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《Journal of Nuclear Science and Technology》2013,50(4):283-289
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. 相似文献
3.
A. A. Kozar' 《Atomic Energy》2001,91(2):667-675
The special features of 129I transmutation are discussed. The changes in content and equilibrium concentration of 127I in a target under recycling are calculated, and the conditions for decreasing the required radiochemical capacity in reprocessing of iodine are found. It is shown on the basis of an analysis of the neutron consumption in targets and estimates of the pressure of daughter xenon under the casing that the gaseous products of transmutation must be removed during the irradiation process along a loop channel. To increase the effectiveness and safety of 129I burnup, it is recommended that 129I be included in the volume of the gas permeable porous nuclear-inert targets by permeation with melts of iodine compounds. 相似文献
4.
Transmutation of 129I to 130I by (n, γ) reaction and isotope dilution with stable iodine were discussed. The transmutation in LWR is calculated by supposing that targets irradiated for 25 years are substituted with new targets. The result showed that initial amount of 129I will be reduced to 11.5%. In order to lower dose equivalent of general public than 0.1mSv/y, 400 times isotope dilution of 129I is required. The feasibility of the isotope dilution was discussed at dissolution process of spent fuel, conditioning process of the waste and disposal conditions. 相似文献
5.
Kazuji Miwa Hajime Obata Takashi Suzuki 《Journal of Nuclear Science and Technology》2020,57(5):537-545
ABSTRACTCurrently, 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. 相似文献
6.
S.E. Agbemava B.J.B. Nyarko J.J. Fletcher R.B.M. Sogbadji E. Mensimah M. Asamoah 《Annals of Nuclear Energy》2011
While there are growing demands for the nuclear data at higher energy regions than keV for up-to-date scientific and technological development, accurate capture cross sections at thermal energy are still needed. The thermal neutron capture cross sections for the reactions 127I(n,γ)128I, 152Sm(n,γ)153Sm,154Sm(n,γ)155Sm, and 238U(n,γ)239U were determined by the method of foil activation using 55Mn(n,γ)56Mn as a reference reaction. The experimental samples with and without a Cd cover were irradiated in an isotropic neutron field of a 20 Ci 241Am–Be neutron source facility. A high purity Ge detector was used to measure the induced gamma-rays from the samples and the monitor. The thermal neutron capture cross sections of the reactions 127I(n,γ)128I, 152Sm(n,γ)153Sm, 154Sm(n,γ)155Sm, and 238U(n,γ)239U were deduced from the analysis of obtained gamma-ray spectra. The thermal neutron capture cross section values for 127I(n,γ)128I, 152Sm(n,γ)153Sm, 154Sm(n,γ)155Sm, and 238U(n,γ)239U reactions are (5.93 ± 0.52), (207.3 ± 9.4), (7.7 ± 0.3), and (2.79 ± 0.09) barns respectively. The obtained results have been discussed and compared with the available experimental data and were found to be in agreement with each other. 相似文献
7.
The performance of the super-critical water-cooled fast reactor (Super FR) for the transmutation treatment of long-lived fission products (LLFPs) was evaluated. Two regions with the soft neutron spectrum, which is of great benefit to the LLFPs transmutation, can be utilized in the Super FR. First region is in the blanket assembly due to the ZrH1.7 layer which was utilized to slow down the fast neutrons to achieve a negative void reactivity. Second region is in the reflector region of core like other metal-cooled fast reactors. The LLFPs selected in the transmutation analysis include 99Tc, 129I and 135Cs discharged from LWR or fast reactor. Their isotopes, such as 127I, 133Cs, 134Cs and 137Cs were also considered to avoid the separation. By loading the isotopes (99Tc or 127I and 129I) in the blanket assembly and the reflector region simultaneously, the transmutation rates of 5.36%/GWe year and 2.79%/GWe year can be obtained for 99Tc and 129I, respectively. The transmuted amounts of 99Tc and 129I are equal to the yields from 11.8 and 6.2 1000 MWe-class PWRs. Because of the very low capture cross section of 135Cs and the effect of other cesium isotopes, 135Cs was loaded with three rings of assemblies in the reflector region to make the transmuted amount be larger than the yields of two 1000 MWe-class PWRs.Based on these results, 99Tc and 129I can be transmuted conveniently and higher transmutation performance can be obtained in the Super FR. However, the transmutation of 135Cs is very difficult and the transmuted amount is less than that produced by the Super FR. It turns out that the transmutation of 135Cs is a challenge not only for the Super FR but also for other commercial fast reactors. 相似文献
8.
T. Jabbar P. Steier 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(24):3183-3187
Atmospheric concentrations of many elements have been significantly increased by human activities. The quantification of these changes and their effect on the terrestrial and aquatic ecosystems is important because of their potentially adverse effects. The human nuclear activities, especially releases from the spent nuclear fuel reprocessing plants, are presently the main source of 129I in the environment.In this work, the concentration of 129I and the ratios of 129I/127I in aerosols weekly collected in Vienna, Austria (202 m a.s.l) during the year 2001 are presented. Iodine was extracted from the aerosol filters using a strong basic solution and separated from the matrix elements by anion exchange. The chemical yield of the procedure, determined by ICP-MS, ranges from 70% to 95%. The AMS results indicated that the 129I/127I isotopic ratios were of the order 10−8 to 10−7. The 129I originated from gaseous emissions from the Sellafield reprocessing plant. The measured 129I concentrations were compared with those of 7Be, a cosmogenic radionuclide. Although, both radionuclides exhibit nearly the same distribution pattern (higher levels in summer and lower in winter) their different origins can clearly be deduced from short term variations. 相似文献
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M.Afzal Ansari R.K.Yaiskul Singh M.L. Sehgal V.K. Mittal D.K. Avasthi I.M. Govil 《Annals of Nuclear Energy》1984,11(4):173-176
Fast-neutron radiative capture cross-sections have been measured relative to the 127I(n, γ)128I reaction cross-section using the comparative activation technique for 160Gd, 154Sm and 51V (using enriched isotopes and Specpure samples) at five different neutron energies between 1 and 3 MeV. The cross-section for 160Gd is reported for the first time in the above energy region. Experimental values are compared with the statistical-model calculations. 相似文献
11.
Kun Liu Hongchun Wu Liangzhi Cao Youqi Zheng 《Journal of Nuclear Science and Technology》2013,50(6):581-598
A systematic study on the long-lived fission product (LLFP) transmutation in a pressurized water reactor (PWR) is performed, aiming at an optimal transmutation strategy for present nuclear energy development. The LLFPs selected in the analysis include 99Tc and 129I discharged from light water reactors (LWRs). The isotope 127I is also considered to avoid the difficulties in isotopes separation. To minimize the negative impacts of LLFPs on the core performance and safety parameters, metallic technetium or MgI2 target pins mixed with ZrH2 are designed and investigated. Through the numerical analysis on equilibrium cycles, the transmuted amounts of 99Tc and 129I equal to the yields from 1.94 and 4.22 PWRs with a power of 1000 MWe, respectively. Numerical results indicate that both 99Tc and 129I can be transmuted conveniently in present PWRs in the form of target pins. 相似文献
12.
Iodine-125 is a radioisotopic impurity “always” present in iodine-123, produced by nuclear reactions induced either on natural or “highly” enriched targets. Liquid scintillation counting is a very sensitive tool to determine low level impurities of both low energy electrons and photons in aqueous and organic solutions of radiopharmaceutical compounds. With this technique it was possible to determine, on commercial samples, that the content of 125I was of the order of not less than 0.1% for 123I produced via 127I(p,5n) reactions and not less than 0.01% for 123I produced via “highly” enriched 124Xe(p,X) nuclear reactions. 相似文献
13.
《Journal of Nuclear Science and Technology》2013,50(6):481-486
The main γ-ray intensities in the 14N(n, γ)15N reaction were determined at an accuracy of 0.3–1.0% based on the intensity balance principle. Measurements were performed at the supermirror neutron guide tube at the Kyoto University reactor (KUR). A liquid nitrogen target and a deuterated melamine (C3D6N6) one were used. We prepared a full-energy-peak efficiency curve by combining the measured and calculated efficiency curves. The previous values widely used as intensity standards agreed with the present results within 4–5% in the 2–11 MeV region, but the ratio to the present values showed a monotonic decrease with the increase in _-ray energy. The results reported by Belgya in 2006 agreed with the present one within 2–3% in the 2–8MeV region; nevertheless, the ratio showed a small oscillation versusγ-ray energy. 相似文献
14.
《Journal of Nuclear Science and Technology》2013,50(2):211-216
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. 相似文献
15.
Van Do NguyenDuc Khue Pham Tien Thanh KimGuinyun Kim Manwoo LeeKyung Sook Kim Heung-Sik KangMoo-Hyun Cho In Soo KoWon Namkung 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(2):159-166
The thermal neutron cross-section and the resonance integral of the 165Ho(n,γ)166gHo reaction have been measured by the activation method using a 197Au(n,γ)198Au monitor reaction as a single comparator. The high-purity natural Ho and Au foils with and without a cadmium shield case of 0.5 mm thickness were irradiated in a neutron field of the Pohang neutron facility. The induced activities in the activated foils were measured with a calibrated p-type high-purity Ge detector. The correction factors for the γ-ray attenuation (Fg), the thermal neutron self-shielding (Gth), the resonance neutron self-shielding (Gepi) effects, and the epithermal neutron spectrum shape factor (α) were taken into account. The thermal neutron cross-section for the 165Ho(n,γ)166gHo reaction has been determined to be 59.7 ± 2.5 barn, relative to the reference value of 98.65 ± 0.09 barn for the 197Au(n,γ)198Au reaction. By assuming the cadmium cut-off energy of 0.55 eV, the resonance integral for the 165Ho(n,γ)166gHo reaction is 671 ± 47 barn, which is determined relative to the reference value of 1550 ± 28 barn for the 197Au(n,γ)198Au reaction. The present results are, in general, good agreement with most of the previously reported data within uncertainty limits. 相似文献
16.
Z. Lu U. Fehn X. Zhao W.E. Kieser H. Tomaru 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(7-8):952-955
We report here results comparing the efficiency of three iodine extraction methods for the determination of 129I/I ratios in small samples. The direct organic extraction had the highest average yield. 129I/I ratios determined from targets prepared by direct organic extraction and silver extraction are comparable to each other within the error limits. The smallest sample from which a reliable 129I/I ratio was measured, started with an iodine input of 0.2 mg iodine and contained 0.14 mg AgI in the target. 相似文献
17.
Vasily Alfimov Hans-Arno Synal 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(7-8):769-772
The 129I measurement program has been established at the 0.5 MV ‘Tandy’ accelerator of the PSI/ETH Zürich AMS facility. This development was made possible by using a SiN window instead of Mylar one in a gas ionization detector. The setting up of the 129I measurement at Tandy is simple, the acquired performance is stable and reliable, and the quality of results is equal to or better than at our larger EN-tandem. With this setup, high sample throughput, which is required in many 129I studies, can be easily achieved. The measurements are performed in the +3 charge state. At this charge state the major difficulty in the 129I+3 identification is caused by a highly abundant 43+1 (m = 43, q = +1) molecule interference. This is a positive molecular ion, because its intensity reduces exponentially with an increase in gas stripper pressure. We conclude that this molecule is 27Al16O+ (m/q = 43/1 = 129/3) and comes from the break-up of (Al2O3 + Al)? (m = 129) precursor at the terminal: (Al2O3 + Al)? → 27Al16O+. The expected isobaric interferences 43Ca+1 and 86Sr+2, which also originate from the break-up of molecules in the stripper, were found to be low and do not disturb the 129I+3 measurements. The best repeatable performance with our standard sample material was achieved at 0.14 μg/cm2 Ar gas stripper pressure with machine blanks showing ~6 × 10?14 normalized 129I/I ratio and 9% transmission through the accelerator. However, high 27Al16O+ molecular rates were observed from the user samples, and in order to destroy these molecules we had to increase the stripper pressure to ~0.22 μg/cm2. This increase in the stripper pressure degraded the machine blank values to ~9 × 10?14 and reduced transmission to 8%. Nevertheless, the achieved measurement conditions are sufficient for measurement of nearly all 129I samples that have been submitted to PSI/ETH over the last few years. 相似文献
18.
Atsushi Kimura Toshiyuki Fujii Satoshi Fukutani Kazuyoshi Furutaka Kaoru Y. Hara 《Journal of Nuclear Science and Technology》2013,50(7):708-724
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. 相似文献
19.
《Journal of Nuclear Science and Technology》2013,50(12):1099-1112
The purpose of this study is to measure the photoneutron emission rate after the shutdown of an operational BWR. The photoneutrons originate from the D(γ, n)H reaction in the moderator region, while the high-energy gamma rays are generated from 140Ba-140La transient equilibrium of fission products in irradiated fuel. The photoneutron emission rate is measured by means of the photoneutron signal ratio of the Start-up Range Neutron Monitor (SRNM). The ratio is defined as a ratio of the photoneutrons to neutrons originating from spontaneous fission and the oxygen (γ, n) reaction of actinides (242Cm, 244Cm, etc.) in irradiated fuel. The principle of the measurement of the photoneutron signal ratio is the large difference between the decay constants of the 140Ba-140La transient equilibrium and those of the actinides. The measurement of the SRNM signal was continuously carried out over several months, and the photoneutron signal ratio was evaluated by using the least-squares method to fit a theoretical model to SRNM signal data. The measurements were performed in the middle of the cycle at three BWR cores. Comparisons of the measured photoneutron signal ratio and the calculated one showed reasonable agreement. This demonstrates the validity and usefulness of the measurement. The absolute value of photoneutrons in the SRNM signal ranged from approximately 1 to 35 counts per second during a five-day cooling period after shutdown. Converting the absolute value to the relative fraction of photoneutrons in the SRNM signal results in a range from approximately 2 to 50%. 相似文献
20.
Hani Negm Hideaki Ohgaki Izuru Daito Takehito Hayakawa Heishun Zen Toshiteru Kii 《Journal of Nuclear Science and Technology》2013,50(6):811-820
The dependence of the nuclear resonance fluorescence (NRF) yield on the target thickness was studied. To this end, an NRF experiment was performed on 238U using a laser Compton back-scattering (LCS) γ-ray beam at the High Intensity γ-ray Source facility at Duke University. Various thicknesses of depleted uranium targets were irradiated by an LCS γ-ray beam with an incident beam energy of ~2.475 MeV. The scattering NRF γ-rays were measured using an High-purity Germanium (HPGe) detector array positioned at scattering angles of 90° relative to the incident γ-beam. An analytical model for the NRF reaction yield (NRF RY model) is introduced to interpret the experimental data. Additionally, a Monte Carlo simulation using GEANT4 was performed to simulate the NRF interaction for a wide range of target thicknesses of the 238U. The measured NRF yield shows the saturation behavior. The results of both of the simulation and the analytical model can reproduce the saturation curve of the scattering NRF yield of 238U against the target thickness. In addition, we propose a method to deduce the precise integral cross section of the NRF reaction by fitting the NRF yield dependency on the target thickness without any absolute measurements. 相似文献