scholarly journals On the Analysis and Evaluation of Direct Containment Heating with the Multidimensional Multiphase Flow Code MC3D

2010 ◽  
Vol 2010 ◽  
pp. 1-13 ◽  
Author(s):  
Renaud Meignen ◽  
Tanguy Janin
Keyword(s):  
Multiphase Flow ◽  
Safety Analysis ◽  
Severe Accident ◽  
Dispersal Rate ◽  
Dynamical Processes ◽  
Analysis And Evaluation ◽  
The Past ◽  
Computer Codes ◽  
Direct Containment Heating ◽  
Level 2

In the course of a postulated severe accident in an NPP, Direct Containment Heating (DCH) may occur after an eventual failure of the vessel. DCH is related to dynamical, thermal, and chemical phenomena involved by the eventual fine fragmentation and dispersal of the corium melt out of the vessel pit. It may threaten the integrity of the containment by pressurization of its atmosphere. Several simplified modellings have been proposed in the past but they require a very strong fitting which renders any extrapolation regarding geometry, material, and scales rather doubtful. With the development of multidimensional multiphase flow computer codes, it is now possible to investigate the phenomenon numerically with more details. We present an analysis of the potential of the MC3D code to support the analysis of this phenomenon, restricting our discussion to the dynamical processes. The analysis is applied to the case of French 1300 MWe PWR reactors for which we derive a correlation for the corium dispersal rate for application in a Probabilistic Safety Analysis (PSA) level 2 study.

Onset of Gas Blowthrough During Melt Expulsion From a Hole in a RPV: Numerical Analysis Using the SIMMER Code

2006 ◽  
Author(s):  
Frank Kretzschmar
Keyword(s):  
Numerical Analysis ◽  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Severe Accident ◽  
Core Material ◽  
Test Facility ◽  
Computer Codes ◽  
Direct Containment Heating ◽  
Heating Up

In the case of a severe accident in a nuclear power plant there is a residual risk, that the Reactor Pressure Vessel (RPV) does not withstand the thermal attack of the molten core material, of which the temperature can be about 3000 K. For the analysis of the processes governing melt dispersal and heating up of the containment atmosphere of a nuclear power plant in the case of such an event, it is important to know the time of the onset of gas blowthrough during the melt expulsion through the hole in the bottom of the RPV. In the test facility DISCO-C (Dispersion of Simulant Corium-Cold) at the FZK /6/, experiments were performed to furnish data for modeling Direct Containment Heating (DCH) processes in computer codes that will be used to extrapolate these results to the reactor case. DISCO-C models the RPV, the Reactor Coolant System (RCS), cavity and the annular subcompartments of a large European reactor in a scale 1:18. The liquid type, the initial liquid mass, the type of the driving gas and the size of the hole were varied in these experiments. We present results for the onset of the gas blowthrough that were reached by numerical analysis with the Multiphase-Code SIMMER. We compare the results with the experimental results from the DISCO-C experiments and with analytical correlations, given by other authors.

Direct Containment Heating: A Solved Risk Issue

2002 ◽  
Author(s):  
Roberto Passalacqua
Keyword(s):  
Model Development ◽  
Blow Down ◽  
Severe Accidents ◽  
Nuclear Plants ◽  
Computer Codes ◽  
Risk Issue ◽  
Direct Containment Heating ◽  
Level 2 ◽  
Core Concrete ◽  
Similar Risk

In case of a High Pressure Melt Ejection (HPME) heated gas and corium may be expelled from the bottom head of a reactor vessel reaching the containment atmosphere, leading to a Direct Containment Heating (DCH). In addition, released gases might burn (e.g. hydrogen) causing a high load of the reactor containment building. Corium dispersal phenomena also strongly affect consequences of Molten Core-Concrete Interaction (MCCI) since the corium mass, which remains within the cavity, may remarkably diminish. Several computer codes are able to simulate the response of nuclear plants during hypothetical severe accidents: MELCOR, MAAP, ESCADRE and ASTEC have the capability to describe corium slump into the reactor cavity, vessel gases blow-down and possible corium entrainment. In this paper the various steps of model development, validation, plant-specific applications, etc., are described in the attempt of establishing a risk-oriented methodology with the target of solving this particular risk-issue. ENEA mature expertise in level-2 PSA analyses shows that the DCH phenomenology can be considered a solved risk issue. The applied methodology gives also hints and/or guidelines for solving similar risk issues in current PSA (level 2) analysis.

Safety Analysis Model of DUCG Based on FMEA/FTA

2018 ◽  
Author(s):  
Zhenxu Zhou ◽  
Hao Nie ◽  
Chunling Dong ◽  
Qin Zhang
Keyword(s):  
Failure Modes ◽  
Fault Tree Analysis ◽  
Safety Analysis ◽  
Nuclear Industry ◽  
Analysis Model ◽  
Industrial Systems ◽  
The Past ◽  
Research Cycle ◽  
Dynamic Uncertain Causality Graph ◽  
Analytical Power

Failure Modes and Effects Analysis (FMEA) is a useful tool to find possible flaws, to reduce cost and to shorten research cycle in complex industrial systems. Fault Tree Analysis (FTA) has gained credibility over the past years, not only in nuclear industry, but also in other industries like aerospace, petrochemical, and weapon. Both FMEA and FTA are effective techniques in safety analysis, but there are still many uncertain factors in them that are not well addressed until now. This paper combines FMEA and FTA based on Dynamic Uncertain Causality Graph (DUCG) to solve this issue. Firstly, the FMEA model is mapped into a corresponding DUCG graph. Secondly, FTA model is mapped into a corresponding DUCG graph. Thirdly, combine the above DUCG graphs. Finally, users can modify the combined DUCG graph and calculations are made. This paper bridges the gap between FMEA and FTA by combining the two methods using DUCG. And additional modeling power and analytical power can be achieved with the advantages of the combined DUCG safety analysis model and its inference algorithm. This method can also promote the application of DUCG in the system reliability and safety analysis. An example is used to illustrate this method.

scholarly journals Aeromedical evacuation: experiences from the UK military level 2 hospital in Bentiu, South Sudan, during Op TRENTON

2020 ◽  
pp. bmjmilitary-2020-001448 ◽  
Author(s):  
Leanne Jane Eveson ◽  
W Nevin ◽  
N Cordingley ◽  
M Almond
Keyword(s):  
South Sudan ◽  
Febrile Illness ◽  
Vital Role ◽  
Diagnostic Group ◽  
Aeromedical Evacuation ◽  
The Past ◽  
The Uk ◽  
To Receive ◽  
Level 2

IntroductionAeromedical Evacuation (AE) is a vital role of the Defence Medical Services (DMS). With a far-reaching defence global footprint, an AE capability is crucial to enable movement of patients in the fastest, safest and least stressful way that meets or exceeds the level of care an injured or ill person may expect to receive in the UK. Operation (Op) TRENTON is a UK military humanitarian operation in support of the United Nations (UN) Mission in South Sudan.MethodsA retrospective analysis was carried out of all patients who underwent AE from the UK level 2 hospital at Bentiu during Op TRENTON over a 17-month period from June 2017 to October 2018.Results14 patients underwent AE. The median age was 36 (22–64) years and all patients were male. 21% of AEs were for UK personnel and 79% were for UN personnel. 29% of AEs were due to non-battle injury with the remainder due to disease. Musculoskeletal was the largest diagnostic group (n=4) followed by respiratory (n=3), cardiovascular (n=2), undifferentiated febrile illness (n=2), neurology (n=1), renal medicine (n=1) and psychiatry (n=1).ConclusionsPatients requiring AE from the level 2 hospital at Bentiu mostly had musculoskeletal and medical pathology, a stark contrast to the trauma patient cohort from operations in the past. The majority of patients had definitive care under the medical team highlighting the requirement for DMS physicians and the AE team, to be trained in acute, general and aviation medicine. The majority of AE moves were for UN personnel and on UN airframes, highlighting the importance of a sound understanding of the nations we are working with.

Development of Transient and Safety Analysis Method for ATF With SiC

2016 ◽  
Author(s):  
Fumie Sebe ◽  
Masato Yamada ◽  
Yutaka Takeuchi ◽  
Kazuo Kakiuchi ◽  
Kazunari Okonogi
Keyword(s):  
High Temperature ◽  
Oxidation Reaction ◽  
Transient Analysis ◽  
Safety Analysis ◽  
Hydrogen Gas ◽  
Lessons Learned ◽  
Temperature Behavior ◽  
Severe Accident ◽  
Water Steam ◽  
Accident Conditions

Based on lessons learned from the Fukushima Daiichi nuclear power plant accident, pursuit of accident tolerant fuel (ATF) has been discussed by many institutions in the world. Toshiba identified a silicon carbide (SiC) ceramic as the most promising material for accident tolerant fuel. Since SiC has less active characteristics in the presence of high temperature water steam (H2O) and is expected to be tolerant of severe accident conditions. Moreover, SiC has a smaller neutron absorption cross-section which is advantageous feature in terms of neutron economy. Zirconium alloys (Zry) are one of the main structural materials in LWR core. In high temperature H2O environment under severe accident conditions, Zry rapidly reacts with H2O and oxidation reaction accompanied by release of hydrogen gas occurs. Since SiC may inhibit the progress of oxidation reaction compared to Zry metal alloys, hydrogen and heat generation is expected to decrease in the case of core uncovered accident conditions. In order to confirm the advantage of SiC over Zry as core materials, transient analysis and safety analysis are carried out. For transient analysis, analyses of temperature behavior of cladding at plant transient condition are carried out with best-estimate transient analysis code. This analysis confirmed the effect of physical properties differences between SiC and Zry on cladding temperature behavior. Moreover to indicate the effectiveness of SiC under the core uncovered condition with oxidation reaction, safety analysis with latest “MAAP” code is carried out and the whole plant behavior during severe accident sequence is simulated. This analysis showed the effectiveness of SiC to mitigate the oxidation reaction. As the result of these analyses, the advantage of SiC over Zry can be perceived. And also, future challenges of SiC application as ATF can be clarified through these analyses.

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