Design Study of A Spent Fuel Shipping Cask for Korea Nuclear Unit-1

고리 1호기의 기사용 핵연료 집합체 수송용기 설계에 관한 연구

To transport the spent fuel assemblies of Korea Nuclear Unit 1, which is a Westinghouse type two loop pressurized water reactor, it has been found that steel is the most appropriate material for the design of a shipping cask in comparison with lead and depleted uranium. The proposed shipping cask will transport nine fuel assemblies at the same time and is well within the weight limit of transportation by unrestricted rail car. The cask requires 33cm thick steel shield and 27cm thick water region to satisfy the 3 feet apart dose rate limit set forth in 10 CFR 71, and 1.27cm thick steel boron fuel basket to hold the fuel elements inside the cask and control the effective multiplication factor. As a safety analysis, the fuel cladding and centerline temperatures were calculated under the accident condition of complete loss of water coolant, and it was found that the temperature was much lower than the limit of the melting point. k$_{eff}$ was calculated with fresh fuel assemblies, which was found to be well lower than 0.95. For shielding computation, the multipurpose Monte Carlo code MORSE-CG and one dimensional discrete ordinates transport code ANISN were used, and the Monte Carlo codes KENO and MORSE-CG were used for criticality calculation. The radiation source terms were calculated using ORIGEN-79.9.

본 논문에서는 고리 1호기의 기사용 핵연료 집합체를 수송하기 위한 Cask를 설계하였다. 이를 위하여 고리 1호기의 기사용 핵연료 집합체로부터 방출되는 감마선과 중성자를 계산하여 MORSE 및 ANISN전산 코드로써 차폐 계산을 수행하였다. 그 결과, 9개의 집합체를 동시에 수송할 수 있는 Steel Cask가 가장 적합하다는 것을 밝혔다. 이 Steel Cask에 대한 안전성을 평가하기 위하여 연료봉의 중심 온도와 복재온도를 계산하여 핵연료의 용융점보다 훨씬 낮음을 증명하였다. 또한 KENO와 MORSE전산 코드를 사용하여 임계도 계산을 수행하여 미임계 상태임을 증명하였다. 이로써 9개의 기사용 핵연료 집합체를 동시에 수송할 수 있는 Steel Cask를 간단히 설계하였다.