The course focuses on the probabilistic quantification of accident sequences and the link between accident sequences and consequences. Previous sessions in this series have focused on the quantification of system reliability (Session A) and the developmen...

The purpose of the present paper is to describe a methodology which was developed as part of the QUASAR (Quantification and Uncertainty Analysis of Source Terms for Severe Accidents in Light Water Reactors) program at BNL. QUASAR is a large program which will apply the methodology described in this paper to severe accident ...

The volume presents the methodology and results of the integrated accident sequence analysis of the LaSalle Unit II nuclear power plant. Integrated results are obtained by merging all of the accident sequences' cut sets from the internal and external even...

A study has been performed as part of the Severe Accident Risk Reduction Program (SARRP) to investigate the response of a particular pressurized water reactor with an ice-condenser containment (Sequoyah Unit 1) to postulated severe accidents. A detailed containment event tree for the Sequoyah plant has been devised to describe the various possible ...

Probabilistic risk assessment (PRA) methodology has emerged as one of the most promising tools for assessing the impact of human interactions on plant safety and understanding the importance of the man/machine interface. Human interactions were considered to be one of the key elements in the quantification of accident sequences in a ...

In a cooperative effort among European and US analysts, an assessment of the comparative safety performance of metal and oxide fuels during accidents in a large (3500 MWt), pool-type, liquid-metal-cooled reactor (LMR) was performed. The study focused on three accident initiators with failure to scram: the unprotected loss-of-flow (ULOF), the unprotected ...

IRRAS2 is an Integrated Probability Risk Assessment (PRA) software tool that gives the user the ability to create and analyze fault trees and event trees using a personal computer. The program provides functions for fault tree and event tree construction and analysis. The fault tree functions range from graphical fault tree construction to fault tree cut set generation and ...

IRRAS2 is an Integrated Probability Risk Assessment (PRA) software tool that gives the user the ability to create and analyze fault trees and event trees using a personal computer. The program provides functions for fault tree and event tree construction and analysis. The fault tree functions range from graphical fault tree construction to fault tree cut set generation and ...

A study has been performed as part of the Severe Accident Risk Reduction Program (SARRP) to investigate the response of a particular pressurized water reactor with a subatmospheric containment (Surry Unit 1) to postulated severe accidents. A detailed containment event tree for the Surry plant has been devised to describe the various possible ...

This paper reports on a cooperative effort among European and U.S. analysts, which is an assessment of the comparative safety performance of metal and oxide fuels during accidents in a 3500-MW (thermal), pool-type, liquid-metal-cooled reactor (LMR) is performed. The study focuses on three accident initiators with failure to scram: the unprotected ...

The Light-Weight Radioisotope Heater Unit (LWRHU) Final Safety Analysis Report (FSAR), Volume 2, Accident Model Document (AMD) describes potential accident scenarios during the Galileo mission and evaluates the response of the LWRHUs to the associated accident environments. Any resulting source terms, consisting of PuO2 (with Pu-238 ...

The Light-Weight Radioisotope Heater Unit (LWRHU) Final Safety Analysis Report (FSAR), Volume 2, Accident Model Document (AMD) describes potential accident scenarios during the Galileo mission and evaluates the response of the LWRHUs to the associated accident environments. Any resulting source terms, consisting of PuO2 (with Pu-238 ...

The inputs to the accident sequence evaluation include the system fault tree models and the event tree models. Each event tree sequence defines a unique accident sequence. The qualitative analysis of an accident sequence is concerned with determining ...

Severe accident management can be defined as the use of existing and/or alternative resources, systems and actors to prevent or mitigate a core-melt accident. For each accident sequence and each combination of severe accident management strategies, there ...

A strategy has been developed for systematically addressing and handling the hazards posed by a transportation accident involving hazardous materials. The Accident Management Orientation Guide presents this system as a logic sequence of events in a color-...

Information concerning the dominant accident sequences from twelve published probabilistic risk assessments (PRA) is cataloged in this report, which is published as a part of the Accident Sequence Evaluation Program (ASEP). The purpose of the report is to...

As part of the Severe Accident Policy Statement implementation, the probabilistic quantification of accident sequence frequencies that may lead to core damage is a key element in demonstrating a plant's safety status relative to US Nuclear Regulatory Commission (NRC) staff goals. One of the key ...

Event trees have been constructed for all phases of LMFBR accidents. The trees proved useful for identifying meaningful initiating accident categories and containment responses. In these areas, quantification appears feasible, given an adequate data base....

Safe operation of SRS facilities continues to be the highest priority of the Savannah River Site (SRS). One of these facilities, the Defense Waste Processing Facility or DWPF, is currently undergoing cold chemical runs to verify the design and construction preparatory to hot startup in 1995. The DWPFF is a facility designed to convert the waste currently stored in tanks at the 200-Area tank farm ...

A probabilistic risk assessment (PRA) was conducted for a loss of coolant accident, (LOCA) in the McMaster Nuclear Reactor (MNR). A level 1 PRA was completed including event sequence modeling, system modeling, and quantification. To support the quantification of the accident ...

This volume describes the methodologies used in the data analysis, the screening human error analysis, and the common mode human error analysis performed in support of the LaSalle PRA. Selected results are presented in this volume. The remainder of the results are presented in other volumes of this report where they are actually used. The data review process used in the determination of the data ...

This volume describes the methodologies used in the data analysis, the screening human error analysis, and the common mode human error analysis performed in support of the LaSalle PRA. Selected results are presented in this volume. The remainder of the results are presented in other volumes of this report where they are actually used. The data review process used in the determination of the data ...

As part of the Severe Accident Sequence Analysis (SASA) program of the Nuclear Regulatory Commission (NRC), threats to containment and ways in which operators can help preserve containment integrity during severe accidents are examined. Severe accidents a...

The report describes a human factors research project performed to: (1) support the Severe Accident Sequence Analysis (SASA) program and (2) develop a descriptive model of operator response in accident management. The first goal was accomplished by workin...

This study developed a set of dominant accident sequences that could be applied generically to domestic commercial PWRs as a standardized basis for a probabilistic seismic risk assessment. This was accomplished by ranking the Zion 1 accident sequences. The pertinent PWR safety systems were compared on a ...

Brookhaven National Laboratory (BNL) assisted the Accident Sequence Evaluation Program (ASEP) by performing a Human Reliability Analysis (HRA) of the operations crew tasks during the Anticipated Transient Without Scram (ATWS) accident sequence with Main Steam Isolation Valve (MSIV) closure at the Peach Bottom ...

This procedures guide describes methods for performing probabilistic risk assessments (PRAs) for nuclear power plants at four levels of scope: (1) systems analysis; (2) systems and containment analysis; (3) systems, containment, and consequence analysis; and (4) full risk assessment, including external events. After reviewing its objectives and limitations, this document describes the organization ...

This work presents a quantitative assessment of the impact that the emergency operating instructions (EOIs) of operating nuclear power plants may have on the frequency of severe accident sequences. Frequencies of such sequences were calculated based on th...

The current state of knowledge with respect to the analysis of postulated accident sequences in fast breeder reactors, as well as some implications to fast reactor design, are reviewed. The accidents considered include loss of coolant flow and transient overpower, both with a postulated failure to scram. The associated ...

This report describes analyses of the response of a Pressurized-Water Reactor at the Zion Plant to hypothetical core-meltdown sequences. The analyses consider the progression of core meltdown, containment response, and consequences to the public for many specific accident sequences within the categories of Loss of Coolant ...

Information concerning the dominant accident sequences from twelve published probabilistic risk assessments (PRA) is cataloged in this report, which is published as a part of the Accident Sequence Evaluation Program (ASEP). The purpose of this report is to provide users of PRA information a single reference ...

Mar 30, 2011 ... Sequence of Major Events of the Challenger Accident. Image library of the STS- 51L Challenger mission at Johnson Space Center. ...

Road traffic accident data in Nigeria generally lack exact coordinate information. Accident analysis is, therefore, restricted to aggregate data on trends, magnitude and temporal dimensions. This article addresses the road accident problem in Jos between 1995 and 1999 through a road profiling approach. Results show that four gateway ...

The Accident Analysis in the Safety Analysis Report (SAR) for the Savannah River Site (SRS) Defense Waste Processing Facility (DWPF) has recently undergone an upgrade. Non-reactor SARs at SRS (and other Department of Energy (DOE) sites) use probabilistic techniques to assess the frequency of accidents at their facilities. This paper describes the ...

This paper presents a methodology to evaluate the reliability of passive systems characterized by a moving fluid and whose working is based on thermal-hydraulic (T-H) principles. The methodology has been developed in the framework of a Project called Reliability Methods for Passive Safety Functions (RMPS), performed under the auspices of the European 5. Framework Programme. The methodology deals ...

This report documents an interim framework for the quantification of the probability of errors of decision on the part of nuclear power plant operators after the initiation of an accident. The framework can easily be incorporated into an event tree/fault tree analysis. The method presented consists of a structure called the operator action tree and a time ...

This report describes the results of safety-evaluation accidents selection by the probabilistic safety analysis method. The accident sequences following on nine initial events were analyzed by means of the event tree method. The occurrence probability (P)...

As part of the Severe Accident Risk Reduction Program, researchers at Sandia National Laboratories have constructed a group of containment event trees to be used in the analysis of key accident sequences for light water reactors (LWR) during postulated se...

A parameter study was carried out for the FRM and the KKE7 core; in this study the effect of the important parameters on the chronological accident sequence and the max. power that was reached was investigated for the startup accident as the limiting case...

The report covers an accident delineation study undertaken to organize and evaluate the available information concerning LMFBR accident sequences and to identify key phenomenological and system-response uncertainties. The study can help provide a basis fo...

The liberation of radioactive materials into various containment locations during a severe accident creates a radiation field that may have a significant impact on the accident progression. High radiation may not only impair the functioning of important e...

...sequence of events leading to the accident or incident, to the extent...the consequences of a launch accident, launch incident, reentry accident, reentry incident, or other...adopt preventive measures for avoiding recurrence of the event....

The current state of knowledge of fast breeder reactors is reviewed. The primary focus on the analysis of postulated accident sequences and the implications to fast-reactor design. The accidents considered include loss-of-collant flow and transient overpower, both with a postulated failure to scram. The associated ...

The paper discusses work conducted to: (1) support the severe accident sequence analysis of a nuclear power plant transient based on an assessment of operator actions, and (2) develop a descriptive model of operator severe accident management. Operator actions during the transient are assessed using qualitative and quantitative ...

In support of the Accident Sequence Precursor Program (ASP), the U.S. Nuclear Regulatory Commission (NRC), in conjunction with the Idaho National Laboratory (INL), in 1994 developed the Accident Sequence Precursor Standardized Plant Analysis Risk Model (A...

For Zion, the following accident sequences were examined: station blackout with failure of auxiliary feedwater (TMLB'), loss of collant accidents (LOCA's) of various sizes inside containment, and the V-sequence interacing system LOCA which involves direct...

The paper will discuss work being conducted during this human factors review including: (1) support of the Severe Accident Sequence Analysis (SASA) Program based on an assessment of operator actions, and (2) development of a descriptive model of operator ...

CONTAIN is an integrated containment thermohydraulic and aerosol transport code. The choice of the Surry plant provides an opportunity to compare the CONTAIN calculations to those recently performed by Battelle Columbus Laboratories. The accident sequence...

A study is reported on the feasibility of the use of microwave dielectric heating to simulate the nuclear heat source in LMFBR 'transition phase' accident sequence volume-boiling simulation experiments. The adequacy of microwave heating is judged based up...

...Integrated safety analysis. (1) Each licensee...an integrated safety analysis, that is of appropriate... (iv) Potential accident sequences caused by...occurrence of each potential accident sequence identified...Integrated safety analysis team...

In support of the US Nuclear Regulatory Commission Accident Management Research Program, the availability of instruments to supply accident management information during a broad range of severe accidents is evaluated for a Boiling Water Reactor with a Mark I containment. Results from this evaluation include: (1) the identification of ...

A case study modeling the thrust reverser system (TRS) in the context of the fatal accident of a Boeing 767 is presented to illustrate the application of Probabilistic Safety Assessment methods. A simplified risk model consisting of an event tree with supporting fault trees was developed to represent the progression of the accident, taking into account the ...

This paper highlights the interim results of ASEP. ASEP is one of many programs sponsored by the Nuclear Regulatory Commission (NRC) to study various aspects of severe core damage accidents. The results of ASEP will ultimately focus on identifying the most likely accident sequences and the high risk accident ...

The anatomy of the disaster at the BP refinery. Management and technical problems are highlighted. Factors that are common to many sites are emphasized. Animated sequences show the factors and there effects on the accident sequence.

Since its inception in October 1980, the Severe Accident Sequence Analysis (SASA) program at Oak Ridge National Laboratory (ORNL) has completed four studies including Station Blackout, Scram Discharge Volume Break, Loss of Decay Heat Removal, and Loss of Injection accident sequences for the Browns Ferry Nuclear ...

The Accident Sequence Precursor (ASP) Program at ORNL analyzed about 14.000 Licensee Event Reports (LERs) filed by US nuclear power plants 1987--1993. There were 193 events identified as precursors to potential severe core accident sequences. These are re...

Event trees have been constructed for all phases of LMFBR accidents. The trees proved useful for identifying meaningful initiating accident categories and containment responses. In these areas, quantification appears feasible, given an adequate data base. Event trees were also used to represent in-core phenomenological questions ...

In support of the Nuclear Regulatory Commission's (NRC's) assessment of the risk from severe accidents at commercial nuclear power plants in the U.S. reported in NUREG-1150, the Severe Accident Risk Reduction Program (SAARP) has completed a revised calcul...

The RAM package design certification process has two important elements, testing and acceptance. These terms sound very similar but they have specific meanings. Qualification testing in the context of this study is the imposition of simulated accident test conditions upon the candidate package design. (Normal transportation environments may also be included.) Following ...

The main features of domino accidents in process/storage plants and in the transportation of hazardous materials were studied through an analysis of 225 accidents involving this effect. Data on these accidents, which occurred after 1961, were taken from several sources. Aspects analyzed included the accident ...

Different hypothetical accident sequences have been simulated at Unit 1 of the Juragua nuclear power plant in Cuba, a plant with two VVER-440 V213 units under construction. The computer code MELCOR was employed for these simulations. The sequences simulated are: (1) a design-basis accident (DBA) large loss of ...

The U.S. Nuclear Regulatory Commission is conducting an accident management research program that emphasizes the use of severe accident research to enhance the ability of plant operating personnel to effectively manage severe accidents. Hence, it is necessary to ensure that the plant instrumentation and information systems adequately ...

This paper describes the methodology used in a quantitative hazard assessment of a nuclear weapon disassembly process. Potential accident sequences were identified using an accident-sequence fault tree based on operational history, weapon safety studies, a hazard analysis team composed of weapons experts, and walkthroughs of the ...

In this report, the scoping quantification procedures for external events in probabilistic risk assessments of nuclear power plants are described. External event analysis in a PRA has three important goals; (1) the analysis should be complete in that all events are considered; (2) by following some selected screening criteria, the more significant events are identified for ...

In this report, the scoping quantification procedures for external events in probabilistic risk assessments of nuclear power plants are described. External event analysis in a PRA has three important goals; (1) the analysis should be complete in that all events are considered; (2) by following some selected screening criteria, the more significant events are identified for ...

This paper presents a comparison of calculations of severe accident progression for several postulated accident sequences for representative Pressurized Water Reactors (PWR) and Boiling Water Reactors (BWR) nuclear power plants performed with the MELCOR 1.8.3 and the MAAP4 computer codes. The PWR system examined in this study is a 1100 ...

In support of the US Nuclear Regulatory Commission (NRC) Accident Management Research Program, a methodology has been developed for identifying the plant information needs necessary for personnel involved in the management of an accident to diagnose that an accident is in progress, select and implement strategies to prevent or mitigate ...

In the frame of the Accidental Risk Assessment Methodology for Industries (ARAMIS) project, this paper aims at presenting the work carried out in the part of the project devoted to the definition of accident scenarios. This topic is a key-point in risk assessment and serves as basis for the whole risk quantification. The first result of the work is the ...

This document presents a method of source term estimation that reflects the current understanding of source term behavior and that can be used during an event. The various methods of estimating radionuclide release to the environment (source terms) as a result of an accident at a nuclear power reactor are discussed. The major factors affecting potential radionuclide releases ...

Boiling water reactor severe accident sequence studies are being carried out using Browns Ferry Unit 1 as the model plant. Four accident studies were completed, resulting in recommendations for improvements in system design, emergency procedures, and operator training. Computer code improvements were an important by-product.

This report documents the methodology, computational framework, and results of facility accident analyses performed for the U.S. Department of Energy (DOE) Waste Management Programmatic Environmental Impact Statement (WM PEIS). The accident sequences pote...

PRAs often require quantification of the probabilities of various low-probability events, such as accident-initiating events and hardware-fault events. A two-stage Bayes/empirical Bayes data pooling procedure is presented for use in combining as many as f...

As an example for a low power research reactor a probabilistic safety assessment is undertaken for the 250 kW TRIGA Mark-II reactor Vienna. A major area of interest is the identification of different accident causes, the description of the following accident sequences and the influence of uncertainties. The usual technique in PSA ...

Fluorescein has been used as a tracer in aerosol studies for the detection and quantification of aerosols. This report summarizes a sequence of experiments conducted to confirm our procedure used for the recovery and detection of fluorescein from filters....

Jul 15, 2007 ... Knowledge of quantification techniques to assess the probability implications of a precursor event or a precursor sequence events. ...

... on the genetics of low pathogenic avian influenza viruses in North America, which use the migratory Northern ... and Quantification (Ip) Viral Genetics--Nucleotide Sequences and Viruses tha...

Four accident classes for fusion magnet systems with examples of upper bounds on probability of occurrence are described. Some potential accident sequences are discussed. The mechanical, thermal, and electrical aspects of magnet safety and reliability are...

Risk methodology is used to define experiments to be conducted in space which will help to construct and test the models required for accident sequence identification. The development of accident scenarios is based on the realization that whether damage o...

Psychophysiological factors are not uncommon terms in the aviation incident/accident investigation sequence where human error is involved. It is highly suspect that the same psychophysiological factors may also exist in the industrial arena where operator...

The purpose of the Severe Accident Sequence Analysis (SASA) Program was to investigate accident scenarios beyond the design basis. The primary objective of SASA was to analyze nuclear plant transients that could lead to partial or total core melt and eval...

After a characterization of the magnet system for the conceptual design of ITER previous failures of superconducting magnets are briefly reviewed. Possible accidents are discussed leading to the definition of so-called reference accident sequences. Since ...

Operator Action Event Trees for transient and LOCA initiated accident sequences at the Zion 1 PWR have been developed and documented. These trees logically and systematically portray the role of the operator throughout the progression of the accident. The...

The sequence of events and the consequences of the nuclear reactor accident at Chernobyl, USSR in April 1986 are reviewed. The background material in nuclear reactor and nuclear explosion physics required for understanding these events is extensively explained, and the differences between U.S. and Chernobyl-type reactors are pointed out.

For the investigation of the sequences of a hypothetical core meltdown accident, the primary interest is directed towards the integrity of the containment. In case of insecurity, the valid interests become then the probable time period of failure and the ...

This paper highlights the interim results of ASEP. ASEP is one of many programs sponsored by the Nuclear Regulatory Commission (NRC) to study various aspects of severe core damage accidents. The results of ASEP will ultimately focus on identifying the mos...

Calculations were performed to study the Ice-Condenser Containment Standard Problem for the NRC Containment Loads Working Group (CLWG). This problem is based on a TMLB' accident sequence. TMLB' denotes a transient-initiated accident in which there is tota...

The basis for fission product source term research in LOFT to support the NRC Severe Accident Research Program is presented. Probabilistic risk assessments are reviewed to identify risk-dominant accident sequences and an overview of source term research i...

Accidents hardly ever happen without warning. The combination, or sequence, of failures and mistakes that cause an accident may indeed be unique but the individual failures and mistakes rarely are. In the USA in 1974 the crews on two different aircraft mi...

Thermodynamic accident analyses have been performed with computer simulation models to investigate core heatup sequences, sensitivity analyses, power variations, anticipated transients without scram, and core displacement considerations for probabilistic ...

The purpose of the advanced reactor program is to provide NRC with a comprehensive data base essential to defining key safety issues, understanding the controlling accident sequences, verifying the complex computer models used in accident analysis and lic...

...the Integrated Safety Analysis summary, remain available and reliable, in an accident sequence evaluated in the Integrated Safety Analysis, to perform their function...the Integrated Safety Analysis summary, remains available...nuclear criticality accident, and has been in...

The Integrated Reliability and Risk Analysis System (IRRAS) is a state-of-the-art, microcomputer-based probabilistic risk assessment (PRA) model development and analysis tool to address key nuclear plant safety issues. IRRAS is an integrated software tool that gives the user the ability to create and analyze fault trees and accident sequences using a ...

The Integrated Reliability and Risk Analysis System (IRRAS) is a state-of-the-art, microcomputer-based probabilistic risk assessment (PRA) model development and analysis tool to address key nuclear plant safety issues. IRRAS is an integrated software tool that gives the user the ability to create and analyze fault trees and accident sequences using a ...

The significance of iodine for source term quantification has been studied by investigating its chemical behavior under the prototypical conditions of a hypothetical severe accident within the containment. As a result, some computer codes were developed and their validation is currently under way. The loss-of-fluid test (LOFT) program was one of the most ...

The Integrated Reliability and Risk Analysis System (IRRAS) is a state-of-the-art, microcomputer-based probabilistic risk assessment (PRA) model development and analysis tool to address key nuclear plant safety issues. IRRAS is an integrated software tool that gives the user the ability to create and analyze fault trees and accident sequences using a ...

The Integrated Reliability and Risk Analysis System (IRRAS) is a state-of-the-art, microcomputer-based probabilistic risk assessment (PRA) model development and analysis tool to address key nuclear plant safety issues. IRRAS is an integrated software tool that gives the user the ability to create and analyze fault trees and accident sequences using a ...

The safety analysis and risk assessment of a Tokamak Test Reactor is approached by an iterative, probabilistic, system study methodology, jointly developed by ENEA and CEA. The first part of this methodology consists of a safety related functional analysis of the plant. That is developed in a quite systematic and exhaustive way, aiming at the identification of all the process functions and their ...

This study describes the predicted response of Unit One at the Browns Ferry Nuclear Plant to a postulated loss of decay heat removal (DHR) capability following scram from full power with the power conversion system unavailable. In accident sequences witho...

A computer algorithm has been developed and implemented to search the Sequence Coding and Search System Licensee Event (LER) database for failures or conditions common to Accident Sequence Precursor (ASP) events. Use of the algorithm has greatly improved the efficiency and timeliness in identifying potential ASP events and, by focusing ...

The TQUV (Transient-induced scram, Power Conversion System Unavailable, High Pressure (HPCI, RCIC) and Low Pressure (RHR, Core Spray) injection systems unavailable) accident sequence has been shown to be among the dominant accident sequences in almost all...

This paper summarizes the Oak Ridge National Laboratory (ORNL) report Loss of DHR Sequences at Browns Ferry Unit One - Accident Sequence Analysis (NUREG/CR-2973). The Loss of DHR investigation is the third in a series of accident studies concerning the BW...

The methodological framework and program plan for systematic quantification and propagation of uncertainties in radiological source terms for light water reactors are presented. The QUASAR methodology is based on detailed sensitivity analysis of the Source Term Code Package (STCP), followed by a systematic uncertainty analysis on the most sensitive parameters/variables, and ...

This report documents the results of the second phase of parameter quantification by the flammable gas expert panel. This second phase is focused on the analysis of flammable gas accidents in the Hanford Site double-shell tanks. The first phase of parameter quantification, performed in 1997 was focused on the analysis of Hanford ...

Severe accident management can be defined as the use of existing and/or alternative resources, systems and actions to prevent or mitigate a core-melt accident. For each accident sequence and each combination of strategy, there may be several options available to the operator; and each involves phenomenological and ...

Severe accident management can be defined as the use of existing and/or alternative resources, systems and actions to prevent or mitigate a core-melt accident. For each accident sequence and each combination of strategies there may be several options available to the operator; and each involves phenomenological and ...

In this paper, a simple analytical code, QUASAR, is developed to analyze the phenomena related to severe subassembly accidents, such as a total instantaneous blockage event for a subassembly inlet. The code models failed and neighboring subassemblies, focusing mainly on the thermal consequences and the propagation potential of the accidents. The prediction ...

This paper presents a method for capturing the uncertainty expressed by an Hazard Analysis (HA) expert team when estimating the frequencies and consequences of accident sequences and provides a sound mathematical framework for propagating this uncertainty to the risk estimates for these accident sequences. The ...

The technology of thermal hydraulic aspects of the transition phase accident sequence in liquid metal fast breeder reactors has been reviewed. Previous analyses of the transition phase accident sequence have been reviewed and the current understanding of major thermal hydraulic phenomenology has been assessed. As a ...

An expert system was developed with the intent to provide real-time information about an accident to an operator who is in the process of diagnosing and bringing that accident under control. Explicit use was made of probabilistic risk analysis techniques and plant accident response information in constructing this system. The expert ...

A calculational procedure for the Station Blackout Severe Accident Sequence at Browns Ferry Unit One has been repeated with plant-specific application to one of the Peach Bottom Units. The only changes required in code input are with regard to the primary continment concrete, the existence of sprays in the secondary containment, and the size of the ...

Probabilistic risk assessment (PRA) analyses have indicated the transient-initiated loss of vessel-water injection (TQUV sequence) to be a dominant accident scenario for BWR plants. The PRA studies assumed the low-capacity injection systems to be unimportant in severe accidents. The results of a Severe Accident ...

This report describes a computer program package that aids in assessing the impact of floods on risk from nuclear power plants. The package consists of two distinct computer programs: ESP and NOAH. The ESP program improves the efficiency of a flood analysis by screening accident sequences and identifying accident ...

Winter weather can be a significant cause of road traffic accidents. This paper uses UKCIP climate change scenarios and a temporal analogue to investigate the relationship between temperature and severe road accidents in the West Midlands, UK. This approach also allows quantification of the changes in the severity of the winter season ...

This work presents a quantitative assessment of the impact that the emergency operating instructions (EOIs) of operating nuclear power plants may have on the frequency of severe accident sequences. Frequencies of such sequences were calculated based on the operator actions required by the EOIs of a reference BWR plant and compared to ...

The MELCOR severe accident code version 1.8.4QK has been employed to calculate the timing of events and source terms released into the environment for several hypothetical severe accidents as Unit 1 of the Juragua VVER 440-213 plant, located near Cienfuegos, Cuba. Different severe accidents were simulated, and results from two of them ...

In support of the US Nuclear Regulatory Commission (NRC) Accident Management Research Program, the availability of instruments to supply accident management information during a broad range of severe accidents is evaluated for a pressurized water reactor with a large dry containment. Results from this evaluation include the following: ...

The purpose of this project was to combine presently available advanced computer modeling techniques for reconstructing a crash sequence to the development of methods for determining occupant contact velocities, impact forces and occupant responses in pas...

The goal of this work is the investigation of the influence of different accident management strategies on the thermal-hydraulics in the containment during a Large Break Loss of Coolant Accident with a large containment leak from the beginning of the accident. The increasing relevance of terrorism suggests a closer look at this kind of ...

Background/AimsRecently, next-generation sequencing-based technologies have enabled DNA methylation profiling at high resolution and low cost. Methyl-Seq and Reduced Representation Bisulfite Sequencing (RRBS) are two such technologies that interrogate methylation levels at CpG sites throughout the entire human genome. With rapid reduction of ...

The source terms of an unmitigated anticipated transient without scram (ATWS) sequence at Kuosheng nuclear power plant were quantified using MAAP3.0B. The plant analyzed is a General Electric designed boiling water reactor (BWR) 6 enclosed in a MARK III containment. Two different ATWS scenarios were considered. In one case (low pressure), it was assumed that the automatic ...

An assessment has been made of the impact on societal risk of Class 3-8 accident sequences as defined by Appendix D to 10 CFR50. The present analysis concentrates on a pressurized water reactor and utilizes realistic assumptions when practical. Conclusions are drawn as to the relative importance of the analyzed accidents and their ...

Some of the coolant-cladding interactions that can take place during the design basis loss-of-coolant accident and the Three Mile Island loss-of-coolant accident are analyzed. The physical manifestations of the interactions are quite similar, but the time sequences involved can cause very different end results. These results are ...

An international analysis exercise has been organized to evaluate the ability of nuclear reactor severe accident computer codes to predict the TMI-2 accident sequence and core damage progression during the first 300 minutes of the accident. A required bou...

Information is presented concerning comments on reactor safety by governmental agencies and civilian organizations; reactor safety study methodology; consequence model; probability of accident sequences; and various accident conditions.

Knowledge and analysis methods of severe accidents at nuclear power plants (NPP) and of subsequent response of primary system and containment have been developed in last few years to the extent that realistic source tems of the specified accident sequence...

A statistical review is presented of 147 major helicopter fire accidents that occurred during an eight-year period. Ninety percent of fires in major accidents erupt on or immediately after the initial impact of the crash sequence. In 48% of the 106 surviv...

The purpose of this work is to use the results of the Savannah River Site K-Reactor Probabilistic Safety Assessment to determine the accident sequences and source terms for beyond design basis accidents. Additionally, the methodology necessary to allow the Reactor Accident Program to incorporate this information is ...

The purpose of this work is to use the results of the Savannah River Site K-Reactor Probabilistic Safety Assessment to determine the accident sequences and source terms for beyond design basis accidents. Additionally, the methodology necessary to allow the Reactor Accident Program to incorporate this information is ...

This paper presents a containment failure mode analysis during a spectrum of postulated degraded core accident sequences in a typical 1000-MW(e) boiling water reactor (BWR) with a Mark-I wetwell containment. Overtemperature failure of containment electric penetration assemblies (CEPAs) has been found to be the major failure mode during such ...

This volume comprises two appendixes: Chemical source terms for low-level mixed waste accidents, and radionuclide releases from facility accidents (HLW, LLW, LLMW(alpha and nonalpha)).

Recent work to identify the most likely beyond design-basis-accident (DBA) sequences which could occur in US commercial pressurized water reactors (PWRs) is summarized. These are defined here as postulated sequences in which all events have been observed separately in US reactors. Further, they involve an initiating failure and one or ...

In risk assessments, a primary objective is to determine the frequency with which a collection of initiating and basic events, E{sub e} leads to some undesired top event, T. Uncertainties in the occurrence rates, x{sub t}, assigned to the initiating and basic events cause uncertainty in the top event frequency, z{sub T}. The quantification of the uncertainty in z{sub T} is an ...

For many years, study of whole-core transients and accidents in fast reactors has been a major element of safety research and development programs in the US. Numerous models and computer codes have been developed and validated for use in these studies. Historically, emphasis has been placed on describing the core disruptive accident, but more recently ...

The Events and Causal Factors (E and CF) chart (or diagram) depicts in logical sequence the necessary and sufficient events and causal factors for accident occurrence. It can be used not only to analyze the accident and evaluate the evidence during investigation, but also can help validate the accuracy of preaccident systems analyses. ...

Most investigations of core meltdown scenarios in liquid metal fast breeder reactors (LMFBRs) have focused on accidents resulting from unprotected transients. In comparison, protected accidents which may lead to loss of core coolability and subsequent meltdown have received considerably less attention until recently. The sequence of ...

This paper describes recent analyses performed by the BWR Severe Accident Technology (BWRSAT) Program at Oak Ridge National Laboratory to estimate the release of debris from the reactor vessel for the unmitigated short-term station blackout accident sequence. Calculations were performed with the BWR Severe Accident ...

This report contains the Appendices for the Analysis of Accident Sequences and Source Terms at Waste Treatment and Storage Facilities for Waste Generated by the U.S. Department of Energy Waste Management Operations. The main report documents the methodology, computational framework, and results of facility accident analyses performed ...

Above-core structures can provide a significant heat sink during a degraded core accident. To determine the extent to which the structures affect an accident, a TRAC-PF1 calculation for the Surry pressurized water reactor was performed. The accident sequence was a total loss of feedwater with failure of the ...

Boiling water reactors (BWRs) incorporate many unique structural features that make their expected response under severe accident conditions very different from that predicted in the case of pressurized water reactor accident sequences. The effect of the BWR procedural and structural differences upon the progression of a severe ...

This study describes the predicted response of Unit One at the Browns Ferry Nuclear Plant to a postulated complete failure to scram following a transient occurrence that has caused closure of all Main Steam Isolation Valves (MSIVs). This hypothetical event constitutes the most severe example of the type of accident classified as Anticipated Transient Without Scram (ATWS). ...

This paper describes a safety analysis of a transfer process for high-level radioactive and toxic waste. The analysis began with a hazard assessment that used elements of What If, Checklist, Failure Modes and Effects Analysis, and Hazards and Operability Study (HAZOP) techniques to identify and rough-in accident sequences. Based on this preliminary ...

Risks associated with power generation must be identified to make intelligent choices between alternate power technologies. Radionuclide air stack emissions for a single coal plant and a single nuclear plant are used to compute the single plant leukemia incidence risk and total industry leukemia incidence risk. Leukemia incidence is the response variable as a function of radionuclide bone dose for ...

An investigation has been made of various accident sequence which may occur following a complete loss of offsite and onsite ac power at a Boiling Water Reactor nuclear power plant. The investigation was performed for the Browns Ferry Nuclear Power Plant, ...

The report describes the results of a series of calculations conducted to investigate the response of BWR Mark III containments to short-term station blackout severe accident sequences. The BWR-LTAS, BWRSAR, and MELCOR codes were employed to conduct quant...

The report describes the results of a series of calculations conducted to investigate the response of BWR Mark II containments to short-term and long-term station blackout severe accident sequences. The BWR-LTAS, BWRSAR, and MELCOR codes were employed to ...

A sequence of aircraft accidents has been analyzed using an Internet freely available database. By means of the Allan Factor (AF) statistics, time-clustering phenomenon was detected in the sequence, and this indicates that at certain timescales the time dynamics of the events is not Poissonian but long-range correlated.

In order to establish a method of probabilistic safety analysis for passive safety features, the event-tree (E/T) of ULOF accident sequences in the early stage of accident progression was constructed for an 600 MWe LMFBR model plant equipped with passive ...

A chronology of the Chernobyl accident begins with the 1 a.m. reduction to half power on Friday, April 25, and reports significant events until all fires were extinguished at 5 a.m. on Saturday. Mathematical reconstruction derived some of the times. The sequence uses data from the Soviet report.