TEPCO Rose

[PamW]

42. You need to cool a reactor..

RobertEarl,

Yes - you need to be able to cool a reactor; both while it is operating, and after shutdown because the reactor is hot, and it has radioactive material in it. How many people here have a video projector, or a slide projector, or use either one at work? What happens when you turn it off? The fan still runs for a while in order to cool down the hot light bulb. The manufacturers warn you not to unplug the projector until the fans turn off.

That's what it is like for reactors. They need cooling when they are operating and they need cooling just after they shut down.

Nobody "forgot" that the Fukushima reactors needed water. In order for the water to do its job of cooling, that water has to be pumped from reactor to heat sink and back. The coolant pumps in the plants are electric, and so the operator have to be sure they have a reliable source of electricity.

In the case of Fukushima, they had the grid as a backup electric power source, and they had their backup diesel generators. The earthquake took out the grid. That left the backup diesel generators which were working for the first hour after the earthquake. However, that's when the tsunami hit.

You'll get no argument from me that TEPCO did some really poor planning in how that plant was configured. Fukushima would NEVER have been licensed in the USA. The fuel tank for the backup diesel generators was located above ground at dockside for easy refueling. The tsunami swept that tank away so there was no fuel for the backup diesels. Additionally, they put the diesels in the basement along with their switchgear. The tsunami flooded the basement and took out the diesels and switchgear. Without those diesels, they didn't have electric power for the coolant pumps, and had to resort to venting, which released radioactive material to the environment.

The NRC wouldn't allow a reactor in the USA to have diesel generators in the basement. When I was a graduate student at MIT, we toured Boston Edison's Pilgrim Nuclear Power Plant. Pilgrim is a GE BWR with Mark I containment like Fukushima. We were on one of the upper floors of the reactor building following our guide, when we came upon two big diesel engines. After viewing the diesels, we got into a nearby elevator and rode up about two floors, and we were at the top floor of the reactor building. So I know personally that the diesels in the Pilgrim plant are high up in the reactor building and not in the basement.

Reactor operating companies in the USA also have some imaginative ways of ensuring that they have electric power in addition to the grid and diesels. One of the largest operators of nuclear power plants in the USA is Exelon which own / operates all the nuclear power plants in the Chicago area; the largest concentration of nuclear power in the USA. Exelon also owns the Peach Bottom plant in Pennsylvania on the Susquehanna River, just north of the Pennsylvania / Maryland border. Just south of that border, on the same river is a "run of the river" hydro-electric dam called Conowingo Dam:

http://en.wikipedia.org/wiki/Conowingo_Dam

The dam was built in 1926. However, the Conowingo Dam is just downstream of the Peach Bottom Nuclear power plant. Exelon, which owns Peach Bottom, also bought the Conowingo dam. There is a dedicated, underground powerline from the dam to the Peach Bottom nuclear plant. Conowingo dam is another backup power source to run the coolant pumps at Peach Bottom should they lose both the grid and their diesel generators as Fukushima did.

I'd say Exelon is doing better planning than TEPCO did.

PamW