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Tuesday 29 March 2011

Meltdown Shock Horror – The Story So Far

Although the news cycle has, in part, moved on from the earthquake and tsunami in Japan, the problems at the Fukushima Daiichi nuclear power station have continued. I’ve not checked this out for some days now, mainly because the news coming out of the area has not been conducive to getting a handle on what is really going on.

As there has been little more said about the previous problems with the spent fuel “ponds” at Reactors 3 and 4 of the six-reactor complex, it has to be assumed that sufficient cooling water has been pumped into the ponds to stabilise the fuel, and the level maintained. So, hopefully, that means no further leak of radioactivity there.

The focus has therefore returned to getting water into the pressure vessels of the three reactors that were working at the time of the earthquake, and where the shutdown process was hampered when the tsunami took out the emergency pumps, leading to overheating of the fuel assemblies.

According to this report, the “injecting” of water into the reactors is continuing, although the residual heat within the pressure vessels means some of it is boiling off – and there is a risk that there will be further generation of hydrogen, which when vented to the air could mean another explosion.

Will the change to using fresh water rather than seawater make a difference? Possibly, although I reckon none of the three reactors will ever see service again – they will be written off, as was that involved in the incident at Three Mile Island (TMI). Their only remaining duty will be to soak up a lot of resources as the cleanup continues.

And the discovery of radioactive water in the various turbine halls? This should not be a surprise, as the turbine hall and reactor building are adjacent. Moreover, the steam circuit for a Boiling Water Reactor (BWR) comes directly from the reactor pressure vessel to the turbine, so it only needs a fracture in that circuit to produce the contaminated water that is now being found.

None of this should induce panic. Nor should the possibility that one of the reactor containments has been breached, until we know for sure the extent of any damage. So far, this incident has followed TMI in being substantially an economic setback, rather than an environmental one.

Hopefully, it will remain in the economic category, and not cross over too far into the environmental one.

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