meltdown question

[ivymike]

ok, so a neighbor of mine used to work at the Japanese nuclear plant that's having the trouble currently. He's a bit of a blow-hard, and this evening he decided to bend my ear about the reactor. He said that he can't see why they're having so much trouble with it, they must just be trying to save money by not draining the water. I said that it sounds like they're having a heck of a time avoiding melting of the fuel and eventual loss of containment. He responded "all they have to do is drain the water and the fission will stop." I was like "um, no... they need the water in there to slow the reaction and help remove heat" He said "no, it's a fast neutron reactor, and the water is where the fission happens. if you drain the water, the fission will stop, but it'll get hot inside." Anyway, he started doing his "you have no business questioning me" routine, so I left. A quick look on wikipedia convinced me that I was more right about it than he was (boiling water reactor, and water helps to moderate), but it left me wondering whether there were any grains of truth in what he was saying, or things that he could have been told and misinterpreted during a safety course or similar. Are there any reactor designs where draining the water inherently results in stopping the fission?

 

[TheTick]

Ideas for the future:

Build reactors in holes or tunnels or surrounded with levees that can be flooded.

Containment structures with flexible balloon-like elements that can survive "rapid expansion" without blowing out the walls.

 

[MintJulep]

The French apparently have robots designed for nuclear accident work.

They are on the way to Japan now.

 

[KENAT]

Zut alors.

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[patprimmer]

It took them quite q while to step forward "or" for a previous offer to be accepted.

Air is pretty elastic, so a bigger containment volume, or an extra level of containment with the total volume much greater.

Being built in a bundered area seems so basic it is hard to believe it is not standard procedure. I know it is with new pesticide formulating plants here.

One possible disadvantage in this case is that it might have retained the tsunami wave water, making the site even less accessible, maybe? Also maybe doing more damage to the pumps, but also maybe making them less needed.

As this is NOT my area I may be sprouting total garbage.

Regards
Pat
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[IRstuff]

Well, it's clear that any new reactor will have to show at least one additional completely independent coolant supply to get construction approval in the future. Clearly, single, even double, or triple point failure analysis is not sufficient for the potential downside of these plants. This will probably add 10% to 20% to the already high cost of a nuclear facility.

TTFN

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[MikeyP]

In the dim and distant past, I remember a school trip to Bradwell-on-Sea Magnox reactor. I seem to remember that the cooling system was normally driven by electricity generated from the plant, but they had 2 independent coal and diesel fired generator AND a gymnasium sized room chock full of lead-acid batteries "just in case". Essex doesn't see that many Tsunamis, I admit...



--
Dr Michael F Platten

 

[KENAT]

Mikey, I seem to remember most UK reactors are fundamentally different from those in other countries as they are CO2 cooled not water cooled.

I also vaguely recall the early ones at least had complex filters installed on some of the vents/towers or something so that if radioactive gas/particle mix did get vented it would get partially cleaned and limit contamination.

These filters were considered a big waste of money, called 'XXX follies' where XXX was the name of the guy that insisted on them. Then they had an accident, the filters worked as planned and suddenly seemed like good value.

Of course, my memory may be playing up.

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[MikeyP]

That's right, the fuel packaging was supposed to make it more safe in the event of a coolant failure, also the reactor vessel is pressurised in normal use, so it's designed for high pressure.

But still a large accumulator system to provide at least some independent power to the cooling system would be a benefit? - Maybe it was washed away by the water.

--
Dr Michael F Platten

 

[btrueblood]

"...you send the robot in and when they're nearly dead pull it out, or it has auto recovery or something"

Vision of now highly radioactive robot "homing" on its suddenly reluctant master, its damaged CPU not responding to commands to stop - "Robbie go home" - "Stay away from me, Robbie!"...

 

[ScottyUK]

MikeyP / Kenat -

Google the Advanced Gas-Cooled Reactor, or AGR. A very different animal to the PWR / BWR designs and with much higher efficiency, it was a brilliant design which was beyond the limitations of the materials available to its designers in the 1960s and 1970s, which has resulted in a justifiably poor reputation for availability. Built today and with modern materials and methods it would likely be very popular.


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