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Belal Almomani,김태용,장윤석 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.4
The importance of ensuring the inherent safety and security has been more emphasized in recent yearsto demonstrate the integrity of nuclear facilities under external human-induced events (e.g. aircraftcrashes). This work suggests a simulation methodology to effectively evaluate the impact of a commercialaircraft engine onto a dry storage facility. A full-scale engine model was developed and verified by Rieraforce-time history analysis. A reinforced concrete (RC) structure of a dry storage facility was alsodeveloped and material behavior of concrete was incorporated using three constitutive models namely:Continuous Surface Cap, Winfrith, and Karagozian & Case for comparison. Strain-based erosion limits forconcrete were suitably defined and the local responses were then compared and analyzed with empiricalformulas according to variations in impact velocity. The proposed methodology reasonably predictedsuch local damage modes of RC structure from the engine missile, and the analysis results agreed wellwith the calculations of empirical formulas. This research is expected to be helpful in reviewing the drystorage facility design and in the probabilistic risk assessment considering diverse impact scenarios.
Probabilistic risk assessment of aircraft impact on a spent nuclear fuel dry storage
Almomani, Belal,Lee, Sanghoon,Jang, Dongchan,Kang, Hyun Gook Elsevier 2017 Nuclear engineering and design Vol.311 No.-
<P><B>Abstract</B></P> <P>This paper proposes a systematic risk evaluation framework for one of the most significant impact events on an interim dry storage facility, an aircraft crash, by using a probabilistic approach. A realistic case study that includes a specific cask model and selected impact conditions is performed to demonstrate the practical applicability of the proposed framework. An event tree analysis of an occurred aircraft crash that defines a set of impact conditions and storage cask response is constructed. The Monte-Carlo simulation is employed for the probabilistic approach in consideration of sources of uncertainty associated with the impact loads onto the internal storage casks. The parameters for representing uncertainties that are managed probabilistically include the aircraft impact velocity, the compressive strength of the reinforced concrete wall, the missile shape factor, and the facility wall thickness. Failure probabilities of the impacted wall and a single storage cask under direct mechanical impact load caused by the aircraft crash are estimated. A finite element analysis is applied to simulate the postulated direct engine impact load onto the cask body, and a source term analysis for associated releases of radioactive materials as well as an off-site consequence analysis are performed. Finally, conditional risk contribution calculations are represented by an event tree model. Case study results indicate that no severe risk is presented, as the radiological consequences do not exceed regulatory exposure limits to the public. This risk model can be used with any other representative detailed parameters and reference design concepts for other comparable direct or indirect impact conditions onto the cask body, which may provide an efficient way to investigate storage facility capacity to withstand an aircraft crash and thereby protect public health.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new risk assessment frame is proposed for aircraft impact into an interim dry storage. </LI> <LI> It uses event tree analysis, response-structural analysis, consequence analysis, and Monte Carlo simulation. </LI> <LI> A case study of the proposed procedure is presented to illustrate the methodology’s application. </LI> </UL> </P>
Almomani, Belal,Kim, Seyeon,Jang, Dongchan,Lee, Sanghoon Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.5
A parametric study of several parameters relevant to design safety on the spent nuclear fuel (SNF) rod response under a drop accident is presented. In the view of the complexity of interactions between the independent safety-related parameters, a factorial design of experiment is employed as an efficient method to investigate the main effects and the interactions between them. A detailed single full-length fuel rod is used with consideration of post-irradiated fuel conditions under horizontal and vertical free-drops onto an unyielding surface using finite-element analysis. Critical drop heights and critical g-loads that yield the threshold plastic strain in the cladding are numerically estimated to evaluate the fuel rod structural resistance to impact load. The combinatory effects of four uncertain parameters (pellet-cladding interfacial bonding, material properties, spacer grid stiffness, rod internal pressure) and the interactions between them on the fuel rod response are investigated. The principal finding of this research showed that the effects of above-mentioned parameters on the load-carrying capacity of fuel rod are significantly different. This study could help to prioritize the importance of data in managing and studying the structural integrity of the SNF.
Belal Almomani,장동찬,이상훈,강현국 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.2
Using a probabilistic safety assessment, a risk evaluation framework for an aircraft crashinto an interim spent fuel storage facility is presented. Damage evaluation of a detailedgeneric cask model in a simplified building structure under an aircraft impact is discussedthrough a numerical structural analysis and an analytical fragility assessment. Sequences ofthe impact scenario are shown in a developed event tree, with uncertainties considered inthe impact analysis and failure probabilities calculated. To evaluate the influence of parametersrelevant to design safety, risks are estimated for three specification levels of caskand storage facility structures. The proposed assessment procedure includes the determinationof the loading parameters, reference impact scenario, structural response analyses offacility walls, cask containment, and fuel assemblies, and a radiological consequenceanalysis with doseerisk estimation. The risk results for the proposed scenario in this studyare expected to be small relative to those of design basis accidents for best-estimated conservativevalues. The importance of this framework is seen in its flexibility to evaluate thecapability of the facility to withstand an aircraft impact and in its ability to anticipate potentialrealistic risks; the framework also provides insight into epistemic uncertainty in theavailable data and into the sensitivity of the design parameters for future research.
Belal Almomani,SaeHanSol Kang,Yoon-Suk Chang,Jae-soo Noh 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.7
To maintain a safe management of spent nuclear fuel (SNF), it is necessary to understand the characteristics of fuel cladding associated with material degradation and failure criteria. This study aims to establish strain-based failure criteria for Zircaloy-4 cladding from uniaxial tensile tests considering hydride distribution. An investigation of the hydrogen effect on mechanical properties of cladding was presented using the design of experiment method. The applicability of the proposed criteria for transverse tearing failure mode was demonstrated in energy-limited events using finite element analysis. The failure probabilities of cladding were estimated for normal transportation and hypothetical accident conditions. The proposed failure criteria provide an advancement on the existing studies that only implemented transverse tearing failure mode by considering hydride distribution. This effort could be particularly valuable to the regulatory institutes and those utility planners who are evaluating structural integrity concerning the critical characteristics of SNF for potential licensing considerations.
A software tool for integrated risk assessment of spent fuel transportation and storage
Mirae Yun,Robby Christian,김보경,Belal Almomani,Jaehyun Ham,이상훈,강현국 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.4
When temporary spent fuel storage pools at nuclear power plants reach their capacity limit, the spentfuel must be moved to an alternative storage facility. However, radioactive materials must be handledand stored carefully to avoid severe consequences to the environment. In this study, the risks of threepotential accident scenarios (i.e., maritime transportation, an aircraft crashing into an interim storagefacility, and on-site transportation) associated with the spent fuel transportation process were analyzedusing a probabilistic approach. For each scenario, the probabilities and the consequences were calculatedseparately to assess the risks: the probabilities were calculated using existing data and statistical models,and the consequences were calculated using computation models. Risk assessment software wasdeveloped to conveniently integrate the three scenarios. The risks were analyzed using the developedsoftware according to the shipment route, building characteristics, and spent fuel handling environment. As a result of the risk analysis with varying accident conditions, transportation and storage strategieswith relatively low risk were developed for regulators and licensees. The focus of this study was the riskassessment methodology; however, the applied model and input data have some uncertainties. Furtherresearch to reduce these uncertainties will improve the accuracy of this model.