Editer l'article Suivre ce blog Administration + Créer mon blog
Le blog de fukushima-is-still-news

information about Fukushima published in English in Japanese media info publiée en anglais dans la presse japonaise

60 years after, the unfulfilled promise of breder reactors



Even before two A-Bombs were dropped on Japan in 1945, starry-eyed nuclear scientists were planning for a future world in which plutonium and thorium would become the principal energy resources of human society, replacing uranium as a nuclear fuel. This dreamy-eyed vision has always been considered of paramount importance to the future of nuclear energy — and nuclear weaponry. 

The only naturally-occurring element that can be used as a nuclear explosive in an A-Bomb or as fuel for a nuclear reactor, is a rare type of uranium called uranium-235 (U-235). When uranium deposits are found in nature, only 7 uranium atoms out of a thousand are U-235. Virtually all of the other uranium atoms are of a different type called uranium-238 (U-238). 

U-238 is a "non-fissile” variety of uranium, often called “depleted uranium” (DU). U-238 is far more abundant than U-235, but it cannot be used as a nuclear explosive or as fuel for a nuclear reactor. Similarly, Thorium-232 (Th-232) is a naturally-occurring element three times more abundant than U-238, but it is not fissile either. 

However, there’s a trick that nuclear scientists learned way back in the early 1940s. It’s a way to make U-238 and Th-232 “breed” new elements -- human-made, artificial elements — that are fissile, and perfectly suited for use in nuclear reactors or nuclear weapons. For this reason, U-238 and Th-232 are said to be “fertile” elements, because they breed fissile materials.

When an atom of uranium-238 absorbs a neutron, it becomes an atom of plutonium-239.  And when an atom of thorium-232 absorbs a neutron, it becomes an atom of uranium-233. Both of these human-made materials, plutonium-239 and uranium-233, are fissile — they are both excellent candidates to be used as an explosive in nuclear weapons or as fuel for nuclear reactors. Neither of them occurs in nature.  They are human-made.

Breeder reactors are specifically designed to breed large quantities of plutonium-239 and/or uranium-233 in order to extend the supply of fissile materials, which — unless replenished — will not long outlast the world’s oil supplies. There is simply not enough uranium-235 to allow nuclear power to replace a significant amount of the world’s oil consumption. At present, nuclear power produces about 11 percent of global electricity, but that’s less than 2 percent of the world’s energy use (most of which is non-electrical).

Up to the present time, most breeder reactors have been built to mass-produce plutonium-239, although breeding uranium-233 using thorium-232 as a “starter” has been repeatedly tried. At Chalk River, for example, in the late 1940 and early 1950s, there were two “reprocessing plants” — one to extract plutonium-239 from irradiated uranium fuel rods, and one to extract uranium-233 from irradiated thorium rods.  (You can’t call them “fuel rods” because thorium is not a fuel.)

One of the biggest worries associated with breeder reactors is the very real danger of the proliferation of nuclear weapons — not only spreading these doomsday devices to other countries, but also to terrorist groups and criminals. For plutonium and uranium-233 are very powerful nuclear explosive materials, and if stolen or diverted can be fabricated into formidable nuclear explosive devices that can be delivered to their targets in any number of ways -- even in the trunk of an auto.

Such is not the case with today’s nuclear power reactors. Normal uranium reactor fuel cannot be used as a nuclear explosive because there is too much uranium-238 mixed with the uranium-235, and there is no practical way to easily or quickly remove the U-238. The situation would change drastically if plutonium or uranium-233 were used as reactor fuel, for such fuel could readily be converted to a powerful nuclear explosive.

Many breeder reactor programs around the world have failed.  The Fermi-1 reactor just outside Detroit was an experimental breeder that suffered a partial meltdown and was scrapped; it was the subject of the book “We Almost Lost Detroit”. The Superphénix in France was a breeder reactor that was a spectacular failure at the time and marked the beginning of the decline of the French nuclear power industry. The SMR-300 breeder reactor in Germany was abandoned without ever operating. Nevertheless, interest in breeder reactors continues because without it the nuclear enterprise has no long-term future. Some of the small modular reactors (SMRs) currently proposed are breeders.


In 2010 the International Panel on Fissile Materials said "After six decades and the expenditure of the equivalent of tens of billions of dollars, the promise of breeder reactors remains largely unfulfilled and efforts to commercialize them have been steadily cut back in most countries". In Germany, the United Kingdom, and the United States, breeder reactor development programs have been abandoned.

Now Japan has joined the parade, abandoning its Monju breeder reactor for good. 

Gordon Edwards,


Monju Breeder Reactor Abandoned

Japan prepares to shut down its

troubled ‘dream’ nuclear reactor 


Decades-old plant has cost almost 

$10 billion and hardly ever operated    


KAZUNARI HANAWA, Nikkei staff writerApril 06, 2018 


or https://nuclear-news.net/2018/04/06/the-end-for-japans-expensive-monju-nuclear-fast-breeder-dream/ 

TOKYO — Japan is set to start decommissioning its troubled Monju fast-breeder reactor after decades of accidents, cost overruns and scandals. It is the beginning of the end of a controversial project that exposed the shortcomings of the country’s nuclear policy and the government’s failure to fully explain the risks and the costs.


In July, the Japan Atomic Energy Agency will begin decommissioning what was hailed as a “dream” reactor that was expected to produce more nuclear fuel than it consumed. The government has so far spent more than 1 trillion yen ($9.44 billion US) on the plant, which has barely ever operated.


The plan approved by the Nuclear Regulation Authority on March 28 to decommission the reactor, located in central Japan’s Fukui Prefecture, calls for the extraction of spent nuclear fuel to be completed by the end of the fiscal year through March 2023. Full decommissioning is expected to take about 30 years.


 Total costs to shut down the reactor are currently estimated at 375 billion yen, but that could climb, as the full technical requirements and the selection of the nuclear waste sites are not well understood.


Japan does not have the technological ability to manage the decommissioning process on its own, and must enlist the help of France, which has more experience with fast-breeder reactors. Among the technical challenges is handling the plant’s sodium coolant, which is highly reactive and explodes on contact with air.


Many of the problems with Japan’s nuclear policy were brought to light by the Fukushima Daiichi nuclear disaster caused by the tsunami and earthquake of March 2011. Such problems have included the high costs of plants, the selection of nuclear disposal sites, and the threat of shutdowns due to lawsuits. Japan’s nuclear policy has largely been gridlocked since the disaster.


But the Monju project had many problems before the Fukushima catastrophe.

Planning for the project began in the 1960s. Its fast-breeder technology was considered a dream technology for resource-poor Japan, which had been traumatized by the oil crisis of the 1970s. The reactor was supposed to generate more plutonium fuel than it consumed.

The reactor finally started operating in 1994, but was forced to shut down the following year due to a sodium leak. It has been inoperative for most of the time since. The decision to decommission it was made in December 2016 following a series of safety scandals, including the revelation that many safety checks had been omitted.


Recent experience suggests the government’s estimated cost of 375 billion yen to decommission Monju could be on the low side. In 2016, the estimate for decommissioning the Fukushima Daiichi plant ballooned to 8 trillion yen [$74.8 billion US] from an initial 2 trillion yen in 2013, largely due to inadequate understanding of the decommissioning process.


While “the JAEA will try to keep costs down,” said Hajime Ito, executive director with the agency, the process of extracting sodium, the biggest hurdle, has yet to be determined. Future technical requirements will also involve significant costs.

The Monju reactor is not the only example of failure in Japan’s nuclear fuel cycle policy — the cycle of how nuclear fuel is handled and processed, including disposing nuclear waste and reprocessing used fuel.


Central to this policy is a nuclear fuel reprocessing plant in the village of Rokkasho in northern Aomori Prefecture that was supposed to extract plutonium and uranium by reprocessing spent nuclear fuel to be reused at nuclear plants.


More than 2 trillion yen [$18.7 billion US] has been spent on the plant so far. Construction was begun in 1993, but completion has been repeatedly postponed due to safety concerns. On Wednesday, the NRA decided to resume safety checks on the plant, but if it chooses to decommission it, the cost would be an estimated 1.5 trillion yen  [$14 billion US] .


Had Japan taken into consideration the costs of decommissioning plants and disposing of spent nuclear fuel, it probably would not have been able to push ahead with its nuclear policy in the first place, said a former senior official of the Ministry of Economy, Trade and Industry, who was involved in formulating the country’s basic energy plan.



Partager cet article
Pour être informé des derniers articles, inscrivez vous :
Commenter cet article