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.     

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.     

Speciation of artificial radionuclides 60Co, 137Cs, 152Eu, and 241Am in bottom sediments of the Yenisei river

The speciation of artificial radionuclides ⁶⁰Co, ¹³⁷Cs, ¹⁵²Eu, and ²⁴¹Am in surface layers of bottom sediments of the Yenisei river, collected within the near zone of impact of the Mining and Chemical Combine (Rosatom), was studied. In these samples the radionuclides ⁶⁰Co, ¹⁵²Eu, and ²⁴¹Am are mainly associated with fractions of humic and fulvic acids. The fraction of ¹⁵²Eu associated with nonsilicate iron is approximately 92%. The migration capability of radionuclides collected near the Atamanovo settlement decreases in the order ¹⁵²Eu > ²⁴¹Am > ⁶⁰Co > ¹³⁷Cs. For samples collected near Bol’shoi Balchug settlement, this order is as follows: ¹⁵²Eu ≈ ²⁴¹Am > ⁶⁰Co > ¹³⁷Cs. The presence of radionuclide-bearing micro-particles in bottom sediments considerably complicates the distribution of radionuclides, in particular, of ²⁴¹Am and ¹³⁷Cs, among migration forms.     

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.     

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.     

Coprecipitation of microamounts of radionuclides on chitosans of various molecular weights in solutions

Coprecipitation of ²³³U, ²³⁹Pu, ²⁴¹Am, ¹⁵²Eu, ⁹⁰Sr, ⁹⁰Y, and ⁶⁰Co on chitosans of various molecular weights (MW) was studied. Low-molecular-weight chitosan (LMWC) with MW of 5 kDa (5 × 10³ g mol⁻¹) proved to be a more effective coprecipitant than high-molecular-weight chitosan (HMWC) with MW of 700 kDa (7 × 10⁵ g mol⁻¹). With HMWC, the degree of coprecipitation (α) was 80% for ¹⁵²Eu and ⁹⁰Y, 99% for ²³³U and ²⁴¹Am, and 85% for ²³⁹Pu. For ⁶⁰Co, α monotonically increased with an increase in the chitosan concentration in solution and reached 40% at [HMWC] = 5 g l⁻¹. For ⁹⁰Sr, α did not exceed 3% in the entire examined range of chitosan concentrations. With LMWC, the α values for An, ¹⁵²Eu, and ⁹⁰Y differed insignificantly (92–99%). For ⁶⁰Co and ⁹⁰Sr, α increased to 40% in the range of chitosan concentrations from 0 to 1 g l⁻¹. The presence of inorganic salts in solution considerably decreases α of UO₂²⁺ with chitosans but does not noticeably affect the behavior of Am, Pu, and Eu. The effect of salts on the efficiency of ²³³UO^2/2+ coprecipitation on HMWC decreases in the order Na₂SO₄ > NaCl > Na₂CO₃ > NaNO₃ > Na₃PO₄. Based on the results obtained, a procedure suitable for expedition conditions was developed for preconcentration of Pu from seawater on chitosan, with simultaneous separation of Pu from U, for radioecological monitoring of natural waters. The specific activity of Pu in samples of near-bottom seawater of gulfs of the Novaya Zemlya archipelago was (150–170) ± 20 mBq m⁻³. The results are well consistent with the published data.     

The performance of a special geometry bismuth germanate escape suppressed spectrometer

The performance of a special geometry bismuth germanate escape suppressed spectrometer has been investigated. The spectrometer comprises a bismuth germanate suppression shield, a germanium detector and a bismuth germanate “catcher” detector positioned behind the germanium detector. The germanium detector is irradiated through a hole in one side of the suppression shield. The performance of the system has been measured with ²⁴¹Am, ¹³⁷Cs and ⁶⁰Co gamma-ray sources.     

Diffusion of some critical radionuclides in mineral-like ceramic materials

The diffusion coefficients and activation energy of diffusion of ²²Na, ⁹⁰Sr, ¹⁵²Eu, and ²⁴¹Am radionuclides in zirconolite ceramics prepared by cold crucible induction melting (CCIM), of ²²Na, ⁹⁰Sr, ¹³⁷Cs, ¹⁵²Eu, and ²⁴¹Am in Synroc-C ceramics prepared by hot pressing (HP) and CCIM, and of ²²Na and ¹⁵²Eu in the ceramic from the Lawrence Livermore National Laboratory (the United States), synthesized by cold pressing (CP) and sintering, and also the diffusion mobility of ⁹⁰Sr, ¹³⁷Cs, and ²⁴¹Am in the chromium-containing sphene glass ceramic prepared by CCIM were determined by the method of integral residual activity. In the temperature interval 573–923 K, the ²²Na radionuclide is the most mobile and ²⁴¹Am is the least mobile. The differences between the diffusion coefficients reach 4–5 orders of magnitude. The diffusion coefficients of the examined radionuclides in the ceramic depend both on the preparation procedure (HP, CP, or CCIM) and on the initial charge components when the same procedure is used for preparing the ceramic. Negative values of the activation entropy of the diffusion of ²²Na, ⁹⁰Sr, ¹⁵²Eu, and ²⁴¹Am in ceramics suggest that the mass transfer of radionuclides in them occurs not by the vacancy mechanism but by the interstitial mechanism and, probably, in part along the facilitated migration pathways (grain boundaries, pore surfaces, micro- and macrocracks).     

Thermal expansion of NZP-family alkali-metal (Na, K) zirconium phosphates

The thermal expansion of the A _x Zr_2.25-0.25x(PO₄)₃ phosphates with A = Na(x = 0.5,1.0,2.0,3.0,4.0, 5.0) and K(x = 1.0, 3.0, 5.0), crystallizing in structures of the NaZr₂(PO₄)₃ type (sp. gr.R3c or C2/c), was studied by high-temperature x-ray powder diffraction in the range 20–700‡C. The lattice parametersa and c and thea- andc-axis thermal expansion coefficients (α_a and α_c) were determined. The thermal expansion of the phosphates was found to be highly anisotropic (α_a < 0, α_c > 0). The strongest anisotropy was found in NaZr₂(PO₄)₃ (α_a = -4.89 x 10^-6 K^-1, α_c = 22.02 x 10^-6 K^-1), KZr₂(PO₄)₃ (α_a =-5.30 x 10^-6 K^-1, α_c = 5.41 x 10^-6 K^-1), and Na₅Zr(PO₄)₃ (α_a = -5.82 x 10^-6 K^-1, α_c = 20.73 x 10^-6 K^-1). K₅Zr(PO₄)₃ exhibited the smallest thermal expansion and weak anisotropy (α_a = -2.14 x 10^-6 K^-1, α_c = 2.65 x 10^-6 K^-1). The effects of M(l) and M(2) site occupancies on α_a, α_c,a, and c were assessed. The relative magnitudes of crystal-chemical and thermal expansion in the Na and K compounds were analyzed.     

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.     

Diffusion of americium in aqueous solutions

The diffusion coefficients of Am in lanthanum and barium nitrate solutions of various concentrations in the pH range 2–12 at 25°C were determined. The secondary hydrate shell of the ion does not participate in the Am migration in the solution. The Am hydrolysis is stepwise and occurs via intermediate species according to the scheme Am(H₂O)₉³⁺ → Am(OH)(H₂O)₉²⁺ or Am(OH)(H₂O)₈²⁺ → Am(OH)₂(H₂O)₅⁺ → Am(OH)₃. The diffusion coefficients of Am at infinite dilution were determined: D ₀ = 6.2 × 10⁻⁶ cm² s⁻¹ at pH 2 and D ₀ = 6.15 × 10⁻⁶ cm² s⁻¹ at pH 3. The limiting concentrations at which the Onsager law is still observed are 0.1 g-equiv l⁻¹ at pH 3 and 0.3 g-equiv l⁻¹ at pH 2.     

Photoluminescence and Raman studies in swift heavy ion irradiated polycrystalline aluminum oxide

Polycrystalline aluminum oxide is synthesized by combustion technique and XRD studies of the sample revealed the α-phase. The synthesized sample is irradiated with 120 MeV swift Au⁹⁺ ions for the fluence in the range from 1 × 10¹¹ to 1 × 10¹³ ions cm⁻². A broad photoluminescence (PL) emission with peak at ∼ 447 nm and two sharp emissions with peak at ∼ 679 and ∼ 695 nm are observed in pristine when sample was excited with 326 nm. However, in the irradiated samples the PL intensity at ∼ 447, 679 and 695 nm decreases with increase in ion fluence. The α-Al₂O₃ gives rise to seven Raman modes with Raman intensity with peaks at ∼ 253, 396, 417, 546, 630, 842, 867 cm⁻¹ observed in pristine. The intensity of these modes decreases with increase in ion fluence. However, the Raman modes observed at lower fluences are found to disappear at higher fluence.     

Impact of various irradiation photon energies and gamma doses on the optical properties of ZnSe nanostructure thin film

ZnSe thin films were prepared by thermal evaporation technique under high vacuum (10⁻⁶ Torr) at 300 K and different film thickness. The structure of thin films was measured using grazing incident in-plane X-ray diffraction (GIIXD) and shows single phase zinc blende structure. The particle sizes of the deposited films were estimated for low film thickness by TEM and high film thickness by GIIXD. The particle size of ZnSe films was decreased from ~8.53 to 3.93 nm as film thickness lowered from 200 to 20 nm which ensures the nanocrystalline structure. The optical transmission (T) and reflection (R) in the wavelength range 190–2,500 nm for irradiated and unirradiated ZnSe thin films under investigation were measured. The effect of irradiation of different energies in range (0.1–1.25 MeV) from X-ray, ¹³⁷Cs and ⁶⁰Co irradiation sources were studied for ZnSe thin films of 100 and 200 nm thicknesses. The dependence of the absorption spectra and refractive index were investigated for different energies irradiation sources. The ZnSe films show direct allowed interband transition. The effect of particle size of nanocrystalline ZnSe thin films for unirradiated and irradiated by gamma (γ) doses from ¹³⁷Cs on the optical properties was studied. Both the optical energy bandwidth and absorption coefficient (α) were found to be (γ) dose dependent.     

Production and radiochemical separation of no-carrier-added <Superscript>88</Superscript>Y by liquid-liquid extraction

A method was suggested for the cyclotron production of ⁸⁸Y with liquid-liquid extraction. The sedimented ^natSrCO₃ target was irradiated with 18-MeV protons at current of 20 μA for 10 h. The ⁸⁸Y yields of about 1.326 MBq μA⁻¹ h⁻¹ were experimentally obtained. Solvent extraction of no-carrier-added ⁸⁸Y from irradiated strontium carbonate target in the hydrochloric acid solution was studied using di(2-ethylhexyl) hydrogen phosphate (HDEHP). The optimum separation was achieved in the system n-hexane/10% HDEHP-0.1 M HCl. Yttrium radionuclides were recovered from the HDEHP phase by stripping with 60 ml of 9 M HC1. Also, excitation functions of the proton, deuteron, and α-particle induced reactions of ⁸⁹Y, ⁸⁸Sr, ^natSr, and natRb were determined using computer codes and compared to the existing data.     

Operation of a TES microcalorimeter cooled by a compact liquid-helium-free He-He dilution refrigerator directly coupled to a Gifford-McMahon cooler

A superconducting transition edge thermosensor (TES) microcalorimeter was irradiated with LX-ray photons emitted by an ²⁴¹Am source maintained at an operating temperature of 120 mK using a compact liquid-helium-free ³He-⁴He dilution refrigerator directly coupled to a Gifford-McMahon (GM) cooler. The first and second stages of the GM cooler were directly coupled to the first and second pre-cool heat exchangers of a stick shaped dilution unit through copper plates in a vacuum chamber. The helium-free dilution refrigerator provided a cooling power of 20 μW at 100 mK. Detection signals of LX-ray photons emitted by the ²⁴¹Am source were observed by operating the TES microcalorimeter in a severe noise environment induced by the mechanical vibrations of the GM cooler.     

Kinetics of the γ → α-alumina phase transformation by quantitative X-ray diffraction

This work reports the kinetics of α-alumina transformation from γ-alumina, prepared by the sol-gel method from a solution of saturated aluminum nitrate and urea. The γ-alumina phase transformed directly into α-alumina at 750, 800, 850 and 900 ^oC, without any intermediate phases, such as θ- or δ-alumina. The kinetics of γ → α-alumina phase transformation was monitored by determination of α-alumina fraction formed through quantitative X-ray diffraction (XRD), with calcium fluoride added as an internal standard. The crystallised fractions of α-alumina increased sigmoidally with time, indicating that the γ → α-alumina phase transformation had a nucleation and growth mechanism. The kinetic parameters for this transformation were determined through the Kolmogorov–Johnson–Mehl–Avrami (KJMA) model and the Arrhenius’ law. The apparent activation energy, the Avrami exponent, n, and the t _0.75/t _0.25 ratio determined for the transformation were, respectively, of (201 ± 4) kJ mol⁻¹ (2.1 ± 0.2) and (2.1 ± 0.1). The apparent activation energy is lower than the values previously reported for the γ → α-alumina transformation, as a consequence of the high surface area (425 m²/g) of γ-alumina. The t _0.75/t _0.25 ratio of (2.1 ± 0.1) suggested that the α-alumina growth was plate-like, which was confirmed by the SEM micrograph of α-alumina.     

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.     

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.     

Influence of temperature on the sorption properties of rocks from the Nizhnekansky massif

The kinetics of radionuclide sorption onto finely divided samples of rocks from the Nizhnekansky massif, taken from the level of the planned arrangement of deep radioactive waste repository, was studied, and the times in which the sorption equilibrium was attained at 20 and 90°С were determined. The distribution coefficients of actinides (²³³U, ²³⁹Pu, ²⁴¹Am) and fission products (¹³⁷Cs, ⁹⁰Sr) were determined. Increasing the temperature from 20 to 90°С intensifies the sorption of the radionuclides studied, except cesium for which the sorption slightly decreases.     

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.