Battery powered nuclear plant coolant pumps

[ScottI2R]

Hello everybody,
In lieu of the disaster in Japan and the loss of power to the reactor coolant pumps, I have read that they are powering the pumps with batteries. While I am familiar with universal motors, I cannot fathom one of the size required to cool a reactor. Unless they are ac motors being powered by battery powered inverters I don't understand what kind of motors they are running and how they are doing it. If anybody can tell me this, can you please enlighten me.

Thanks,
Scott

In a hundred years, it isn't going to matter anyway.

 

[electricpete]

Hmmm. Where did you see the part about the batteries?

Typically a nuke plant will have several redundant diesel generators providing ac to several redundant pumps for each safety-critical application such as residual heat removal. These safety-critical pumps are much smaller than the main coolant pumps used during power operation since much smaller amount of heat is being transferred and much smaller flow.

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(2B)+(2B)' ?

 

[electricpete]

It will probably be more relevant to follow this event in the nuke forum:
thread466-294228

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[electricuwe]

I'm also suprised about what I'm hearing and reading in the news.

It's true that nuclear power plant have battery based UPS systems as well as diesel operated emergency generators.

Usually the battery based UPS system is designed to supply some essential control systems and the turbine bearings oil pump without interuptions, but not to ensure cooling for extended periods. This would be the task of the emergency diesel generators.

But beside this electrical systems there may be a small auxilliary steam turbine provided than operates an auxilliary coolant pump.

But I do not know any details about the schem of the plant in Japan.

 

[waross]

As I understand the scheme in one nuclear plant;
I am not sure whether the pump was feed water to the heat exchanger or the heavy water circulating pump. It was about 10,000 HP. There was a very large battery room to supply the inverter. The inverter kept the pump running until the emergency diesel generator was up and running.
The point is, size is not an impediment when it is vitally important that a pump be kept up and running in a nuclear plant.


Bill
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"Why not the best?"
Jimmy Carter

 

[electricpete]

I think most nuke designs are similar to what was described by electricuwe.

The plant I am very familiar with has dc pumps on the secondary side (lube oil backup), but no dc pumps associated with safety systems except some backup pumps lube oil pumps and similar auxiliaries associated with the diesel generator. The safety pumps such as residual heat removal, containment spray, safety injection (low-head/high-head), essential cooling water, component cooling water are ac induction motors ranging from 350 hp to 1000hp at 460vac and 4kv. They are designed to be driven by off-site power or on-site diesel generators.

The safety-related inverters powered from battery bus produce 120vac for non-motor control type loads. As a backup to the inverter, there is an alternate supply to the safety 120vac panels which is a constant voltage transformer. The only way to get 460vac would be to feed from batteries to inverter to 120vac and backfeed through the constant voltage trnasformer to 460vac. I don't think the batteries would last very long, and that is not a designed strategy. The designed fail-safe strategy relies on off-site power being available or at least one of several redundant diesel generators being available.

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[ScottI2R]

Gentlemen,
Thank you all very much. ElectricPete: I read about the batteries in one of the articles cnn had on its webpage when they first started talking about the power plants. Also, I was a little perplexed about what forum to post this in originally, but I decided to go with this one because at the basic level, it is a motor question. And thank you for the link.
Waross: That was the scheme I was envisioning and hence, the basis for my post. Unfortunately in this case, the redundant diesel generators were flooded by the tsunami. I guess next time they will put them on a roof.







In a hundred years, it isn't going to matter anyway.

 

[rmw]

Or at least on the turbine deck level.

rmw

 

[ScottyUK]

I'm not from a nuclear generator, but my understanding is that the gas circulators in the British AGR design are maintained by battery-backed medium-voltage inverters in the event of a loss of auxiliary power. These pumps are by no means small machines although I'm not certain of the exact rating.

Emergency power generation at some AGR stations (if not all) is from an aero-derivative gas turbine rather than a diesel, possibly a modified Rolls-Royce Avon engine as the AGR stations pre-date the Trent and RB-211 by quite some years.


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If we learn from our mistakes I'm getting a great education!

 

[zeusfaber]

Without knowing, I would have expected Tynes, Olys or Speys - those were the ones they did marine variants of, so easy candidates for conversion to GTAs.
A.

 

[ScottyUK]

zeusfaber,

You may well be right. I have some old notes which were scribbled long ago - I made the odd mistake back then. Not like now. [LOL]


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If we learn from our mistakes I'm getting a great education!

 

[zeusfaber]

I should have Googled it first. Not only did they make an industrial derivative of the Avon, But they sold over a thousand of the things. You were probably right.
A.

 

[electricpete]

The designed fail-safe strategy relies on off-site power being available or at least one of several redundant diesel generators being available.

I forgot to mention steam... in our plant, some of the redundant safety pumps use steam turbines and do not rely on any electrical power. That is a pretty common strategy to provide diversity among redundant pumps.

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