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Nuclear power and climate change – what now?

I’m currently on a 3-week trip to North America, and will be returning to Australia in mid-June. At the end of my travels I’ll be attending an energy futures conference in Waterloo, Canada (and will write more about that in an upcoming blog). But at present, I’m in Davis, California, and have been visiting Tom Blees. So it’s appropriate that I present a guest post from Tom, which was originally published in Meteorological Technology International magazine in May 2011. You can download the printable PDF version here.

Guest Post by Tom Blees. Tom an advanced energy systems consultant from Davis, California, and author of Prescription for the Planet – The Painless Remedy for Our Energy & Environmental Crises. Tom is also the president of the Science Council for Global Initiatives , an international think tank of distinguished scientists dedicated to creating an environmentally sound energy-rich future for the entire human race. Previous guest posts on BNC include: Unnatural GasDanish fairy tales – what can we learn? and Germany – crunched by the numbers.

The nuclear power plant debacle in Japan in the wake of the recent earthquake and tsunami has complicated what already was a contentious question: Should we look to nuclear power as a major component in solving the climate change problem? The situation at Fukushima Daiichi in Japan is getting more manageable by the day, though the ultimate repair and cleanup will be a long-term project. The 24-hour news cycle has feasted on the public’s dread of radiation, relegating the deaths of tens of thousands in the earthquake and tsunami to almost a footnote on American cable news shows. Anti-nuclear crusaders have been trotted out with little regard for their qualifications, some resurrecting long-debunked tales of deaths and injuries at Three Mile Island (where nobody was even hurt, much less killed).

The predicted nuclear renaissance may founder temporarily in some countries because of these events, but the lessons that will be learned from Japan’s accident won’t stop the growth of nuclear power in the long run. It will only make future plants safer. Despite the dire warnings of doomsayers, nuclear power plants being built today are far safer than those at Fukushima, and the Generation IV reactors to come will be even better. The aged power plants at Fukushima that would likely have survived the tsunami intact if not for the woefully misjudged placement of their backup power supplies had been running as long as forty years, and were designed half a century ago.

A Toshiba engineer describes features of the "4S" (super-safe, small and simple) nuclear battery - a sodium-cooled fast reactor with metal fuel, based on the IFR concept

Nuclear Technology Moves On

How’s that laptop working that your daddy bought you back in 1960? One might well pose that question to those who now advocate the wholesale abandonment of nuclear power based on the accident in Japan, for technology—nuclear and otherwise—has not been standing still. The fact is that our energy options are limited, and those that can provide baseload electricity (24/7 on demand) without carbon emissions are more limited still. Except for geothermal power opportunities accessible in just a few places in the world, hydroelectric power and nuclear power are just about the only two choices. Hydro, of course, while not as geographically limited as geothermal, nevertheless is circumscribed by both topography and politics. (On that latter point, it’s ironic that the Sierra Club used to be pro-nuclear until the early Seventies, seeing nuclear power as the way to obviate the building of dams. Since their complete reversal of that position they have been anti-nuclear crusaders—who still hate dams.)

Whatever one believes about the causes of climate change, there is no denying that glaciers around the world are receding at an alarming rate. Billions of people depend on such glaciers for their water supplies. We have already seen cases of civil strife and even warfare caused or exacerbated by competition over water supplies. Yet these are trifling spats when one considers that the approaching demographic avalanche will require us to supply about three billion more people with all the water they need within just four decades.

There is no avoiding the fact that the water for all these people—and even more, if the glaciers continue to recede, as expected—will have to come from the ocean. That means a deployment of desalination facilities on an almost unimaginable scale. Not only will it take staggering amounts of energy just to desalinate such a quantity, but moving the water to where it is needed will be an additional energy burden of prodigious proportions. Given the formidable energy requirements for these water demands alone—not to mention the energy demands of the developing countries for all their other needs—any illusions about wind turbines and solar panels being able to supply all the energy humanity requires should be put to rest.

Fortunately for all of us, the nuclear power technologies that can safely provide all the carbon-free energy that humanity will desire in the years to come have already been invented. We are already seeing the first of the so-called Generation III+ light-water reactors (LWRs) being built in China, the Westinghouse/Toshiba AP-1000. GE/Hitachi’s III+ design, the ESBWR (Economic Simplified Boiling Water Reactor), is slated to be certified for construction this fall by the U.S. Nuclear Regulatory Commission (NRC). Both reactors utilize advanced passive safety features that rely on the laws of physics rather than operator or automated intervention to deal with potential accident scenarios.

Cut-away diagram of the 1,550 MWe GE Economic and Simplified Boiling Water Reactor (ESBWR)

These reactors are also designed to weather electrical shutdowns like the one that bedeviled the Japanese plants and caused such a cascade of problems. With natural circulation only, the plants will remain in a safe condition even in an accident where no humans are on-site for three days. Probabilistic risk assessment studies for the ESBWR indicate that we could expect a core meltdown once every 29,000,000 years. But say we built 1000 of them (twice the total electrical generating capacity of the USA, and the amount of new nuclear the Chinese plan to build by 2050). That would mean you could expect a core meltdown once every 29,000 years, still virtually fail-safe. If we build ten times that many, 10,000 reactors, that would mean an expected core melt just once every 2,900 years, and as we can see from the experiences of Japan and Three Mile Island, you’d still probably have zero casualties, once every three millennia. Granting that even the most rigorous risk assessment studies might perhaps miss something, the safety margin is still so great that it would be the height of folly to abandon nuclear power when systems such as this are available to us. What would we use instead that can fill the bill?

Nuclear Waste and Material

But detractors will nevertheless complain that reactors like the ESBWR still produce long-lived radioactive waste products that will have to be safely watched over for what is, for all intents and purposes, forever (from a human standpoint). Another objection frequently raised is the risk of nuclear proliferation, the fear that nuclear material will be misdirected from power plants and made into nuclear weapons. Fuel supply is also an issue when the prospect of a burgeoning nuclear renaissance is considered, with demand for uranium expected to skyrocket. And over all this looms the capital cost of building nuclear power plants, which many consider a deal-breaker even if all the other issues could be resolved.

Back in the early Eighties a group of talented nuclear physicists and engineers realized that if there was to be any reasonable expectation of widespread public acceptance of nuclear power, all these problems would have to be solved. So they set out to solve them. Under the leadership of Dr. Charles Till at Argonne National Laboratory’s western branch in the state of Idaho, a virtual army of nuclear professionals designed an energy system that many expect will soon power the planet, if only we can muster the political will to deploy it. Their test reactor operated virtually flawlessly for thirty years as they identified and solved one potential obstacle after another, proceeding methodically until they were ready to demonstrate the commercial-scale viability of their revolutionary fuel recycling system that would complete what had been a spectacularly successful project. What they had accomplished during those years was, without exaggeration, probably the most important energy system ever invented, one that promises virtually unlimited safe, clean energy for the entire planet. Unfortunately, an almost unbelievable shortsightedness on the part of politicians in Washington D.C. pulled the plug on the project just as it reached its final stage in 1994, and the promise of the Integral Fast Reactor (IFR) languished virtually unnoticed for the next fifteen years.

Figure 1: A simplified version of an IFR reactor. Illustration courtesy of Andrew Arthur

The Integral Fast Reactor

But the IFR is such a grand invention that it couldn’t stay buried any longer, and people around the world are now clamoring for it to be deployed. The looming threat of climate change has prompted many to take a fresh look at nuclear power. Some have considered the problem of so-called “nuclear waste” (not waste at all, as we shall soon see) an acceptable price to pay in order to curtail greenhouse gas emissions. In the wake of the Japan accident, safety will also be prominent in the debate. The IFR, though, is so impressive in its qualifications that even previously hard-core anti-nuclear activists have touted it as the ultimate answer. And the fact that over 300 reactor-years of experience have been accumulated with fast reactors around the world means that such technology is no pipe dream, but a mature technology ripe for commercial deployment.

The term Integral Fast Reactor denotes two distinct parts: A sodium-cooled fast neutron fission reactor and a recycling facility to process the spent fuel. A single recycling facility would be co-located with a cluster of reactors. Figure 1 shows a simplified version of such a reactor. It consists of a stainless steel tub of sodium, a metal that liquifies at about the boiling point of water. Sodium is used both as a completely non-corrosive coolant and, in a separate non-radioactive loop, as the heat transfer agent to transport the heat to a steam generator in a separate structure (thus avoiding any possible sodium-water interaction in the reactor structure).

The system is unpressurized, and the pumps are electromagnetic pumps with no moving parts. In the event of a loss of flow, natural convection and the large amount of sodium will be sufficient to dissipate the heat from the fission products in the core, unlike the situation in the Japanese reactors at Fukushima, which required constant cooling even though the reactors had been shut off.

The commercial-scale iteration of the IFR’s reactor component is called the PRISM (or its slightly larger successor, the S-PRISM, though for the sake of brevity I’ll hereafter call it simply the PRISM, which stands for Power Reactor Innovative Small Module). It was designed by a consortium of American companies in conjunction with Argonne Lab, and is now being further refined by GE/Hitachi Nuclear. From a safety standpoint it is unparalleled. If the risk assessment studies for the ESBWR mentioned above sound impressive, those of the IFR are even better.

In my book Prescription for the Planet, I did a thought experiment based on the risk assessment studies for the PRISM that have already gotten a preliminary nod from the NRC. The likelihood of a core meltdown was so improbable that I figured out how often we could expect one if thousands of PRISMs were providing all the energy (not just electricity) that humanity will require a few decades hence (according to most estimates). Remember, the occurrence of one meltdown would require dividing the total number of reactors into the probability for a single reactor. Even so, the probable core meltdown frequency came to once every 435,000 years! Even if that risk assessment was exaggerated by ten thousand times, it would still mean we could expect a meltdown about once every half-century for all the energy humanity needs.

Reactors and Natural Disasters

The crisis at Fukushima’s power plant has stoked fears that existing nuclear sites may be incapable of withstanding quakes in excess of their design specifications. Whereas many lightwater reactors are designed to withstand G forces of about 0.3, the PRISM is rated at 1.0. This G rating is different than a Richter scale rating because the Richter scale represents the total energy released in an earthquake, which is dependent on many factors (duration, depth, etc.). When designing a structure or piece of equipment to withstand earthquakes, the degree of ground acceleration is what matters. If one were to stand directly on a geological fault line during the most severe earthquake imaginable, the G forces caused by ground acceleration would almost certainly not exceed 1.0. (The maximum ground motion at the Fukushima complex during the earthquake measuring 9.0 on the Richter scale was 0.56 G) So the PRISM reactor, designed for that level of motion, could safely be built in any seismically active area. Of course it goes without saying that no power plant should be built at a low elevation in a zone that is vulnerable to tsunamis, or for that matter on a flood plain. But with the PRISM, seismic shocks are not an issue.

As for proliferation risk, it should be pointed out that the risk of proliferation from any sort of power reactor has been substantially mischaracterized and generally overblown. The reason is that the isotopic composition of the uranium and plutonium in power reactors is lousy for making weapons. Any country that wishes to pursue a weapons program covertly is far better served by using a small research reactor operated in a specific manner to produce high-grade weapons material, and even then it requires a quite complex reprocessing system to separate it.

That being said, the IFR system uses a unique metal fuel that can not only be easily and cheaply recycled on-site and then fabricated into new fuel elements, but at no stage of the fuel cycle is any sort of weapons-grade material isolated. All the isotopes of uranium and plutonium are not only left mixed with their various cousins, but there is always at least a bit of highly radioactive fission product elements, making the fuel impossible to handle except by remote systems.

Figure 2: The fission products will only be radioactive beyond the level of natural ore for a few hundred years.

The buildup of such fission products in the fuel, though, is what eventually necessitates pulling fuel elements out of the reactor for recycling. In the pyroprocessing system—a type of electrorefining common in the metallurgical industry but unique to the IFR among reactor systems—the majority of the fission products are isolated. The rest of the fuel is reincorporated into new fuel elements. The fission products, representing only a small percentage of the fuel, are entombed in borosilicate glass that can’t leach any of them into the environment for thousands of years. Yet the fission products will only be radioactive beyond the level of natural ore for a few hundred years (see Figure 2). Thus the so-called “million year waste problem” is neatly solved.

As for the question of uranium supply, that issue is moot once we begin to build IFRs. First we’ll use up all the spent fuel that’s been generated over the years by LWRs, plus all the weapons-grade uranium and plutonium from decommissioned nuclear weapons. It’s all perfect for fuel in IFRs. But then when that’s all gone we can fuel them with depleted uranium. There is already so much of it out of the ground from years of nuclear power use that even if we were to supply all the energy humanity is likely to need from just IFRs alone, we’ve got enough fuel already at hand for nearly a thousand years. As efficient as LWRs are in squeezing a huge amount of energy out of a small amount of fuel, fast reactors like the PRISM are about 150 times more efficient. In fact, all the energy a profligate American would be likely to use in a lifetime could be extracted from a piece of depleted uranium the size of half a ping-pong ball.

Finally we come to the clincher: the cost. For some reason it supposedly is going to cost anywhere from two to five times as much to build a nuclear power plant in the USA than exactly the same design being built in the Far East. This comparison applies not just to countries with low labor costs but to Japan too, where labor costs are high and nearly all the materials are imported. It’s an American societal and political problem, not an inherent flaw of nuclear power. Utility companies fear that a group of protesters with signs and lawyers might shut down construction midway through a multi-billion-dollar project, or prevent a built reactor from operating. So they prudently try to build that uncertainty into their cost estimates (with maybe a little padding to boot).

A golf ball of uranium would provide more than enough energy for your entire lifetime, including electricity for homes, vehicles and mobile devices, synthetic fuels for vehicles (including tractors to produce your food and jet fuel for your flights). Your legacy? A soda can of fission product was, that would be less radioactive than natural uranium ore in 300 years.

The new reactor designs, both the Gen III+ designs mentioned earlier and the PRISM, are designed to be mass-produced in modules, then assembled at the power plant site. The PRISM has the added advantage of operating at atmospheric pressure, so no pressure vessel or high-pressure pumps are needed. The passive safety principles mean that multiple redundancy is unnecessary, allowing such reactors to have far fewer pumps, valves, controls, and other components than their older Gen II predecessors. Based on both industry estimates and actual experience of building these reactors since the Nineties, there is every reason to believe that the price can be kept well below $2,000/kW, though the Chinese plan to produce them for half that price once their mass production supply lines are in place.

There is virtually no doubt that with these new nuclear technologies available, the shift to predominantly nuclear power is virtually inevitable in the long term. Over sixty new plants are under construction around the world with many more to come, even if some nations are temporarily deterred by political and social pressures. If we’re serious about solving the climate change problem before it’s too late, we’ll have to get serious about the only zero-emission baseload power source that can easily supply all the energy the world needs.

We shouldn’t consider this a Faustian bargain. These new designs—particularly the IFR—are clean, safe, economical, and able to convert waste products that we desperately want to get rid of into abundant energy for the entire planet. Anyone serious about protecting the environment can safely embrace them with enthusiasm.

By Barry Brook

Barry Brook is an ARC Laureate Fellow and Chair of Environmental Sustainability at the University of Tasmania. He researches global change, ecology and energy.

129 replies on “Nuclear power and climate change – what now?”

@Environmentalist, the only thing that is going to be added of any real consequence to the European grid in the next ten years is more Russian gas. Ever last bit of wind and solar added will only be there to provide a green veil to hid it.

Why you and other supporters of wind and solar steadfastly refuse to see that this is what is happening, is beyond me. You are being used by FF interests as auxiliaries in their fight. The funny thing is that even if wind and solar could assume 100% of the load, those same interests wouldn’t let it. They are not supporting renewables because they are good citizens – they are doing it because it’s good for their bottom line.

For Christ’s sake, wake up and smell the coffee.

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IT IS NECESSARY TO ANSWER STUPID QUESTIONS because if we don’t, the wrong answer may be assumed by someone who knows nothing about it but who is very good at pushing people’s emotional buttons. Likewise, it is necessary to tell an innumerate humanitologist that she is wrong and how and that she should get a degree in physics or nuclear engineering before commenting on that subject. “You are being too emotional” is not an adequate answer. We need to really explain the truth.

Just complying with making nuclear power safer has never worked. We must explain that coal, wind, solar etc are far more deadly and that not having electricity is the most dangerous thing of all. Otherwise, you are on an infinite treadmill of making nuclear safer and gaining nothing. We need to get corporate money involved in advertising the fact that nuclear is the safest source of electricity. This includes teaching everybody about natural background radiation. Teaching everybody about natural background radiation does work.

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I think the best way to promote nuclear is to let the German experiment unfold but have France and Czech republic boycott sale of electricity to Germany. Give it 5 years of green utopia (deleted ioffensive remark)

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(Rick’s offensive remark deleted)

Back on topic, the Germans are indeed looking down the barrel of a F-up. They might learn the hard way the importance of reliability.

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Right again DV8.The kindest thing to be said about Germany on the energy score is that they are somewhat confused. The only way they’ll replace the 23.8% lost from nuclear phase out will be for an increase in fossil fuel use [gas]. That will be marginally better than coal but still not emissions-free. I thought that was the whole purpose [emissions-free] of our future power generation. Oh yeah, I forgot the renewables. There’s no hope of an adequate 24/7 supply with them, not ever, ever. Got that.

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@Podargus, on 31 May 2011 at 7:00 AM

Unfortunately, “we” are not the ones who need to be convinced about the impossibility of relying on renewables for base load power. It is the general public and their governments. A constant complaint from the pro nuclear lobby is that excess regulation against nuclear and subsidies in favour of renewables are tilting the playing field. Obviously the renewables supporters have succeeded in getting the ear of governments to have achieved this.
The reasoning against using renewables might be “simple” but, by itself, it is obviously not enough to convince even a country like Germany with a long and impressive record of technological innovation and expertise. I think that what is at work is a mixture of entrenched core belief in the evils of nuclear and an optimism generated by the growth of “people power” successes which give rise to the attitude that somehow someone will come up with a new development to solve this problem. The renewables supporters are very fond of the argument that their costs are reducing and assert that they will solve the zcalability and cost problems if only more and more can be invested in R&D.

But, as Podargus has said, we don’t have the time to wait for a new silver bullet to emerge. Otherwise, we will be stuck with the renewables outcome which David Mackay rails against in “Sustainable Energy Without the Hot Air” —If everyone does a little, we’ll achieve only a little”

Somehow, people have to be convinced to discard the superficially attractive renewables and go back to that which they have previously set their minds and hearts against. Governments will quickly respond if public opinion moves in that direction.

Achieving such a reversal will require a concrete demonstration of the superiority of one system other the other, theories or modelling won’t be enough.
I expect that it won’t take till 2022 for the result to be clear cut. Germany will have to develop a clear detailed plan now to achieve the phase -out so the consequences will start to hit home as its citizens are told what they will be giving up to achieve 10 % efficiency savings, where the new pylons are to go, how much their power bills are to rise relative to France’s etc. Already, some commentators on this site are saying 5 or 6 years should be enough.

That may still be longer than what we would like, but I think it is shorter than what could have been achieved without this development.

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Mullos well said. The only other way public opinion will change and thus government policy, is a global climate event that is dramatic. However this may be 20 years or more away and will be too late to stop warming of 2 to 4 degrees C by the end of the century.

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I’m looking forward to the post on sodium coolant.

I do believe that the debate of lead vs sodium is by no means closed. According to a report* which studies both coolants, lead-cooled fast reactors are safer, but sodium-cooled fast reactors are minimally more efficient at burning actinides and a more mature technology.
From an operational security and public acceptance viewpoint I believe that if fast reactors are commercialized in a Western country they will be lead-cooled. Even if they don’t hurt anyone, sodium fires do disrupt the operation of the power plant.

*http://www.sciencedirect.com/science/article/pii/S0029549306003347

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Germany’s Nuclear Ban: The Global Effect

“Germany’s plan to shut all of its nuclear power plants within the next 11 years will send waves — not ripples — through the energy industry and the offices of policymakers throughout the world. In short, Germany’s nuclear ban is a global game-changer.”

“In the short term, Germany, most likely will import nuclear power from France and the Czech Republic. This will place pressure on the existing nuclear power supply and drive up costs as a result. .”

“Germany’s nuclear ban will add about 25 million metric tons of CO2 emissions a year. “

“Today, renewable energy provides about 13 percent of Germany’s power. By 2020, it wants renewable sources to provide 35 percent of its electricity. To be clear, it will take a massive effort to reach that goal.”

“If it fails, governments that have been slow to embrace renewable energy will use Germany’s problems as a reason to backpedal from the source altogether.”

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On the issue of sodium coolant, my understanding of it is that in most breeder reactors there are two coolant loops.

The primary loop that cools the reactor directly, then there is the secondary loop that takes the heat out of the primary containment to the steam generators and that’s where the problem is.

If the steam generators develop a leak and catch fire you have to shut everything down for repairs and even though there’s no danger to the reactor itself this still ends up probably being a significant economic cost.

Leaving aside the notion that it very well might be possible to develop a sturdy and reliable sodium-to-water heat exchanger with a little engineering and elbow grease the thought that always occurs to me is:

If we’re that worried about it, why don’t we try to find something that doesn’t react with sodium or water and use that as the coolant in the secondary loop? That seems a bit more reasonable than throwing out decades of work and research on an otherwise promising reactor.

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Nick this has been my primary concern about sodium reactors all along. Sodium is an otherwise fine material except for that darn water sodium interface. (deleted personal opinion presented as fact and unsubstantiated by refs.)

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Gene:

Well, yes.

Current sodium-to-water heat exchangers do tend to leak now and then which causes problems.

I was agreeing with that.

For various reasons, some of which could be called pseudo-philosophical and are outside of the scope of this thread, I want to keep breeding ratios as high as possible. As far as I know this means metal fuel and sodium coolant in the reactor itself, so that’s the baseline I’m working from.

Which means either building super durable heat exchangers or eliminating the water-sodium interface.

The former may very well be possible, perhaps using diffusion bonded heat exchangers rather than tube-in-shell designs to eliminate the welds that are what tend to leak? There’s one company that makes such heat exchangers and indeed lists metal cooled reactors as a compatible application: http://www.heatric.com/index.html

Or the other option is make sure sodium and water never meet. I’m told lead-bismuth eutectic doesn’t react with water and has a reasonable melting point, if it doesn’t react with sodium either then perhaps that would be worth a try? Also, for all of the talk I’ve seen about using gas turbines for future reactors might it be possible to have a sodium-to-gas heat exchanger and just remove water from the mix altogether?

I guess all I’m trying to say is that sodium + water = fire shouldn’t automatically consign sodium fast reactors to the scrap heap.

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Use of another material for the intermediate loop such as nitrogen or CO2 might be feasible. I often wonder why we need the intermediate loop. Isn’t there a safe design that could use just sodium and some other material other than steam for the turbine with just a single loop through the turbine? CO2 turbines are of interest because of their high power with respect to their size. Just because we have used steam for so many years does not mean we have to use steam forever. I’m obviously way over my head on this topic. I wish I also had a degree in nuclear engineering….

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You all do understand that at the sort of temperatures that are involved here, lead-bismuth erupting into water in a steam generator would be just as explosive as sodium. In other words, at 600-700C the amount of energy added by the chemical reaction would make little difference to the size of the explosion.

As well unlike sodium in the liquid state, lead-bismuth eutectic is highly corrosive to most metals making a rupture more, not less likely.

You might be interested to know that several non-nuclear power stations have been built that use mercury as a working fluid.

http://www.aqpl43.dsl.pipex.com/MUSEUM/POWER/mercury/mercury.htm

including the Clementine nuclear reactor

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@DV82XL

from the referenced linked above :
heat generated from the reaction of Na with water :
140000 Joule
specific heat of one mole of Na @300C : 23*1.2= 27.6 J/K
140000/27.6 = 5072 K temperature difference !

From an instantaneous standpoint , chemical energy is not negligible.

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It is not necessary to use sodium to water steam generators. There can be an intermediate loop fluid that transfers heat from the sodium to the water in the steam generator. A fluid that can’t be used in the primary loop because its not sufficiently stable against radiation but is compatible with both sodium and water. Certain fluorocarbons are a good example. A noble gas is also an option, helium for example. The latter being completely noble as an advantage, and high pressure, low volumetric heat capacity as a disadvantage (but this is not such a big deal for a steam generator that is non-nuclear and already high pressure on the steam side).

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Of course, we’d be having four loops, which costs a bit and loses temperature in each loop.

First loop: sodium (activated, very radioactive)
Second loop: sodium (barely radioactive at all)
Third loop: helium (possibly final loop if helium gas Brayton is available) or fluorocarbon
Fourth loop: steam (if helium gas Brayton is unavailable).

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I’m from germany and antinuclear forces are so strong here, right now you can’t win an election while supporting or even just keeping nuclear.
So, no matter if it’s a good idea or not, our government has to ban nuclear. It’s even a race who can demand the earliest ban. Many consider keeping it run till 2022 as a pro-nuclear position that plays on time and forgetting fukushima.
Also many people here think there is a big bad “atomlobby” financing all the arguments pro nuclear, so you don’t have to listen to them.

Here are some examples what the german climate&energy discussions look like (it’s in german):
http://www.heise.de/tp/inhalt/energie/default.html

It’s a shame.

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@charles monneron -Consider the physics of a rupture of the sort we are contemplating. As the molten metal at such a high temperature hits the water, the water flashes to steam and the area in contact with the sodium is highly reduced, so most of the initial release of energy will be from this process, not the chemical reaction.

Since this will now be a liquid-gas interface, both the heat vaporizing the water and the evolving hydrogen from the chemical reaction will form a shield that will slow down the chemical reaction as the species won’t interact very well.

This is the same effects that has a lump of Na skidder around on the surface of a bowl of water rather than react all at once.

I am not saying a rupture would be without hazards, but it would not be much different if any molten metal hits hot water under these conditions.

The free enthalpy calculations don’t tell the whole story.

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Cyril you have me thinking about another possible advantage of the intermediate loop. If the intermediate loop were either a gas or compressed liquid, might it not be possible to raise the temperature on the steam generator side, thus increasing the turbine efficiency? For example you could have a lower temperature sodium IFR reactor and then the intermediate loop would be inert, transfer the energy, and at the same time raist the temperature on the steam cycle side to super critical? I need Rod Adams to comment on this if you are monitoring Rod….

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A gas compressor can increase gas temperature (and hence steam temperature on the other side of the steam generator) but it requires work to operate. You don’t get the work back because the work to be done is in the next loop (steam). You only get the heat. So unless I’m missing something this does not improve on the final work done. But if you have a turboexpander on the cold end it could be the most efficient means of moving the intermediate gas around. This isn’t an energy positive cycle though, and a fluid loop (using pumps) would always consume less work…

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@DV82XL

I agree with you that the dynamic of the process is complex. Nevertheless, if the “steam envelope” tends to isolate the sodium from the water, it also lowers the heat transfer. At some point the sodium may boil and the sodium vapor interact with the whole volume of the steam or the steam/water interface. Ruling out an explosive dynamic is not obvious for me. It may also be dependent of the quantity and shape of the sodium sample.

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My personal feeling is Merkel should have said ‘I support nuclear’ and been prepared to be defeated at the polls. She surely has the educational background to know, which I presume is why she initially supported nuclear.
The world is going to find out soon enough that nuclear is the only option. The only way it won’t be the only option is if a miracle occurs and, say, the polywell works, or some UFO lands on the WHL and gives us the secret to zero point energy.
My increasing feeling is that we are screwed. If even someone like Merkel, who really doesn’t need to win another election to afford to buy bread, can lie to us all about what it really takes to have a sustainable future, then I’d say we are in real trouble. The rot did not stop with Schroeder.
How I wish I was French.

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@charles monneron, – The fact is that there have been sodium leaks, both intentional and accidental into steam generators that show this is not as big an issue as it might seem to be on paper.

The Japanese Fast Breeder Reactor MONJU had an event in December 8, 1995 as detailed here:

http://www.sozogaku.com/fkd/en/cfen/CB1011005.html

which was reasonably uneventful.

Nevertheless the physics of a breach in a sodium cooling loop is not simple, but it has been studied enough to understand the risks, and those risks can be controlled.

Click to access MQP_Studies_of_Metal_Fires.pdf

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