Publikationen


Suche nach „[W.] [Maschek]“ hat 6 Publikationen gefunden
Suchergebnis als PDF
    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    A. Rineiski, S. Gianfelici, W. Maschek, B. Vezzoni, Rui Li, C. Matzerath Boccaccini, F. Gabrielli, M. Flad

    Probabilistic evaluation of the energetics upper bound during the transition phase of an unprotected loss of flow accident for a sodium cooled fast reactor by using a Phenomenological Relationship Diagram

    Nuclear Engineering and Design, vol. 341, no. 146-154

    2019

    DOI: 10.1016/j.nucengdes.2018.11.004

    Abstract anzeigen

    One of the main research goals of the GEN-IV systems is enhancing their safety compared with the former Sodium-Cooled Fast Reactor (SFR) designs. A key issue is the capability of accidents prevention as well as of demonstrating that their consequences do not violate the safety criteria. In order to fulfill such requirements, risk analyses of severe core disruptive accidents are performed. Since the beginning of the SFR development, Hypothetical Core Disruptive Accidents (HCDAs) have played an outstanding role. Numerous safety analyses have been performed for developing and licensing past SFR designs and nowadays a large database of results is available. In particular, a large amount of results of the mechanistic SIMMER-II and SIMMER-III/IV analyses for various core designs and different power classes is available at the Karlsruhe Institute of Technology (KIT). The current paper describes the probabilistic approach based on the Phenomenological Relationship Diagram (PRD), which is used to evaluate the Probability Distribution Function (PDF) of the thermal energy release during the transition phase of an unprotected loss of flow accident scenario for a SFR. The technique allows taking into account the mechanistic nature of the accident scenario. In fact, the available results of the mechanistic analyses of HCDAs in SFRs are used to assess the PDFs of the dominant phenomena affecting the thermal energy release, which are propagated in the PRD by employing a Monte Carlo method.

    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    K. Morita, W. Maschek, Rui Li, C. Matzerath Boccaccini, F. Gabrielli

    Investigation on upper bounds of recriticality energetics of hypothetical core disruptive accidents in sodium cooled fast reactors

    Nuclear Engineering and Design, vol. 326, no. January, pp. 392-402

    2018

    DOI: 10.1016/j.nucengdes.2017.11.002

    Abstract anzeigen

    One key research goal for GEN-IV systems is an enhanced safety compared to the former Sodium Cooled Fast Reactor concepts. A key issue is built-in safety and the capability to prevent accidents and to demonstrate that their consequences do not violate aimed-at safety criteria. From the beginning of SFR development the Core Disruptive Accident (CDA) has played an outstanding role in the safety assessment. Under core disruptive accident conditions with core melting the fuel might compact, prompt criticality might be achieved and a severe nuclear power excursion with mechanical energy release might be the consequence. Numerous safety analyses accompanied the development and the licensing procedures of past fast reactor projects. A central issue of all analyses was the assessment of a realistic upper bound of energetics especially related to recriticalities in disrupted core configurations. Striving for an even higher safety level for next generation reactors a new strategy focused on the development and introduction of preventive and mitigative measures both to reduce the chance for a severe accident development and to mitigate its energetics. For assessing the effectiveness of these measures the knowledge of the CDA behavior is essential. In this context and on basis of new code developments, new experimental insights and extended studies for many reactor types of different power classes over the recent years, the issue of a realistic upper bound of energetics of the late core melt phases is again of relevance. Of special interest is the identification of natural and intrinsic mechanisms that limit the escalation of energetics. The current paper deals with these issues and tries to add supportive facts on the limits of CDA energetics. The evaluation of results of mechanistic SIMMER-II and SIMMER-III/IV analyses performed for various core designs and power classes and specific model case studies in 2D and 3D geometry indeed supports the idea of a limit of recriticality energetics. Intrinsic mechanisms exist, which limit the escalation energetics even in case of a strong blockage confinement suppressing any fuel discharge and allowing on-going sloshing recriticalities. In the light of the available information and taking into account relevant scientific publications and studies by the international community on the subject, one could conclude that an upper bound for energetics in the range given in the paper can be deduced.

    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    L. Guo, S. Wang, A. Rineiski, W. Maschek, Rui Li, M. Flad

    Numerical investigation of SIMMER code for fuel-coolant interaction

    International Journal of Hydrogen Energy, vol. 41, no. 17, pp. 7227-7232

    2016

    DOI: 10.1016/j.ijhydene.2016.01.080

    Abstract anzeigen

    Fuel-coolant interaction (FCI) is a very complex but important issue in the safety analysis of the severe accidents for nuclear reactors due to the rapid multiple thermos–hydrodynamic activities. Until now, there are still large uncertainties existing in various phases during the FCI process, such as the melt solidification, fragmentation and relocation, film boiling on the melt surface, coolant vaporization and following vapor explosion, and so on. SIMMER-III code was first developed to analyses core disruptive accidents in liquid-metal fast reactors (LMFRs) as an integral numerical tool coupling multiphase thermal hydraulic code with neutron kinetics model, and was demonstrated its reasonable flexibility in some FCI simulations. In this paper, the applicability of the code in simulating the premixing phase of FCI process is verified in comparison with a related jet-type experiment in literature. In addition, the sensitivity analysis on several key parameters of the related models in the SIMMER code was performed to assess the impacts in the simulation of the FCI premix phase. It is expected that the results can provide some numerical experience for the uncertainty analysis of FCI calculation using SIMMER-III code.

    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    A. Rineiski, W. Maschek, B. Vezzoni, Rui Li, C. Matzerath Boccaccini, M. Flad

    Impact of the Bell–Plesset instability on centralized sloshing in pool geometry

    International Journal of Hydrogen Energy, vol. 41, no. 17, pp. 7126-7131

    2016

    DOI: 10.1016/j.ijhydene.2016.01.152

    Abstract anzeigen

    The theoretical and numerical analyses have been conducted to investigate the kinetic energy attenuation characteristics on basis of identical geometry and liquid properties together with an existing centralized sloshing experiment. The goal of this paper is to assess the quantitative impact of the Bell–Plesset (BP) instability on the sloshing motion. The results show that BP instability plays a certain role in azimuthal energy dissipation when the sloshing waves are moving inwards and converging in cylindrical geometry. The velocity attenuation is calculated via a perturbation flow equation assuming the initial perturbation length 1 mm, it shows that the velocity could be suppressed by 25% due to BP instability. The corresponding simulation using particle method has been performed. With the help of numerical simulation, the initial perturbation length is approximated as 1.3 mm which is in line with the assumption in the theoretical analysis.

    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    A. Rineiski, W. Maschek, Rui Li, C. Matzerath Boccaccini, M. Marchetti, V. Kriventsev

    Bell-Plesset Instability Analysis for an Inward Centralized Sloshing

    Nuclear Engineering and Design, vol. 297, pp. 312-319

    2016

    DOI: 10.1016/j.nucengdes.2015.12.010

    Abstract anzeigen

    Liquid sloshing is a typical phenomenon when liquid in a container has an unrestrained surface. In fast reactors under core disruptive accidents (CDAs) conditions specific sloshing motions could be encountered that can be described as a centralized sloshing. It is important to investigate the mitigating and augmenting factors for such centralized sloshing motions. Any retardation or instability effects that reduce the compaction speed and resulting reactivity ramp rate are of importance, requiring an understanding of the kinetic energy dissipation of an inward centralized slosh. In this paper, the Bell–Plesset (BP) instability has been studied theoretically and numerically based on a corresponding inward centralized sloshing experiment. The theoretical analysis is based on the classical perturbation theory and the simulation has been conducted by a fully mesh-free, Lagrangian particle numerical method. With our experimental data, the initial perturbation length 1.3 mm is approximated by the numerical calculation as supplement of the purely theoretical analysis. The outward and inward sloshing timings have been re-checked from the experiment that the inward velocity is reduced by around 20% compared to outward velocity. It experimentally confirms reasonably well the numerical result 17.5%. The experimental, numerical and theoretical analysis show that BP instability plays a certain role in azimuthal energy dissipation when the sloshing waves are moving inwards and converging in cylindrical geometry, for the experiment case the velocity reduction may be 17.5%.

    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    X.-N. Chen, A. Rineiski, W. Maschek, Rui Li, C. Matzerath Boccaccini

    Study on Severe Accident Scenarios: Pin Failure Possibility of MYRRHA-FASTEF Critical Core

    Energy Procedia, vol. 71, pp. 14-21

    2015

    DOI: 10.1016/j.egypro.2014.11.850

    Abstract anzeigen

    The present work is carried out within the European FP7 project SEARCH, in which the MYRRHA demonstrator reactor is designed to be able to operate both in ADS mode and in critical mode using lead-bismuth eutectic (LBE) as primary coolant. According to the project task definition, the pin failure and fuel dispersion scenarios in severe accidents have to be extensively studied for reactor safety analysis. In this paper, the unprotected severe transients analyses for the MYRRHA-FASTEF critical core were performed using SIMMER-III code. The aim of the current work was to obtain a deeper understanding of core material redistribution processes before and after pin damage, since the Archimedes force could move pellets, chunks and fuel particles upwards out of the core and redistribute them into the upper pool region and peripheral structures. Starting the simulations with the steady state calculation, relevant parameters reflect good agreement with the design operational conditions. For the transients three postulated severe accident scenarios were proposed that may possibly lead to pin failure and furthermore core damage: unprotected loss of flow (ULOF), unprotected transient overpower (UTOP) and unprotected blockage accident (UBA), where in particular the entrance of fuel assembly is blocked as a side window is still open. The three transients, starting from the steady state conditions, have been investigated. The calculation results show for the MYRRHA-FASTEF that under the conditions chosen all simulated transient cases do not lead to a pin failure and fuel redistribution.