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Shunsuke HORI, Akira SUZUKI Tokyo Electric Power Company

TEPCO’s Challenges for Occupational Exposure Reduction -Installation of Additional CF in Fukushima Daiichi NPP-. Shunsuke HORI, Akira SUZUKI Tokyo Electric Power Company Nuclear Power Plant Management Department Radiation Protection Group ISOE International ALARA Symposium

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Shunsuke HORI, Akira SUZUKI Tokyo Electric Power Company

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  1. TEPCO’s Challenges for Occupational Exposure Reduction-Installation of Additional CF in Fukushima Daiichi NPP- Shunsuke HORI, Akira SUZUKI Tokyo Electric Power Company Nuclear Power Plant Management DepartmentRadiation Protection Group ISOE International ALARASymposium September 8-9, 2009, Aomori, JAPAN

  2. Profile - Location Electricity sales by the 10 electric utilities

  3. TEPCO’s Nuclear Power Plants Kashiwazaki-Kariwa NPP Fukushima-Daiichi NPP NPP Fukushima-Daini NPP 17 BWRs including 2 ABWRs (total capacity 17,308MWe) - 27% of generation capacity (FY 2008)

  4. Contents • Occupational Exposure in NPP • Measures for Reduction of Collective Dose • Quality of Feed Water after Installation of Additional CF in Fukushima Daiichi Unit 6 • Collective Dose Estimation • Secondary Effects by Reduction of CRUD • Conclusions

  5. Occupational Exposure in NPP (1/2) Collective Dose per Reactor in Nuclear Power Station (BWR) (2006 to 2008 Average)

  6. Occupational Exposure in NPP (2/2) Annual Collective Dose Trend per Plant in Japan

  7. MeasuresforReductionofCollectiveDose(1/4) Measures for Reduction of Collective Dose in PCV Use of Low Cobalt Material(Ⅰ) Reduction of Activated Corrosion Products Control / Removal of CRUD Use of Corrosion-Resistant Material (Ⅰ) Mechanical Decontamination (Ⅲ) Removal of Activated Corrosion Products Oxygen Injection(Ⅱ) Chemical Decontamination (Ⅲ) CF Volume Increase(Ⅱ) Radiation Level Reduction Optimized use of CF,C/D and CUW(Ⅲ) Control of Activated Corrosion Products Attachment Electrochemical Polishing (Ⅰ) Temperature-Controlled Shutdown(Ⅲ) Pre-filming (Ⅰ) Ni/Fe Control (Ⅲ) Change in Piping Design(Geometry / Location) (Ⅱ) Zinc Injection (Ⅲ) Optimization of Shield Permanent Shield (Ⅱ) Temporary Shield (Ⅲ) Improvement of　　（Ⅰ）Material　　（Ⅱ）Equipment or System　　（Ⅲ）Operation

  8. MeasuresforReductionofCollectiveDose(2/4) Reactor Primary System（BWR） Main Steam Line Moisture Separator Generator Feed Water LP-Turbine HP-Turbine Condenser Sea Water PLR RWCU Heater Heater Feed Water Pump Condensate Polisher System Oxygen Injection

  9. MeasuresforReductionofCollectiveDose(3/4) Results of Dose Reduction Measures ① ① Oxygen injection ② Use of low-cobalt material ③ Use of weatherproof steel in component materials for feed water and condensate ④ Control of feed water iron ⑤ CF installation ② ③ ④ ⑤ Annual Dose per Reactor (person-Sv) Fiscal Year

  10. MeasuresforReductionofCollectiveDose(4/4) CF(Condensate Pre-Filter) in Japan (BWR)

  11. Quality of Feed Water Feed Water Iron Concentration Trend after CF Installation (Fukushima Daiichi Unit 6)

  12. Collective Dose Estimation Collective Dose Estimation after additional CF Installation (Fukushima Daiichi Unit 6)

  13. Secondary Effects by Reduction of CRUD

  14. Conclusions • We have successfully reduced the concentration of feed water iron in Fukushima Daiichi Unit 6 by theinstallation of additional CF. • We’ll continue to try to reduce occupational exposures by every possible measures after cost performance evaluations.

  15. Support Documentation(1/5) LPCP-out Iron Concentration Trend after CF Volume Increase (Fukushima Daiichi Unit 6)

  16. Support Documentation(2/5) Injecting Oxygen Into the Feed Water System (Fukushima Daiichi Unit 1) Oxygen-injection installation ppb as Fe 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Cycle The concentration of the insoluble iron in the feedwater.

  17. Support Documentation(3/5) Use of Low Cobalt Material (Fukushima Daiichi Unit 1) Change to low-cobalt material Heating pipes of feedwater heaters Bq/cm3 as Co-60 Cycle The concentration of Co-60 in the reactor water.

  18. Support Documentation(4/5) Use of weatherproof steel ppb as Fe Application of weatherproof steel Cycle The concentration of the insoluble iron in the condensate water

  19. Support Documentation(5/5) Duplication of condensate purification system (Fukushima Daiichi Unit 1) ppb as Fe HFF installation Cycle The concentration of the insoluble iron in the condensate water

  20. MeasuresforReductionofCollectiveDose(2/4) Reactor Primary System（BWR） RPV Tb CUW H/W FWP LPCP CF FW Hx HPCP C/D

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