thanks for responding. I understand that you don't want to engage into a lengthy debate, but let me reply to your main points.
>>Also, Monju fuel is oxide fuel pellets, not metallic fuel. It is too bad that you were misinformed by experts<<
I'm glad to hear about the oxide fuel. I was making the obviously mistaken assumption that Monju was using the same fuel design as the European Fast Breeder prototypes I'm more familiar with. There metallic fuel was used because it was supposed to marginally improve the breeding rate over oxide fuel, despite the extra risk.
>>Two advantages of sodium over water as reactor heat transfer medium are the temperature and pressure of operation which are possible.<<
I am familiar with these advantages, see my comments on the thickness of coolant pipes in my message to M. Downey in this thread. The lower coolant pressure becomes a disadvantage when designers take advantage of it and use thinner pipe walls, resulting in less time to spot small cracks before they turn into leaks and making the plant more susceptible to earthquake damage.
As to the higher temperatures in the FBR heat exchanger that improve thermal efficiency, I think you've got a point there but it's a bit of a mute one, considering you would have to build 4-5 FBRs like Monju (at $6 billion apiece) to produce as much electricity as one cheaper but slightly less efficient LWR. You'll have tough time reclaiming that extra capital cost in fuel cost savings.
For the benefit of other less familiar with power plants I should also mention that it are not FBRs that have an unusually *high* efficiency but LWRs of the more common PWR (pressurized water reactor) type that have an unusually *low* one (about 33%). Coal fired power stations (40% and more) have no problems exceeding the thermodynamic efficiency of FBRs and advanced combined cycle gas fired power stations achieve as much as 70%.
>>As the availability and price of petroleum again become more favorable, we seem to drop the search for long-term energy sources. We aren't about to change, so it is not impossible that sometime after I can't possibly care we will buy nuclear power plants from the French or the Japanese.<<
I do agree it is a pity that so little money has been spent on subsidizing research into alternative energy sources that will become necessary as fossil fuels become scarce and expensive again. Unfortunately the vast sums spent on developing nuclear energy (for example, in the early 1980s the German Federal Ministry of Research spent over 90% of its energy research budget on nuclear projects) has not brought the exaggerated promises made for that technolgy in the 1950s and 60s any closer to reality, but research into renewable energy was severly starved of cash by that onesided focus on nuclear. I personally believe that the main reason so much money was spent on nuclear energy was the guilt factor from its association with the bomb. Scientists and politicians wanted to make up for the negative image of Hiroshima and mushroom clouds, which is not a very rational basis for founding ones energy policies on.
Even without billion dollar research budgets, wind energy has already become competitive with nuclear in some European countries. Denmark, without any nuclear power stations and the highest proportion of wind energy in its electricty industry also happens to have some of the lowest electricity prices in Europe. Mountainous Japan, with thousands of kilometres of windswept coastline provides excellent conditions for harnessing wind power.
Solar electricty costs have come down by more than a factor of 1000 over the last three decades and is already competitive in isolated locations where the cost of establishing a connection to the grid is a problem. Tokyo lies further south than either Madrid, Rome or Athens. The potential for using solar power is there and some people here (including my family) already use it for hot water in the summer. All it takes for solar to compete head on with fossil fuels for electricty is for solar panel prices to come down a little more.
Let me give you an example to illustrate that solar energy is actually much closer to practical use than Fast Breeder technology: Today I can buy 1 sqm (11 sqft) of high quality photovoltaic panels (monocrystalline silicon) for about $500. No doubt if I wanted millions of square metres the price would be much lower. But even at that one-off retail price I could have bought 1 sqm of panel for every third household in Japan for the price tag of Monju. In bright daylight, when airconditioners push power consumption here in Japan to the peak, these 12 m sqm would have produced a total output of about 1000 MW, about three times as much electrical power as Monju, without producing any radioactive waste, no need for reprocessing plants and no risk of nuclear disasters. Five or ten years from now the balance will look even better for solar as prices for panels fall further and further. Please also note that I have not even included the cost of the reprocessing plant necessary to process Monju's spent fuel and the cost of dismantling the plant at the end of its lifespan, both of which will add billions of dollars to the cost of nuclear energy.
Japan also has vast untapped reserves of geothermal energy (well, untapped apart from the odd onsen) and is not using any of it for power generation, while New Zealand, Iceland and Italy are all using it commercially (New Zealand happens to have industrial electricity prices four times lower than Japan with its 49 nuclear power stations). Volcanic hot water heats Icelandic greenhouses so that you can even grow bananas a few kilometres south of the polar circle. Houses in Reykjavik are heated with geysir energy and steam from geothermal sources produces electrity. Because Iceland and New Zealand are not as densely populated as Japan they have no real shortage of energy sources but some people in Iceland were discussing supplying Scotland with Icelandic power via a undersea high voltage cable.
To claim that Japan was short of domestic energy sources as the supporters of the Fast Breeder like to do is bogus. Japan is not short of energy, it is only short of imagination and initiative. I don't know how long it will take before France and Japan finally realize they bet on the wrong horse and abandon their costly nuclear programs, but when it happens they will not only find that other countries will be way ahead on solar and other technologies but also that these two countries will have to spend vast sums of money on cleaning up the radioactive mess left behind by their nuclear adventures.
>>I have a feeling that the promise of FBR to relieve the terrible anxiety the Japanese have about dependence on imported energy will keep alive the dream of making this technology work. This is a politico-national security issue for them.<<
There may be an element of 'nihonjinron' in this. In most countries the fact that all other countries had abandoned a particular policy that ones own country was still following would be a good reason to subject that policy to close scrutiny, to see if maybe the reasons that led others to abandon it might not apply here as well. In Japan however isolation is only taken as confirmation for the idea that this country is indeed different from other countries (i.e. better, in this case planning for the future).
I think the idea of "energy self-sufficiency" may be as much a generation problem as it is with the rice issue. Not only has the 60+ generation experienced a shortage of food during the war, they also experienced how their country was punished for its large scale invasion of China via an oil boycott by the Dutch and British (Dutch-Eastindia and Malaya), one of the factors that led to the Pearl Harbor attack.
The unique Japanese drive for energy selfsufficiency is quite irrational. The only major industrial power that exports more oil and gas than it imports is Britain, just because it happens to sit right next to North Sea oil. All other developed countries are virtually as dependent on oil imports as Japan is. Even the United States with their huge land mass only produce half their oil needs domestically. Germany and France have virtually no domestic oil reserves. It is not the Japanese energy supply situation that is unique, it is only how Japan chose to respond that is different from other major industrial powers.
It doesn't take much to look through the smokescreen of Japan's drive for energy self-sufficiency:
For one, there is a very practical limit to the percentage of electricty capacity that can be nuclear in any country: The output of nuclear power stations can not be as easily be varied as for other types of power stations, for technical as well as safety and economical reasons. As a result, the difference between the daily and seasonal peak and the base level nighttime bottom of power consumption will always have to come from non-nuclear stations such as coal, oil and gas. This is why even nuclear-mad France does not produce more than 70% of its electricity from nuclear. What that would mean is that even if through a veritable army of Fast Breeders like Monju Japan became completely independent of uranium imports, it could probably only provide minimum supplies of electricity in the event of a global energy import blockade!
In most industrialized countries electricity only provides about half of all energy used. Transport, domestic heating and the chemical industry are still totally dependent on fossil fuels. Without oil and gas all trucks in Japan would still come to a halt, most households still couldn't cook any meals or make hot water and practically all industry would come to a standstill because of the resulting breakdown of the transport system. A chain is no stronger than its weakest link. Energy self-sufficiency for a country as developed as Japan is virtually impossible. The only time for which it would make any sense is World War III, a scenario that Japanese politicians vow they would try to prevent with all their might.
Incidentally, Germany was subject to the same oil shortages as Japan during WW2. It resorted to making liquid fuels from coal, just like South Africa did during the Apartheid years. Nowadays Germany imports almost all its oil and the German coal industry would have virtually no chance of survival in an open market. There are plenty of low cost producers of coal from politically stable countries such as Australia and the USA. This is why Germany is gradually phasing out its costly subsidies for domestically mined coal and will become as dependent on imports as Japan is.
I think countries like North Korea are proving very clearly that you can't afford to run a self-sufficient wartime economy in peace times, which is exactly what Japan is attempting with its Fast Breeder program. Trade has made Japan wealthy and striving to achieve self-sufficiency would ruin it, as it has ruined North Korea.
I am hoping that the shock of this accident would raise enough questions in enough people here so as to start some serious debate. This subject is too important to leave it to government bureaucrats.
P.S. Please also have a look at my reply (138921) to Bob Eichelberger's message about Monju's technology in the "Monju problems" thread in the "Politics & Opinion" section where I also talk about the issue of domestic renewable energy sources in Japan. This is where I would pefer to keep the debate. BTW, are you in Japan?
>>Officials of the governmental Power Reactor and Nuclear Fuel Development Corp (PNC), which runs Monju, have said there was no radioactive harm to the environment from the accident. In March 1987, 20 tons of sodium leaked from a storage tank at France's fast-breeder, Super Phenix, the Science and Technology Agency said.<<
The leak in the storage tank in the French Fast Breeder was greater in quantity but less serious in quality. The amount of sodium leaked in the Monju accident was at least 20-30 times more *per hour* than in the Superphenix incident and it directly involved one of the coolant cycles of a reactor producing power while the Superphenics leakage only involved a secondary storage tank that was not directly related to the running of the reactor. The next largest accident in a fast breeder involving leakage from a coolant cycle released only half to one third of the amount of sodium as the Monju accident.
The fact that the sodium that leaked from Monju was not radioactive is no reason for comfort whatsoever. That comment is nothing but an excellent piece of disinformation by the PNC. Yes, unlike the sodium in the primary coolant cycle which is radioactive, the sodium in the secondary coolant cycle (where the leak occured) isn't radioactive. BUT: If leaks can occur in the secondary coolant cycle where operating temperatures are actually *lower* than in the primary cycle, what confidence can we have in the reliability of the primary cooling cycle that after all was built and designed by the same people but is subject to more stressful conditions?
It is still not clear wether the sodium leak was down to bad workmanship or to corrosion or inadequate materials or a combination thereof, but the main problem is, if it can happen in the secondary coolant cycle it is probably even more likely to happen in the primary cycle and would pose even greater dangers in that case. Cracks in metal widen due to temperature changes and corrosion is also speeded up by higher temperatures. Since coolant temperatures are higher in the primary cycle, all of these problems are actually worse there than in the secondary cycle...
P.S. See my messages in the "Monju problems" thread in section "Politics and Opinion"
>>It seems to me that your conclusion doesn't follow. If the primary cycle experiences higher temperatures, it will be designed with these higher temperatures in mind, correct? If so, then one cannot infer much about the primary cycle from problems in the secondary cycle.<<
what happened in the Monju Fast Breeder Reactor a week ago was highly unexpected. It was never supposed to happen. There is nothing inherent about the operating temperatures of either coolant cycle that should directly cause leaks. The temperature of the sodium is supposed to be in the order of 500 C = 900 F (I don't have detailed figures differentiating by location), which is well below the melting point of steel (about 1500 C or 2700 F). If a particular kind of steel was known to be affected by sodium it could not be used for either coolant cycle. From an engineering point of view there is therefore little reason to assume that the primary coolant cycle would use different materials from the secondary coolant cycle. The separation between the two cycles is only made to prevent the sodium circulating outside the reactor core containment (the secondary cycle) from becoming radioactive.
The problems affecting these pipes are of a more fundamental nature. As Bob Eichelberger who used to work with the PNC pointed out the coolant temperatures of Fast Breeders are higher than those of Light Water Reactors, allowing for better efficiency. Unfortunately it also increases thermal stress. The inside of a coolant pipe is hotter than its outside. If you remember your physics that means that the inside will try too expand further than the outside, which is not possible. It is the same effect that cracks a glass jar when you pour boiling water into it. Repeated heating and cooling of the reactor as its power output varies or as it is shut down for maintenance or refuelling and started up again will subject the pipes to thermal stress, which can cause cracks to develop in the material. These cracks will not instantly damage the pipes such that they could no longer fullfil their function, but they can grow over time. Because the primary cycle is subject to higher operating temperatures that effect will be worse there too.
It is a similar effect to the one that affects planes as they climb into the stratosphere and then return to sea level air pressures. Remember the Aloha Airlines jet that once blew a hole into its fuselage and a stewardess was blown out through the hole? They found nothing wrong with the jet, except that it had done an extraordinary number of takeoffs and landings as it was shuttling back and forth between the islands. Just as jets are not supposed to loose twelve foot diameter pieces of their aluminium skins, Fast Breeder coolant pipes are not supposed to develop coolant pipe leaks either, but how can we respond if they do?
The Monju accident probably was not from thermal stress only, as the reactor is too new for that. It must have been a combination of bad workmanship or materials, such as badly done welding that wasn't detected on an inspection, with the effects of thermal stress. As the reactor was gradually brought up to full power the walls of the pipe became subject to stronger and stronger tensions and eventually the bad spot ripped. Because they are considered particularly vulnerable spots, welding seams in LWRs are supposed to be inspected with x-rays or with ultrasonic scans. If this isn't done carefully then air bubbles or cracks are missed. If a seam contains such enclosures it out to be cut and rewelded, which is expensive and can lead to delays in the construction process. Monju already took ten years to build and cost $6 billion so maybe it became tempting to cut corners...
The problem of cracks in jet fuselages was adressed by submitting jets of a certain age to inspections as the material itself was fine when the jets were built and the problems only developed through aging. Corresponding inspections for Fast Breeder Reactors are very difficult: While the surface of a jetliner is easily accessible, the FBR cooling pipes are covered up with heating coils and insulation materials (they are actually red hot in operation). The primary coolant cycle runs through a normally nitrogen filled containment where humans could not enter without breathing apparatus and the contents of these pipes is highly radioactive.
Unfortunately if the Monju reactor runs out of control due to a major failure in its cooling system there is no emergeny cooling system to save the day. The future of Fukui prefecture vitally depends on these cooling pipes.
>>If failure of the primary cycle would be more catastrophic, then I would think that "normal engineering practice" dictates that the various tolerances be increased. I don't know if "normal engineering practice" is adequate here.<<
That depends on whether you expect the kind of problems that did occur. If something has to withstand pressure you can design it for a pressure ten times higher than expected. If something wears out you can design it for a ten times longer longer life span. The problem with the coolant leak is that it is unexpected. There is no designed-in system parameter that springs to mind that, if inadequate, would allow this sort of thing and that would be different between the two coolant circuits.
The most likely cause of the leak was bad workmanship that was not caught because of inadequate inspections. Higher tolerances in the design help very little if design standards are not met in practice. Concentric pipes as in Monju's predecessor might have helped but they were dropped for cost reasons.
>>Funny you should draw the parallel with aircraft. Nine years ago I submitted a patent application (in Japan, in Japanese) for a system to detect imminent failure in a certain class of materials. I listed as potential applications aircraft fuselages, and critical systems in nuclear power plants. (...) I didn't pursue it (..) because I realized that its implementation would involve a complete rethinking of the system design. In the case of aircraft in particular, people tend to use more silicon in the aluminum alloys to make them harder. This prolongs the service life of the material, but also makes the material that much more brittle, so that when failure occurs it occurs nearly instantaneously. Making failure prediction nearly impossible.<<
I think these two problem areas have more in common than you realize: In German nuclear power stations they found on inspecting one of the longest serving station in the country that there were far more cracks in the pipework than they had expected. They finally realized that the special kind of highly alloyed steel that they had been using for the last 15-20 years in all new stations and that had been praised as a "wonder material" was not only very firm but also extremely brittle, making it break more easily with thermal stress than conventional steel.
One particular fear from that was that if due to a cooling system failure the emergency cooling system ever had to force large amounts of cold water into the reactor core, the sudden temperature shock on the hot but brittle cooling pipes would cause them to burst, causing leaks on such a scale that the core becomes uncoolable. Obviously we don't have to worry about that problem with Monju as it doesn't even have an emergency core cooling system...