ALARA Programs & Occupational Dose Trend in Wolsong NPP

1. ALARA Programs & Occupational Dose Trend in Wolsong NPP Korea Hydro & Nuclear Power Co., Ltd Wolsong Nuclear Power Plant Unit 3&4

2. Contents • Introduction of Wolsong NPP • Brief History of Wolsong NPP • Generation Capacity of Wolsong NPP • History of Korea Regulatory Law • ALARA program improvements in KHNP • ALARA Program before 2000 • ALARA Program after 2000 • Calling ALARA Committee & Making Decision • General Review of ALARA Program • Cases of Improvements • Results of ALARA Program Improvements • Conclusions

3. Brief History of Wolsong • 1975.10: Opening of Wolsong NPP construction office • 1983. 4: Commercial operation of unit #1 • 1997. 6: Commercial operation of unit #2 • 1998. 6: Commercial operation of unit #3 • 1999. 9: Commercial operation of unit #4

4. Generation Capacity of Wolsong • Generation Capacity: Total 2,778 MW

5. History of Korea Regulatory Law • Korea regulatory law in radiation protection • 1958 : Establish the atomic act • 1983 : General revision based on ICRP-9(MPD, MPAD, MPC) • 1994 : Include the concept of “ALARA” • 1996 : Apply the dose limit concept (no quarterly limit) • 1998 : Apply 100mSv/5yr (50mSv/yr maximum) to effective dose limit but 200mSv/5yr until 2002 • 1999 : Require to implement “ALARA” • 2001 : Apply the concept of ALI, DAC

6. ALARA Prog. Improvements in KHNP • Before 2000 : Plant specific ALARA procedure • After 2000. 10 : Standard ALARA procedure

7. ALARA Program before 2000 • ALARA Committee

8. ALARA Program before 2000 • ALARA ImplementationCommittee

9. ALARA Program after 2000 • Organization ofALARA Committee

10. ALARA Program after 2000 • Responsibility of ALARA Committee • General reviews & approval of ALARA program • RP Policy, Annual Target, Long-term ALARA strategy etc • If expected dose for work is above 200 man-mSv • Review & approve radiation protection optimization plan • Review ALARA results after work if actual doseexceeded by 25% more than expected dose • Review & approve radiation safety control plan during O/H periods • Reviews & approval of optimization plan for radiation protection when requested by chairman

11. ALARA Program after 2000 • Organization of ALARA Implementation Committee

12. ALARA Program after 2000 • Responsibility of ALARA Implementation Commit. • If expected dose for work is above 70~200 man-mSv • Review & approve radiation protection optimization planning • Review ALARA results after work if actual doseexceeded by 25% more than expected dose • Review & approve radiation safety control plan for following workplace • If airborne tritium concentration exceeds 10DAC • If expected dose exceeds 10 man-mSv • Review & approval of optimization plan for radiation protection when requested by chairman

13. Call ALARA Commit.& Make Decision • Minimum 50% of the committee membership must be attended • Issued meeting agenda must be agreed by two-thirds of the attendee • Urgent items & imperative cases can be decided in writing by the committee members without the committee meeting

14. ALARA Documentation

15. Reviews of ALARA Program Any Works Expected Dose 10 ~ 70 man-mSv Expected Dose 70 ~ 200 man-mSv Expected Dose over 200 man-mSv Expected dose under 10 man-mSv Use general RWP - Use RWP - Evaluate expected dose every work steps Work group makes & submits to rad. section - expected dose sheet - ALARA check list Work group makes & submits to rad. section - expected dose sheet - ALARA check list Perform works Perform works Open ALARA Implementation committee Review & approve - expected dose sheet - ALARA check list Open ALARA committee Review & approve - expected dose sheet - ALARA check list Perform works Perform works A B

16. Reviews of ALARA Program A B Review after works Review after work If actual dose exceeds 25% of expected dose If actual dose exceeds 25% of expected dose Open ALARA Implementation committee Review & discuss & apply - dose reduction method to hereafter works Open ALARA committee Review & discuss & apply - dose reduction method to hereafter works

17. Cases of Improvements • High internal exposure dose (IED) in Wolsong NPP • Internal exposure dose of PHWR is higher than that of PWR • Furthermore, IED reaches up to 40% of EED in the beginning of operation • Internal exposure is mainly caused by airborne tritium The Comparison of Occupational Dose

18. Cases of Improvements • The Improvement of the Respirator using Ice Cubes • Tritium removal media: replace vermiculate and paper filter by ice cubes • Year of development: 1992 • Components: canister, half face mask, rubber hose • Ice cube mass: 670g/canister • Tritium removal efficiency: above 95% within 2 hours • Improvements • The prevention of solid rad-waste generation • The respiration became fresher and less stifling • Easy-to-get and cost-effective tritium removal medium

19. Cases of Improvements • The Development of Movable Tritium Eliminator • Application • D2O leak from moderator and coolant system • Spills from equipment failure • Maintenance for the systems or facilities including tritium • Purpose • Preventing diffusion of airborne tritium • Reducing internal exposure of workers • Tritium removal mechanism • Adsorption of airborne tritium into water

20. Cases of Improvements • The Other Efforts for IED Reduction • Use of temporary ventilation fan and duct • Use of portable air tent • Improvement of D2O collection tools • Development of dryer used for decontamination paper

21. Results of ALARA program • Diminishment of internal exposure dose • Internal exposure dose of PHWR has been diminished • Portion of IED have decreased to half of previous’ • Result of continuous efforts to reduce airborne tritium Occupational dose for Wolsong NPP1 Occupational dose for Wolsong NNP2

22. Results of ALARA program • Decrease in Exposure Dose • Annual dose has not increased (but no. of units increased) • Average dose per person & unit have been diminished Annual dose & no. of operating units Annual Avg. Dose per unit & person

23. Annual radiation exposure dose per PHWR plant

24. Results of ALARA program • Diminishment of Over-exposure Workers • No. of over-exposure workers exceeded 20mSv/yearhas increased before 1990. • There was no over-exposure workers for last 7 years Status of over-exposure workers

25. Remark: 1) was happened during in-core detector motor repair work at Kori #2 NPP. Total dose was 52.09mSv per person.

26. Results of ALARA program • Tendency in Exposure Dose • Annual dose has not increased (but no. of NPP increased) • Average dose per person & unit have been diminished • Concentrate radiation control & ALARA activity during O/H Exposure dose for all NPPs Exposure dose for PHWR

27. Conclusions • Atomic law in Korea request actual ALARA implementation • First time, management had a duty to ensure doses were ALARA • KHNP developed the standard ALARA program • Apply lower dose limits & organize stronger members • Successful achievement in dose reduction • Annual total dose has not increased • No. of over-exposure workers has been diminished until 1999 & there was no over-exposure worker till now

28. Thank you very much for your attention