nuclear fuel cycle

(redirected from defuelling)
Also found in: Dictionary.
Related to defuelling: defueled, duffed

nuclear fuel cycle

[′nü·klē·ər ¦fyül ‚sī·kəl]
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

Nuclear fuel cycle

The nuclear fuel cycle typically involves the following steps: (1) finding and mining the uranium ore; (2) refining the uranium from other elements; (3) enriching the uranium-235 content to 3–5%; (4) fabricating fuel elements; (5) interim storage and cooling of spent fuel; (6) reprocessing of spent fuel to recover uranium and plutonium (optional); (7) fabricating recycle fuel for added energy production (optional); (8) cooling of spent fuel or reprocessing waste, and its eventual transport to a repository for disposal in secure long-term storage. See Nuclear fuels

Steps 6 and 7 are used in Britain, France, India, Japan, and Russia. They are no longer used in the United States, which by federal policy has been restricted to a “once through” fuel cycle, meaning without recycle. Belgium, China, France, Germany, Japan, and Russia, with large and growing nuclear power capacities, use recycled plutonium. Disposal of highly enriched uranium from nuclear weapons is beginning to be undertaken by blending with natural or depleted uranium to make the 3–5% low-enrichment fuel. Similarly, MOX (mixed oxides) fuel capability can be used to dispose of plutonium stockpiled for nuclear weapons. This option is being planned in Europe and Russia, and is beginning to be considered in the United States.

Nuclear reactors produce energy using fuel made of uranium slightly enriched in the isotope 235U. The basic raw material is natural uranium that contains 0.71% 235U (the only naturally occurring isotope that can sustain a chain reaction). The other isotopes of natural uranium consist of 238U, part of which converts to plutonium-239, during reactor operation. The isotope 239Pu also sustains fission, typically contributing about one-third of the energy produced per fuel cycle. See Nuclear reactor

Various issues revolve around the type of nuclear fuel cycle chosen. For instance, the question is still being argued whether “burning” weapons materials in recycle reactors is more or less subject to diversion (that is, falling into unauthorized hands) than storing and burying these materials. Another issue involves the composition of radioactive wastes and its impact on repository design. The nuclear fuel cycles that include reprocessing make it possible to separate out the most troublesome long-lived radioactive fission products and the minor actinide elements that continue to produce heat for centuries. The remaining waste decays to radiation levels comparable to natural ore bodies in about 1000 years. The shorter time for the resulting wastes to decay away simplifies the design, management, and costs of the repository.

McGraw-Hill Concise Encyclopedia of Engineering. © 2002 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Following the completion of the defuelling the site will move into its care and maintenance preparations phase, which focuses on retrieving, treating and processing any wastes.
This is the culmination of years of hard work and significant investment in the plant to ensure defuelling can be carried out safely.
Defuelling had been carried on earlier in the day and gasoline had somehow been discharged into the harbour.
In addition, management-ignited fires on some 1,300 acres a year, mostly on the fuelly floor of Yosemite Valley, are set annually for defuelling and wildlife-habitat enhancement purposes.
The log showed another problem in October that year, when engineers defuelling the tank found that the quantity indicator was stuck at 11kg, when the tank was empty.
Stuart Law, Site Director, said: "At the start of defuelling, the reactors contained almost 90,000 fuel elements.
But on the other hand, defuelling the plane would have also caused more delay since Boeing was the only one authorized to do so according to the CAAP Spokesperson.
"We envisage that the defuelling programme will complete in mid to late 2019, with everyone working hard to achieve this target."
A Magnox Electric spokesman said it paves the way for decommissioning of Wylfa in 2012, after defuelling finishes.
A Magnox spokeswoman said: "Around 90 people have now left Wylfa as part of the reorganisation and move to the new defuelling structure.