The long-term safe condition of
sealed radioactive sources in schools
Ralph Whitcher
ABSTRACT Sealed radioactive sources for school science became available during the 1950s from
educational equipment suppliers and by the 1960s and early 1970s many UK secondary schools had
purchased sets of them. These sources have been in use since then, which raises the question of
their safe service life. A study was undertaken to examine the condition of a relatively large sample
of school sources to see whether there are signs of source integrity beginning to fail and whether
there are any patterns to failures, particularly those that may be age-related. The findings may be
helpful to schools when undertaking reviews of the sources they hold and making judgements on
keeping older sources in continued use.
Sealed radioactive sources for school science
became available during the 1950s from
educational equipment suppliers and by the 1960s
and early 1970s many secondary schools had
purchased sets of them. UK suppliers of school
radioactive sources at that time included Griffin
& George (now Griffin Education), Philip Harris,
Panax, Nicholson, and Labgear (of these, only
Philip Harris supplies sealed sources today). The
sources have been in use since then, which raises
the question of their safe service life. Generally,
any piece of equipment, even if used correctly
and maintained properly, will eventually wear or
degrade to the point that it should be taken out
of service, and sealed radioactive sources are no
different. A study was undertaken to examine the
condition of a relatively large sample of school
sealed sources to see whether there are signs of
source integrity beginning to fail and whether there
are any patterns to failures, particularly those that
may be age-related. The findings of this study may
be helpful to schools when undertaking reviews of
the sources they hold and making judgements on
keeping older sources in continued use (although
schools must follow their employer’s guidance).
The Approved Code of Practice (ACoP) to
the Ionising Radiations Regulations 1999 states
that where a sealed source reaches the end of its
working life, a review of its condition is advised
with a view to replacing the source or having it
examined by the supplier or manufacturer. If the
evidence is that the source is safe for continued
use, the ACoP recommends that a time limit should
be set on its continued use, after which a further
review should be undertaken (HMSO, 2000).
School source construction
School sealed sources comprise an active
component (the part that is radioactive) and a
holder (the part that holds and protects the active
component). Griffin & George, Philip Harris,
Panax and Nicholson source holders were a cuptype design, while those from Labgear were a
plate-type design. These designs were approved by
the Department of Education and Science (now the
Department for Children, Schools and Families)
for school purchase. The most popular is the cuptype (see Figures 1 and 2). There were variations
in the design, but generally the construction is a
recessed plated-metal (commonly brass) cylindrical
source holder, roughly 13 mm diameter and 8 mm
long. The cup has a 4 mm diameter spigot so the
source can be manipulated with a suitable tool. The
active component (a radioactive foil) is held inside
the cup by a circular spring clip and protected by
a wire mesh. The spring clip is not located within
a groove; it stays in place by friction. In some
designs the foil is also secured by adhesive. In the
Panax cup-type design, the foil is often secured
just with adhesive; the spigot and cup are fastened
together by a circlip and epoxy resin adhesive.
In the cup-type sources, the strontium-90,
americium-241, plutonium-239 and radium-226
active components are foils; the active component
SSR March 2009, 90(332)
113
The long-term safe condition of sealed radioactive sources in schools
of the cobalt-60 source is a small pellet of cobalt-60
metal secured with adhesive and screened by an
aluminium filter to attenuate the beta emissions. The
Panax cobalt-60 source (labelled S3) has a longer
cylindrical holder with a small diameter recess and
the pellet is embedded inside the cylinder.
The Panax 333 kBq strontium-90 source
(labelled S4) has an active component, a small
foil, in a cylindrical housing with a collimating
slit; the housing is pressed into a clear plastic
block (Figure 3).
The plate-type design from Labgear is a 50 mm
square piece of plastic, recessed in the centre, with
the active component secured with epoxy resin
adhesive (Figures 4 and 5). The strontium-90,
americium-241 and radium-226 active components
are disc foils. The cobalt-60 active component is a
cobalt-60 pellet of metal but without an aluminium
disc filter, and the thorium-232 is a thorium
Whitcher
compound embedded in epoxy resin adhesive.
Some Labgear plates have wire mesh over the
front to protect the active component.
Figure 3 Panax S4 source; an aluminium protective
cap covers the collimating slit
Figure 1 Diagram of a cup-type source construction;
there were variations in this design
Figure 4 Diagram of a plate source construction;
there were variations in the design
Figure 2 The front of a cup-type source
Figure 5 A Labgear plate-style strontium-90 source
114 SSR March 2009, 90(332)
Whitcher
The long-term safe condition of sealed radioactive sources in schools
The original manufacturer of the active
components for school sources assembled
in the UK was the United Kingdom Atomic
Energy Authority Radiochemical Centre. (The
Radiochemical Centre has changed ownership
several times since, to become Amersham, then
Nycomed-Amersham. Currently the sealed-source
manufacturing is owned by nuclitec GmbH.)
The cobalt-60 active component was made by
irradiating cobalt-59 metal, the naturally occurring
non-radioactive isotope of cobalt, in an intense
neutron field. The other active components were
laminated foils made by sintering a radioactive
compound, e.g. plutonium oxide, radium sulphate,
strontium carbonate or americium oxide, with
silver or gold metal, into a briquette. This
was backed with silver and faced with gold or
gold–palladium, and then rolled into a sheet foil.
Discs were stamped from the sheet foil (in Panax
sources, squares were cut from the sheet foil). Note
that since the late 1990s, the construction of the
strontium-90 foil changed. In the current design,
the radioactive material is evenly deposited onto an
aluminium backing plate and the plate is anodised
to seal the activity into a thin surface layer.
The literature supplied with some sources gave
the americium-241 and radium-226 foil sources
a recommended working life (RWL) of ten years
(Amersham, 1991). In the discussions between
the Scottish Schools Equipment Research Centre
(SSERC) and Amersham in 1990, Amersham
gave a RWL of ten years for americium-241 and
strontium-90 foils, but five years for the radium226 foil and the cobalt-60 pellet (SSERC, 2008).
Information from former Amersham staff (personal
communication, 2004) indicated that these figures
were not based on any direct evidence of failure,
but an expectation that the sources would retain
integrity for at least the RWL.
The author is aware of two earlier surveys of
school radioactive sources. The first, in 1974, was
carried out by the National Radiological Protection
Board (now the Radiation Protection Division in the
Health Protection Agency). It tested 15 plutonium239 school sealed sources following concerns about
the radiotoxicity of plutonium (NRPB, 1974).
Under quite brutal destructive tests, including
heating one source in a butane flame for five
minutes, the sources retained remarkable integrity.
However, the survey did find evidence to suggest
that the manufacturing process of plutonium-239
and radium-226 foil discs by the Radiochemical
Centre did not completely seal the active material
between the metal layers; tiny fragments may
become dislodged from the edge during the process
of stamping out the discs from the sheet foil,
possibly causing minute traces of contamination.
The NRPB report pointed out that this leakage was
orders of magnitude smaller than the limits for
members of the public. The NRPB concluded that
demonstrations and experiments using the plutonium
sources could be carried out with a very high degree
of safety. The second survey was carried out by
CLEAPSE (now the CLEAPSS School Science
Service) in 1982 and involved testing and inspecting
sources from ten educational establishments holding
sealed sources that were at least ten years old. The
survey concluded that, among other things, no
evidence was found that mechanical or chemical
damage to the source face was causing a leak of
active material (CLEAPSE, 1982).
The study and checks chosen to test
source integrity
The tests chosen for this study were a remote
visual examination of the radioactive foil surface,
and a wipe test for contamination. This study
was carried out on a total of 250 sealed sources,
detailed in Table 1.
The sources were held by 41 establishments
mostly around the West Sussex area: 34 local
authority schools, two independent schools, three
sixth-form colleges, one further education college
and one school science support establishment. The
Table 1 Number of sources tested, by supplier and radionuclide
Supplier
Griffin & George
Panax
Philip Harris
Labgear
Nicholson
Totals
Am-241
17
25
7
1
0
50
Co-60
12
16
8
1
1
38
Pu-239
13
0
8
0
1
22
Ra-226
25
6
23
3
2
59
Sr-90
23
37
16
2
2
80
Th-232
1
1
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115
The long-term safe condition of sealed radioactive sources in schools
leak test was based on the ISO 9978:1992 standard;
the particular test chosen was the wet wipe test
because it is suitable for recurrent tests and because
the other methods, such as the immersion test,
could cause damage to the source. The gaseous
emanation test for radium-226 sources was
inappropriate for this study because it would not
reveal leakage of radium-226 material, whereas the
wipe would pick up both radon-222 decay products
and radium-226 contamination. In the wipe test,
the accessible external surface (not the active
component) of the source is wiped and if there is
more than 200 Bq of contamination removed by the
wipe, the source is failed. The wipe in this study
was a small disc of cellulose filter paper barely
dampened with ethanol (this method is effective in
removing surface contamination without damaging
the source). A sample of wipes was also taken from
the lead pots in which the sources were stored.
The Labgear sources were wiped with a dry disc to
avoid the slight risk of damage to the plastic mount.
A Rackbeta 1217 liquid scintillation
counter (LSC) was used for detecting any
contamination on the wipes. This is a device
using photodetectors for detecting and counting
scintillations produced by particulate ionising
radiations in a scintillating fluid. The advantage
of an LSC is the high detection efficiency,
approaching 100% for alpha and higher energy
beta emissions, and low background, giving a low
minimum detectable activity.
Where significant contamination was found, a
second measurement was taken using the LSC to
give information on the energy spectrum from the
alpha and beta emissions. The LSC spectrum is
not adequate to identify a radionuclide uniquely,
but it can be used comparatively to rule out
radionuclides or to compare samples. The gamma
spectrum on selected wipes was also investigated
using a liquid-nitrogen-cooled hyper-pure
germanium (HPGe) detector gamma spectrometer
with multi-channel analyser. This gave a high
resolution of gamma emission energy that would
enable any contamination that emitted significant
gamma radiation to be identified.
The surfaces of the sources were examined
using an Olympus Iplex remote inspection videocamera. The 3.5 mm optical adapter at the end of
the remote optical cable and illumination enabled
it to be placed very close to the protective mesh
of the cup source to give a magnified view of the
interior of the source holder and the foil surface on
116 SSR March 2009, 90(332)
Whitcher
a remote screen. Photographs of selected sources
were also taken remotely using a Nikon 8700
digital camera. This has an 8 megapixel CCD and
a 30 mm macro lens facility. Owing to sourceholder designs, there were limitations to the visual
inspection. In the cobalt-60 cup-type source, the
active component is obscured by an aluminium
disc filter so the visual examination was limited to
examining the filter. The Panax cobalt-60 source
was also limited to examining the visible surface
because the cobalt-60 pellet is embedded inside
the cylinder. The other Panax cup-type sources
have a close mesh weave which obscures the foil
surface to the extent that a thorough examination
is not feasible. The Panax S4 strontium-90 foil is
also largely obscured and only part of the foil can
be viewed through the collimating slit.
The local authority records dating back to
the 1960s gave the dates that local authority
schools had received authorisation to purchase
the sources. This date was used as a measure of
the age of the sources in looking for any trends in
degradation. Some caution is needed with these
data; the accuracy could not be verified as they
were not part of a quality assurance process.
Results of the visual examination
Most of the active component surfaces in the cuptype sources from Griffin & George, Philip Harris
and Nicholson showed no obvious evidence
of damage or degradation. As far as they were
able to be examined, the Panax foils appeared to
be in satisfactory condition too. On some foils
there were faint marks, likely to be from the
manufacturing process rather from any subsequent
abuse; the marks were light and would have been
difficult to achieve by scratching the foil with
the mesh in place. Some foils had small areas
of light blemishes. Three cup-type sources from
establishment L showed significant corrosion on
the front mesh and blemishes on the surfaces of
the foils. The sources had been stored close to
a defective protactinium generator and this had
almost certainly caused the damage.
There were five sources where the foil had
moved off-centre so that the edge of the circular
foil was revealed. This did not show in any Panax
source, but other than that there was no pattern to
the supplier, date of approval or radionuclide type
of these sources. There were another two sources
where the spring clip had moved forward leaving
the foil loose, possibly from them being dropped
Whitcher
The long-term safe condition of sealed radioactive sources in schools
and the spring clip dislodged (Figure 6). One of
these two sources showed clear signs of being
dropped or struck on the edges.
The foils in the S4 strontium-90 sources could
be seen partially, and from what was observed
there was no evidence of surface degradation.
All six Labgear sources (from three
establishments) with foil discs had large patches
of dark discolouration on the surface of the foils,
easily visible. This was mainly where the foils were
in contact with the epoxy resin adhesive, but not
wholly. The epoxy resin adhesive was discoloured
in most of the sources. There was a suspect fissure
on an americium-241 foil (Figure 7). The suspect
fissure was under the epoxy resin adhesive and
could not be investigated further. Many of the
sources had what appeared to be stress cracks in
the epoxy resin. The condition of the epoxy resin
adhesive in six of the sources was such that it was
decided not to test them any further but to take them
out of service and place them in a sealed container;
it was plausible that a wipe test could dislodge
fragments of epoxy resin, possibly releasing
fragments of the foils. This left just two Labgear
sources, both radium-226, for leak-testing.
Of the 244 sources that were leak-tested,
wipes from 227 sources showed no detectable
contamination. Of the 17 sources that showed
contamination on the wipes, 16 were radium-226
sources and one was a plutonium-239 source
held by establishment B. None of the wipes
exceeded the 200 Bq fail threshold and all but
one were a small fraction of it (Table 2). Note
that the lower the estimated activity, the greater
the uncertainty of the estimate. (When deciding
whether contamination is present, there is the
problem of the count from background radiation.
If the background count, which is random in
nature, fluctuates above average on a particular
measurement, it may be wrongly interpreted as the
presence of contamination – a false positive. To
reduce the chance of this, a decision-level count is
chosen high enough above the estimated average
background count to be confident of avoiding
false positives, but not so high that significant
contamination is missed – a false negative. The
decision level for this study was chosen at a 99%
confidence level of avoiding false positives. This
gave an estimated minimum detectable activity of
contamination, using the LSC, of 0.34 Bq.)
The contamination arising from radium-226
sources was expected because radium-226 decays
to radon-222, and in some school radium-226
sources (the evidence suggests about 30% of
them) radon is able to migrate through the thin foil
surface and edge to cause marked contamination;
Figure 6 The foil has moved out of place; the ­bottom
edge of the foil has moved forward and over the
spring clip
Figure 7 Centre of a Labgear americium-241 source
showing surface degradation and suspect fissure
(bottom left); this is the reverse side of the plate source
Results from the leak test
SSR March 2009, 90(332)
117
The long-term safe condition of sealed radioactive sources in schools
Whitcher
Table 2 Activity measured on the wipes with detectable contamination
Type
Ra-226
Ra-226
Ra-226
Ra-226
Pu-239
Ra-226
Ra-226
Ra-226
Ra-226
Ra-226
Ra-226
Ra-226
Ra-226
Ra-226
Ra-226
Ra-226
Ra-226
Activity/kBq
185
185
185
185
3.7
185
185
185
185
185
185
185
185
185
185
185
185
Supplier
Establishment*
Panax
Philip Harris
Griffin & George
Philip Harris
Griffin & George
Philip Harris
Griffin & George
Philip Harris
Griffin & George
Philip Harris
Griffin & George
Philip Harris
Griffin & George
Griffin & George
Philip Harris
Griffin & George
Labgear
A
A
B
C
B
C
D
A
E
A
F
C
G
H
I
J
K
Approval date/year
1966
1966
1966
Not known
1966
Not known
Not known
1966
Not known
1966
1970
Not known
Not known
1960
1965
Not known
Not known
Estimated activity
on wipe/Bq
124
6.6
6.0
6.0
5.5
2.9
1.6
1.4
1.3
1.2
0.80
0.76
0.73
0.52
0.47
0.35
0.33
* The codes A–L have been assigned to distinguish establishments of interest in this study.
this is normal because the foil design was not a
guaranteed encapsulation of the radon-222. The
radon-222 decays and the radioactive daughter
products gradually accumulate on the surfaces of
the source and storage pot. Low levels of radon222 contamination are not a concern if the sources
and pots are cleaned periodically – keep in mind
that the average concentration of radon-222 in UK
homes is about 20 Bq m–3 (Watson et al., 2005).
The contamination of 124 Bq on the wipe of
a Panax radium-226 source from establishment A
Figure 8 Gamma spectrum of the radium-226 wipe
118 SSR March 2009, 90(332)
was much higher than from any other source in the
study. This was much higher than was expected
from radon-222 contamination, although it was still
within the ISO 9978 200 Bq limit and would not
be a failure on this standard. A corresponding wipe
from the storage pot of the source also showed
well above average levels of contamination. The
gamma spectrum of this radium-226 wipe, using
the HPGe detector, was measured and compared to
background (Figure 8). The characteristic energy
line of 186.2 keV confirmed that radium-226
Whitcher
The long-term safe condition of sealed radioactive sources in schools
was present in the contamination, the other lines
coming from the radium-226 decay products,
bismuth-214 and lead-214.
Educational establishment A had four radium226 sources; the other three showed contamination
but at much lower levels. Cross-contamination
could not be ruled out because the storage pots
were not uniquely labelled and the sources could
have been swapped into different storage pots
after use. No radium-226 was detected on the
wipes from the other three radium sources from
establishment A. (The minimum detectable activity
was estimated to be 1.8 Bq, the efficiency of the
HPGe detector being much lower than the LSC.)
Figure 9 shows a scatter diagram of the LSC
gross count rate of the wipes, in counts s–1, against
the year that government approval was given
to purchase the radium-226 sources. Unknown
dates are plotted at the end of the scatter diagram.
Note that the radium-226 cup-type source from
UK suppliers was discontinued around 1997. The
background count rate is marked with a dotted line.
The correlation coefficient (using CORREL in
Microsoft Excel) gave a value of –0.14 (ignoring
the data from sources of unknown date of
approval). This is a weak negative correlation and
does not support a hypothesis that older radium-226
sources give higher levels of contamination.
The contamination from the wipe of the
plutonium-239 source was investigated by
gamma-spectrum analysis, measured over a
time of 250 000 seconds. This revealed no
significant characteristic gamma energy above
background; this is consistent with a plutonium-
239 contamination because there is negligible
photon emission beyond the low-energy part of
the spectrum.
An energy spectrum plot of the particulate
emissions from the wipe of the plutonium-239
source, measured over 256 logarithmically
separated channels using the LSC, was
significantly different compared to the spectra
of the wipes from the radium-226 sources (see
Figure 10 for examples). This eliminated crosscontamination by radon-222 progeny from the
radium-226 source that the school also held. A
spectrum plot of a small quantity of low-activity
plutonium-239 agreed with that from the wipe
from the plutonium-239 source. From this it can
be concluded with reasonable confidence that the
contamination on the plutonium-239 wipe was
from a small quantity, 5.5 Bq, of plutonium-239.
Discussion and actions
Of the 244 sources that were leak-tested, only
two results gave cause for further investigation
to check source integrity: a 1966 Panax radium226 source from establishment A, and a 1966
Griffin & George plutonium-239 source from
establishment B. The close weave of the mesh
made it difficult to examine the Panax radium226 foil surface, but from what could be seen
there was no obvious damage or degradation.
The subsequent wipe re-test of the Panax radium226 source showed a repeated high level of
contamination so it was taken out of service and
disposed of. (Establishment A held sources taking
it well beyond the standard holding of 1.1 MBq, so
Figure 9 Wipe tests: gross count rate
for Ra-226
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119
The long-term safe condition of sealed radioactive sources in schools
Whitcher
Figure 10 Liquid scintillation
counter spectrum plots
it was decided to dispose of the other radium-226
sources it held too.) The other 11 radium-226 cuptype sources listed in Table 2 were kept in service,
with advice to clean them and re-test periodically.
The visual examination of the plutonium-239
source from establishment B revealed no evidence
of damage or degradation, although the foil disc was
located slightly to one side under the spring clip,
revealing an edge of the foil disc. The source was
taken out of service, and re-tested after three months.
There was no detectable contamination from the
source or storage pot on the re-test; consequently
the source was reinstated for use. The contamination
from the plutonium-239 source could have been
from a tiny fragment that had become dislodged
from the foil edge during the process of stamping out
the disc from the sheet foil. This would be consistent
with the findings of the 1974 NRPB report in which
small traces of plutonium-239 contamination were
found on some plutonium sources and storage pots,
the largest amount being 3.3 Bq. This compares to
the 5.5 Bq found in this survey.
The three cup-type sources from establishment
L that had corroded meshes were taken out of
service and disposed of. Although the leak test
revealed no contamination, there was clear evidence
of surface degradation of the foils by the exposure to
hydrochloric acid fumes from a leaking protactinium
generator. The two cup-type sources that had loose
foils were taken out of service. Although it might be
tempting to try to relocate the foil and spring clip,
there is a risk of damaging the foil.
Generally, the Labgear sources were not in
a satisfactory condition. The visual examination
showed marked degradation. Consequently, all
eight Labgear sources in this study were taken out
of service and disposed of.
120 SSR March 2009, 90(332)
Conclusions
This study did not reveal any evidence of
age-related failure modes in the cup-type
americium-241, strontium-90, plutonium-239 and
cobalt-60 sources and the Panax S4 strontium-90
sources (although the activity of old cobalt-60
sources has decayed to the extent that they are
only useful to show the effect of half-life). A
risk assessment based on this evidence would
help support extending their service life for, say,
another ten years, provided the sources continue
to show no visual signs of damage or degradation,
and no detectable contamination by a suitable leak
test. The same conclusion can be reached for a
cup-type radium-226 source, where the source is in
satisfactory condition from a visual inspection and
there is no contamination detected by a leak test.
The evidence from this study suggests that the
contamination on radium-226 sources by radon222 is generally small. Nonetheless, this radon-222
contamination is a nuisance because it could mask
low levels of contamination from radium-226, an
indicator that the source integrity is starting to fail.
It is not possible with school science equipment
to tell if there is radium-226 contamination in
the radon-222 contamination. Consequently, for
a radium-226 cup-type source in which there is
detectable contamination on the leak-test wipe, a
cautious approach is needed in deciding whether to
extend its service life. CLEAPSS recommends that
where deposits of small quantities of radioactive
decay products are found on the outside of the
radium-226 source, the radium-226 source and
its storage pot should be cleaned carefully and
the source should then be re-tested before its next
use. If the contamination persists, the employer’s
Whitcher
The long-term safe condition of sealed radioactive sources in schools
Radiation Protection Adviser should be consulted
for advice (CLEAPSS, 2008). If the source
exhibits repeated contamination despite cleaning, it
is difficult to justify keeping the source in service.
A different approach has been taken by
SSERC; for schools in Scotland, SSERC strongly
advises that that all sources, including the
radium-226 sources, should be disposed of by an
authorised route after a time limit of three RWL
periods (SSERC, 2008).
For sources kept in service, considering that
many of the sources are now over 40 years old,
suitable leak tests and indirect visual examination
of foil surfaces (for example by using a mirror)
should be done at least yearly (the Approved Code
of Practice to the Ionising Radiations Regulations
1999 specifies a period of no more than 24
months, and recommends more frequent testing
when a sealed source is to be retained in use
beyond its recommended working life). Schools
should follow the guidance from CLEAPSS or
SSERC on inspection and testing.
The Labgear sources in this study were found
to be at the end of their service life. This study
provided no evidence to support extending the
service life of Labgear sources, although the sample
size of Labgear sources in this study was small.
It is worth noting that the activities found
on the contaminated wipes in this survey would
not be a failure using the ISO 9978 standard.
Except for one wipe, the estimated activities of
contamination on the wipes were very low – less
than 10 Bq. To put this into perspective, there is
probably as much activity from radium-226 in a
300 g bag of Brazil nuts (Watson et al., 2005).
The justification for detecting low activities in this
study is the investigation into any early evidence
of source integrity failure.
Disposal of sources
Sealed sources that are no longer in a safe
condition should be disposed of by an authorised
route. In England and Wales, the Environment
Agency has produced a guidance document
(available through CLEAPSS) that explains the
available disposal routes. SSERC has produced
guidance for schools in Scotland. Schools in
Northern Ireland should contact DENI. In some
cases it is possible to dispose of sealed sources
with normal refuse but it is important to check the
conditions that apply; these conditions vary in the
different parts of the UK.
Acknowledgements
I am greatly indebted to Dr Alan Flowers and staff at the School of Life Sciences at Kingston University
for their support and use of the university nuclear laboratory facilities. I also wish to thank Kieran
Agnew for joint working in the planning stages during his MSc postgraduate study at the University of
Surrey. Finally, I would like to thank the West Sussex schools and colleges and other establishments who
participated in this study.
References
Amersham (1991) Amersham safety instructions for
unpacking and use of alpha foil and sources. Ref HIO41
Issue 1.
CLEAPSE (1982) Hazards from radioactive sources in
schools and colleges. R. J. J. Orton. Unpublished.
CLEAPSS (2008) Managing ionising radiations and
radioactive substances in schools. etc. L93. Uxbridge:
CLEAPSS School Science Service.
HMSO (2000) Work with ionising radiation. Ionising
Radiations Regulations 1999 Approved Code of Practice
and Guidance. L121. Regulation 27, para 482 & 491.
London: HMSO.
NRPB (1974) The use of plutonium-239 in schools and
other educational establishments. T. Williams. NRPBR28. National Radiological Protection Board.
SSERC (2008) Protocol on the ageing and leak testing of
sealed radioactive sources. Edinburgh: Scottish Schools
Equipment Research Centre
Watson, S. J. et al. (2005) Ionising radiation exposure
of the UK population: 2005 review. HPA-RPD 001.
Chilton: Health Protection Agency/Radiation Protection
Division.
Ralph Whitcher is Chair of the Association for Science Education’s Safeguards Committee. He is
Radiation Protection Adviser for several local authorities including West Sussex County Council. He
was formerly an advisory teacher for science.
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