Tuesday, April 12, 2011

IAEA Briefing On Fukushima Severity Level


# 5486




The International Atomic Energy Agency (IAEA) released an update over the last few hours on the revision to the Fukushima severity level I reported last night (see Fukushima: Brief Fire, 6.4 Aftershock & Severity Level To Be Raised).


While sharing the same severity level as Chernobyl, Japan’s Nuclear and Industrial Safety Agency (NISA) is quick to point out that the amount of radiation released from Fukushima is estimated to be 1/10th that of the Russian disaster.



NISA, however, has come under increasing criticism for its handling of the disaster and the speed in which it has released radiation readings from the reactor facilities and surrounding areas.


There have been frequent calls from the public, international agencies, and world governments for better dissemination of information on the nuclear crisis (including Kyoto News China urges Japan to release timely, precise info on nuke crisis).


Yesterday NISA publicly admitted that their actions have not always been adequate for the task at hand (see NHK News Nuclear safety regrets its response to Fukushima).


Events and admissions that are likely to do little to assuage criticism and frustration over NISA’s ongoing assessment and handling of the nuclear risks at Fukushima.


Here is the IAEA update, followed by links to the NISA announcement.




IAEA Update on Fukushima Nuclear Accident (12 April 2011, 4:45 UTC)

by International Atomic Energy Agency (IAEA) on Tuesday, April 12, 2011 at 12:43am

The Japanese Nuclear and Industrial Safety Agency (NISA) today issued a new provisional rating for the accident at the Fukushima Daiichi nuclear power plant on the IAEA International Nuclear and Radiological Event Scale (INES).


The nuclear accident at Fukushima Daiichi is now rated as a level 7 "Major Accident" on INES. Level 7 is the most serious level on INES and is used to describe an event comprised of "A major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures." Japanese authorities notified the IAEA in advance of the public announcement and the formal submission of the new provisional rating.


The new provisional rating considers the accidents that occurred at Units 1, 2 and 3 as a single event on INES. Previously, separate INES Level 5 ratings had been applied for Units 1, 2 and 3. The provisional INES Level 3 rating assigned for Unit 4 still applies.


The re-evaluation of the Fukushima Daiichi provisional INES rating resulted from an estimate of the total amount of radioactivity released to the environment from the nuclear plant. NISA estimates that the amount of radioactive material released to the atmosphere is approximately 10 percent of the 1986 Chernobyl accident, which is the only other nuclear accident to have been rated a Level 7 event.


Earlier ratings of the nuclear accident at Fukushima Daiichi were assessed as follows:


On 18 March, Japanese authorities rated the core damage at the Fukushima Daiichi 1, 2 and 3 reactor Units caused by loss of all cooling function to have been at Level 5 on the INES scale. They further assessed that the loss of cooling and water supplying functions in the spent fuel pool of the Unit 4 reactor to have been rated at Level 3.


Japanese authorities may revise the INES rating at the Fukushima Daiichi nuclear power plant as further information becomes available.


INES is used to promptly and consistently communicate to the public the safety significance of events associated with sources of radiation. The scale runs from 0 (deviation) to 7 (major accident).


For further information on the INES scale:


Further details regarding this development can be found in the following NISA press release:


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