CORROSION CONTROL in nuclear fuel reprocessing

The chemical reprocessing of irradiated nuclear fuel involves the handling of highly radioactive and often hot or highly corrosive solutions, usually containing nitric acid. This demands plant constructed to a high standard of integrity from suitably resistant materials. The difficulty of carrying out maintenance or repair of active plant which fails due to corrosion means that an adequate corrosion allowance, based on reliable data, must be included at the design stage. The data on which to base the allowance are gathered from small‐and rig‐scale laboratory experiments where coupons or vessels, tubing, etc fabricated from the candidate material(s) are exposed to a simulated process environment. This is backed up whenever possible by corrosion data accruing from the operation of existing plants and by exposure of specimens to the actual plant environment followed by metallographic examination. The constructional materials most commonly used in reprocessing plants are austenitic grades of stainless steel along with smaller quantities of refractory metals like titanium. This, unsurprisingly, is in line with current practices in the nitric acid manufacturing industry.