Abstract
In the United Kingdom, most intermediate level radioactive waste is being packaged in grade 316L stainless steel containers of various sizes. There is a need to ensure that the containers maintain their integrity during storage for a period that may extend for several decades. It is therefore important to have methods available for monitoring the condition of such packages so that at the end of the storage period the containers are in a form which is suitable for safe storage, transport, handling and potential disposal. A prototype container, the 4 Metre Box, which is fabricated in grade 304L stainless steel, has been used to gain experience in applying condition monitoring and corrosion monitoring techniques. The programme involved two main themes: characterising the environmental conditions (air temperature, surface temperature, relative humidity, time of wetness, surface chloride) and monitoring any changes in the condition of the box (surface strain, visual inspection, potential of reinforcement in concrete liner, dye penetrant). Atmospheric corrosion probes and corrosion coupons were also employed. This paper presents the results acquired during a five-year monitoring period and demonstrates the importance of environmental conditions, surface treatment and surface cleanliness in ensuring good corrosion resistance of stainless steel radioactive waste containers during storage.
