Probability accident

Despite its shortcomings, WASH-1400 provides at this time (1978) the most complete single picture of accident probabilities associated with nuclear reactors. The fault tree/event tree approach coupled with an adequate database is the best method available to quantify these probahililies. 

Interpreting PSA as any risk assessment using accident probabilities and consequences, government and industry have prepared many examples. These are discussed as Public Risk, Specialized Analyses, and Performance Improvement. 

Chapters 8 and 9 presented computer codes that are available for computer hazardous material release and transport. Many of these codes have been tested using controlled experiments with varying agreement depending upon the code s applicability to the phenomena. In the author s opinion, the accuracy of the consequence calculation is not much better than the calculation of accident probabilities. 

Risk analysis. The risk of accidents can be assessed in terms of two factors severity and probability of the accident. Severity is high if consequences of the accident to employees, the public, the environment, and the plant are significant. Severity is related to the amount and properties of hazardous (toxic, flammable, explosive) substances that can escape to the surroundings during the accident, and to the energy that is released during the accident. Probability is associated with the likelihood of the occurrence of unwanted chains of events and the time of development of undesired events starting from the disturbance. If the time... 

Type of accident Probability of occurrence Potential for fatalities Potential for economic loss... 

Accident probability design goals, U.S. Army production base modernization program, 48f... 

The next part of the procedure involves risk assessment. This includes a determination of the accident probability and the consequence of the accident and is done for each of the scenarios identified in the previous step. The probability is determined using a number of statistical models generally used to represent failures. The consequence is determined using mosdy fundamentally based models, called source models, to describe how material is ejected from process equipment. These source models are coupled with a suitable dispersion model and/or an explosion model to estimate the area affected and predict the damage. The consequence is thus determined. 

There are two proposed technologies that use accelerators. One is called accelerator-breeding, as it aims at converting fertile material (e.g., Th-232) into fissile fuel to be used elsewhere in a (conventional) reactor (Lecocq and Furukawa, 1994). This does not in itself reduce accident probabilities, and to achieve this, the reactors should be of the above-mentioned inherently safe type. 

Consumption of game or wildlife in Great Britain after the Chernobyl accident probably did not exceed the annual limits of intake (ALI)... 

Prepare a summary report include a discussion of the events prior to the accident, a description of the accident, probable causes, and actions to be taken to prevent a recurrence. 

Analysis on relationship of construction accident probability and safety training... 

Note These criteria are based on failure probability (not accident probability). The accident/risk-based criteria (e.g. from Def Stan 00-56 or MIL-STD-882) consider die probability of the consequence (i.e. the accident) of various types of hazards. It is in this aspect that the accident/risk-based approach is difficult to apply, because a system target can only be set after an accident risk is defined and the accident sequence is fully populated with the probability of each contributing cause/event. For more information, see Kritzinger (2005), Chapters 4 and 5. When considering the use of risk (i.e. die product of accident probability and accident severity), please do ke in mind ... 

GM21.A.3B(d)(4) para 3,7 For large commuter transport aircraft, history has shown that the accident probability due to all technical causes is 1 in lOmiUion flying hours (i.e. lE-7 per flight hour). 

Probit functions were evaluated as the most often used tools for determining the effects of major accidents, probably due to the fact that these functions are included in the EFFECTS software. Furthermore, it was determined that the values of the limits of acute toxicity are not always the same when applying different methods. For example the value of IDLH for chlorine differs in order of tens. The ERPG has the lowest difference in the values in the order of units. This can be caused by the absence of literature sources. 

Traffic accidents involve collisions between two or more vehicles and collisions with fixed objects. Traffic accidents rate depends onroad category, traffic density and road location (urban areas/ out of urban areas). Traffic accident probability is usually measured per one kilometre (2nd task category). 

Szwed, P., J.R. van Dorp, J.R.W. Merrick, T.A. Mazzuchi, and A. Singh (2006). A Bayesian paired comparison study for relative accident probability assessment with covariate information. European Journal of Operations Research 196, 157 177. 

Data on which to base accident analyses have been obtained from reports on the particulars of accidents that are filed by officials on the scene and those involved in subsequent investigations. Some of the data are based on actual measurements. Other data are derived by analysis of data and inferences based on a notion of how the accident probably progressed. Each accident report must be evaluated and converted to some basic characteristics, such as impact speed, character of the impacted mass, impact angle, nature of the impact surface, and the like. It is frequently necessary to obtain other accounts of an accident to aoss-check information. 

Most agree that one of the first major formal system safety efforts involved the Minuteman intercontinental ballistic missile (ICBM) program. A series of pre-Minuteman design-related silo accidents probably provided at least part of the incentive (U.S. Air Force 1987). 

As the nuclear ftiel recycle industry grows, the probability of a criticality accident will tend to grow proportionately unless current criticality safety control is improved. (Accident Probability < Probability per Plant times Number of Plants.) Optimum control of criticality safety requires an overview of the entire system. The relationships between the criticality safety philosophy, the criticality data, the use of the data, and various human Victors must be considered. Application of the foult tree analysis (FTA) methodology will permit identification of the important control foctors and their relationships, indication of what is required to reduce the accident probability per plant, and systematic evaluation of our current criticality safety position. FTA is not new but the application to criticality safety presented in this... 

Empirical probabilities are also used in working out certain accident probabilities. For example, if there have been ten accidents during one hundred shifts, then it is possible to express the probability of an accident on a given shift as... 

A formalized deductive technique that works backward from a defined accident to I identify and graphicaliy display combinations of equipment failure and operator error that can lead to the accident. Probabilities are tissigned to each failure and error and an overall probability for the event is determined. 

The NTSB report [2], although very detailed, does not name any of the actors in the long sequence of events which led to the accident, probably because legal action... 

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