Pressure has reportedly dropped in the suppression chamber - suggesting a crack in the containment vessel. If so, radioactive materials (in air or possibly in liquid) can leak out.
Radioactivity levels have now risen significantly - numbers are no longer in MICROsieverts but in MILLIsieverts - a thousand times greater. Recommended annual doses are around 10mSv a year - measurements of 400mSv an hour have been reported.
Temperatures in the spent fuel pools have also risen as cooling is not in place (as warned of below). A further (hydrogen-ignited?) fire broke out in the pool in Reactor 4. Although this reactor is shutdown, the used rods can still generate sufficient heat to cause such an incident if cooling is ceased. down, These pools are outside the core containment and so radioactive material released by the fire will have risen into the atmosphere. The previous hydrogen blast at Reactor 3 has left its spent pool uncovered. A fire here could release toxic plutonium into the environment if MOX fuel rods are involved.
So much for a localised 'Level 4' incident. What a mess.
I was angry enough at the lies and distortions that have hit our news screens since Hutton reported on pensions - but the overnight media 'experts' on nuclear safety have driven this physics teacher to further levels of annoyance!
First we were told that there are always 'back-ups to the back-ups' in the nuclear industry - it seems not sufficiently at Fukushima - despite the obvious threat of major tsunamis in the region.
Now they have spent hours wondering whether or not there has been a meltdown when there have been clear reports of caesium being detected outside the reactor. Caesium is a fission product from uranium - there is only one place that it can come from - the reactor core. There has certainly been some kind of leak or meltdown - and the situation could well be getting worse.
There are now also pictures of an explosion at the plant which appeared to have blown off some of the containment structures - potentially allowing radioactive materials to escape into the environment (but see below). There will be brave workers valiantly trying to resolve the situation, but it is unclear how much they are able to do.
UPDATE: One worker at least has died. Sea water and neutron-absorbing boric acid/sodium polyborate (is this Clinton's mystery 'coolant' from the USA?) is apparently now being injected to try and cool the core (apparently an untested method being resorted to because of the failure of the plant's coolant systems- let's hope it works...). Seawater may also be needed to ensure that the 'used' rods in the spent fuel pools are also sufficiently cooled.
UPDATE: The explosion seems to have been a hydrogen explosion - probably caused by steam reacting with hot zirconium in the fuel rods. That alone confirms that there has been some kind of a problem inside the core. While many news outlets are keen to correctly say that this was not a "nuclear explosion" few seem to recognise that the presence of hydrogen in itself suggests that the core has been at worryingly high temperatures.
http://bit.ly/hOEXov Warnings about the design go back as far as 1972:This is already (IMO!) a worse situation than Three Mile Island in 1979. (14.3 - the French Nuclear Agency ASN are now publicly questioning the 'level 4' classification given to the events and suggesting it is a more serious 5 or 6 incident) The nuclear industry has always claimed that the effects of that accident were exaggerated and that there were few long-term health risks. However, at TMI the containment held firm. It was also a new reactor where there had not been time for the Caesium-137 levels to build up within the core. The Fukushima reactors are reportedly 40 years old.
UPDATE: TEPCO are saying that the containment structures remain intact but it is still seems uncertain whether the core has sustained any damage. Nearby residents have tested positive for radiation exposure.
Cs-137 is not only highly radioactive, it is also taken up into the body as if it were potassium, absorbed into muscles and other vital tissues.
Earthquakes are a natural disaster but Japan's choice to rely heavily on nuclear power was a political one. I believe that the risks of nuclear fission and the unresolved problems of waste storage have always meant this was the wrong choice. This disaster will add to the arguments against nuclear power as a solution to dwindling fossil fuels.
UPDATE: http://in.reuters.com/article/2011/03/12/idINIndia-55523220110312 It appears that TEPCO have previously been found guilty of falsifying data over coolant temperatures and repair records at Fukushima Daiichi - can we ever trust big business with public safety?
LATER UPDATE 13.3.11: Belatedly, the media are catching up with the severity of events at Daiichi. Concerns are also being raised about the nearby Fukushima Daini plant. Reports state that the emergency cooling system is also no longer functioning at the Fukushima Daiichi No.3 reactor. Officials are now admitting that they are working on the assumption of a partial meltdown in both reactors 1 and 3 and warning of the possibility of a further hydrogen explosion at No.3 (suggesting that the fuel rods must have been at dangerously high temperatures there too) . The seawater injection is apparently ongoing - permanently disabling the reactors which will never be usable again. However, the risk of further serious release of radioactive material is certainly still possible.
A real concern is that Reactor 3 started using MOX (mixed oxide) fuels last Autumn. Its core therefore includes plutonium as well as uranium.
MARCH 14 UPDATE: Radiation measurements are rising at reactor 1, water levels are falling in reactor 2 exposing the fuel rods, and the inevitable hydrogen explosion has occurred at reactor 3 (containing the MOX fuel). Japan's NISA (Nuclear and Industrial Safety Agency) latest press release contains the detail that for two hours overnight sea water injection had to be stopped 'because of the lack of seawater in the pit".
While seawater injection is still required at reactors 1 and 3, Kyodo News reports that the number-two reactor has now become the priority. This is because four of the the pumps to that reactor were put out of operation - perhaps by the earlier explosion in reactor three (which injured eleven). At one stage, the rods were totally uncovered, inevitably leading to at least some melting of the core materials.
The chances of a more serious meltdown allowing materials to break through the floor of the containment vessel in one of these reactors must be increasing.
The media 'experts' continue brazenly on. A BBC news item this morning tried to claim that residents will be protected by the high levels of iodine in the Japanese diet!!
This evening, TEPCO's reports confirm that the 'fuel integrity' is 'damaged' in reactors 1 and 3 and 'unknown' in reactor 2. While the containment integrity in the reactors is thankfully listed as 'not damaged', water levels in 1 and 3 are 'unknown' and pressures are increasing in reactor 2. See: http://bit.ly/fqj8Ig
This has now been followed by reports of an explosion being heard from Reactor No.2
Whatever the outcome, surely this incident illustrates that a global energy plan should not rely on nuclear power - and certainly not earthquake-vulnerable Japan.
For a socialist view from China Worker, read: http://www.socialistworld.net/doc/4929
There's a useful scientific explanation of events on http://www.scientificamerican.com/article.cfm?id=fukushima-core