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hindsight- how to avoid repeat of Fukushima
4

hindsight- how to avoid repeat of Fukushima

hindsight- how to avoid repeat of Fukushima

(OP)
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).

 

RE: hindsight- how to avoid repeat of Fukushima

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

Regards
Pat
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RE: hindsight- how to avoid repeat of Fukushima

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.
 

RE: hindsight- how to avoid repeat of Fukushima

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.





 

RE: hindsight- how to avoid repeat of Fukushima

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

RE: hindsight- how to avoid repeat of Fukushima

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

RE: hindsight- how to avoid repeat of Fukushima

(OP)
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.  

RE: hindsight- how to avoid repeat of Fukushima

Quote (polymathjack1234):

-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.

RE: hindsight- how to avoid repeat of Fukushima

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)'  ?

RE: hindsight- how to avoid repeat of Fukushima

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

RE: hindsight- how to avoid repeat of Fukushima

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.

RE: hindsight- how to avoid repeat of Fukushima

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

RE: hindsight- how to avoid repeat of Fukushima

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.    

RE: hindsight- how to avoid repeat of Fukushima

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

 

RE: hindsight- how to avoid repeat of Fukushima

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

RE: hindsight- how to avoid repeat of Fukushima

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.  

RE: hindsight- how to avoid repeat of Fukushima

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.

RE: hindsight- how to avoid repeat of Fukushima


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 ...  

RE: hindsight- how to avoid repeat of Fukushima


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!!

RE: hindsight- how to avoid repeat of Fukushima

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

RE: hindsight- how to avoid repeat of Fukushima

"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."  
Poison pumps are powered from the emergency power system. For that reactor they are piston pumps.  The boron solution is a solid at room temperatures.  The injection lines have to be heat traced. There is a squib valve between the pumps and the reactor.

  

RE: hindsight- how to avoid repeat of Fukushima

How about if they re-configure the shutdown command (or is it an emergency procedure) to allow for the immediate run-up/ re-synchronization of even the smallest unit (I guess in Fukushima Dai-ichi it was Unit No. 1 - 460MW) to prevent a total blackout at the plant site? If Fukushima Dai-ichi site has six units, perhaps the total in-house loads could load that unit by some %! (That is assuming the auxiliaries power centers were not damaged during the tsunami). If it took them 1 hour running on emergency diesels, they should have ample time to cut-back in one nuke generator, line up the emergency cooling systems to take power from that nuke unit before the emergency diesel got swamped over.

RE: hindsight- how to avoid repeat of Fukushima

Sure, bringing one reactor back up to cool the others might work, with some cleverness to override xenon poisoning and reject the excess heat. But now you're playing double-or-nothing. You've just turned a nuclear reactor back on right after it went through a record-breaking earthquake, and you haven't had time to give it a full inspection for damage. What if the coolant pumps are toast? Do you want a risk of loss of coolant on three shutdown cores, or a risk of one on-power core out of control?

You may be interested in thread466-294381: Japanese nuclear accident FAQ where several of the same back-up power issues were discussed.

RE: hindsight- how to avoid repeat of Fukushima

Any Daiini is not that far away and its fully shutdown so they could bring it only a few percent online and supply plenty of power.   

RE: hindsight- how to avoid repeat of Fukushima

Quote (trottiey):

Sure, bringing one reactor back up to cool the others might work, with some cleverness to override xenon poisoning and reject the excess heat. But now you're playing double-or-nothing. You've just turned a nuclear reactor back on right after it went through a record-breaking earthquake, and you haven't had time to give it a full inspection for damage. What if the coolant pumps are toast? Do you want a risk of loss of coolant on three shutdown cores, or a risk of one on-power core out of control?
Yep, I guess xenon135 and samarium149 poisons the fission reaction after each nuclear trip but I guess you always have a poison override window right after a trip. Given the facts in Fukushima Daiichi, it seems the turbines and the steam generator/ nuclear reactor rode-thru the quake with out damages. I was basing my suggestion on the fact that for any external faults to the generators, it is possible to immediately run-up and bring the unit back to the system.

The good thing with a well-designed unit control is that you cannot line up the unit for connection back to the grid if the lockouts are not reset; and you cannot reset if there are problems detected by the relays' sensors. So, in effect, if a trip occurs and the unit elements get damaged, you can't run it back, answering your fear of putting back a unit which experienced a very strong quake.

RE: hindsight- how to avoid repeat of Fukushima

2
There are a lot of interesting ideas stated above.  I certainly don't want to discourage discussion, but unfortunately most of the suggestions above won't work.

I have worked in the nuclear industry for 13 years, so here are the facts and my 2 cents:

 - Fukushima was hit with a beyond design basis event.  The information I have is that they lost offsite power as a result of the tsunami, and then went into a station blackout (SBO) condition as a result of tsunami damage to the fuel supply to the diesel generators.  

 - Most US plants are designed to accommodate about 4-8 hrs in a SBO.  During this time steam driven pumps were used at Fukushima.  Power is needed for instrumentation and controls, which comes from batteries.  The batteries eventually need power to be charged, so when they go dead, you have nothing.  At Fukushima, this happened after about 8 hours.

 - As a result of this event, the NRC will likely ask most plants in the country to evaluate their capability to withstand an extended SBO condition, and plants on the coast lines will need to consider their capability to withstand a tsunami (or a seiche for an inland lake or reservoir).  I also imagine that the beyond design basis procedures will be upgraded with possibly a focus on safely venting off hydrogen gas with no power without causing an explosion.

So for the ideas proposed above by davefitz:

 a - No US plant has an offsite control room.  That would be an incredibly bad idea, and would not have helped at Fukushima since they had no power.  All control rooms are right in the middle of the plant.  The control room must be an incredibly robust room with independent ventilation systems and tight security.  The offiste facilities are typically just emergency response centers (desks and telephones).

 b - The SFP will always be close to the reactor because the fuel must stay underwater (for shielding and cooling).  Storage facilities that are farther from the plant are dry fuel storage, which does work, but not for fuel assemblies that have recently been used.  And you still need a pool for a core offload.

 c - Elevated air inlet and exhaust air for diesels is definitely a possibility.  But the external fuel supply is what caused the problem, and that needs to be looked at.

 d - No need to change concrete type.  Normal concrete works just fine.  Tearing down and rebuildling every containment in the US won't happen, and the NRC would never allow the use of an unproven and untested type of material, and it would also be cost prohibitive.

 e - Many plants have steam driven pumps that use steam produced from the reactor to operate.  They still need power for instruments and control valves.

 f - Plants already have this.  Boration is not the issue.  It is long term removal of decay heat and loss of coolant inventory due to boiling.

And for the other ideas:

  - Starting up a reactor just after a beyond design basis event would never happen.  This would be incredibly reckless and foolish.  You never start your reactor back up until you fully understand why it shut down and have performed inspections and surveillances on plant equipment as required.

 - Changing coolant is not an option and is not needed.  You would need an entirely different type of plant.  The type of coolant is not the issue.  

 - An additional huge tank of water is not needed since all plants will have an ocean, lake, reservoir, or river to get water from.  

Here are some better ideas:

 - Tsunami proof emergency power and upgraded beyond design basis event procedures.  Ensuring power is available addresses both core cooling and SFP cooling.

 - Passively designed reactors that can cool using natural circulation and require minimal emergency power.  Some new reactor designs are this way (AP1000).

 - Improved hydrogen venting capability to prevent explosions.

RE: hindsight- how to avoid repeat of Fukushima

"No US plant has an offsite control room"

No commercial plant :)

RE: hindsight- how to avoid repeat of Fukushima

Correct Zogzog.

All of my statements above apply only to the light water civilian nuclear power plants in the US, and are not meant to be applied to any other type of reactor.

RE: hindsight- how to avoid repeat of Fukushima

(OP)
rcchap:

Good points all, and thanks for the education. Yet I still take issue with 2 items, going forward.

a) Today's availability of a DCS  system makes it a nearly trivial task to allow a plant to have a remote control room for emergency use. That technology has been available since about 1985 ; being developed after the bulk of the US plants were built . Certainly the main control room needs to be close-coupled to the operating equipment  for all the practical reasons you discussed, but after  3  emergencies, one can no longer pretend they do not happen. The most likely future emergencies at  overseas plants would be war related ( Pak vs India, anyone vs Iran, asian conflicts are feasible) , but other causes are plausible, depending on your imagination- GPS spoofing  or solar flares upsetting the synch of the grid, smart transmission system  programming faults, and natural catastrophes.

b) the F-D-I 1-6 instant crisis shows an equal risk being associated with loss of coolant for the SFP- in hindsight, if each pool had been supplied with 2  redundant 12" NPS pipes  routed from the pool to a termination perhaps 0.5 km away, then emergency crews could safely concentrate on supplying a coolant fluid loop to the pool when local devices have failed and local activity cannot be conducted .

Although the news reporting  normally focuses on local damage caused by the event, there is  long term damage that occurs far from the site that effects other countries, so perhaps there also needs to be an international agreement along the lines that war time targeting of such sites which  leads to a level 5+ event represents a "crime against humainty " or some other such prohibition.
 

RE: hindsight- how to avoid repeat of Fukushima

davefitz:

We can agree to disagree I guess.  I know that there are advanced digital technologies out there, but they are rarely used in the nuclear industry, and would definitely not be used for reactor control.  We keep it simple and analog.  A networked control room will never happen because some hacker would find a way to cause problems.  The current cyber security requirements already in place are very restrictive, and they are getting more restrictive every year, and these requirement would preclude a remote control room using a network.  

There are digital computer systems used at plants to monitor parameters only ... they have no control functions.

There are also alternate control panels at the plant for specific equipment that are used in the event that the control room is uninhabitable due to a fire.  These panels are inside the plant are used to control safe shutdown.

Keep in mind that if the plant is in an SBO condition, it doesn't matter where the control room is ... it is useless without power to the plant.

As for the SFP, I agree that upgrades should be done to be able to provide water to the pool during an extended SBO condition.  The cascading series of events that unfolded at Fukushima where a core melt event turned into damage to the SFP and loss of SFP inventory clearly identifies an opportunity for improvement.  Many plants have evaluated redundant methods that can be used to provide water to the SFP (including transferring water from various holdup tanks and using other cooling water systems or even fire protection).  However, all of these methods require power.  I imagine that this will be looked at very closely in the coming months.

On another subject, I have seen a report where Isolation Condensers were considered for installation at Fukushima, but it was decided not to install them.  These would allow removal of core decay heat with natural circulation.  I am sure the anti-nukes will get a lot of mileage out of that.  Some US BWRs have these.

RE: hindsight- how to avoid repeat of Fukushima

With perfect hindsight...

It seems incredible that the 'spent' (a bit of a misnomer) fuel rods are removed from the highly-sealed reactor, withdrawn from the ultra-secure, ultra-strong primary containment structure, and then....they are dropped into what is basically a 3rd floor swimming pool under a tin roof.

Corrective action to better protect the spent fuel rods (and their water) when they're outside the reactor should be relatively inexpensive.

 

RE: hindsight- how to avoid repeat of Fukushima

Quote (rcchap):

I know that there are advanced digital technologies out there, but they are rarely used in the nuclear industry, and would definitely not be used for reactor control.
I found this in the internet!

RE: hindsight- how to avoid repeat of Fukushima

Link?
 

RE: hindsight- how to avoid repeat of Fukushima

Uhuh, sorry. Missed to add the link.
Google
Or Here

RE: hindsight- how to avoid repeat of Fukushima

What you have found is a simulation program.  This seems to be a simple one.  Most (if not all) US reactors will have a full scale simulator room that mimics the actual control room and is controlled by computers that are programmed to mimic plant operation.  These are used for operator training and NRC license qualification.

So, of course, digital technologies are used for simulators and plant process monitoring systems and to perform calculations.  My statement is still true.  This type of digital system would not be used to control any actual plant equipment, at least on the existing US nuclear fleet.  

The newer generation of plants will probably have more digital controls, but to what extent I do not know.

RE: hindsight- how to avoid repeat of Fukushima

Not that I trust a thing that I see or read in the media, there was a scene shown of a control room on some TV channel a day or two ago that supposedly was the Fukujima plant in happier days.  At least all the operators in the CR were all oriental.

I noticed that all or at least most all the stuff on the walls and operating consoles was analog.

Made a gauge tapper like me feel right at home.

rmw

RE: hindsight- how to avoid repeat of Fukushima

Opening the door and trying to read a 28 channel temperature recorder. I didn't think there were any left except me.

Just heard on the news that there is serious possibility of compromise of the containment vessel in Reactor #3.  Based on a previous report this could almost take out Japan as safe place to live.   

RE: hindsight- how to avoid repeat of Fukushima

rmw - I think there are quite a few "gauge tappers" on this site.

HAZOP at www.curryhydrocarbons.ca

RE: hindsight- how to avoid repeat of Fukushima

rcchap is right on with the comments....for my $0.02...the ability to have natural circulation capability is key just as it is in Naval Reactors and stick with the PWR vs BWR..and my final comment...to pay for this retrofit, utilize the money set aside for the failed Yucca repository. Looks like Code Shops will be busy doing retrofits until new plant designs incorporate and cost out all that results from the above comments. Let alone the NRC mandates.

 FAQ731-376: Eng-Tips.com Forum Policies A question properly stated is a question half solved.

RE: hindsight- how to avoid repeat of Fukushima

(OP)
coderef:
Chances are the money deposited for the Yucca repository went down the same hole as the excess SS trust funds, excess highway funds from fuel tariffs, etc, and was instead spent on a few bridges to nowhere. I doubt it is sitting in a bank under an account labeled " for Yucca mountain , or equivalent".  

RE: hindsight- how to avoid repeat of Fukushima

Dave, good point, but I don't think the utilities will just sit back and eat it without a fight. I think some have already filed suit regarding Yucca....and any recommendations resulting from what has occurred in Japan would be costly. I would think the mess of Yucca would be worthy of at least a federal loan gurantee of some type from the government. The question is, who will ask first? Will the government agree? how desperate each one is in speeding up the economic recovery.

FAQ731-376: Eng-Tips.com Forum Policies A question properly stated is a question half solved.

RE: hindsight- how to avoid repeat of Fukushima


I heard a news report that Japan delayed shipment of reprocessed fuel from France because they didn't have enough human resources to monitor the shipment.

Based on this, I'm wondering how much fuel was in the spent fuel pool and how does it compare to US Plants?

It is my understanding that most US Plants are only moving the minimum amount of fuel out of the pool and into dry cask storage to maintain TS required space off loading th fuel from the vessel.

For the U.S., I think regulations need to address the fact that the spent fuel pool was never intended to be a permanent repository.

Furthermore, all fuel that can be placed into dry cask storage should be mandated to be done immediately or hefty penalties be imposed for every day it remains in th SFP, unnecessarily.

RE: hindsight- how to avoid repeat of Fukushima

The storage issue has always been the achilles heel of the Nuclear industry and it is to me an issue that requires a technical solution.  That is what we as engineers are all about.  Maybe the current crisis will spur that effort along.

rmw

RE: hindsight- how to avoid repeat of Fukushima

There is a technical solution in place.  Put the spend fuel in dry casks, ship the dry casks to Yuca.

Problem is political.

RE: hindsight- how to avoid repeat of Fukushima

Agreed - however, I think there are still some technical challenges that have to be solved with how to ship it from "here" (wherever the stuff is)to Yucca safely.  Or should I say in a form that the public would view as "safely".

The next scenario we don't want to see is a truck or train load of dry casks scattered all over some accident sceen where a truck turns over or a train derails.

The irony is, Nuclear material is shipped all over the country every day, but it is very quietly done and as of now, nothing has happened.  But as of a few weeks ago, a Tsunami hadn't inundated a Nuclear station either.

rmw

RE: hindsight- how to avoid repeat of Fukushima

Dry cask storage is not necessarily the solution.

Current dry casks technologies are not designed for permanent storage, nor are the designed for travel.  The dry cask storage is at the plant site, so the fuel is moved only a very short distance.  Usually the trucks that do this moving go very slow, and are not designed to travel the highways.  Actually, their weight alone would preclude this.

Plants are using dry cask storage because the pools are filling up.  Without any storage locations in the pool for spent fuel, the reactor cannot refuel, and thus it could not continue to operate.  Thus plants are doing this because they have no choice.

Also, dry cask storage is usually done with the oldest fuel assemblies that put out the least amount of heat.  Since the dry casks are cooled with ambient air, recently used assemblies would probably not be stored this way, and they would remain in the pool.  The hotter assemblies are the ones that are at greater risk of melting if the SFP water was lost.

On the occasions that they do ship spent fuel, they use special transport casks.  These casks are smaller, extremely rugged, and can withstand a collision with a speeding locomotive without rupturing.

The federal government has dropped the ball.  Those in Congress who are anti-nukes have made sure that Yucca will never be used, even though billions of dollars of tax payer money had been spent on it and the government had committed to taking the spent fuel (since they actually own it).

I know that Spent Fuel Pools will get a lot of attention in the next few months ...  but first we need to understand why the Fukishima pools lost their water.  I don't think it was because of the earthquake or the tsunami.  I think it was because of the containment design of Fukushima with the pool in very close proximity to the reactor where it could be damaged by the hydrogen explosions.  If this does turn out to be the case, then plants who have their pools in a separate building won't have this problem.  This is the case for all PWRs in the US.

RE: hindsight- how to avoid repeat of Fukushima

This one is easy. Decommission all of them, world wide, yesterday.  

RE: hindsight- how to avoid repeat of Fukushima

dicer; Are you for real?

Would you like to live with rotating blackouts for the rest of your, (would-be miserable), life?

Do you prefer a CO2 laden atmosphere?  Every creek and river dammed up?  A world wide collapse that makes the last one look puny?

And all this because one plant suffered a 9.0 quake and a 10 meter tsunami in the same hour?

Everything that went wrong can be designed out, or retrofitted without any new inventions or unproven technology.

Get a grip.

Keith Cress
kcress - http://www.flaminsystems.com

RE: hindsight- how to avoid repeat of Fukushima

The technical solution is to hit the nuclear with intense gamma radiation until the elements are transformed from unstable isotopes to stable isotopes- doable with an active nuclear reactor.   

RE: hindsight- how to avoid repeat of Fukushima

Does decommissioning solve the spent fuel problem?

HAZOP at www.curryhydrocarbons.ca

RE: hindsight- how to avoid repeat of Fukushima

I believe that opinions are like elbows; everyone has a couple and that everyone is entitled to their own st***d opinion.

Unfortunately a large segment of the population of this country agrees with the statement as written by [b]dicer]/b].  Equally unfortunately, they don't have the ability to reason much further than the tip of their nose so they aren't confused with the facts like those that Keith presented.

They go into a dark room, flip the switch and the lights come on.  They haven't the foggiest notion of how that comes about.  It is kind of like the water in their fawcets, it is always there.

There are quite a number of Nuclear plants in spring outage right now and no one notices because the demand for power is not very high during spring.  Let those plants stay off line come June-July-and August and they will notice because it will be rolling blackout time.

I think the country needs a "maintenance outage" week where a whole segment of the industry - Nuclear being just one - goes off line for a week of maintenance during the same week.  I think that by the end of that week, the population as a whole would be rethinking their views on the power industry.  Especially if it is in late spring or early summer.

As it right now, go try it - go to the nearest light switch and turn it on and see if the light doesn't come on.  How neat.

rmw

RE: hindsight- how to avoid repeat of Fukushima

rmw, that's uncalled for. Nuclear power only supplies 13% of the world's electricity. Keith's predictions of eternal rolling blackouts, every creek and river dammed up, and a world wide collapse are grossly exaggerated. You do no service to your cause by labeling these things "facts," nor by insulting those you disagree with.

RE: hindsight- how to avoid repeat of Fukushima

I had a feeling this would turn into a nuclear debate.  It is natural there will be differences in opinion in all of that.

As events unfold in Japan, I suggest we as engineers should pay attention to quantitative aspects.  As bad as it sounds in the media, the amount of exposure to the general public seems to me to have been very small.   When we hear that radioactivity from Fukujima is detected in Iowa, it sounds alarming, but we have to remember what a tremendously sensitive ability to detect we have:  each decaying isotope gives off a unique signature (gamma energy), so we can tell exactly which isotopes are present. Since some of these isotopes do not occur in nature, the signal to noise ratio is essentially infinite (there is no natural "background" noise for these isotopes).  On the other hand, we still are exposed from a variety of natural sources to external and internally-ingested radioactivity which is very similar with respect to biological damage, but does not have identical detection signature.

My feeling is that (unless things turn worse), the biggest impact is that there has been a disruption and psychological burden when the Japanese are at a very vulnerable time and shouldn't have to deal with this. There are also food chain impacts which which at this point remain unknown but will be closely tracked and restricted so that the impact remains economic (not public health).    

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

RE: hindsight- how to avoid repeat of Fukushima

Trottiey,

I don't know what you think "my cause" is.  And I am not clear on how I labeled anything as a fact.

I am an adovcate of not only Nuclear Power, but some other very unpopular forms of power generation (e.g. Coal) in today's media hype driven anti any type of power generation climate.  

Moreover and more importantly, I am an advocate of the public at large becoming more aware of just where their power comes from and accepting that there are risks with all forms of power generation, and accepting the risks if they want to receive the benefits.

Dicer advocated "decommission them all - yesterday".  Whether his comment was tongue-in-cheek to make a point, or he really felt that way doesn't matter.  The truth is that a large segment of the population of this country feels just that way.

Kieth "itsmoked" used a little alegory and maybe some overstatement in his response to Dicer but that didn't give me any heartburn, because his point is valid.  I agree with him in his call for them to get a grip.

Nuclear Power generates over 20% of the power in this country, higher than the 13% world wide average you quoted, and if all of it were taken off line "yesterday", there would be rolling blackouts for several summers and maybe a few winters to come before it could be replaced with something - who knows what that might be, but it won't be wind and solar.  

There is just not enough reserve margin to instantly replace Nuclear Power and still have adequate reserve margin to operate the grid(s) in a stable fashion.  And that is a fact.  For how long it would remain so is conjecture.

I have witnessed first hand on more than a few occasions right from inside different power station operating rooms the moment when a Nuke somewhere out on their system tripped and watched them scramble to try to deal with catching the load, often unsuccessfully.  I can't picture what they would do if all the Nukes on their system tripped simultaneously.  You better believe black outs.  And that is a fact.

If Dicer is insulted by my opinion, I regret that.  That was not my intent.  But I would also recommend that he/she not come on an industry specific forum and advocate doing away with that industry if easily insulted.  You won't find me on his/her automotive fora advocating doing away with motor vehicles.  I think I can accurately guess how I would be responded to if I did.

rmw

RE: hindsight- how to avoid repeat of Fukushima

If the US nuclear industry is so keen on the safety of their reactors, will they push for the chief regulator to be someone "anti-nuclear"? Not really anti-nuclear rather not nuclear industry friendly like a police man.   

RE: hindsight- how to avoid repeat of Fukushima

All good comments.....
"Failing to plan is planning to fail." - John Wooden

"Although there is no progress without change, not all change is progress." -John Wooden

And my favorite from Warren Buffet.....Beware of geeks bearing formulas.

FAQ731-376: Eng-Tips.com Forum Policies A question properly stated is a question half solved.

RE: hindsight- how to avoid repeat of Fukushima


My point about the spent fuel was that it is safer in dry cask then in a pool with a "tin roof" over it.

The casks are inerted and welded closed. It is my understanding that the dry-cask design was based on the shipping container design done in the 1960's, which can withstand truck, train and plane crashes.

I don't think decay heat is limiting the move, but the amount of radiation when a bundle is removed from the water to be put into the dry cask.

The problem is allowing the SFP to be re-racked to allow more fuel storage and not revising TS to preclude long term storage.  Full core off-load should not be the limiting TS requirement based on space.

The Licensee has no motivation to move fuel into a safer onsite storage location. I wonder whether the utilities built a concrete pad sufficient to store all possible fuel or just enough to preclude TS shut down.

Does anyone know what the decommissioning requirements are? I hope its not just leave the fuel in the pool until congress provides a permanent storage location.

RE: hindsight- how to avoid repeat of Fukushima

(OP)
"The Licensee has no motivation to move fuel into a safer onsite storage location" + Yucca canceled + 20 yr license renewal = formula for open-ended increase in SPF inventory.

 Sounds like the foxes are guarding the chicken coop.Why is it that there is no assessment of the risk due this accumulation?  

RE: hindsight- how to avoid repeat of Fukushima

rmw,
I just wanted to say that I appreciate your post of April 3rd for its professionalism and care with facts. I'm glad we got over that bump in the conversation.

If you don't mind, I would point out that referring to "this country" is ambiguous when writing on an internet forum. From your figure of 20%, I can guess you mean the USA, but that is not representative of my country nor of several other posters on this forum.

RE: hindsight- how to avoid repeat of Fukushima


Thankyou davefitz for being someone who understands the point of my lesson learned.

How do we get these concerns to the NRC task force investigating the Fukushima event for U.S. plants?

RE: hindsight- how to avoid repeat of Fukushima

{quote]I know that Spent Fuel Pools will get a lot of attention in the next few months ...  but first we need to understand why the Fukishima pools lost their water.  I don't think it was because of the earthquake or the tsunami.  I think it was because of the containment design of Fukushima with the pool in very close proximity to the reactor where it could be damaged by the hydrogen explosions.  If this does turn out to be the case, then plants who have their pools in a separate building won't have this problem.  This is the case for all PWRs in the US. [/quote]
Reactor 4 loss its water before the explosion.  If I'm not mistaken, it was the loss of water that allowed the fuel to be exposed which caused the explosion.  That reactor was completely shut down and defueled at the time.

Where did the water go?  There are some good ideas here:
http://allthingsnuclear.org/post/3964225685/possible-source-of-leaks-at-spent-fuel-pools-at
and here
http://allthingsnuclear.org/post/4133270698/where-did-the-water-in-the-spent-fuel-pools-go

A significant problem may have been identified!

Quote:

A possible source of the leak in the Unit 4 pool may be the seals around the doors (or "gates") on one side of the spent fuel pool. These gates are shown in the diagram below. They are located between the pool and the area above the reactor vessel. They are concrete with metal liners, and are roughly 20'x 3'.

When fuel is moved between the pool and vessel, this whole region is filled with water, the gates are opened, and the fuel can be moved to or from the reactor core while remaining under water. The water not only keeps the fuel rods cool but acts as a radiation shield.

When the gates are closed, they are made watertight by an inflatable seal, similar to a bicycle innertube, that runs around the sides and bottom of the gates. Electric air pumps are used to inflate these seals and keep them inflated as air leaks out of them over time.

These pumps are powered by electricity from the power grid, and not by backup diesel power or batteries. So once the power grid in Japan was knocked out, these seals could not be inflated if they lost air over time. If these seals lost air they could lead to significant water loss from the pool, even if there were no direct physical damage to the pool from the earthquake or tsunami. This may be what happened at pool 4, and could affect the other pools as well.

We saw an example of this in the US at the Hatch nuclear plant in Georgia in December 1986. This reactor is very similar to the reactors at Fukushima. In the Hatch case, the line supplying air to the inflatable seal was accidentally closed, the seal lost pressure and created a leak, and by the time the problem was identified several hours later some 141,000 gallons of water leaked from the pool—about half the water in the pool Fortunately, the source of the problem was discovered and fixed before the water level uncovered the fuel.

An NRC document on the leak gave this description of the event:

    A valve in the single air supply line to the seals was mistakenly closed. Although water level dropped about 5 feet and low-level alarms in the spent fuel pool worked, the leak was not specifically identified for several hours because a leak detection device was valved out and none of the seals were instrumented to alarm on loss of air pressure.

The NRC document goes on to note that if the water level had gotten low enough to expose the fuel the high radiation level around the pool would have made it difficult for workers to fix the problem.

The closed air line in the Hatch case had the same result that lack of electric power the air pump inflating the seals in Japan could have.

See also this entry for the current state of gauges and controls at the stricken reactors:
http://allthingsnuclear.org/post/4136147791/how-much-does-japan-know-about-the-status-of-its

RE: hindsight- how to avoid repeat of Fukushima

Wow.. Thanks for quoting that Spartan5.

That needs some fail-safe work.

Keith Cress
kcress - http://www.flaminsystems.com

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