Determination of the 129I transmutation rate and 129I(n, 2n)128I correction using gas mass spectrometry

Two groups of ¹²⁹I and ¹²⁷I targets were analyzed using a gas quadrupole mass spectrometer (QMS) to determine the transmutation rates via the melting method. Sodium iodide was chosen to make the target. The iodine composition in the ¹²⁹I targets is 82.7% ¹²⁹I and 17.3% ¹²⁷I. The transmutation rate of the ¹²⁹I(n, γ)¹³⁰I reaction was determined by measuring the ¹³⁰Xe with QMS. An equivalent corrective method was brought out to correct the ¹²⁹I(n, 2n)¹²⁸I branch which is interfered with by the ¹²⁷I(n, γ)¹²⁸I reaction. And the correction formula was deduced in theory. For very little ¹²⁸Xe from the ¹²⁹I(n, 2n)¹²⁸I reaction, the equivalent corrective method could not be suitable here. However, it is suitable for the mass of ¹²⁸Xe from ¹²⁹I(n,2n)¹²⁸I reaction that reaches the accurately detective level of the mass spectrometry.     

Development of a Non-conservative Radionuclides Dispersion Model in the Ocean and its Application to Surface Cesium-137 Dispersion in the Irish Sea

A numerical simulation model system that consists of an ocean current model, Princeton Ocean Model (POM), and a particle random-walk model, SEA-GEARN, has been developed to describe the migration behavior of non-conservative radionuclides in a shallow water region. Radionuclides in the ocean are modeled in three phases, i.e., the dissolved phase in seawater, the adsorbed with large particulate matter (LPM) and the adsorbed with active bottom sediment. The adsorption and desorption processes between the dissolved and solid phases are solved by the stochastic method with the kinetic transfer coefficients. Deposition of the LPM and re-suspension from bottom sediment are also considered. The system was applied to simulate the long-term (24-year) dispersion of 137Cs actually released from the BNFL spent nuclear fuel reprocessing plant at Sellafield in United Kingdom. The calculation well reproduced the main characteristics of migration of dissolved ¹³⁷Cs concentration in the Irish Sea.     

Source term estimation of atmospheric release due to the Fukushima Dai-ichi Nuclear Power Plant accident by atmospheric and oceanic dispersion simulations

The source term of the atmospheric release of ¹³¹I and ¹³⁷Cs due to the Fukushima Dai-ichi Nuclear Power Plant accident estimated by previous studies was validated and refined by coupling atmospheric and oceanic dispersion simulations with observed ¹³⁴Cs in seawater collected from the Pacific Ocean. By assuming the same release rate for ¹³⁴Cs and ¹³⁷Cs, the sea surface concentration of ¹³⁴Cs was calculated using the previously estimated source term and was compared with measurement data. The release rate of ¹³⁷Cs was refined to reduce underestimation of measurements, which resulted in a larger value than that previously estimated. In addition, the release rate of ¹³¹I was refined to follow the radioactivity ratio of ¹³⁷Cs. As a result, the total amounts of ¹³¹I and ¹³⁷Cs discharged into the atmosphere from 5 JST on March 12 to 0 JST on March 20 were estimated to be approximately 2.0 × 10¹⁷ and 1.3 × 10¹⁶ Bq, respectively.     

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.     

Calcium isotope separation by band chromatography using 18-crown-6-ether resin

To develop the ⁴⁸Ca enrichment process, a feasibility study on a band chromatography was made using 9 M HCl solution and crown ether resin synthesized in porous silica beads. Prior to the chromatographic experiments, distribution coefficients, Kd, of Ca²⁺ and Sr²⁺ were measured at different concentrations of these ionic species. The frontal boundary of the chromatography was made by a usual manner of the breakthrough mode of calcium feeding, and the rear boundary was made by introducing strontium as a following ion on the basis of the observed Kd values. It was confirmed that the heavy isotope ⁴⁸Ca was depleted in the rear boundary region, while ⁴⁸Ca was enriched in the front boundary region. The values of separation coefficient ε (= α – 1) in three chromatographic operations at different temperatures were observed as 2 × 10^?3 ~ 3 × 10^?3. The separation coefficients observed in the front boundary regions, where ⁴⁸Ca was enriched, agreed with those observed in the rear boundary regions, where ⁴⁰Ca was enriched.     

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.     

Estimation of Total Amounts of Anthropogenic Radionuclides in the Japan Sea

We estimated the total amounts of anthropogenic radionuclides, consisting of ⁹⁰Sr, ¹³⁷Cs, and ^239+240 Pu, in the Japan Sea for the first time based on experimental data on their concentrations in seawater and seabed sediment. The radionuclide inventories in seawater and seabed sediment at each sampling site varied depending on the water depth, with total inventories for ⁹⁰Sr, ¹³⁷Cs, and ^239+240Pu in the range of 0.52–2.8 kBq m^?2, 0.64--4.1 kBqm^?2, and 27-122Bqm^?2, respectively. Based on the relationship between the inventories and the water depths, the total amounts in the Japan Sea were estimated to be about 1:2 ± 0:4PBq for ⁹⁰Sr, 1:8 ± 0:7PBq for ¹³⁷Cs, and 69 ± 14TBq for ^239+240Pu, respectively; the amount ratio, ⁹⁰Sr:¹³⁷Cs:^239+240Pu, was 1.0:1.6:0.059. The amounts of ⁹⁰Sr and ¹³⁷Cs in the Japan Sea were in balance with those supplied from global fallout, whereas the amount of ^239+240Pu exceeded that supplied by fallout by nearly 40%. These results suggest a preferential accumulation of the plutonium isotopes. The data used in this study were obtained through a wide-area research project, named the “Japan Sea expeditions (phase I),” covering the Japanese and Russian exclusive economic zones.     

Theoretical study of the adsorption of Cs,Cs+, I,I−, and CsI on C60 fullerene

Theoretical investigation for the adsorption of the cesium atom (Cs), the cesium iodide molecule (CsI), the iodine atom (I), the cesium cation (Cs⁺), and the iodide anion (I^?) onto the surface of a single fullerene molecule (C₆₀) are reported. A hybrid exchange–correlation functional using the Coulomb-attenuating method (CAM-B3LYP) is employed. The adsorption energies, i.e., the opposite of enthalpy change through adsorption, are calculated to be 143, 12, 9, 46, and 49 kJ mol^?1 for Cs, CsI, I, Cs⁺, and I^?, respectively. The equilibrium constant for Cs is calculated to be 7×10³ atm^?1 at the temperature of 1000 K and is seven orders of magnitude higher than that for CsI, indicating that the C₆₀ molecule adsorb the Cs atom highly selectively against the CsI molecule.     

Assessment for radiological impact of irradiated nuclear fuel package sunk in marine environment

Abstract

To gain the public acceptance for the transport of irradiated nuclear fuel, environmental impact assessments have been made by assuming that a transport package may be sunk into the sea. General circulation models for the Japan Sea and for the world ocean were employed to simulate radionuclide concentration in the ocean near shore and in deep sea areas respectively. Radionuclide concentrations were simulated for the hypothetical release from a submerged transport package of fresh mixed oxide fuel in the Japan Sea and the global ocean by general circulation models. Simulated concentrations were quite small compared to the background concentration by the fallout. The effective doses of radiation exposure to the public for both cases were much less than the effective dose limit (1 mSv year^–1) by the ICRP recommendation.     

Effect of spring water on the radon concentration in the air at Masutomi spa in Yamanashi Prefecture,Japan

The concentrations of ²²²Rn existing in air have been studied by using a convenient and highly sensitive Pico-rad detector system at Masutomi spa in Yamanashi Prefecture, Japan. The measurements in air were carried out indoors and outdoors during the winter of 2000 and the summers of 1999 and 2005. The concentrations of ²²²Rn in spring water in this region were measured by the liquid scintillation method. The concentrations of natural radionuclides contained in soils surrounding spa areas were also examined by means of the γ-ray energy spectrometry technique using a Ge diode detector to investigate the correlation between the radionuclides contents and ²²²Rn concentrations in air at each point of interest. The atmospheric ²²²Rn concentrations in these areas were high, ranging from 5 Bq/m³ to 2676 Bq/m³. The radon concentration at each hotel was high in the order of the bath room, the dressing room, the lobby, and the outdoor area near the hotel, with averages and standard deviations of the concentration of 441 ± 79 Bq/m³, 351 ± 283 Bq/m³, 121 ± 5 Bq/m³, and 23 ± 1 Bq/m³, respectively. The source of ²²²Rn in the air in the bath room is more likely to be the spring water than the soil. The spring water plays carries the radon to the atmosphere. Our measurements indicated that the ²²²Rn concentration in the air was affected by the ²²²Rn concentration in spring water rather than that in soil.     

Extraction of Lithium from Sea Water with Metallic Aluminum

Extraction of lithium from sea water was investigated. It was found that a corrosion product of metallic aluminum immersed in sea water extracts lithium from it selectively. Effects of the temperature and the pH of sea water, and of the initial concentration of lithium in it were examined. On the basis of the analysis of the surface deposit on aluminum, which is a corrosion product of aluminum, the selectivity coefficients were calculated. For the extraction of lithium from natural sea water, the values of K ^Li _Na ^Li _MgK ^Li _Ca and ^Li _K were 9.9 × 10², 1.1×10, 4.5×10 and 4.4 × 10², respectively.     

Sodium Fires and Aerosols

Release of ¹³¹I associated with burning of contaminated Na, decay of airborne concentration of the released ¹³¹I and the size distribution of aerosols referred to radioiodine are investigated in experimental runs conducted on laboratory scale. These investigations are carried out in conjunction with similar investigations for the Na matrix. An experimental chamber (5.4 m³) is used for burning a small pool of Na (–50 g) containing spiked ¹³¹I (40–500 μCi). Values of the specific activity ratio, viz. the ratio of the concentration of ¹³¹I in the aerosol Na to that in pool Na lay in the range of 0.9×10^?2—5.7×10^?2 at pool temperatures of about 300°C. The concentration decay half-time and the aerosol size distribution characteristics referred to ¹³¹I remain similar to those applicable to the Na content of the aerosols. Surface concentrations of ¹³¹I in the residues examined differ from the bulk concentrations (calculated) in the pool and are lower by a factor of ?20. The concentrations of ¹³¹I in the aerosols released are further lower than the surface concentrations in the residues by a factor of ?2.     

Neutron-capture cross-sections of 244Cm and 246Cm measured with an array of large germanium detectors in the ANNRI at J-PARC/MLF

The neutron neutron-capture cross cross-sections of ²⁴⁴Cm and ²⁴⁶Cm were measured by the time-of-flight method in the energy range of 1–300 300 eV with an array of large germanium detectors in the Accurate Neutron-Nucleus Reaction measurement InstrumentANNRI at Material and Life Science Experimental Facility (MLF) of the Japan Proton Accelerator Research ComplexJ-PARC/MLF. The ²⁴⁴Cm resonances at around 7.7 and 16.8 8 eV and the ²⁴⁶Cm resonances at around 4.3 and 15.3 3 eV were observed in the capture reactions for the first time. The uncertainties of the obtained cross cross-sections are 5.8% at the top of the first resonance of ²⁴⁴Cm and 6.6% at that of ²⁴⁶Cm. The rResonance analyses were performed for low-energy ones using the code SAMMY. The prompt γ-ray spectra of ²⁴⁴Cm and ²⁴⁶Cm were also obtained. Eight and five new prompt γ-ray emissions were observed in the ²⁴⁴Cm(n, γ) and ²⁴⁶Cm(n, γ) reactions, respectively.     

Measurement of Thermal Neutron Capture Cross Section and Resonance Integral of the 129I(n, γ) 130I Reaction

To obtain fundamental data for research on the transmutation of nuclear wastes, the thermal neutron cross section and the resonance integral of the ¹²⁹I(n, γ)¹³⁰I reaction have been measured using an activation method. The neutron cross sections for the formation of the ground (5⁺) state and the isomeric (2⁺) state of ¹³⁰I were measured separately.

Six ¹²⁹I targets were irradiated for 10 min with thermal reactor neutrons; three of them containing 2.55- 2.61 kBq of ¹²⁹I were irradiated within a Cd capsule, and the other three targets containing 259–261 Bq of ¹²⁹I were irradiated without it. The Co/Al and Au/Al alloy wires were used to monitor the neutron flux and the fraction of the epithermal part (Westcott's epithermal index). The gamma-ray spectra from the irradiated samples were measured with a Ge detector.

The thermal neutron capture cross section (the 2,200 m/s neutron cross section) and the resonance integral of the ¹²⁹I(n, 7)¹³⁰I reaction were determined to be 12.5±0.5b and 15.6±0.7b for the formation of the ground state ^130gI(5+), 17.8±0.7b and 18.2±0.8b for the formation of the isomeric state ^130mI(2⁺), and 30.3±1.2b and 33.8±1.4b for the formation of ¹³⁰I (the sum of the 2⁺ and the 5⁺ states), respectively. The sum of the thermal neutron capture cross sections forming the 2⁺ and the 5⁺ states was 12% larger than the evaluated values of JENDL-3.2 and ENDF/B-VI and that reported by Roy et al. This discrepancy is explained by the population of the isomeric level.     

177Lu标记单克隆抗体Rituximab

以CHX-A''''-DTPA和p-SCN-Bz-DTPA为双功能螯合剂,分别对Rituximab进行偶联,用¹⁷⁷Lu进行标记,制备¹⁷⁷Lu-Rituximab。在优化条件下,¹⁷⁷Lu对单抗偶联物CHX-A''''-DTPA-Rituximab和p-SCN-Bz-DTPA-Rituximab的标记率和放化纯度均大于99%。室温及37 ℃条件下,¹⁷⁷Lu-Rituximab在各种测试体系中均显示良好的体外稳定性。在正常小鼠体内的生物分布结果显示,¹⁷⁷Lu-Rituximab发生了分解,游离的¹⁷⁷Lu在骨中形成较高浓集。¹⁷⁷Lu-p-SCN-Bz-DTPA-Rituximab比¹⁷⁷Lu-CHX-A''''-DTPA-Rituximab的体内清除快,而且游离¹⁷⁷Lu的骨摄取低,结果表明,p-SCN-Bz-DTPA更适于作为双功能螯合剂用于单抗的¹⁷⁷Lu 标记。     

Atmospheric discharge of 14C from the Tokai reprocessing plant: comprehensive chronology and environmental impact assessment

Quantitative evaluation of the atmospheric discharge of radiocarbon (¹⁴C) is of primary importance for accurately assessing the radioecological impact of the operation of the Tokai reprocessing plant (TRP). However, monitoring the atmospheric ¹⁴C discharge was not conducted at the TRP prior to October 1991. The main purpose of this study was to establish the chronology of atmospheric ¹⁴C discharges for the entire operation period (1977–2014). We found a strong correlation between the ¹⁴C discharge and spent fuel reprocessing data obtained after October 1991; we used this correlation to estimate the monthly ¹⁴C discharges in the 1977–1991 period. The total amount of atmospheric ¹⁴C discharge was estimated at 7741 ± 217 GBq for the entire period, with the largest annual discharge of 978 GBq in 1992. Tree-ring ¹⁴C analysis and model calculations using the established discharges were conducted to assess the excess ¹⁴C concentrations around the TRP in the past. The results suggested that the excess ¹⁴C concentrations were <45 Bq kg^?1 C and the annual effective dose via the atmosphere–rice ingestion pathway was as low as 1.2 μSv y^?1, indicating no significant radioecological impact of atmospheric ¹⁴C discharges from the TRP.     

Trapping and Measuring Radioiodine (Iodine-129) in Cartridge Filters

To understand the distribution of ¹²⁹I trapped in AgS (silver-impregnated silica gel) adsorbent and to determine a calibration curve for measurement of this ¹²⁹I, cartridges containing 10 in-line (arranged in series) filter elements, each packed with a 10-mm thickness of adsorbent, were fed from 20Bq (3.3 μg) to 4.6 MBq (768mg) of ¹²⁹I at 150°C at a gas velocity of 22cm/s. The ¹²⁹I in each filter element was measured after the adsorbent had been mixed homogeneously until the counting rates at the front and back surfaces of the filter element became equal. The amount of input ¹²⁹I was allocated to each filter in proportion to the counting rates thus obtained.

The first 7 of the 10 filter elements completely confined 4.6MBq of ¹²⁹I. Therefore, the width of the adsorption zone was 7cm. Although each filter element in the cartridge could theoretically adsorb 2.92 MBq (485mg) of ¹²⁹I, the first element captured only 1.42 MBq, which was 49% of its saturation value. Its DF had dropped to a level of 2.21 for its adsorption of only 17.4% of the saturated amount. As ¹²⁹I continued to be deposited, the DF dropped to 1.45. The high gas velocity causes this phenomenon. Plots of counting rates vs. adsorption quantity provide a calibration curve covering a range of 20Bq to 2MBq of ¹²⁹I with deviation of ± 13%. This curve is expressed by

1n y = ?0.57 + 0.961n x

where y is the counting rate (counts/300s) and x the quantity of ¹²⁹I in Bq.     

Attenuation length of high energy neutrons through a thick concrete shield measured by activation detectors at CHARM

ABSTRACT

A deep-penetration shielding experiment was performed at the CERN High-energy AcceleRator Mixed-field (CHARM) facility. The protons (24 GeV/c) were injected into a 50-cm-thick copper target and the released neutrons were transmitted through a bulk concrete shield located vertically upward from the target, where they were measured with bismuth and aluminum activation detectors placed at various penetration distances in the shield. From the radionuclide production rate in the activation detectors, the attenuation profiles through the concrete shield were obtained for the reactions of ²⁰⁹Bi(n,xn)^210-x Bi(x = 4–9) and ²⁷Al(n,α)²⁴Na. The attenuation length of the high-energy neutrons through ordinary concrete was estimated as 120 g/cm², in good agreement with Monte Carlo simulations using simple slabs as a universal geometry implemented in Particle and Heavy Ion Transport System (PHITS) code. Proton energy dependence of attenuation length was also investigated with simulations by PHITS code and comparisons with the published data were discussed.     

Application of Fibrous Carbon Ferrocyanide Sorbents for Removing Cesium and Cobalt from Large Volumes of Sea Water

The results of comparative tests of the FN sorbent based on iron diferrocyanide with a matrix base form of fibrous carbon with known commercial and laboratory analogs are presented. The possibility of using this sorbent for selective removal of ¹³⁷Cs and ⁶⁰Co for large volumes of sea water and producing fast methods of analysis is examined. Information is presented on the content of technogenic radionuclides in sea water in regions of disposal of radioactive wastes in the Sea of Japan and in the region of the accident on a nuclear powered submarine. It is shown that the disposal of radioactive wastes in the Sea of Japan did not change the background radioecological conditions. The radioactivity of sea water at the epicenter of the accident in Bukhta Chazhma is a consequence of the accident and is due to ⁶⁰Co; the presence of ¹³⁷Cs and ⁹⁰Sr is due to global fallout. The concentration of technogenic radionucldes in water and hydrobionts does not exceed admissable norms. Consumption of up to 100 kg/yr of marine products does not increase dose loads above the limit of the yearly individual lifetime risk established for the public and corresponds to a low radiation danger.     

Trend in criticality calculation results of borated-water-moderation experimental cores relating to 10B(n, α) cross section

ABSTRACT

In connection with the accuracy of the ¹⁰B(n, α) cross section in the thermal- and epithermal-neutron energy regions, criticality calculation results were examined for six benchmark sets of light-water-moderation critical experiments of UO₂ and MOX fuel lattice cores with un-borated and borated water. Two of the benchmark sets were those implemented in the Tank-Type Critical Assembly (TCA). The others were taken from the International Handbook of Evaluated Criticality Safety Benchmark Experiments (ICSBEP), and the International Handbook of Evaluated Reactor Physics Benchmark Experiments (IRPhEP). The enrichments of the UO₂ fuel range from 1.9 wt% to 2.6 wt%, and the Pu contents of the MOX fuel do from 2.0 to 6.6 wt%. The boron concentrations in water are up to 1511 ppm. The effective neutron multiplication factors (k_eff ) were taken from the published documents. They were calculated with continuous-energy Monte Carlo calculation codes in combination with JENDL-4.0, and other evaluated nuclear data libraries. It was confirmed that the k_eff values of the critical cores increased with the boron concentrations, which indicates that the ¹⁰B(n, α) cross section in the thermal- and epithermal-neutron energy regions should be larger than those in JENDL-4.0 and other libraries.