Ann. nucl. Energy, Vol. 15, No. 2, p. 111, 1988 Pergamon Press plc. Printed in Great Britain

PRESS RELEASE F R O M THE N R P B

SOLID RADIOACTIVE WASTE FROM FUSION REACTORS

A preliminary assessment t of the radiological implications of various ways of managing the solid radioactive waste which would be produced during the operation of fusion reactors has been published by the NRPB. The study was partly funded by the Culham Laboratory of the U.K. AEA.

In a fusion reactor, light atomic nuclei-- in this case those of deuterium and t r i t i u ~ r e a c t to produce a nucleus heavier than either of them, with the release of large amounts of energy. Fusion reactors are therefore a possible new source o f energy.

Al though the commercial utilization of fusion power is still a long way in the future, it is desirable to establish, even at this early stage, the safety and environmental effects of the operation of fusion reactors.

Solid waste would arise primarily because radioactivity is induced in structural materials, some of which would need to be replaced during the operational lifetime of the reactor. For each year of operation o f a fusion reactor, a few hundred tonnes of waste would be produced, and the report is con- cerned with the doses to the public after disposal of this radioactive waste.

The radiological problems of the management of the wastes will depend on the details of the radioactive materials present, particularly the high-energy 7-emitters which tend to limit the feasible options for waste handling, and those long lived radionuclides which might, if present in sufficient amounts , result in significant radiological impact after dis- posal in a waste repository.

There is, therefore, work within the U.K. fusion pro- gramme aimed at reducing the radionuclide inventory by the substitution of one or two elements in conventional steels

~" Report NRPB-R210, Radiological Aspects of the Man- agement of Solid Wastes from the Operation of D T fusion reactors, by J. P. Davis and G. M. Smith. HMSO, £6.00.

or by the choice of low activation structural materials such as vanadium alloys.

The starting point for this study was a detailed statement of the radionuclide inventories for each of a range of potential structural materials. The basic features of the inventories, including the heat output , their time development and the associated radiological data, were considered and the most likely contributors to radiological impact identified.

A range of disposal options were considered, including shallow and deep disposal in land based repositories and disposal on the bed of the deep ocean. The advantages of various storage periods prior to disposal were examined. The advantages of recycling the structural materials were also considered.

The main conclusions of the report are :

• None of the waste materials is likely to be considered suitable for shallow land burial, particularly when the risks due to inadvertent human intrusion are taken into account.

• All of the materials could be disposed of at low risk to the public by deep geological burial, or on the bed of the deep ocean.

• There are no major post-disposal safety advantages in using the lower activation materials considered, al though there may be considerable operational advan- tages. Other alternative materials may be worth con- sideration.

• Recycling of the waste could have some post-disposal radiological advantages, but the extra dose to workers and the economic and strategic advantages need also be taken into account.

• More information is required about the quantities of some radionuclides likely to be produced and their behaviour in the geosphere and biosphere, notably car- bon- 14 and rhenium-186m, in order to guide the further development of suitable candidate structural materials.

Further information : Matthew Gaines, Gill Wilkinson. Tel. 0235 831600.

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