March 14, 2011
New Designs Would Avoid Japan Reactor Failures?

In Technology Review Kevin Bullis highlights nuclear reactor design improvements that would cut the risk of cooling system failures.

The latest nuclear reactor designs could help avoid the overheating and explosions that have occurred at the Fukushima Daiichi nuclear plant in Japan following the powerful earthquake and tsunami that struck on Friday. Newer reactor designs propose the use of passive cooling systems that would not fail after a power outage, as happened in Japan, as well as other novel approaches to managing reactor heat.

Passive systems are key in my view. Human operators make mistakes and active systems can get damaged when you most need them. According to a Bloomberg report the Japanese reactors had back-up generators designed to withstand 6.3 meter waves but the plant was hit by 7 meter waves. So for want of an additional 0.7 meters of protection the reactors have undergone partial meltdowns. Ouch.

On the bright side, big nuclear reactor failures are like big passenger aircraft accidents: They get heavily picked over and analyzed by large numbers of skilled engineers. We learn from failure. Unfortunately, the failure of nuclear plants in Japan is starting to look more like Chernobyl and less like Three Mile Island in terms of the scale of the disaster.

An LA Times story points to mistakes made by Japanese engineers that have exacerbated the problems.

Engineers had begun using fire hoses to pump seawater into the reactor — the third reactor at the Fukushima No. 1 complex to receive the last-ditch treatment — after the plant's emergency cooling system failed. Company officials said workers were not paying sufficient attention to the process, however, and let the pump run out of fuel, allowing the fuel rods to become partially exposed to the air.

Once the pump was restarted and water flow was restored, another worker inadvertently closed a valve that was designed to vent steam from the containment vessel. As pressure built up inside the vessel, the pumps could no longer force water into it and the fuel rods were once more exposed.

One can guess these reported mistakes are not the only mistakes that have been made so far. Under intense pressure in a crisis situation people will make mistakes. Emergency handling can not depend near perfect decision making.

The Diablo Canyon nuclear power plant at Avila Beach California is designed to handle only a 7.5 earthquake. San Onofre is designed for a 7.0 quake and has a 25 foot high wall to protect from tsunami. A fault 5 miles offshore could let loose some day. The absence of a subduction zone off of SoCal is supposed to put us at much lower risk of a tsunami. Also, SoCal Edison claims San Onofre has more safety layers than the older reactors in Japan. Plus, it has an emergency cooling source that is gravity driven.

But what about the soundness of the probabilities of geological risks and systems reliability that are fed into models for choosing nuclear reactor sites and designs? As Joel Achenbach wrote in a WaPo piece a few days ago, Japanese scientists were expecting the Big One to occur south of Tokyo, not north of it. Japan's preparations were oriented in the wrong direction. The coast off of Sendai hadn't had a huge quake for at least 1,000 years. What other geological surprises lay in store?

If an earthquake followed by a large tsunami is "beyond what anyone could expect" then how can the nuclear power industry claim it can choose sites and designs that will avoid events like the ones happening at the Fukushima nuclear power site?

Richard Meserve, a physicist and former NRC chairman from 1999 to 2003, said the Japanese reactors experienced a "one-two punch of events beyond what anyone could expect or what was conceived."

What is so unlikely about a big earthquake followed by a big tsunami along a Pacific Rim subduction zone?

Update: Diablo Canyon is 85 feet above the ocean. Plus, it has a gravity fed back-up water reserve. So it looks like it is at much lower risk of a tsunami.

What the Japanese ought to do for their remaining undamaged nukes: Build back-up generator buildings that can survive a tsunami flooding over them. Be able to ride out the worst that nature can throw at you can keep on going. Earthen berms and lots of concrete would do the trick. Another idea: Build back-up generators that are well inland and run underground cables to the nukes near the coast.

Any other spectators want to tell the nuclear plant engineers how to make their nukes safe from tsunamis?

Share |      Randall Parker, 2011 March 14 10:59 PM  Dangers Complex Engineering


Comments
Red said at March 15, 2011 1:55 AM:

All the issues with these systems have to do with active nature of cooling the reactor down. Thorium molten salt reactors and pebble bed reactors both stop the reactions and cool themselves off without outside intervention once a certain temperature threshold is exceed. Both systems would be an excellent choice to replace today system in high earthquake/tsunami zones.

Chris T said at March 15, 2011 9:20 AM:

Also, what is so unlikely about a big earthquake followed by a big tsunami along a Pacific Rim subduction zone?

What was unlikely was the 4th most powerful earthquake on record on a fault the geological record didn't show generating quakes that powerful. You can attempt to engineer for every risk, but cannot completely eliminate it. At some point, you just have to accept a level of risk.

Sadly, this one went against us.

BioBob said at March 15, 2011 9:57 AM:

Sorry, but not only has TEPCO misled and lied front, right and center from the beginning of this crisis (as well as for the 40 years prior to it) but there is still critical information they are not releasing.

For instance, were you all aware that while each of these reactors do have a containment structure around the core, they also have a spent fuel rod storage pool in the reactor "attic" now fully exposed to the environment in the case of the 3 reactors which have had hydrogen explosions. The fire at the 4th reactor in trouble was in one of these pools that spent fuel rods was stored in. We don't know how much of an issue this is or how many pools are in use or how much spent fuel is stored in each. Failure to maintain water levels in these pools will cause melt downs of the "dirtiest" nuclear fuel possible without any containment whatever.

This is now well beyond corporate damage control. While contamination is not likely to reach Chernobyl levels simply because of the lack of graphite fuel, global contamination is inevitable at least at lower levels. This is now ALL our problem.

AMac said at March 15, 2011 1:27 PM:

Randall,

Nice essay. I stumbled across this 25-page PDF by a TEPCO engineer, showing a careful study of the risks to the two Fukashima complexes, in the wake of the 2010 Chilean earthquake. It is unhappily titled, "Tsunami Assessment for Nuclear Power Plants in Japan." Summary: "We assessed and confirmed the safety of the nuclear power plants based on the JSCE method which was published in 2002."

This disaster looks like one more example of the truism that complex systems have complex failure modes. It wasn't one single thing that led to this situation, but a series of things piling on, one atop the other.

Beyond running out of diesel and turning a valve to the wrong position, I've read of other things (not sure that they are true, though). One is that this design has the electrical interconnect for supplying external generator power to the emergency cooling pumps located in the reactor building's basement. Flooded, in this case.

Today, the NYT quoted some US military as saying they'd driven some fire trucks to the Daiichi complex to help with pumping, but were told that their help wasn't needed. So they returned to their base. I don't know what day this was, but surely it would have been prudent to have kept the trucks on site as spares, if nothing else.

Apparently the Japanese government didn't take an active role in crisis management of the plants until Monday, deferring instead to TEPCO.

.

A glance at the San Onofre station on Google Images makes it seem very unlikely that it is as well-prepared for earthquake/tsunami as were the Fukashima plants. Though perhaps deeper water offshore makes a > 25-foot tsunami less likely there (power company claims it has a 25 foot seawall).

.

Chris T,

You don't seem to distinguish between risks that we don't know well enough to quantify accurately, and risks that we know are unlikely to happen. Was "a very big subduction-zone earthquake near Japan with an associated very big tsunami" an event that could not have been foreseen by the people who sited and designed these plants?

Tom Register said at March 15, 2011 5:42 PM:

So where does it end? Design for a Magnitude 7 quake, 8?, 9? 10? A 7 meter wall of water? 17 meter? 170 meter?

Lets just give up a sit around the campfire chipping flint

Chris T said at March 15, 2011 7:19 PM:

Was "a very big subduction-zone earthquake near Japan with an associated very big tsunami" an event that could not have been foreseen by the people who sited and designed these plants?

It was foreseen, planned, and built for. Unfortunately, it turned out not to be enough. The same concept goes with designing a car. If we all drove tanks around at 30 miles per hour, we'd be very safe. However, no one can afford or wants to do that. So auto engineers make them as safe and survivable as possible, but still have to accept that it won't always be enough.

Steve Sailer said at March 15, 2011 8:28 PM:

San Onofre sits on top of an 85 foot high bluff according to the LA Times article. But what is the bluff made out of? Granite? Sandstone? There can be a big difference.

Southern California is somewhat protected from tidal waves originating in the Northern Pacific ring of fire by Point Concepcion. Tidal waves from the tropical Pacific would have to go farther to reach SoCal. Two tsunamis were recorded in the 19th Century in Southern California and none in the 20th. In contrast, Crescent City, CA, near the Oregon border has been hit twice in recent years.

The height of a tsunami depends upon the shoreline. Survivors of fishing villages in narrow inlets in Japan reported a 60 foot high wave. So, Santa Monica, say, might survive pretty well but the Santa Monica bluffs could channel water toward the lowlands of Marina Del Rey.

Fat Man said at March 15, 2011 9:34 PM:

The historic records show the strongest California Quake as a 7.9 at Fort Tejon (the pass between LA and the Central Valley) in 1857. The only 9 is a 1700 quake off Washington and Oregon, that is mostly known by historic records of the tsunami in Japan. The big fault system -- the San Andreas -- runs inland.

http://earthquake.usgs.gov/earthquakes/states/historical.php

Randall Parker said at March 15, 2011 10:58 PM:

Tom Register,

Worst case? Design cooling systems that can sustain a big tsunami washing over them. This seems doable. Just got to make buildings have a low profile and enough concrete and steel to stand up to the weight of the passing wave.

Chris T,

They did not plan for a large tsunami. If they had then their back-ups wouldn't have gotten thrashed by the passing wave.

The more I think about it the more I think that the key is to design for a wave passing over. Assume you can't stop the wave. Okay, given that assumption how to build your structures so they survive it? I can see a few strategies:

- Build the back-up generators underground and waterproof with a strong ceiling that can stand up the passing wave.

- Build above ground with a long slope of concrete leading up to the back-up generator building. The building should be able to have the wave pass over it.

- Build some back-up generators inland and run buried cables to the nuke plants.

James Bowery said at March 16, 2011 12:24 AM:

Red, it might seem like satire to state it, but Hollywood could probably solve the nuclear safety problem by making as many movies about Hyman G. Rickover as they do about the Holocaust, portraying Rickover the way they portray Nazis. The cult of Rickover still has a death grip on the Federal agencies responsible for nuclear power and the word "thorium" is right up their with "Hail Satan!

Sergey Kurdakov said at March 16, 2011 7:42 AM:

Randall - in economic simplified boiling water reactor http://en.wikipedia.org/wiki/Economic_Simplified_Boiling_Water_Reactor
no need for any pumps at all

wGraves said at March 16, 2011 10:57 AM:

They could easily have backed up an ocean-going vessel, nuclear or conventional, and used it's generating capacity to run their pumps. A carrier generates enough power to light up an entire city. I believe some of our carriers have dual plants? Why didn't they do something like that? Probably, it wasn't in the policy and procedure manual.

Nico said at March 16, 2011 11:01 AM:

Faraway generators and underground cables -> bad idea: earthquakes can sever those! (Even if you have pipes and cables in them with lots of slack, an earthquake could shear off the cables.)

Tynan Sylvester said at March 16, 2011 11:02 AM:

Here's an idea. Build coastal nuclear stations with the reactor underwater. If something goes really wrong, you can just open the roof and flood the entire vessel with seawater. It destroys the reactor, but it saves everyone's life. Nuclear submarines have had this sort of functionality for years.

Even better, in case of radiation leak, the poisons go into the water instead of the air. While this is still horrible, I'd rather the fish get radiation sickness than me. They can withstand it better anyways.

Pat Moffitt said at March 16, 2011 11:06 AM:

Wondering if your home had been washed out to sea or if you family was still alive would play no small role "influencing decision making".

Dana H. said at March 16, 2011 11:09 AM:

> They did not plan for a large tsunami. If they had then their back-ups wouldn't have gotten thrashed by the passing wave.

This is a non-sequitur, unless by "plan for a large tsunami" you mean "plan for an arbitrarily large tsunami". They did indeed plan for a large tsunami (6.3m definitely counts as "large"), just not one as large as the one they got hit with.

M. Simon said at March 16, 2011 11:10 AM:

the Japanese reactors had back-up generators designed to withstand 6.3 meter waves but the plant was hit by 7 meter waves.

Some one cut corners. A 10% over design accident should not cause failure.

tmitsss said at March 16, 2011 11:10 AM:

Perhaps you could build a repository in a desert somewhere to store spent fuel rods?

Nico said at March 16, 2011 11:12 AM:

The problem with nuiclear power plants is that the radioactive ashes of the fuel will produce about 6% of the plant's output when the chain reaction of the fuel itself is shut off. The good news is that the ashes have fairly short half-lives, so the emergency ends soon enough, but the bad news is that 6% is enough to cause a meltdown, which is why cooling is always needed for a while after a reactor is disabled.

Some ideas: a) build earthquake-safe platforms on which to put backup generators, b) keep backup generators on trucks and barges inland, so they can be brought in to a flooded plant after the fact, c) build huge water tanks to provide gravity-fed cooling (but w/o circulation this means allowing radioactive steam to vent, still, better than melting down!), d) provide better venting of hydrogen and other gasses (better release radiation than allow vessel containment to be destroyed in chemical explosions). OK, (b) is not great, but with luck enough to avoid meltdown; do it in addition to (a), as a redundance measure.

Possibly better ideas: build traveling wave reactors, thorium reactors, ... Also, it might be possible to make the heat exchangers such that when exposed to air they can provide cooling if the only the ashes are producing heat (think of CPU heat sinks) -- if at all feasible then this might be the best solution of all, though it'd probably require massive re-fitting, thus it's probably a non-starter even if it were feasible to build such a thing.

Mitch Rapp said at March 16, 2011 11:16 AM:

Experts brought us global warming
Experts brought us Obama
Experts brought us solar power at 4 x the price
Experts brought us Ethanol at 3 x the price

Experts brought us our current education

So what do these experts say?

Alan S. Blue said at March 16, 2011 11:16 AM:

Put reactors on barges. Build artificial (substantial reinforced concrete ) lakes as needed.

A barge on a lake is fundamentally far more earthquake-proof than you'll ever manage on land. Should be fine right up to an earthquake so large it could be called "Opening a Hellmouth". Or "Damn, you're too close to Yellowstone."

Making it tsunami-proof is tougher, but the crucial issue is the difference between "swiftly rising water" and "actual tsunami". The -actual- tsunami needs deflection, sea-walls, distance or hills. But if you're on a barge, you've already fundamentally solved the crisis of "swiftly rising water". Well-sunk piering/anchoring would be key, but not an amazing design challenge.

The standard "outer loop" massive cooling towers of iconic in American plants wouldn't need to be on the barge - you're looking for just the core, containment, inner cooling loop, (which should be sufficient for complete shutdown from full-operation cooling.) and diesel generators/batteries for extended outages.

In response to the "What are you smoking?!?" responses:
1) Compare the costs of a full-up supercarrier to those of a nuclear power plant.
2) The Army Core of Engineers studied doing this in the 60s. Basically for nuclear-powered logistics/hospital ships. http://www.wmsym.org/archives/2002/Proceedings/44/168.pdf (An article reviewing the state of the 'nuclear barge Sturgis' 50 years after the fact.)

3) Site analysis becomes -dramatically- simplified.
4) Plant design can become much more modularized.

M. Simon said at March 16, 2011 11:18 AM:

They could easily have backed up an ocean-going vessel, nuclear or conventional, and used it's generating capacity to run their pumps. A carrier generates enough power to light up an entire city. I believe some of our carriers have dual plants? Why didn't they do something like that? Probably, it wasn't in the policy and procedure manual.

Cross connecting the electrical systems is difficult without a pier to tie up to.

Chad said at March 16, 2011 11:24 AM:

"But what is the bluff made out of? Granite? Sandstone? There can be a big difference."

No, in the case of a tsunami neither would fail in anyway to question their durability.

From a geology perspective neither Diablo Canyon nor San Onofre is anywhere near a location that would see more than a 7.0-7.4 range earthquake (The Inglewood Fault near San Onofre would be the source for that upper value). No fault anywhere in California south of Mendocino is capable of causing a thrusting to generate a tsunami even approaching what Japan suffered. To imply otherwise is to base nothing on real geology.

For example, mentioning the San Andreas is meaningless in comparison to Tohoku. The San Andreas is a right-lateral transform fault...its motions do not create the sea-floor movement needed for a tsunami. So mentioning what the fault can do with just a Richter/Mercalli number is meaningless if the type of fault is omitted.

Finally the submarine topography off southern California insulates the greater LA area from significant tsunamis as their waves will feel the submarine slopes and discharge their energy tens of miles at sea.

So, frankly, the "they designed for it, but it was worse" hysteria is wearing thin. Too many armchair folks are comparing the apple of the Tohoku disaster with the mongoose of American powerplants and geology.

M. Simon said at March 16, 2011 11:30 AM:

The magnitude of quake you design for depends on the estimated cost of the accident. Do you just lose the plant? Or can there be expensive collateral damage?

Big Bob said at March 16, 2011 11:30 AM:

Or better yet, tmitsss, why not wind powered generators, say, uh... off the coast of Cape Cod to replace the dirty power sources such as coal and nukes. What tree-hugging environmentalist could possibly oppose that solution? Or maybe miles and miles of solar panels in some remote desert location. Could anyone object to that?

Coal and nukes, folks. Two fuel sources that put electric power at our finger tips at reasonable cost. Plus, coal is plentiful, the supply of nuke power is infinite and surely we've smart people who can solve the problems associated with each. I mean, come on, we're the nation that put men on the moon, dammit. Developing disaster-proof nuclear power and reasonably clean coal really shouldn't be that difficult for us.

diane wilson said at March 16, 2011 11:31 AM:

Building any sort of backup or recovery facility underground in a tsunami zone seems unwise. Water will seek the lowest level. Any failure in waterproofing will result in a failure of the entire facility. Ventilation for an underground and waterproof facility would be problematic at best.

Underground power lines also seems problematic in an earthquake zone. Above-ground transmission lines could survive ground shearing that would rip undergound lines apart. Redundant transmission lines using both approaches would probably be a better idea.

Designing for a 9.0 quake does not seem unreasonable to me. We know (Alaska, 1964) that such quakes can occur on the eastern side of the Pacific. In any case, over-engineering is never a bad idea when the cost of failure is catastrophic.

Steve said at March 16, 2011 11:32 AM:

"What the Japanese ought to do for their remaining undamaged nukes: Build back-up generator buildings that can survive a tsunami flooding over them. Be able to ride out the worst that nature can throw at you can keep on going."


So they should build 2000-foot+ tall berms, and protect nuclear reactors and associated facilities from asteroid strikes?

I mean, Mother Nature has thrown both of those things at us.

M. Simon said at March 16, 2011 11:35 AM:

Developing disaster-proof nuclear power and reasonably clean coal really shouldn't be that difficult for us.

How much do you want to spend?

Astro said at March 16, 2011 11:39 AM:

Build a huge lead containment box well below the reactor. If an accident occurs, the rods drop into the lead box, with the rods surrounded by lead and spaced far enough apart to prevent any chain reaction. See sketch in the link below.

Steve said at March 16, 2011 11:43 AM:

Why cant backup pumps and power be put on trucks or ships, and transported to site after disaster?
How about upgrading all these old unsafe plant designs with Generation III+ designs?

Jay, beltway said at March 16, 2011 12:27 PM:

A safety system that automatically shuts down all the reactors instantly in event of an earthquake is only a good idea at first glance. A massive event that triggers the safety shutdown is likely to damage the backup power as well, and possibly all useful offsite power. And that is what happened.

My take is the safety system should leave 1 reactor running long enough to bring the other reactors down to a safe temp in a quick but controlled manner, and then shut down the ‘backup’ reactor. My guess is that a well built reactor is much more resilient that diesel generators and their fuel tanks. The best thing would be to have the ‘backup’ reactor on higher ground, and built with a thicker containment vessel, perhaps mounted on shocks to avoid quake damage.

Perhaps large nuclear power plants should include a smaller modular reactor buried underground to run the pumps and control systems for the big reactors. Or mini reactors could be built onto long haul trucks parked in a safe location to provide emergency power where needed (not just for power plants). With these for backup, older plants that depend on power supply for safety could keep running while we build newer versions with passive cooling.

Kent said at March 16, 2011 12:50 PM:

What about using Thorium rather than Uranium? This is a link I found on Instapundit:

http://www.popularmechanics.com/science/energy/next-generation/the-truth-about-thorium-and-nuclear-power?click=pp

LouisWheeler said at March 16, 2011 1:58 PM:

With all the recrimination going on, there are things to remember: life will always surprise us, our plans are never good enough. The point is that when they were built, these reactors were state of the art, but that was back in the 1970s. They should have been replaced long ago. But, the reason they weren’t is common to bureaucratic industries. It has been hard to get newer design approved, even though those would have prevented a meltdown. Neither Pebble Bed nor Liquid Fluoride Thorium Reactors would have been harmed by the Tsunami even if they wound up under water.

Mistakes happen, so we have to keep pushing for greater safety. Perhaps now, the current version 1 reactors through out the world will be phased out, especially in high risk zones like the pacific rim.

inspectorudy said at March 16, 2011 3:10 PM:

I have a couple of questions that may be silly but I haven't seen any mention of them. one, why do they build more than one reactor in any one place? I am aware of the money saving aspect but when you stop and think about it anytime you have a big problem with one you essentially wipe out all of the others just from the safety aspect alone and of the physical/mechanical threats as well.
Two, why aren't the control rods in the cores gravity operated if power fails? In other words why aren't the rods held up electricaly and if power fails then they would scram the core? Along with this same question is why isn't there a huge water reservoir requirement on site that would be gravity fed for emergency back up cooling?

DexLane said at March 16, 2011 3:17 PM:

Why not just build a containment structure strong enough to contain a maximum meltdown? I mean, a melted set of fuel rods contains a finite amount of heat energy, no? Just construct the containment to safely contain that much energy * 2.

Jethro said at March 16, 2011 3:23 PM:

Has anyone ever considered powering some of the backups with thermocouples? As the plant heats up, turn it into an oversized RTG.

M. Simon said at March 16, 2011 3:25 PM:

My take is the safety system should leave 1 reactor running long enough to bring the other reactors down to a safe temp in a quick but controlled manner

Which takes from a week to two weeks depending. Which is why there is a backup DG.

And to the lead box guy - please spend a year or two studying reactor design before you let your imagination run free.

M. Simon said at March 16, 2011 3:27 PM:

Has anyone ever considered powering some of the backups with thermocouples? As the plant heats up, turn it into an oversized RTG.

The power required is in the megawatt range. RTGs? Kilowatts at best.

ez said at March 16, 2011 3:47 PM:

"The more I think about it the more I think that the key is to design for a wave passing over"

Randall, I think you are correct but don't forget any Deisel generator must have an oxygen source as well as fuel. Also it would be dificult to hemertically seal anything much less a building that must hold up against a tsunami and earth quake. I can't figure out why they didn't bring in portable generators such as the ones sold by Caterpillar. These can be quite powerful. Maybe they really need an enourmous power source for backup and can't use portables?

Bart said at March 16, 2011 4:16 PM:

Let's be sure some of you get the big picture: Saying "oh, nobody could have foreseen this" or "it would have cost too much" is not going to cut the mustard. If you are interested in seeing a viable nuclear industry, you had better stop the whinging and start coming up with solutions.

The possibility of a tsunami knocking out all the backup power means that there was a single point failure mechanism in this design, and the built-in redundancy was an illusion. In my line of work, this would be considered an epic failure, and probably spell the end of the company.

There is no room for excuses. The consequences have been too severe.

Tom Register said at March 16, 2011 5:01 PM:

See this is why I think that the solution is for all of us to take off our clothes, build a campfire and sit around and chip flint. That way none of these problems would occur. We would all die before we were 35 and the carbon footprint would be reduced significantly.

Although I have to thank you Randall for providing thought provoking answers to the questions in my orginal comment. It seems like for the relatively small costs of doing a few multiples of the things people suggested:

Build the back-up generators underground / Build above ground with a long slope of concrete leading up to the back-up generator building / Build some back-up generators inland and run buried cables to the nuke plants

the problem could have been averted.

Since we won't do those things and most of our fellow humans have NO CONCEPT of what is going on I say, back to the Late Pleistocene!!!!

T.V. Smith said at March 16, 2011 6:17 PM:

A 9.0 earthquake centered in Tokyo would have brought down hundreds of skyscrapers, killing tens of thousands of people (dead right now, not "maybe of excess cancer in 30 years").
Should we stop building skyscrapers?

PlanetaryGear said at March 16, 2011 7:00 PM:

The solution is to approve the building of more smaller plants of more modern designs. For goodness sake we had a thorium reactor running back at Shippingport more than 50 years ago. The chinese have a pebble bed reactor that they will happily dial up to full power and then shut off the cooling to and let you sit there and sweat while they smile because it can't hurt itself. The scarriest thing is not that 40 year old reactors are still in use, they can be improved from the lessons learned here, but that we are considering building NEW 40 year old reactors. The reason for this is regulatory. The entire cost of the NRC to learn about your design must be paid by the company wanting a license to build one. Even just small changes to a well established 40 year old design can cost half a billion or more. Bringing a new design to market is beyond the coffers of any company. Bringing a smaller design to market, say a 500 MW thorium battery, would mean that for a 600 million dollar piece of gear there would be a 1.5 billion or so charge to approve it. Nobody can do that. If you want safer, smaller, new plants in the US the regulatory environment has to change to make it possible. If that means that the government has to pay for the salaries of the people at the NRC while they learn about it then so be it. That would be far better, in my view, than just giving the money to companies directly. Pay the NRC and guarentee the loans for development of the 3 or 4 best designs. Give me 5 500MW plants built around a city rather than a single 2gw station outside it. And then you can cycle the maintenance of them too rather than once a year have to find 2GW of coal plants somewhere you can buy your power from.

Randall Parker said at March 16, 2011 10:17 PM:

Regards using an aircraft carrier as a power source: Takes too long to set up. You can't count on the aircraft carrier being around when the tsunami hits.

The ship approach could be done at lower cost with a much smaller and cheaper diesel-powered ship.

Randall Parker said at March 16, 2011 11:24 PM:

Regards thorium and other alternative reactor designs: They show great promise. But they are not ready yet.

Many step-wise refinements have been made in existing conventional reactors. The new designs ready for construction today have many fewer valves and switches and more passive systems that are much less prone to failure.

Al Reasin said at March 17, 2011 4:16 AM:

I have held a senior reactor operator's license and started up BWRs, but that was some decades ago so the memory may be a bit clouded.

BWRs provide steam directly to the turbine from the reactor, so unlike PWR's, which indirectly provide steam to the turbine from a steam generator inside of the secondary containment, the BWR pressure vessel (reactor) is "open" to areas outside of the secondary containment. Steam valves are installed in the line but the steam lines effectively become part of the core containment.

It appears that the emergency generator fuel supply storage tanks did not survive the tsunami so the generators ran out of fuel. thus the safety systems failed to operate from loss of power. Reportedly there is a crack in a fuel pool storage tank, but I wonder if the gate seals failed or depressurized.

PlanetaryGear said at March 17, 2011 9:53 AM:

Agree that there are no available "ready" thorium designs to just go ahead and manufacture. One might argue that with a regulatory environment that keeps you from ever dreaming you might be allowed to operate such a device that the research money to develop the device you can never sell might be a bit constrained... Solve that problem and I can't see very many more years passing without the work being completed enough to develop an actual approvable device.

Chris T said at March 17, 2011 12:11 PM:

There is plenty to be learned from the disaster. What I had a problem with is criticizing the designers for making decisions that probably seemed reasonable at the time. We now know they weren't, but they did not have the benefit of hindsight as we do now. If problems were pointed out then or in the intervening period then it's a different story, but for now it would seem best to study the disaster and learn from it. Criticizing people for what seemed like good assumptions about risk when they made them is not really productive.

Everything carries a risk. We can mitigate it and learn from mistakes, but it can never be completely eliminated. The only way to progress is to accept that.

Randall Parker said at March 17, 2011 7:21 PM:

ez,

My other line of thinking: The nuclear power industry should have a lot of highly mobile equipment that can be transported to a disaster site within hours. So, for example, they should have lots of

- portable generators.
- portable towers for stringing electric cables across a devastated landscape.
- Heavily lead-shielded vehicles.

I've got some other related ideas. I'm going to write it up into a post.

Engineer-Poet said at March 18, 2011 4:56 AM:

A BWR generates steam, so one potential way to address the afterheat cooling issue is to have the reactor power its own cooling system.  I'd have a small steam turbine coupled to a generator set up to recharge the backup batteries.  It wouldn't have to be particularly optimized or efficient, just powerful enough to keep up with the water requirements and preferably able to operate with a fairly wide range of input conditions (e.g. 225-285°C saturated steam).  The operators would only have to hold the temperature reasonably constant, throttling or pulsing the pumps and turbine to keep heat withdrawal balanced with heat production and maintain battery SOC.

The reactor coolant pumping systems aren't the end of the story; a tsunami picks up a lot of debris and it seems likely that condenser cooling water supplies could be choked or blocked.  But as long as there's replacement water for the reactor loop, venting a bit of steam is preferable to uncovering fuel.

I doubt that shielded vehicles would be much good.  A half-inch of steel will attenuate gammas and block almost everything else except neutrons, so your run-of-the-mill APC is nearly proof against radiation from outside.  What you have to guard against is contamination being carried or blown into the vehicle.  This means a filtered, positive-pressure ventilation system and ways to either decontaminate personnel or keep them clean in the first place.  (I've seen such ventilation systems, they're not overly large or complex.  Decontamination facilities are another matter.)

Engineer-Poet said at March 18, 2011 4:59 AM:

Of course, a conversion to MSRs using open-cycle gas turbines for power conversion would eliminate the cooling water issue and allow the reactors to be sited away from shorelines.  Passive cooling of the dump tanks takes care of that issue; when the first P-waves hit, drain the sucker and worry about something else.

PlanetaryGear said at March 18, 2011 6:46 AM:

Engineer-Poet, while I can't find any confirmation of it, I believe that they did use their own steam driven turbine pump in the 8 hours or so after the tsunami took out the backup generators. The batteries they have are for running the valves and other equipment not for actually running the pumps. So for 8 hours the batteries lasted and they were able to keep cooling, but they were unable to get any real power returned before the batteries were used up. So they CAN use their own steam to pump cooling water, but only as long as they have battery power for control systems.

BioBob said at March 18, 2011 8:30 AM:

All these pie in the sky ideas !

The first thing nuke designers should do is honestly determine if their reactor will generate more electricity than it consumes in the construction & operating process. Many of our current reactors take between 10 and 15 years to generate enough power to pay back their construction consumption. Factor in mitigating the costs of retiring these units including spent fuel and it is at least questionable if they generate much more energy than they consume in their 30-40 year lifetime and millennial footprint.

@ DexLane who said "Why not just build a containment structure strong enough to contain a maximum meltdown"

Answer: what are you going to make it out of exactly since it needs to be a unibody (seamless) tub design of considerable size, say over 20 meters square? cast tungsten perhaps? how much will that cost ? will it withstand pressure from a hydrogen/other generated gases explosion as well as max temp ?

It just is not likely to be economically nor energetically feasible.

AMac said at March 18, 2011 11:06 AM:

I'm puzzled about the catastrophic nature of failure of the plant. Reports say the tsunami was "7 meters", while it was designed to withstand a tsunami of "6.3 meters". A plain reading has the tsunami being 70 cm higher than was anticipated.

Given the scope of the destruction at the plant, it seems unlikely to me that the outcome would have been all that different, if the tsunami had been 70 cm lower than it actually was. If so, then either the plant as built didn't meet the claimed criteria, or my "plain reading" is wrong. (For example, perhaps "6.3 meters" refers to the height of the crest of a wave that quickly recedes, compared to a 7-meter rise in sea level for a sustained time.)

I left a comment on this point left at the useful site MITNSE.

The slides placed online by Prof. Benjamin Monreal of UCSB provide useful background on the basic physics and health physics issues of the accident. How Bad is the Reactor Meltdown in Japan?, from March 11th.

PlanetaryGear said at March 18, 2011 12:24 PM:

The severity of this accident is entirely due to the failed protections on their backup generator fuel tanks which washed away an hour after the accident. After that they may have been more failures and failures of policy and communication that failed to get more backup generators or some source of power to them within the 8 hours they could run on batteries after that point. So for 9 hours after the earthquake there was little or no problem beyond their ability to fully recover from. Those 9 hours were horrible for everyone else in Japan though, and somehow they could not get more generators to the plants at any reasonable time. That failure in communications or whatever that they were unable to do that is what led to everything else. The plants nor the fuel ponds nor anything else was damaged beyond the ability to safely shutdown until the end of that 9 hour period when no help and no power was forthcoming. What about us? Did we have ships in the area yet? Could the US Ronald Regan have put a couple of big generators on a boat and tied down just off shore and run them an extension cord? If someone somewhere had understood, or been made to understand what was coming could they have gotten them some over land? Something failed in that time frame that could have saved us all this conversation.

Anonymous said at November 16, 2011 3:27 PM:

I agree that you cannot predict every natural disaster however with the nuclear power plants in the U.S. getting older now it would be wise to look at situations that we have now seen occur such as a larger earth quake at the Diable Nuclear Power plant than a 6.5. Although we may not have a Tsunami what would happen if an 8.0 or 8.5 occurs near Diable Canyon. Would there be adequate surface protection for the rods? I doubt it. http://buildsitepro.com/home.asp

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