Severe Accident Context Evaluation for BWR NPPS Based on Long-Term Station Blackout

2016 ◽  
Author(s):  
Gueorgui I. Petkov ◽  
Monica Vela-Garcia
Keyword(s):  
Safety Assessment ◽  
Power Plants ◽  
Human Performance ◽  
Severe Accident ◽  
Research Centre ◽  
Joint Research ◽  
Accident Scenario ◽  
Station Blackout ◽  
Fukushima Daiichi

The realistic study of dynamic accident context is an invaluable tool to address the uncertainties and their impact on safety assessment and management. The capacities of the Performance Evaluation of Teamwork procedure for dynamic context quantification and determination of alternatives, coordination and monitoring of human performance and decision-making are discussed in this paper. The procedure is based on a thorough description of symptoms during the accident scenario progressions (timelines) with the use of thermo-hydraulic model and severe accident codes (MELCOR and MAAP). The opportunities of PET procedure for context quantification are exemplified for the long-term station blackout (LT SBO) accident scenario at Fukushima Daiichi #1 and an hypothetic unmitigated LT SBO at Peach Bottom #1 Boiling Water Reactor Nuclear Power Plants. The context quantification of these LT SBO scenarios is based on the IAEA Fukushima Daiichi accident report, “State-of-the-Art Reactor Consequence Analysis” and thermo-hydraulic calculations made by using MAAP code at the EC Joint Research Centre, Institute for Energy and Transport, Nuclear Reactor Safety Assessment Unit.

Severe Accident Context Quantification for Long-Term Station Blackout in Boiling Water Reactor Nuclear Power Plants

2018 ◽  
Vol 4 (2) ◽  
Author(s):  
Gueorgui I. Petkov ◽  
Monica Vela-Garcia
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Boiling Water ◽  
Severe Accident ◽  
Boiling Water Reactor ◽  
Water Reactor ◽  
Accident Scenario ◽  
Station Blackout ◽  
Fukushima Daiichi

The realistic study of dynamic accident context is an invaluable tool to address the uncertainties and their impact on safety assessment and management. The capacities of the performance evaluation of teamwork (PET) procedure for dynamic context quantification and determination of alternatives, coordination, and monitoring of human performance and decision-making are discussed in this paper. The procedure is based on a thorough description of symptoms during the accident scenario progressions with the use of thermo-hydraulic (TH) model and severe accident (SA) codes (melcor and maap). The opportunities of PET procedure for context quantification are exemplified for the long-term station blackout (LT SBO) accident scenario at Fukushima Daiichi #1 and a hypothetic unmitigated LT SBO at peach bottom #1 boiling water reactor (BWR) reactor nuclear power plants (NPPs). The context quantification of these LT SBO scenarios is based on the IAEA Fukushima Daiichi accident report, “State-of-the-Art Reactor Consequence Analysis” and TH calculations made by using maap code at the EC Joint Research Centre.

Hydrogen Deflagration Analysis in THAI Experiments Using MELCOR Code

2020 ◽  
Author(s):  
Alain Flores y Flores ◽  
Guido Mazzini
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Control Volume ◽  
Critical Issue ◽  
Severe Accident ◽  
Test Facility ◽  
Research Centre ◽  
Time Step ◽  
Volume Number ◽  
Fukushima Daiichi

Abstract In order to develop an appropriate knowledge to support the SUJB (State Office of Nuclear Safety), the CVR (Research Centre Rež), in collaboration with SURO (National Radiation Protection Institute) is developing a methodology to simulate nuclear power plants under accidental conditions. A particular effort is focused in the severe accident phenomenology where hydrogen deflagration carries a critical issue for the containment integrity, such as Fukushima Daiichi accident. For this purpose, THAI (Thermal-hydraulics, hydrogen, aerosol and iodine) experimental campaigns are chosen due to the several tests involved in different conditions. THAI containment test facility is used to open questions concerning the behaviour of hydrogen, iodine and aerosols in the containment of water-cooled reactors during severe accidents. The Fukushima Daiichi Accident demonstrates that the hydrogen deflagration could lead to a significant containment damage. For this reason, a particular attention is given to the hydrogen deflagration scenario. All simulations are prepared and modelled in MELCOR 2.1. The results obtained showed a strong influence related with some factors as: the nodalization pattern, control volume number (CV), flow paths number FP and time step. In order to assess the THAI model with the THAI final reports, a sensitivity analysis focused with those parameters was performed.

Analyses of Feedwater Trip With SBO Sequence of VVER1000 Reactor

2016 ◽  
Vol 2 (4) ◽  
Author(s):  
Guido Mazzini ◽  
Miloš Kynčl ◽  
Marek Ruščák
Keyword(s):  
Nuclear Power ◽  
Lessons Learned ◽  
Severe Accident ◽  
Research Centre ◽  
Stress Tests ◽  
Research Organizations ◽  
Trace Model ◽  
Station Blackout ◽  
Project Prevention

In the Czech Republic, as a follow-up, a consortium of research organizations and universities has decided to simulate selected stress tests’ scenarios, in station blackout (SBO) and the loss of ultimate heat sink (LoUHS), with the aim to verify the national stress report and to analyze time response of respective source term releases. These activities are carried out in the frame of the project prevention, preparedness, and mitigation of consequences of severe accident (SA) at Czech NPPs in relation to lessons learned from stress tests after Fukushima, financed by the Ministry of Interior. The Research Centre Rez has been working on a methods for estimation of leakages and consequences of releases (MELCOR) model for VVER1000 nuclear power plant (NPP) starting with a plant systems nodalization. The aim was to benchmark the MELCOR model with the validated TRAC/RELAP advanced computational engine (TRACE) model, first comparing the steady state and continuing in a long-term SBO plus another event until the beginning of the SA. The presented work is based on the previous paper from the ICONE 23rd Conference hosted in Japan. It focuses mainly on the comparison of the thermohydraulics of the two models created in MELCOR and TRACE codes as outcome of the “Fukushima project.” After that, preliminary general results of the SA progression showing the hydrogen production and the relocation phenomena will be shortly discussed. This scenario is considered closed after some seconds to the break of the lower head. It is important to note that this paper is a substantial update of a previous one (Mazzini et al., 2015, “Analyses of SBO Sequence of VVER1000 Reactor Using TRACE and MELCOR Codes,” 23rd International Conference on Nuclear Engineering (ICONE23)) and although it contains the same descriptive sections, all the results are new.

scholarly journals On the Root Causes of the Fukushima Daiichi Disaster from the Perspective of High Complexity and Tight Coupling in Large-Scale Systems

Symmetry ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 414
Author(s):  
Atsuo Murata ◽  
Waldemar Karwowski
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Large Scale ◽  
High Complexity ◽  
Tight Coupling ◽  
Large Scale Systems ◽  
Safety Issues ◽  
Loss Of Coolant ◽  
Station Blackout ◽  
Fukushima Daiichi

This study explores the root causes of the Fukushima Daiichi disaster and discusses how the complexity and tight coupling in large-scale systems should be reduced under emergencies such as station blackout (SBO) to prevent future disasters. First, on the basis of a summary of the published literature on the Fukushima Daiichi disaster, we found that the direct causes (i.e., malfunctions and problems) included overlooking the loss of coolant and the nuclear reactor’s failure to cool down. Second, we verified that two characteristics proposed in “normal accident” theory—high complexity and tight coupling—underlay each of the direct causes. These two characteristics were found to have made emergency management more challenging. We discuss how such disasters in large-scale systems with high complexity and tight coupling could be prevented through an organizational and managerial approach that can remove asymmetry of authority and information and foster a climate of openly discussing critical safety issues in nuclear power plants.

Source Term Analysis Considering B4C/Steel Interaction and Oxidation During Severe Accidents

2017 ◽  
Author(s):  
Jun Ishikawa ◽  
Tomoyuki Sugiyama ◽  
Yu Maruyama
Keyword(s):  
Source Term ◽  
Severe Accident ◽  
Water Pool ◽  
Energy Agency ◽  
Severe Accidents ◽  
Station Blackout ◽  
Carbon Dioxide Co2 ◽  
Accident Sequences ◽  
Term Analysis

The Japan Atomic Energy Agency (JAEA) is pursuing the development and application of the methodologies on fission product (FP) chemistry for source term analysis by using the integrated severe accident analysis code THALES2. In the present study, models for the eutectic interaction of boron carbide (B4C) with steel and the B4C oxidation were incorporated into THALES2 code and applied to the source term analyses for a boiling water reactor (BWR) with Mark-I containment vessel (CV). Two severe accident sequences with drywell (D/W) failure by overpressure initiated by loss of core coolant injection (TQUV sequence) and long-term station blackout (TB sequence) were selected as representative sequences. The analyses indicated that a much larger amount of species from the B4C oxidation was produced in TB sequence than TQUV sequence. More than a half of carbon dioxide (CO2) produced by the B4C oxidation was predicted to dissolve into the water pool of the suppression chamber (S/C), which could largely influence pH of the water pool and consequent formation and release of volatile iodine species.

Issues Associated With the Development of Severe Accident Management Guidelines for NPPs in China

2013 ◽  
Author(s):  
Zhiyi Yang ◽  
Yimin Chong ◽  
Chun Li ◽  
Jian Deng ◽  
Xianhong Xu ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Severe Accident ◽  
Regulatory Body ◽  
Control Room ◽  
Technical Approach ◽  
Management Guidelines ◽  
Accident Management ◽  
Term Monitoring

After Fukushima nuclear accident, the Severe Accident Management Guidelines (SAMGs) are required according to the policy of the regulatory body in China. Most nuclear power plants (NPPs) in China adopt the technical approach of generic-SAMG of the Westinghouse Owner Group, consisting of severe accident control room guideline (SACRG), diagnostic flow chart (DFC), severe accident guideline (SAG), severe challenge status tree (SCST), severe challenge guideline (SCG), technical support center (TSC) long term monitoring guideline, and SAMG termination guideline (SAEG). A number of issues have been identified during the development of the SAMGs for M310+ NPPs, which is a dominant reactor type in China. The paper discussed these issues and identified some considerations for their resolution.

scholarly journals Extended Station Blackout Coping Capabilities of APR1400

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Sang-Won Lee ◽  
Tae Hyub Hong ◽  
Mi-Ro Seo ◽  
Young-Seung Lee ◽  
Hyeong-Taek Kim
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Water Injection ◽  
Severe Accident ◽  
Injection Strategy ◽  
Safety Improvement ◽  
External Injection ◽  
Station Blackout ◽  
The Government ◽  
External Water

The Fukushima Dai-ichi nuclear power plant accident shows that an extreme natural disaster can prevent the proper restoration of electric power for several days, so-called extended SBO. In Korea, the government and industry performed comprehensive special safety inspections on all domestic nuclear power plants against beyond design bases external events. One of the safety improvement action items related to the extended SBO is installation of external water injection provision and equipment to RCS and SG. In this paper, the extended SBO coping capability of APR1400 is examined using MAAP4 to assess the effectiveness of the external water injection strategy. Results show that an external injection into SG is applicable to mitigate an extended SBO scenario. However, an external injection into RCS is only effective when RCS depressurization capacity is sufficiently provided in case of high pressure scenarios. Based on the above results, the technical basis of external injection strategy will be reflected on development of revised severe accident management guideline.

Causes and Radiological Consequences of the Chernobyl and Fukushima Nuclear Accidents

2018 ◽  
Vol 4 (2) ◽  
Author(s):  
L. Sihver ◽  
N. Yasuda
Keyword(s):  
Local Time ◽  
Emergency Response ◽  
Nuclear Power ◽  
Power Plants ◽  
Severe Accident ◽  
Nuclear Accidents ◽  
Emergency Response System ◽  
Response System ◽  
Accident Management ◽  
Fukushima Daiichi

In this paper, the causes and the radiological consequences of the explosion of the Chernobyl reactor occurred at 1:23 a.m. (local time) on Apr. 26, 1986, and of the Fukushima Daiichi nuclear disaster following the huge Tsunami caused by the Great East Japan earthquake at 2.46 p.m. (local time) on Mar. 11, 2011 are discussed. The need for better severe accident management (SAM), and severe accident management guidelines (SAMGs), are essential in order to increase the safety of the existing and future operating nuclear power plants (NPPs). In addition to that, stress tests should, on a regular basis, be performed to assess whether the NPPs can withstand the effects of natural disasters and man-made failures and actions. The differences in safety preparations at the Chernobyl and Fukushima Daiichi will therefore be presented, as well as recommendations concerning improvements of safety culture, decontamination, and disaster planning. The need for a high-level national emergency response system in case of nuclear accidents will be discussed. The emergency response system should include fast alarms, communication between nuclear power plants, nuclear power authorities and the public people, as well as well-prepared and well-established evacuation plans and evacuation zones. The experiences of disaster planning and the development of a new improved emergency response system in Japan will also be presented together with the training and education program, which have been established to ensure that professional rescue workers, including medical staff, fire fighters, and police, as well as the normal populations including patients, have sufficient knowledge about ionizing radiation and are informed about the meaning of radiation risks and safety.

scholarly journals Study of hydrodynamics performance of a multi-venturi filtering system for BWR severe accident venting strategies

2020 ◽  
Vol 35 (1) ◽  
pp. 16-23
Author(s):  
Alejandro Reyes-Garcia ◽  
Eduardo Sainz-Mejia ◽  
Javier Ortiz-Villafuerte ◽  
Javier Palacios-Hernandez ◽  
Roberto Lopez-Solis
Keyword(s):  
Pressure Drop ◽  
Mass Flow ◽  
Reference Model ◽  
Geometrical Model ◽  
Severe Accident ◽  
Cfd Models ◽  
Station Blackout ◽  
Experimental Values ◽  
Good Agreement

The aim of this project was to determine the capacity of a multi-venturi scrubber filtering system to cope with vented gas mass-flow rate coming from a BWR Mark II primary containment during a long-term station blackout. The multi-venturi filtering system CFD models were developed in the environment of the open source platforms SALOME and OpenFoam. The first geometrical model was created based on the dimensions of a well-known experimental setup, and the results of the pressure drop along the streamwise co-ordinate showed a maximum difference of 10 % in relation to the experimental values for different cases of liquid to gas mass ratios. Then a full scale multi-venturi model was developed. To study the performance of this system during conditions expected in a severe accident, a gas mixture similar to that occurring in a BWR Mark II containment at venting pressure was used as inlet gas. The gas mass-flow that can be cleansed by individual venturis and the pressure required to activate those venturis were computed. The pressure drop profiles in each sector were also determined as the function of different liquid loadings. The results showed good agreement with the capacity of the design taken as the reference model.

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