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The 1950s, 1960s, and Onward
Published in Sidney Dekker, Foundations of Safety Science, 2019
A 1975 report labeled WASH-1400, The Reactor Safety Study (U.S. Nuclear Regulatory Commission, 1975) set out to calculate the risk associated with the operation of a nuclear power plant with the help of probabilistic risk assessment, which takes into account the likelihood as well as the severity of adverse events. To calculate the risk, the team modeled all kinds of possible accident scenarios in event trees. They concluded that the risk associated with the operation of 100 power plants was lower than the risk associated with other natural or man-made disasters such as airplane crashes (Keller & Modarres, 2005). After publication, the report was criticized for: The calculations;The handling of uncertainties;The risk comparisons which had been “prejudging an acceptable level of risk for nuclear energy” (p. 280).
The Pedigree
Published in Erik Hollnagel, Safety–I and Safety–II, 2014
By the late 1940s and early 1950s, reliability engineering had become established as a new and separate engineering field, which combined the powerful techniques of probability theory with reliability theory. This combination became known as probabilistic risk assessment (PRA), sometimes also called probabilistic safety assessment (PSA). PRA was successfully applied to the field of nuclear power generation where the WASH- 1400 ‘Reactor Safety Study’ became the defining benchmark. This study considered the course of events which might arise during a serious accident at a large modern Light Water Reactor, using a fault tree/event tree approach. The WASH-1400 study established PRA as the standard approach in the safety assessment of modern nuclear power plants, from where the practice gradually spread to other industries with similar safety concerns. The focus of PRA was, however, on the technology rather than on humans or the organisation.
Nuclear safety: some reasons why siting is important
Published in Stan Openshaw, Nuclear Power, 2019
Further reassurance can be offered by noting that even worst-case reactor accidents seem to be similar to other possible catastrophes and cataclysmic events that we all have to live with. The WASH 1400 report compares the risks of nuclear accidents to other remote events such as meteorite impacts on cities, earthquakes, aircraft crashes, dam failures, and fire. Typical frequency-casualty relationships are shown in Figure 1.1. According to the WASH 1400 report the risks of a 100 reactor power programme are far smaller than all other man-made events with similar numbers of casualties (see curve A). Indeed, it would seem that many cataclysmic events with a similar casualty potential as reactor accidents are in fact 1000 times, or more, more likely to occur.
Structural Ignorance of Expertise in Nuclear Safety Controversies: Case Analysis of Post-Fukushima Japan
Published in Nuclear Technology, 2021
Kohta Juraku, Shin-Etsu Sugawara
For example, the Safety Goals Policy Statement published by the USNRC in 1986 comprised qualitative and quantitative goals that attempted to provide an overall framework regarding the risks acceptable to individuals and society.30 It reflected the technical advancement of PRA since WASH-1400 as well as the growing needs for formulating a safety goal triggered by the Three Mile Island nuclear accident.31 Meanwhile, the United Kingdom’s approach is less prescriptive, with the principle of as-low-as-reasonably-practicable (ALARP) being applied along with two reference risk levels that conceptually demarcate decision space into three regions.32 While the conceptualization and application of ALARP in the United Kingdom goes back to the 1940s, the origin of societal discussion on acceptable/tolerable risk in the nuclear field consists in the public hearings regarding the siting of Sizewell-B in the early 1980s.33
Nuclear safety by numbers. Probabilistic risk analysis as an evidence practice for technical safety in the German debate on nuclear energy
Published in History and Technology, 2020
Stefan Esselborn, Karin Zachmann
Despite these objections, quantitative risk analyses continued to gain ground in West German reactor safety circles in the early 1970s, as an increasing number of publications and research projects attests. One reason for this was internal to science and technology: as more data, more sophisticated logical-mathematical models and more computing power became available, probabilistic approaches became state of the art internationally. The most visible sign of this was the Reactor Safety Study (WASH 1400), the first comprehensive probabilistic risk analysis of a nuclear power plant worldwide, conducted between 1972 and 1975 under the supervision of Norman Rasmussen for the USAEC.75 The Rasmussen study received intensive attention in almost all nations using nuclear energy. In spite of the very public controversies following its release, it generally provided an important boost to proponents of probabilistic approaches, whom it provided with a template and a proof of principle. However, in contrast for example to the French nuclear safety establishment, which welcomed Rasmussen’s results but did not undertake any work itself, in the FRG, WASH-1400 helped to coagulate already existing minor projects into a large-scale national research program.76 This divergence had at least partly political reasons. A major part of the attraction and ambition of the extensive West German risk research projects of the early 1970s had less to do with (global) technological progress than with the societal (and hence national) side of the nuclear safety. Between 1970 and 1975, minor regional protests against nuclear power plants transformed into a highly energized, nationwide mass movement, willing to resort to all kinds of legal and extra-legal means – much to the surprise and dismay of nuclear experts, as well as the Federal bureaucracy.77 Against this backdrop, the idea to ‘objectively prove’ the (relative) safety of nuclear power plants through the introduction of quantitative criteria looked more appealing than ever. It is therefore not surprising that some of the most enthusiastic proponents of PRA were to be found in the state bureaucracy.78