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

Contents Introduction of Wolsong NPP History of Korea Regulatory Law 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

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

Generation Capacity of Wolsong Generation Capacity: Total 2,778 MW

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

ALARA Prog. Improvements in KHNP Before 2000 : Plant specific ALARA procedure After 2000. 10 : Standard ALARA procedure Previous (before 2000) Present (after 2000) ALARA Committee Expected dose: above 250man-mSv above 200man-mSv Implementation 100~250man-mSv 70~200man-mSv

ALARA Program before 2000 ALARA Committee PWR PHWR Organi -zation Chairman Vice chairman Member Secretary General manager Deputy general manager Plant senior manager Appointed person Radiation safety section senior manager Plant section senior manager QA section senior manager Plant senior manager (sub-contractor) Radiation safety section senior manager Responsibility Review ALARA program Review dose reduction plan for work. If expected dose is above 250man-mSv for work. If expected dose is above

ALARA Program before 2000 ALARA Implementation Committee PWR PHWR Organization Radiation safety Section senior manager ALARA staff Radiation protection sect. manager Work planner and supervisor Radiation safety section senior manager Maintenance section manager Work supervisor Responsibility Review & approve dose reduction plan for work expected dose 100~250man-mSv Review & approve ALARA sheet for work expected dose

ALARA Program after 2000 Organization of ALARA Committee

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 dose exceeded 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

ALARA Program after 2000 Organization of ALARA Implementation Committee

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 dose exceeded 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

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

ALARA Documentation Radiation work plan Retention periods 3 years Kinds of documents Retention periods Radiation work plan (Over 10 under 70 man mSv) Doc. reviewed by ALARA Implementation committee (Over 70 under 200 man mSv) Doc. reviewed by ALARA committee (Over 200 man mSv) 3 years 5 years Plant life time

Reviews of ALARA Program Any Works Expected dose under 10 man-mSv Expected Dose 10 ~ 70 man-mSv Expected Dose 70 ~ 200 man-mSv Expected Dose over 200 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

Reviews of ALARA Program 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

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

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

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

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

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

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

Annual radiation exposure dose per PHWR plant

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

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

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 Year Dose (man-mSv) % of O/H Dose Normal Operation Total 2000 1,811 9,583 11,394 84 2001 2,181 8,571 10,752 80 2002 2,671 6,644 9,315 71 2003 2,756 7,532 10,288 73 2004 2,627 10,398 13,025 2005 2,607 9,323 11,930 78 Year Dose (man-mSv) % of O/H Dose Normal Operation Total 2000 750 1,463 2,213 66 2001 779 1,898 2,677 71 2002 877 1,661 2,538 65 2003 1,137 2,027 3,164 64 2004 845 2,485 3,330 75 2005 809 2,207 3,016 73 Exposure dose for all NPPs Exposure dose for PHWR

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

Thank you very much for your attention This a picture taken during the cherry blossom season in April. These are briefs of KEPCO & WNPD. Thank you, very much minister for your attention. Thank you very much for your attention