1,720,969 research outputs found
Modeling by RELAP5-3D© system code of the instability transient occurred on 25th February 1999 at the Oskarshamn-2 BWR
No full textThe OECD/NEA proposes a new international benchmark based on the Boiling Water Reactor instability transient occurred on 25th February 1999 at the Oskarshamn-2 Nuclear Power Plant (Sweden), with the aim of testing the coupled tridimensional neutron kinetics-thermal-hydraulic (3DNK-TH) codes on a challenging simulation. The ENEA Engineering Simulator Laboratory is participating involving a computational model for the RELAP5-3D© code. Currently a complete thermal-hydraulic and 3D neutron kinetics description of the core has been achieved. The simulation results and analyses allowed to fully understand the phenomena, and demonstrated the model suitability in reproducing the instability event with a good level of accuracyThe OECD/NEA proposes a new international benchmark based on the Boiling Water Reactor instability transient occurred on 25th February 1999 at the Oskarshamn-2 Nuclear Power Plant (Sweden), with the aim of testing the coupled tridimensional neutron kinetics-thermal-hydraulic (3DNK-TH) codes on a challenging simulation. The ENEA Engineering Simulator Laboratory is participating involving a computational model for the RELAP5-3D© code. Currently a complete thermal-hydraulic and 3D neutron kinetics description of the core has been achieved. The simulation results and analyses allowed to fully understand the phenomena, and demonstrated the model suitability in reproducing the instability event with a good level of accurac
Simulation of AER-DYN-002 and AER-DYN-003 Control Rod Ejection Benchmarks by RELAP5-3D/PHISICS Coupled Codes
No full textENEA “Casaccia” Research Center is collaborating with Idaho National Laboratory performing activities devoted to the validation of the Parallel and Highly Innovative Simulation for INL Code System (PHISICS) neutron simulation code. In such framework, the AER-DYN-002 and AER-DYN-003 control rod (CR) ejection benchmarks were used to validate the coupled codes RELAP5-3D/PHISICS. The AER-DYN-002 benchmark provides a test case of a CR ejection accident in a VVER-440 at hot-zero-power and end-of-cycle conditions assuming an adiabatic fuel and taking into account only the fuel temperature feedback. The AER-DYN-003 benchmark is based on the same problem; however, the moderator density feedback and the coolant heat removal are also considered. A RELAP5-3D core channel-bychannel, thermal-hydraulic nodalization was developed and coupled, first with the RELAP5-3D internal neutronic routine NESTLE and then with the PHISICS code. Analysis of the AER-DYN-002 results shows that the steady-state solutions are in good agreement with the other participants’ average solution, while some differences are shown in the transient simulations. In the AER-DYN-003 benchmark, however, both steady-state and transient results are in good agreement with the average solution
Effects of cross sections library parameters on the OECD/NEA Oskarshamn-2 benchmark solution
No full textThe OECD/NEA proposes a new international benchmark based on data collected during an instability transient occurred at the Oskarshamn-2 NPP. This benchmark is aimed at testing the coupled 3D Neutron Kinetic–Thermal Hydraulic (3D NK–TH) codes on challenging situations. The ENEA “Casaccia” Research Center, is participating to this benchmark, developing a computational model using the RELAP5-3D© code. The 3DNK model has been already developed from the cross sections dataset calculated by OKG, the Oskarshamn-2 licensee, through the CASMO lattice code. In order to use this neutron cross sections database in RELAP5-3D© a n-dimensional polynomials data fitting and base cross sections values calculations are required. An ad-hoc tool, named PROMETHEUS, has been developed for automatically generating RELAP5-3D©-compatible cross sections libraries. This tool allows at easily visualizing the complex structure of the neutronic datasets; moreover it is exploited for deriving different cross sections libraries needed to evaluate neutronic parameters effects on the reactor instability prediction. Thus, the effects of the fuel temperature and control rod histories, of the discontinuity factors (averaged/not averaged) and of the neutron poisons has been assessed. A ranking table has been produced, demonstrating the relevance of the not-averaged discontinuity factors and of the on-transient neutron poisons calculations for the correct prediction of the Oskarshamn-2 event
Integral study of accident sequences with reference to NPPs next to the Italian borders
No full textThis report presents the activity performed in the framework of LP1, Objective B (Accident consequent evaluation) task B1 Topic 3 (Integral study of accident sequences with reference to BWR and PWR reactor next to Italian borders) of PAR 2014, ADP ENEA-MSE. Three different PWR accidents - Short term Station Blackout (SBO), Loss of Feed Water (LFW), Large Break Loss of Coolant Accident (LBLOCA) - scenarios have been studied by using the MELCOR code. To lead these three accidents to a BDBA, they will be unmitigated and the actions of the operator are assumed to fail; the characterization of the thermal hydraulic behaviour, the in-vessel phenomena, the core degradation and corium behaviour in the lower head are here analyzed. A first estimation of the source term is here also presented for the SBO scenario. For the BWR, a preliminary Fukushima Unit 1 like MELCOR nodalization has been deveped allowes to have a basis to analyse transients scenarios and compare the data with calculated results of other codes and possible full scale plant transient data, if available. The analyses of thermal hydraulic phenomenology of interest, for the validation of severe accident code, related to advanced reactor (as Small Modular Reactor) that could be in operation in the next short term, are here presented. The “scaling issue”, that determines uncertainty in the code calculated data, is here briefly analyzed considering the aspect of interest that should be investigated for the “severe accident” analyses
OSKARSHAMN-2 BWR INSTABILITY EVENT MODELLING BY RELAP5-3D CODE
No full textThe OECD/NEA proposes a new international benchmark based on the data collected from an instability transient occurred at the Oskarshamn-2 NPP with the aim to test the coupled nuclear-thermal-hydraulic (CNTH) codes on challenging situations. The ENEA “Casaccia” Research Center is participating to this benchmark, developing a computational model using RELAP5-3D© code. The model was developed devoting particular attention to the core nodalization which is a critical point in reproducing the instability event. All the 444 core fuel assemblies were independently modeled as a single thermal-hydraulic channel coupled to an equal number of neutron kinetics nodes. Thus a complete thermal-hydraulic and 3D neutron kinetics description of the core, including the bottom and top reflector was achieved. Auxiliary software was also developed for handling the large amount of geometrical data and for performing the CASMO code cross section libraries interpolation. Operating plant data was used to perform the model steady state validation. The instability transient and several sensitivities studies were carried out, using benchmark defined boundary and initial conditions. The effects of the uncertainties of specific physical parameters on the transients results was also assessed. Finally, the simulation results demonstrate the model suitability in reproducing the instability event with a good level of accuracy, while the sensitivity analyses confirm the expected behavior to each perturbation
Fukushima Dai-ichi Unit 1 Accident Simulation by Best Estimate and Integral Codes & Accident Management Procedures Identification Focusing on BWR close to the Italian Borders
No full textThis report presents the activities devoted to the development and validation of models for Severe Accident analyses of BWR. The reference severe accident simulation codes are MELCOR and RELAP/SCDAPSIM. The need to have such tools for performing safety analysis of BWR close to the Italian border is presented. Then, the reconstruction of the sequence of events occurred at Fukushima Dai-ichi Unit 1 is reported. MELCOR nodalization of a generic BWR is described and test calculations are reported. RELAP/SCDAPSIM modelling of Fukushima Dai-ichi Unit 1 is also presented and a preliminary analysis of the accident is performed. This model and results should constitute the basis for future MELCOR works
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
New RELAP5-3D Lead and LBE Thermophysical Properties Implementation for Safety Analysis of Gen IV Reactors
Full text linkThe latest versions of RELAP5-3D© code allow the simulation of thermodynamic system, using different type of working fluids, that is, liquid metals, molten salt, diathermic oil, and so forth, thanks to the ATHENA code integration. The RELAP5-3D© water thermophysical properties are largely verified and validated; however there are not so many experiments to generate the liquid metals ones in particular for the Lead and the Lead Bismuth Eutectic. Recently, new and more accurate experimental data are available for liquid metals. The comparison between these state-of-the-art data and the RELAP5-3D© default thermophysical properties shows some discrepancy; therefore a tool for the generation of new properties binary files has been developed. All the available data came from experiments performed at atmospheric pressure. Therefore, to extend the pressure domain below and above this pressure, the tool fits a semiempirical model (soft sphere model with inverse-power-law potential), specific for the liquid metals. New binary files of thermophysical properties, with a detailed mesh grid of point to reduce the code mass error (especially for the Lead), were generated with this tool. Finally, calculations using a simple natural circulation loop were performed to understand the differences between the default and the new properties
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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