Chemical Processes and Nuclear Reactor Fuel

There are about 557 nuclear power reactors in the world and about 440 are operating in early 2005.  These reactors have common elements that uranium oxide enriched to 3-4% ²³⁵U is fabricated into pellets then inserted into fuel rods.  These rods are neutron emitters and, in close proximity with each other, begin a self-sustaining chain reaction releasing energy and producing new elements by the fission of the uranium and producing plutonium (²³⁹Pu) by nuclear chain reactions. These fuel rods generally can supply energy from the fission reaction for 1-3 years.  They are then removed and replaced by new rods.

Spent fuel from nuclear reactors still contains considerable amounts of ²³⁵ U but now has generated significant ²³⁹Pu.  After 3 years in a reactor, 1,000 lbs. of 3.3-percent-enriched uranium (967 lbs. ²³⁸ U and 33 lbs. ²³⁵U) contain 8 lbs. of ²³⁵U and 8.9 lbs. of plutonium isotopes along with 943 lbs. of ²³⁸U and assorted fission products. Separating the ²³⁵U and ²³⁹Pu from the other components of spent fuel significantly addresses two major concerns. It greatly reduces the long-lived radioactivity of the residue and it allows purified ²³⁵U and ²³⁹Pu to be used as reactor fuel. (Courtesy of the Uranium Information Center)

Three options are available for cooled spent fuel rods; they can remain at the sites from which they have been removed from service, be moved to a more permanent site for storage or they can be reprocessed to remove the uranium and plutonium. In either case, these fuel rods must cool in storage ponds near the reactor for several months in order to reduce their short-lived radioactivity and to allow them to dissipate their initial high thermal energy. Reprocessing involves chopping up the fuel rods and dissolving the pieces. 

The plutonium and uranium are then removed and chemically  separated.  The byproducts of reprocessing, transuranic elements and fission products can be encapsulated in glass and disposed as waste. Gaseous diffusion or other processes can be used to enrich the uranium. The plutonium can be mixed with enriched uranium to make mixed oxide (MOX) reactor fuel. Purified plutonium can also be used for nuclear weapons. Great Britain and France have built large reprocessing plants to produce MOX fuel. They reprocess spent fuel not only from reactors in their respective countries, but also from reactors in other nations.

At one time, the United States planned to use a plutonium-uranium extraction (PUREX) process to for this separation.  But no spent fuel from nuclear power plants has been  reprocessed in the US.  In 1977 President Carter established national policy that prohibited reprocessing based on the premise that limiting plutonium would limit the spread of nuclear weapons around the world.  Although President Reagan reversed this policy, reprocessing has never been initiated in the US.

But in science, what can be done, will be done.  Local policy seldom deters the ambitions of the entire environment.

The French have reprocessed power plant spent fuel rods at the COGEMA LaHague site since 1966.  The French see reprocessing as ecologically sound, economical and profitable and as demonstrating scientific leadership on a world stage.

Quite naturally, the rise of organized terrorism since about 1990, culminating in the destruction of the Twin Towers in New York has focused attention on all aspects of nuclear material management.  As an example, the LaHague site was surrounded for a time by antiaircraft missiles for a time after the 2001 terrorist attacks.

In the US spent rods are currently stored at locations near the approximately 70 plants throughout the country. US fuel rod disposal planning anticipates opening a facility at Yucca Mountain, NV by 2012 for permanent burial of spent rods.

(Courtesy of the Department of Energy)

Complete Bibliography on Nuclear Power , Nuclear Waste  and Reprocessing from the ALSOS Digital Library for Nuclear Issues