Central Research Institute of Electric Power Industry (CRIEPI) Nuclear Development

1. 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 – Nakata K. a)*, Hironaga M.a), Minato D.a), Kino K.b), Sakashita A.c), Takao K.d), Sakakihara T.e) Central Research Institute of Electric Power Industry (CRIEPI) Nuclear Development Mitsubishi Heavy Indstries Tokyo Institute of Technology Shikoku Electric Power Co. INC.

2. Background C-14: Important radionuclide for RW disposal C-14 : long half life (5730y) may control exposure dose in safety assessment Understanding chemical form of C-14 from NPPis required for predicting environmental behavior of C-14 C-14 produced from NPP • Produced from BWR mainly gas (CO2) form • Produced from PWR C-14 found in solid phase (CRUD) • ion-exchange resinmay be the origin of C in the solid phase * * As presented in previous presentation Issues • The possibility that resin can be an origin of solid C has not been evidenced • There is little information chemical form of solid C and mechanism for formation of solid C Obtaining the information about chemical form and formation mechanism of solid C in PWR is needed for safety assessment of RW disposal

3. Objective Objective of this study ( As a first step of resolution of problems） Obtaining information about alteration of resin in PWR (alteration of resin with high temperature and irradiation of γ-rays origin of solid C in CRUD is discussed information about chemical form and formation mechanism of solid C What we do in this study Alteration of resin with high temperature: heating experiment---(1) Resins were heated in simulated atmosphere of coolant in PWR Alteration of resin by irradiation with γ-rays---(2) γ-rays were irradiated to resins after heating Comparison of CRUD and altered resins---(3)

4. (1) Heating experiment– experimental conditions Experimental Conditions: Simulate the primary coolant of PWR Measurement The outline of experimental system (Solid phase) 　・FT-IR　・TG-DTA　・C/H 　・NMR　・Raman (Liquid phase) 　・TOC ・IC ・GC (gas phase) 　・GC Will be explained in detail

5. (1) Heating experiment– Results (FT-IR and TG) TOC and IC Concentration of SO42- increased significantly Sulfo groups detached from resin After heating for 24h TG The sample weight decreased sharply at 400 to 450 oC Similar behavior to Polystyrene After heating for 96h The sample weight deceased gradually above 500 oC Similar behavior to Graphite Structure of resin changed with increase of time

6. (1) Heating experiment– Summary of Results – -Sulfo group detached -H detached from the structure -Structure similar to amorphous C -Structure similar to polystyrene was remained

7. (1) Heating experiment－ Information from 13CNMR－ Aromatic rings Alkyl group (2) (3) (1) (2) (3) (1) After heating for 24h (1) Changed → Sulfo group detached (2) Not changed→Maintain CH2 (3) Not changed→Maintain aromatic rings 13Ｃ-ＮＭＲ spectra of resin before and heating After heating for 96h • Changed → Change of CH2 • (2) Not changed → Maintain aromatic rings

8. (1)Alteration of resin by high temperature Before heating After heating for 24h After heating for 96h Detachment of sulfo group -H from CH2 detached -CH may be involved in condensation reaction -Aromatic rings were remained The structure similar to polystyrene remained The structure similar to amorphous carbon may be formed with aromatic rings and C from CH2 Insoluble C is formed from resin by heating

9. (2)Alteration of resin by irradiation Resin after heating was micronized and irradiated with γ-rays (318kgy) ---micronized resins were suspended in the solution by stirring during the irradiation Peaks generated by irradiation → Related to –OH and/or -COOH Irradiation of γ-rays generate OHand /or COOH groups on the surface of resin OH and COOH may be involved into condensation reactions → accelerate condensation reactions FT-IR Spectra after heating and heating +irradiation

10. (3) Comparison of CRUD and altered resins • FT-IR measurement CRUD and heated + irradiated resin is similar (presentation I) • TG-14C measurement Resins caught with filter soon Contribute to (1) • Structure similar to polystyrene • Little C-14 is contained (1) (2) Resins stayed in coolant long time Contribute to (2) • Structure similar to Amorphous C • Significant amount of C-14 contained (1) Sharp decrease in weight, however little C-14 was detected (2) Even heated with 1000oC, most of C-14 remained in solid

11. Summary The change in resin with high temperature Detachment of H from alkyl → Condensation reactions → Aromatic rings remain Detachment of SO3 → Structure like polystyrene Amorphous C is formed The change in resin with γ–rays irradiation OH and/or COOH may be formed with γ–rays irradiation OH and COOH may be involved in condensation reactions, if it is heated Comparison of CRUD and altered resin • FT-IR spectrum was similar each other • TG-14C measurement for CRUD and be explained by the results of heating experiment • “Insoluble C” is formed from resin with high temp and irradiation • It is possible that a part of CRUD comes from the resin

12. Acknowledgements We would like to appreciate • For helpful and insightful advices Prof. Ishigure (Univ. of Tokyo) Prof. Ikeda, Associate Prof. Tsukahara (Tokyo Institute of Technology) • For help in irradiation experiment Mr. Yoda (Tokyo Institute of Technology)