Material balance evaluation is an important measure to determine whether or not nuclear material is diverted. A prototype code to evaluate material balance has been developed for uranium fuel fabrication facility. However, it is difficult to analyze the code’s functionality and performance because the utilization of real facility data related to material balance evaluation is very limited. It is also restricted to deliberately implement various abnormal situations based on real facility data, such as nuclear diversion condition. In this study, process flow simulator of uranium fuel fabrication facility has been developed to produce various process data required for material balance evaluation. The process flow simulator was developed on the basis of the Simulink-SimEvents framework of the MathWorks. This framework is suitable for batch-based process modeling like uranium fuel fabrication facility. It dynamically simulates the movement of nuclear material according to the time function and provides process data such as nuclear material amount at inputs, outputs, and inventories required for Material Unaccounted For (MUF) and MUF uncertainty calculation. The process flow simulator code provides these data to the material balance evaluation code. And then the material balance evaluation code calculates MUF and MUF uncertainty to evaluate whether or not nuclear material is diverted. The process flow simulator code can simulate the movement of nuclear material for any abnormal situation which is difficult to implement with real process data. This code is expected to contribute to checking and improving the functionality and performance of the prototype code of material balance evaluation by simulating process data for various operation scenarios.

The Republic of Korea is implementing safeguards for domestic nuclear facilities through cooperation with the IAEA. But it is not to evaluate the material balance for the material unaccounted for, MUF in the bulk handling facility. Although the development of a material balance evaluation program is underway, there are no related regulations. The State Regulatory Authority, SRA is performing material balance evaluation, MBE on the facility based on the design information and material balance results of the facility. However, it is not possible to directly derive measurement uncertainty for the facility’s measurement equipment, which is an important variable of MBE. To solve this problem, it is trying to derive a method suitable for the domestic environment by investigating the some measurement uncertainty estimation methods and analyzing characteristics of them. In this study, the traditional measurement uncertainty estimation method, GUM method and GUM-S1 method were studied and the advantages and disadvantages were analyzed. Due to the problems mentioned above, the uncertainty quantification technique currently being used cannot be applied to the evaluation of the domestic material balance. Therefore, we are tying to apply them to the evaluation the domestic material balance through the above three methods or a combination of them appropriately. Through this continuing study, it is expected that it will be possible to present a plan to derive measurement uncertainty optimized for the domestic MBE environment.

수은은 인체독성과 생물농축성 그리고 대기를 통한 장거리 이동성이 크기 때문에 국제적으로 관리가 필요한 화학물질로 인식되어 왔다. 이에 따라 유엔환경계획(UNEP) 집행이사회에서는 2013년 “수은에 관한 미나마타협약”을 채택하였다. 미나마타협약은 국제적으로 수은사용 및 배출을 저감하는 것이며, 이를 위해 모니터링, 배출원 관리, 원자재 및 제품관리, 폐기물 처리, 노출저감, 기술개발 등 6개 주요 분야별 관리방안을 마련하도록 요구하고 있다. 본 연구에서는 국내 폐형광등 재활용처리시설에 처리방식에 따라 처리공정별 수은 농도변화를 측정하여 공정단계별 수은 물질수지를 분석하였다. 처리방식으로 건식과 습식시설을 각각 선정하여 현장에서 공정단계별 입자상과 기체상 수은 농도, 유량을 측정하거나 시료를 일정시간 동안 3회 채취하여 분석하였다. 또한 직관형 형광등 무게 당 투입 갯수를 확인하였다. 형광등 투입구, 파쇄장치, 건식 및 습식 수은 처리공정, 대기방지시설 등에서 분진, 유리, 비철, 활성탄 등 26개 시료를 채취하고, 수은농도를 측정하여 물질수지를 계산하였다. 연구 결과, 폐형광등 재활용시설로 입고되는 직관형 폐형광등은 박스 당 무게는 약 40-45 kg이고, 형광등 개수는 약 240개 정도이었다. 일부 환형, 일체형 형광등이 처리시설 투입구로 투입되지 않도록 미리 제거하였고, 처리과정에서 발생한 폐기물 중 수은 함량농도를 측정한 결과, 분진, 슬러지, 폐활성탄 및 폐수에서 높게 검출되었다.

It is noted that the red tides and the oxygen-deficient water mass are extensively developed in Masan Bay during summer. The nutrients mass balance was calculated in Masan Bay, using the three-dimensional numerical hydrodynamic model and the material cycle model. The material cycle model was calibrated with the data obtained on the field of the study area in June 1993. The nutrients mass balance calculated by the combination of the residual currents and material cycle model results showed nutrients of surface and middle levels to be transported from the inner part to the outer part of Masan Bay, and nutrients of bottom level to be transported from outer part to inner part of Masan Bay. The uptake rate of DIN in the box A1(surface level of inner part) was found to be 337.5㎎/㎥ ·day, the largest value in all 9 boxes and that of DIP was found to be 18.6㎎/㎥·day in box A1, and the regeneration rate of DIN was found to be 78.2㎎/㎥· day in the box A3(bottom level of inner part), and that of DIP was found to be 18.6㎎/㎥· day in box A1. The regenerations of DIN and DIP in the water column of the entire Bay were found to be 7.66ton/day and 760㎏/day, respectively. And the releases of DIN and DIP from the sediments of the entire Bay were found to be 2.86ton/day and 634㎏/ day, respectively. The regeneration rate was 2.5 times as high as the release rate in DIN, and 1.2 times in DIP. The results of mass balance calculation showed not only the nutrients released from the sediments but the nutrients regenerated in water column to be important in the control and management of water quality in Masan Bay.