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속중성자 다중도 측정 기반 특정핵물질 계량 시스템 전산모사

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Alternative Title
Monte Carlo Simulation for Special Nuclear Material Accounting System using Fast Neutron Multiplicity Counting
Abstract
One of the main tasks for implementing nuclear safety measures is nuclear material accounting management. The development of technology for nuclear disarmament verification is the focus of numerous studies, but the study is concentrated on using it to verify the pyroprocessing system in Korea. The new accounting technique combines a thermal neutron multiplication-based accounting method based on the Pu/Cm ratio with a fast neutron energy multiplication method. However, there is a limitation in detecting thermal neutrons using 3He tubes.
While alternative detector are being developed internationally due to the 3He depletion problem, fast neutron multiplicity detection method is being developed to replace the function of the current accounting system and improve performance. For 239Pu or 241Pu, the spontaneous fission rate is significantly lower, so neutrons can be detected by irradiation of exogenous sources. However, to develop a system that estimates the effective mass of 240Pu with a high spontaneous fission rate due to low economic feasibility and increased complexity for system construction, an optimized design was carried out through computer simulation. Mathematical modeling previously proposed for application to a fast neutron detection system was verified.
In this study, using MCNPX-PoliMi, the characteristics of neutrons caused by spontaneous fission and induced fission of 240Pu were observed by assuming a 4 π type 20 mm thick stilbene detector. Through this, it was verified that the point model to be applied to the fast neutron detection system was valid. For the development of a compact system, an optimized arrangement was selected among system designs using six stilbene. It was confirmed that the decrease the source-to-detector distance in the ring arrangement and the cubic arrangement, the higher the efficiency. The effective mass in the range of 5 g to 100 g of 240Pu samples was derived and compared in each design. Through this, it was confirmed that the maximum value of the relative error of the estimated mass was lower than that of the ring arrangement when the stilbene detector achieved a cubic arrangement. In addition, a method using parameters was additionally performed to compare the accuracy of estimating the effective mass of the sample. When comparing the one-parameter assay and the two-parameter assay, it was confirmed that the accuracy was improved, especially for trace samples, when the two-parameter assay was applied.
Therefore it was confirmed that the parameter analysis method using the information of reference samples among various methods was the most accurate in developing a specific nuclear material metering management system. Based on this, a neutron multiplicity accounting system using fast neutron detection is developed to measure specific nuclear materials, and the estimated effective mass of 240Pu can be used as a relative criterion for determining spent nuclear fuel and weapon-grade Pu.
Author(s)
현수연
Issued Date
2023
Awarded Date
2023-02
Type
Dissertation
URI
https://dcoll.jejunu.ac.kr/common/orgView/000000011107
Alternative Author(s)
Hyeon Suyeon
Affiliation
제주대학교 대학원
Department
대학원 에너지화학공학전공
Advisor
정만희
Table Of Contents
표 목차 i
그림 목차 ii
ABSTRACT iv
I. 서론 1
제1절 연구배경 및 필요성 1
1. 원자력 안전조치를 위한 기술 1
1.1 원자력 안전조치 1
1.2 핵물질 계량 기술에 대한 국내외 현황 2
2. 핵분열성 물질의 물리적 특성 7
2.1 자발적 핵분열 7
2.2 유도핵분열 9
2.3 (α, n) 반응 9
3. 중성자 다중도 개요 11
제2절 연구범위 13
II. 특정핵물질 계량을 위한 중성자 계측 14
제1절 산란 기반의 속중성자 검출기 14
1. 유기 섬광검출기 : 스틸벤 14
2. 신호 파형 구별법을 이용한 중성자/감마 분리 15
제2절 속중성자 다중도 계수 기술 17
1. Rossi-α 분포 17
2. 포인트 모델 (Point Kinetic Equation) 19
3. 매개변수 분석 방법 23
3.1 단일 매개변수 분석 방법 23
3.2 이중 매개변수 분석 방법 23
III. 특정핵물질 계량 시스템 전산모사 방법 및 결과 25
제1절 전산모사 및 분석 절차 25
1. MCNPX-PoliMi를 이용한 특정핵물질 유효질량 도출 개요 25
제2절 분석 및 유효질량 도출을 위한 방법 26
1. MCNP Data 분석 26
2. Rossi-α 분포 도출 및 게이트 선정 28
제3절 전산모사 결과 30
1. 수학적 모델링 유효성 검증 30
2. 특정핵물질 계량 시스템 개발을 위한 최적의 디자인 평가 32
2.1 링 형태 (시료와 검출기 간격: 9 cm)의 특정 핵물질 계량 시스템 33
2.2 링 형태 (시료와 검출기 간격: 4.5 cm)의 특정 핵물질 계량 시스템 35
2.3 큐빅 형태 (시료와 검출기 간격: 3.5 cm)의 특정 핵물질 계량 시스템 37
3. 매개변수 분석 방법 적용 결과 39
3.1 단일 매개변수 분석 방법 39
3.2 이중 매개변수 분석 방법 42
IV. 결론 44
제1절 연구의 요약 44
제2절 향후 연구계획 45
참고문헌 47
부록 01. MCNP Input 파일 예시 51
부록 02. Cross-talk 보정 전 결과 53
Degree
Master
Publisher
제주대학교 대학원
Citation
현수연. (2023). 속중성자 다중도 측정 기반 특정핵물질 계량 시스템 전산모사.
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Faculty of Applied Energy System > Energy and Chemical Engineering
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