Belt and Suspenders thread - what safety upgrades should older BWRs get?

[zapperzero]

I'll start it off with a nice idea I found in another forum:

http://www.energyfromthorium.com/forum/viewtopic.php?f=51&t=3433

Solar panels on the roof to keep battery banks for instrumentation and valves charged. Lovely and relatively inexpensive, might avoid the need for bigger battery banks in some setups.

 

[gmax137]

How rugged can you make a solar panel? Seismic, tornado proof, etc. might be hard to do. Even without a tornado, a 'regular' hurricane sends a lot of debris flying through the air (rocks, dirt, coconuts, signs, etc.)

 

[Rive]

My opinion is that well set redundant EDG-s are much more reliable than well set redundant EDG-s with solar addons.

Especially at night.

 

[jim hardy]

When all else fails you get out the jumper cables.

my 2 cents:
Emergency connections for portable generators and pumps
Annual drills on how to hook them up
Walkdown of systems to make sure everything needing manual operation will be accessible in post accident environment
Submarine hulls surrounding emergency diesels and switchgear wherever flooding is credible.
12 volt DC instruments on a small set of instruments necessary to monitor water inventory and heat transfer from core.
there's plenty of regulatory action afoot.

http://www.nrc.gov/japan/japan-info.html

Parkinson - "...defensive measures are best organized locally."

 

[rmattila]

I'm a bit worried that the common-cause failures in the plants' internal AC distribution systems (switchgear, busbars etc.) and the potential problems caused by loss of DC and ill-balanced fail-safe modes have not yet deserved sufficient attention, as everybody is concentrating on the "easy" stuff of adding an air-cooled bunkered or mobile diesel generator and being happy with that.

It was the distribution, not the supply that failed in Fukushima, and that's something that in my opinion should be looked at more carefully.

 

[Yamanote]

After I have seen the footage how severely the plant was hit by the tsunami, I would simply conclude a tsunami-prone shoreline like the one in Fukushima isn't the right place for a nuclear power plant.

Due to flooding all the switchgear including DC battery power was lost immediately after the tsunami and there was not much chance to connect any external power source. All lights went out and important valves were left in an unknown state. So it was not possible to fix the problems within the given time span of one to two hours. And besides that they had lost the ultimate heatsink anyway, as all seawater pumps were gone.
Fukushima Daini was on the edge and showed the limits, Daiichi went beyond and failed.

Ok, let's be a bit more constructive...
First of all they would have needed watertight switchgear to keep their electrical equipment running. If you don't want to end up with batteries, you have to provide diesel generators with secured fuel supply. Taking the adverse conditions (earthquake, tsunami) into account, 8 hours of battery life aren't enough.
Well, all this wouldn't have fixed the problem with the ultimate heatsink...
That might lead to a passive cooling system that would work ideally without any electricity. But one also needs sufficient makeup water and the possibility to do a scrubbed containment vent in time with staff being trained for that.

When one thinks about these points for the first time while the core is melting down already, it is too late.

 

[tsutsuji]

About solar panels :

http://www.nikkansports.com/general/news/f-gn-tp0-20111002-844020.html According to the records of solar-powered seismometer(s), explosion happened only once on 15 March at 06:12 AM. It is inferred that it is the explosion at unit 4. The reason why no hydrogen explosion occurred at unit 2 is that, by chance, [unit 2's] blowout panel was removed by unit 1's explosion, enabling the hydrogen gas to be released to the outside.

The details on Tepco's seismometer analysis are available in the internal investigation interim report　http://www.tepco.co.jp/cc/press/betu11_j/images/111202c.pdf

Interim report English version : http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/111202e14.pdf page 95 (105/166) "provisional seismological recorders set up within the premises of the Fukushima Daiichi NPS." (so they don't mention that they are solar-powered)The nikkansports.com link is broken, so here are alternative links for the Kyodo news mentioning that the seismometers are solar-powered :

http://www.kyodonews.jp/feature/news05/2011/10/post-3570.html & http://www.sankeibiz.jp/business/news/111003/bsc1110030502004-n1.htm (3 October 2011) : "It turned out later that solar-powered provisional seismometers set up within the premises of the Daiichi NPS had been continuously recording tremors".

 

[zapperzero]

When one thinks about these points for the first time while the core is melting down already, it is too late.

Of course. This is the reality we live in, though. There is any number of aging plants situated on shorelines, in Japan and also in other countries.

 

[zapperzero]

How rugged can you make a solar panel? Seismic, tornado proof, etc. might be hard to do. Even without a tornado, a 'regular' hurricane sends a lot of debris flying through the air (rocks, dirt, coconuts, signs, etc.)

You can make it as rugged as the roof itself. It can BE the roof, if you so wish.

 

[zapperzero]

That might lead to a passive cooling system that would work ideally without any electricity. But one also needs sufficient makeup water and the possibility to do a scrubbed containment vent in time with staff being trained for that.

All these things were present at Fukushima Dai-Ichi. There is the isolation condenser which only needs makeup water (but relies on electrically operated valves), a filtered vent (which has insufficient capacity for emergency venting) and trained staff (which dithered and ignored their training and their SAMG apparently).