Gadolinium Isotope Separation by Cation Exchange Chromatography

Displacement chromatographies of Gd adsorption band in cation exchange resin were performed to observe the isotope effects in the Gd ion exchange processes involving complex forming reagents. The heavy isotope of ¹⁶⁰Gd was found to be enriched at the front boundary of Gd adsorption band and the lighter isotopes of 1MGd, ¹⁵⁶Gd and ¹⁵⁷Gd were enriched at the rear boundary in both cases of 20.1m elution with EDTA and 14 m elution with malic acid, as predicted in the theoretical relations. Observed separation coefficients are 4.9×10^?5, 4.0×10^?5 and 2.5×10^?5for isotopie pairs of ^{156 160}Gd, ¹⁵⁸Gd and ¹⁶⁰Gd, respectively, in the case of EDTA elution. In the case of malic acid elution, smaller separation coefficients were observed as 1.8×10^?5, 1.6 ⁵O^?5 and 0.92×10^?5 for isotopie pairs of ^{156 160}Gd, ¹⁵⁷Gd and^{158 160} respectively.     

Zinc Isotope Fractionation on Benzo-15-crown-5 Resin by Liquid Chromatography

Chromatographic fractionation of zinc isotopes was performed on the synthesized benzo-15-crown-5 resin as a column packing material at 323K in the breakthrough manner for both a frontal and a rear bands. Zinc adsorption capacity was affected by anion chloride concentration and solvent dielectric constant. The heavier zinc isotopes were found enriched to the solution phase and the lighter zinc isotope was concentrated on the resin phase. The frontal maximum enrichment ratio for isotopic pair of ⁶⁸Zn/⁶⁴Zn was 1.0081. The isotope separation coefficients for isotopic pair of ⁶⁸Zn/⁶⁴Zn for frontal and rear band, were 5.3 × 10^?4, 4.5 × 10^?4, respectively.     

Zinc Isotope Effects Observed by Liquid Chromatography with Benzo-15-Crown-5 Resin

The chromatographic fractionation in Zn isotopes was performed on the synthesized benzo-15-crown-5 resin at 313 and 343 K. The lighter isotopes were found enriched in the resin phase. The isotope fractionation coefficients (ε) were 3.4 and 2.9×10^?4, 4.7 and 4.7×10^?4, and 6.7 and 5.7×10^?4 for the ⁶⁶Zn/⁶⁴Zn, ⁶⁷Zn/⁶⁴Zn and ⁶⁸Zn/⁶⁴Zn isotopic pairs at 313 and 343 K, respectively. They reflected mass-dependence among the Zn isotopes at each operated temperature but did not show 1/T² -temperature proportionality. The temperature effects of the composition of Zn species both in the solution phase and in the resin phase may account in part for the latter observation. The magnitudes of ε's in this study were comparable to the ones obtained by ion exchange chromatography, but much smaller than those observed in the solvent extraction systems with a crown ether in the organic phase.     

Uranium Isotope Separation by Cation Exchange Chromatography Using Uranous Sulfate Complexes

A nearly ideal displacement chromatography has been realized with an eluent of MgS0₄ and H₂SO₄ in the study of uranium isotope separation by means of cation exchange chromatography using uranous sulfate complexes. Uranium-235 was enriched at the end of the chromatogram and ²³⁸U was enriched at the front. Two long distance displacement experiments have been carried out, keeping an isotopic plateau region on the chromatogram. Consequently, good accumulation of the isotopic fractionation based on uranous-sulfate complex formation reactions obtained. The separation coefficient ε of this system was estimated to be about 5×10^?5.     

A sensitive method for Sr-90 analysis by accelerator mass spectrometry

ABSTRACT

Strontium-90 is one of the most important fission products due to the potential health risks of its uptake and retention in the human body. Conventional analysis techniques involve β counting, which requires ingrowth of ⁹⁰Y over a period of two weeks. Accelerator mass spectrometry (AMS) has the potential to shorten the analysis time while offering a lower limit of detection than β counting. Here, Sr in samples was recovered as SrF₂ to provide sufficient negative ions in the caesium-sputtering ion source. In the sample preparation step, 95–98% of Sr was recovered and 99–100% of Zr removed by ion-exchange separation. Sr recovery was ~30% in the precipitation process, and this can be improved. A maximum 500 nA beam current of SrF₃ ^– ions was obtained from SrF₂ samples mixed with PbF₂. A five-anode gas ionization detector was used to avoid isobaric interference from ⁹⁰Zr. The ⁹⁰Sr/Sr atomic ratio background of ~6 × 10^–13 (~3 mBq ⁹⁰Sr) was comparable with that achieved at other AMS facilities. Good linearity in ⁹⁰Sr/Sr atomic ratios was obtained from 1.75 × 10^–10 to 3.38 × 10^–9. Suitable techniques for sample preparation and measurement were thus achieved for ⁹⁰Sr analysis by AMS.     

Atmospheric 85Kr and 133Xe activity concentrations at locations across Japan following the Fukushima Dai-ichi Nuclear Power Plant accident

Atmospheric ⁸⁵Kr and ¹³³Xe activity concentrations were determined from weekly air samples collected at Sapporo, Akita and Chiba, Japan, throughout 2011. The results demonstrated that the Fukushima Dai-ichi Nuclear Power Plant accident in early March 2011 resulted in high ¹³³Xe activity concentrations as well as elevated levels of ⁸⁵Kr activity; there was a striking increase in the concentrations of both isotopes over the week running from 14 to 22 March as the radioactive plume released from the plant was captured. At Chiba, following the accident, the ⁸⁵Kr activity concentration increased from 1.38 to 17.7 Bq/m³, while the ¹³³Xe levels increased from below the minimum detectable concentration (MDC ≤ 1.9 × 10^?3 Bq/m³) to 1.3 × 10³ Bq/m³. Conversely, at Sapporo and Akita, high ⁸⁵Kr activity concentrations were not observed, due to differences in air transportation mechanisms based on wind directions. Duplicate samples were collected at Chiba to allow the simultaneous analyses of ⁸⁵Kr and ¹³³Xe at the Japan Chemical Analysis Center and the Bundesamt für Strahlenschutz in Germany and the results were in good agreement. The external effective radiation doses resulting from ⁸⁵Kr and ¹³³Xe releases following the accident were estimated to be approximately 7.0 × 10^?3 and 1.3 μSv, respectively, based on the activity concentrations of these nuclides from March to June in 2011 at Chiba.     

Vertical distributions of Iodine-129 and iodide in the Chukchi Sea and Bering Sea

ABSTRACT

Currently, most Iodine-129 (¹²⁹I) present in the environment is anthropogenic; it has been released from European nuclear reprocessing plants and transported into the northern part of the Arctic Ocean via ocean circulation. This study investigates the ¹²⁹I distribution in the Chukchi Sea and Bering Sea by considering water mass structure. The range of ¹²⁹I concentration is 0.89–5.03 × 10⁷ atoms L^?1 in the studied area, which is considered to be the fallout level. ¹²⁹I was found to be distributed almost uniformly. An increase in ¹²⁹I concentration levels caused by high ¹²⁹I water inflow from the Atlantic Ocean was not observed. Additionally, we revealed the vertical distribution of iodide, one chemical form of iodine, from the Bering Shelf area to the Chukchi Sea for the first time. The range of iodide concentrations was found to be 10–157 nM. Moreover, an increasing tendency of iodide near sea bottom was observed, suggesting that iodide is released from sediments at the bottom of the sea.     

Quantitative Analysis of Boron with Solid State Track Detector

In a study aimed at the application of solid state track detectors to the quantitative analysis of boron, track detector plates of cellulose nitrate were set in polypropylene test tubes, filled with various concentrations of boron-agar solution, and irradiated with thermal neutrons. After irradiation, the cellulose track detectors were separated from the solution, and etched with suitable chemical reagents. The number of etch-pits observed on the plate surface was counted by means of an optical microscope. The experiments proved that the number of etch-pits per unit area P (cm^?2) is proportional to the product of the ¹⁰B-concentration τ (atom·cm^?3) and the thermal neutron fluence φ (cm^?2): P=bτφ, where b is the ¹⁰B-detection efficiency. If p is the number of ¹⁰B(n, a)⁷Li reactions per cubic centimeter, P=pρ, where p is the etch-pit formation efficiency. The maximum values of b and p obtained in these experiments were 1.3 × 10^?24 cm³, and 3.3 × 10^?4 cm, respectively. The mean effective range of α and ⁷Li particles in the solution was found to equal 2p.     

Strontium Isotope Effect in Liquid-Liquid Extraction of Strontium Chloride Using a Crown Ether

Isotope effects in a liquid-liquid extraction of strontium with dicyclohexano-18-crown-6 (DC18C6) were investigated. Unit mass enrichment factors were observed to increase with concentrations of strontium salt in an aqueous phase. Isotope distinguishing ability of DC18C6 to strontium isotopes was calculated as an intrinsic separation factor to be K _c =1.00051±0.00004. An odd mass number isotope, ⁸⁷Sr, was recognized to behave differently from even mass number isotopes, ⁸⁴Sr, ⁸⁶Sr and ⁸⁸Sr. The enrichment factor induced by a nuclear property (odd or even mass number) other than the mass difference was ε_O/E = ?8.0 × 10^?4 which was observed with 3.2M Sr aqueous solution. Isotope shift of energy state for 5S-orbital of strontium produces the isotope shift in vibrational energy between the strontium ion and the DC18C6.     

Production of high-purity medical radio isotope 64Cu with accelerator-based neutrons generated with 9 and 12 MeV deuterons

We conducted a feasibility study for producing a high-purity medical radioisotope ⁶⁴Cu from natural zinc with accelerator-based neutrons. ⁶⁴Cu isotopes were produced via the ⁶⁴Zn(n,p) reaction. The accelerator-based neutrons were generated via the C(d,n) reaction using low-energy deuterons of 9 and 12 MeV on a 1-mm-thick carbon target. First, the production purity was estimated using the evaluated nuclear data library JENDL-4.0 and our previously measured thick target neutron yield. We found that even when natural zinc was used as the starting material, significantly high-purity ⁶⁴Cu could be obtained. Next, irradiation experiments for producing ⁶⁴Cu using natural zinc were conducted at Kyushu University Tandem Laboratory, with the amounts of ⁶⁴Cu isotopes and other gamma-emission nuclides measured by a high-purity germanium detector. As a result, high-purity ⁶⁴Cu isotopes of 1.11(49) × 10⁰ and 3.70 (17) × 10⁰ Bq/g/μC were produced with incident deuteron energies of 9 and 12 MeV, respectively.     

Resonance Parameters of Tantalum-181 in Neutron Energy Range from 100 to 4,300eV

Neutron transmission measurements were performed on natural tantalum (abundance ratio 99.988% for ¹⁸¹Ta) in the energy range of 100–4,300 eV using the Japan Atomic Energy Research Institute linac. The transmissions were measured using 55 and 190 m time-of-flight spectrometers for two and three samples of different thicknesses, respectively. These transmission data were simultaneously analyzed with a least squares fitting program based on a multl-level Breit-Wigner formula, and resonance energies and neutron width were obtained for 696 resonances of ¹⁸¹Ta.

The statistical analysis of these parameters gave the s-wave average level spacing of D=4.10±0.14 eV and s-wave neutron strength functions of (1.67±0.13) × 10^?4, (1.09 ± 0.09) × 10^?4 and (1.42 ± 0.20) × 10^?4 for the energy intervals from 100 ? 1,700 eV, 1,700–3,400 eV and 3,400–4,300 eV, respectively. This significant difference among the neutron strength function for each energy interval is a prominent result of the present experiments and is of great interest.     

Tungsten Blister Formation Kinetic as a Function of Fluence,Ion Energy and Grain Orientation Dependence Under Hydrogen Plasma Environment

This work deals with the formation kinetic of tungsten (W) blisters under smooth plasma conditions, i.e. low hydrogen flux and energy in order to analyze the first stages of their formation. In addition, we focus on determining the W grain orientation where blisters grow preferentially. For this purpose, mirror-polished polycrystalline tungsten samples were exposed to hydrogen plasma under fixed hydrogen flux of 2.2 × 10²⁰ m^?2 s^?1, with a fluence in the range of?~?10²⁴ m^?2, ion energy of?~?20, 120 and 220 eV, and sample surface temperature of?~?500 K. The formation of blisters at the surface was investigated using SEM, AFM and EBSD to determine the size, the distribution and the orientation of grain where blisters are formed, respectively. The critical fluence for initiating blisters was established around 2.3 × 10²⁴ m^?2. The evolution of blister size distribution and density is discussed as function of fluence and ion energy. At lower ion energy, i.e. 20 eV, only nanoblisters (less than 150 nm) are observed whatever the fluence value (1.5 and 2.3 × 10²⁴ m^?2). At higher ion energy i.e. 120 and 220 eV, micrometric (~ few to tens of µm) blisters are observed and their density highly depends on fluence. We show that blisters can also be formed on (001) oriented grains contrarily to previous results from the literature where the (111) orientation seemed more favorable. Such information is of importance for tungsten based fusion tokamak operation and design.     

Temperature Coefficient of Water Lattices

Temperature coefficients of slightly enriched UO₂-H₂O lattices were measured in the Ozenji Critical Facility and analyzed in terms of critical parameters. The lattices studied were mainly those of 2.5% enriched UO₂, 10 mm in diameter and clad in 0.8 mm thick Al tube, and with water to fuel volume ratios of 2.5 and 1.5. Analyses were made with Deutsch's four factor critical equation and also with three group one dimensional diffusion calculations.

The result shows the importance of the influence of the reflector, which is the largest positive contribution to the temperature coefficient, being about 1×10^-4 Δk/k/°C. This was experimentally demonstrated by measuring the coefficient for a core with an inner reflector water gap. Analyses also show that the discrepancy between experiment and calculation, which increases from 0.2 to 0.7×10^-4 Δk/k/°C as the water to fuel volume ratio decreases, may be mostly resolved by applying corrections for the space-dependent spectrum within the cell using the THERMOS code and for the effect of Dancoff factor with the TUZ-ZUT code. Calculation with these corrections applied reproduces experiment within an accuracy of about 0.2×10^-4 Δk/k/°C over the temperature range of 20° to 70°C.     

Effects of water-to-cement ratio and temperature on diffusion of water in hardened cement pastes

Apparent diffusion coefficients (D_a) of water and activation energies (E_a) of diffusion in hardened cement pastes (HCPs) were determined as a function of water-to-cement (w/c) ratio (0.36–0.60) and temperature (293–323 K) using HTO and H₂¹⁸O as tracers. The values of D_a and E_a ranged from 1.1×10^?11 to 1.7×10^?10 m² s^?1 and from 21.5 to 31.3 kJ mol^?1, respectively. No significant difference between the D_a values of HTO and H₂¹⁸O suggests that water predominantly diffuses as H₂O molecule and dissociation of water is not significant even at high pH range in HCP. The values of E_a at low w/c ratio were higher than in bulk liquid water, suggesting a contribution of a different water regime, such as supercooled bulk water. Two simple models consisting of capillary and gel pores were considered to estimate the volume ratio of gel pores to total pores by optimizing the model to fit with the experimental data. The result suggests that HCP has a pore network mostly consisting of capillary pores with some very narrow pores plugged with hydrates, where HTO must diffuse through gel pores. This view of the HCP pore network was made available through analysis of E_a values.     

Chemical State and Deposition Rate of Nickel Ion Deposit Produced on Heated Surface in High Pressure Boiling Water

Nickel ion deposit was produced on a heated rod surface in high pressure boiling water (150–285°C, 0.4–7.0 MPa). The deposit under the same temperature and pressure conditions as those for BWR reactor water (285°C, 7.0 MPa) was identified as NiO by spectrum profile analysis of the NiLα, NiLβ and 9th-order NiKα₁ lines. Deposition rate was obtained from in situ measurements of deposit thickness, by a photoacoustic method, and from chemical analysis of deposit amount. The deposition rate coefficients obtained in temperature and pressure ranges of 150–250°C and 0.4–4.0 MPa were 2 × 10^?3–5 × 10^?2, which were 0.15–0.45 times as large as those of iron crud. This was attributed to a dissolution effect of Ni ion from NiO. The deposition rate coefficient at 285°C, 7.0 MPa was estimated to be 4.4 × 10^?2–1.3 × 10^?1.     

Sorption Behavior of Selenium(—II) on Rocks under Reducing Conditions

The sorption of radionuclides on rocks is an important factor for performance assessment of geologic disposal of radioactive wastes. Batch sorption experiments under reducing conditions were carried out to investigate the sorption behavior of selenium onto granodiorite, sandy mudstone, tuffaceous sandstone, and their major constituent minerals and accessory minerals. Rock cores and groundwater employed in the experiments were sampled with special care to avoid exposing the cores and groundwater to air to minimize their oxidation. Selenium was spiked as HSe^? and Se₄ ^2- in the experimental solutions, and reducing conditions were maintained throughout the sorption periods. Distribution coefficients, Kd (m³ kg^?1), were obtained in the ranges of 2.2 × 10^?4 to 4.0 × 10^?3 m³ kg^?1 for granodiorite, 3.3 × 10^?2 to 5.6 × 10^?2 m³ kg^?1 for sandy mudstone, and 2.9 × 10^?2 to 8.2 × 10^?2 m³ kg^?1 for tuffaceous sandstone at pHs 8.5 to 11.5. The dominant sorbent minerals for selenium over a neutral to alkaline pH range were determined to be biotite for the granodiorite samples and pyrite for the sandy mudstone and tuffaceous sandstone samples.     

Experimental study of pulse neutron irradiation damage in SiGe HBT

The response to transient irradiation of npn SiGe HBT (BG35 SiGe BiCMOS), i.e. device under test (DUT) was studied with online measurement of 1 MeV equivalent pulse neutron fluence of 0.8 × 10¹³n/cm². The differently biased DUT1 and DUT2 in test circuit were irradiated in the first day with neutron fluence (0.8 × 10¹³n/cm²) termed as Fluence1 and with an additional neutron fluence (0.8 × 10¹³n/cm²) in the second day to make Fluence2 equals to 1.6 × 10¹³n/cm². The experimental results show that pulsed neutron irradiation causes voltage surges in the DUTs exhibited by a negative and positive peak known to be radiation damage (RD). The RD in DUTs induced by pulse neutron Fluence1 initially created unstable displacement defects and the defects later reordered (cluster defects) to form more stable configurations via neutron Fluence2. The irradiated DUTs experienced online instantaneous annealing after 2.03 × 10^?9 s and offline measurement (i.e. without irradiation) of DUTs showed recovery to normal mode of operation after 24 h annealing. The level of pulse peaks in the base voltage terminals of DUT1 and DUT2 were compared as V_b2Fluence1 > V_b1Fluence1 and V_b2Fluence2 > V_b1Fluence2. A comprehensive analysis of RD region in DUTs with reference to Area (A₁, A₂), Peak (P₁, P₂), Height (H), and Full width at half maximum (FWHM) were investigated.     

Grain boundary diffusion of tritium in 304- and 316-stainless steels

Grain boundary diffusion of tritium in 304- and 316-stainless steel was studied over the temperature range -78 °C to 185 °C through direct measurement of tritium concentration profiles. Tritium was injected through transmutation of a surface blanket of ⁶LiF, specimens were heated isothermally to establish a tritium diffusion gradient, and the specimen layers containing the rapidly-diffusing grain boundary component were removed with a lathe and/or electropolishing. The data were analyzed by both Fisher's and Suzuoka's models for grain boundary diffusion and similar diffusion coefficients were obtained. Grain boundary diffusion coefficients (G) and their standard deviation are given by: (Fisher) G = exp (8.85 ± 1.2) × exp (? 0.45 ± 0.03 eV/kT) cm²-sec¹, (Suzuoka) G = exp (8.55 ± 0.85) × exp (? 0.43 ± 0.02 eV/kT) cm²-sec^{? 1}.     

Estimation of the radiation dose equivalent for the hypothetical submergence of a sea-transport package of low-level radioactive waste

Japanese Electric Power Utilities plans to transport low-level radioactive waste (LLW) in CSD-C (36 canisters) and CSD-B packages (10 canisters) by sea from France to Japan. In this study, we carried out assessments of the dose to the public from a hypothetical release of radioactive materials from submerged LLW packages into the sea. The estimated dose equivalents from the CSD-C and CSD-B packages were 2.8 × 10^?8 and 7.9 × 10^?9 mSv year^?1, respectively, for the near shore case. For the deep sea case, the estimated dose equivalents were 8.6 × 10^?8 and 5.8 × 10^?8 mSv year^?1, respectively. These estimated results were much smaller than those found in a previous study of Type-B packages (spent fuel, high level waste, and mixed oxide fuel) and the ICRP recommendation (1 mSv year^?1).     

The Influence of Cathode Voltage and Discharge Current on Neutron Production Rate of Inertial Electrostatic Confinement Fusion (IR-IECF)

In this research effect of gas pressure, discharge current and cathode voltage on the neutron production rate in IR-IECF device is studied. In the experiment discharge current from 20 to 100 mA was tunable by deuterium gas pressure from 6.4 × 10^?3 mbar to 1.7 × 10^?2 mbar and cathode voltage was changed from 20 to 80 kV. Moreover, maximum value of neutron production rate can be achieved in optimum pressure and discharge current at a constant voltage.