WASH-1400

"Rasmussen Report" redirects here. For the polling firm, see Rasmussen Reports.

WASH-1400, 'The Reactor Safety Study' was a report produced in 1975 for the Nuclear Regulatory Commission by a committee of specialists under Professor Norman Rasmussen. It is thus often referred to as the Rasmussen Report. The report is now considered obsolete (see the disclaimer to NUREG-1150) and it and similar studies are being replaced by the State-of-the-Art Reactor Consequence Analyses study.

Overview

WASH-1400 considered the course of events which might arise during a serious accident at a (then) large modern Light water reactor. It estimated the radiological consequences of these events, and the probability of their occurrence, using a fault tree/event tree approach. This technique is called Probabilistic Risk Assessment (PRA). The report concluded that the risks to the individual posed by nuclear power stations were acceptably small, compared with other tolerable risks. Specifically, the report concluded, using the methods and resources and knowledge available at the time, that the probability of a complete core meltdown is about 1 in 20,000 per reactor per year.

The study was peer-reviewed by the 'Lewis Committee' in 1977, which broadly endorsed the methodology as the best available, but cautioned that the risk figures were subject to large uncertainty.

The methods used were comparatively simple and overly-pessimistic by today's standards, and based on early understanding of key phenomenology. Following a period of intensive (and expensive) research and discussion, inspired in part by the Three Mile Island accident, WASH-1400 was replaced in due course first by NUREG-1150 and now by a new study being performed by the Nuclear Regulatory Commission called the State-of-the-Art Reactor Consequence Analyses (SOARCA)[1]. Specific Studies were also made of two plants at Zion and Indian Point - the so called Z/IP Study.

The PRA methodology became generally followed as part of the safety-assessment of all modern nuclear power plants. In the 1990s, all US nuclear power plants submitted PRAs to the NRC under the Individual Plant Examination program [2], and five of these were the basis for the 1991 NUREG-1150.

WASH-1400 is now NUREG-75/014.

Criticism and debate

A panel of scientists organized by the American Physical Society (APS) "found much to criticize" in the WASH-1400 report. The panel noted that fatality estimates had considered only deaths during the first 24 hours after an accident, although radioactive cesium released in an accident would remain active for decades, and could expose large populations to adverse effects. The APS reviewers argued that cancer, one of the most serious forms of illness resulting from a reactor accident, would not show up until years after the accident. The APS reviewers also criticized the report’s methods for predicting the performance of emergency cooling systems.

The Union of Concerned Scientists released a 150-page report critiquing the WASH-1400 report, and in June 1976, the House Subcommittee on Energy and Environment held hearings on the validity of the report's findings. As a result of these hearings, NRC agreed to have a review group examine the validity of the report's conclusions.

In 1978, the review group appointed by the NRC and led by Professor Harold Lewis of the University of California concluded that "the uncertainties in WASH-1400's estimates of the probabilities of severe accidents were in general, greatly understated".

See also

• Nuclear safety in the U.S.
• Nuclear power
• WASH-740 (1957)
• CRAC-II (1982)
• NUREG-1150 (1991)

External links

• Probabilistic Safety Assessment from Nuclear Tourist Summary
• Probabilities of injuries from nuclear power plants
• The Reliability Information Analysis Center (RIAC)
• The WASH-1400 Report