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Preliminary Post-closure Safety Assessment of Disposal Options for Disused Sealed Radioactive Source

폐밀봉선원 처분방식별 폐쇄후 예비안전성평가

  • Received : 2016.05.24
  • Accepted : 2016.07.15
  • Published : 2016.08.28

Abstract

Disused Sealed Radioactive Sources (DSRSs) are stored temporally in the centralized storage facility of Korea Radioactive Waste Agency (KORAD) and planned to be disposed in the low- and intermediate-level radioactive waste (LILW) disposal facility in Gyeongju city. In this study, preliminary post-closure safety assessment was performed for DSRSs in order to draw up an optimum disposal plan. Two types of disposal options were considered, i.e. engineered vault type disposal and rock cavern type disposal which were planned to be constructed and operated respectively in LILW disposal facility in Gyeongju city. Assessment end-point was individual effective dose of critical group and calculated by using GoldSim code. In normal scenario, the maximum dose was estimated to be approximately $1{\times}10^{-7}mSv/yr$ for both disposal options. It meant that both options had sufficient safety margin when compared with regulatory limit (0.1 mSv/yr). Otherwise, in well scenario, the maximum dose exceeded regulatory limit of 1 mSv/yr in engineered vault type disposal and the exposure dose was mainly contributed by $^{226}Ra$, $^{210}Pb$ (daughter nuclide of $^{226}Ra$) and $^{237}Np$ (daughter nuclide of $^{241}Am$). For rock cavern type disposal, even though the peak dose satisfied regulatory limit, the exposure doses by $^{14}C$ and $^{237}Np$ were relatively high above 10% of regulatory limit. Therefore, it is necessary to exclude $^{14}C$, $^{226}Ra$ and $^{241}Am$ for two type of disposal options and additional management such as long-term storage and development of disposal container for those radionuclides should be performed before permanent disposal for conservative safety and security.

국내에서 발생한 폐밀봉선원은 현재 한국원자력환경공단 폐기시설에 임시 보관 중에 있으며 향후 중 저준위 방사성 폐기물 처분시설에 처분될 예정이다. 본 연구에서는 폐밀봉선원의 최적 처분방안 수립에 앞서 폐밀봉선원 처분시 폐쇄후 예비안전성평가를 수행하였다. 폐밀봉선원이 표층처분시설 또는 동굴처분시설에 처분되는 것으로 가정하였으며, GoldSim 전산코드를 사용하여 결정집단의 개인 피폭선량을 계산하였다. 평가결과 정상 시나리오시 최대 피폭선량은 두 가지 처분방식에 대해 약 $1{\times}10^{-7}mSv/yr$으로 나타났으며 이는 규제치인 0.1 mSv/yr에 대비하여 장기적으로 충분한 안전성을 확보할 수 있는 것으로 판단된다. 우물시나리오 시 최대 피폭선량은 표층처분시설에서 규제치인 1 mSv/yr를 초과하였으며 이는 $^{226}Ra$, $^{210}Pb$($^{226}Ra$의 딸핵종) 및 $^{237}Np$($^{241}Am$의 딸핵종)에 기인한 것으로 확인되었다. 동굴처분시설의 경우, 모든 핵종의 최대 피폭선량이 법적 규제치를 만족하나 $^{14}C$$^{237}Np$($^{241}Am$의 딸핵종)에 의한 피폭선량이 규제치 대비 10%를 초과하는 상대적으로 높은 값을 나타내는 것으로 확인되었다. 처분시설 폐쇄후 주민의 피폭선량은 반드시 법적 규제치 이하로 유지되어야 하므로 규제치를 초과 또는 이에 근접한 피폭선량을 유발하는 핵종인 $^{14}C$, $^{226}Ra$$^{241}Am$를 각 처분방식에서 제한할 필요가 있으며 안전한 영구 처분을 위한 처분전 관리가 요구된다.

Acknowledgement

Supported by : 한국에너지기술평가원(KETEP)

References

  1. Andrews, A. (2006) Radioactive Waste Streams: Waste Classification for Disposal, CRS Report for Congress, RL32163.
  2. FNC Technology Co., Ltd. (2015) Characteristic Analysis of Disused Sealed Radioactive Sources in Korea, Ministry of Trade, Industry and Energy.
  3. GIMS(National Groundwater Information Management and Service Center), (2016) (https://www.gims.go.kr/new/contents/sub01/InternalAmount.aspx)
  4. GoldSim Technology Group. (2014) GoldSim Contaminant Transport Module User's Guide, Version 6.4.
  5. IAEA(International Atomic Energy Agency). (2004) Safety Assessment Methodologies for Near Surface Disposal Facilities, v.2.
  6. IAEA(International Atomic Energy Agency). (2011) BOSS: Borehole Disposal of Disused Sealed Sources - A Technical Manual, IAEA-TECDOC-1644.
  7. Jung, K.I., Jeong, M.S. and Park, J.B. (2015) Performance Assessment of Low- and Intermediate-Level Radioactive Waste Disposal Facility in Korea by Using Complementary Indicator: Case Study with Radionuclide Flux, JNFCWT, v.13(1), p.73-86.
  8. KHNP(Korea Hydro & Nuclear Power Co., Ltd). (2008) Low and Intermediate Level Waste Safety Analysis Report.
  9. KINS(Korea Institute of Nuclear Safety). (2014) Verification and Complementation of INDAC, KINS/HR-1357.
  10. KORAD(Korea Radioactive Waste Agency), (2015) Disposal Facility of Very Low Level Radioactive Waste Revision - Preliminary Safety Analysis Report.
  11. NSSC(Nuclear Safety and Security Commission). (2014a) Regulation on Classification of Radioactive Waste and Criteria of Exempt Waste, Notice No. 2014-3.
  12. NSSC(Nuclear Safety and Security Commission). (2014b) Criteria on Prevention of the Radiological hazard for Low and Intermediate Level radioactive Waste Disposal Facility, Notice No. 2014-56.
  13. OECD/NEA(OECD-Nuclear Energy Agency). (2013) Radioactive Waste Management and Decommissioning in Sweden, (https://www.oecd-nea.org/rwm/profiles)
  14. Park, J.W., Chang, K. and Kim, C.L. (2001) Important Radionuclides and Their Sensitivity for Groundwater Pathway of a Hypothetical Near-surface Disposal Facility, J. of the Korean Nuclear Society, v.33(2), p.156-165.
  15. Park, C.K., Lee, J.K., Lee, Y.M., Ko, N.Y. and Jeong, J.T. (2012) Production and Application of Domestic Input Data for Safety Assessment of Disposal, J. of the Korean Radioactive Waste Society, v.10(3), p.161-170. https://doi.org/10.7733/jkrws.2012.10.3.161
  16. Park, J.B., Kim, H.J. and Lee, D.H. (2014) Preparation and Management of the Input Data for the Safety Assessment of Low- and Intermediate-level Radioactive Waste Disposal Facility in Korea, J. of Nuclear Fuel Cycle and Waste Technology, v.12(4), p.345-361. https://doi.org/10.7733/jnfcwt.2014.12.4.345
  17. Reid, R.C., J.M. Prausnitz and B.E. Poling. (1987) The Properties of Gases and Liquids, 4th Edition, McGraw-Hill, Inc., TP242.R4.
  18. Sobolev, I.A., Ojovan, M.I. and Karlina, O.K. (2001) Management of Spent Radiation Sources at Regional Facilities "RADON" in Russian Federation, Proceedings of WM'01 Conference.