A design-basis event (DBE) is a postulated event used to establish the acceptable performance requirements of the structures, systems, and components, such that a nuclear power plant can withstand the event and not endanger the health or safety of the plant operators or the wider public. Similar terms are design-basis accident (DBA) and maximum credible accident.[1][2]
design-basis criticality: "A criticality accident that is the most severe design-basis accident of that type applicable to the area under consideration."
design-basis earthquake (DBE): "That earthquake for which the safety systems are designed to remain functional both during and after the event, thus assuring the ability to shut down and maintain a safe configuration."
design-basis explosion: "An explosion that is the most severe design-basis accident of that type applicable to the area under consideration."
design-basis fire: "A fire that is the most severe design-basis accident of this type. In postulating such a fire, failure of automatic and manual fire-suppression provisions shall be assumed except for those safety class items or systems that are specifically designed to remain available (structurally or functionally) through the event."
design-basis flood: "A flood that is the most severe design-basis accident of that type applicable to the area under consideration."
design-basis tornado (DBT): "A tornado that is the most severe design-basis accident of that type applicable to the area under consideration."
Circumstances like the 2011 Tōhoku earthquake and tsunami were not considered within the design basis of the plant, and so the resulting Fukushima I nuclear accidents were described using this terminology as "beyond design basis" or "non-design-basis".[4] However, some have claimed that the design basis for tsunami events at Fukushima was incorrect.[5]
Accidents caused by poor design, failure to follow listed safety procedures, or other forms of human error are not considered to be beyond-design-basis accidents. The terminology can be unclear, however, because a poorly handled design-basis accident can result in conditions beyond what was considered likely, causing a beyond-design-basis accident.[6] For this reason, some industry experts have criticized the use of design-basis terminology. The Three Mile Island accident and the Chernobyl disaster are examples of design-basis accidents becoming non-design-basis accidents because of design deficiencies, inadequate training, procedures inadequate for the conditions (TMI), failure to follow operating procedures (Chernobyl), and control room design shortfalls.[7]
Beyond-design-basis eventsedit
Beyond-design-basis events can reduce or eliminate the margin of safety of the structures, systems and components, possibly resulting in a catastrophic failure.[8]
The Fukushima Daiichi nuclear disaster was caused by a "beyond-design-basis event": the tsunami and associated earthquakes were more powerful than the plant was designed to accommodate. The plant withstood the earthquake but the tsunami overflowed the seawall.[9] Since then, the possibility of unforeseen beyond design basis events has been a major concern for plant operators.[10]
^Ungethuem, J.; Stokes, M. D. (PDF). Paul Scherrer Institut. Archived from the original (PDF) on 26 August 2011. Retrieved 7 February 2017.
^Rogovin, Mitchell (1980). Three Mile Island: A Report to the Commissioners and to the Public(PDF). Vol. 1. Washington, D.C.: United States Nuclear Regulatory Commission. p. 3. Retrieved 17 October 2021. Long before the accident at Three Mile Island, there was a high bravado quotient widespread throughout the industry and its regulators. Licensing procedures were not entirely adequate, giving rise to deficiencies in some plant designs. Operator training was totally inadequate for emergencies, and poorly monitored. Control rooms were often designed with precious little attention to the operators' needs. The lessons learned from malfunctions and mistakes at nuclear plants both here and abroad were never effectively shared within the industry.
^Todreas, Neil E. (1992). Nuclear Systems: Elements of Thermal Hydraulic Design. Vol. 2. CRC Press. p. 347.
^Fackler, Martin (1 June 2011). "Report Finds Japan Underestimated Tsunami Danger". The New York Times. Retrieved 18 August 2019.
^Declan Butler (21 April 2011). "Reactors, residents and risk". Nature. 472 (7344): 400–401. doi:10.1038/472400a. PMID 21525903. S2CID 4371109.
March 17, 2024
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A design basis event DBE is a postulated event used to establish the acceptable performance requirements of the structures systems and components such that a nuclear power plant can withstand the event and not endanger the health or safety of the plant operators or the wider public Similar terms are design basis accident DBA and maximum credible accident 1 2 Subtypes of DBEs are 3 design basis criticality A criticality accident that is the most severe design basis accident of that type applicable to the area under consideration design basis earthquake DBE That earthquake for which the safety systems are designed to remain functional both during and after the event thus assuring the ability to shut down and maintain a safe configuration design basis explosion An explosion that is the most severe design basis accident of that type applicable to the area under consideration design basis fire A fire that is the most severe design basis accident of this type In postulating such a fire failure of automatic and manual fire suppression provisions shall be assumed except for those safety class items or systems that are specifically designed to remain available structurally or functionally through the event design basis flood A flood that is the most severe design basis accident of that type applicable to the area under consideration design basis tornado DBT A tornado that is the most severe design basis accident of that type applicable to the area under consideration Circumstances like the 2011 Tōhoku earthquake and tsunami were not considered within the design basis of the plant and so the resulting Fukushima I nuclear accidents were described using this terminology as beyond design basis or non design basis 4 However some have claimed that the design basis for tsunami events at Fukushima was incorrect 5 Accidents caused by poor design failure to follow listed safety procedures or other forms of human error are not considered to be beyond design basis accidents The terminology can be unclear however because a poorly handled design basis accident can result in conditions beyond what was considered likely causing a beyond design basis accident 6 For this reason some industry experts have criticized the use of design basis terminology The Three Mile Island accident and the Chernobyl disaster are examples of design basis accidents becoming non design basis accidents because of design deficiencies inadequate training procedures inadequate for the conditions TMI failure to follow operating procedures Chernobyl and control room design shortfalls 7 Beyond design basis events editBeyond design basis events can reduce or eliminate the margin of safety of the structures systems and components possibly resulting in a catastrophic failure 8 The Fukushima Daiichi nuclear disaster was caused by a beyond design basis event the tsunami and associated earthquakes were more powerful than the plant was designed to accommodate The plant withstood the earthquake but the tsunami overflowed the seawall 9 Since then the possibility of unforeseen beyond design basis events has been a major concern for plant operators 10 See also editLists of nuclear disasters and radioactive incidentsReferences edit NRC Glossary Design basis accident United States Nuclear Regulatory Commission Retrieved 7 February 2017 Design basis accident European Nuclear Society Retrieved 7 February 2017 An Exceptional Nuclear Glossary nuclearglossary com Archived from the original on 7 September 2017 Retrieved 7 February 2017 NRC Glossary Beyond design basis accidents Retrieved 7 February 2017 Acton James M Hibbs Mark March 2012 Why Fukushima Was Preventable PDF Carnegie Endowment for International Peace Ungethuem J Stokes M D Overview of Beyond design Basis Accident Management with Particular Reference to Severe Accident Scenarios in German Pressurized Water Reactors PDF Paul Scherrer Institut Archived from the original PDF on 26 August 2011 Retrieved 7 February 2017 Rogovin Mitchell 1980 Three Mile Island A Report to the Commissioners and to the Public PDF Vol 1 Washington D C United States Nuclear Regulatory Commission p 3 Retrieved 17 October 2021 Long before the accident at Three Mile Island there was a high bravado quotient widespread throughout the industry and its regulators Licensing procedures were not entirely adequate giving rise to deficiencies in some plant designs Operator training was totally inadequate for emergencies and poorly monitored Control rooms were often designed with precious little attention to the operators needs The lessons learned from malfunctions and mistakes at nuclear plants both here and abroad were never effectively shared within the industry Todreas Neil E 1992 Nuclear Systems Elements of Thermal Hydraulic Design Vol 2 CRC Press p 347 Fackler Martin 1 June 2011 Report Finds Japan Underestimated Tsunami Danger The New York Times Retrieved 18 August 2019 Declan Butler 21 April 2011 Reactors residents and risk Nature 472 7344 400 401 doi 10 1038 472400a PMID 21525903 S2CID 4371109 Retrieved from https en wikipedia org w index php title Design basis event amp oldid 1185343037 Beyond design basis events, wikipedia, wiki, book, books, library,
