Plutonium processing chemical

Groves moved on to Berkeley more impressed with their work than his Met Lab auditors realized. I left Chicago feeling that the plutonium process seemed to ofier us the greatest chances for success in producing bomb material, he recalls. Every other process. .. depended upon the physical separation of materials having almost infinitesimal differences in their physical properties. Transmutation by chain reaction was entirely new, but the rest of the plutonium process, chemical separation, while extremely difficult and completely unprecedented, did not seem to be impossible. ... 

The symposium was designed to provide an overview of the current status of plutonium chemistry by practitioners in the various areas covered. The authors, drawn from U.S. and foreign universities and national laboratories, were encouraged to include review material to place their subjects in perspective, as well as to suggest what they believe to be productive directions for future investigation. We find it particularly useful that the contributions represent a mixture of fundamental as well as more applied environmental and process chemical research. Although we do not claim that this volume represents all areas of plutonium chemistry that are currently under active investigation, this collection does represent a reasonably broad and balanced view of the field. The contents of the volume should be useful as a reference both for those familiar with actinide chemistry and for those with limited interests who seek an introduction to the literature and current status in an area of plutonium chemistry. 

The fission product and encapsulation plant (FPCE) to be built by Isochem, Inc.y in Washington state will produce fully encapsulated fission products for the commercial market. Among these, all of which are extractable from Hanford s plutonium process residues, is cesium-137, a 600-kv. gamma emitter of interest to the process irradiation industry. Isochem will offer cesium in large production quantities and low cost to irradiators of foods, woods, chemicals, etc. Its 30-year half-life promises economies in source array replenishment to compensate for decay. Cesium thus becomes an economic contender for current and planned irradiation applications. 

Like microflltration, ultraflltration process can also be used in conjunction with chemical precipitation techniques to improve decontamination factors. Ultrafiltration processes could be useful for decontaminating alpha wastes from laundry and washing water streams of plutonium-processing plant on a large scale [15,16]. 

The classical Purex process was designed to produce nearly pure uranium and plutonium. The Chemical Engineering Division of Argonne National Laboratory has demonstrated UREX+, an advanced aqueous process with five extraction trains that split commercial reactor spent fuel into five streams 1) a nearly pure uranium stream (95.5% of the heavy metal in the spent fuel) 2) technetium sent to transmutation (0.08 /o) 3) Pu/Np converted to MOX fuel for LWR fuel and Am/Cm for transmutation or fast-flux reactor fuel (0.962 /o) 4) Cs/Sb decay heat producers sent to interim decay storage (0.017 /o) and 5) a mixed fission product stream (3.44 /o) composed of gases and solids incorporated into a waste form for geological repository disposal.f The percentages shown are computed from Table 1. 

Nuclear wastes are classified according to the level of radioactivity. Low level wastes (LLW) from reactors arise primarily from the cooling water, either because of leakage from fuel or activation of impurities by neutron absorption. Most LLW will be disposed of in near-surface faciHties at various locations around the United States. Mixed wastes are those having both a ha2ardous and a radioactive component. Transuranic (TRU) waste containing plutonium comes from chemical processes related to nuclear weapons production. These are to be placed in underground salt deposits in New Mexico (see... 

Chemical Separation. A reprocessing facility typically utilizes multiple extraction/reextraction (stripping) cycles for the recovery and purification of uranium and plutonium. For example, a co-decontamination and partitioning cycle is followed by one or more cycles of uranium and plutonium purification. The basic process is illustrated in Figure 3. 

Uranium. The uranium product from the PUREX process is in the form of uranyl nitrate which must be converted to some other chemical depending on anticipated use. One route to MO fuel is to mix uranium and plutonium nitrates and perform a coprecipitation step. The precipitate is... 

Chemical processing or reprocessing (39) of the fuel to extract the plutonium and uranium left a residue of radioactive waste, which was stored in underground tanks. By 1945, the reactors had produced enough plutonium for two nuclear weapons. One was tested at Alamogordo, New Mexico, in July 1945 the other was dropped at Nagasaki in August 1945. 

Evidence foi the anionic complex PuCP is the precipitation of complex halides such as Cs2PuClg from concentrated HCl (aq). The ability of Pu(IV) to form stable nitrate complexes provides the basis for the Purex and ion-exchange (qv) process used in the chemical processing of Pu (107). Pu(VI) is similar to Pu(IV) in its abihty to form complex ions. Detailed reviews of complex ion formation by aqueous plutonium are available (23,94,105). 

Nuclear power reactors cause the transmutation of chemicals (uranium and plutonium) to fission products using neutrons as the catalyst to produce heat. Fossil furnaces use the chemical reaction of carbon and oxygen to produce CO2 and other wastes to produce heat. There is only one reaction and one purpose for nuclear power reactors there is one reaction but many puiposes for fossil-burning furnaces there are myriad chemical processes and purposes. 

Since the amount of fissile material in the fuel assemblies is only about 3 percent of the uranium present, it is obvious that there cannot be a large amount of radioactive material in the SNF after fission. The neutron flux produces some newly radioactive material in the form of uranium and plutonium isotopes. The amount of this other newly radioactive material is small compared to the volume of the fuel assembly. These facts prompt some to argue that SNF should be chemically processed and the various components separated into nonradioac-tive material, material that will be radioactive for a long time, and material that could be refabricated into new reactor fuel. Reprocessing the fuel to isolate the plutonium is seen as a reason not to proceed with this technology in the United States. 

When the Plutonium Project was established early in 1942, for the purpose of producing plutonium via the nuclear chain reaction in uranium in sufficient quantities for its use as a nuclear explosive, we were given the challenge of developing a chemical method for separating and isolating it from the uranium and fission products. We had already conceived the principle of the oxidation-reduction cycle, which became the basis for such a separations process. This principle applied to any process involving the use of a substance which carried plutonium in one of its oxidation states but not in another. By use of this... 

Although the outline of a chemical separation process could be obtained by tracer-scale investigations, the process could not be defined with certainty until study of it was possible at the actual separation plants. Therefore, the question in the summer of 1942, was as follows How could any separations process be tested at the concentration of plutonium that would exist several years later in the production plants when, at this time, there was not even a microgram of plutonium available This problem was solved through an unprecedented series of experiments encompassing two major objectives. First, it was decided to attempt the production... 

Other reasons for investigating plutonium photochemistry in the mid-seventies included the widely known uranyl photochemistry and the similarities of the actinyl species, the exciting possibilities of isotope separation or enrichment, the potential for chemical separation or interference in separation processes for nuclear fuel reprocessing, the possible photoredox effects on plutonium in the environment, and the desire to expand the fundamental knowledge of plutonium chemistry. 

Research into the aquatic chemistry of plutonium has produced information showing how this radioelement is mobilized and transported in the environment. Field studies revealed that the sorption of plutonium onto sediments is an equilibrium process which influences the concentration in natural waters. This equilibrium process is modified by the oxidation state of the soluble plutonium and by the presence of dissolved organic carbon (DOC). Higher concentrations of fallout plutonium in natural waters are associated with higher DOC. Laboratory experiments confirm the correlation. In waters low in DOC oxidized plutonium, Pu(V), is the dominant oxidation state while reduced plutonium, Pu(III+IV), is more prevalent where high concentrations of DOC exist. Laboratory and field experiments have provided some information on the possible chemical processes which lead to changes in the oxidation state of plutonium and to its complexation by natural ligands. 

These processes do not operate independently for example, the behavior of plutonium in step 3 will be greatly dependent on the species formed as a result of solution-phase reactions in step 2. However, from a chemical standpoint, we have found that consideration of these processes individually is a useful aid to understanding the transport of plutonium in a ground-water system. 

Chemical processing activities involve the recovery of plutonium from Rocky Flats Plant scrap, waste materials and residues, and effluent streams. The final product of this recovery and purification effort is high-purity plutonium metal for use in foundry operations. 

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. 

Conner, W. V. "Process Studies on the Reduction of Plutonium Tetrafluoride to Metal," U.S. AEC Rept. RFP-728, Dow Chemical Company, Golden, Colorado, May 11, 1966. 

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