ウラン加工施設からのクリアランスにおける回収ウランの影響評価

抄録

  Clearance levels for uranium isotopes have been recently authorized in Japan. The measurement of those elements can be disregarded when the nominal of the element (D/C), expressed as (D/C)*, is less than 10⁻³, where D is the specific radioactivity concentration of nuclides, C is the clearance level of nuclides, and (D/C)* is defined as (D/C) divided by the highest value of (D/C)'s in the element constitutions of uranium waste. In this study, the concentration of nuclides in reprocessed uranium was evaluated using ORIGEN2 burnup analyses and the most appropriate decontamination factors for determining the (D/C)* values and their influence on clearance application in the uranium fuel fabrication plant. It was concluded that nuclides other than five isotopes, ²³²U, ²³⁴U, ²³⁵U, ²³⁶U, and ²³⁸U, can be disregarded with regards to clearance application in the uranium fabrication plant, regardless of operation conditions, whether the fuel is fabricated by receiving reprocessed uranium or not.