Plutonium production, continuous

Irradiated Fuel A historically important and continuing mission at the Hanford site is to chemically process irradiated reactor fuel to recover and purify weapons-grade plutonium. Over the last 40 years, or so, several processes and plants— Bismuth Phosphate, REDOX, and PUREX—have been operated to accomplish this mission. Presently, only the Hanford PUREX Plant is operational, and although it has not been operated since the fall of 1972, it is scheduled to start up in the early 1980 s to process stored and currently produced Hanford -Reactor fuel. Of nine plutonium-production reactors built at the Hanford site, only the N-Reactor is still operating. 

The UK and France were the first countries to develop civil nuclear energy in Europe building upon their separate experiences with gas cooled reactors devoted to military plutonium production. In the 1960s France altered its technology policy to favor pressurized water reactors while the UK did not make an equivalent policy choice until 1979 with policy implementation spanning the 1980s. France and the UK are the only EU-15 countries ever to have been nuclear weapons states and both states continue to maintain nuclear weapons capacity. 

Now that DuPont would be building the plutonium production complex in the Northwest, Compton saw no reason for any pile facilities in Oak Ridge and proposed to conduct Met Lab research in either Chicago or Argoime. DuPont, on the other hand, continued to support a semiworks at Oak Ridge and asked the Met Lab scientists to operate it. Compton demurred on the grounds that... 

At the Metallurgical Laboratory, the principal motivation of interest in homogeneous reactors was to develop alternate plutonium production facilities to be used in the event that the Hanford reactors did not operate successfully on a suitable large scale, and studies were continued through 1944. With the successful operation of the Hanford reactors, however, interest in homogeneous plutonium producers diminished, and by the end of 1944 very nearly all developmental research had been discontinued. The results of this work are summarized in a book by Kirschenbaum [12]. 

Continuous plutonium recovery. Continuous removal of neptunium or plutonium is possible in a liquid-fuel reactor. This yields a product with a loiv Pu ° content and increases the value of the plutonium [23]. 

Plutonium. A considerable investigation of the chemistry of plutonium in aqueous uranyl sulfate solutions has been directed, not toward the achievement of solubility, but toward the achievement of insolubility in order to provide the basis for continuous processing of a blanket solution for plutonium production [25] (see Chapter 6). 

X PILE. A graphite reactor was built at Site X, Oak Ridge, Tennessee, to produce plutonium for the Manhattan Project. The original intent was to prove the feasibility for scale-up from the laboratory level prior to undertaking full-scale plutonium production at Site W, Hanford, Washington. This reactor, known variously as the X Pile, X-10 Pile, and Clinton Pile, was the world s first continuously operated nuclear reactor. It operated for 20 years, from 4 November 1943 until 4 November 1963. After World War II, the reactor became the world s single... 

The Natural Reactor. Some two biUion years ago, uranium had a much higher (ca 3%) fraction of U than that of modem times (0.7%). There is a difference in half-hves of the two principal uranium isotopes, U having a half-life of 7.08 x 10 yr and U 4.43 x 10 yr. A natural reactor existed, long before the dinosaurs were extinct and before humans appeared on the earth, in the African state of Gabon, near Oklo. Conditions were favorable for a neutron chain reaction involving only uranium and water. Evidence that this process continued intermittently over thousands of years is provided by concentration measurements of fission products and plutonium isotopes. Usehil information about retention or migration of radioactive wastes can be gleaned from studies of this natural reactor and its products (12). 

Synthesis of plutonium in significant quantities requires a sufficiently long reactor fuel irradiation period. Uranium, plutonium, and the fission products obtained after neutron irradiation are removed from the reactor and stored under water for several weeks. During such cooling periods most neptunium-239 initially formed from uranium and present in the mixture transforms to plutonium-239. Also, the highly radioactive fission products, such as xenon-133 and iodine-131 continue to decay during this period. 

Previous experience in the production of plutonium 238 revealed the need for the double alpha containment of the cells where the alpha-emitter isotopes with high specific activity are handled. Thus all the hot cells are equipped with a double ventilation system which provides ventilation of alpha-cells and ventilation between alpha-cells and biological shields. Alpha detectors continuously monitor the exhaust circuits. 

A continuing problem with the cation exchange process as used in production operations is that it has not been sufficiently selective and therefore allows considerable carryover of the MSE salt constituents and impurities with the plutonium and americium. This isn t serious with plutonium since plutonium can be subsequently purified by anion exchange. For americium, however, the subsequent recovery process is oxalate precipitation which is less selective and carries some of the impurities into the final product. 

The Purex process will continue to be the main method for the reprocessing of nuclear reactor fuels. The inherent flexibility of this process allows for modifications needed to accomodate a large range of fuel compositions and product specifications. Among the several plutonium partitioning methods developed, those avoiding the introduction of extraneous metal ions... 

The emphasis on production of pure plutonium for weapons continued throughout the Cold War period. The successful control of the chain reaction to power submarines to cruise underwater for weeks rather than hours for the diesel-electric powered substitutes opened up a new option. The contractors that built the nuclear reactors and steam turbines for submarines also served the electric power utilities. Extension of this nuclear technology to domestic electric power production was obvious. President Eisenhower s Atoms for Peace initiative in 1954 opened the way for the nuclear power plants that followed that currently supply about 20% of the electric power to the U.S. power grid. 

In the Aquafluor process [G4] developed by the General Electric Company, most of the plutonium and fission products in irradiated light-water reactor (LWR) fuel are separated from uranium by aqueous solvent extraction and anion exchange. Final uranium separation and purification is by conversion of impure uranyl nitrate to UFg, followed by removal of small amounts of PuF , NpFg, and other volatile fluorides by adsorption on beds of NaF and Mgp2 and a final fractional distillation. A plant to process 1 MT/day of irradiated low-enriched uranium fuel was built at Morris, Illinois, but was never used for irradiated fuel because of inability to maintain on-stream, continuous operation even in runs on unirradiated fuel. The difficulties at the Morris plant are considered more the fault of design details than inherent in the process. They are attributed to the attempt to carry out aqueous primary decontamination, denitration, fluorination, and distillation of intensely radioactive materials in a close-coupled, continuous process, without adequate surge capacity between the different steps and without sufficient spare, readily maintainable equipment [G5, R8]. 

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