My most trusted source of technical info on this nuclear incident has been Dr. Goto. He's an ex-Toshiba engineer, a designer of nuclear reactor containment vessels.
He's made a series of presentations explaining what he believes has been happening at the Fukushima plant, making it very clear why he believes so. He's been saying for some time that the reactor cores probably have been breached, based on data released by TEPCO and the gvt.
Recorded temperature and pressure levels contain figures seriously exceeding their design values. For instance, the pressure on the containment vessel in reactor no.1 has reached 0.8MPa, when the vessel is only designed to withstand up to 0.4MPa. (Under normal operation pressure is 0.1MPa)
TEPCO argued that the pressure vessel is made of thick steel and is solid. Goto san then released data from stress-tests performed on flanges and gaskets. It clearly showed that they leak when exposed to the kind of tempreture and pressure. Highly radioactive water found on the floors of reactor buildings 1 to 3 is the evidence.
He and ex-Hitachi engineer who managed a team working on No.4 reactor at Fukushima, Tanaka-san, held an emergency press conference on the evening of 26th Mar 2011.
From the info released by the PM's Residence, they've discovered data suggesting reactor no.1 experienced a total loss of the reactor coolant, probably due to a rupture on at least one of the main pipes on the 11th.
Supposing that one of the main pipes did rupture. Inside the pressure vessel during normal operation is around 270 degrees Celcius and about 7MPa. So this high-pressure steam would pour out from the pressure vessel into the containment vessel, raising the pressure of the containment vessel.The pressure inside the pressure vessel would drop, as well as the water-level inside the pressure vessel.
The graph Tanaka-san has plotted from data released by the PM's Residence shows just that happening to reactor No.1 few hours after the earthquake. Tanaka-san says any engineer monitoring these figures at the site totally would and should have been able to spot what happened.
'The sudden loss of coolant inside the reactor is the worst nightmare for nuclear reactors,' says Tanaka. 'It's never happened before. And as if that wasn't bad enough, ECCS didn't work.'
The control rods were inserted and nuclear fission chain reaction was stopped. However, even when the chain reaction is stopped, uranium and the fission products continues to undergo radioactive decays, producing enormous amount of heat (spent fuel rods must be cooled inside circulating coolant for 2-5 years). When exposed, fuel would produce enough heat to melt itself.
Normally under such circumstances, emergency coolant circulation system would kick in to keep the fuels cool. But this time the system didn't work due to power-cut and the loss of generator by the tsunami.
TEPCO used to boast about its 5 layers of shields against radiation. 1. Zirconium casing around the fuel rod 2. The pressure vessel 3. The containment vessel 4. The reactor building
Where's no.5....? Oh, oh yeah, I fotgot! No.1 isn't Zirconium casing, it's the fuel pellet itself. I don't know how a lump of radioactive substance can shield radioactivity, but that's what TEPCO says so there.
Zirconium melts at about 2000 degrees celcius. It also reacts with vapour to produce hydrogen. So it's at a serious risk when coolant is lost from the reactor. If coolant is lost from the reactor then the pressure vessel is already breached. The containment vessel is most definitely damaged after the high-pressure steam had hit it as shown by stress-test data. And the reactor building... I don't know if you remember watching the news of reactor building blowing up, but I'm sure the experts have explained that the building isn't there to contain radiation anyway so that was OK.
It means radiation isn't contained whatsoever. Which makes the plant very unsafe. More over, if Zirconium did melt, it could cause hydrogen/vapour explosion and severely damage the containers. Reactors aren't designed to withstand a hydrogen explosion. If containers get severely damaged, it could've been another Chernobyl or a lot worse.
Apparently, if you were a pro and you saw the data these are the things you would instantly think about. But they only kept calling for calm, only evacuated people living inside 3km radius. The evacuation zone was expanded to 10km then 20km next day AFTER the hydrogen explosion.
He said there were two implications, one is social and one is technical. The social implication, if I may summarise in my own words, is that the government or TEPCO can be trusted to give you a warning when there are serious risks. In fact, they're more likely to be giving you an impression that everything is OK.
The second technical implication he made wasn't too clear to me. He talked about the possibility of one of the pipes at a relatively low position in the reactor being ruptured. That would mean all the water you pump in will leak out through the rupture. He also talked about the increased likelihood of molten fuel gathering at the bottom of the pressure vessel. He seemed to personally believe that the molten fuel was melting down the pressure vessel as we speak.
It freaked me out for a good day. But I'd come to believe (perhaps because I want to) that the world will not end quite yet. Not sure how bad things will get, but I think the process is likely to be a slow and gradual one - which means we can do things about it. It may come to that the whole world will have to come together to make sure our children are safe or the survival of whole human race will be threatened. There really is no time to waste on freaking out - there's so much to do.
The evacuation zones must be adjusted according to possible imminent dangers and SPEEDI forecasts. People outside the evacuation zones should also be prepared to evacuate if they need to. The government is probably overwhelmed with humanitarian operation and the nuclear power plant, so it will have to be a bottom-up effort. Local communities will have to take the initiative in making evacuation plans, and we must get the government to support that.
I believe that with the current unity and resilience the Japanese people are showing, (which is now directed at silensing people who speak up against the dangers of nuclear power) it is possible to organise something like that, but TEPCO's got to stop playing a silly game that nobody, even themselves, don't find funny anymore. And the government has to start exhibiting some real leadership.
We can do this. We can over come this and make the world a better place than it was before the earthquake and make something positive from this devastating tragedy.
But the first step is transparancy - we all need to be on the same page.