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.     

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.     

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.     

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.     

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.     

Plutonium Contamination Level and Isotopic Composition in Soils around St. Petersburg

Plutonium isotopic composition including ²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu, and ²⁴¹Pu and the Pu contamination level are determined in soils around St. Petersburg using an advanced procedure involving radiochemical separation stage followed by the -ray spectrometric and mass spectrometric determination. The Pu specific activity in surface horizons (0-25 cm) ranges from 0.2 to 0.44 Bq kg^-1. The mean ²³⁸Pu/239,240Pu activity ratio is found to be 0.033±0.007. The Pu contamination level of the surface horizon (0-25 cm) is 62±5 Bq m^-2. The ²³⁸Pu/²³⁹Pu, ²⁴⁰Pu/²³⁹Pu, and ²⁴¹Pu/²³⁹Pu isotopic ratios are (2.0±0.5)×10^-4, 0.172±0.004, and 0.003±0.002, respectively. These ratios are close to the values typical of plutonium from the global radioactive fallout due to nuclear weapons tests in the atmosphere. The effect of the Chernobyl accident and regional potential contamination sources, including the Leningrad NPP, on the Pu isotopic composition and contamination level in the soil is insignificant.     

Association of 90xSr, 137Cs, 239,240Pu, 241Am,and 244Cm with Soil Absorbing Complex in Soils Typical of the Vicinity of the Chernobyl NPP

Association of the main long-lived radionuclides ¹³⁷Cs, ⁹⁰Sr, ^239,240Pu, ²⁴¹Am, and ²⁴⁴Cm with various components of the soil absorbing complexes from soil samples collected along the western, northwestern, and northern tracks of radioactive fallout in the vicinity of the Chernobyl NPP was studied by the sequential leaching. In the samples of the sandy soil collected in the floodplain of the Pripyat river along the northwestern radioactive track, more than 85% of ⁹⁰Sr, 55% of ^239,240Pu, and 75% of ²⁴¹Am and ²⁴⁴Cm are associated with various components of the soil absorbing complex and are potentially mobile species. In the soil samples collected along the narrow western track, 80-85% of ¹³⁷Cs, ⁹⁰Sr, ^239,240Pu, ²⁴¹Am, and ²⁴⁴Cm are incorporated in hot particles. The degree of ¹³⁷Cs, ⁹⁰Sr, ^239,240Pu, ²⁴¹Am, and ²⁴⁴Cm association with different components of the soil absorbing complex is a function of the radionuclide type and physicochemical features of soil.     

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.     

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.     

Monte Carlo simulations of differential die-away instrument for determination of fissile content in spent fuel assemblies

The differential die-away (DDA) technique has been simulated by using the MCNPX code to quantify its capability of measuring the fissile content in spent fuel assemblies. For 64 different spent fuel cases of various initial enrichment, burnup and cooling time, the count rate and signal to background ratios of the DDA system were obtained, where neutron backgrounds are mainly coming from the ²⁴⁴Cm of the spent fuel. To quantify the total fissile mass of spent fuel, a concept of the effective ²³⁹Pu mass was introduced by weighing the relative contribution to the signal of ²³⁵U and ²⁴¹Pu compared to ²³⁹Pu and the calibration curves of DDA count rate vs. ²³⁹Pu_eff were obtained by using the MCNPX code. With a deuterium-tritium (DT) neutron generator of 10⁹ n/s strength, signal to background ratios of sufficient magnitude are acquired for a DDA system with the spent fuel assembly in water.     

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.     

Simultaneous determination of Np, Pu and Am in HNO3 solution by combining extraction, liquid scintillation counting, and α spectrometry

α Spectrometry is one of the most important and sensitive techniques for the assay of α-emitting nuclides, but various complicated procedures are often required for preparation of uniform thin plate source. Liquid scintillation counting (LSC) with pulse shape analysis (PSA) combining extraction is much simpler, more rapid and accurate technique, but the extraction processes are often very long. By combining extraction, LSC with PSA, and α spectrometry, we proposed a new approach to determine ²³⁷Np, ^238–240Pu and ²⁴¹Am. The new approach includes an extraction process of three steps for blind samples or of only one step for those samples without tailing interference with α spectra. Moreover, no complicated procedure is required for α plate source preparation because even non-uniform plate source is feasible for the new approach. The approach has taken advantages of high counting efficiency (nearly 100%) of LSC for α-radiation, high energy resolution of α spectrometry and high recovery yield of actinides by trialkylphosphine oxide (TRPO) extraction. The approach with one step extraction can be expected to determine ²³⁷Np, ^238–240Pu, ²⁴¹Am and ²⁴⁴Cm simultaneously.     

Determination of the content of radioactive elements in irradiated beryllium

The elemental composition of the material of beryllium blocks of SM reactor reflector in the initial state was determined by inductively coupled plasma atom emission spectrometry (ICP AES). The α-, β-, and Γ-active components of the radiation from Be irradiated to a neutron fluence of 6 × 10²² cm⁻² (E > 0.1 MeV) were determined. Radiochemical analysis revealed the presence in the irradiated Be of ⁶⁰Co, ⁵⁴Mn, ¹³⁷Cs, ¹³⁴Cs, and ⁹⁰Sr. The following α-emitters were revealed: ^238–241Pu, ²⁴¹Am,²⁴³Am, and ²⁴⁴Cm.     

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.     

Radionuclide composition of fragments of lava-like fuel-containing materials from the CNPP fourth unit

Samples of fuel-containing materials taken inside the CNPP Fourth Unit were analyzed by γ- and α-ray spectrometry. The isotope ratios for Cs, Eu, Pu, Am, and Cm were measured, and the fuel burn-up in the samples was determined. Inconsistencies in theoretical estimations on the production of all the radionuclides over ²⁴¹Am were revealed. The burn-up values determined from data on the Cs isotopes systematically differ from those determined from data on the other radionuclides. The causes of these facts are 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.     

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.     

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.     

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.