Accepted Manuscripts

Guest Editorial  
Mohammad Pourgol-Mohammad and Leon Cizelj
ASME J. Risk Uncertainty Part B   doi: 10.1115/1.4038467
ASME Risk Journal Preface-Editorial Note SI020B: Special Issue on Uncertainty Quantification in Multiscale Systems for Nuclear Safety and Security
TOPICS: Safety, Risk, Uncertainty quantification, Security
Danial Faghihi, Subhasis Sarkar, Mehdi Naderi, Jon R. Rankin, Lloyd Hackel and Nagaraja Iyyer
ASME J. Risk Uncertainty Part B   doi: 10.1115/1.4038372
In the present study, a general probabilistic design framework is developed for cyclic fatigue life prediction of metallic hardware using methods that address uncer- tainty in experimental data and computational model. The methodology involves (i) fatigue test data conducted on coupons of Ti6Al4V material (ii) continuum damage mechanics based material constitutive models to simulate cyclic fatigue behavior of material (iii) variance-based global sensitivity analysis (iv) Bayesian framework for model calibration and uncertainty quantification and (v) computa- tional life prediction and probabilistic design decision making under uncertainty. The outcomes of computational analyses using the experimental data prove the feasibility of the probabilistic design methods for model calibration in presence of incomplete and noisy data. Moreover, using probabilistic design methods result in assessment of reliability of fatigue life predicted by computational models.
TOPICS: Design methodology, Fatigue life, Risk, Design, Calibration, Decision making, Performance, Fatigue, Reliability, Hardware, Constitutive equations, Uncertainty quantification, Damage mechanics, Fatigue testing, Sensitivity analysis, Uncertainty
Hai Zhong and Mijia Yang
ASME J. Risk Uncertainty Part B   doi: 10.1115/1.4038340
Prestress applied on bridges affects the dynamic interaction between bridges and vehicles traveling over them. In this paper, the prestressed bridge is modeled as a beam subjected to eccentric prestress force at the two ends, and a half-vehicle model with 4 degrees of freedom is used to represent the vehicle passing the bridge. A new bridge-vehicle interaction model considering the effect of prestress with eccentricity is developed through the principle of virtual work. The correctness and accuracy of the model are validated with literature results. Based on the developed model, numerical simulations have been conducted using the Newmark's ß method to study the effects of vehicle speed, eccentricity and amplitude of the prestress, and presence of multiple vehicles. It is shown that prestress has an important effect on the maximum vertical acceleration of vehicles, which may provide a good index for detecting the change of prestress. It is also interesting to find that the later-entering vehicle on the prestressed bridge will largely reduce the maximum vertical acceleration of the vehicle ahead of it.
TOPICS: Bridges (Structures), Vehicles, Risk, Computer simulation, Degrees of freedom, Virtual work principle
Zhen Hu, Zhifu Zhu and Xiaoping Du
ASME J. Risk Uncertainty Part B   doi: 10.1115/1.4038318
Time-dependent system reliability is computed as the probability that the responses of a system do not exceed prescribed failure thresholds over a time duration of interest. In this work, an efficient time-dependent reliability analysis method is proposed for systems with bivariate responses which are general functions of random variables and stochastic processes. Analytical expressions are derived first for the single and joint upcrossing rates based on the First Order Reliability Method (FORM). Time-dependent system failure probability is then estimated with the computed single and joint upcrossing rates. The method can efficiently and accurately estimate different types of upcrossing rates for the systems with bivariate responses when FORM is applicable. In addition, the developed method is applicable to general problems with random variables, stationary, and non-stationary stochastic processes. As the general system reliability can be approximated with the results from reliability analyses for individual responses and bivariate responses, the proposed method can be extended to reliability analysis of general systems with more than two responses. Three examples, including a parallel system, a series system, and a hydrokinetic turbine blade application, are used to demonstrate the effectiveness of the proposed method.
TOPICS: Event history analysis, Risk, Reliability, Probability, Stochastic processes, System failures, Blades, Failure, Hydraulic turbines
Zhengchun Du, Jian Wu and Jianguo Yang
ASME J. Risk Uncertainty Part B   doi: 10.1115/1.4038170
The influence of component errors on the final error is a key point of error modeling of CNC machine tool. Nevertheless, the mechanism and the quantitatively relationship is not clear; the identification of this mechanism is highly relevant to precision design of CNC machine. In this study, the error modeling based on the Jacobian-torsor(JT) theory is applied to determine how the fundamental errors in mechanical parts influence and accumulate to the comprehensive error of single-axis assembly. Firstly, a brief introduction of the JT theory is provided. Next, the JT Model is applied to the error modeling of a single-axis assembly in a three-axis machine center. Furthermore, the comprehensive errors of the single-axis assembly are evaluated by Monte Carlo simulation based on the synthesized error model. The accuracy and efficiency of the JT Model are verified through a comparison between the simulation results and the measured data from a batch of similar vertical machine centers. Based on the JT Model, the application of quantitative sensitivity analysis of single-axis assembly is investigated, along with the analysis of key error sources to the synthetic error ranges of the single-axis assembly. This model is providing a comprehensive method to identify the key error source of the single axis assembly and has the potential to enhance the tolerance/error allocation of the single axis and the whole machine tool.
TOPICS: Machinery, Manufacturing, Modeling, Errors, Sensitivity analysis, Risk, Computer numerical control machine tools, Simulation results, Simulation, Design, Machine tools
Hidemasa Yamano, Hiroyuki Nishino, Kenichi Kurisaka and Takahiro Yamamoto
ASME J. Risk Uncertainty Part B   doi: 10.1115/1.4037877
The objective of this paper is to develop a probabilistic risk assessment (PRA) methodology against volcanic eruption for decay heat removal function of sodium-cooled fast reactors. In the volcanic PRA methodology development, only the effect of volcanic tephra (pulverized magma) is taken into account because there is a great distance between a plant site assumed in this study and volcanoes. The volcanic tephra (ash) could potentially clog air filters of air-intakes that are essential for the decay heat removal. The degree of filter clogging can be calculated by atmospheric concentration of ash and tephra fallout duration and also suction flow rate of each component. This study evaluated a volcanic hazard using a combination of tephra fragment size, layer thickness and duration. In this paper, functional failure probability of each component is defined as a failure probability of filter replacement obtained by using a grace period to filter failure. Finally, based on an event tree, a core damage frequency has been estimated by multiplying discrete hazard frequencies by conditional decay heat removal failure probabilities. A dominant sequence has been identified as well. In addition, sensitivity analyses have investigated the effects of a tephra arrival reduction factor and pre-filter covering.
TOPICS: Sodium fast reactors, Probabilistic risk assessment, Risk, Failure, Filters, Probability, Heat, Hazards, Damage, Sensitivity analysis, Suction, Air filters, Flow (Dynamics)
Christophe Journeau, Viviane Bouyer, Nathalie Cassiaut-Louis, Pascal Fouquart, Pascal Piluso, Gérard Ducros, Stéphane Gossé, Christine Guéneau, Andrea Quaini, Beatrix Fluhrer, Alexei Miassoedov, Juri Stuckert, Martin Steinbrueck, S Bechta, Pavel Kudinov, Wei Min Ma, Bal Raj Sehgal, Zoltan Hozer, Attila Guba, Dario Manara, David P. Bottomley, Manfred Fischer, Gert Langrock, Holger Schmidt, Monika Kiselova and Jiri Zdarek
ASME J. Risk Uncertainty Part B   doi: 10.1115/1.4037878
SAFEST (Severe Accident Facilities for European Safety Targets) is a European project networking the European experimental laboratories focused on the investigation of a nuclear power plant (NPP) severe accident (SA) with reactor core melting and formation of hazardous material system known as corium. The main objective of the project is to establish coordinated activities, enabling the development of a common vision and severe accident research roadmaps for the next years, and of the management structure to achieve these goals. In this frame, a European roadmap on severe accident experimental research has been developed to define research challenges to contribute to further reinforcement of Gen II and III NPP safety. The roadmap takes into account different SA phenomena and issues identified and prioritized in the analyses of severe accidents at commercial NPPs and in the results of the recentEuropean stress tests carried out after the Fukushima accident. Nineteen relevant issues related to reactor core meltdown accidents have been selected during these efforts. These issues have been compared to a survey of the European SA research experimental facilities and corium analysis laboratories. Finally, the coherence between European infrastructures and R&D needs has been assessed and a table linking issues and infrastructures has been derived. The comparison shows certain important lacks in SA research infrastructures in Europe, especially in the domains of core late reflooding impact on source term, reactor pressure vessel failure and molten core release modes, spent fuel pool accidents, as well as the need for a large scale experimental facility operating with up to 500 kg of chemically prototypic corium melt.
TOPICS: Safety, Hazardous substances, Stress, Melting, Accidents, Failure, Nuclear power stations, Spent nuclear fuels, Reactor vessels, Risk, Fukushima nuclear disaster, Japan, 2011
Niki Lymperea, Andreas Nikoglou and Evangelos Hinis
ASME J. Risk Uncertainty Part B   doi: 10.1115/1.4037879
This study presents an assessment of the RELAP5/MOD3.3 using the experimental work upon the rewetting mechanism of bottom flooding of a vertical annular water flow inside a channel enclosing concentrically a heated rod. The experiments have been carried out in the experimental rig 1 of the Nuclear Engineering Department of National Technical University of Athens (NTUA-NED-ER1) inside which the dry out and the rewetting process of a hot vertical rod can be simulated. Experiments have been conducted at atmospheric conditions with liquid coolant flow-rate within the range of 0.008 and 0.050 kg·s-1 and two levels of subcooling 25 and 50 K. The initial average surface temperature of the rod for each experiment was set at approximately 823 K. The predicted rod surface temperatures during rewetting of the RELAP5/MOD3.3 calculations were compared against the experimental values. The results presented in this study show that RELAP5/MOD3.3 provides temperature estimations of the reflooding mechanism within acceptable marginal error. However, larger deviations between predicted and experimental values have been observed when subcooled water was used instead of saturated one.
TOPICS: Flow (Dynamics), Temperature, Nuclear engineering, Coolants, Errors, Floods, Subcooling, Water, Risk
Keith Friedman, Khanh Bui and John Hutchinson
ASME J. Risk Uncertainty Part B   doi: 10.1115/1.4037725
Vehicle door latch performance testing presently utilizes uniaxial quasi-static loading conditions. Current technology enables sophisticated virtual testing of a broad range of systems. Door latch failures have been observed in vehicles under a variety of conditions. Typically these conditions involve multi-axis loading conditions. The loading conditions presented during rollovers on passenger vehicle side door latches have not been published. Rollover crash test results, rollover crashes, and physical FMVSS 206 latch testing results are reviewed. The creation and validation of a passenger vehicle door latch model is described. The multi-axis loading conditions observed in virtual rollover testing at the latch location are characterized and applied to the virtual testing of a latch in the secondary latch position. The results are then compared with crash test and real world rollover results for the same latch. The results indicate that a door latch which meets the secondary latch position requirements may fail at loads substantially below the FMVSS 206 uniaxial failure loads. In the side impact mode, risks associated with door handle designs and the potential for inertial release can be considered prior to manufacturing with virtual testing. An example case showing the effects of material and spring selection illustrate the potential issues that can be detected in advance of manufacturing. The findings suggest the need for reexamining the relevance of existing door latch testing practices in light of the prevalence of rollover impacts and other impact conditions in today's vehicle fleet environment.
TOPICS: Doors, Testing, Failure, Risk, Vehicles, Manufacturing, Stress, Springs, Testing performance
Kasmet T. Niyongabo and Scott B. Nokleby
ASME J. Risk Uncertainty Part B   doi: 10.1115/1.4032634
A proof-of-concept detector prototype capable of collecting and storing radiometric data in the Jet Boring System (JBS) during pilot hole drilling at the Cigar Lake uranium mine is presented. Cigar Lake is the world’s second highest known grade uranium mine and is located in northern Saskatchewan, Canada. Variant design is used to design, develop, test and implement the detector’s firmware, software and hardware. The battery powered detector is attached inside a JBS drill rod to collect radiometric data through the drilling cycle. A readout box is used to initiate the detector, recharge the battery and download radiometric data afterthe pilot hole drilling cycle is complete.Functional testing results are presented and comparative test results between the JBS gamma probe and the AlphaNUCLEAR Hi-Flux probe are evaluated. Field data collected from a pilot hole is plotted against the pilot hole’s driving layout and jetting recipe to show the accuracy of the readings collected.

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