Tuesday, April 05, 2011

A few things arising from Fukushima

Here's a few things I have learnt from the coverage of the Fukushima accident:

1. Criticality accidents: well, I'm not Homer Simpson, and haven't ever read that much about dangers of operating nuclear plants, but the uncertainty over whether Fukushima has had some criticality incidents led to this explanation of what they are at the Time Ecocentric blog:
To nuclear workers, there are few events more fearful than a criticality accident. In such a scenario, the fissile material in a reactor core--be it enriched uranium or plutonium--undergoes a spontaneous chain reaction, releasing a flash of aurora-blue light and a surge of neutron radiation; the gamma rays, neutrons and radioactive fission products emitted during criticality are highly dangerous to humans. Criticality occurs so rapidly--within a few fractions of a second--and so unpredictably that it can suddenly kill workers without warning. There have been 60 criticality incidents worldwide since 1945. The most recent occurred in Japan in 1999, at an experimental reactor in Tokai, when a beam of neutrons killed two workers, hospitalized dozens of emergency workers and nearby residents, and forced hundreds of thousands to remain indoors for 24 hours.
Nature has a post detailing the controversy as to whether small scale criticality accidents have been happening at Fukushima.

2. Jimmy Carter took part in a dangerous reactor rescue in 1952:
The reactor in Chalk River, Canada, about 180 kilometres (110 miles) from Ottawa, was used to enrich plutonium for America's atomic bombs. On December 12th 1952 it exploded, flooding the reactor building’s basement with millions of litres of radioactive water. Lieutenant Carter, a nuclear specialist on the Seawolf submarine programme, and his men were among the few people with the security clearance to enter a reactor. From Schenectady, New York, they rode the train up and got straight to work.
"The radiation intensity meant that each person could spend only about ninety seconds at the hot core location," wrote Mr Carter in "Why Not the Best?", an autobiography published in 1975 when he was campaigning for the presidency.

The team built an exact replica of the reactor on a nearby tennis court, and had cameras monitor the actual damage in the reactor's core. "When it was our time to work, a team of three of us practised several times on the mock-up, to be sure we had the correct tools and knew exactly how to use them. Finally, outfitted with white protective clothes, we descended into the reactor and worked frantically for our allotted time," he wrote. "Each time our men managed to remove a bolt or fitting from the core, the equivalent piece was removed on the mock-up."
Impressive.

3. A commentary piece in Nature News today shares my view that the rush of some nuclear proponents to downplay the extent of the problems from this accident has not been helpful. It notes three lessons with wide implications for the nuclear industry around the world:

a. co-siting of nuclear reactors is (apparently) common in Western countries "because the only communities that will accept new nuclear plants are those that already have them." Yet the problem is, as we can see, have one go seriously wrong, and it can badly hamper the safe operation of the rest on the same site.

b. light water reactors melt if the water isn't there:
These designs are compact and relatively inexpensive, but their potential for meltdown was once obvious enough that Britain spent 30 years trying to develop gas-cooled alternatives. But, now that PWRs are the only viable design for new nuclear build, that extensive search for a safer design seems to have been forgotten by many of those who promote a nuclear future.
c. spent fuel rods have no where to go in Britain and the US.

The commentary then notes:
These legitimate technical criticisms of Fukushima, and of planned nuclear build, have been largely drowned out by the flood of technical reassurance offered by nuclear scientists and engineers in the wake of the disaster. For example, reassuring soundbites offered to journalists by the London-based Science Media Centre (which is funded by a variety of scientific bodies and industries, including Nature Publishing Group) in the days immediately after the earthquake contained barely a cautionary note on how serious the situation at Fukushima was set to become. Instead, the scientific establishment and those whose careers are invested in nuclear power have sought to convince the public that 'science' supports nuclear power. Too many specialists have assured us of the general safety of nuclear power without adequately addressing specific concerns.
Pretty much what I said.

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