Wednesday, December 14, 2011

Stop Wasting Valuable Nuclear Fuel

If reprocessing is revived in the United States, used fuel could become an important energy source. If not, it will remain in storage indefinitely as a lost opportunity._William H Miller Professor of Nuclear Science & Engineering
In spite of the doubts from skeptics, reprocessing is a game-changing technology that could turn a huge amount of used fuel left over from the production of nuclear-generated electricity into a significant energy resource. _William H Miller

Often mistaken for nuclear waste, used fuel contains large amounts of valuable plutonium and uranium that can be extracted and then chemically reprocessed into a so-called mixed-oxide, or MOX, fuel that can be used in a nuclear plant to produce more electricity. In 1977, President Jimmy Carter ended reprocessing in the United States, citing proliferation risks and hoping other countries such as France and Great Britain would do likewise. They didn’t.

They have continued to reprocess used fuel — in the case of France, using recycling as part of its nuclear program to obtain 80 percent of its electricity and to sell surplus power to neighboring countries.

Reprocessing has great potential value for the United States. Using it along with breeder reactors would recover 90 percent of the original energy that remains in the fuel after one use in a reactor. And it would extend uranium resources for hundreds of years and reduce by at least 50 percent the amount of long-lived nuclear waste that would need to be stored in a deep-geologic repository. Additionally, the heat and toxicity of such waste would be reduced, enabling the United States to store all of the long-lived waste from power reactors and the weapons program in a single repository instead of having to find sites and pay for the construction of multiple repositories. _William H Miller

Users of nuclear-generated electricity already have paid $17.9 billion into the trust fund since it was established more than 30 years ago. The fund continues to grow by $800 million annually to cover the costs of nuclear waste management. Considering the uncertain future of the Yucca Mountain project, now is the time to resurrect used-fuel reprocessing. This would simplify the challenge of nuclear waste storage and disposal. _William H Miller
Used fuel

With time, the concentration of fission fragments and heavy elements formed in the same way as plutonium in the fuel will increase to the point where it is no longer practical to continue to use the fuel. So after 18-36 months the used fuel is removed from the reactor. The amount of energy that is produced from a fuel assembly varies with the type of reactor and the policy of the reactor operator.

When removed from a reactor, the fuel will be emitting both radiation, principally from the fission fragments, and heat. Used fuel is unloaded into a storage pond immediately adjacent to the reactor to allow the radiation levels to decrease. In the ponds the water shields the radiation and absorbs the heat, which is removed by circulating the water to external heat exchangers. Used fuel is held in such pools for several months to several years. It may be transferred to naturally-ventilated dry storage on site after about five years.

Depending on policies in particular countries, some used fuel may be transferred to central storage facilities. Ultimately, used fuel must either be reprocessed or prepared for permanent disposal.


Used fuel is about 94% U-238 but it also contains almost 1% U-235 that has not fissioned, almost 1% plutonium and 4% fission products, which are highly radioactive, with other transuranic elements formed in the reactor. In a reprocessing facility the used fuel is separated into its three components: uranium, plutonium and waste, which contains fission products. Reprocessing enables recycling of the uranium and plutonium into fresh fuel, and produces a significantly reduced amount of waste (compared with treating all used fuel as waste). See page on Processing of Used Nuclear Fuel.

According to Areva, about eight fuel assemblies reprocessed can yield one MOX fuel assembly, two-thirds of an enriched uranium fuel assembly, and about three tonnes of depleted uranium (enrichment tails) plus about 150 kg of wastes. It avoids the need to purchase about 12 tonnes of natural uranium from a mine.

Uranium and plutonium recycling

The uranium from reprocessing, which typically contains a slightly higher concentration of U-235 than occurs in nature, can be reused as fuel after conversion and enrichment.

The plutonium can be directly made into mixed oxide (MOX) fuel, in which uranium and plutonium oxides are combined. In reactors that use MOX fuel, plutonium substitutes for the U-235 in normal uranium oxide fuel (see page on Mixed Oxide (MOX) Fuel). _World-Nuclear

A spent fuel (recycling fuel) that was once used at a nuclear power station contains 94% of unburnt uranium (about 1% of uranium 235 and about 93% of uranium 238), and about 1% of plutonium produced by uranium 238 that absorbed neutrons. They can be used again as fuels, if they are reprocessed. In Japan as a country poor in natural resources, the “nuclear fuel cycle” that reprocesses spent fuels, recover uranium and plutonium, and repeatedly use them for power generation is the basis of nuclear energy policy.

MOX Fuel Utilization (Pluthermal Plan)

Using the fuels that are made by mixing the plutonium extracted from reprocessed spent fuels with uranium in a light-water reactor (MOX fuel) is called “pluthermal process.” Pluthermal process already has a long track record of about 40 years, and continues to be practically used in France, Germany and Switzerland, etc. Japan's electric power companies are scheduled to introduce and start pluthermal process in 16 to 18 nuclear reactors by FY2010. Tohoku EPCo plans to start pluthermal process at one unit of Onagawa Nuclear Power Station by FY2010. To realize pluthermal process, Tohoku EPCo is intended to promote the activities to win the understanding of people, taking various opportunities for this purpose. _Tohoku Epco

Nuclear power requires a complex high technological infrastructure, utilising the highest standards of safety and quality control. In a society where the average IQ is 100, efficient nuclear power with fuel recycling can be safely utilised as long as the proper training and supervision is in place.

In a society with an average IQ of 85 -- such as most of the third world -- or in societies with average IQs under 80 -- such as most of Sub Saharan Africa -- nuclear power should probably not be used, due to the inability of such societies to field sufficient numbers of qualified scientists, engineers, and technicians. One exception to that rule of thumb would be oil-rich or mineral rich nations, which were willing and able to pay for outside ongoing technical assistance. But such a commitment would need to be open-ended for the indefinite future, or at least until decommissioning of the plant and auxiliary facilities.

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