A Method for Determining the Isotope Composition of U, Pu, Am, and Cm in "Hot" Particles and Spent Nuclear Fuel

A method was proposed for determining the content of ^234-238U, ^238-242Pu, ^241-243Am, and ^242-244Cm in "hot" fuel particles and spent nuclear fuel. The method is based on high-precision measurement of the -activity in the sample and calculation of the relative contributions of individual nuclides or radionuclide groups to the total activity. Partitioning of U, Pu, Am, and Cm was carried out by ion-exchange chromatography. The contents of ²³⁴U, ²³⁶U, ²³⁸U, ²³⁸Pu, ^239+240Pu, ²⁴²Pu, ²⁴¹Am, ^242mAm, ²⁴³Am, ²⁴²Cm, and ²⁴⁴Cm in "hot" particles sampled in the Chernobyl area were reported. The applicability of the method proposed to determining the radionuclide composition of spent nuclear fuel was discussed.     

Transuranium elements in liquid radioactive wastes from the Shelter

The volume activity of ⁹⁰Sr, ¹³⁷Cs, ²³⁸Pu, ^239+240Pu, ²⁴¹Am, and ²⁴⁴Cm in water taken from unorganized water accumulations on lower marks of the Shelter was determined. Separate water accumulations are characterized by their specific radionuclide activity ratios ²³⁸Pu/^239+240Pu, ²⁴¹Am/^239+240Pu, and ²⁴⁴Cm/²⁴¹Am. The activity ratios ²⁴¹Am/^239+240Pu and ²⁴⁴Cm/^239+240Pu in the water accumulations are 5–10 times higher than in the irradiated fuel of the 4th Unit of the Chernobyl NPP and in lava-like fuel-containing materials.     

Soil Contamination with Fuel Component of Chernobyl Radioactive Fallout

Radionuclide activity ratios in the fuel component of the Chernobyl fallout are reestimated on the basis of new experimental data, and maps of the density of contamination of the Chernobyl 30-km zone with ¹⁵⁴Eu, ²³⁸Pu, ^239+240Pu, and ²⁴¹Am as of January 1, 2000 are compiled. The total radionuclide inventories in the top 30-cm horizon of the soil of the 30-km zone (minus the NPP service area, cooling pond, and radioactive waste disposal sites) on January 1, 2000 were estimated to be (Bq): ⁹⁰Sr 7.7×10^{1 4}, ¹³⁷Cs 2.8×10^{1 5}, ¹⁵⁴Eu 1.4 × 10^{1 3}, ²³⁸Pu 7.2 × 10^{1 2}, ^239+240Pu 1.5 × 10^{1 3}, and ²⁴¹Am 1.8 × 10^{1 3}, which makes up to 0.4-0.5% of the total amount of these radionuclides produced in the 4th block of CNPP. This value is lower by a factor of 3 than that generally accepted so far. The radionuclide inventories in other objects of the 30-km zone and beyond it are also estimated. The total amounts of radionuclides fallen out with fuel particles beyond the NPP service area are reestimated. The resulting value (1.5±0.5% of the total produced in the reactor by the accident time) is lower by half as compared to the previous estimates. Two thirds of these amounts are found on the Ukrainian territory.     

Estimation of the Solubility of Radioactive Aerosol Particles in Biological Liquids

The solubility of the aerosol hot particles, sampled in 1987 in the town of Pripyat, in the simulated lung fluid (SLF) (Gamble or Ringer solution) and in 0.1 M HCl was studied under static conditions. Leaching of radionuclides from the hot particles in the SLF decreases in the order ¹³⁷Cs > ⁹⁰Sr >> ^239+240Pu ²⁴¹Am, and in 0.1 M HCl, in the order ⁹⁰Sr > ²⁴¹Am >> ¹³⁷Cs > ^239+240Pu. The degree of passing into 0.1 M HCl solution for ⁹⁰Sr and ²⁴¹Am was estimated at 3.3-21 and 2.7-17%, respectively. Depending on the particle size, 0.06-2.2% of ²⁴¹Am and 0.2-1.8% of ^239+240Pu passes into the SLF within 28 days.     

Radionuclides in ground waters from observation holes in the Shelter local area

The volume activity of ³H, ⁹⁰Sr, ¹³⁷Cs, ²³⁴U, ²³⁵U, ²³⁸U, ²³⁸Pu, ^239+240Pu, and ²⁴¹Am in ground waters from observation holes 1-G-6-G in the north section of the Shelter local area of the Chernobyl Nuclear Power Plant (CNPP) was measured. The distribution of radionuclides in the suspension fractions of the ground waters was evaluated. The main contribution to the pollution of ground waters with uranium is due to natural uranium isotopes: ^234,235,238U. The activity ratios of ²³⁸Pu, ^239+240Pu, and ²⁴¹Am in ground waters are similar to those in the spent fuel of 4th CNPP block.     

Procedure for Simultaneous Determination of Uranium and Transuranium Elements in Groundwater and Liquid Radioactive Wastes from the Shelter

An ion-exchange procedure for simultaneous determination of ²³⁴U, ²³⁵U, ²³⁶U, ²³⁸U, ²³⁸Pu, ^{239 + 240}Pu, ²⁴¹Am, and ²⁴⁴Cm in groundwater and liquid radioactive wastes is described. The concentration and separation of U and Pu are performed on AV-17 anion exchanger in the chloride form from 9 M HCl. Am and Cm are separated from rare-earth elements by step-by-step elution from KU-2 cation-exchange resin in the NH ₄ ⁺ form with α-hydroxyisobutyric acid (pH 4.75). Finally, U, Pu, Am, and Cm are determined α-spectrometrically.     

Determination of Pu isotopes and 241Am in a reference fallout material using SF-ICP-MS

This paper reports on the characterisation of activities of Pu and (241)Am, and Pu isotopic composition in a reference fallout material prepared by the Meteorological Research Institute (MRI), Japan, from samples collected at 14 stations throughout Japan in 1963-1979. The acid leaching and total digestion were used to compare whether there is difference in Pu and (241)Am activities and Pu isotopic composition between these two methods. The results of activities of (239+240)Pu and (241)Pu, and Pu isotopic composition have been reported in the previous work (Sci. Total Environ. 2010, 408, 1139-1144). In this study, the (241)Am activity and (241)Am/(239+240)Pu activity ratio in the reference fallout material are reported, and the usefulness of Pu atom ratios and (241)Am/(239+240)Pu activity ratio for source identification is discussed.     

An analysis of a puncture wound case with medical intervention

A worker noted a small wound to his thumb when leaving a work site that was undergoing decontamination because of past operations with plutonium (Pu) and americium (Am). Direct surveys of the wound site confirmed the presence of contamination. The chelating agent Ca-DTPA was administered via a nebuliser within an hour after discovery of the wound. External measurements were made of the wound site and wound dressings; 24-h urinary excretion data were collected periodically and the Pu and Am urine content was determined. Zn-DTPA was administered on three occasions. The ICRP Pu systemic model was modified to consider the enhanced urinary excretion following administration of the chelating agents. The analysis indicated that the wound resulted in an initial deposition of 400 Bq 238Pu, 2240 Bq (239/240)Pu and 1060 Bq 241Am. About 70% of the initial wound activity was removed by surgical procedures and less than 1% of the wound activity was removed by chelation therapy. This paper compares the observed urinary excretion data with that indicated by a simulation of the kinetics of the transfer from the wound site and the kinetics of the chelating agent and Pu.     

Plutonium in Lake Sediments of the Taimyr Peninsula

A radiochemical study is made of five cores of lake sediments collected from the Taimyr Peninsula. For the first time quantitative data are reported on the content and vertical distribution of ^239,240Pu and ²³⁸Pu in lake sediments of this region. The plutonium content was found to range from 0.89 Bq/kg in the surface layers to 0.02 Bq/kg in the lower horizons (5-10 cm) of the sediment cores studied. The observed variations in the Pu vertical distribution are interpreted in terms of bioturbation and specific features of water catchment for the lakes studied. The 239,240Pu and ²³⁸Pu contents and the ²³⁸Pu/^239,240Pu activity ratios obtained in this work (0.02-0.10) correspond to the global level for the North hemisphere, although the region studied is not far from the principal nuclear weapons test site of the former Soviet Union in the Novaya Zemlya Archipelago.     

Distribution of <Superscript>137</Superscript>Cs, <Superscript>90</Superscript>Sr, <Superscript>239 + 240</Superscript>Pu, <Superscript>241</Superscript>Am,and <Superscript>244</Superscript>Cm among Components of Organic Matter of Soils in Near Exclusion Zone of the Chernobyl NPP

Distribution of Chernobyl-derived ¹³⁷Cs, ⁹⁰Sr, ^{239 + 240}Pu, ²⁴¹Am, and ²⁴⁴Cm among organic fractions of soddy-podzolic, sandy, soddy-meadow, and peat soils collected from the Chernobyl Exclusion Zone along the North-Western radioactive fallout track was determined. Regardless of the soil type, 80–85% of ¹³⁷Cs is tightly fixed on the mineral fraction of the soil. Depending on the soil type, 50–70% of ⁹⁰Sr and 15– 45% of ²⁴¹Am are associated with fulvic acid fractions. ²⁴¹Am and ²⁴⁴Cu are similarly distributed among the organic acid fractions. In all the soil types studied, ^{239 + 240}Pu is associated essentially with humic acid fractions. Natural ^{230, 232}Th and technogenic ^{239 + 240}Pu are similarly distributed among the organic fractions.__________Translated from Radiokhimiya, Vol. 47, No. 1, 2005, pp. 91–96.Original Russian Text Copyright © 2005 by Odintsov, Pazukhin, Sazhenyuk.     

Sorption of long-lived radionuclides onto main types of rocks of the Novaya Zemlya Archipelago

The ability of black carbonaceous siltstones and silt sandstones, lime sandstones, gray limestones, carbon–silicon carbonate schists with pyrite, and other rocks that most widely occur on the Novaya Zemlya Archipelago to sorb ¹³⁷Cs, ⁹⁰Sr, ^239+240Pu, and ²⁴¹Am was studied. The distribution coefficients K _d (cm³ g^–1) are as follows: for ^239+240Pu, 2.7 × 10³–7.7 × 10³; for 241Am, 2.5 × 10³–1.8 × 10⁴; and for ¹³⁷Cs, 1.1 × 10²–2.0 × 10³. Strontium-85(90) it not noticeably sorbed (within the measurement uncertainty) by any of the rocks studied. ^239+240Pu, ²⁴¹Am, and ¹³⁷Cs are strongly sorbed onto the rocks studied and are not noticeably desorbed from them with distilled water. The data obtained are required for predicting the migration of long-lived radionuclides generated by nuclear explosion with surface waters from test sites on the Novaya Zemlya Archipelago.     

Joint determination of 238Pu, 239, 240Pu, 241Pu, and 90Sr in soil

A procedure for determination of ²³⁸Pu, ^{239, 240}Pu, ²⁴¹Pu, and ⁹⁰Sr in soil is reported. ²⁴¹Pu was determined by liquid scintillation counting in the same Pu sample that was obtained from the initial soil sample by coprecipitation with neodymium fluoride and used for α-spectrometric measurements. ⁹⁰Sr was determined by the carbonate method after ion-exchange separation of plutonium. The ⁹⁰Sr activity in the sample was estimated using two measurements of the Cherenkov radiation of ⁹⁰Y, the first made just after separation of ⁹⁰Sr from ⁹⁰Y. This technique allows monitoring of ⁹⁰Y accumulation, excluding contributions from foreign radionuclides. Original Russian Text & V.N. Zabrodskii, Yu.I. Bondar’, A.S. Komarovskaya, V.N. Kalinin, 2006, published in Radiokhimiya, 2006, Vol. 48, No. 1, pp. 87–91.     

Formation of Unusual U,Pu, and Cf Oxide Species under Conditions of Gas Thermochromatography

Experiments were performed on the preparation of volatile oxidation products from trace amounts of plutonium and on thermochromatographic (TC) separation of these species, taking into account the previously obtained data on different behaviour of some micro- and macrocomponents in the gas phase. The volatility of products formed by thermal oxidation of traces of U and ²⁴⁹Cf with an He-O₂ (1 : 1 vol.) mixture was studied with the aim to simulate the behavior of Pu(IV) and Pu(VI) oxides. Hollow quartz columns were used. Under the experimental conditions, volatile UO₂, UO₃, and 249CfO₂ were formed; the dioxides were deposited at 450±25°C, and UO₃, at 250±25°C. The enthalpies of adsorption -H _a ⁰ of these compounds on quartz were calculated. Experimental evidence of existence in the gas phase of volatile uranic acid was obtained. The TC behavior of 238,239Pu traces was studied under conditions of thermal oxidation in an He-O₂ flow at the oxygen concentration cO ₂ varied from 50 to 10^{- 7}%. In the cO ₂ range of 50-5 × 10^{- 2}%, deposition of volatile Pu species at 460±25 and 250±25°C was observed. The identical deposition temperatures and close values of -H _a ⁰ of the products of U and Pu oxidation suggest the transfer of Pu in the form of PuO₂ and PuO₃. In the cO ₂ range from 50 to 1%, an abnormally volatile Pu species was detected, which was deposited at -105±25°C. Its -H _a ⁰, 41±6 kJ mol^{- 1}, was close to that of OsO₄. The deposition zones of ¹⁸⁵OsO₄ and of the highly volatile Pu species were superimposed. As cO ₂ decreased, the yield of the highly volatile Pu species decreased; a similar trend is also characteristic of OsO₄. This volatile Pu species was tentatively identified as Pu(VIII) oxide, PuO₄.     

Plutonium isotopes in marine sediments and some biota from the Sudanese coast of the Red Sea

Measurements of (239+240)Pu and (238)Pu were carried out on marine biota as well as on sediments from the fringing reefs area extending towards north and south (Flamingo Bay) of PortSudan harbour. The analyses were performed using radiochemical separation and alpha spectrometry. The range of the activity concentrations in marine sediments, in mBq kg(-1) dry weight, was found to be from 5.10 to 82.00 for (239+240)Pu and from 0.89 to 8.63 for (238)Pu. Corresponding activity concentrations of (239+240)Pu and (238)Pu in sediments from the harbours at PortSudan and Sawakin were 53-301 and 8.29-28.6 (PortSudan) and 163-343 and 4.7 (Sawakin), respectively. The higher values for plutonium in marine algae suggest their suitability as an indicator species for monitoring purposes. The results obtained are generally lower than those found by other studies and show that the Red Sea environment is mildly affected by plutonium contamination. Activity ratios of plutonium isotopes confirm that the existence of plutonium in the Red Sea is mainly due to atmospheric global fallout.     

Titanate Ceramics with Pyrochlore Structure as a Matrix for Immobilization of Excess Weapons-Grade Plutonium: I. Radiation Resistance

Radiation resistance of titanate ceramics of a complex cationic composition with the pyrochlore structure, containing U, Pu, Ca, Gd, and Hf, is studied from the standpoint of its use for immobilization of excess weapons-grade plutonium. To induce radiation damage of the host matrix, isomorphic incorporation of ²³⁸Pu (t _{1 / 2} = 87.7 years) at the ceramics preparation stage was used. Radiation-induced structural transformations in the ceramics were monitored by X-ray diffraction up to the radiation doses providing full amorphization of the structure. The critical damaging (amorphization) dose for the ceramics studied is estimated to be about 120 ×10^{2 3} -events m^{- 3}. Taking into account the planned concentration of incorporated ²³⁹Pu in the ceramics at a level of 10 wt %, the lower limit of amorphization time of the actual ceramics under conditions of a waste disposal site is estimated to be about 360 years.     

Physicochemical Processes Occurring in Long-Term Storage of Liquid Radioactive Waste in Deep Underground Collector Beds

Interaction under hydrothermal conditions (pressure 3 MPa; temperature 80-170°C; contact time up to 2500 h) of intermediate-level acidic waste with bed rock of the underground repository for liquid radioactive waste is studied. Transformation of rock-forming minerals under these conditions is accompanied by increasing absorption of ¹³⁷Cs, ⁹⁰Sr, ²³⁹Pu, ²⁴¹Am, and ²³⁸U.     

USTUR whole body case 0262: 33-y follow-up of PuO2 in a skin wound and associated axillary node

This whole body donation case (USTUR Registrant) involved two suspected PuO2 inhalation intakes, each indicated by a measurable Pu alpha activity in a single urine sample, followed about 1(1/2) y later by a puncture wound to the thumb while working in a Pu glovebox. The study is concerned with modelling simultaneously the biokinetics of deposition and retention in the respiratory tract and at the wound site; and the biokinetics of Pu subsequently transferred to other body organs, until the donor's death. Urine samples taken after the wound incident had readily measurable Pu alpha activity over the next 14 y, before dropping below the minimum detectable excretion rate (<0.4 mBq d(-1)). The Registrant died about 33 y after the wound intake, at the age of 71, from hepatocellular carcinoma with extensive metastases. At autopsy, all major soft tissue organs were harvested for analysis of their 238Pu, 239+240Pu and 241Am content. The amount of 239+240Pu retained at the wound site was 68 +/- 7 Bq (1 SD), measured by low-energy planar Ge spectrometry. A further 56.0 +/- 1.2 Bq was retained in an associated axillary lymph node, measured by radiochemistry. Simultaneous mathematical analysis (modelling) of all in vivo urinary excretion data, together with the measured lung, thoracic lymph node, wound, axillary lymph node and systemic tissue contents at death, yielded estimated intake amounts of 757 and 1504 Bq, respectively, for the first and second inhalation incidents, and 204 Bq for the total wound intake. The inhaled Pu material was highly insoluble, with an estimated long-term absorption rate from the lungs of 2 x 10(-5) d(-1). The Pu material deposited at the wound site was mixed: approximately 14% was rapidly absorbed, approximately 49% was absorbed at the rate of about 6 x 10(-5) d(-1), and the remainder ( approximately 37%) was absorbed extremely slowly (at the rate of about 5 x 10(-6) d(-1)). Thus, it was estimated that only approximately 40% of the Pu initially deposited in the wound had been absorbed systemically over the 33-y period until the donor's death. The biokinetic modelling also indicated that, in this individual case, some of the parameter values (rate constants) incorporated in the ICRP Publication 67 Pu model were up to a factor of 2 different from ICRP's recommended values (for reference man).     

International program to improve decay data for transactinium nuclides

To help meet an identified need for precise decay data, in 1977 the IAEA organized an international Coordinated Research Program (CRP) to measure and evaluate half-lives and γ- and α-emission probabilities for selected transactinium nuclides of importance for reactor technology. The CRP goals were (1) to determine a list of data that needed improvement, (2) to encourage new measurements, and (3) to evaluate the available data. All three phases of this work are now complete. Our participation in this effort has involved the measurement of γ-ray emission probabilities for ^232,233,235U, ^{238,239,240,241}Pu, ²²⁹Th and ²³³Pa, as well as participating in the data evaluation. The γ-emission probabilities were determined from the measurement of γ-emission rates with the goal of obtaining uncertainties of ≤ 1%. γ-measurements were made on calibrated Ge detectors. These calibrations were done by standard methods, generally involving measurements at ∼ 60 γ-ray energies from 14 to 2700 keV. The efficiency-calibration functions were assigned uncertainties ranging from 2% below 50 keV to 0.50% from 400 to 1400 keV. The determination of the decay rates of the various sources involved several techniques. The ²³⁸Pu, ²³⁹Pu and ²⁴⁰Pu samples were calibrated by gross α-emission-rate measurements at NBS. The ²³⁵U sample was taken from an NBS-calibrated spike solution. The ²⁴¹Pu and ²³³U samples were calibrated by isotope-dilution mass spectrometry based on spikes of the calibrated ²³⁹Pu, ²⁴⁰Pu and ²³⁵U materials. Some of our results are given, together with a comparison of some present and previous results.     

Half-Lives of 131-135I Nuclides

The half-lives of ^131-135I isotopes prepared by short irradiation of highly enriched ²³⁵U in an SM-3 high-flux nuclear reactor were determined by direct -ray spectrometric procedure. The measurement were carried out on automated -ray spectrometers equipped with DGDK-100V and DGDK-32-3 type semiconductor germanium detectors. For each isotope new half-lives were evaluated: 8.044±0.008 days (¹³¹I), 2.38±0.23 h (¹³²I), 20.36±0.01 h (¹³³I), 52±8 min (¹³⁴I), and 6.9±0.4 h (¹³⁵I); the results were compared with published data.