Organic Waste and Residue Treatment at the NNL Preston Laboratory
H. GREENWOOD, T.I. DOCRAT, S.J. ALLINSON, D.P. COPPERSTHWAITE
Waste Management and Decommissioning Directorate, National Nuclear Laboratory
Preston Laboratory, Springfields, PR4 0XJ - UK
Introduction
Organic compounds of various kinds have been used in the nuclear industry for numerous duties in uranium chemical, metal
and ceramic processing plants. In the course of the various operations undertaken, these organic compounds have become
contaminated with uranic material, either accidentally or as an inevitable part of the process. Typically, the chemical/physical
form and/or concentration of the uranic content of the organics has prevented disposal.
In order to address the issue of contaminated organics, the National Nuclear Laboratory (NNL) has developed a suite of
treatments designed to recover uranium and/or other radioisotopes, thereby rendering the waste suitable for ultimate
disposal off-site. The developed processes are operated at considerable scale via the NNL Preston Laboratory Residues
Treatment Plant.
Residues Treatment Plant in the NNL’s Preston Laboratory
Ongoing process development
Fully installed processes
OWL (Oil Waste Leaching)
SWORD (Springfields Waste Organic Residue Digester)
OWL is a fully industrialised process used for the
treatment of contaminated oils. Approximately 200 te
of uranium-contaminated oil has been treated via
various installations within the NNL Preston
Laboratory Residues Treatment Plant. Processed oils
include “water-emulsifiable” cutting oils, lubricating
oils, hydraulic oils/fluids and “Fomblin” (fully
fluorinated) oils.
SWORD was developed to treat a specific residue comprising a resinous floor polish/PVC
matrix contaminated with gross levels of uranium dioxide (UO2).
Incineration of the residue proved very problematic, with the production of large volumes of
flammable gas and “vitrification” of the inorganic component. This latter issue resulted in the
encapsulation of uranium, rendering the furnace-treated material unleachable in anything
other than hydrofluoric acid.
10m3 process vessels
The process can be operated using various equipment within the NNL Preston Laboratory; a
large industrial scale centrifuge is available together with tanks capable of treating varying
volumes of oils (2000 dm3 oil can be treated in a single batch, though typically batch volumes
are of the order of 200 dm3). Approximately 1000 drums of oil have been treated via OWL and
tens of tonnes of uranium-contaminated TBP/OK solvent (including badly degraded solvent)
have also been treated via a process and equipment more or less identical to OWL.
Oil samples are tested via the laboratory to determine the
optimum processing conditions for the bulk residue. As such,
representative sampling is crucial, especially regarding any
settled sludge. Laboratory testing is used to investigate
whether bulk solids removal is required and at what stage
this is most advantageous. In addition, the agitation/mixing
conditions, the contact time, the number of contacts, the
operating temperature, the sulfuric acid concentration and
the oil/sulphuric acid volumetric ratio are optimised at this
Oil process testing in the laboratory
stage. The requirement for additives which can aid uranium
extraction is also assessed.
The OWL process has also been tested in conjunction
with non-uranic alpha-contaminated oils, yielding a
very high decontamination factor even in the presence
of a considerable amount of active solids. It would be
expected that OWL could easily be applied to many
other contaminated oils, though some alteration to the
chemistry might be required or be advantageous.
Direct treatment with aqueous mineral acid, caustic soda and solvents was completely
ineffectual and/or produced large volumes of intractable by-products.
NNL have developed the “wet oxidation” SWORD process to treat the target residues.
Hot concentrated sulphuric acid acts as a powerful oxidising agent. When heated, sulphuric
acid decomposes and produces nascent oxygen, which helps in the oxidation process.
Resinous floor
polish/PVC residue
H2SO4 (aq)  H2O(l)  SO2 (g)  [O]
Chipped resinous floor
polish/PVC residue
Bulk matrix destruction
CxHy 
y
y
H2SO4(aq)  xC(s)  yH2O(l) 
SO2(g)
2
2
Carbon digestion
C(s)  2H2SO4(aq)  CO2(g)  2H2O(l)  2SO2(g)
Bulk matrix destruction
Carbon digestion
The process has also been tested in conjunction with a tritiated oil, where the radioactivity is
chemically bound; in this process (TOAST, or “Tritiated Oil Advanced Sulphuric Treatment”),
the oil was initially treated in concentrated sulphuric acid at a temperature selected to
prevent oil boiling/evaporation, followed by the normal carbon digestion step. Tritium
recovery to the acid was effectively quantitative with no measurable tritium escaping as off
gas.
It is clear that the SWORD process will be applicable to a wide variety of organic wastes,
most of which will be far less intractable than the residues for which it was developed.
ARTEMIS (Advanced Residue Treatment, Enriched
Materials Integrated System)
Solids extant in the oil
1 m3 process vessels
HEU oil
processing
Mid-process solids
Post solids removal
ARTEMIS is a suite of processes designed to treat a
variety of uranic residues. The processes are
designed for solid materials which are very heavily
contaminated with hydrocarbon oils and greases,
including those which have suffered radiation
damage. Such materials often contain both low
molecular weight volatile species and heavy or waxy
organics.
Increasing number of contacts
STAR (Solvent Treatment Advanced Rig)
STAR is a small treatment plant (100 dm3 volume) which allows volatile
and flammable solvents to be treated in aqueous sulfuric acid. The rig is
ATEX rated and operates under an inert atmosphere during solvent
processing. STAR has treated a few hundred litres of uraniumcontaminated solvents in recent years.
Part of the STAR rig can also be utilised in the treatment of watermiscible solvents. This process involves the addition of caustic soda
solution to precipitate uranium for recovery.
Artemis pilot plant
STAR
installation
Recovered oil
SCIMITAR (Springfields Complex Intractable
Material, Total Actinide Removal)
SWAMP (Springfields Washing Machine Process)
SCIMITAR has been developed for the treatment of
uranium solvent extraction (SX) plant cruds. The cruds
comprise a mixture of TBP/OK, aqueous liquor (impure
uranyl nitrate/nitric acid), inorganic solids such as
zirconium hydrogen phosphate and similar, magnesium
fluoride and silica plus c. 20 % w/w organic solids; the
residues are contaminated with uranium, and with very
high levels of thorium and protactinium (as 231Pa).
The NNL-developed SWAMP uses modified industrial washing
machines to treat uranium-contaminated soft wastes such as
ventilation filters, gloves, wipes, flexible plastics, filter cloths,
lagging (e.g. Rockwool), mop heads and paper.
Some materials can be fed directly to the washing machines
while others are shredded and loaded into permeable
polypropylene bags prior to loading. Ventilation filters are
dismantled with the filter medium being placed in permeable
bags before washing. Filter casings are cleaned by jet washing.
Oil-contaminated
Oil-free residue
residue
The process utilises a proprietary solvent to remove
organic materials from solid matrices, allowing the
inorganic fraction and the recovered oil to be
treated via standard routes. The solvent, which is
recovered for reuse, is also suited to the removal of
fomblin and mixed fomblin/hydrocarbon oils.
SWAMP installation
EDX analysis of SX crud sample