The International Nuclear and Radiological
Event Scale INES Denis Flory Deputy Director General Department of Nuclear Safety and Security International Atomic Energy Agency
What is INES? <ul><li>International event
rating scale with the aim of communicating to the public the safety significance of nuclear and radiological events </li></ul><ul><li>Provides criteria for rating any event associated with the transport, storage and use of radioactive material </li></ul><ul><li>Jointly developed in 1990 by the IAEA and OECD/NEA </li></ul><ul><li>INES communication network comprises over 70 Member States </li></ul>
Using the INES Scale: three
criteria <ul><li>Impact on people and environment </li></ul><ul><ul><li>Activity released or dose received </li></ul></ul><ul><li>Impact on radiological barriers and controls (former on-site impact) </li></ul><ul><ul><li>The severity of the event inside the site of a facility and the potential harm to the public </li></ul></ul><ul><li>Degradation in “Defence in Depth” </li></ul><ul><ul><li>Looking at failures in safety provisions to determine how close the event was to causing actual consequences </li></ul></ul>
General Description of Criteria At
Level 4/5: fuel damage and radiological barrier damage occurs At Level 6/7: significant radiological releases occur
<ul><li>"All safety activities, whether organizational,
behavioural or equipment related, are subject to layers of overlapping provisions , so that if a failure should occur it would be compensated for or corrected without causing harm to individuals or the public at large...” </li></ul><ul><ul><ul><li>Basic Safety Principles for Nuclear Power Plants (INSAG-3) </li></ul></ul></ul><ul><li>The strategy for defence in depth is twofold: first, to prevent accidents and second, if prevention fails, to limit the potential consequences of accidents and to prevent their evolution to more serious conditions. </li></ul>Defence in Depth Explained
Defence in Depth Illustrated <ul><li>The
fuel matrix </li></ul><ul><li>The fuel cladding </li></ul><ul><li>The boundary of the Reactor Coolant System </li></ul><ul><li>The Containment System </li></ul><ul><li>Mitigation of the radiological consequences of significant external releases of radioactive materials </li></ul><ul><ul><li>Quality Assurance </li></ul></ul><ul><ul><li>Control systems (alarms) </li></ul></ul><ul><ul><li>Safety culture </li></ul></ul><ul><ul><li>Accident management </li></ul></ul><ul><ul><li>Emergency planning </li></ul></ul>P H Y S I C A L P R O C E D U R A L Based on INSAG-10: Defence in Depth in Nuclear Safety
Defence in Depth Rated <ul><li>Initiator
approach: </li></ul><ul><li>The occurrence that c hallenges the safety systems, e.g. reactor trip, loss of coolant, loss of off-site power </li></ul><ul><li>Power reactor while at power; hot shutdown; start up conditions </li></ul><ul><li>Safety layer approach : </li></ul><ul><li>How many layers of safety still remain </li></ul><ul><li>Power reactors during shutdown; cold shutdown </li></ul><ul><li>Fuel cycle facilities, research reactors, accelerators, etc </li></ul><ul><li>Identify how close the event was to causing actual consequences by looking at the safety provisions: </li></ul><ul><ul><li>What has failed? and What is left? </li></ul></ul>
How to Communicate INES Events
<ul><li>NEWS: www-news.iaea.org </li></ul><ul><ul><li>Events rated at INES level 2 and above </li></ul></ul><ul><ul><li>Events attracting international public interest </li></ul></ul><ul><ul><li>IAEA hosts and administrates the system </li></ul></ul><ul><ul><li>Event reports are filed and updated by the participating countries </li></ul></ul>
Provides a harmonized approach. France, Japan, UK and other were looking at a nuclear event scale to help in public communications and were considering creating one. IAEA and NEA pulled together all interested parties to develop an internationally consistent one (use at national level and international level) Simplicity of a seven-level Scale with a solid technical background similar to other existing scales Harmonized international approach 1990 – only nuclear power plants By 2008 - wider scope to include all: nuclear facilities; radiation sources (accelerators, irradiators, etc), radioactive sources (exposure of workers or public, etc) Only for civilian applications; only relates to the safety aspects of an event INES scale does not replace existing well-established criteria used for formal emergency arrangements in any country
The Country where the event occurs is responsible for rating the event Can be provisional or final: exact nature of the damage/contamination many not be known for some time Events posted by the Member State in the NEWS system www-news.iaea.org Specific terminology: Levels 4–7 are termed “accidents” ; Levels 1–3 “incidents”. The scale is a logarithmic one. The severity of an event would increase by about an order of magnitude for each increase in level on the scale Events unrelated to radiation or nuclear safety are not rated using INES Potential consequences – defence in depth concept Actual consequences 1986 Chernobyl accident - level 7 widespread impact on people/environment 1999 Tokaimura: fatal overexposure of workers – level 4 1989 Vandellos: near accident, fire and loss of safety systems 2006, Forsmark: degraded safety functions due to failure in emergency power supply
Criteria 1: Considers the actual radiological impact to workers and members of public and to the environment. Can be localized or widespread as in the release of radioactive material. Rating Level: 4 to 7 Criteria 2: Damage to radiological barriers and controls. Applicable to major facilities where a site boundary is clearly defined as part of their licensing Facilities handling major quantities of radioactive material (with a potential for a Level 5 release) -NPPs, reprocessing facilities Typical events are: fuel damage, reactor core melt and contamination spread-criteria applies to major facilities Criteria 3: The concept includes protection of the barriers by averting damage to the plant and to the barriers themselves. (it will be discussed in “depth” two slides down)
Level 1 covers only degradation of defence-in-depth. Levels 2 and 3 cover more serious degradations of defence-in-depth, or lower levels of actual consequence to people or facilities. Levels 4 to 7 cover increasing levels of actual consequence to people, the environment or facilities. Radioactive release to the atmosphere - level 4 to 7. The rating is based on the radiological equivalence to a atmospheric release for each isotope released. The rating is based on the quantity released. The actual dose received will greatly depend upon the protective actions implemented and other environmental conditions. Impact on radiological barriers and controls - formerly named on-site impact - level 2 to 5 only.
Structured in five levels, subsequent levels comes into play. Prevention of abnormal operation and system failures : conservative design and high quality in construction and operation Control of abnormal operation or failures detection: control, limiting and protection systems and other surveillance features Ensuring safety functions are performed - activating specific safety systems and other safety features Limiting accident progression through accident management - to prevent or mitigate severe accident conditions with external releases of radioactivity Mitigation of the radiological consequences - off-site emergency response Special attention is paid to hazards that could potentially impair several levels of defence in depth: fire, flooding, earthquakes
This is the event rating form provided for the rating of Fukushima Daiichi units 1,2 and 3. Event rated provisionally at Level 5. The event at Fukushima Daiichi 1 was initially rated at level 4, within 24 hours by Japan. It was uprated later to level 5. It is still provisional. The event at Fukushima Daiichi 5 was rated at level 3 (next slide) Rating is for a facility.
This is the event rating form provided for the rating of Fukushima Daiichi units 1,2 and 3. Event rated provisionally at Level 5. The event at Fukushima Daiichi 1 was initially rated at level 4, within 24 hours by Japan. It was uprated later to level 5. It is still provisional. The event at Fukushima Daiichi 5 was rated at level 3 (next slide) Rating is for a facility.
NEWS = Nuclear Event Web-based System Not a formal reporting system; voluntary system for communicating events at international level. Countries have their own system to communicate events at national level, usually the safety authority websites Events posted by the country where the event occurred INES community: officially designated national officers in over 70 Member States Periodically, the INES advisory committee assess the rating of events for sharing experience on the use of the Scale INES advisory committee meets once a year, or as needed (next meeting: July 2011) INES National officers meet every two years (last meeting held in October 2010. Next planned for 2012)
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