Transactions of the Korean Nuclear Society Spring Meeting Jeju, Korea, May 12-13, 2016 Probabilistic Assessment Method of Turbojet Engine Impact on an Interim Dry Storage Facility Belal Almomani a , Sanghoon Lee b , Hyun Gook Kang a* a Dept. of Nuclear and Quantum Eng., KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Korea b Dept. of Mechanical and Automotive Eng., Keimyung University, Dalgubeol-daero 1095, Dalseo-gu, Daegu, Korea * Corresponding author: hyungook@kaist.ac.kr 1. Introduction In the process of developing an aircraft crash scenario onto an interim dry storage facility, the shield wall of the facility building is considered as a first barrier of protecting the internal spent fuel storage casks. In order to evaluate the aircraft risk model on the interim storage facility, it is important to use a probabilistic safety assessment approach for investigating the probable realistic and severe impact conditions from the aircraft crash. This paper describes an analytical method of structural analysis for an interim storage facility subjected to aircraft jet engine based on a probabilistic approach. This method will be employed in the process of aircraft risk model for the interim storage facilities. 2. Methods and Assumptions The local response mechanism of a concrete shield is initiated with spalling and subsequently can result in penetration, scabbing of the shield material from the back face, and eventual perforation transporting the missile through the shield as illustrated in Fig 1 [1]. Fig. 1. Local response of a shield: (a) penetration and spalling, (b) scabbing, and (c) perforation. The primary local damage effect of interest is an eventual perforation of the shield that the missile fully penetrates and passes through the target since this study concentrates on the safety of the internal storage casks during a direct high-speed impact from a heavy component. The direct impact on the storage casks happens when the initial velocity of the missile is greater than the perforation velocity that is sufficient to fully penetrate the target without exiting. The exit velocity of the missile is called a “residual velocity”. The residual velocity of the perforating missile is an important parameter that could potentially cause casks to be damaged. The engines of an aircraft were considered from many references as the major critical missiles that can result a significant local structural damage. Regardless of other stiff elements on an aircraft, the jet engine is assumed as a potential independent missile normally impacting towards the reinforced concrete wall slab for this study. The analytical formulation of the engine impact and the perforation to find the required thickness of concrete to protect the equipment inside the structure is an enormously complex impact phenomenon. Therefore, all the available formulas describing perforation phenomena are empirical and based on experimental data. In this study, the assessment of structural integrity for the local loading on concrete walls is based on a simplified approach using empirical formulas that were recommended in NEI 07-3 report [2]. 2.1 Perforation mode of damage The term perforation thickness is used especially when the projectiles just passes through the target completely with zero exit velocity. Two empirical formulas have been used to determine the limit state of the perforation depth and to define the concrete wall thickness criteria to protect the storage casks inside the facility. The Modified NDRC (National Defense Research Committee) eq. (1) obtains the penetration depth, and the reduced Degen eq. (2) calculates the wall thickness required to prevent perforation.   =  √ 4 (   1000 ) 1.8 , for      <2 (1)   =   {2.2 (      ) − 0.3 (      ) 2 } , for      < 1.52 (2) where   is the wall thickness to prevent perforation (inches),   is the crushed casing penetration depth (inches),  is the missile weight (Ibs), α c is the reduction factor for penetration and α p is the reduction factor for perforation, K is the concrete penetrability factor defined as 180 (  ) 12 ⁄ ⁄ ,   is the compressive strength of concrete (psi), D is the effective diameter of the engine (inches),   is the original missile velocity (ft/sec). For the missile shape factor N, 0.72 is assigned for flat-nosed, 0.84 for blunt-nosed, 1.00 for spherical end, and 1.14 for very sharp-nosed projectiles.