hindsight- how to avoid repeat of Fukushima 4

[davefitz]

In anticipation of the need to incorporate "lessons not quite learned" from the last 3 meltdowns, here is my list economically and technically achievable means to avoid repeats:

a)add a hardwired, remote , backup operating room 0.7 km away from the reactor.
b)spent fuel storage pool located at least 0.5 km away from reactor
c)backup diesel genset at ALL coastal plants to have inlet air snorkel be at least 10 M above sea level. Ditto exhaust discharge nozzle.
d)use geopolymer concrete for containment dome- at least for the foundation- tolerates much higher temperatures than ordinary portland cement concrete.
e) (??) develop and implement a stirling engine based backup circ pump that is driven by primary coolant discharge , air cooled at cold end
f)(??) onsite mandatory storage of sufficient boric acid for loss of coolnat events- perhaps stored in a pressurized local accumulator that can be immeidiately discharged to the core , based on 2 independent keyed switches plus control system confirmation loss of coolant for ( XXX minutes).

 

[patprimmer]

And personnel convicted of falsifying maintenance and safety documents be charged with careless disregard and get similar sentences to manslaughter.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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for site rules

 

[unclesyd]

It looks like there a few hills nearby so why-not a large tank,10,000,000 of water connected to the plant by underground lines for use in emergency.

At our plant is the river water fire protect water supply is backed up by 2 elevated water tanks, one ours and the other by the local utility, 3 500 hp diesel pumps, 2 steam turbine pumps,
2 1,500,00 gallon storage tanks, and the cooling tower water that is fed by our wells.

 

[polymathjack1234]

My understanding of the problem:

-Since SCAM, the reactor has stopped generating heat.
-without circulation of coolant, the latent heat of the fuel rods is causing the coolant to boil and increase the pressure inside of the reactor.
-if the coolant boils away without being replaced with fresh coolant, the fuel rod casings will become exposed, "burn" and eventually melt.

Am I understanding everything right?

If this is the problem, would it be possible to use a coolant with a higher boiling point than water to cool the reactor without the coolant boiling away? For example molten lead, zinc, copper, or aluminum? Would it be advantageous?

In terms of prevention instead of countermeasures:
What about running BWRs underwater at depth so that ambient pressure is higher, and the difficulty of pumping in fresh coolant is lower?

The impact of tsunamis and earthquakes on submarines seems to be dampened by their environment. I would think that "china syndrome" would be much less dramatic when the waste is being diluted by an entire ocean rather than a limited supply of ground water and soil.

 

[cloa]

davefitz
which reactors (or powerplants) have any of those features to support your statement as to economically and technically feasible?

 

[itsmoked]

polymathjack1234; In a BWR the water itself is a moderator. The moderator is needed to slow the neutrons down so they have time to interact with the neighboring rod fission materials. Switching to something like metal might not get that done. Furthermore using something like molten sodium has lots of drawbacks of its own. Some metals will burn if exposed to air if they're hot.

Water also has a huge specific heat ,is easy to find, and doesn't burn.

Remember Chernobyl? A thousand tons of graphite. The big disaster multiplier was that carbon burning in air. That made unimaginably horrid amounts of rising hot particulates. It essentially acted like a radionuclide conveyor belt hauling away radiation emitting debris to land on Sweden amongst other areas.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[davefitz]

Cloa:
I have no proven examples of where these were installed.

My understanding is that several US plants ( but not all) have installed alternate or backup control rooms seperated from main room , and/or enhanced the rad protection of the control rooms with add'l concrete barriers, based on US NRC recommendations following TMI. Also, most US plants designed + built in the 70's are yet using original analog control systems, ripe for upgrade in any case .

Current control technology can be provided to allow remote monitoring and control without hardwiring- but meeting new NERC CIP rules is a neccesary detail that may be better met with hardwiring. In any case , the base assumption that an incident will not occur at a plant no longer appears to be the correct assumption , based on the known 3 incidents- instead, the design assumption may need to change to assuming an incident could occur, therefore one should include design features that would simplify the emergency response. Limiting operators to 1 hr in the control room, or even finding operators willing to work under the current emergency scenario, does not appear to be a rational design approach.

Other typical commercial facilities have "fire dept connections" for typical fires, it seems to make sense for similar design considerations apply to reactors, such as providing a means for emergency crews to better provide auxiliary supply of water to the spent fuel pool ( ie a permanent UG piped connection to a safe location at which another temp pump can access). The current event allows helicopters to spray water on the used fuel pool due to the roof being conveniently removed by an H2 puff, but relying on such a means of allowing access to the pool in an emergency seems somewhat bizarre, to say the least.

The most likely water inundation event for a coastal plant is the Tsunami, but that is not the only such event. I cannot quantify the risk due to an LNG tanker incident , or tactical underwater bomb, or antarctic ice shelf collapse, and it sounds naive to discuss them, but if a spent fuel pool does fail to the point of releasing elements to the downwind zones, the permanent impact of that event on agriculture, habitation, and genetic damage would need to be considered before dismissing them.

 

[zeusfaber]

-Since SCAM, the reactor has stopped generating heat.
-without circulation of coolant, the latent heat of the fuel rods is causing the coolant to boil and increase the pressure inside of the reactor.

Not latent heat in the conventional sense of the term.

Once a reactor has been running for a while, about 10% of the heat output comes from the radioactive decay of fission products (the rest comes directly from fission). When the reactor scrams, the 90% stops very quickly - but the decay heat continues, fading away over the course of a few days.

That means that just after shutdown, the core is still generating something of the order of 100 MW of heat. If this isn't removed, temperatures are going to rise.

A.

 

[electricpete]

I’m sure many lessons will become clear over time.

At this point in time, from my limited viewpoint, it strikes me that plant management should have brought a small team of industry experts into the inner circle of discussion very early on, simply for purpose of detached peer checks to make sure that no simple or obvious things were overlooked during the process of trying to manage a new, unfamiliar and chaotic situation.


=====================================
(2B)+(2B)' ?

 

[rmw]

Electric Pete,

Does your plant have a remote control room?

Anyone else reading this thread working directly for or with Nuke plants familiar with remote or alternate or backup control rooms?

I have been in a few Nuke plants both domestic and foreign (can count 'em on less than 10 fingers) but none that I have been in were so situated.

On the other hand, where I work now, remotely controlled power plants is almost the norm. And this would be real remote, miles and even states away. But they aren't Nukes

It is a novel concept.

rmw

 

[trottiey]

Fukushima Dai-ichi's problems mostly seem to revolve around the lack of electricity. This is in part because lines to the outside world were washed away by the tsunami. So how do you figure a remote control room would fare in those conditions? I'm sure someone will suggest burying the cables underground, but what happens if an earthquake opens up a rift in the ground?

Some people are talking about airlift-ready generators that would be plug-and-play with nuclear systems. I think that has more potential. If your power was guaranteed by those, and you use multiple-redundant wireless communications, then the idea of a remote, or even mobile, control room might make sense. But you're still going to need to send people into the reactor to force the stuck valves, look around to figure out why it's not working, weld together the broken stuff back together, etc.

 

[rmw]

I suspect that there are some ~20 MW mobile trailer mounted generator units in the bellys of Antonov's even as we write. More than one major package power manufacturer offers these.

The problem however is that once electricity is re-established regardless of whether that is through generators brought in or via new tie lines to the grid, any motors that were ground level or any lower level where the tsunami waters could get to them are wet and worthless.

I can't speak for the coolant pumps, or any pumps in the containment vessel, but for the BFP and the condensate pumps, and the cooling water circ pumps, they are typically located at ground level or lower elevations of the plant. Those are typically some pretty big motors. Wet and worthless.

So it is still a long way back even if the power gets reconnected some way.

rmw

 

[cloa]

The real answer is the procedures and design should have allowed and ensured that the plant could run isolated from the rest of the world for over one hour after a nearby earthquake underwater until the tsunami danger abated or made to be isolated later if the earthquake was far enough for tsunami to be detected then they could have isolated later than immediately. If the control room is breached, you have bigger problems then you have bigger problems than the control room- the plant is uncontrollable. Danici's control room is probably still secure but there is nothing they can do there- the engineering controls have failed.

 

[rasevskii]

I agree with rmw: Not only were the motors, switchgear, and other electrical equipment at or near sea level, submerged, it was actually operating and energized at the time. There would have been major faults as the seawater swept in, resulting in arcs and fires.

The main outdoor seawater pump motors, on the platform, at the intakes had to have been all submerged, likely also the feedwater pumps inside the building. These would be all HV motors in the several MW classification. In addition all other smaller motors and MCCs as well. The same for the Diesel Generators, also HV units with open-circuit aircooled generators likely in the 3 to 5 MW class, each.

The initail idea of bringing in portable generators had to have faltered due the above situation.

rasevskii

 

[msquared48]

In case the electrical grid breaks down, develop technology to the point where a backup failsafe command can be sent piggybacked via a very remote laser to a sensor that would remotely activate the Boron release to the core. The OP's item "f" is assumed in place.

Maintaining viable options is good. They just ran out of them.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[Zogzog]

It seems the water may have entered the DG's through the snorkel which was only a few meters high. On subs our snorkel had a valve that closed if it sensed water.

The NRC disussed in thier brief on CNN today making storage pools 1E. I was suprised they were not already.

Having trailer based generators and mobile substations in a safe location nearby, say 100 miles so plants could share that resource and maintenence costs.

 

[BJC]

Remoter control rooms are not complete. They are remote shut down stations. They have little to do with BOP systems.
They are not publized or on public documents as they can be considered part of the security system.

 

[mauner]

I think item C becomes irrelevant if switchgear and substations become submerged.
For the nuke plant I worked at, we would have to declare all of the EDG inoperable if the river water level became high enough to cause a problem.

I don't think its possible to get an instant type flood there, but coastal nuke plants must consider flooding due to all natural events.
I believe the standard review plan requires evaluation for flooding due to tidal surges from hurricanes and tsunamis.

As for a remote control station in older plants - they only exist for damage due to a fire in the control room. If there was a radiation hazard the remote control station could not be used because it was in the reactor building.

I think the security measures required to prevent unauthorized access to a remote control station off site will make it economically not practical. Although it would make a great movie. A terrorist seizes the remote control station or taps into the cabling between it and the reactor, takes control away from the operators and ...

 

[mauner]

I did find it interesting that the design basis accounted for 6.51 m surge and all the problems resulted when it was hit by a 7m surge. Excerpt from WNN

"One hour later the plant was inundated by a tsunami said to be seven metres in height, compared to design basis surge of 6.51 metres."

Maybe the lesson learned is that the design should consider the fact that Japan move 13 feet closer to the U.S.A and dropped 2 feet down below sea level. What if California dropped down below sea level by 2 meters added to a Tsunami wave? 2012 is just around the corner!!

 

[rmw]

A snorkle on a diesel generator is like tits on a boar hog. Sure the engine could breath as long as the snorkle stays above water, but what good is an engine when the generator and its electrical connections are under water?

rmw