potential for reuse)
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17
Assessment Criteria for Remedial
Options
„ Expected radiological, toxicological and other Impacts on the
Environment, current and as a Result of implementing
remedial Works
„ Compliance with European and World Best Practice
(BPEO/BPM/BATNEEC)
„ Expected Land and Water Quality
„ Cost Effectiveness of Remediation, i.e. total Cost and TimeExpenditure Profile
„ Technical Feasibility and Effectiveness
„ Secondary Waste Arisings, etc.
„ Social and Economic Effects of Remediation, e.g.
Employment
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RWE NUKEM
37
RWE NUKEM
38
19
RWE NUKEM • 2006-05-17
RWE NUKEM
39
20