INES, event scale

The assessment of integral damage caused by implications of individual accidents was compared with some standard levels determined by the International Nuclear Event Scale (INES). The INES scale, supplemented by expert assessments of economic damages, as applied to typical emergencies with decommissioning objects, is illustrated in Table 1. 

TABLE 19.6. The international nuclear event scale (INES) used for the reporting of nuclear events... 

INTERNATIONAL ATOMIC ENERGY AGENCY, The International Nuclear Event Scale (INES) User s Manual, 2001 Edition, IAEA, Vienna (2001). 

INES International Nuclear Event Scale INES is an information system operated by IAEA to inform the public about safety related events in nuclear power plants (IAEA 2001) http //www-news.iaea.org/news/... 

Failure of the sodium coolant circuit and its long exposure to the atmosphere lead to a fire and, consequently, to a 24-h release of Ci accounted for by Na alone. Further Na burning will cause cooling interruption and fuel melting with release of 10 —10 Ci, depending on the reactor power level and the time of fuel irradiation. Such an accident is classed as Level 7 of the International nuclear event scale (INES) and involves inevitable evacuation of the local residents with prolonged isolation of the territory (ISTC 2001 Orlov et al. 2003). 

The emergency classification should not be confused with the International Nuclear Events Scale (INES) (IAEA, 1997c). INES is designed to indicate how serious an event was after it is understood and is not the basis for the response. Determining the INES rating is impossible early in an event and does not form part of the initial response, and determining the rating should not delay any response actions. 

The emergency response classification system should not be confiised with the lAEA/NEA International Nuclear Event Scale (INES). The INES is designed for communicating the severity or estimated severity of an event to the pubhc and cannot be the basis for emergency response actions. 

INES International Nuclear Event Scale Defines the safety significance of an event occurring in a nuclear facility. Scale 0 (least serious) to 7 (most serious). Chernobyl would have been a 7. 

Hydrogen explosions in units 1, 2 and 4 and pressure venting operations in the reactor vessels caused massive releases of radioactive material to the atmosphere and environment. The prevailing winds transported most of the atmospheric emissions in an easterly direction into the Pacific Ocean region. On the 8 stage International Nuclear Event Scale (INES) the accident was rated as 7, the highest rating on this scale. ... 

The operating organization should provide information on the status of the plant to the public in a regular and timely manner. The pnbUc should be informed of any significant event on the International Nuclear Event Scale (INES) [4] and of any enforcement action taken by the plant. 

In case of any event that clearly deviates form normal behavior of a reactor (ranging from observations with safety implications to catastrophes), the event should be reported to IAEA and the appropriate organizations in other coimtries. For reports to the press and to the general public of safety related events in nuclear power plants IAEA and OECD/NEA recommend the INES scale, see Table 19.6. 

If we exclude a half (51) of events which have not led to a deterioration (real or potential) of a reactor safety function, it becomes obvious that the largest number of really significant anomalies is, like on other installations, associated with the loss of standby electricity supply (which did not have important consequences for Superphenix since there are 4 identical sets), but also that the second cause of safety function deterioration is linked to sodium. This illustrates that the two, sodium-related, incidents which were classified level 2 on the INES scale (nos. 40 and 61) were not isolated events. 

All the significeint events occurring on Creys-Malville have been classified using the criteria on the INES scale of nuclear events. It must be observed that for events occurring prior to application of the French scale, the subsequent classification cannot take account of the discussions which have taken place in certain limit cases. However, this classification benefits from all the experimental classification work which had been carried out by IPSN and EDF when defining the French scale. 

DESCRIPTION OF EVENTS CLASSIFIED LEVELS 1 AND 2 ON THE INES SCALE... 

In 1996, a good safety level was maintained 1.6 event per reactor/year. A level I classification was given to 84 events. A level 2 classification was given to 2 events (INES scale). 

The reason of this incident was a fault during repair work. This event was estimated as level 1 on INES scale. 

Even in the most severe accident with coolant circuit failure and direct contact of lead with the atmosphere, the ensuing toxic and radioactive releases would correspond merely to Level 5 on the international scale of events at NPPs (INES), which is an accident dangerous for the environment but not requiring evacuation of the local population (ISTC 2001 Orlov et al. 2003). 

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