Behaviour of Fission Product Caesium in LMFBR Primary Circuits: Experiments in a Small Stainless Steel Loop Containing Circulating Sodium.

摘要

The available information which can be used to determine the likely behaviour of fission product caesium, released from defective fuel pins, in the primary circuit of a sodium-cooled fast reactor has been reviewed and assessed. For a relatively small number of fuel pin failures over a reactor lifetime sup 137 Cs is potentially a predominant contributor to dose rates on out-of-core steel components if the adsorption of caesium on these components is sufficiently high. Shortcomings are identified in the existing data on caesium adsorption from liquid sodium onto austenitic steel surfaces. This has enabled the definition of those areas of work which are necessary before the behaviour of fission product caesium in the primary circuit, and the possible requirement of any alleviatory measures, can be predicted with precision and confidence. Experiments are described from which the mechanism of adsorption of caesium onto steel surfaces was elucidated, thereby enabling the prediction of the likely sorption behaviour of fission product caesium on components in the primary circuits of LMFBRs. The potential use of cold-trapping as a means of removing cesium from sodium was also investigated and found to be of no significant value; alternative methods for cesium removal are discussed. The development of methods for decontamination of steelwork which has become contaminated by cesium sorption onto chromium (III) oxides is described, although it is not clear that the levels of contamination which would arise by this mechanism under normal LMFBR operating conditions would necessitate such treatment. (ERA citation 13:033545)