Question on Nuclear Power plant back-up generators

[Old and In the Way]

I posted the following on another thread, but started my own thread to give it more visibility - I hope someone who has far more knowledge about Nuclear Plant construction can help explain this to me-

What I don't get is...they spend 100's of millions of dollars on redundant safety systems, yet something obvious like the location of system critical back-up generators in a tsunami/earthquake zone seems to be done without regard for this most probable catastrophic scenario. Why not mount these generators on top of the building where the tsunami couldn't have destroyed them? What am I missing here? Is there a reason why that couldn't be done? No doubt that the roof would have required some reinforcement to support...but in the overall scheme of things, that would have been peanuts compared to the situation they face now.

[buddysmellgood]

1. I read that a back up generator was brought in but that the electrical

connections didn't match. I'm thinking that must be bull. Why wouldn't you just cut the connections and splice the copper together?

[no limit]

4. I haven't read that. But the voltage and the phase need to be right

if they aren't you can't simply splice the connections and connect any generator that you want.

[Old and In the Way]

7. Another thought....why wouldn't they have had mobile generators/fuel

depoted om higher ground and available to relocate quickly? Seems like another option that would have made sense.

[JVS]

6. I read that the place where backups would be plugged in was under water and inaccessible.

[buddysmellgood]

9. That makes sense. I wouldn't think connecting a new power supply

would be an insurmountable engineering challenge.

[godai]

2. Good question...I don't know where the generators were located.

But, based on the failure, if you see the 'after' photo', everything in front of the reactors was damaged or destroyed. If the generators were there, that sounds like criminal negligence.

[Old and In the Way]

5. I could be wrong, but my understanding was the BU generators were

destroyed during the Tsunami and flooding. If so, why would they locate them on the ground when your plant is sitting literally on the edge of the ocean?

[Statistical]

3. As an alternative the generators should have been in a building

that could have withstood the tsunami (like containment building did). Maybe even with a 20ft "snorkel" to ensure it could run even if completely underwater. These generators are rather large not sure you would want them on top of a building in an earth quake zone.

Another thing should be a standardized international connector and quick connect system for remote/mobile generators. I am sure there will be plenty of lessons learned for the industry.

That being said even better design is GenIII+ reactors which can be cooled passively without any power of human interaction.

[Old and In the Way]

10. The buildings seemed to have survived a 9.0 quake OK.

Had a stronger quake toppled the building....maybe the power plant would have been a moot point. Just seems to me that the added cost of beefing up the outer building to support BU generators and a fuel reserve, given the location at the edge of the ocean, in a tsunami prone region, would have been the logical choice. Your option about a breathable system is interesting, but running hi-voltage juice underwater would have it's own problems if the earthquake had damaged the waterproofing necessary.

I'll have to ask my brother, who does mechanical licensing for start-ups of conventional power plants, about this..

[somone]

8. Diesel generators for nuclear plants are not small:

http://www.nucleartourist.com/systems/diesel1.htm

[Old and In the Way]

12. True....but the added cost might have been the difference between

plants that are operational today vs. a total, multi-billion dollar loss.

[kirby]

11. It is the way some engineers / managers think...

They plan for an Earthquake but not a Tsunami or vis-versa. Or the engineers say it needs be in location A but to work around some other issue someone grants a waiver.

Or in this case the design of the reactor pressure vessel (which appears to be holding up so far) was only specified for an Earthquake of a 7 times lesser magnitude. WTF?

[Old and In the Way]

13. You'd think that in the planning stages for these plants that

there'd be a 'worst case scenario' gaming outcomes and possible solutions. Lets see, we're on the coast in a region with a long history of strong earthquakes and resultant tsunamis....what if we lost power and had to rely on the back-up generators?

[kirby]

16. There probably was...

And the final decisions was based on a set of compromises and rationalisations that fit the budget and other constraints.

[snagglepuss]

14. This is what happens with unregulated capitalism. Adequate safety cuts into

the bottomline so only the bare minimum is spent on safety and even then corners are cut.

[Old and In the Way]

17. Especially if there's a cap on liability for catastrophic failure.

It will be interesting to know what the taxpayers of Japan are ultimately on the hook for. Without the caps, maybe the energy corporation behind the investment thinks twice about risking bankruptcy on these plants. Or does a better job of insuring his investment. But with an upside cap, the incentive to add costs for better protection becomes less of an issue.

[MadHound]

15. It's for a few possible reasons,

First, the design of the roof, and the building of the roof, were probably carried out by two separate contractors. The contractor who did the roof only built the roof to the specs required, and didn't reinforce it for massive diesel generators.

Thus, the generator contractor was forced to put them at ground level.

There are other things into consideration. Diesel is mildly corrosive, what would a lifetime of spills do to the roof. Refueling would be a massive pain. Costs would be enormous. Vibrations from running the generators could weaken the roof over the ensuing decades. Fire danger.

They could have installed a massive breakwater around the generators however, that would make more sense.

But what completely blows me away is the fact that they put these reactors on the coast line to begin with. I mean really, in one of the most seismically active areas of the world, which is also prone to massive tsunamis, you would think that they would have the brains to at least locate the reactor inland, out of reach of the ocean.

[Vinnie From Indy]

18. The problem was obviously in the design phase, not the construction phase

The architects determine where shit goes and the contractors build to their spec. This appears to be a massive failure of design caused most likely by criminal negligence brought on by greed. It is a story as old as time.

[Old and In the Way]

19. Siting location of the plant sure seems like a questionable call.

I suppose proximity to industrial, commercial, and residential areas was a factor...but there was a suitable location 100ft above sea-level?

Perhaps a rooftop location over the containment vessel for the bu generators wasn't the best option, but they could have poured a pad, erected structural steel/platform that was next to the plant and had the same level of protection. I just can't believe that they locate their generators on the ground where the most probable cause for the power plant shutdown would be an earthquake and resultant tsunami.

[Old and In the Way]

20. A shameless kicking...