Plutonium processing deposits

A fire on May 11, 1969, occurred at the plutonium processing facility at Rocky Flats, Golden, Colorado. Subsequently, a study of the plutonium content in off-site soils was performed. The results of the study indicated that the plutonium found off-site was due, primarily, to small emissions from the facility rather than to the fire, and that a total of 0.003 kCi (9.6x10 Bq) of plutonium was deposited in soils within a 7 mile radius from the facility (Eisenbud 1987). 

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... 

Electrodeposition could be a pseudo-S-L type process, although definitive proof is lacking. The element to be ionized, uranium [16] or plutonium [17], is coelec-trodeposited with a platinum metal layer, then covered with an additional layer of platinum. The U or Pu is believed to be electrodeposited as an oxide, and platinum is electrodeposited as the metal. Hence there is thought to be a U or Pu oxide buried in the metal matrix. When this deposit is heated, after a sufficient length of time atomic cations of U or Pu begin to sublime from the surface without measurable metal oxide ions. Metal oxide ions should be readily observable if they are present in the matrix. Thermodynamic calculations indicate that the hot platinum matrix will not reduce the U and Pu oxides to the metallic state, and yet the observed species are atomic ions and not oxide molecular ions. 

Protracted DTPA therapy removes plutonium as it is liberated from cells by natural processes or solubilized by body fluids from intramuscular or lung deposits. The slowness of these processes requires DTPA administration over long periods of time to... 

Plutonium polymer. At low acidity and high temperature, plutonium forms a polymer that deposits as an insoluble solid film on the walls of process equipment. Polymer deposition plugs lines, fouls surfaces, and may result in unanticipated accumulation of a critical mass of plutonium. Figure 10.38 summarizes [M3] the results of investigations of the combinations of low acidity and high temperature that must be avoided if plutonium polymer formation is to be prevented. 

As an additional precaution, process equipment in which plutonium polymer might form should be soaked periodically in boiling, concentrated nitric acid. If plutonium is found in solution, the presence of a polymer deposit is indicated. Complete removal may require addition of 0.01 to 0.1 MHF to the hot HNO3. 

Plutonium does not undergo transformation processes in the air beyond those related to radioactive decay. Radioactive decay will be important for the short-lived isotopes with half-lives less than the average residence time in the troposphere of approximately 60 days. For example, plutonium-237 has a half-life of 46 days and undergoes electron capture to form neptunium-237 which has a half-life of 2.1x10 years (Nero 1979). Therefore, neptunium-237 may form in the stratosphere prior to deposition of plutonium-237 on the earth s surface as fallout. 

The ultimate fate of plutonium that is not excreted promptly after administration or ingestion is deposition in the bone and other mineralized tissues. Whether the mineralization is phosphate- or carbonate-based appears to be immaterial. In cartilaginous fish, plutonium is concentrated in the skeleton to a significant extent, and in fish with a bony skeleton, the plutonium concentration in the soft tissues may be less than 1 % of that in the skeleton. The uptake of actinide elements from the body fluids by bone is a slow process, because of the strong binding of plutonium by transferrin. Autoradiography of bone shows quite different patterns of deposition for plutonium and ameridum compared to the deposition of radioactive caldum. Caldum deposition is uniform, whereas actinide deposition is irregular. The lack of uniformity in the distribution of the actinides deposited in bone may be related to variations in the pH of the bone surface, or to different concentrations of dtrate ion at different locations on the bone surface. 

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