1. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA- 1 Demonstration of Zinc Injection Technique in Fugen Nuclear Power Station Satoshi MORITA Radiation and Chemistry Management Section Fugen Nuclear Power Station Japan Atomic Energy Agency

2. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -2 Contents  Outline of Fugen nuclear power station  Ｗａｔｅｒ chemistry history in Fugen  Demonstration of Zinc injection technique  Conclusion

3. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -3 Fugen Nuclear Power Station Heavy-water-moderated, boiling light water cooled, pressure tube type reactor 165 MWe [Prototype Advanced Thermal Reactor(ATR)] Pu-U mixed oxide fuel Commercial operation since 1979 Average load factor: ~ 65% Permanent shut down: 2003 Tsuruga. Fukui. JAPAN

4. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -4 Outline of FUGEN Transformer Generator Condenser Sea Sea Water Feed Water Pump Turbine Pump Steam Steam Drum Containment Vessel Recirculatio Pump Pressure Tube Control Rod Heavy Water in the “Calandria” Tank Fuel Heavy Water (Moderator) Light Water (Coolant) Calandria Tank

5. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -5 An Overview of Primary Cooling System

6. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -6 Radiation Dose Rate Rise Mechanism of Reactor Cooling System NuclideHalf-lifeReaction 60 Co5.3 year 59 Co(n,γ) 58 Co72 day 58 Ni (n,p) 59 Fe45 day 58 Fe(n,γ) 54 Mn310 day 54 Fe(n,p) 51 Cr28 day 50 Cr(n,γ)

7. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -7 Dose Rate Reduction by Chemical Decontamination and Zinc Injection

8. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -8 Material integrity –HWC (1984.7 ～ 1985.7 ： experimental HWC) (1985.12 ～ 2003.3 ： HWC) Occupational dose reduction –Chemical decontamination (1989, 1991, 1999, 2000) –Zinc injection (1998.8 ～ 1999.1 : experimental Zn Inj.) (1999.8 ～ 2003.3 :continuous Zn Inj.) Water Chemistry Features of Fugen

9. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -9 Application Timing of Decontamination with Water Chemistry History in Fugen 200 0 30 0 Year Electrical output (MWe) Hydrogen Injection (Nm 3 /h) Zn Conc. in reactor water (ppb) 788084909600 02 828688929498 A-Loop B-Loop Kridecon(EDTA)HOP Decon. A-Loop 10 0 5 System decontamination

10. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -10 Area of Decontamination Steam drum to Turbine Pressure tube Riser tube Lower header Inlet tube Down comer Manifold Recirculation pump(D) Calandria tank Recirculation pump (B) ［ Decontamination on each loop ］ B- LOOP A- LOOP

11. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -11 Dose ｒ ate Change of the Reactor Coolant Recirculation Pump Outlet Pipe

12. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -12 Preparations for Zn Injection in Fugen ・ Confirmation of the retardation effect of radioactivity deposition Short-term Injection Test Zinc Injection Irradiation Test Material Integrity Test Plant test ・ Confirmation of implication for main structural material 1990 ～ 1992 1994 ～ 1997 1998.8 ～ 1999.1 1999.8 ～ ・ Confirmation of stable injection technique ・ Confirmation of Zinc injection effect ・ Confirmation of implication for plant ・ Confirmation of long-term Zinc injection effect

13. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -13 Flow Schematic of Zinc Injection in Fugen

14. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -14 Activity Change During Zinc Injection 1ppb 3ppb 5ppb 7ppb

15. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -15 Long Term Trend of Co-60 Concentration in Reactor Water on HWC and Zinc Injection Electrical output ( MWe ) Hydrogen injection ( Nm 3 /h ) 200 0 40 0 0 10 Zn 2+ concentration ( ppb ) 0 78808284868890929496980002 Year 10 0 3 2 1 Soluble (ionic)Co-60 concentration ( Bq/cm 3 ) Insoluble (crud) Co-60 concentration ( Bq/cm 3 )

16. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -16 Ge Detector/shield Set Against RCP-D Outlet

17. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -17 After Decontamination Co-60 Deposition Coefficient

18. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -18 Long-term Occupational Dose Related Issues Electricity output ( MWe ) H2 Flow rate ( Nm 3 /h ) Zn2+ Conc.in RW ( ppb ) 4 0 6 3 0 2 Normalized doserate of B-Loop ( - ) Occupational dose With normal periodic Maintenance wark ( person-Sv ) 78808284868890929496980002 Year Kuridecon-Decon. HOP-Decon RW* ： Reactor water sampled from the inlet of purification bed Averaged doserate in a ｐｅｒｉｏｄｉｃ mainntenance period Normalized doserate** ＝ Averaged doserate in the 1 st periodic maintenance perriod 200 0 40 0 0 10

19. ISOE Asian Technical Center 2005ALARA Mini-Workshop Fugen Nuclear Power Station, JAEA -19 CONCLUSION The zinc injection after the decontamination effectively suppressed the re-adhesion of Co-60 on the surface of piping and maintained the radiation source state at a low-level ． The occupational exposure dose in 17th inspection period was at the minimum, 1.31 person ・ Sv, through Fugen’s operational period. The dose control measures for a permanent, effective plant were achieved by these water chemistry control technique developments and in this way, effective exposure dose control measures were established.