Overall optimization of radioactive waste processing and disposal for problematic waste management

Nakagawa, Akinori ; Sasaki, Toshiki ; Sakamoto, Yoshiaki 

Japan Atomic Energy Agency (JAEA) has stored radioactive wastes generated from R&D activities related to nuclear science and technology. A part of these wastes contains compressed wastes without prior radiological, chemical or physical characterization assessed, as well as mixed wastes containing lead and mercury with little information about its contents. Pre-treatment and radiological characterization efforts for such problematic wastes are very time consuming and costly. In order to optimize the processing and disposal of the problematic wastes, a method to balance the processing work and disposal facility robustness was studied. Work analysis of waste processing showed bottleneck processes, such as radiological characterization and segregation of hazardous materials and combustibles. Establishment of a conservative scaling factor method and non-destructive gamma-ray measurement enable easier radiological characterization. Hazardous materials will be identified using records and nondestructive inspection. The waste identified as hazardous will be unpacked and segregated. Based on preliminary survey of about 1,000 drums, only 10 % of stored drums contain hazardous materials and need segregation. Regarding the separation of combustibles, total volume of the combustibles will be evaluated using nondestructive inspection technique such as high-energy X-ray CT and the waste that does not comply with the waste acceptance criteria should be mixed with waste containing a small amount of combustibles in order to satisfy the waste acceptance criteria on a disposal facility average. It was estimated that segregation throughput of compressed waste should be increased about 5 times more than conventional method by applying the countermeasures.