Friday, March 25, 2011

Japan's damaged nuclear reactors

I note that the media hysteria over the damaged nuclear reactors in Japan is continuing unabated. I sometimes wonder whether those responsible have any idea what they're talking about. Yes, there's a problem: but the truly amazing thing about this situation is how well the reactors and their containment vessels have coped with a disaster with which they were never designed to cope.

The monster tsunami which left a Japanese nuclear power plant on the brink of meltdown measured at least 14 metres (46 feet) high, the plant’s operator said Tuesday. ... "Now we estimate the height at more than 14 metres. We have found traces of the tsunami at such elevations," TEPCO spokesman Naoki Tsunoda said, adding that the wave was 14 metres high when it passed through the plant’s parking area.

A tsunami can surge to an elevation higher than its height at the time when it hits shore, Japanese media noted. The stricken plant’s twin complex, some 10 kilometres (six miles) to the south, was also hit by the tsunami but received less extensive damage.

. . .

The plants were designed to withstand earthquakes of magnitudes up to 8.0 and tsunami waves of up to 5.7 metres [about 18.7 feet] at the No. 1 plant and 5.2 metres [about 17 feet] at the No. 2.

There's more at the link. Bold print is my emphasis.

So the reactors survived - without meltdown or total destruction - an earthquake ten times more powerful, and a tsunami two and a half times higher, than their design limits; yet the mainstream media appear to be ignoring this remarkable performance, and spending their time screaming about the danger. For example, on Friday morning CNN reported:

Three men working inside the No. 3 reactor stepped into water this week that had 10,000 times the amount of radiation typical for that locale, Nishiyama said. That water likely indicates "some sort of leakage" from the reactor core, signaling a possible break of the containment vessel that houses the core.

. . .

Some 17 people have been exposed to 100 or more millisieverts of radiation since the plant's crisis began two weeks ago following a 9.0-magnitude earthquake and subsequent tsunami struck.

A person in an industrialized country is naturally exposed to 3 millisieverts of radiation a year.

But Japan's Health Ministry recently raised the maximum level of exposure for a person working to address the crisis at the nuclear plant from 100 millisieverts to 250 millisieverts per year.

The workers had been laying cables in the No. 3 reactor turbine building's basement when they stepped in the water. It seeped into the ankle-height boots of two, according to the power company.

The workers remained in the 15-centimeter (5-inch) deep water for about 40 to 50 minutes.

Two of them were admitted to Japan's National Institute of Radiological Sciences: one in his 30s who was exposed to 180.7 millisieverts and the other in his 20s who tested at 179.37 millisieverts.

Nishiyama said the third man -- who was exposed to 173 millisieverts but at first did not go to the hospital because his boots were high enough to prevent water from touching his skin -- has also gone to the same research hospital out of "an abundance of caution."

Again, there's more at the link.

Sounds terrible, doesn't it? . . . until you realize that even the three who incurred doses in excess of 170 millisieverts are still well within the US EPA's recommended dose limit for emergency workers in lifesaving operations (which is 250 millisieverts). That dose limit isn't healthy, of course; but it's not fatal, either. (XKCD has put out a very useful graphical representation of radiation dosage, showing everything from the dose one gets through sleeping next to someone for a single night [0.05 microsieverts, or five one-hundredths of a millisievert], to a guaranteed fatal dose [8 sieverts, or 8,000 millisieverts]. The chart makes useful and informative reading. Recommended.)

The fifty-odd workers who stayed at the nuclear plant to try to restore its cooling systems are, indeed, brave people. It may be that their continued presence there, in the face of cumulative radiation exposure, may prove fatal to some or all of them. However, let's not forget that they're dealing with a problem that's strictly limited. It's not (so far) having a terminally disastrous effect on the nation of Japan as a whole, despite what the panic-stricken headlines would have you believe. Farmers are still growing food; water is still being processed, purified and consumed; life is going on.

For continually updated, accurate information on what's happening at the damaged reactors, I recommend following the Nuclear Information Hub at the Massachusetts Institute of Technology's Department of Nuclear Science and Engineering. It's one of the few sources that's providing strictly scientific, rational measurements of what's going on - without fear-mongering, or panicked prognostications of doom, gloom and disaster.


1 comment:

douglas2 said...

I've seen entries from other bloggers who feel "lied to", as in response to the overblown drama from the large media we've all been pushing back and saying "it's bad, but not really a problem because it looks like the Japanese are on top of things, here is the real state right now..."
The trouble is that each day or two the situation is demonstrably worse than what we had described to them.