照射後試験施設から発生した廃棄物に対する放射能濃度評価方法の検討

Study on the evaluation methodology of the radioactivity concentration in low-level radioactive wastes generated from post irradiation examination facility

水飼 秋菜; 原賀 智子   ; 石森 健一郎 ; 亀尾 裕 

Mitsukai, Akina; Haraga, Tomoko; Ishimori, Kenichiro; Kameo, Yutaka

日本原子力研究開発機構の研究施設から発生する研究施設等廃棄物は、将来的に浅地中に埋設処分する予定であり、埋設処分を開始するまでに、廃棄体の放射能濃度を評価する方法を構築する必要がある。原子力科学研究所バックエンド技術部では、照射後試験施設であるホットラボから発生した廃棄物をモデルに、放射性核種(H-3, C-14, Cl-36, Co-60, Ni-63, Sr-90, Mo-93, Nb-94, Tc-99, Ag-108m, Sn-126, I-129, Cs-137, Eu-152, Eu-154, U-233+234, U-238, Pu-238, Pu-239+240, Pu-241, Am-241, Am-243, Cm-244)を対象とした放射化学分析に基づく放射能濃度評価方法の検討を行った。検討の結果、Sr-90, I-129, Eu-154, U-233+234, Pu-238, Pu-239+240, Am-241, Cm-244に対してスケーリングファクタ法が適用できる見込みが得られ、H-3, C-14, Cl-36, Ni-63, Mo-93, Nb-94, Tc-99, Ag-108m, Sn-126, Eu-152, U-238, Pu-241及びAm-243に対して平均放射能濃度法が適用できる見込みが得られた。また、Ni-63, Tc-99, Eu-152及びU-238は追加データが得られれば、スケーリングファクタ法が適用できる可能性がある。

In the future, radioactive waste which generated from nuclear research facilities in Japan Atomic Energy Agency are planning to be buried for the near surface disposal. It is necessary to establish the method to evaluate the radioactivity concentrations of the radioactive wastes. In this work, we studied the evaluation method of radioactivity concentration based on radiochemical analysis data (H-3, C-14, Cl-36, Co-60, Ni-63, Sr-90, Mo-93, Nb-94, Tc-99, Ag-108m, Sn-126, I-129, Cs-137, Eu-152, Eu-154, U-233+234, U-238, Pu-238, Pu-239+240, Pu-241, Am-241, Am-243, Cm-244) which was generated from research facility Hot Laboratory. As a result of examining the application of the scaling factor method, the correlation with Key-nuclide in some nuclides which are Sr-90, I-129, Eu-154, U-233+234, Pu-238, Pu-239+240, Am-241, Cm-244 confirmed by the correlation coefficient and t-test. In the present radiochemical analysis data, the mean activity concentration method can be applied to all nuclides which could not be applied to the scaling factor method H-3, C-14, Cl-36, Ni-63, Mo-93, Nb-94, Tc-99, Ag-108m, Sn-126, Eu-152, U-238, Pu-241 and Am-243. Ni-63, Tc-99, Eu-152 and U-238 could be applied to the scaling factor method with getting several additional data, this study will be continued to review for the practical evaluation method.