WASH-1400
Encyclopedia
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 "generated a storm of criticism in the years following its release". Several detailed critiques raised numerous questions about the study's assumptions, methodology, calculations, peer review procedures, and objectivity. 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.
. 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 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)http://www.nrc.gov/about-nrc/regulatory/research/soar.html. 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 plant
s. In the 1990s, all U.S. nuclear power plants submitted PRAs to the NRC under the Individual Plant Examination program http://www.nrc.gov/reading-rm/basic-ref/glossary/individual-plant-examination-ipe.html, and five of these were the basis for the 1991 NUREG-1150.
According to Table 6-3 on pg. 112 of WASH-1400, individual persons have a less than 1 in 5,000,000,000 (Tbl 6-3, pg. 112) chance of dying on a yearly basis from the operation of 100 nuclear power plants in the United States. This is less than yearly risk of being struck by lightning and being killed (1 in 20,000,000, Tbl 6-3, pg. 112), being in a fatal auto collision (1 in 3,000 chance of dying, Tbl 6-3, pg. 112), or any other accident risk mentioned in WASH-1400.
WASH-1400 is now NUREG-75/014.
(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 a 1978 report, 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".
In 1979, The NRC was forced to issue a policy statement in which it accepted numerous criticisms of WASH-1400 raised by the Lewis Committee, and it withdrew any endorsement of the executive summary.
Nuclear Regulatory Commission
The Nuclear Regulatory Commission is an independent agency of the United States government that was established by the Energy Reorganization Act of 1974 from the United States Atomic Energy Commission, and was first opened January 19, 1975...
by a committee of specialists under Professor Norman Rasmussen. It "generated a storm of criticism in the years following its release". Several detailed critiques raised numerous questions about the study's assumptions, methodology, calculations, peer review procedures, and objectivity. The report is now considered obsolete (see the disclaimer to NUREG-1150
NUREG-1150
NUREG-1150 is an improvement on WASH-1400 and CRAC-II using the results of plant-specific Probabilistic Risk Assessments...
) and it and similar studies are being replaced by the State-of-the-Art Reactor Consequence Analyses
State-of-the-Art Reactor Consequence Analyses
The State-of-the-Art Reactor Consequence Analyses is a study of nuclear power plant safety conducted by the Nuclear Regulatory Commission...
study.
Overview
WASH-1400 considered the course of events that might arise during a serious accident at a (then) large modern Light water reactorLight water reactor
The light water reactor is a type of thermal reactor that uses normal water as its coolant and neutron moderator. Thermal reactors are the most common type of nuclear reactor, and light water reactors are the most common type of thermal reactor...
. It estimated the radiological consequences of these events, and the probability of their occurrence, using a fault tree
Fault tree analysis
Fault tree analysis is a top down, deductive failure analysis in which an undesired state of a system is analyzed using boolean logic to combine a series of lower-level events...
/event tree
Event tree
Error tree is an inductive analytical diagram in which an event is analyzed using Boolean logic to examine a chronological series of subsequent events or consequences...
approach. This technique is called Probabilistic Risk Assessment
Probabilistic risk assessment
Probabilistic risk assessment is a systematic and comprehensive methodology to evaluate risks associated with a complex engineered technological entity ....
(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 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
Three Mile Island accident
The Three Mile Island accident was a core meltdown in Unit 2 of the Three Mile Island Nuclear Generating Station in Dauphin County, Pennsylvania near Harrisburg, United States in 1979....
, WASH-1400 was replaced in due course first by NUREG-1150
NUREG-1150
NUREG-1150 is an improvement on WASH-1400 and CRAC-II using the results of plant-specific Probabilistic Risk Assessments...
and now by a new study being performed by the Nuclear Regulatory Commission
Nuclear Regulatory Commission
The Nuclear Regulatory Commission is an independent agency of the United States government that was established by the Energy Reorganization Act of 1974 from the United States Atomic Energy Commission, and was first opened January 19, 1975...
called the State-of-the-Art Reactor Consequence Analyses (SOARCA)http://www.nrc.gov/about-nrc/regulatory/research/soar.html. 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
Nuclear safety
Nuclear safety covers the actions taken to prevent nuclear and radiation accidents or to limit their consequences. This covers nuclear power plants as well as all other nuclear facilities, the transportation of nuclear materials, and the use and storage of nuclear materials for medical, power,...
of all modern nuclear power plant
Nuclear power plant
A nuclear power plant is a thermal power station in which the heat source is one or more nuclear reactors. As in a conventional thermal power station the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity.Nuclear power plants are usually...
s. In the 1990s, all U.S. nuclear power plants submitted PRAs to the NRC under the Individual Plant Examination program http://www.nrc.gov/reading-rm/basic-ref/glossary/individual-plant-examination-ipe.html, and five of these were the basis for the 1991 NUREG-1150.
According to Table 6-3 on pg. 112 of WASH-1400, individual persons have a less than 1 in 5,000,000,000 (Tbl 6-3, pg. 112) chance of dying on a yearly basis from the operation of 100 nuclear power plants in the United States. This is less than yearly risk of being struck by lightning and being killed (1 in 20,000,000, Tbl 6-3, pg. 112), being in a fatal auto collision (1 in 3,000 chance of dying, Tbl 6-3, pg. 112), or any other accident risk mentioned in WASH-1400.
WASH-1400 is now NUREG-75/014.
Criticism and debate
A panel of scientists organized by the American Physical SocietyAmerican Physical Society
The American Physical Society is the world's second largest organization of physicists, behind the Deutsche Physikalische Gesellschaft. The Society publishes more than a dozen scientific journals, including the world renowned Physical Review and Physical Review Letters, and organizes more than 20...
(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
Union of Concerned Scientists
The Union of Concerned Scientists is a nonprofit science advocacy group based in the United States. The UCS membership includes many private citizens in addition to professional scientists. James J...
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 a 1978 report, the review group appointed by the NRC and led by Professor Harold Lewis
Harold Lewis
Harold Warren Lewis was an Emeritus Professor of Physics and former department chairman at the University of California, Santa Barbara...
of the University of California
University of California
The University of California is a public university system in the U.S. state of California. Under the California Master Plan for Higher Education, the University of California is a part of the state's three-tier public higher education system, which also includes the California State University...
concluded that "the uncertainties in WASH-1400's estimates of the probabilities of severe accidents were in general, greatly understated".
In 1979, The NRC was forced to issue a policy statement in which it accepted numerous criticisms of WASH-1400 raised by the Lewis Committee, and it withdrew any endorsement of the executive summary.
See also
- Nuclear safety in the U.S.
- Nuclear accidents in the United StatesNuclear accidents in the United StatesAccording to a 2010 survey of energy accidents, there have been at least 56 accidents near nuclear reactors in the United States . The most serious of these was the Three Mile Island accident in 1979...
- Nuclear powerNuclear powerNuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...
- WASH-740WASH-740WASH-740, "Theoretical Possibilities and Consequences of Major Accidents in Large Nuclear Power Plants" estimated maximum possible damage from a meltdown with no containment building at a large nuclear reactor. The report was published by the U.S...
(1957) - CRAC-IICRAC-IICRAC-II is both a computer code and the 1982 report of the simulation results performed by Sandia National Laboratories for the Nuclear Regulatory Commission...
(1982) - NUREG-1150NUREG-1150NUREG-1150 is an improvement on WASH-1400 and CRAC-II using the results of plant-specific Probabilistic Risk Assessments...
(1991)