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INVESTIGATIONS INTO THE BEHAVIOUR OF HIGHLY COMPACTED DRY LOW LEVEL RADIOACTIVE WASTE UNDER REPOSITORY CONDITIONS

Objective

THE SUPERCOMPACTION PROCESS (IN WHICH A STEEL DRUM CONTAINING LOW LEVEL RADIOACTIVE WASTE IS SUBJECTED TO AXIAL PRESSURES OF UP TO 70 MPA) RESULTS IN A SIGNIFICANT SAVING IN THE VOLUME OF A REPOSITORY NECESSARY FOR DISPOSAL OF SUCH WASTES. WHILST IT IS LIKELY THAT SOME COMPACTED WASTE FORMS ARE INERT, FOR OTHER MATERIALS THE ENERGY DISSIPATED IN THE COMPACTION PROCESS MAY RESULT IN TIME-DEPENDENT SWELLING. SUCH EXPANSION MAY, IF RESTRAINED, INDUCE STRESSES WHICH COULD POTENTIALLY DISRUPT CONTAINERS, OR THE OVERALL INTEGRITY OF THE REPOSITORY. MANY MATERIALS SWELL WHEN WETTED, AND THE ELIMINATION OF VOIDAGE BY THE SUPERCOMPACTION PROCESS MAY SIGNIFICANTLY INCREASE THE EXTENT OF SWELLING-ON-WETTING. SUPERCOMPACTION OF THE WASTE MAY LIMIT THE MOBILITY OF SOLUBLE MATERIAL WITHIN THE WASTE; BIOLOGICAL AND CHEMICAL DEGRADATION OF WASTE AND DRUM MAY ALSO BE ALTERED BY THE SUPERCOMPACTION PROCESS.

THE PROJECT IS A SCOPING STUDY TO DETERMINE WHICH IF ANY OF THE ABOVE FACTORS ARE OF SIGNIFICANCE IN THE USE OF SUPERCOMPACTED WASTE FORMS IN A REPOSITORY. ALL WORK IS BEING CARRIED OUT ON FULL SCALE 200 LITRE DRUMS OF SIMULATED WASTE.

THE WORK IS BEING UNDERTAKEN IN COLLABORATION WITH HANSA PROJEKT GMBH, BRITISH NUCLEAR FUELS, U.K.A.E.A. UK NIREX AND THE N.I.I.
Supercompaction is a process in which drums containing low level radioactive waste are compressed at a high axial pressure of up to 70 MPa, resulting in a significant saving in the volume of a repository built to store such waste. Recent practice has been to compact waste which has been placed in a sealed primary container, typically a 200 litre steel drum. During the process of compaction the drum is squashed with its contents into a flat pellet (the compaction ratio may reach as high as 20 to 1).

Supercompaction is a procedure in which drums containing low level radioactive waste are compressed at a high axial pressure of up to 70 MPa, resulting in a significant saving in the volume of a repository built to store such waste. Recent practice of supercompaction is to compact waste which has been placed in a sealed primary container, typically a 200 litre steel drum. During compaction the drum is squashed with its contents into a flat pellet with the compaction ratio reaching as high as 20:1.
The primary objective of this work has been to investigate the physical and some of the chemical characteristics of such supercompacted pellets. All the work was carried out on full scale 200 litre drums of simulated but nonradioactive waste. Upon completion of compaction, all drums exhibited a tendency to expand. The magnitude of the ultimate expansion for dry storage was of the order of 1 mm only whereas under wet storage conditions values were up to about 10 mm. As the presence of moisture can significantly increase the expansion of compacted waste drums, or stress developed due to restraint, it is recommended that the waste repository be made water and vapour tight.
1. WASTE CHARACTERIZATION - DEFINITIONS OF RANGE AND TYPES OF LLW THAT WOULD BE CONSIDERED SUITABLE FOR SUPERCOMPACTION.
2. SIMULANT LLW SPECIFICATION - IDENTIFYING THE TYPES OF MATERIAL THAT COULD EXHIBIT INTERESTING BEHAVIOUR, AND PREPARING SCHEDULES OF DRUM CONTENTS.
3. DEFINE TEST PROGRAMME TO MONITOR DIMENSIONAL STABILITY OF COMPACTED WASTE FORMS, FORCE GENERATORS, MOBILITY OF SOLUABLE MATERIALS AND GENERATION OF GAS.
4. DESIGN, FABRICATE AND COMMISSION TEST RIGS.
5. PROCURE SIMULANT MATERIALS, PREPARE DRUMS, TRANSHIP TO HANSA PROJEKT GMBH, SUPERCOMPACT DRUMS, AND TRANSHIP BACK TO UK.
6. UNDERTAKE PHYSICAL TEST PROGRAMME ON COMPACTED DRUMS.
7. COMPLETE FINAL REPORT.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Taylor Woodrow Construction Ltd
Address
Taywood House 345 Ruislip Road
UB1 2QX Southall
United Kingdom

Participants (1)

HANSA PROJECT ANLAGENTECHNIK
Germany