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 ...

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-...

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...

...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....

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 ...

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

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...

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 ...

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 ...

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 ...

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, ...

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 ...

...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 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 ...

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 ...

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 reported in ...

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 ...

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 documentation includes a delineation of the required ...

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 ...

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.

The United States Nuclear Regulatory Commission is sponsoring an on-going safety research program to assess dominant risk events in boiling water reactors. As part of this program, a sequence event tree for a boiling water reactor anticipated transient wi...

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 ...

The document contains the appendices for the accident sequence analyses of internally initiated events for the Surry Nuclear Station, Unit 1. This is one of the five plant analyses conducted as part of the NUREG-1150 effort by the Nuclear Regulatory Commi...

The document contains the accident sequence analysis of internally initiated events for Grand Gulf, Unit 1 as it operates in the Low Power and Shutdown Plant Operational State 5 during a refueling outage. The report documents the methodology used during t...

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 ...

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 ...

The Accident Sequence Precursor Program reviews licensee event reports of operational events that have occurred at LWRs to identify and categorize precursors to potential severe core-damage accidents. Accident sequences considered in the study are those ...

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 ...

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 ...

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 ...

This report documents the initial planning, specification of objectives, uses of results, and plan of attack to be used in the Severe Accident Sequence Analysis Program at the Oak Ridge National Laboratory. A key aspect is the determination of timing of events and a method of displaying and tracking concurrent ...

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 ...

BWR-LACP has been a versatile tool for the ORNL SASA program. The development effort was minimal, and the code is fast running and economical. Operator actions are easily simulated and the complete scope of both reactor vessel and primary containment are modeled. Valuable insights have been gained into accident sequences. A Fortran version is under ...

Changes in the US NRC Accident Sequence Precursor program methods since the initial program evaluations of 1969-81 operational events are described, along with insights from the review of 1984-85 events. For 1984-85, the number of significant precursors was consistent with the number observed in 1980-81, dominant ...

The document contains the accident sequence analysis of internally initiated events for Grand Gulf, Unit 1 as it operates in the Low Power and Shutdown Plant Operational State 5 during a refueling outage. The report documents the methodology used during t...

The document contains the accident sequence analysis of internally initiated events for Grand Gulf, Unit 1 as it operates in the Low Power and Shutdown Plant Operational State 5 during a refueling outage. The report documents the methodology used during t...

The document contains the accident sequence analysis of internally initiated events for Grand Gulf, Unit 1 as it operates in the Low Power and Shutdown Plant Operational State 5 during a refueling outage. The report documents the methodology used during t...

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 ...

This paper summarizes a study of light water reactor event sequences which have been investigated for their potential to result in reactivity accidents with severe consequences. The study is an outgrowth of the concern which arose after the accident at Chernobyl and was recommended by the report of the US Nuclear ...

On April 26, 1986 the world's worst nuclear power plant accident occurred at the Unit 4 of the Chernobyl Nuclear Power Station in the USSR. This paper presents a discussion of the design of the Chernobyl Power Plant, the sequence of events that led to the accident and the damage caused by the resulting ...

In this paper we study the time-clustering behavior of sequences of car accidents, using data from a freely available database in the internet. The Allan Factor analysis, which is a well-suited method to investigate time-dynamical behaviors in point processes, has revealed that the car accident sequences are ...

A limited review is performed of the Severe Accident Risk Assessment for the Limerick Generating Station. The review considers the impact on the core-melt frequency of seismic- and fire-initiating events. An evaluation is performed of methodologies used for determining the event frequencies and their impacts on the plant components and ...

The purpose of this report is to describe the use of Probabilistic Risk (Safety) Assessment (PRA or PSA) at a Department of Energy (DOE) facility. PRA is a methodology for (i) identifying combinations of events that, if they occur, lead to accidents (ii) estimating the frequency of occurrence of each combination of events and (iii) ...

This report provides the results of work carried out in support of the US Nuclear Regulatory Commission Accident Management Research Program to develop a technical basis for evaluating the effectiveness and feasibility of current and proposed strategies for boiling water reactor (BWR) severe accident management. First, the findings of an assessment of the ...

This paper briefly describes the results of work carried out in support of the US Nuclear Regulatory Commission Accident Management Research Program to evaluate the effectiveness and feasibility of current and proposed strategies for BWR severe accident management. These results are described in detail in the just-released report Identification and ...

This paper briefly describes the results of work carried out in support of the US Nuclear Regulatory Commission Accident Management Research Program to evaluate the effectiveness and feasibility of current and proposed strategies for BWR severe accident management. These results are described in detail in the just-released report Identification and ...

This report provides the results of work carried out in support of the US Nuclear Regulatory Commission Accident Management Research Program to develop a technical basis for evaluating the effectiveness and feasibility of current and proposed strategies for boiling water reactor (BWR) severe accident management. First, the findings of an assessment of the ...

This volume presents the results of the initiating event and accident sequence delineation analyses of the LaSalle Unit II nuclear power plant performed as part of the Level III PRA being performed by Sandia National Laboratories for the Nuclear Regulatory Commission. The initiating event identification included a ...

The report describes the sequence of events culminating in a critical excrusion of the reactor and the dosimetric and medical consequences. One person died of radiation-induced injuries. (ERA citation 11:020009)

BWR-LACP has been a versatile tool for the ORNL SASA program. The development effort was minimal, and the code is fast running and economical. Operator actions are easily simulated and the complete scope of both reactor vessel and primary containment are ...

On April 26th 1986, the worst accident in the history of commercial nuclear power generation occurred at the Chernobyl Nuclear Power Station some 60 miles north of Kiev in the Ukraine. This article describes the sequence of events that occurred and the co...

This summary by the Nuclear Regulatory Agency describes how the sequence of certain events equipment malfunctions, design-related problems and worker errors led to a partial meltdown of the TMI��ë2 reactor core but only very small off��ësite releases of radioactivity.

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 ...

The containment response to a postulated core meltdown accident in a PWR Ice Condenser Containment and a BWR Mark III Containment was examined to see if the WASH-1400 containment failure mode judgment for the Surry large, dry containment and the Peach Bottom Mark I containment are likely to be appropriate for ice-condenser and Mark III plant designs. Using ...

IRRAS is a program developed for the purpose of performing those functions necessary to create and analyze a complete Probabilistic Risk Assessment(PRA). This program includes functions to allow the user to create event trees and fault trees, to define accident sequences and basic event failure data, to solve ...

Probabilistic Risk (Safety) Assessment (PRA or PSA) is an analytic methodology for identifying the combination of events that, if they occur, lead to accidents. Accidents are defined as those events causing loss or injury to people, property, or the environment. PRA also provides a method for estimating the ...

A probabilistic risk assessment (PRA) approach is proposed to be used to scrutinize selection of accident sequences. A technique is described in this Licensing Topical Report to identify candidates for Design Basis Accidents (DBAs) utilizing the risk assessment results. As a part of this technique, it is proposed that ...

A sequence event tree for a boiling water reactor anticipated transient without scram (ATWS) has been developed and quantified. Goal is to provide a logical representation of the systems that must respond to an ATWS, the required operator response to the event, operator actions that could be performed in response to multiple failures, ...

The purpose of this report is to conduct a limit scope risk assessment by generating event trees for the accident scenarios described in table 4-2 of the HEAF SAR, ref 1. Table 4-2 lists the postulated event/scenario descriptions for non-industrial hazards for HEAF. The event tree analysis decomposes ...

This report presents the thermal-hydraulic design criteria (THDC) developed for the tungsten neutron source (TNS). The THDC are developed for the normal operations, operational transients, and design-basis accidents. The requirements of the safety analyses are incorporated into the design criteria, consistent with the integrated safety management and the safety-by-design ...

This report summarizes the findings of the Accident Investigation Team (Team) assembled in response to a request from Pacific Gas and Electric Company (PG and E) to the US Department of Energy (DOE) to understand the events surrounding the electric shock of a worker at the PVUSA site in Davis, California and to provide recommendations to prevent such ...

As a part of the overall effort undertaken by Brookhaven National Laboratory (BNL) to review the GESSAR-II probabilistic risk assessment, an independent containment performance evaluation was performed using the containment event tree approach. This evaluation focused principally on those accident sequences which are initiated by ...

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 BWR 4 - MK I containment plant design. These studies, sponsored ...

Los Alamos Scientific Laboratory reactor safety groups have performed a detailed mechanistic analysis of a best-estimate composite sequence of events for the March 28, 1979, accident at the Three Mile Island - Unit 2 (TMI-2) nuclear reactor. One aspect of that study is analyzed: the core response to the calculated thermal hydraulic ...

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 ...

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 ...

Indian nuclear power program as of now is mainly based on Pressurized Heavy Water Reactors (PHWRs). Operating Procedures for normal power operation and Emergency Operating Procedures for operational transients and accidents within design basis exist for all Indian PHWRs. In addition, on-site and off-site emergency response procedures are also available for these NPPs. The ...

In present, the development and analysis of Accident Progression Event Trees (APETs) are performed in a manner that is computationally time consuming, difficult to reproduce and also can be phenomenologically inconsistent. One of the principal deficiencies lies in the static nature of conventional APETs. In the conventional event tree ...

SAS4A is a new code system which has been designed for analyzing the initial phase of Hypothetical Core Disruptive Accidents (HCDAs) up to gross melting or failure of the subassembly walls. During such postulated accident scenarios as the Loss-of-Flow (LOF) and Transient-Overpower (TOP) events, the relocation of the fuel plays a key ...

The SAS4A code system has been designed for the analysis of the initial phase of Hypothetical Core Disruptive Accidents (HCDAs) up to gross melting or failure of the subassembly walls. During such postulated accident scenarios as the Loss-of-Flow (LOF) and Transient-Overpower (TOP) events, the relocation of the fuel plays a key role in ...

The fundamental objective of the accident management program is to assure, in the event of a severe accident at a nuclear plant, that the effectiveness of personnel and equipment is maximized in preventing or mitigating the consequences of the accident. T...

The Committee on Interior and Insular Affairs conducted an informal review of the accident beginning on March 28, 1979 at the Three Mile Island Nuclear Power Plant. Officials of the Nuclear Regulatory Commission, plant operating personnel employed by General Public Utilities, and representatives of the reactor manufacturer, Babcock and Wilcox Company, related their activities ...

This study investigated 478 police accident reports from 9 states to examine and characterize rollover crashes involving ESC-equipped vehicles. The focus was on the sequence of critical events leading to loss of control and rollover, and the interactions between the accident, driver, and environment. Results show ...

Graphical presentations of human actions in incident and accident sequences have been used for many years. However, for the most part, human decision making has been underrepresented in these trees. This paper presents a method of incorporating the human decision process into graphical presentations of incident/accident ...

Boiling water reactors (BWRs) incorporate many unique structural features that make their expected response under accident conditions very different from that predicted in the case of pressurized water reactor accident sequences. Automatic main steam isolation valve (MSIV) closure as the vessel water level approaches the top of the ...

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 ...

The Nuclear Regulatory Commission`s (NRC`s) ongoing Accident Sequence Precursor (ASP) program uses probabilistic risk assessment (PRA) techniques to assess the potential for severe core damage (henceforth referred to simply as core damage) based on operating events. The types of operating events considered include ...

Safety is a crucial issue in densely sailed waterways. Traffic guidance systems (VTS) have proven to be valuable in this respect. The effectiveness of current systems and the benefits for improvements in navigation are addressed in this paper. Relevant incidents are analysed with a risk assessment tool (Accident Sequence Precursor method) developed for ...

This document contains the accident sequence analysis of internally initiated events for Grand Gulf, Unit 1 as it operates in the Low Power and Shutdown Plant Operational State 5 during a refueling outage. The report documents the methodology used during the analysis, describes the results from the application of the methodology, and ...

A historic meeting was held Aug. 25-29, 1986, in Vienna, Austria. A delegation of U.S.S.R. experts presented detailed information on the design characteristics of the RBMK-1000 type of reactor and their evaluation of all aspects of the Chernobyl accident, including causes, events, measured releases, mitigation efforts, response measures taken, atmospheric ...

Accidents and unscheduled events associated with non-nuclear energy resources and technology are identified for each step in the energy cycle. Both natural and anthropogenic causes of accidents or unscheduled events are considered. Data concerning these accidents are summarized. ...

While it would be very difficult to predetermine all of the actions required to mitigate the consequences of every potential severe accident for a nuclear power plant, development of additional guidance and training could improve the likelihood that the operating crew would implement effective sever-accident management measures. The US Nuclear Regulatory ...

This paper presents a QRA-based approach for assessing and evaluating the safety of installations handling explosive substances. Comprehensive generic lists of immediate causes and initiating events of detonation and deflagration of explosive substances as well as safety measures preventing these explosions are developed. Initiating events and ...

A quantitative data base for initiating events encountered during nuclear weapons handling is described. This data base was assembled from incident reports at the plant where the weapons are handled. The strengths and pitfalls of constructing such a data base are elaborated using examples encountered in the data. Insights gained into accident ...

Management of risk in complex domains such as aviation relies heavily on post-event investigations, requiring complex approaches to fully understand the integration of multi-causal, multi-agent and multi-linear accident sequences. The Event Analysis of Systemic Teamwork methodology (EAST; Stanton et al. 2008) ...

The history of high consequence accidents is rich with events wherein the actions, or inaction, of humans was critical to the sequence of events preceding the accident. Moreover, it has been reported that human error may contribute to 80% of accidents, if not more ...

This paper presents results from a Los Alamos National Laboratory Engineering and Safety Analysis Group assessment of the worse-case design-basis accident associated with the Clinton P. Anderson Meson Physics Facility (LAMPF)/Weapons Neutron Research (WNR) Facility. The primary goal of the analysis was to quantify the accident ...

This paper presents results from a Los Alamos National Laboratory Engineering and Safety Analysis Group assessment of the worse-case design-basis accident associated with the Clinton P. Anderson Meson Physics Facility (LAMPF)/Weapons Neutron Research (WNR) Facility. The primary goal of the analysis was to quantify the accident ...

This document contains a summarization of the results and insights from the Level 1 accident sequence analyses of internally initiated events, internally initiated fire and flood events, seismically initiated events, and the Level 2/3 risk analysis of internally initiated ...

The Reactor Safety Study (WASH-1400) predicted that Interfacing System Loss-of-Coolant Accidents (ISL) events were significant contributors to risk even though they were calculated to be relatively low frequency events. However, there are substantial uncertainties involved in determining the probability and consequences of the ISL ...

A methodology has been developed to extract generic risk-based information from probabilistic risk assessments (PRAs) of Westinghouse and Combustion Engineering (CE) pressurized water reactors (PWRs) and apply the insights gained to Westinghouse and Ce plants have not been subjected to a PRA. The available PRAs (five Westinghouse plants and one CE plant) were examined to identify the most ...

A methodology has been developed to extract generic risk-based information from probabilistic risk assessments (PRAs) of General Electric boiling water rectors and applying the insights gained to plants that have not been subjected to a PRA. The available risk assessments (six plants) were examined to identify the most probable, i.e., dominant accident ...

This paper presents the results and insights gained from MELCOR analyses of two severe accident scenarios, a Loss of Coolant Accident (LOCA) and a Station Blackout (TMLB) in Oconee, a Babcock & Wilcox (B&W) designed PWR with a large dry containment, and comparisons with Source Term Code Package (STCP) calculations of the same ...

This paper presents the results and insights gained from MELCOR analyses of two severe accident scenarios, a Loss of Coolant Accident (LOCA) and a Station Blackout (TMLB) in Oconee, a Babcock Wilcox (B W) designed PWR with a large dry containment, and comparisons with Source Term Code Package (STCP) calculations of the same ...

During 1989 the Nuclear Regulatory Commission (NRC) initiated an extensive program to carefully examine the potential risks during low power and shutdown operations. Two plants, Surry (a pressurized water reactor) and Grand Gulf (a boiling water reactor), were selected for study by Brookhaven National Laboratory and Sandia National Laboratories, respectively. The program objectives included ...

In this paper we present information that can be used in severe accident management by providing an improved understanding of the effects of water addition to a degraded core. This improved understanding is developed using a diagram showing a sequence of core damage states. Whenever possible, a temperature and a time after accident ...

In this paper we present information that can be used in severe accident management by providing an improved understanding of the effects of water addition to a degraded core. This improved understanding is developed using a diagram showing a sequence of core damage states. Whenever possible, a temperature and a time after accident ...

This paper summarizes an analysis of the movement of noble gases, iodine, and cesium fission products within the Mark-I containment BWR reactor system represented by Browns Ferry Unit 1 during a postulated accident sequence initiated by a loss of decay heat removal (DHR) capability following a scram. The event analysis showed that this ...

A safety analysis study has been applied to the Ignitor machine using Probabilistic Safety Assessment. The main initiating events have been identified, and accident sequences have been studied by means of traditional methods such as Failure Mode and Effect Analysis (FMEA), Fault Trees (FT) and Event Trees (ET). The ...

The Savannah River Laboratory (SRL) human factors group has been developing methods for analyzing nuclear reactor operator actions during hypothetical design-basis accident scenarios. The SRL reactors operate at a lower temperature and pressure than power reactors resulting in accident sequences that differ from those of power ...

The basis for securing nuclear safety is to prevent occurrence of accidents and to mitigate propagation of abnormal events or accidents to severe accidents. In practice, a nuclear power plant is designed and constructed so that abnormal events can be dete...

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 ...

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 ...

The Nuclear Safety Analysis Center (NSAC) of the Electic Power Research Institute is analyzing the Three Mile Island-2 accident. An early result of this analysis was a brief narrative summary, issued in mid-May 1979. The present report contains a revised version of that narrative summary, a highly detailed sequence of events, a ...

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...

Traditionally, probabilistic risk assessments (PRA) of severe accidents in nuclear power plants have considered initiating events potentially occurring only during full power operation. Some previous screening analyses that were performed for other modes of operation suggested that risks during those modes were small relative to full power operation. ...

A review of the Oconee-3 Probabilistic Risk Assessment (OPRA) was conducted with the broad objective of evaluating qualitatively and quantitatively (as much as possible) the OPRA assessment of the important sequences that are ''externally'' generated and lead to core damage. The review included a technical assessment of the assumptions and ...

The report describes the Chernobyl accident and its consequences for Denmark in particular. It was commissioned by the Secretary of State for the Environment. The event at the accident site, the release and dispersal of radioactive substances into the atm...

Information is presented concerning accident definition and use of event trees, event tree methodology, potential accidents covered by the reactor safety study, analysis of potential accidents involving the reactor core, and analysis of potential accidents not involving the ...

Accident management strategies that have the potential to maintain containment integrity and control or mitigate the release of radioactivity following a severe accident at a boiling water reactor with a Mark 2 type of containment are identified and evaluated. The strategies are referred to as containment and release strategies. Using information available ...

In the present paper, an accident occurred during a liquefied petroleum gas (LPG) tank filling activity has been taken into consideration. During the transfer of LPG from the source road tank car to the receiving fixed storage vessel, an accidental release of LPG gave rise to different final consequences ranging from a pool fire, to a fireball and to the catastrophic rupture ...

Anticipated Transients Without Scram (ATWS) accident analyses make part of the Safety Analysis Report of the European Pressurized water Reactor (EPR), covering Risk Reduction Category A (Core Melt Prevention) events. This paper deals with three of the most penalizing RRC-A sequences of ATWS caused by mechanical blockage of the ...

An analysis of the Soviet report on the accident at the Chernobyl unit 4 in April of 1986 examines the poorly conceived experiment, the human errors, and the lack of safety measures which contributed to the accident. The author reviews the sequence of events as presented by the Soviets at an international meeting, ...

A new methodology is developed for modeling a system's evolution to support decisionmaking on alternative actions which affect the system's evolution. The methodology is based upon the goal tree success tree method for hierarchal decomposition of the system's objective. The goal tree success tree structure is used to identify the system's objective and supporting functions and the ...

OBJECTIVE: The paper reviews community based epidemiological studies of injuries at school. It discusses their main findings in the light of a frame of analysis that emphasizes multidimensionality of causes, and in a Swedish context, where school injuries are legally regarded as occupational injuries. METHODS: A frame of analysis, inspired by research in the arena of occupational ...

The revolutionary reactor design, PIUS-600 as described in the Preliminary Safety Analysis Report (PSID) was subject to analyses consisting of Failure Modes. Effects and Criticality Analysis (FMECA), Hazards and Operability (HAZOP) analysis, and conventional engineering review of the stress, neutronics, thermal hydraulics, and corrosion. These results were integrated in the PIUS Intermediate Table ...

The revolutionary reactor design, PIUS-600 as described in the Preliminary Safety Analysis Report (PSID) was subject to analyses consisting of Failure Modes. Effects and Criticality Analysis (FMECA), Hazards and Operability (HAZOP) analysis, and conventional engineering review of the stress, neutronics, thermal hydraulics, and corrosion. These results were integrated in the PIUS Intermediate Table ...

Sensitivity studies based on Probabilistic Safety Assessments (PSAs) for a pressurized water reactor and a boiling water reactor are described. In each case human errors modeled in the PSAs were categorized according to such factors as error type, location, timing, and plant personnel involved. Sensitivity studies were then conducted by varying the error rates in each category and evaluating the ...

On April 26, 1986, the worst accident in the history of commercial nuclear power generation occurred at the Chernobyl Nuclear Power Station some 60 miles north of Kiev in the Ukraine. This paper describes the sequence of events that occurred and the consequences of the accident. There was extensive damage to the ...

One of the most important safety design issues for a hydrogen production system coupling with a high-temperature gas-cooled reactor (HTGR) is to ensure reactor safety against fire and explosion accidents because a large amount of combustible fluid is dealt with in the system. The Japan Atomic Energy Research Institute has a demonstration test plan of a hydrogen production ...

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Home News & Events Press Releases Events Speeches & Testimony Across the Board Transportation Safety Most Wanted List Safety Alerts Safety Recommendations Safety Studies Accident...

Home News & Events Press Releases Events Speeches & Testimony Across the Board Transportation Safety Most Wanted List Safety Alerts Safety Recommendations Safety Studies Accident...

This report summarizes the results from MELCOR calculations of severe accident sequences in the ABWR and presents comparisons with MAAP calculations for the same sequences. MELCOR was run for two low-pressure and three high-pressure sequences to identify the materials which enter containment and are available for ...

Traditionally, probabilistic risk assessments (PRA) of severe accidents in nuclear power plants have considered initiating events potentially occurring only during full power operation. Some previous screening analyses that were performed for other modes of operation suggested that risks during those modes were small relative to full power operation. ...

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 without DHR capability, the residual heat removal (RHR) system functions of pressure suppression pool ...

Source 16:37:53.444 ME-3 Ignition Command -6.566 GPC 37:53.564 ME-2 Ignition Command -6.446 GPC 37:53.684 ME-1 Ignition Command -6.326 GPC 38:00.010 SRM ...

An important goal of the US DOE reactor development program is to conceptualize advanced safety design features for a demonstration Sodium Fast Reactor (SFR). The treatment of severe accidents is one of the key safety issues in the design approach for advanced SFR systems. It is necessary to develop an in-depth understanding of the risk of severe accidents ...

Inherent in the design of DOE reactors under review are many features which provide significant protection against the likelihood of TMI-type accidents. In addition, other features in the design or operating characteristics would tend to limit or reduce the consequences of the accident. Some of these features were discussed earlier in this report. However, ...

A general temperate latitude cyclonic rainstorm model is presented which describes the effects of washout and runoff on consequences of atmospheric releases of radioactive material from potential nuclear reactor accidents. The model treats the temporal and spatial variability of precipitation processes. Predicted air and ground concentrations of radioactive material and ...

Since 1980, a series of accident studies concerning the Boiling Water Reactor (BWR) - MARK I containment plant design have been conducted by the Severe Accident Sequence Analysis (SASA) program at the Oak Ridge National Laboratory (ORNL). The SASA program is sponsored by Containment Systems Research Branch, Division of ...

The Nuclear Regulatory Commission (NRC) approves new package designs for shipping fissile quantities of UF{sub 6}. Currently there are three packages approved by the NRC for domestic shipments of fissile quantities of UF{sub 6}: NCI-21PF-1; UX-30; and ESP30X. For approval by the NRC, packages must be subjected to a sequence of physical tests to simulate transportation ...

Risk analysis is being increasingly applied in the chemical process industries to assess health and safety problems and to improve loss-prevention capabilities. Many of the tools used in risk analysis to identify and evaluate accident sequences can also provide information for solving engineering and design problems. Systems-analysis techniques such as ...

The BWR-LTAS code was developed by the SASA program at Oak Ridge National Laboratory for the detailed study of specific accident sequences at Browns Ferry Unit One: station blackout, small break LOCA outside primary containment, loss of decay heat removal, loss of vessel water injection, and anticipated transient without scram. The primary use of the code ...

Reentry vehicles (RVs) carrying warheads from ballistic missiles must be carefully balanced with the warhead in situ to prevent wobble as the RVs enter the earth`s atmosphere to prevent inaccuracy or loss of the warhead. This balancing is performed on a dynamic balancing machine that rotates the RV at significant angular velocities. Seizure of the spindle shaft of the machine could result in rapid ...

Sandia National Laboratories (SNL) has developed a package for the on-site. transport of chemical munitions for the US Army. This package was designed to prevent the release of lethal quantities of chemical agents during transportation of munitions to the demilitarization facilities on-site. The packaging prevents auto-ignition of the munitions by limiting the thermal and structural assault on the ...

Sandia National Laboratories (SNL) has developed a package for the on-site. transport of chemical munitions for the US Army. This package was designed to prevent the release of lethal quantities of chemical agents during transportation of munitions to the demilitarization facilities on-site. The packaging prevents auto-ignition of the munitions by limiting the thermal and structural assault on the ...

In response to the damage which occurred during the Three Mile Island nuclear accident, the Nuclear Regulatory Commission (NRC) has implemented a Probabilistic Risk Assessment (PRA) program to evaluate the safety of nuclear power facilities during events with a low probability of occurrence. The PRA can be defined as a mathematical technique to identify ...

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 ...

This manuscript describes in detail the LPG accident occurred in Viareggio on June 2009 and its modeling. The accident investigation highlighted the uncertainty and complexity of assessing and modeling what happened in the congested environment close to the Viareggio railway station. Nonetheless, the analysis allowed comprehending the ...

This paper presents a new approach for evaluating accident management options using containment event trees (CETs) developed during individual plant examinations (IPEs) for a Combustion Engineering-type 1050-MW(electric) pressurized water reactor. A station blackout sequence is used here because it is identified as one of the most ...

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 ...

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 ...

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 paper presents a new approach for developing and assessing severe accident management strategies under uncertainty in nuclear power plants. The strategy of flooding the reactor cavity during the TMLB{prime} sequence as a means to prevent vessel breach is used as an example. The modeling of complex decision problems, such as those encountered in severe ...

The Three Mile Island (TMI)-2 accident provides the only data for a full-scale, integrated water reactor facility during a severe accident. The data from this accident has been, and is being, collected, reviewed, and cataloged. The data will be placed in structured data bases. To date, three data bases have been completed: Plant ...

Studies and operating experience suggest that the risk of severe accidents during low power operation and/or shutdown (LP/S) conditions could be a significant fraction of the risk at full power operation. Two studies have begun at the Nuclear Regulatory Commission (NRC) to evaluate the severe accident progression from a risk perspective during these ...

Nuclear power reactor safety in the United States is about to enter a new era -- an era of risk- based management and risk-based regulation. First, there was the age of `prescribed safety assessment,' during which a series of design-basis accidents in eight categories of severity, or classes, were postulated and analyzed. Toward the end of that era, it was recognized that ...

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 ...

This report identifies and assesses accident management strategies which could be important for preventing containment failure and/or mitigating the release of fission products during a severe accident in a BWR plant with a Mark III type of containment. Based on information available from probabilistic risk assessments and other existing severe ...

This report identifies and assesses accident management strategies which could be important for preventing containment failure and/or mitigating the release of fission products during a severe accident in a BWR plant with a Mark 1 type of containment. Based on information available from probabilistic risk assessments and other existing severe ...

...the event as either a launch accident or launch incident, and must...the consequences of a launch accident, launch incident or other...investigating the cause of a launch accident, launch incident or other...adopt preventive measures for avoiding recurrence of the event....

Analysis is made of many postulated accidents within the NS Savannah power plant. The accidents include reactivity accidents, mechanical accidents, and miscellaneous accidents. It is concluded that there is no appreciable hazard to the public or the crew even in the ...

The temperature response of three generic surface models in each of three locations in an ice condenser containment building were calculated assuming a hydrogen deflagration event and using the HECTR code. The intent of using the three generic surfaces was to conservatively represent surfaces of various types of safety equipment. Analyses were performed for four ...

This report is a qualitative assessment of the public and worker risk involved with the operation of a liquefied natural (LNG) vehicle refueling facility. This study includes facility maintenance and operations, tanker truck delivers and end-use vehicle fueling; it does not treat the risks of LNG vehicles on roadways. Accident initiating events are ...

The steps involved to incorporate parameter uncertainty into the Nuclear Regulatory Commission (NRC) accident sequence precursor (ASP) models is covered in this paper. Three different uncertainty distributions (i.e., lognormal, beta, gamma) were evaluated to Determine the most appropriate distribution. From the evaluation, it was Determined that the ...

The method of moments is applied to precisely determine the mean values of three importance measures: risk reduction, partial derivative, and variance reduction. Variance reduction calculations, in particular, are significantly improved by eliminating the imprecision associated with Monte Carlo estimates. The three importance measures are extended to permit analyses of the relative importance of ...

The method of moments is applied to precisely determine the mean values of three importance measures: risk reduction, partial derivative, and variance reduction. Variance reduction calculations, in particular, are significantly improved by eliminating the imprecision associated with Monte Carlo estimates. The three importance measures are extended to permit analyses of the relative importance of ...