Why Japan has no CANDU's

OVERKILL

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Shannow's thread had me wondering why there are CANDU's all over Asia except in Japan. A quick search yielded this (very long) article: No CANDU - Why Japan has no Canadian reactors A few excerpts:
Quote:
n March 14, 2011, three days after a 16 metre tsunami knocked out the cooling systems of four of six reactors at the Fukushima Daiichi nuclear power plant, the Washington Post’s Slate website carried a column by Anne Applebaum in which the Pulitzer Prize–winning author gave voice to a widely shared sense of disbelief: “If the Japanese can’t build a completely safe nuclear reactor, who can?” One is tempted to write, “Canadians could have, had they been given the chance.” After all, Japanese nuclear engineers engaged in extensive studies of Canadian deuterium (heavy water) technology throughout the 1970s. In August 1979, however, Japanese bureaucrats decided against constructing CANDUs, making Japan the only country in Asia generating electricity with nuclear power not to have at least one CANDU or CANDU-derived reactor. (Korea has four, China two, Pakistan one; 14 of India’s 16 power plants are CANDU-derived.) At the time Japanese bureaucrats said no to CANDU, Japan’s U.S.-designed light water reactors of the type then already in operation at Fukushima were down for maintenance or refuelling for as long as six months a year. The extremely low efficiency rates of Japanese LWRs were in marked contrast to the 80 percent and higher operating levels that would be achieved within a very few years by CANDUs in neighbouring Korea. In fact, it would take decades for LWRs anywhere to reach near 90 percent operating efficiency. Japanese LWRs on average still operate at lower levels. Although one cannot speculate with total confidence how a CANDU would have behaved when jolted by a magnitude 9.0 earthquake followed by the onslaught of successive tsunamis, one can safely say that by adopting the far more efficient CANDUs, Japanese utilities could have avoided building more than 50 reactors in order to supply Japanese consumers with a mere 29 percent of their electricity needs. So why did Japanese decision makers opt for inefficient LWRs? To answer that question, one has to forget for a moment that the world’s fastest computer today is made in Japan. Japanese nuclear energy policy is everything that the country’s efficient export industries are not: it is a field where scientists and politicians distrust each other, where decisions on reactor type have been determined by political ambition and diplomatic necessity, where bureaucrats place a higher priority on turf wars than on rational decisions, where monopolies are shielded from responsibility for bad risks and where safety concerns are addressed by public relations departments. The origins of the Fukushima reactors—and the disaster they have caused—can be traced to the Cold War, when the dream of prosperity through the magic of the atom came to be utilized by the United States as a diplomatic tool against the Soviet Union. The first hint Japanese leaders had that they might be permitted to share in the benefits of nuclear power came on December 8, 1953, when President Dwight Eisenhower delivered his Atoms for Peace speech at the United Nations. Eisenhower promised that the atom would “provide abundant electrical energy in the power-starved areas of the world.”
*snip*
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Perhaps no single leader exercised more influence on Japanese nuclear energy policy than Matsutaro Shoriki, president and owner of the Yomiuri newspaper and its broadcasting affiliate, Nippon Television. A former Class A war crimes suspect, who came to enjoy close relations with the CIA, Shoriki would arrange to have himself appointed the first head of Japan’s Atomic Energy Agency. Already in his seventies, Shoriki was a man in a hurry. For Shoriki, nuclear power plants meant cheap electricity, which could be translated into popular support as well as financial backing from utilities and power generation equipment manufacturers. But in spite of all the above seeming advantages, the introduction of nuclear power to Japan would forever be seen in Cold War terms, actively promoted by a pro-American right wing and equally energetically opposed by the left.
*snip*
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Shoriki’s haste, his alienation of experts and his bombastic personality brought about a temporary rift with the United States on nuclear technology, resulting in a single, one-time importing of a non-U.S. reactor, a gas-cooled, graphite-moderated Magnox from Britain. Lax attitudes toward nuclear safety in Japan can be traced directly to the Magnox deal, signed in haste after the rift between Shoriki and the CIA. Graphite-moderated reactors, such as the Magnox, similar although not identical to the Soviet reactors of the type used at Chernobyl, were notoriously unstable. Britain had just experienced radiation leakage from a Magnox and therefore informed Shoriki that it would not take responsibility for any accidents. Not only would this not deter Shoriki from arranging for the importing of a Magnox, but the contract would also introduce to Japan the “no liability” clause in purchases of plants from the United States. The GE-designed power plants at Fukushima Daiichi Power Station conformed to this pattern. One can only wonder if the Fukushima reactors would have been plagued by so many design flaws had responsibility for failures been more clearly defined from the start. Although safety equipment did succeed in shutting off the reactor as soon as the quake struck on March 11, emergency diesel generators that should have kept coolants circulating to handle residual heat could not be made to work. Placed in the basements of relatively weak turbine buildings, situated on the seaward sides of reactors, the generators were immediately flooded by the tsunami. But even if they could have been coaxed into life, diesel fuel would not have been available since the fuel tanks—also constructed on the seaward side of the reactors—had already been swept away by the waves.
*snip*
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To be fair, the choices Japanese decision makers had in nuclear technology have been far narrower than in the case of Canada. In the field of nuclear energy, Canada has enjoyed tremendous advantages over Japan and continues to do so. Canada benefitted technologically from the U.S.-led World War Two weapons program but was far enough away from day-to-day military concerns at Los Alamos that Canadian scientists could look ahead to the peaceful applications of nuclear energy well before Eisenhower’s UN speech. Already in 1945, C.D. Howe, speaking to provincial premiers, would interpret the significance of the nuclear explosions in Hiroshima and Nagasaki in terms of what he called “the practical use” of the atom in the near future. As a result, after World War Two, political leaders in Canada could steer tax dollars toward the building of research and demonstration reactors where Canadian scientists could work toward goals they shared with their country’s leaders, all at a time when politicians and scientists in Japan were not talking to each other. Japanese choices in nuclear technology were also constrained in other ways. While there was much support within Japan’s Ministry of International Trade and Industry to import CANDUs, it is doubtful that MITI could ever have arranged for a significant shift away from heavy Japanese reliance on U.S.-built LWRs. CANDU’s biggest drawback was that it was not American. By the early 1970s when MITI approached Atomic Energy of Canada to begin discussions that might have resulted in the purchase of CANDUs, the burgeoning Japanese trade surplus was already triggering resentment in the United States. The trade surplus would grow rapidly, necessitating importing big-ticket items from the United States.
*snip*
Quote:
In the end, according to both Japanese and Canadian sources close to the negotiations, the CANDU fell victim to a bureaucratic turf war between MITI and the Science and Technology Agency that had taken over responsibility for the Atomic Energy Commission. In 1977, when MITI announced that the Electric Power Development Corporation, a MITI affiliate, would introduce the CANDU to Japan, STA officials were miffed and proceeded to oppose all future attempts to do so. Finally, bureaucratic inertia also played a role. According to a former bureaucrat close to Canada-Japan negotiations, a major source of resistance against the CANDU seems to have come from the nuclear power industry and the utilities, where senior executives responsible for total reliance on licensed production of U.S.-designed LWRs were still in positions of influence. As the former bureaucrat explained, “the last thing these people wanted was to see the introduction of simpler, more efficient CANDUs.”
Quote:
“The CANDU is not prone to meltdowns,” said Atsushi Kasai, former laboratory chief of the Japan Atomic Energy Agency. As to why Japanese utilities did not buy any CANDUs, Kasai added, “We scientists were never consulted on reactor types. Such decisions were always made elsewhere.”
I would say that it boils down to greed, which is the same reason none of the later recommended safety updates proposed during audits were done at Fukushima (like the relocation of the generators and their fuel tanks, the increase in the size of the sea wall...etc). Hopefully TEPCO and the Japanese power industry as a whole have learned from the situation at Fukushima, since, as noted in Shannow's thread, there are a lot of reactors coming online and I am betting many of them are similar in design.
 
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I just finished a very good read called 'Atomic Accidents' by James Mahaffey. I strongly recommend it. He spends a lot of time on the really sad and horrific "criticality accidents" that happened during the early years of handling isotopes, but then he does get on to the powerplant incidents (TMI, Fukushima, Chernobyl, as well as accidents at R&D reactors). Spoiler: more people died in criticality accidents in lab rooms or processing tank rooms than ever died in reactor accidents. He makes a very good point about the world pretty much locking into 3 reactor designs for large-scale power generation: 1) Westinghouse (PWR) and GE (BWR) light-water thermal neutron reactors 2) CANDU "heavy" water fast-neutron reactors 3) Soviet graphite-moderated/water-cooled reactors All three have some pretty serious disadvantages, but one they all share is "positive void coefficient," where an increase in vapor in the core accelerates the reaction. Type #3 has a whole lot more disadvantages on top of that, like oh... flammable moderator, control reversal in some designs (where inserting the control rods briefly accelerates the reaction), etc. The way the world has chosen to build powerplants also has the inherent problem of decay heat, which is exactly what caused all the trouble at Three Mile Island and at Fukushima (well, that plus operators overriding safeties- the operators at Fukushima disabled unit #1's completely passive shutdown cooling system before the backup batteries died, and then were unable to turn it back on!). Its a matter of scale. A PWR in a Navy submarine can be cooled completely passively once shut down, but scale that same design up 10-fold, and you have to have huge systems just to cool the core for a few days after a shutdown. So how about we make powerplants with 10 or even 50 small reactors paralleled? Because bigger = better. Because regulations. Permitting 10 reactors was once 10x more work than one giant one, but maybe the time has come to re-examine that. He also makes a strong case for breaking the paradigm and putting time and effort into new reactor technologies, some of which were studied and prototyped as far back as the 1950s, but funding and interest both dried up with the PWR/BWR and CANDU models took hold in the west. Things like liquid-solution FUEL reacotrs, where the fuel itself is the primary loop coolant, and only goes critical as it passes through a properly-shaped reaction chamber with the right reflectors and moderators arranged around it. Need to SCRAM the reactor? Dump the coolant/fuel into a bank of long cylindrical tanks immersed in borated water where it cannot become critical, and where the residual heat can be managed... even passively. And parallel 10 small ones so that when one is down, the others can keep generating power.
 
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Originally Posted By: OVERKILL
I would say that it boils down to greed, which is the same reason none of the later recommended safety updates proposed during audits were done at Fukushima (like the relocation of the generators and their fuel tanks, the increase in the size of the sea wall...etc). Hopefully TEPCO and the Japanese power industry as a whole have learned from the situation at Fukushima, since, as noted in Shannow's thread, there are a lot of reactors coming online and I am betting many of them are similar in design.
GREED? REALLY??? The Japanese have been raised to think of themselves as part of a group, and their group is always dealing with other groups. Internationally it is "We Japanese" vs. everyone else, but in schools, companies, sections of companies etc. there are many groups and sub-groups -- and not always in perfect harmony and cooperation as it may look on the surface. Do NOT judge with your Western thinking!!!!
 
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Urban legend says that TEPCO wants to preserve the reactor instead of rushing sea water in to flood / cool it, partly because once you do that the reactor and fuel are pretty much poisoned beyond future use, and partly because the nuclear waste has valuable source of Pu239 that could be used for atomic weapon, just in case one day they want to build up a weapon program if they can get out of US military influence. In some way it is the US' class-action lawsuit culture that keeps big companies from doing risky things like TEPCO did in Japan, intentionally.
 
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Originally Posted By: turtlevette
Do you Canadians use the candu in your aircraft carriers and subs? The power density probably is not there.
I don't believe Canada has any nuclear powered vessels, so the answer seems to be "no".
 
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Really very well written 440magnum and OVERKILL... I have watched videos regarding the nuclear accident at Chernobyl to learn why it happened. And I will tell everyone here this very seriously and solemnly that I have seen a similar incident firsthand involving healthcare. The striking similarity of human behavior in the Chernobyl accident and what I saw was stunning. The human behavior factor cannot be taken out of any circumstance whether it be nuclear tests or healthcare. I believe that 440's idea of 10 smaller reactors is very good idea. Ohh and Three Mile Island was not far at all from total meltdown itself. When cameras were able to look into the reactor it was realized just how serious it really was. Literally just a half an hour to an hour away from total meltdown. The engineers who had built the reactor had been trying for hours to get through a land line phone call into the reactor. Granted the reactor containment building was much better than the Soviet design at Chernobyl. But it still would have had very severe effects for this country. Ohh and I've learned that several Russian men more than likely saved Kiev, Moscow, and much of western Europe from a massive nuclear explosion on the magnitude of 3-5 megatons. Which would have irradiated all of those areas and killed many tens of thousands more. Those Russian divers who manually opened the water valves underneath the destroyed reactor at Chernobyl are true heroes. It was later found that in fact the white hot magma had into made it into underneath the damaged reactor. Wow. That was more than a close call.
 
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OVERKILL

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Originally Posted By: turtlevette
Do you Canadians use the candu in your aircraft carriers and subs? The power density probably is not there.
Have you seen our military? LOL! There's no room in the budget for that wink I'd say the density probably is there, but given the lack of association between AECL and the military, as well as the fact we have no need to have those vessels cruising the globe like the US does, and of course the budget limitations, it is something that would be a non-starter.
 
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Japan has long wanted to be a developer and exporter of nuclear plant technology not an importer. The Fukushima plant was built, perhaps reluctantly out of needing the power before domestic designs were complete, in the early 1970's. Because it uses non-enriched uranium and has on-line refueling capability, a CANDU is more of a proliferation risk than other designs that use expensive enriched uranium and also must run the fuel longer because they shut down to replace it. The production of weapons-grade plutonium is based on used fuel that has been reacted for a relatively short time. Fuel that has been reacted for a long time becomes increasingly contaminated with Pu-240 which does not work well in a bomb.
 

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Originally Posted By: OVERKILL
Originally Posted By: turtlevette
Do you Canadians use the candu in your aircraft carriers and subs? The power density probably is not there.
Have you seen our military? LOL! There's no room in the budget for that wink I'd say the density probably is there, but given the lack of association between AECL and the military, as well as the fact we have no need to have those vessels cruising the globe like the US does, and of course the budget limitations, it is something that would be a non-starter.
You guys have like 2 or 3 submarines. I have been on one. Not to sound like an [censored], but you don't need a huge defense budget when the US is your next door neighbor. smile
 

OVERKILL

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Originally Posted By: mk378
Because it uses non-enriched uranium and has on-line refueling capability, a CANDU is more of a proliferation risk than other designs that use expensive enriched uranium and also must run the fuel longer because they shut down to replace it. The production of weapons-grade plutonium is based on used fuel that has been reacted for a relatively short time. Fuel that has been reacted for a long time becomes increasingly contaminated with Pu-240 which does not work well in a bomb.
Weapons grade versus reactor grade plutonium is covered in great detail here as well as here.
Quote:
A CANDU reactor, like all commerical power reactors, creates plutonium in its fuel which could be used in the manufacture of a nuclear device (albeit of limited usefulness - see related FAQ). Under the auspices of the International Atomic Energy Agency (IAEA), an agency of the United Nations, a number of safeguards are applied to CANDU reactors that meet the international convention of (a) timely detection of the diversion of nuclear material, and (b) deterrence of such diversion in the first place, due to the capability for timely detection. As with all commercial power reactors, these safeguards are based primarily on accountability of the fuel inventory at all stages of its movement (including within the reactor core), utilizing overlapping layers of "containment" (physical barriers) and "surveillance" (monitoring), backed up by periodic inspections. To date there has been no documented diversion of fuel from any CANDU reactor. While safeguards represent sufficient external measures to reduce the proliferation risk to an internationally-acceptable level, a number of inherent features are also found in CANDU technology that reduce the risk of proliferation. First and foremost, natural-uranium-fuelled CANDU reactors require no uranium enrichment capability by a host state, decoupling civilian power generation from one of the key technologies in the manufacture of nuclear weapons. Secondly, the significantly large mass of CANDU spent fuel required for the extraction of usable amounts of plutonium (weighing over two tonnes, without shielding), comprising of a large number of components (over a hundred fuel bundles), makes undetected diversion a non-trivial challenge. Thirdly, the relatively low concentration of plutonium in CANDU spent fuel (roughly half the already-low concentration in light-water spent fuel) reduces its proliferation attractiveness by adding to the scale and complexity of any subsequent extraction process. Finally, the on-power refuelling of a CANDU reactor is necessarily automated and therefore an easily monitored procedure, operating in conditions of intense heat and radiation, at a rate that cannot readily be increased.
Regarding your first point, I am sure that is the case. GE was partnered with various Japanese companies for Fukushima, which is why the reactors are all differently branded despite sharing the same designs. And of course we now have the merger of GE and Hitachi's nuclear divisions. However, the issues with corruption and negligence at TEPCO, arguably resulting in the Fukushima disaster, really gives the whole industry in Japan a black eye. As noted in my opening article, accountability really seems to play a big role here too.
 
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Originally Posted By: PandaBear
Urban legend says that TEPCO wants to preserve the reactor instead of rushing sea water in to flood / cool it, partly because once you do that the reactor and fuel are pretty much poisoned beyond future use, and partly because the nuclear waste has valuable source of Pu239 that could be used for atomic weapon, just in case one day they want to build up a weapon program if they can get out of US military influence.
Good luck with that. They need to locate that corium first: http://www.fukuleaks.org/web/?p=15666
 
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Originally Posted By: bbhero
Russian men more than likely saved Kiev, Moscow, and much of western Europe from a massive nuclear explosion on the magnitude of 3-5 megatons.
That doesn't happen. The SL-1 demonstrated that even a totally out of control reactor won't go up in a mushroom cloud with devastating blast damage like an atomic bomb. There was only a minor explosion that didn't damage beyond the building. To make a nuclear bomb takes highly concentrated fuel and a means to explosively force it into critical mass. Were a simple pile of core melt to reach critical mass and start a chain reaction, it would heat up rapidly and blow itself apart into a non-critical configuration before there is a significant nuclear yield. As for "3-5 megatons", the British tried to develop a fission-only "megaton class" weapon using large amounts of highly enriched uranium in an optimized bomb configuration. The program was discontinued as tests of those bombs only yielded about 400 kilotons. The only successful megaton size bombs involve a fusion stage.
 
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OVERKILL

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Originally Posted By: mk378
Originally Posted By: bbhero
Russian men more than likely saved Kiev, Moscow, and much of western Europe from a massive nuclear explosion on the magnitude of 3-5 megatons.
That doesn't happen. The SL-1 demonstrated that even a totally out of control reactor won't go up in a mushroom cloud with devastating blast damage like an atomic bomb. There was only a minor explosion that didn't damage beyond the building. To make a nuclear bomb takes highly concentrated fuel and a means to explosively force it into critical mass. Were a simple pile of core melt to reach critical mass and start a chain reaction, it would heat up rapidly and blow itself apart into a non-critical configuration before there is a significant nuclear yield. As for "3-5 megatons", the British tried to develop a fission-only "megaton class" weapon using large amounts of highly enriched uranium in an optimized bomb configuration. The program was discontinued as tests of those bombs only yielded about 400 kilotons. The only successful megaton size bombs involve a fusion stage.
thumbsup Little Boy was an enriched Uranium bomb and was ~15KT.
 
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Well that's not my thought or hypothesis here...... it was the nuclear physicists from the former Soviet Union at the time of the incident. Good, bad, or indifferent... I just don't believe that water exposed to almost 3000°C magma from the core would have gone well... at bare minimum this would've caused a far greater potential for a far bigger explosion than the first two.
 
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How do you quickly cool something that is so hot?
We can split atoms and quickly make air many times the temperature of the sun, but seems much more difficult to quickly cool something, you would literally be freezing molten fire.
 

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How do you quickly cool something that is so hot?
We can split atoms and quickly make air many times the temperature of the sun, but seems much more difficult to quickly cool something, you would literally be freezing molten fire.
I think the CANDU is less prone to core meltdown bc It does not require offsite electricity to allow gravity core cooling. The ultimate damage would be about the same as a U.S. PWR although on a lower scale. Ultimately the water boiling off as steam would require electricity to pump water into containment to replace water turning to steam.

In the case of TMI, instrumentation did not recognize the reactor was not water filled and the fuel melted down but did not breach the bottom of the reactor vessel.
 

OVERKILL

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I think the CANDU is less prone to core meltdown bc It does not require offsite electricity to allow gravity core cooling. The ultimate damage would be about the same as a U.S. PWR although on a lower scale. Ultimately the water boiling off as steam would require electricity to pump water into containment to replace water turning to steam.

In the case of TMI, instrumentation did not recognize the reactor was not water filled and the fuel melted down but did not breach the bottom of the reactor vessel.

Technical docs I've seen indicate that the SG's can be flooded in the CANDU to passively cool the units basically indefinitely in a shutdown state. The volume of water within the unit is large enough and the surface area over which heat is spread with the SG's flooded means that convection can be used. Note that every CANDU has a MASSIVE tank located above each unit for make up water and for, if required, performing the above.
 

OVERKILL

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How do you quickly cool something that is so hot?
We can split atoms and quickly make air many times the temperature of the sun, but seems much more difficult to quickly cool something, you would literally be freezing molten fire.
A lot of water. But remember, you aren't cooling something that's actively engaged in fission. That process is poisoned/killed, you are just removing the decay heat, which is significant, don't get me wrong, but it's far less than what's produced when the unit is critical. One of the big problems at Fukushima was getting water to the spent fuel pool, which dried out without circulation and had no way to replenish with the emergency generators flooded and the fuel tanks washed away. There was of course no fission taking place there, just significant decay heat from all of the fuel assemblies stored. It takes somewhere between 5 and 10 years for decay heat to peter off enough that the assemblies/bundles can be put into dry cask storage.

A CANDU, if the fuel channels deflect, it will take the unit from critical to non. That's why they are oriented horizontally, because in the event that there was a massive pressure tube failure event or a LOC where the water in the calandria escaped, the tubes would quickly overheat, bend, and take the unit non-critical. A CANDU can't maintain fission without heavy water because it uses natural uranium. Of course the reactor would be scrap at that point, so you'd never want that to happen, so every attempt is made to keep the unit intact which means redundant control rod systems to kill criticality, redundant poison systems if the control rod systems fail. So there are 4x systems to rapidly kill any reactivity and leave you with just having to deal with decay heat, which is far easier to work with. We have had two pressure tube failures in units over the years, one was a huge split at Pickering very early on due to a materials issue. Both of those units are still operational.
 
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