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

Introduction of Wolsong NPP Introduction of Wolsong NPP  Brief History of Wolsong NPP  Generation Capacity of Wolsong NPP History of Korea Regulatory Law History of Korea Regulatory Law ALARA program improvements in KHNP 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 Results of ALARA Program Improvements Conclusions Conclusions Contents

Brief History of Wolsong : Opening of Wolsong NPP construction office : Commercial operation of unit # : Commercial operation of unit # : Commercial operation of unit # : 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

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

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

ALARA Program before 2000 ALARA Implementation Committee PWRPHWR Organization Radiation safety Section senior manager ALARA staff Radiation protection sect. manager Work planner and supervisor Radiation safety section senior manager Radiation protection sect. 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 100~250man-mSv

ALARA Program after 2000 Organization 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 Responsibility of ALARA Committee

ALARA Program after 2000 Organization of ALARA Implementation Committee

 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 ALARA Program after 2000 Responsibility of ALARA Implementation Commit.

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 Call ALARA Commit.& Make Decision Call ALARA Commit. & Make Decision

ALARA Documentation 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

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

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

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 Cases of Improvements The Comparison of Occupational Dose

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  D 2 O 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 D 2 O collection tools  Development of dryer used for decontamination paper Cases of Improvements

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 Results of ALARA program Annual dose & no. of operating units Annual Avg. Dose per unit & person

Annual radiation exposure dose per PHWR plant

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

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 O/HTotal 20001,8119,58311, ,1818,57110, ,6716,6449, ,7567,53210, ,62710,39813, ,6079,32311,93078 Results of ALARA program Year Dose (man-mSv) % of O/H Dose Normal Operation O/HTotal ,4632, ,8982, ,6612, ,1372,0273, ,4853, ,2073,01673 Exposure dose for all NPPs Exposure dose for PHWR

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 Conclusions

Thank you very much for your attention