• 방사성폐기물학회지
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• 제11권4호
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• pp.271-280
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• 2013

원자력 발전소와 연구시설의 해체 시 다량의 오염된 방사성 콘크리트 폐기물이 발생한다. 현재 국내에는 연구로 1, 2호기의 해체와 제염사업이 진행 중이며, 약 800여 드럼 (200 L)의 콘크리트 폐기물이 발생하였다. 이들 방사성 콘크리트 폐기물은 최종처분을 위해 200 L 드럼에 덩어리 크기의 콘크리트를 채우고, 시멘트 모르타르 형태로 제조한 입자상 폐기물로 빈 공간을 채우며 혼용 고정화 및 안정화하는 일련의 과정이 필요하다. 이에 본 연구에서는 콘크리트 폐기물, 물, 시멘트의 최적의 혼합비율을 찾고, 처분장 폐기물 인수기준에 준하기 위한 고화체의 특성을 평가하였다. 모르타르 유동도, 고화체 압축강도, 침출에 대한 안정성, 열 저항성 등의 인자에 따라 평가한 결과, 콘크리트 폐기물, 물, 시멘트의 배합비 75:15:10wt%에서 평가인자 기준에 도달하였으며, 콘크리트 폐기물 75%에 미분말 콘크리트 폐기물을 최대 40wt%까지 포함시켜 시멘트 고화체를 제조한 경우에도 압축강도를 만족하였다. 입자의 충진 밀도의 증가로 scale-up실험에서는 75:10:15wt%의 배합비에서 작업도 및 압축강도 범위를 만족하였다.

• Journal of Radiation Protection and Research
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• 제45권4호
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• pp.178-186
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• 2020

Background: Reactor pressure vessel (RV) with internals (RVI) are activated structures by neutron irradiation and volume contaminated wastes. Thus, to develop safe and optimized disposal plan for them at a disposal site, it is important to perform exact activation calculation and evaluate the dose rate on the surface of casks which contain cut-off pieces. Materials and Methods: RV and RVI are subjected to neutron activation calculation via Monte Carlo methodology with MCNP6 and ORIGEN-S program-neutron flux, isotopic specific activity, and gamma spectrum calculation on each component of RV and RVI, and dose rate evaluation with MCNP6. Results and Discussion: Through neutron activation analysis, dose rate is evaluated for the casks containing cut-off pieces produced from decommissioned RV and RVI. For RV cut-off ones, the highest value of dose rate on the surface of cask is 6.97 × 10-1 mSv/hr and 2 m from it is 3.03 × 10-2 mSv/hr. For RVI cut-off ones, on the surface of it is 0.166 × 10-1 mSv/hr and 2 m from it is 1.04 × 10-1 mSv/hr. Dose rates for various RV and RVI cut-off pieces distributed lower than the limit except the one of 2 m from the cask surface of RVI. It needs to adjust contents in cask which carries highly radioactive components in order to decrease thickness of cask. Conclusion: Two types of casks are considered in this paper: box type for very-low-level waste (VLLW) as well as low-level waste (LLW) and cylinder type for intermediate-level waste (ILW). The results will contribute to the development of optimal loading plans for RV and RVI cut-off pieces during the decommissioning of nuclear power plant that can be used to prepare radioactive waste disposal plans for the different types of wastes-ILW, LLW, and VLLW.

• Nuclear Engineering and Technology
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• 제55권1호
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• pp.190-200
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• 2023

As the field of application of in-situ gamma spectroscopy is diversified, proficiency is required for consistent and accurate analysis. In this study, a program was developed to virtually create gamma energy spectra of artificial nuclides, which are difficult to obtain through actual measurements, for training. The virtual spectrum was created by synthesizing the spectra of the background radiation obtained through actual measurement and the theoretical spectra of the artificial radionuclides obtained by a Monte Carlo simulation. Since the theoretical spectrum can only be obtained for a given geometrical structure, representative major geometries for in-situ measurement (ground surface, concrete wall, radioactive waste drum) and the detectors (HPGe, NaI(Tl), LaBr₃(Ce)) were predetermined. Generated virtual spectra were verified in terms of validity and harmonization by gamma spectrometry and energy calibration. As a result, it was confirmed that the energy calibration results including the peaks of the measured spectrum and the peaks of the theoretical spectrum showed differences of less than 1 keV from the actual energies, and that the calculated radioactivity showed a difference within 20% from the actual inputted radioactivity. The verified data were assembled into a database and a program that can generate a virtual spectrum of desired condition was developed.