18 Septembre 2012
September 18, 2012
Under the government's new energy strategy, announced last week, Japan will aim to end its reliance on nuclear energy during the 2030s. But the public was quick to spot a contradiction, as the strategy states that the nation's contentious nuclear fuel cycle policy will remain intact.
Why wouldn't the government decide to give it up at this point? Following are questions and answers about Japan's nuclear fuel cycle policy:
What is the nuclear fuel cycle?
The nuclear fuel cycle describes the stages the fuel goes through in its lifetime. Fuel that is only used once has an open nuclear cycle, whereas fuel that undergoes reprocessing is described as having a closed cycle. Since Japan must import practically all of its energy resources, it opted to pursue a closed cycle for its nuclear program.
The idea is to reprocess spent fuel by extracting the key materials, uranium and plutonium, and reuse them to generate power. Nuclear fuel is mainly made of uranium isotopes 235 and 238. The uranium 235 produces the fissile energy, while the uranium 238, which makes up the bulk of the fuel, produces plutonium, another fissile element, through the fission process.
Spent fuel usually contains a small amount of uranium 235 that can still generate fission. By extracting the uranium 235 and the plutonium and combining them with uranium 238, a fresh source of fuel can be produced.
When reprocessed fuel is used in a special type of reactor called a fast breeder, which uses sodium instead of water to cool the fuel, it increases the amount of plutonium in the fuel, allowing it to be extracted once the fuel is spent and reused.
In theory, a closed nuclear fuel cycle can produce fuel for hundreds of years.
What are the advantages of Japan's fuel cycle?
The fact that great amounts of energy can be produced through continuous recycling is attractive to resource-poor countries like Japan.
Some experts also say that since Japan is the only country without nuclear weapons to gain approval from the international community to sustain a nuclear fuel cycle, it would be unwise to get rid of such an intangible asset.
Another benefit is that reprocessing can reduce the amount of high-level radioactive waste produced by nuclear power plants — and the space needed to store it — by about half.
How successful has Japan been in developing its fuel cycle?
More than half a century has passed since the government committed to setting up the cycle in the 1950s, but implementation has dragged on for decades.
Fast-breeder reactors, while experimental, are a crucial piece of the plan. Japan has been betting on the Monju, a prototype fast breeder in Fukui Prefecture run by the Japan Atomic Energy Agency, to pave the way. Since it was built in 1991, however, the Monju has run into several problems, including a major fire triggered by a sodium-coolant leak that was later the subject of a coverup attempt. When sodium reacts with water, it catches fire.
Monju has never reached full-scale operation despite the ¥960 billion or so the government has poured into it.
In addition to fast breeders, reprocessing facilities are another key part of the cycle. But a reprocessing plant in Rokkasho, Aomori Prefecture, another experimental facility run by the Japan Nuclear Fuel Ltd., has experienced several problems in its quest for full operations and has cost more than ¥2 trillion so far.
Rokkasho is also building a plant to make MOX, an alternative reprocessed fuel made of mixed uranium oxides and weapons-grade plutonium that is designed for fast-breeder reactors.
Opponents of nuclear power have been pressuring the government to give up its fuel cycle quest in light of the prolonged failures of these two facilities.
Was the nuclear fuel cycle expected to take this long to set up when the policy was drafted?
No. According to the long-term nuclear power policy Japan compiled in 1961, a fast-breeder reactor was to be developed and in engaged in practical use by the late 1970s. That now looks unlikely to happen until the 2050s.
Hiroshi Tasaka, who was a special adviser to Prime Minister Naoto Kan during the Fukushima crisis, said it is obvious that the bureaucrats who drafted the fuel cycle plan were uninformed about the feasibility of the project.
In the planning stages, it is often difficult to say a project is scientifically impossible, but that doesn't necessarily mean it's feasible, said Tasaka, who has a doctorate in nuclear engineering and is a professor of business at Tama University.
"Seeing that the plan has been delayed this long, it means the policymakers didn't thoroughly examine its feasibility or that it is too difficult to achieve because of technological challenges. . . . I think it's a combination of both factors," Tasaka said.
On an NHK program about the fuel cycle in June, a former bureaucrat involved in the initial stages of drafting the fuel cycle policy said that because the United States was already developing a fast-breeder reactor for research in the 1950s, officials believed it would soon be put into practical use.
Meanwhile, professor Minoru Takahashi of the Tokyo Institute of Technology, an expert on fast-breeder reactors, said that Japan has the knowhow to build fast breeders for commercial use but that its safety technology needs further development before it can pass public muster.
Why isn't the government terminating the fuel cycle project if it is officially abandoning nuclear power?
In June, a panel set up by the Japan Atomic Energy Commission said that if the government decides to end the nation's reliance on nuclear power, there won't be any need to reprocess spent fuel and it should all be disposed of.
But it's not that easy. The central government is having difficulty winning over governments in areas that host all the facilities built for the cycle, especially Fukui and Aomori prefectures. These areas stand to lose huge government subsidies if the fuel cycle spigot is turned off.
Moreover, Aomori is concerned the central government may end up choosing it as a final disposal site for high-level radioactive waste because much of the nation's spent fuel is already sitting in storage at the Rokkasho facility.
The new energy policy states that the central government will keep its promise not to make Aomori a final disposal site.
Since the Rokkasho facility isn't running full bore yet, Japan has been shipping spent fuel to French and British facilities for reprocessing. The high-level radioactive waste produced as a byproduct is usually shipped back to Japan with the fuel. Both countries have called on Japan to make sure it will still be taken back.
The new energy strategy also gives consideration to the international community by saying the recycling program must be maintained to keep consuming plutonium for peaceful purposes and prevent nuclear materials from proliferating.
If the government ever decides to end the fuel cycle project, what would happen to the spent fuel?
Japan currently has about 14,200 tons of spent fuel and 29.6 tons of plutonium. Before the Fukushima disaster, it is estimated that the nation's reactors were producing 1,000 tons of spent fuel a year and were on course to exhaust all available storage space within six years.
If the fuel cycle is abandoned, the spent fuel would most likely be stored hundreds of meters underground and perpetually monitored because materials like plutonium remain dangerous for tens of thousands of years. The problem is, Japan hasn't found anywhere to build a permanent repository because no municipality will host it.
"The question of where to dispose of high-level radioactive waste has not been solved since I was a student (back in the 1970s)," said Tasaka, who researched high-level radioactive waste disposal methods for his doctoral thesis.
The waste eventually has to go somewhere, but Fukushima will make it incredibly difficult to find a spot.
If the Fukushima crisis hadn't occurred and the nuclear plants had kept their noses clean for another decade or so, it might have been possible to convince a municipality to host the final disposal site, Tasaka said. The disaster, however, has basically shattered those hopes, he said.
Given how difficult it is just to get municipalities to store lightly tainted tsunami debris from Tohoku, it will be challenging to find a site for storing high-level radioactive waste, Tasaka said.
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