Tuesday, March 15, 2011

Maximum credible accident

Well this looks bad.

We have at least 3 of the 4 reactors at the Japanese Nuclear facility at the Fukushima having had major incidents. At least 2 have lost cooling and the fuel rods in them are believed to be melting. This will not only mean their materials will recombine in different, and potentially more lethal geometries, but also that the cooling of the reactor may not be possible to effectively restart as the passages through which cooling fluid would travel may now be blocked.

The remaining water will have boiled and nuclear and chemical reactions have generated hydrogen which will, thanks to the chemical properties of hydrogen, raise the pressure in the reactors to a level that containment can't handle - hence the venting and presumably the higher levels of radiation being observed.

Looks bad.

It is.

But it could yet get worse in the main containment vessels are breached allowing air into the reactor ( fire - are the moderator rods graphite ? ) and the China syndrome meltdown through the base of the reactor into the ground as the core melts it's way downwards. Remember if you heat steel enough it loses its strength and then will just collapse. I assume there is concrete around the reactor vessel also which may offer some further containment.

The mixed oxide fuel is likely to become an issue also as it has probably been manufactured either in the UK or France and certainly was used in our older reactors ( of the type we will need to keep running beyond their design lives thanks to the green delusion our politicians have been involved in ).

Did things need to turn out like this ?

Not really is my guess. The big mistake hear seems to have been speed of reaction to the unexpected failures. We are told to believe that the diesel pumps ran out of fuel. Why wasn't heaven and earth moved to get more fuel as a matter of national emergency ? Is this a case of the virtues of calm deference that are serving Japan so well over the Tsunami disaster being the last thing needed in a rapidly evolving emergency when the people on the scene need to be empowered to act ?

There is a term int he nuclear world "Maximum credible accident" and this is starting to look like it to me. If it is the failings may turn out to be as much human and cultural and technical or geotechnical.

Maximum credible accident was also a fictional story about a fast breeder reactor program which would have justified the Ultra Vox treatment.

For those old enough ...



PS Don't get me wrong the video is guff and I'm a supporter of nuclear power. We just need to know what we're doing. Nothing is without risk.

See also - The First Pot's nuclear expert things things are already beyond repair - see here.

2 comments:

Techno Mystic said...

That version is blocked. Try the version uploaded by EMI themselves.

Man in a Shed said...

Thanks - I switch3ed version. I guess EMI know how to track events !