• 한국지하수토양환경학회지:지하수토양환경
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• 제22권4호
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• pp.33-48
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• 2017

An optimum disposal plan of disused sealed radioactive sources (DSRSs) should be established to ensure long-term disposal safety at the low- and intermediate-level radioactive waste (LILW) disposal facility in Gyeongju. In this study, an optimum disposal system was suggested and preliminary post-closure safety assessment was performed. The DSRSs disposal system was composed of a rock cavern and near surface disposal facilities at the Gyeongju LILW disposal facility. The assessment was conducted using GoldSim program, and probabilistic assessment and sensitivity analysis were implemented to evaluate the uncertainties in the input parameters of natural barriers. Deterministic and probabilistic calculations indicated that the maximum dose was below the regulatory limits ($0.1mSvyr^{-1}$ for the normal scenario, $1mSvyr^{-1}$ for the well scenario). It was concluded that the DSRSs disposal system would maintain environmental safety over a long-time. Moreover, the partition coefficient of Np in host rock, Darcy velocity in host rock, and density of the host rock were the most sensitive parameters in predicting exposure dose in the safety assessment.

• Nuclear Engineering and Technology
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• 제55권2호
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• pp.530-545
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• 2023

As an alternative to conventional management options for a lot of concrete waste from decommissioning of nuclear power plants, a set of scenarios for controlled recycling of decommissioning concrete waste as engineered barriers of a radioactive waste repository was proposed, and a comprehensive safety assessment model and framework covering both pre-and post-closure phases was newly developed. The new methodology was applied to a reference vault-type repository, and the ratios of derived concentration limits to unconditional clearance levels of eighteen radionuclides for controlled recycling were provided for three sets of dose criteria (0.01, 1, and 20 mSv/y for the pre-closure and 0.01 mSv/y for the post-closure phases). It turns out that decommissioning concrete waste whose concentration is much higher than the unconditional clearance level can be recycled even when the dose criterion 0.01 mSv/y is applied. Moreover, a case study on ABWR bio-shield shows that the fraction of recyclable concrete waste increases significantly by increasing the dose criterion for the radiation worker in the pre-closure phase or the duration of storage prior to recycling. The results of this study are expected to contribute to demonstrating the feasibility of controlled recycling of a lot of decommissioning concrete waste within nuclear sectors.

• Nuclear Engineering and Technology
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• 제55권11호
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• pp.4083-4095
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• 2023

Currently, various research institutes in Korea are conducting research to develop a safety case for deep geological repository for high-level radioactive waste (HLW). In the past, low and intermediate-level waste (LILW) was approved by a regulatory body by performing a post-closure safety assessment, but HLW has different disposal characteristics and safety objectives are different. Therefore, in the case of HLW, safety assessment should be performed based on these changed conditions, and specific procedures are also under development. In this paper, the regulatory status of prior research institutes, feature, event and process (FEP) and scenario development cases were investigated for well-organized FEP and scenario development methodologies. In addition, through the results of these surveys, the requirements and procedures necessary for the FEP and scenario development stage during the safety assessment of repository for HLW were presented. These review results are expected to be used to identify the overall status of previous studies in conducting post-closure risk assessment for HLW repository, starting with identifying regulatory requirements, the most basic element.

• Nuclear Engineering and Technology
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• 제35권2호
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• pp.108-120
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• 2003

In assessing the long term post closure radiological safety assessment of a potential HLW repository in Korea, three categories of uncertainties exist. The first one is the scenario uncertainty where series of different natural events are translated into written statements. The second one is the modeling uncertatinty where different mathematical models are applied for an identical scenario. The last one is the data uncertainty which can be expressed in terms of probabilistic density functions. In this analysis, three different scenarios are seleceted; a small well scenario, a radiolysis scenario, and a naturally discharged scenario. The MASCOT-K and the AMBER, probabilistic safety assessment codes based on connection of sub-modules and a compartment theory respectively, are applied to assess annual individual doses for a generic biosphere. Results illustrate that for a given scenario, predictions from two different codes fairly match well each other But the discrepancies for the different scenarios are significant. However, total doses are still well below the guideline of 2 mRem/yr. Detailed analyses with model and data uncertainties are underway to further assure the safety of a Korean reference dispsoal concept.

• 방사성폐기물학회지
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• 제6권4호
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• pp.329-346
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• 2008

중저준위 방사성폐기물의 영구처분을 위하여 건설되는 월성원자력환경관리센터의 1단계 폐쇄후 안전성평가에 대하여 기술하였다. 처분시설의 건설운영허가를 위하여 작성된 안전성평가에 대하여 평가개요, 처분시설의 폐쇄개념, 처분부지에 대한 지하수 유동특성을 이용하여 평가를 위한 시나리오의 개발과정과 도출된 평가대상 시나리오에 대한 개념을 기술하였다. 폐쇄후 안전성평가 모델링을 위한 평가도구, 입력인자와 개별 시나리오에 대한 핵종누출 모델링, 기체발생 및 기체이동 모델링, 인간침입 모델링과 생태계 모델링에 대하여 기술하였다. 처분시설의 폐쇄후 안전성 평가시나리오에 대하여 국내 규제치를 만족하는 것으로 평가되었으며 향후 처분시설 안전성에 대한 불확실성 저감과 신뢰성 증진을 위한 노력을 지속적으로 수행할 예정이다.

• 방사성폐기물학회지
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• 제11권4호
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• pp.311-324
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• 2013

우리나라 중저준위 방사성폐기물 최종 처분시설인 월성원자력환경관리센터의 폐쇄 후 안전평가 컴퓨터 프로그램의 신뢰성 확보를 위해 MASCOT와 검증프로그램으로 SAFE-ROCK와 GOLDSIM을 선정하여 정상시나리오에 대하여 안전평가를 수행하였다. 각 프로그램의 장단점을 비교/분석하였으며, 각 프로그램 별 구획 간의 선량 및 누출량을 평가하였다. 그 중 방사성핵종 $^{129}I$와 $^3H$가 MASCOT와 SAFE-ROCK 프로그램에서는 비슷한 경향을 보여주었지만, GOLDSIM 프로그램에서는 상이한 결과를 나타냈다. 이는 각 프로그램의 근계지역 내 핵종이동방정식의 해석과정의 차이와 개별 프로그램의 한계로 인해 다른 결과값을 보여주는 것으로 분석되었다. GOLDSIM 프로그램의 경우, 선원항 구획에서 초기 핵종누출량은 time-scale에 민감하게 반응한다는 사실도 확인할 수 있었다. 안전평가 프로그램은 처분환경에서 발생하는 핵종거동 및 이동에 대한 실제현상을 예측하기 위해 모델링을 거치지만, 전산프로그램의 특성과 실제현상에 대한 데이터가 제한적이므로 결과에 차이가 발생하게 된다. 이러한 차이점은 다양한 프로그램을 이용한 결과와 상호비교를 통해 알아내며 그 원인을 지속적으로 분석하는 연구개발과정을 필요로 하고 있다.

• Nuclear Engineering and Technology
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• 제34권4호
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• pp.406-414
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• 2002

In TSPA of long-term post closure radiological safety on permanent disposal of HLW in Korea, appropriate management of input and output data through QA is necessary. The robust QA system is developed using the T2R3 principles applicable for five major steps in R&D＇s. The proposed system is implemented in the web-based system so that all participants in TSPA are able to access the system. In addition, the internet based input database for TSPA is developed. Currently data from literature surveys, domestic laboratory and field experiments as well as expert elicitation are applied for TSPA.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2002년도 추계학술발표회요약집
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• pp.326.1-326
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• 2002

• Nuclear Engineering and Technology
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• 제42권1호
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• pp.37-46
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• 2010

The development of advanced nuclear fuel cycle(ANFC) technology is essential to meet the national mission for energy independence via a nuclear option in Korea. The action target is to develop environmentally friendly, cost-effective measures to reduce the burden of long term disposal. The proper scenarios regarding potential radionuclide release from a repository have been developed in this study based on the advanced korean Reference Disposal System(A-KRS). To predict safety for the various scenarios, a new assessment code based on the GoldSim software has also been developed. Deterministic analysis indicates an environmental benefit from the ANFC as long as the solid waster from the ANFC act as a proper barrier.

• Journal of Radiation Protection and Research
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• 제29권1호
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• pp.41-48
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• 2004

A safety assessment code, called SAGE (Safety Assessment Groundwater Evaluation), has been developed to describe post-closure radionuclide releases and potential radiological doses for low- and intermediate-level radioactive waste (LILW) disposal in an engineered vault facility in Korea. The conceptual model implemented in the code is focused on the release of radionuclide from a gradually degrading engineered barrier system to an underlying unsaturated zone, thence to a saturated groundwater zone. The radionuclide transport equations are solved by spatially discretizing the disposal system into a series of compartments. Mass transfer between compartments is by diffusion/dispersion and advection. In all compartments, radionuclides ate decayed either as a single-member chain or as multi-member chains. The biosphere is represented as a set of steady-state, radionuclide-specific pathway dose conversion factors that are multiplied by the appropriate release rate from the far field for each pathway. The code has the capability to treat input parameters either deterministically or probabilistically. Parameter input is achieved through a user-friendly Graphical User Interface. An application is presented, which is compared against safety assessment results from the other computer codes, to benchmark the reliability of system-level conceptual modeling of the code.