Much of the mainstream media coverage of the unfolding events at the Fukushima Nuclear Plant has been sensationalized and full of inaccuracies. I’m going to attempt to cut through some of the BS and put a little truth out there, at least on our little corner of the internet.
Here is the Google Maps view of the plant:
http://maps.google.com/maps?hl=en&ie=UTF8&ll=37.422253,141.029348&spn=0.020518,0.041971&t=k&z=15
Starting at the bottom, the large square structures are the reactor buildings 1, 2 & 3. These are the older of the reactors on site. Next to them is reactor 4, and reactors 5 & 6 sit further up the coastline, near the end of the seawall. All 6 reactors are older model Boiling Water Reactors, or BWRs. These units are normally water cooled, meaning the fuel rods are fully submerged. The reactors were also connected to grid power in case of an internal power failure. All reactors were also equipped with emergency diesel generators and battery back ups as a final redundancy.
At the time of earthquake on 3/11, Units 4, 5 & 6 were shutdown for maintenance, and only units 1, 2 & 3 were operating. After the quake, all 3 operating units were scrammed. Here are the current statuses of the reactors, per multiple sources.
Reactors 5 & 6:
Temperatures in units 5 & 6 have been rising, and there have been concerns about the lack of additional cooling water being injected into the cores, however, at this point neither reactor has had any major issues, and if grid power can be restored both cores should be intact.
Reactor 4:
Reactor 4 was offline and unfueled at the time of the quake, however, it has had issues with the spent fuel pool, which apparently has little or no cooling water. This in turn led to a hydrogen buildup and explosion, breaching the out containment building. At this time it is not believed to have achieved criticality, although no definitive data is available.
Reactor 1:
The fuel rods in the reactor were or are at least partially exposed. Seawater injection was used as an emergency cooling procedure. Hydrogen gas buildup also led to an explosion, damaging the outer building.
Reactor 2:
Similar to Reactor 1, except that there may be damage to the primary containment vessel or reactor core itself.
Reactor 3:
Similar to Reactor 2, with additional problems similar to reactor 4 concerning spent fuel storage as well.
The use of seawater in several of the units means they will not be recoverable for normal use even if cooling is restored. Boron injection is also being considered, and according to reports both France and South Korea are flying in large supplies.
The basic problem seems to have been the lack of redundant cooling on-site. Although generators and batteries were available, they appear, for the most part, to have been damaged either in quake or the follow on tsunami. The fact that the plant sits on the coast in a quake prone region without adequate tsunami protection seems to be a major design oversight, shall we say.
That being said, this should not deter the U.S. Nuclear power industry from expansion. These plants are older, obsolete designs managed by a utility with a history of safety faults and falsification of records (TEPCO). If plants are built to proper local specs, Nuclear power is still safe and clean.
Sources:
http://www.iaea.org/newscenter/news/tsunamiupdate01.html
http://en.wikipedia.org/wiki/Fukushima_I_nuclear_accidents
http://en.wikipedia.org/wiki/Tokyo_Electric_Power_Company
http://www-ns.iaea.org/tech-areas/emergency/ines.asp
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