Development of Analysis Method for Plutonium amount and Burn up by Measurement of Xenon Isotopic Ratio in Dissolver Off-Gas at Reprocessing Facility

None

岡野 正紀 ; 久野 剛彦 ; 高橋 一朗*; Charlton, W. S.*; Wells, C. A.*; Hemberger, P. H.*

Okano, Masanori; Kuno, Takehiko; Takahashi, Ichiro*; Charlton, W. S.*; Wells, C. A.*; Hemberger, P. H.*

再処理施設における使用済燃料中のプルトニウム量及び燃焼度をオフガス中のキセノン同位体組成比との相関から求める測定技術を検討した。東海再処理施設にてBWR使用済燃料処理時の溶解オフガス(6サンプル)を採取し、ガスクロマトグラフ質量分析計でキセノン同位体組成を求めた後、ロスアラモス国立研究所で開発された解析コード(NOVA)を用いて使用済燃料中のプルトニウム量及び燃焼度を算出した。溶解オフガス中の3つのキセノン同位体組成比(Xe/Xe,Xe,Xe/Xe)から評価した処理燃料の燃焼度は、申告された燃焼度と94%の信頼度で一致していた。一方、プルトニウム量については、申告値と-0.9%4.7%の差で一致した。

We have studied a new technique to evaluate Pu amount in the spent fuel from Xe isotopic ratio in off-gas in reprocessing facility, which is related to burn up. The technique is applicable for both burn up credit to achieve efficient criticality safety control and a new measurement method for safeguards inspection. Six batches of dissolver off-gas (DOG) at spent fuel dissolution process were sampled with press pump from the main stack in Tokai Reprocessing Plant (TRP) during BWR fuel (approx. 30GWD/MTU) reprocessing campaign. Xe isotopic ratio was determined with Gas Chromatography-Quadrupole Mass Spectrometer (GC-QMS). Burn up and Pu amount were evaluated with NOVA, Noble Gas Environmental Monitoring Application code, developed by Los Alamos National Laboratory. Agreement between declared burn up and inferred burn up evaluated by Xe isotopic measurements and NOVA was at the 94% confidence level. We found that Pu amount in spent fuel evaluated by developed method agreed with declared value calculated by ORIGEN code in the range of -0.9% to 4.7%.