While transferring the fourth ingot, a criticality excursion occurred, producing an energy release that either expelled the fourth ingot or prompted the operator to instinctively withdraw it, ending the excursion. It is sometimes referred to as a critical excursion, a critical power excursion, or a divergent chain reaction. An alternative criticality detection system was designed by adam kryskow and eric darois of rscs. Criticality is an important nuclear safety hazard in plants where fissile material is processed this includes fuel manufacture, handled or stored but is also an important consideration during defuelrefuel operations on nuclear reactor plant. Estimating the credible consequences of a potential criticality accident. The accident occurred at a facility which reprocessed for recovery highly enriched uranium in scrap material from fuel element production. Spent fuel handling, packaging, transfer, and storage systems must be designed to be maintained subcritical and to ensure that, before a nuclear criticality accident is possible, at least two unlikely, independent, and concurrent or sequential changes have occurred in the conditions essential to nuclear. The immediate result of a nuclear criticality accident is the production of an uncontrolled and unpredictable radiation source that can be harmful, even lethal, to people who are nearby. A criticality analysis is a systematic approach to evaluating potential risks, therefore consequences that can impact the business. Description of program or function criticality accidents and the characteristics of prompt power excursions are discussed. A brief history of nuclear criticality accidents in russia.
Criticality noun the noun criticality has 2 senses 1. The criticality accident that occurred on september 30, 1999 at a uranium processing plant in tokaimura was an unprecedented nuclear accident in japan, not only because it caused deaths of two workers due to radiation casualty but also because it called for evacuation and sheltering indoors to nearby residents. Bill clark recalls 1958 criticality accident and his upanddown life since then 81yearold bill clark poses for a picture on his back porch. Do not circulate federation of american scientists. The sequence of events the criticality accident took place in the conversion building of the jco uranium processing plant in tokai village in ibaraki prefecture. The criticality analysis has defined criteria that outlines the potential consequences so that they can be evaluated, categorised and prioritised. The relative importance of the contribution of each person is not intended by the ordering of names. The use of understatement is astounding, as when the table of criticality accidents lists the accidents involving harry daghlian and louis slotin, but neglects to include that fact that fatalities were involved. Any such event involves the unintended accumulation or arrangement of a critical mass of fissile material, for example enriched uranium or plutonium.
The nuclear facility safety program establishes and maintains the doe requirements for nuclear criticality safety. Oct 25, 2015 a criticality accident is an uncontrolled nuclear chain reaction. Then you may enjoy this technical analysis of 60 accidents where improper handling of fissile materials led to unexpected critical mass. Computational advances in criticality safety analysis 297. Mar 30, 2012 nuclear criticality training film, ukaea, 1969. Criticality safety specialists must demonstrate a working level knowledge of doestd 102792, hazard categorization and accident analysis techniques for compliance with doe order 5480. Enterprise assessments assessment of the y12 national security.
The experiment in progress at the time of the incident was one in a series designed to study criticality conditions of uraniumwater solutions in annular cylindrical containers. Simulation of criticality accident transients in uranyl nitrate solution with comsol multiphysics c. A tank containing uranium 93% u235 in sodium carbonate solution was being agitated by a stirrer. A criticality accident is an uncontrolled nuclear fission chain reaction. Historically, 1d and 0d approximations to accident related physics have been employed to analyze criticality excursion transients for particular geometries. Ipsn initiated experiments reproducing the criticality accident by divergence of a fissile solution of uranyl nitrate on the crac and silene installations. In addition, the company did not believe that a criticality accident was a credible event and there were no specific operator training requirements for criticality safety. There have been two tokaimura nuclear accidents at the nuclear facility at tokai, ibaraki. The first operator returned and transferred two more ingots to this same container, for a total plutonium mass of 10. On the safety side, it introduces the risk of criticality when regular water is used to refill a pool following an accident that partially drains it. Chateau cea models the transient criticality of uo 2 fuel rods array in an open cylindrical shipping cask, so that the water is able to expand thermal dilatation of water, void effect of vapor bubbles critex ukaeacea models the transient criticality of a fissile solution contained in an open cylindrical vessel with vertical walls, so that the solution is able to expand vertically. Reports, articles and other documents harvested from the office of scientific and technical information. Pdf on 30 september 1999, a criticality accident occurred at a uranium processing plant operated by jco in tokaimura, japan and the criticality. He also published an article on his blog, the blue flash, with additional information he uncovered while researching the piece.
Security complex y12 criticality accident alarm system caas in buildings 92042e. The exposure, which caused a high neutron radiation dose, led to death within three days despite prompt medical attention. On september 30, 1999, a criticality accident occured at the tokai nuclear fuel plant, tokaimura, ibaraki prefecture, japan. Wood river criticality accident, 1964 johnstons archive. Nhk japan broadcasting corporation has produced an important contribution to the english literature on the criticality accident, which occurred at the jco nuclear fuel processing facility in tokaimura, about 110 km northeast of tokyo. However, enhanced computing and multiphysics capabilities i. This system relies upon the emissions from shortlived activated materials from neutron interactions with the materials contained within a drm2nc geigermueller detector manufactured by mirion technologies and materials surrounding the detector. The accident was not directly caused by failures or malfunctions of hardware but. Our russian hosts accommodated this request by arranging a presentation by professor v. Criticality status, a milestone in the commissioning of a nuclear power plant criticality accident, an uncontrolled nuclear chain reaction nuclear criticality safety, the prevention of nuclear and radiation accidents resulting from an inadvertent, selfsustaining nuclear chain reaction. Criticality definition of criticality by the free dictionary. This is the first of two criticality accidents the other being the accident at tokaimura in japan in 1999 on which the iaea has now issued reports, and it is intended that the reports will contribute to preventing such accidents in the future.
Criticality safety requirements are based on the documented safety analysis required by 10 cfr 830, subpart b. Simulation of criticality accident transients in uranyl. For the anniversary of manhattan project scientist louis slotins fatal criticality accident, historian alex wellerstein has a discerning article in the new yorker, the demon core and the strange death of louis slotin. Sufficient detail is provided to enable the reader to understand the physical situation,the chemistry and material flow,and when available the administrative setting leading up to the time of the accident.
When a criticality accident occurs it can give off high levels of radiation in a. Criticality accident analysis working party on criticality. September 30, 1999, criticality accident at the tokai mura fuel cycle facility, to identify lessons learned that could be applied to u. Minimizing the consequences if a criticality accident were to occur. The death of louis slotin atomic heritage foundation. Kns photopaul efird the photo below shows the scene of the 1958 criticality at the y12 nuclear weapons plant. The philosophy of the regulator was that the system was safe if it was operated in accordance with the approved procedures.
It is sometimes referred to as a critical excursion or a critical power excursion and represents the unintentional assembly of a. Criticalities definition of criticalities by the free. Thirtyfour accidental power transients are described. Criticality s sciencebased approach to the extraction, refinement and formulation of highquality cbd products makes it well positioned in the market and presents a huge growth opportunity for both criticality and pyxus, said pieter sikkel, pyxus chairman, president and chief executive officer. A description of criticality accidents is presented along with a discussion of the characteristics of prompt power excursions. The potential consequences of a criticality accident can be considerable e. Each person made a necessary contribution to the final document. As nouns the difference between criticality and critical is that criticality is the state of being critical while critical is a critical value, factor, etc. Frolov of the nuclear safety division of the institute of physics and power engineering at obninsk during the august 1997 nuclear criticality safety course. A criticality accident is an uncontrolled nuclear chain reaction. The atomic energy commission, under its mandate from congress, reported all criticality and radiation accidents in the following documents. Formal criticality analysis, something other than a simple 15 ranking, allows reliability leaders to determine the leading characteristic that makes each asset critical, be that production throughput, maintenance cost, utilization rate, or safety impact, to ensure that reliability improvements are made based on risk rather than perception. The russian authorities requested urgent assistance from the iaea under the terms of the 1986 convention on assistance in the case of a nuclear accident or. Pdf update of the nuclear criticality slide rule for the emergency.
As a adjective critical is inclined to find fault or criticize. Comsol allow for a greater range of detail and flexibility in criticality transient simulations. On the financial side, it incurs the cost of having to continually monitor the chemistry of the spent fuel pool water and periodically make adjustments to maintain the proper concentration of. The story of chicago pile 1, the first atomic pile 1 of 2 duration. The criticality accident resulted when a solution of enriched uranyl nitrate accidentally surged from a geometrically safe section of the evaporator into. Criticality article about criticality by the free dictionary. Pevey1 1department of nuclear engineering, university of tennessee, knoxville, tn, usa 2y12 national security complex, safety analysis engineering, oak ridge, tn, usa abstract numerical analysis of criticality accident transients is used to characterize fission source term. Criticality accident study programs were started in france in 1967 in order to improve knowledge about accidents.
In each case, enough detail is given to visualize the physical situation, the cause or causes of the accident, the history and characteristics of the transient. Specifically, this safety guide provides recommendations on how. Criticality accident at tokai nuclear fuel plant japan. The man whose body was destroyed from the inside out. Theoretical studies of the transient criticality of irradiated fuel elements in a transport flask proceedings of the iscs87 p. Criticality accident alarm system modeling made easy with scale 6. A nuclear excursion of approximately 6 x 10 17 fissions occurred in a firstcycle product evaporator at a chemical processing plant. A brief history of nuclear criticality accidents in russia orau. Equipment criticality classification model based on ahp kadarsah suryadi heri setyanta industrial management research group department of industrial engineering bandung institute of technology jl. The release of energy as a result of accidentally producing a selfsustaining or divergent fission chain reaction. It is sometimes referred to as a critical excursion, critical power excursion, or divergent chain reaction. Pdf external doses in the environment from the tokaimura. Noun wikipedia criticality criticalities the state of being critical education a disposition for purposeful thinking and acting guided by criteria that are considered to be contextually appropriate and that are expected to result in positive outcomes related to the purpose.
In the workplace, nuclear criticality accidents last from a fraction of a second up to several. The doe detailed requirements for criticality safety are contained in section 4. This applies to operations involving fissile material outside of reactor cores in order to ensure criticality safety at all times. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. The workers followed jco operating manual guidance in this process but were unaware it was not approved by the sta. Nea1681 criticalityaccidents nuclear energy agency.
1264 1504 585 1086 481 261 70 1213 1245 1422 1401 1242 1017 161 1021 805 571 481 573 1050 1234 1064 1492 944 3 1013 454