국내 경수로 및 중수로 해체원전의 부지 개방을 위한 잔류방사능 유도농도 도출 및 비교분석 연구 = A Study on Calculation and Comparative Analysis of Derived Concentration Guideline Levels for Site Release of Decommissioned PWRs and PHWRs in Korea

다국어 초록 (Multilingual Abstract)

A Study on Calculation and Comparative Analysis of Derived Concentration Guideline Levels for Site Release of Decommissioned PWRs and PHWRs in Korea Jinho Son Advisor : Prof. Kong, Tae Young Department of Nuclear Engineering Graduate School of Chosun University Currently, there are two permanently shut down nuclear power plants (NPPs) in Korea: Kori Unit 1, which is a pressurized water reactor (PWR), and Wolsong Unit 1, which is a pressurized heavy water reactor (PHWR). The decommissioning of an NPP involves the removal of buildings and structures and, ultimately, the release of the site for unrestricted use. To release the site for unrestricted use, an assessment of the radiation dose received by individuals using the site must be conducted. According to the Korea Nuclear Safety and Security Commission Notice No. 2021-11, for the purpose of unrestricted site release, the annual radiation dose standard for individuals using the site after decommissioning is set at 0.1 mSv. Conducting such radiation dose assessments for every NPP decommissioning involves practical difficulties. An alternative to this dose assessment is the use of derived concentration guideline levels (DCGLs), which can be used to demonstrate that the dose is within the acceptable standard. Therefore, this study compared the DCGLs for Kori Unit 1 and Wolsong Unit 1. Estimating the DCGLs requires various factors. In particular, there are different scenarios based on the purpose of the site use by individuals, with the residential farmer or the industrial worker scenarios. They are typically considered the most conservative scenarios for evaluation. In these scenarios, the main factors for radiation exposure include the consumption of food produced on the contaminated site or working on a site that has been contaminated by radioactive materials. In this study, the food consumption rates of adults in Korea were surveyed to estimate the DCGLs. The radioactive isotopes expected to remain at Kori unit 1 were estimated using data from the Rancho Seco & Connecticut Yankee NPPs, which have similar decommissioning conditions. For Wolsong Unit 1, measurement data from the replaced pressure tube samples were used, and additional radioactive isotopes were included by assuming concrete activation. Additionally, the site's meteorological, hydrogeological, physical, and chemical factors were investigated to match the site characteristics for the DCGL calculation. The DCGLs showed some differences between the PWR and PHWR. The expected residual final radioactive isotopes for Wolsong Unit 1 included additional isotopes not found in the list of residual radioactive isotopes for Kori Unit 1, specifically 36Cl, 133Ba, 182Hf, 192mIr. On the other hand, the final predicted radionuclides remaining at the site of Kori Unit 1 include 237Np, which is not observed in Wolsong Unit 1. It was found that the DCGLs and dose to individuals were affected by each site's hydrological and geological characteristics. In general, for the common isotopes expected to remain in both decommissioned sites, it was found that the DCGLs differed by approximately 2-3%. However, the DCGLs of 90Sr were found to be approximately 22.38% higher in Wolsong Unit 1 compared to Kori Unit 1. Even for the same radioactive isotopes, different doses to individuals have resulted depending on the specific characteristics of each site. Furthermore, radiation exposure primarily occurs due to gamma-emitting radionuclides remaining on the contaminated site rather than internal exposure from ingestion. This indicates the need to focus on the decontamination of gamma-emitting radionuclides during the remediation of decommissioned sites. It was also found that for some radioactive isotopes, significant differences in doses and DCGLs can arise depending on the distribution coefficient of the soil. Therefore, it was determined that when decommissioning an NPP, soil samples should be collected from each site, and their physical and chemical properties should be accurately measured using tracer isotopes to conduct a dose assessment for people using the site after decommissioning. Additionally, hydrogeological factors of the site can also influence the transport of radioactive isotopes, so it is advisable to apply actual measurement data for these factors.

목차 (Table of Contents)

• 1. 서 론 1
• 1.1 연구 배경 1
• 1.1.1 원자력발전소 및 해체시장 현황 2
• 1.1.1.1 국내 원자력발전소 현황 2
• 1.1.1.2 해외 원자력발전소 현황 4
• 1.1.1.3 원자력발전소 해체 현황 및 전망 6
• 1.1.2 원자력발전소 해체절차 10
• 1.2 연구 목적 14
• 1.2.1 국내외 해체 원자력발전소 부지복원 사례 14
• 1.2.1.1 국내 해체 원자력발전소 부지복원 사례 14
• 1.2.1.2 해외 해체 원자력발전소 부지복원 사례 14
• 1.2.2 해체 원자력발전소 부지복원 관련 법령 15
• 1.2.2.1 국내 해체 원자력발전소 부지복원 관계 법령 15
• 1.2.2.2 해외 해체 원자력발전소 부지복원 관계 법령 16
• 1.2.2.3 기타 국가 원자력발전소 부지복원 관계 법령 16
• 1.2.3 잔류방사능 유도농도 도출의 필요성 17
• 2. 연구방법 19
• 2.1 잔류방사능 유도농도 도출을 위한 분석코드 19
• 2.1.1 잔류방사능 유도농도 도출을 위한 분석코드 19
• 2.1.2 RESRAD 20
• 2.2 입력인자 분석 21
• 2.2.1 국내 원자력발전소 부지 특성 21
• 2.3 피폭경로 24
• 2.3.1 외부피폭 24
• 2.3.1.1 외부피폭 시나리오 25
• 2.3.2 내부피폭 26
• 2.3.2.1 내부피폭 시나리오 27
• 2.4 노형별 잔류 예상 방사성핵종 및 선량환산인자 비교 30
• 2.4.1 경수로형 원자력발전소의 잔류 예상 방사성핵종 31
• 2.4.2 중수로형 원자력발전소의 잔류 예상 방사성핵종 34
• 2.4.3 외부피폭 선량환산인자 비교 36
• 2.4.4 내부피폭 선량환산인자 비교 39
• 3. 잔류방사능 유도농도 도출을 위한 입력인자 42
• 3.1 잔류방사능 유도농도 평가 대상 원전부지의 특성 42
• 3.1.1 고리 1호기의 기상 및 수문학적 특성 42
• 3.1.2 월성 1호기의 기상 및 수문학적 특성 45
• 3.2 잔류방사능 유도농도 도출을 위한 확률론적 평가 방법 46
• 3.2.1 입력 매개변수의 분류 및 순위 46
• 3.2.2 결정론적 매개변수 선정 52
• 3.2.3 확률론적 매개변수 선정 57
• 4. 잔류방사능 유도농도 도출 61
• 4.1 고리 1호기의 잔류방사능 유도농도 도출 61
• 4.2 월성 1호기의 잔류방사능 유도농도 도출 70
• 4.3 경수로형 및 중수로형 원전의 잔류방사능 유도농도 비교 78
• 5. 결론 84
• 참고문헌 87