As the situation at Japan's Fukushima Daiichi nuclear powerplant slowly winds down, the salient facts remain the same as they have been throughout: nobody has suffered or will suffer any radiological health consequences. Economic damage and inconvenience resulting from the quake's effects on nuclear power have been significant, but tiny in comparison to all other human activities – the nuclear power plants in the stricken region have suffered less damage and caused less trouble to local residents than anything else that was there.
Despite this background, the details of which are now largely uncontested, hysteria continues to grip large sections of the news media and the internet.
The latest events at the plant itself:
Three workers who suffered noticeable but not dangerous radiation doses from standing ankle-deep in radioactive water – and possible minor burns equivalent to a mild case of sunburn – have been confirmed to have suffered no ill effects. Their "hospitalisation with radiation burns" was widely reported: the fact that they are – as was to be expected – perfectly fine was not.
More radioactive water has been found in a deep trench containing pipework and cabling adjacent to the No 2 reactor. This was measured as being noticeably radioactive four days ago, enough that a person could only be immersed in it for a quarter of an hour before sustaining a radiation dose sufficient to merit withdrawal from operations at the site – though not enough to cause any measurable health consequences.
Analysis indicates that some of the water in the trench by No 2 has been in contact with heat-damaged fuel in the reactor core. This is unsurprising as government and power-company officials had assessed as long ago as early last week that there had probably been damage to the No 2 suppression chamber, a doughnut-shaped vessel surrounding the central core vessel into which steam from the core has been released continually during the incident.
Normally water in the suppression chamber cools the steam and it is held there to allow short-lived isotopes to dissipate before being vented onward to atmosphere, so minimising radiation levels at the plant. But with the suppression chamber damaged as has long seemed likely, some steam from the core could have become water and exited below the building. The trench in question has 16m-deep shafts at each end and connects to a tunnel running below the No 2 complex.
Alternatively, radioactive steam from the suppression chamber could be condensing elsewhere in the building to trickle down and out and pool on top of otherwise harmless water already in the trench as a result of the tsunami, rain and snowfall since, massive pumping operations to cool spent-fuel pools etc. The trench, shafts etc contain many thousands of tonnes of water, only very small amounts of which could possibly have come via the core. Plant workers have built a sandbag barrier to prevent water spreading in the event of the trench overflowing.
Similar trenches and shafts exist at units 1 and 3, which also have damaged cores. Only tiny levels of radiation have been found at No 1, whose suppression chamber is thought to be intact; at No 3, thought likely to have suffered damage similar to that at No 2 (this too was announced last week), the trench is too clogged with tsunami debris to take readings.
As the situation has stabilised, workers at the plant have tried to minimise corrosion damage to the worst-hit reactors by switching from emergency seawater cooling of the cores and spent-fuel pools to the use of fresh water – in some cases delivered via the normal cooling equipment, restored to service with new electric power supplies to replace those wrecked by the tsunami. It had been hoped until recently that the expensive reactors might be restored to service in future.
Plant owner TEPCO has now decided to cut its losses, however, stating that it now considers that reactors 1 to 4 at the site will have to be written off: being near the end of their planned lives anyway, it makes no sense to spend much money on fixing them. The other two Daiichi reactors, Nos 5 and 6, were brought safely into a cold shutdown condition early on and TEPCO still expects to continue operations with these (as would be quite normal: both Chernobyl and Three Mile Island continued in operation as nuclear power stations following the incidents there).
The Japanese government, under tremendous pressure from the media-pumped hysteria over the issue, has said that it thinks the 5 and 6 reactors should also be shut down permanently. Rumours that the government might nationalise TEPCO are circulating widely, though denied both by the company and the state. TEPCO's 11 other reactors seem certain to continue in service, as will the 40-odd owned by other Japanese power companies. The company seems to be coping well with the temporary loss of many of its power stations: it cancelled planned rolling blackouts today and has announced that tomorrow's planned blackouts will not take place either.