As the full scale of the devastation that the earthquake – now upgraded to a whole 9.0 on the Richter Scale – and subsequent tsunami have caused to north eastern Japan has come clear, there are more stories of problems with the Fukushima-Daiichi nuclear power station.
Quite apart from the explosion in the auxiliary building of the station’s number one reactor, video of which is widely available, there is now reported to be a problem with the number three reactor. Once again, terms like “meltdown”, “radiation” and “exclusion zone” are being deployed, with the addition of the ultimately scary “plutonium”.So, once again, some facts may be born in mind. As I noted yesterday, comparisons with the accident at Chernobyl in 1986 are fatuous, as the Japanese reactors have a containment around them, and the Russian RBMK reactor did not. Moreover, the Japanese plants use water as both coolant and moderator, unlike the RBMK which used graphite to moderate the reaction.
But how come there was an explosion? This is consistent with reports that pressure within the reactor had been lowered by venting off steam, with that steam being accompanied by hydrogen, the latter being a by-product of an overheating reactor. What does it take to set off a hydrogen detonation? Think back to chemistry lessons at school: the answer is, not much.
The important thing is that the containment held, and continues to hold, all the fissile material inside it, and that the operators keep enough water flowing through the reactor while its residual heat dissipates. The result may be that the reactor is no longer usable, but as with Three Mile Island unit 2 (TMI2), that is an economic reverse, rather than an environmental one.
And the talk of plutonium? Reactor 3 at Fukushima is fuelled partly with Mixed Oxide, or MOX. This uses between 1.5 and 3 per cent reclaimed plutonium: it’s not going to turn the plant into a nuclear bomb. Once again, keeping enough water passing through the reactor core as the heat dies down is what is needed, the process not differing merely because the make-up of the fuel rods is a little different.
Why, then, the exclusion zone? The authorities are dealing with an uncertain situation: there has already been substantial loss of life, and so the decision will inevitably err on the side of caution. There may be further leaking of radioactive material. But, provided the reactors affected are kept relatively cool, there is no need for anyone to panic.Although panic sells papers.