Investigation of C-14 in the CRUD collected on the coolant filter for safety disposal of radioactive waste containing C-
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.271
Investigation of C-14 in the CRUD collected on the coolant filter for safety disposal of radioactive waste containing C-14 (II) – Chemical alteration of ion exchange resin under simulated condition in primary coolant of PWR Kotaro Nakata1, Michihiko Hironaga1, Daisuke Minato1, Kenichiro Kino2, Akira Sakashita3, KoichiroTakao4 and Tetsuro Sakakihara5 1 Central Research Institute of Electric Power Industry, 1646 Abiko, Abikoshi, Chibaken 270-1194, JAPAN.
2
Nuclear Development Corporation, 622-12 Funaishikawa, Tokaimura, Ibarakiken 319-1111, JAPAN.
3
Mitsubishi Heavy Industries, LTD, 16-5, Konan 2-Choume, Minato-ku Tokyo 108-8215, JAPAN.
4
Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, JAPAN.
5
Shikoku Electric Power Co., INC., 2-5 Marunouchi, Takamatsushi, Kagawaken 760-8573, JAPAN.
ABSTRACT
The formation mechanism and chemical form of insoluble C-14 found in PWR need to be examined in order to predict its environmental behavior after disposal. This study investigates the alteration of ion-exchange resin by heating and irradiation, because past studies indicated the ion-exchange resin may be the origin of insoluble C-14.
Resin was heated at 300 °C in solution with low oxygen content to simulate the environment of PWR coolant. The sulfo group was found to detach within 8 h, and structures similar to polystyrene were remained. This is followed by detachment of H from the alkyl group, condensation reaction, and the formation of amorphous carbon-like structure. After heating for 24 and 96 h, the resin was irradiated by 60Co γ-rays in the solution. The FT-IR and TG measurements after irradiation suggested that OH and COOH groups were formed on the surface of the resin. These functional groups may be involved in reactions that finally form the amorphous carbon.
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In addition, the characteristics of heated and irradiated resin were compared to real insoluble-C (CRUD) sample in PWR (in Appendix).
INTRODUCTION Radiocarbon (C-14) is one of the most important radionuclides to consider for the safe disposal of Low Level Radioactive Wastes, because of its long half-life (5730 years; Mook and Van Der Plicht, 1999) and large inventory (Yim and Caron, 2006; Sakuragi et al., 2016). The formation mechanism and chemical form of insoluble C-14 found in PWR need to be examined in order to predict its environmental behavior after disposal. Previous studies have indicated (1) CRUD (in this study, it is defined as solid phase on fuel rod or captured by the filter in the coolant system including not only metal oxides but also the other solids) obtained on the surface of fuel rod and coolant filter contained a significant amount of C (58 to 95%; Vance et al., 1995) (2) insoluble C incl
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