Nitrate plutonium dioxide

Plutonium is subsequently stripped to an aqueous phase containing NH20H HN03 in the CC Column. In order to increase the plutonium concentration of the CC Column product, a portion of this stream (CAIS) is recycled to the CA Column after adjustment with HNO3. The remainder of the stream (CCP) is routed to the product concentrator. The resulting concentrated and purified plutonium nitrate solution is suitable feed to other processes for conversion to the desired product form (e.g., metal or plutonium dioxide). The remainder of the PRF solvent extraction system consists of a series of columns to wash the TBP-CCI4 solvent and prepare it for reuse. 

In contrast to the direct formation of a uranate species, there is evidence that both uranium and plutonium dioxide form a soluble species in molten alkali metal nitrates in the presence of nitric acid vapor (8, H)) or ammonium nitrate (70. How-... 

Plutonium Dioxide in Molten Equimolar Sodium-Potassium Nitrate. The behavior of plutonium dioxide in molten alkali metal nitrates is an area of major concern. Claims that alkali metal plutonates are formed (1, 2, 3, 5, 6) are not substantiated by definitive analytical results. In some cases (5, 6), sodium peroxide was added as an oxidant to either an alkali metal nitrate melt (6) or to an alkali metal hydroxide melt (5). If the temperature is great enough, for example above 700°C, thermal decomposition of the nitrate melt produces peroxide species. Other studies (4, , 12, 17) do not claim formation of a plutonate species, but only state that an insoluble plutonium-containing compound exists. However, in all the references cited, the results were given for mixed uranium-plutonium dioxide definitive analytical results were not given. 

Our studies of the behavior of plutonium dioxide in molten alkali metal nitrates were conducted in equimolar sodium-potassium nitrate without addition of peroxide. Melt temperatures were low enough so that thermal decomposition was not expected to produce peroxide species. In addition, we studied... 

For this study we chose a mass ratio of 1 100, plutonium dioxide-to-nitrate melt. The experiments were performed in a glove box, designed for containment of high alpha-activity materials. Plutonium dioxide and equimolar NaN03-KN(>3 were added to the reaction vessel, and the temperature was increased to 525°C. The temperature exceeded 350°C approximately three hours, and 500°C for at least one hour. No reaction of plutonium dioxide was noted at any time. The melt remained clear and colorless throughout the entire period. It therefore appears that plutonium dioxide does not react with the alkali metal nitrate melt to produce a plutonate within the temperature range cited (<525°C). The temperature of the melt was then reduced to 275°C, and nitric acid vapor was added. At no time were there any visual indications of solubility or reaction of the plutonium dioxide in the melt. 

Analytical results of the study of the behavior of plutonium dioxide in equimolar sodium-potassium nitrate show that, under the conditions cited, plutonium dioxide did not react and did not form a soluble species either with the original melt or with the addition of 100% nitric acid vapor. The analytical results were based on alpha-energy analysis of samples of the molten phase taken throughout the experiment. All molten phase samples were dissolved in 0.5 M HNO3. 

Mixed Uranium-Plutonium Dioxide in Equimolar Sodium-Potassium Nitrate. The behavior of two compositions of mixed uranium-plutonium dioxide has been investigated thus far at PNL. The first composition, designated material A, consists of 5.44% Pu02/94.56% UO2. The second composition, designated material B, consists of 27.56% Pu02/72.44% UO2. Both materials were acquired as pellets that had been sintered at 1700°C. The behavior of both mixed-oxide materials was studied under the same conditions used in the previous experiments. 

Although these studies are not complete, it appears that molten alkali metal nitrates will react with mixed uranium-plutonium dioxide material of varying composition. Higher melt temperatures and longer reaction times are required, however, as the plutonium enrichment is increased. The insolubility of plutonium dioxide must certainly be investigated further since its solubility in the molten phase upon addition of nitric acid vapor has been claimed in various patents (8, 10). It should... 

Our conceptual flowsheet for further decontamination of plutonium dioxide indicates oxidation of Pu02 with a nitrate melt containing peroxide. A plutonate species should form with this treatment. If formed, we expect the plutonate to be soluble in the melt upon addition of nitric-acid vapor. If this supposition is correct, then the plutonium could probably be recovered similar to uranium. Whether a plutonate or Pu02 would be obtained from the thermal decomposition of a soluble plutonate species is unknown for this system. 

We have determined that plutonium dioxide does not react with molten nitrates under the same conditions that uranium dioxide does. We have also determined that plutonium dioxide is not soluble in molten nitrates with the addition of 100% nitric acid vapor under conditions which did produce soluble uranium. This observation must be further verified under the various conditions which can produce the soluble uranium species. 

Preliminary investigation has shown that most fission products are not soluable in alkali metal nitrate melts and that they are not dissolved by addition of 100% nitric acid vapor. If these characteristics are verified by further experiments, a fission product separation is easily envisioned. One could react the fuel with the molten nitrate, dissolve the uranate with the addition of 100% nitric acid, and separate the uranium from the remaining solids, which should consist of both plutonium dioxide and fission products. 

Direct calcination of Pu(N03)4 involves no chemical separations that could remove impurities, so a highly pure plutonium nitrate feed solution is required. The plutonium dioxide product can be hydrofluorinated to PUF4, or it can be used as a feed for the formation of PUCI3. Direct calcination has received less industrial-scale application than the precipitation processes described above [C2]. 

Plutonium dioxide, prepared by direct calcination of Uie nitrate or calcination of the peroxide or oxalate precipitates, can be chlorinated to PuQ by HQ-Hj, gaseous CCI4, or phosgene (COCI2), the latter resulting in the most rapid reaction. 

Plutonium-238 is used to provide on board power for electronic systems in satellites. Plutonium- 239 is used primarily in nuclear weapons. Most plutonium is found combined with other substances, for example, plutonium dioxide (plutonium with oxygen) or plutonium nitrate (plutonium with nitrogen and oxygen). More information about the properties and uses of plutonium can be found in Chapters 3, 4, and 5. 

Depending on the plutonium compound, it may be either soluble or insoluble. Plutonium as the citrate or nitrate was more soluble than the dioxide compound. Plutonium dioxides prepared at temperatures of 700°C or higher had a slower absorption rate compared to air-oxidized forms (Sanders and Mahaffey 1979). The absorption of plutonium was also dependent upon its respirable fraction, or that fraction of the total concentration of plutonium which may deposit in the nonciliated part of the lung. The respirable fraction of plutonium is composed of particles less than 10 om Activity Median Aerodynamic- Diameter (AMAD), which indicates that only particles less than 10 om AMAD would be retained in the nonciliated part of the lung and would be available for absorption (NEA/OECD 1981 Volchoketal. 1974). 

Absorption of plutonium through wounds has occurred in humans occupationally exposed (Hammond and Putzier 1964). Experiments in animals where plutonium-239 as the nitrate or dioxide was injected under the skin have been conducted to simulate this exposure. From these studies it has been found that about 80% of the administered plutonium nitrate or dioxide was absorbed (Dagleetal. 1984). 

The distribution of plutonium in the liver differed between the nitrate and dioxide forms. Administration of the nitrate form to dogs resulted in diffusely distributed activity found as single tracks, while administration of the dioxide form resulted in localized activity found as "alpha stars" with radioautography (Dagle et al. 1985). 

Several components are required in the practical appHcation of nuclear reactors (1 5). The first and most vital component of a nuclear reactor is the fuel, which is usually uranium slightly enriched in uranium-235 [15117-96-1] to approximately 3%, in contrast to natural uranium which has 0.72% Less commonly, reactors are fueled with plutonium produced by neutron absorption in uranium-238 [24678-82-8]. Even more rare are reactors fueled with uranium-233 [13968-55-3] produced by neutron absorption in thorium-232 (see Nuclear reactors, nuclear fuel reserves). The chemical form of the reactor fuel typically is uranium dioxide, UO2, but uranium metal and other compounds have been used, including sulfates, siUcides, nitrates, carbides, and molten salts. 

Palladium(II) oxide, 4825 Palladium(IV) oxide, 4835 Perchloric acid, 3998 Periodic acid, 4425 Permanganic acid, 4434 Peroxodisulfuric acid, 4482 Peroxodisulfuryl difluoride, 4328 Peroxomonosulfuric acid, 4481 Peroxytrifluoroacetic acid, 0666 Platinum hexafluoride, 4371 Platinum(IV) oxide, 4836 Plutonium hexafluoride, 4372 Potassium bromate, 0255 Potassium chlorate, 4017 Potassium dichromate, 4248 Potassium iodate, 4619 Potassium nitrate, 4650 Potassium nitrite, 4649 Potassium perchlorate, 4018 Potassium periodate, 4620 Potassium permanganate, 4647 Rhenium hexafluoride, 4373 Rubidium fluoroxysulfate, 4309 Ruthenium(VIII) oxide, 4862 Selenium dioxide, 4838 Selenium dioxide, 4838 Silver permanganate, 0021 Sodium chlorate, 4039 Sodium chlorite, 4038 Sodium dichromate, 4250 Sodium iodate, 4624 Sodium nitrate, 4721 Sodium nitrite, 4720... 

Palladium(II) oxide, 4819 Palladium(IV) oxide, 4829 Perchloric acid, 3992 Periodic acid, 4419 Permanganic acid, 4428 Peroxodisulfuric acid, 4476 Peroxodisulfuryl difluoride, 4322 Peroxomonosulfuric acid, 4475 Peroxytrifluoroacetic acid, 0662 Platinum hexafluoride, 4365 Platinum(IV) oxide, 4830 Plutonium hexafluoride, 4366 Potassium bromate, 0255 Potassium chlorate, 4011 Potassium dichromate, 4242 Potassium iodate, 4614 Potassium nitrate, 4645 Potassium nitrite, 4644 Potassium perchlorate, 4012 Potassium periodate, 4615 Potassium permanganate, 4642 Rhenium hexafluoride, 4367 Rubidium fluoroxysulfate, 4303 Ruthenium(VIII) oxide, 4856 Selenium dioxide, 4832 Selenium dioxide, 4832 Silver permanganate, 0021... 

These mixed oxides can also be manufactured by mixing the uranium and nitrate solutions produeed during the reprocessing of spent nuclear fuels and converting these metal nitrate mixtures into a mixed oxide (coprecipitation). In this process the plutonium is first reoxidized, then gaseous ammonia and carbon dioxide are introduced into the aqueous nitrate mixture, whereupon ammonium uranyl-plutonyl carbonate is precipitated. This can be calcined to... 

From experimentation with supercritical fluid extraction it is known that neither plutonium nitrate or oxides nor americium nitrate or oxides are soluble in carbon dioxide without the aid of soluble complexing agents. Even with the aid of selected complexing agents plutonium extraction efficiency from spiked... 

Similar results were observed in animals given a single, acute inhalation exposure to plutonium- 238, as the more soluble dioxide or nitrate (Mewhinney et al. 1987a Park et al. 1988 Sanders 1977 Sanders et al. 1977). Studies in dogs (Park et al. 1988) and hamsters (Sanders 1977) have demonstrated that plutonium-239 was more toxic than plutonium-238. The primary cause of death in animals treated with plutonium-238 was also radiation pneumonitis. 

In on-going studies in dogs (Dagle et al. 1988 Park et al. 1988 Ragan et al. 1986) the earjiest observed biological effect was in the hematopoietic system. Aerosols of plutonium-239 or plutonium-238, as the dioxide (Park et al. 1988), or plutonium-239 nitrate (Dagle et al. 1988) were each... 

Investigations of the radiation effects of plutonium in laboratory animals indicated that translocation of plutonium from the lungs to other tissues was dependent on several factors including the solubility of the plutonium isotope or compound. Translocation to the bone occurred with plutonium citrate and with plutonium nitrate (Bair et al. 1973). By 4,000 days post-exposure, osseous atrophy and radiation osteodystrophy occurred in dogs given a single inhalation exposure to plutonium-238 dioxide (Gillett et al. 1988). The dose which resulted in these specific effects was not reported. For further discussion of this study see Section 2.2.1.8. 

Plutonium-238 administered as the soluble nitrate or as the less soluble dioxide form to dogs was absorbed from the lungs more rapidly than the corresponding forms of plutonium-239, possibly due to the lower mass of plutonium-238 (Dagle et al. 1983 Park et al. 1972) or more likely, due to the higher specific activity of plutonium-238. However, when plutonium-239 nitrate was administered to rats, it was absorbed more readily than the plutonium-238 nitrate (Morin et al. 1972). 

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