Fukushima Daiichi #1 Accident
This is a report I prepared for another conference 2030 EST (-0500 UCT)
As far as the state of the core at Fukushima Daiichi 1, at this time NHK and Nikkei are reporting that the NISA, Japan's nuclear regulatory authority, have said that a partial meltdown has occurred. However, the most recent NISA press release available in English [PDF], the IAEA, and industry sources make no mention of a meltdown, or as @arclight on twitter suggests they might core melt or core damage.
The confusion over the state of the core is perhaps due to the fact that all parties are in agreement that the events at Fukushima Daiichi 1 are an INES Level 4 'Accident with Local Consequences'. The criteria for this classification are
Nevertheless the amount of radiation detected at the site boundary reached 500 microSieverts per hour - exceeding a regulatory limit and triggering another set of emergency precautions. It also meant the incident has been rated at Level 4 on the International Nuclear Event Scale (INES) - an 'accident with local consequences'.
This would seem to indicate that no core melt has occurred, despite reports to the contrary by the NHK and the Nuclear Energy Institute.
As far as the state of the core at Fukushima Daiichi 1, at this time NHK and Nikkei are reporting that the NISA, Japan's nuclear regulatory authority, have said that a partial meltdown has occurred. However, the most recent NISA press release available in English [PDF], the IAEA, and industry sources make no mention of a meltdown, or as @arclight on twitter suggests they might core melt or core damage.
The confusion over the state of the core is perhaps due to the fact that all parties are in agreement that the events at Fukushima Daiichi 1 are an INES Level 4 'Accident with Local Consequences'. The criteria for this classification are
- People and Environment
- Minor release of radioactive material unlikely to result in implementation of planned countermeasures other than local food controls.
- At least one death from radiation.
- Radiological Barriers and Control
- Fuel melt or damage to fuel resulting in more than 0.1% release of core inventory.
- Release of significant quantities of radioactive material within an installation with a high probability of significant public exposure.
Nevertheless the amount of radiation detected at the site boundary reached 500 microSieverts per hour - exceeding a regulatory limit and triggering another set of emergency precautions. It also meant the incident has been rated at Level 4 on the International Nuclear Event Scale (INES) - an 'accident with local consequences'.
This would seem to indicate that no core melt has occurred, despite reports to the contrary by the NHK and the Nuclear Energy Institute.