PWR oxide characterisation/surface Finish improvement and development of decontamination processes for gas and water cooled reactors

Status of nuclear power and decontamination studies in the UK is described. It is reported that laboratory scale decontamination tests were carried out on contaminated Magnox boiler fin specimens using formic acid alone and in combination with formaldehyde. With a 1.5% solution of formic acid alone at 23 deg. C, decontamination was 90% complete after 48 hours, further decontamination to give an overall DF of 17 took place when the temperature was raised to 50 deg. C. Tests were also carried out with Windscale AGR specimens in 5% formic acid and 60 deg. C. On sections of the superheater, DFs of > 100 were achieved for the dominant 60C and 134Cs/137Cs isotopes. The reagent was, however, less effective on steels with a higher chromium content such as the Refrasil insulation package. Experimental work by Nuclear Electric on water reactor decontamination techniques was actually ceased. A number of techniques for improvement of surface finish are being studied, including electropolishing, mechanical polishing, pre-oxidation and application of surface coatings. Experiments have confirmed that electropolished surfaces show radioactivity uptake a factor of four to five lower than on mechanical ground or machined surfaces 9 refs, 1 tab