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.     

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.     

Ultratrace and isotope analysis of long-lived radionuclides by inductively coupled plasma quadrupole mass spectrometry using a direct injection high efficiency nebulizer

The direct injection high efficiency nebulizer (DIHEN) was explored for the ultrasensitive determination of long-lived radionuclides ((226)Ra, (230)Th, (237)Np, (238)U, (239)Pu, and (241)Am) and for precise isotope analysis by inductively coupled plasma mass spectrometry (ICPMS). The DIHEN was used at low solution uptake rates (1-100 μL/min) without a spray chamber. Optimal sensitivity (e.g., (238)U, 230 MHz/ppm; (230)Th, 190 MHz/ppm; and (239)Pu, 184 MHz/ppm) was achieved at low nebulizer gas flow rates (0.16 L/min), high rf power (1450 W), and low solution uptake rates (100 μL/min). The optimum parameters varied slightly for the two DIHENs tested. The detection limits of long-lived radionuclides in aqueous solutions varied from 0.012 to 0.11 ng/L. The sensitivity of the DIHEN was improved by a factor of 3 to 5 compared with that of a microconcentric nebulizer (MicroMist used with a minicyclonic spray chamber at a solution uptake rate of 85 μL/min) and a factor of 1.5 to 4 compared with that of a conventional nebulizer (cross-flow used with a Scott type spray chamber at a solution uptake rate of 1 mL/min). The precision of the DIHEN ranged from 0.5 to 1.7% RSD (N = 3) for all measurements at the 10 ng/L concentration level (～3 pg sample size). The sensitivity decreased to 10 MHz/ppm at a solution uptake rate of 1 μL/min. The precision was about 5% RSD at a sample size of 30 fg for each long-lived radionuclide by the DIHEN-ICPMS method. The oxide to atom ratios were less than 0.05 (except ThO(+)/Th(+) ) and decreased under the optimum conditions in the following sequence: ThO(+)/Th(+) > UO(+)/U(+) > NpO(+)/Np(+) > PuO(+)/Pu(+) > AmO(+)/Am(+) > RaO(+)/Ra(+). Atomic and oxide ions were used as analyte ions for ultratrace and isotope analyses of long-lived radionuclides in environmental and radioactive waste samples. The analytical methods developed were applied to the determination of long-lived radionuclides and isotope ratio measurements in different radioactive waste and environmental samples using the DIHEN in combination with quadrupole ICPMS. For instance, the (240)Pu/(239)Pu isotope ratio was measured in a radioactive waste sample at a plutonium concentration of 12 ng/L. This demonstrates a main advantage of DIHEN-ICPMS compared with α-spectrometry, which cannot be used to selectively determine (239)Pu and (240)Pu because of similar α energies (5.244 and 5.255 MeV, respectively).     

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.     

Production and characterization of plutonium dioxide particles as a quality control material for safeguards purposes

Plutonium (Pu) dioxide particles were produced from certified reference material (CRM) 136 solution (CRM 136-plutonium isotopic standard, New Brunswick Laboratory, Argonne, IL, U.S.A., 1987) using an atomizer system on December 3, 2009 after chemical separation of americium (Am) on October 27, 2009. The highest density of the size distribution of the particles obtained from 312 particles on a selected impactor stage was in the range of 0.7-0.8 μm. The flattening degree of 312 particles was also estimated. The isotopic composition of Pu and uranium (U) and the amount of Am were estimated by thermal ionization mass spectrometry (TIMS), inductively coupled plasma mass spectrometry (ICPMS), and α-spectrometry. Within uncertainties the isotopic composition of the produced particles is in agreement with the expected values, which were derived from the decay correction of the Pu isotopes in the CRM 136. The elemental ratio of Am to Pu in the produced particles was determined on the 317th and 674th day after Am separation, and the residual amount of Am in the solution was estimated. The analytical results of single particles by micro-Raman-scanning electron microscopy (SEM)-energy-dispersive X-ray spectrometry (EDX) indicate that the produced particles are Pu dioxide. Our initial attempts to measure the density of two single particles gave results with a spread value accompanied by a large uncertainty.     

惯性约束聚变／裂变混合堆核能系统的概念研究

在惯性约束聚变尚未达到能量得失相当的条件下，以惯性约束聚变产生的中子作为驱动源，￣（２３８）Ｕ或￣（２３９）Ｐｕ与￣（２３８）Ｕ的混合物作为包层核燃料，进行了聚变裂变混合放能系统的概念研究。提出了以少量￣（２３９）Ｐｕ作为“助燃剂”，用以提高包层能量倍增的概念。￣（２３９）Ｐｕ的引入提高了包层的通量水平，加速了￣（２３８）Ｕ的造钚和钚的燃烧过程，实现了消耗￣（２３８）Ｕ释放能量而不消耗或很少消耗￣（２３９）Ｐｕ，并使包层能量倍增达到３０以上，从而为惯性约束聚变的早期应用和以￣（２３８）Ｕ为裂变能源燃料的持续发展提出了一条可能的途径。     

高放废物中^238Pu,^240Pu,^242Pu在聚变—裂变混合堆内的嬗变研究

从中子学角度研究了高放废物中２３８Ｐｕ、２４０Ｐｕ、２４２Ｐｕ在聚变一裂变混合堆内擅变的可行性。选取２３３Ｕ做中子增殖剂，对四个不同燃料组分的快谱包层进行了设计，利用输运一燃耗程序ＢＩＤＥＡＹ对所选方案进行了计算分析，结果表明：用２３３Ｕ做中子增殖剂，在聚变一裂变混合堆快谱包层内擅变２３８Ｐｕ、２４０Ｐｕ、２４２Ｐｕ是安全可行的。     

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.     

Determination of pu isotopes in seawater by an on-line sequential injection technique with sector field inductively coupled plasma mass spectrometry

An on-line sequential injection (SI) system combined with sector field inductively coupled plasma mass spectrometry was developed for the determination of ultratrace level 239Pu and 240Pu in seawater. The potential of this method is the substantial reduction of a sample volume and rapidity in the determination of Pu isotopes. A chemical purification and preconcentration of Pu isotopes were accomplished by the on-line SI system with two microcolumns of solid-phase extraction resins, Sr-Spec and TEVA-Spec. The MCN-6000 microconcentric nebulizer was used as a sample introduction system because of low interference effect and good sample utilization. With this method, it was possible to analyze ultratrace levels of Pu isotopes in only 5 L of surface seawater with an analysis speed of 4 h/sample. The precision of the measurement for the 239Pu and 240Pu was less than 3.4 (n = 7) and 5% (n = 7) for 5 L of seawater. The detection limits for 239Pu and 240Pu were 0.64 (1.5 microBq/mL) and 0.19 fg/mL (1.6 microBq/mL), respectively. The accuracy of this method was verified by using the reference seawater (IAEA-381) as well as by the comparison with the a-spectrometry.     

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.     

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.     

Separation of U,Pu, and Am recovered from mixed oxide (MOX) fuel by countercurrent chromatography

The separation of U, Pu, and Am recovered from MOX fuel with the adduct of HNO₃ with N,N′-dimethyl-N,N′-dioctylhexylethoxymalonamide by countercurrent chromatography (CCC) was studied. Solutions of N,N′-dimethyl-N,N′-dibutyldodecylethoxymalonamide in dodecane were used as stationary phase. The separation of U, Pu, and Am was carried in both isocratic and stepwise elution modes. The better separation of actinides and their higher radionuclidic purity are reached with stepwise elution. The first eluate fraction contained only Am (100%). The second eluate fraction contained U (100%) and Pu (0.7%). The third eluate fraction contained 99.3% of Pu.     

Ultratrace uranium fingerprinting with isotope selective laser ionization spectrometry

Uranium isotope ratios can provide source information for tracking uranium contamination in a variety of fields, ranging from occupational bioassay to monitoring aftereffects of nuclear accidents. We describe the development of isotope selective laser ionization spectrometry for ultratrace measurement of the minor isotopes (234)U, (235)U, and (236)U with respect to (238)U. The inherent isotopic selectivity of three-step excitation with single-mode continuous wave lasers results in measurement of the minor isotopes at relative abundances below 1 ppm and is not limited by isobaric interferences such as (235)UH(+) during measurement of (236)U. This relative abundance limit is attained without mass spectrometric analysis of the laser-created ions. Uranyl nitrate standards from an international blind comparison were used to test analytical performance for different isotopic compositions and with quantities ranging from 11 ng to 10 microg total uranium. Isotopic ratio determination was demonstrated over a linear dynamic range of 7 orders of magnitude with a few percent relative precision and detection limits below 500 fg for the minor isotopes.     

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 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.     

Speciation of radionuclides in colloidal matter of underground waters taken from observation wells in the zone of impact of Lake Karachai

The strength of actinide bonding with colloidal matter of groundwaters from the Lake Karachai contamination area was studied by selective leaching. An α-track analysis showed that the microdistribution of α-emitting radionuclides in the colloidal matter is uniform. Analysis of fission tracks confirms the presence of ²³⁹Pu and ²⁴¹Am in the colloidal material. In the colloidal matter of groundwaters taken from three wells and differing in the chemical composition, radionuclides occur in forms differing in the solubility. U and Np in the colloidal material are associated only with readily soluble and mobile groups of compounds and are not detected in the difficultly soluble residue. Pu and Am, on the contrary, occur in the colloidal material of groundwaters mainly in difficultly soluble forms. Am is bound to a greater extent with surface organometallic complexes. Pu is detected mainly in the fraction of amorphous oxides.     

Development of Decay Energy Spectroscopy for Radionuclide Analysis Using Cryogenic 4π Measurements

We report the recent progress in the development of decay energy spectroscopy for radionuclide analysis using a metallic magnetic calorimeter. In the present analysis, sample radionuclides were completely enclosed by a 4π steradian absorber. The use of a 4π absorber composed of gold foil guarantees that the total energy associated with radioactive decay is converted into thermal energy in the absorber. A paramagnetic temperature sensor was attached to the absorber to accurately measure the temperature change due to radioactive decay. The plutonium isotopes ²³⁸Pu, ²³⁹Pu, and ²⁴⁰Pu were readily identified in the decay energy spectrum because each isotope creates a single peak at its characteristic Q value. Two clear peaks were observed for ²³⁹Pu and ²⁴⁰Pu, and a 6.3?keV FWHM was obtained. The energy resolution of the method was affected by the low-energy tail of the spectrum at the left-hand side of the peaks. A 4.1?keV FWHM of a Gaussian fit was obtained for the right-hand side of the peak. Slow heat release to the absorber due to heat flow mechanisms is discussed to explain the low-energy tailing effect.     

Development of an automatic method for americium and plutonium separation and preconcentration using an multisyringe flow injection analysis-multipumping flow system

A new procedure for automatic separation and preconcentration of 241Am and 239+240Pu from interfering matrixes using transuranide (TRU)-resin is proposed. Combination of the multisyringe flow injection analysis and multipumping flow system techniques with the TRU-resin allows carrying out the sampling treatment and separation in a short time using large sample volumes. Americium is eluted from the column with 4 mol L(-1) hydrochloric acid, and then plutonium is separated via on-column Pu(IV) reduction to Pu(III) with titanium(III) chloride. The corresponding alpha activities are measured off-line, with a relative standard deviation of 3% and a lower limit of detection of 0.004 Bq mL(-1), by using a multiplanchet low-background proportional counter.