I think the reading public is close to giving up on trying to follow this remarkably opaque disaster, which is compounded by a company apparently dead-set against sharing information with the government or any other non-nuclear outsiders, multiple reactors of different makes, and faulty measurements or no measurements.
Just to add to the confusion, we have international radioactivity standards that inexplicably shifted from old and familiar terms like rads, rems, and curies to grays, sieverts, and becquerels. Here's a glossary that compares old and new terms. Example: "One gray is equivalent to 100 rads." Good luck figuring out the dosages that justify evacuation!
Meanwhile, we have our daily dose of confusion over which reactor did what, and why. One day a unit is declared stable and the next day there's a cloud of smoke or steam or dust that nobody can explain. Things are supposedly well in hand one day, and the next we hear of radioactive iodine briefly showing up in Tokyo's water supply. (I haven't see any indication that Tokyo residents are at significant risk from this, but the event is odd given that the nearest point of the watershed of the Tone River -- which supplies most of Tokyo's water -- is more than a hundred miles southwest of the reactors.)
Yes, there are tables and reports showing the status of all six reactors and these are of help, but none that I've seen so far are fully authoritative, prompt, and thorough. That's because Tepco is holding back the information that would make such updates possible.
To illustrate how frustrating it is to keep track, there were reports yesterday that radioactivity had reached astonishing levels in the basement of Unit 2's turbine building, according to this update from the Bulletin of Atomic Scientists. Citing official sources, the BAS said the level of Iodine-134 in Fukushima Dai-ichi Unit 2 had reached 2.9 billion becquerels/cubic meter. Then this item from NHK said the level was 2.9 billion per cubic centimeter, which would be much higher.
Then the authorities retracted all those numbers today as too darned high, according to this piece in the LATimes.
Op-ed writers have been busy opining on the future of the nuclear power industry, but the information quality out of Fukushima is so poor that I'm refraining from conclusory statements such as "the existing fleet is pretty safe, except for outliers like these," or "let's drop the whole idea of electricity from fission," or "the new generation of reactors relying on natural-circulation cooling are the really safe ones."
It will be at least a year until objective information comes out on the course of events at Fukushima. Right now, it's enough of a challenge just to figure out what Tepco is trying to do.
Setting aside the latest flap over Unit 2's basement numbers, Tepco says that radioactivity levels went up shortly before three workers were exposed to radiation while wading through a basement. Tepco said that it had assumed the area was still safe for workers.
Obviously that was a flawed approach to safety, but it also suggests either that a new leak allowing water from the reactor core into the turbine-building basement has opened or an accidental criticality is underway somewhere, adding to the iodine and cesium inventory (less likely but troubling if so).
So, Question 1: BWR control panels are supposed to have an instrument called the neutron flux indicator (here's a link to a patent document for one), showing the level of fission in the core. What are the readings from the neutron flux indicators in the two control rooms for Units 1-4? Set aside the mysterious "neutron beams" detected in the vicinity last week: the neutron flux indicators are supposed to be definitive. In this post, the Union of Concerned Scientists studied official photos of the re-opened control room of Unit 2 and compared critical instruments to those in a BWR simulator, pointing out that the Unit 2 control room didn't seem to be functional at the time of the photography.
A credible case has yet to be made that the cooling circuit "repairs" to the cores of the most hazardous units are going to work in any manner other than dumping water in one end (via spray heads or feedwater pipes) and having it gush out somewhere else. Injected water seems to be going into various basements, either under the reactor buildings or the turbine buildings, and then finding its way out to the sea.
Question 2: Has Tepco been using something like a trash pump to dump water from the basements directly to the sea?
If the promise from Tepco is that it plans to restore a closed circuit to recirculate the primary cooling water that comes into contact with the reactor core, so that it isn't dumped into the basements or the ocean, this will be a truly formidable job at Units 2 and 3.
Recently I looked into the subject of "the world's toughest industrial problems" for a television producer, and nothing I came across in that research approached the difficulty of this one. A workmanlike job couldn't even start until an expert assessment of the equipment status from reactor building to turbine building to control rooms, which would need to assess all damage due to the earthquake shocks; overheating; overpressure; stress corrosion cracking; salt deposits around the fuel rods; the operation of gate, check and pressure-relief valves; and the unintended effects of attempted workarounds. I suspect something like this has been distributed to experts at GE, Hitachi, and JAIF.
Question 3: If so, can we get a look at the damage assessment?
Let's assume that experts have mapped out what equipment is broken in each reactor, and what can be relied on; and they've been able to procure suitable replacement parts from check valves to instruments to elastomeric seals to piping. Finding spare parts is not easy for way-old equipment like that at Fukushima, but given that a number of similar reactors are still in service, it should be possible, like finding parts for 1970s muscle cars.
Which leads to Question 4: Can we get a copy of the new primary cooling circuit diagram being used to guide work at Units 2 and 3, assuming that something more is planned than a once-through use of cooling water? Given that the upper walls and roof of Unit 3 has collapsed on the upper levels of the main reactor structure, I'm curious how repairs will proceed. Here's a link to a useful diagram of a BWR, drawn in the style of a subway network.
All in all, the time for a "fix" of the primary cooling circuit in any conventional sense seems to have expired. One reason is that radiation levels in some areas is so high that Tepco is running out of contract workers to handle high-dosage jobs.
Question 5: Exactly which contractor companies are providing temporary workers for Tepco, and which neutral health agency is monitoring the health of every worker, not just the ones sent to the hospital?
Assuming for the sake of argument that the contract labor supply dries up, and that the government doesn't turn to ordering troops in, that leaves teleoperated machinery, robots .... or abandonment in place to let the radioactivity die down. I think the latter scenario is increasingly likely at Units 2 and 3.
Sidebar: Temporary, unskilled workers brought in for high-dosage reactor-maintenance jobs are called "jumpers" in this country. They're outside non-technical people like farm workers, clerks, or auto mechanics paid to learn a simple job like replacing a nut in a confined space. Then they suit up, put on a dosimeter, and go in. The allowable time for any given jumper to do his job may be only minutes, if the radioactivity level is high. So it can take several jumpers to remove a nut and put a new one on.
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