Possible Source of Leaks at Spent Fuel Pools at Fukushima

[FBaggins]

Note - I believe the image is a generic early-model BWR with MK I containment. Not specifically one of the reactors at the plant.

A possible source of the leak in the Unit 4 pool may be the seals around the doors (or “gates”) on one side of the spent fuel pool. These gates are shown in the diagram below. They are located between the pool and the area above the reactor vessel. They are concrete with metal liners, and are roughly 20’x 3’.

When fuel is moved between the pool and vessel, this whole region is filled with water, the gates are opened, and the fuel can be moved to or from the reactor core while remaining under water. The water not only keeps the fuel rods cool but acts as a radiation shield.

When the gates are closed, they are made watertight by an inflatable seal, similar to a bicycle innertube, that runs around the sides and bottom of the gates. Electric air pumps are used to inflate these seals and keep them inflated as air leaks out of them over time.

These pumps are powered by electricity from the power grid, and not by backup diesel power or batteries. So once the power grid in Japan was knocked out, these seals could not be inflated if they lost air over time. If these seals lost air they could lead to significant water loss from the pool, even if there were no direct physical damage to the pool from the earthquake or tsunami. This may be what happened at pool 4, and could affect the other pools as well.



http://allthingsnuclear.org/post/3964225685/possible-source-of-leaks-at-spent-fuel-pools-at

[bluecoat_fan]

1. well that's a crappy design

It assumes you will never lose outside power and a lot of facility water at the same time.

[FBaggins]

2. Not quite.

You also have to lose backup power and battery power AND get a leak in this seal.

But of course that's what happened (except perhaps the seal).

[girl gone mad]

3. Considering all of the heat and pressure building up in the reactor after cooling was lost..

then that pressurized gas being vented into the area which contained the gates, it's easy to picture the seals bursting.

[Fledermaus]

4. FAIL!

Building large nuclear plants on the ring of fire at sea level...FAIL!

Building six large nuclear plants next to each other...FAIL!

Store all spent fuel on top of reactores....FAIL!

[Wilms]

5. Getting taxpayers to foot the bill...

"Winning the Future".

Yay!

:sarcasm: