The most serious concerns in the Japan nuclear emergency now lie with Fukushima Daiichi reactors 1 and 3, both of which have lost cooling and have suffered explosions.
On the positive side, neither containment is judged to have been damaged, and reports are positive that emergency injection of seawater into the reactors with added boron is working. However, such an action will likely destroy the reactors, since seawater is corrosive.
A chart published by the Japan Atomic Industry Forum classifies the situation of each reactor by system, based on government and utility reports.
Four plants were affected by the earthquake and tsunami on Friday 11 March; below is a short reactor-by-reactor summary as of 11am GMT. News as it breaks is being compiled on http://www.ansnuclearcafe.org
Unit 1: Explosion on 12 March outside containment (but which did not damage containment vessel) injured 4. Several people have been injured in other accidents, and a few are being treated for radiation sickness. IAEA reports one worker died in a crane operation accident; four others were injured. Levels of radioactive Caesium 137 and Iodine 131 detected outside the reactor on 12 March subsided during the day. Began pumping seawater on 12 March. Containment vented on 12 March.
Unit 2: Unit is shut down; primary cooling is not functional, but a backup system is working.
3: Hydrogen explosion outside containment injures 11 on 14 March. Containment venting on 13 March. Borated seawater pumping began 13 March. Containment judged undamaged on 13 March.
4, 5, 6: in shutdown
Evacuations around the plant have begun. A report from the Japan Times reports that between 100 and 200 people around the plant may have been exposed to higher-than-normal levels of radiation, according to the Fukushima Prefectural government; but it was not clear how high these levels were.
Fukushima Daini 1, 2 and 4 retain off-site power., Although the primary cooling system is not working in 2 and 4, secondary cooling is working. Unit 3 is shutdown.
Onagawa: Units under control as of 13 March. Radioactivity detected at site was probably due to containment venting plume from Fukushima Daiichi.
Tokai: one emergency backup diesel generator operating successfully to operate pumps to keep the plant cool; two others had failed.