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Determination of plutonium-239 + plutonium-240 and plutonium-241 in environmental samples using low-level liquid scintillation spectrometry.

A radiochemical method for the simultaneous determination of 239Pu + 240Pu and 241Pu in environmental samples has been developed. In the course of the analysis a 236Pu tracer was used for estimating the chemical yield of plutonium isotopes. After suitable pre-treatment of the sample, the plutonium nuclides in solution were coprecipitated with iron(III) hydroxide and calcium oxalate and isolated further from impurities and interfering radionuclides by means of anion-exchange chromatography. Plutonium isotopes in the eluate (NH4I-HCI) were converted into nitrate form and then extracted with 20 ml of 5% bis(2-ethylhexyl) hydrogen phosphate extractive cocktail. The final organic solution was measured spectrometrically using an ultra-low-level liquid scintillation spectrometer, Quantulus (LKB, 1220 Wallac). The chemical yields of plutonium range from 25 to 50% for 100 I of sea-water and 30 to 60% for 40 g of dried soil sample. The counting efficiencies are nearly 100% for 239Pu + 240Pu and 48.8% for 241Pu, respectively. The detection limits were estimated to be 0.20 mBq for 239Pu + 240Pu and 2.2 mBq for 241Pu, respectively. The proposed procedure has been tested for the simultaneous determination of 239Pu + 240Pu and 241Pu in sea-water (Irish Sea, North Sea) and soils (Cumbrian coast, UK; Byelorussia, USSR).

Europe↗

Plutonium in Finnish Lapps--an estimate of the gastrointestinal absorption of plutonium by man based on a comparison of the plutonium content of Lapps and southern Finns.

The plutonium body burden of five male Lapps was determined through radiochemical analysis of bone, liver and lung samples, and compared with the body burden of male southern Finns. Tissue burdens of plutonium were found equal in the Lapps and southern Finns. The mean content of 239,240Pu in bone (ribs), liver and lung of the Lapps was 0.045, 0.42 and 0.033 pCi/kg wet wt (1.7, 15.5, 1.2 mBq/kg), respectively. The average body burden of plutonium in the Lapps was 1.1 pCi (41 mBq). The 137Cs, 90Sr, 210Po and 210Pb contents of tissue samples were analyzed to estimate the amount of reindeer tissue consumed by the Lapps studied. The 137Cs content in liver and lung of the Lapps was, on the average, 2160 and 1180 pCi/kg wet wt (79.9 and 43.7 Bq/kg), respectively. In southern Finns both liver and lung content of 137Cs was less than 50 pCi wet wt (less than 1.9 Bq/kg). For 210Po, the liver and lung values were 86.2 and 8.2 pCi/kg wet wt (3.2 and 0.3 Bq/kg) in the Lapps and 15.4 and 3.9 pCi/kg wet wt (0.6 and 0.1 Bq/kg) in southern Finns, respectively. The inhalation intake of 239,240Pu of male Lapps during the period 1954-1978 was about 13 pCi (0.48 Bq) and that of southern Finns about 18 pCi (0.67 Bq). The estimated values for dietary intake were 535 pCi (19.7 Bq) and 36 pCi (1.3 Bq), respectively. The fractional absorption factor of 239,240Pu from the GI tract of man was estimated to be (8-9) X 10(-4), which is somewhat higher than that presently suggested by the ICRP for soluble plutonium compounds (1 X 10(-4)).

Adult↗

Plutonium in bone: a high resolution autoradiographic study using plutonium-241.

Plutonium-241 citrate solution at pH 6-5 was injected intravenously into hamsters and an adult rabbit at a dose of 10 kBq g-1 (260 nCi g-1). The hamsters were killed serially at 15 min, 2 hours, 1 day, 10 days, 1 month and 6 months after injection and the rabbit at 1 week. Their knee-joints or femora were examined for plutonium-241 by autoradiography. Few differences were found between the pattern of plutonium distribution in the hamsters and the rabbit. The results showed that although plutonium is initially distributed on bone surfaces, at long periods after injection it becomes deposited throughout the bone matrix. Plutonium uptake by cells in resorbing areas of periosteum, in active osteoblasts, and in chondrocytes in regions of cartilage mineralization was rapid. Plutonium concentrated more slowly on the resting bone surfaces and at sites of low metabolic activity. In addition, some unlabelled sections of skeletal tissues were immersed in a plutonium-241 citrate solution. When autoradiographed, it was found that plutonium was bound by cell nuclei, tooth enamel matrix, dentine, predentine and bone matrix. Plutonium binding to cartilage matrix was weak. The results are discussed with reference to the literature, and a model is proposed to explain the distribution pattern and fate of plutonium deposits in bone.

Animals↗

The calculation of annual limits of intake for plutonium-239 in man using a bone model which allows for plutonium burial and recycling.

Values of the annual limit of intake (ALI) for plutonium-239 in man have been calculated using committed dose equivalent limits as recommended by ICRP in Publication 26. The calculations were made using a multicompartment bone model which allows for plutonium burial and recycling in the skeleton. In one skeletal compartment, the growing surfaces of cortical bone, it is assumed that plutonium deposits are retained and are not subject to resorption or recycling. In the trabecular bone compartment plutonium is taken to be resorbed with either subsequent redeposition onto bone surfaces or retention in the bone marrow. ALIs for plutonium-239 have been calculated assuming a range of rates of bone accretion (0-32 micron yr-1), different amounts of plutonium retained in the marrow (0-60%) and a 20%, 45% or 70% deposition of plutonium in the skeleton from the blood. The calculations made using this bone model suggest that 750 Bq (20 nCi) is an appropriate ALI for the inhalation of class W and class Y plutonium compounds and that 830 kBq and 5 MBq (23 muCi and 136 muCi) are the appropriate ALIs for the ingestion of soluble and insoluble forms of plutonium respectively.

Administration, Oral↗

Translocation of plutonium from rat and monkey lung after inhalation of industrial plutonium oxide and mixed uranium and plutonium oxide.

This study was designed to compare the translocation from lung of the Pu contained in the pure and mixed industrial oxides PuO2 and (U,Pu)O2. The latter had a Pu content of 20% w/w. For this purpose, young adult male rats and male and female baboons were exposed to a single inhalation of these oxides. Two baboons were exposed to the reference PuO2, i.e. 239PuO2. Rats were killed under anaesthesia 1, 15, 30, 90 and 180 days after exposure, and baboons, also under anaesthesia, 1 year thereafter. The results indicate that lung retention of Pu was independent of the oxide inhaled, but was smaller in rat (12-15% of the initial pulmonary burden, 6 months after exposure) than in baboon (56-80% of this burden, 1 year after exposure). In rat, Pu translocation kinetics were similar for the two industrial oxides, but as from day 15 after inhalation until 6 months thereafter, measurement of Pu deposits in the liver and skeleton showed that translocation of Pu from the mixed oxide was 2-3 times greater than that from the industrial Pu oxide. In baboon, the largest amounts of Pu were retained in the lung and thoracic lymph nodes for the three oxides inhaled. Pu translocation to the liver, skeleton and kidneys, and also urinary Pu excretion, were greater after inhalation of the mixed oxide than after inhalation of the industrial and reference Pu oxides. Nevertheless, the amount of mixed oxide Pu translocated to these sites and excreted in urine remained under 3% of the initial pulmonary burden.

Administration, Inhalation↗

Mortality among plutonium and other radiation workers at a plutonium weapons facility.

Mortality among 5,413 white males who were employed for at least two years at a plutonium weapons facility was investigated to measure risks from exposures to low levels of plutonium and external radiation. When compared with US death rates, fewer deaths than expected were found for all causes of death, all cancers, and lung cancer. No bone cancer was observed. An excess of brain tumors was found for the cohort in general. Elevated rate ratios for all causes of death and all lymphopoietic neoplasms were found when employees with plutonium body burdens greater than or equal to 2 nCi were compared with those with body burdens less than 2 nCi, while accounting for age, calendar period, and induction time. Increased rate ratios were also found for esophageal, stomach, colon, and prostate cancers, and for lymphosarcomas and reticulum cell sarcomas. No elevated rate ratios were noted for bone and liver cancers. When employees with cumulative exposures greater than or equal to 1 rem were compared with those with exposures less than 1 rem, elevated rate ratios were found for myeloid leukemia, lymphosarcoma and reticulum cell sarcoma, liver neoplasms, and unspecified brain tumors. No overall dose-response relationships were found for plutonium or external radiation exposures. Standardized rate ratios increased, however, as plutonium body burden levels increased for all causes, all cancers, and digestive cancers at five years induction time. Standardized rate ratios also increased as external radiation exposure categories increased for all lymphopoietic cancers and unspecified brain tumors for a two-year induction period. With the exception of analyses of combined categories of death, and perhaps of lung cancer, confidence limits were wide, indicating limited precision. Nevertheless, these findings suggest that increased risks for several types of cancers cannot be ruled out at this time for individuals with plutonium body burdens of greater than or equal to 2 nCi. Plutonium-burdened individuals should continue to be studied in future years.

Air Pollutants, Radioactive↗

Recent trends of plutonium fallout observed in Japan: plutonium as a proxy for desertification.

Plutonium in monthly deposition samples collected in Tsukuba (the Meteorological Research Institute), Japan from 1990 to end of 2001 is reported, together with monthly plutonium deposition in Nagasaki and Yonaguni in 2000. The annual deposition of (239,240)Pu during the period from 1990 to 2001 shows no systematic interannual variation. However, monthly (239,240)Pu depositions show a typical seasonal variation with a maximum in spring season (March to April), which corresponds to seasonal cycle of soil dusts originating from the East Asian arid area. Plutonium isotopic ratios in the deposition samples suggest that significant amounts of the recent (239,240)Pu deposition observed in Japan are attributed to the resuspension of plutonium-bearing surface soil particles; resuspended plutonium originates from the East Asian arid areas. The recent increased tendency of (239,240)Pu content in residues in deposition samples may reflect desertification in the East Asian continent.

Asia↗

Distribution, retention and dosimetry of plutonium and americium in the rat, dog and monkey after inhalation of an industrial-mixed uranium and plutonium oxide aerosol.

This study provides information on patterns of radiation dose in laboratory animals after inhalation exposure to an aerosol of one form of mixed uranium and plutonium oxide. The aerosol contained a mixture of UO2 and 750 degrees C heat-treated PuO2 obtained from the ball milling operation in a mixed-oxide fuel fabrication process. Americium-241 from the decay of 241Pu was also present in the PuO2 matrix. Fischer-344 rats, Beagle dogs, and Cynomolgus and Rhesus monkeys inhaled aerosols re-generated from dry mixed oxide powders with particle size distribution characteristics similar to those observed in samples collected at the industrial site. Clearance from the lung and distribution in other tissues of the plutonium from this UO2 + PuO2 admixture was similar to what has been observed for PuO2 from laboratory-produced aerosols. The UO2-PuO2 aerosol was relatively insoluble in the lungs of all species. Monkeys and rats cleared plutonium and americium from their lungs faster than dogs. Very little plutonium or americium translocated within the first 2 yr after exposure to tissues other than tracheobronchial lymph nodes. The greater accumulation of plutonium and americium in the tracheobronchial lymph nodes of dogs as compared to monkeys and rats combined with the more rapid initial clearance of these radionuclides from the lungs of rats and monkeys suggests that errors could result from using data from a single animal species to estimate risk to humans from inhalation of these industrial aerosols.

Aerosols↗

Fifty years of plutonium exposure to the Manhattan Project plutonium workers: an update.

Twenty-six white male workers who did the original plutonium research and development work at Los Alamos have been examined periodically over the past 50 y to identify possible health effects from internal plutonium depositions. Their effective doses range from 0.1 to 7.2 Sv with a median value of 1.25 Sv. As of the end of 1994, 7 individuals have died compared with an expected 16 deaths based on mortality rates of U.S. white males in the general population. The standardized mortality ratio (SMR) is 0.43. When compared with 876 unexposed Los Alamos workers of the same period, the plutonium worker's mortality rate was also not elevated (SMR = 0.77). The 19 living persons have diseases and physical changes characteristic of a male population with a median age of 72 y (range = 69 to 86 y). Eight of the twenty-six workers have been diagnosed as having one or more cancers, which is within the expected range. The underlying cause of death in three of the seven deceased persons was from cancer, namely cancer of prostate, lung, and bone. Mortality from all cancers was not statistically elevated. The effective doses from plutonium to these individuals are compared with current radiation protection guidelines.

Aged↗

Sector field inductively coupled plasma mass spectrometry, another tool for plutonium isotopes and plutonium isotope ratios determination in environmental matrices.

The transfer of radio nuclides into the different compartments of the environment are widely studied and leads to the elaboration of transfer models in order to evaluate potential impact onto the environment and humans. Accurate experimental data are needed to validate these models for all types of matrices (air, water, sediments, soils, biota and food...). Among these radionuclides, 238Pu, 239Pu, 240Pu and 241Pu, are often mentioned. They have been released into the environment by nuclear weapon tests, nuclear facilities, reactors or satellite accidents. These different sources have different 240Pu/239Pu ratios and therefore this ratio is used to provide information on the source of contamination into the environment. The most conventional analytical tools used for plutonium isotope determination are liquid scintillation and alpha spectrometry, and thermal ionisation mass spectrometry (TIMS) is still considered as the primary method for determination of plutonium isotope ratios. During the last decade, mass spectrometers equipped with plasma ion sources and sector field analysers were developed and can offer now another alternative method for the accurate determination of isotope content and ratios of long-lived radionuclides in environmental samples. This paper presents and discusses the results obtained for 239Pu, 240Pu and 241Pu content and isotope ratios by sector field ICP-MS in different environmental matrices.

Environmental Monitoring↗

Sequestered plutonium: [Pu(IV){5LIO(Me-3,2-HOPO)}2]--the first structurally characterized plutonium hydroxypyridonate complex.

The first single-crystal X-ray diffraction analysis of a hydroxypyridonate plutonium(IV) complex is presented, that of the tetradentate ligand 5LIO(Me-3,2-HOPO) with Pu(IV). The [Pu(IV){5LIO(Me-3,2-HOPO)}(2)] complex crystallizes in the space group Pna2(1) with the asymmetric unit cell containing two unique eight-coordinate plutonium complexes and one perchlorate anion. According to shape measure analysis, the geometry of both Pu centers is closest to a bicapped trigonal prism (C(2v) symmetry, for Pu 1: S(C(2v))=13.48 degrees , S(D(4d))=15.43 degrees , S(D(4d))=16.10 degrees ). The average bond length for the Pu--O(phenolic) is 2.31(4) A, whereas the Pu--O(amide) distances are slightly longer, averaging 2.40(2) A. The preparative chemistry of this compound and the implications of the structure are discussed.

Journal Article↗

Plutonium partitioning to colloidal and particulate matter in an acidic, sandy sediment: implications for remediation alternatives and plutonium migration.

Plutonium partitioning within a bulk, freshwater sediment and to specific size fractions of the sediment was determined. Fission track analysis was used to observe the spatial heterogeneity of fissile isotopes of Pu and U in the sediment. For the bulk sediment, a six-step sequential extraction scheme was used to elucidate Pu partitioning. Although no direct Pu speciation is obtained from our sequential extraction scheme, this study demonstrates that the partitioning information obtained is more useful for evaluating ex-situ remediation treatments than information obtained from complete digestion and analysis of the bulk sediment. The majority of 238Pu and 239 + 240Pu appear to be partitioned in the oxidizable fraction, suggesting that Pu is primarily associated with organic matter in the bulk sediment or may exist as a discrete, oxidizable phase. By varying filter pore size used to separate the sequential extraction leachate solution from the remaining solid phase, a fraction of 238Pu associated with colloidal material was observed, and chemical evidence suggests that this colloidal material is relatively refractory. Pu partitioning to various size fractions of the bulk sediment was also compared to the percent organic carbon present in those size fractions. Interestingly, little correlation was observed between the percentage of organic carbon and concentrations of Pu isotopes in the various size fractions, although differences were observed in the distributions of 238Pu versus 239 + 240Pu in the size fractions. These results suggest that other sediment phases may also be important for Pu partitioning. Our observations are described in the context of feasibility of various remediation options.

Colloids↗