Toshio Katoh

Measurement of Thermal Neutron Capture Cross Section and Resonance Integral of the 237Np(n, γ)238Np Reaction

The thermal neutron capture cross section (σ0) and the resonance integral (I 0)of 237Np have been measured by an activation method to supply basic data for the study of transmutation of nuclear waste. The neutron irradiation of 237Np samples have been done at the Research Reactor Institute, Kyoto University (KUR). Samples of 237Np were irradiated between two Cd sheets or without a Cd sheet. Since 237Np has a strong resonance at the energy of 0.49 eV, the Cd cutoff energy was adjusted at 0.358 eV (thickness of the Cd sheets: 0.125 mm). A high purity Ge detector was employed for activity measurement. The reaction rate to produce 238Np from 237Np was analyzed by the Westcotts convention. Results obtained were 141.7±5.4 barns for σ0 and 862±51 barns for I 0 above 0.358 eV of 273Np. By setting the Cd cut-off energy at 0.358 eV considering the resonance at 0.49 eV, a smaller value of σ0 was obtained in this work than the values reported by the previous authors.

Measurement of Thermal Neutron Capture Cross Section and Resonance Integral of the Reaction 133Cs(n, γ)134m,134gCs

The measurements of the thermal neutron (2,200 m/s neutron) cross section (σ0) and the resonance integral (I 0) of the 133Cs(n, γ;) reaction were performed by an activation method to obtain fundamental data for research on the transmutation of nuclear wastes. The cross sections for the formations of the isomeric state 134mCs and the ground state 134mCs were measured respectively by following the behavior of the γ-ray counting rate after the irradiation. The thermal neutron capture cross sections and the resonance integrals of the 133Cs(n, γ) reaction were determined to be 2.70±0.13 b and 23.2±1.8 b for the formation of the isomeric state 134mCs, and 26.3±1.0 b and 275±16 b for the formation of the ground state of 134gCs. The results for the reaction 133Cs(n, γ)134m+gCs were 29.0±l.0 b and 298±16 b, respectively. As for the thermal neutron capture cross section for the formation of 134m+gCs, the evaluated value (29.00 b) of JENDL-3.2 agreed with the present result. The reported value by Baerg et al. was in...

Measurement of the Thermal Neutron Capture Cross Section and the Resonance Integral of the 90Sr(n, γ)91Sr Reaction

In order to develop a neutron flux monitor for long-term neutron irradiation, the thermal neutron(2,200 m/s neutron) capture cross section (≤σ0) and the resonance integral (I 0)of the 109Ag(n,γ)110mAg reaction were measured by the activation and γ-ray spectroscopic methods. Silver foils were irradiated with and without a Cd shield capsule at the Rikkyo Research Reactor. The Co/A1 and Au/A1 alloy wires were irradiated together with silver foils in order to monitor the thermal neutron flux and the fraction of the epi-thermal neutron part (Westcotts index). A high purity Ge detector was used for the γ-ray measurements of the irradiated samples. The σ0 and the I 0 of the 109Ag(n,γ)110mAg reaction are 4.12±0.10 b and 67.9±3.1 b, respectively. The σ0 is 12% smaller than the tabulated one (4.7±0.2 b). On the other hand, the I 0 is in agreement with the tabulated one (72.3±4.0 b) within the limits of error.

Measurement of Thermal Neutron Capture Cross Section and Resonance Integral of the Reaction 127I(n, γ)128I

The thermal neutron (2,200 m/s neutron) capture cross section (σ0) and the resonance integral (I 0) of the reaction 127I(n, γ)128I were obtained. The targets of the iodine were irradiated within and without a cadmium capsule at Rikkyo University Research Reactor. Characteristic features of neutron field were monitored by Co/Al and Au/Al wires. Gamma-rays from the irradiated targets were measured by a high purity Ge detector. The γ-ray spectra were taken successively and the decay of peak-area counts of the 443 keV γ-ray of 128I was followed. A half-life of 128I obtained was 24.72±0.03 min. The σ0 and I 0 of the reaction 127I(n, γ)128I were deduced from the analysis of obtained γ-ray spectra according to the Westcotts convention and were 6.40±0.29 barns and 162±8 barns, respectively. The previous measurements of the σ0 and I 0 of the reaction 127I(n, γ)128I were reviewed and differences between the present values and the previous results were discussed with special emphasis on the experimental results by ...

Production of the Isomeric State of 138Cs in the Thermal Neutron Capture Reaction 137Cs(n, γ)138Cs

In order to obtain precise data of the neutron capture cross section of the reaction 137Cs(n, γ)138Cs, the production probability of isomer state 138mCs was measured in this work. Targets of about 0.37MBq 137Cs were irradiated for 3 min in. the pneumatic tube facility (Pn-3) of Kyoto University Reactor (KUR). The 1,436 keV gamma;-ray emitted from both of 138gCs and 138mCs was measured. A ratio of the production probability between 138gCs and 138mCs was deduced from time dependence of peak counts of 1,436 keV γ-ray by making use of difference of half-lives of 138gCs (33.41 min) and 138mCs (2.91 min). The production probability of 138mCs was obtained as 0.75plusmn;0.18 and this value revised the effective cross section upwards by 9plusmn;2percnt;. The effective cross section ô and the thermal neutron capture cross section σo were obtained as ô=0.29±0.02 b and σ=0.27±0.03b with taking into account the production of 138mCs.

Measurement of Thermal Neutron Capture Cross Section and Resonance Integral of the 166mHo(n, γ167Ho Reaction using a Two-Step Irradiation Technique

The thermal neutron capture cross section (a0) and the resonance integral (I0) of 166mHo have been measured as data for the transmutation of nuclear waste. Samples of 166mHo were made by the neutron irradiation of 165Ho. Two metallic foils of 165Ho were irradiated for 2 weeks and two others for 3 weeks at the Kyoto University Reactor. A high purity Ge detector was employed for activity measurement. The samples irradiated were cooled for 3 months to reduce the activity of 166gHo. One of the samples irradiated for 2 weeks was irradiated again with Cd cover sheets and the other one without a Cd cover sheet. For the samples irradiated for 3 weeks, the same irradiation was performed. The 167Hon uclei were produced at the second irradiation via the neutron capture of 166mHo and the double neutron capture of 165Ho. The amount of 167Ho via the double capture was estimated from the difference between the data of 2 week irradiation and 3 week irradiation, and corrected. The reaction rate to produce 167Ho from 166mHo was analyzed by Westcotts convention. A resonance at 0.274 eV was considered in the analysis. The results obtained were 3.11±0.82kb for the a0 and 10.0±2.7 kb for the Ia of 166mHo.

Precise Measurement of Gamma-ray Emission Probabilities of 100Ru

To precisely determine emission probabilities of γ rays of 100Ru, β-γ coincidence measurements have been performed. A thin plastic scintillator was used to detect f rays emitted from the ground state of 100Tc produced by thermal neutron capture reaction of99 Tc, while γ rays de-exciting the excited states of 100Ru populated via the β decays were detected using a high-purity germanium detector. In the data analysis, ratios of counting rates of f rays in coincidence with one of the 100Ru γ rays to that of f-ray singles were deduced at several finite β-ray detection threshold energies. The ratios at the zero threshold energy were then deduced by extrapolating the ones at finite threshold energies to take the effect of cascading γ rays into account. From the ratios at the zero threshold energy, the emission probabilities of 539 and 591 keV γ rays of 100Ru, which are emitted following the β decay of 100Tc, were obtained to be 6.6±0.5% and 5.5±0.3%, respectively. By following the decay of the two γ rays, half-life of the 100Tc nuclide was determined to be 15.27±0.05s.

Measurement of Effective Neutron Capture Cross Section of 166mHo using Two Step Irradiation Technique

Holmium-166m is one of the long-lived fission products, whose half-life is 1,200 yrCll. In the course of the systematic studyC2 ) of neutron capture cross sections of fission products, the thermal neutron capture cross section of 166mHo has been measured. There is no experimental data of thermal neutron capture cross section for 166mHo, except the resonance parameter measured by Masyanov et al.C3 l. They identified three resonances of 166mHo in the energy range of 0.001137 eV, and calculated from the resonance parameters the thermal capture cross section of 166mHo as 9.1±0. 7 kb and the resonance integral as 1.1±0.1 kb. They assumed the statistical weight of the channel spin C 4), g, be equal to 1. Present note describes the measurement of the effective capture cross section for thermal neutron of 166mHo by an activation method that is free from the ambiguity of the g factor. Two-step irradiation technique is introduced to make an activation method effective. The obtained value of the cross section, 3±1 kb, is about three times smaller than the value reported in Ref. (3).

Evaluation of β-γ Coincidence Measurement System Using Plastic Scintillation β-ray Detector Developed for the Determination of γ-ray Emission Probabilities of Short-lived Nuclides

For precise determination of γ-ray emission probabilities of short-lived nuclides whose half-lives are less than a few minutes, a β-γ coincidence measurement system has been developed which uses a plastic scintillator as a β-ray detector. The system was applied to a measurement of the absolute β-ray emission probability of 1,779keV β ray in 28A1 (Ti/2=2.24min), whose γ-ray emission probability is well known. The uncertainty of the measured γ-ray emission probability was smaller than 2%. Performance of the β-γ coincidence system has been demonstrated for a short-lived nuclide, and the details of the corrections have been analyzed.

Measurement of the Effective Neutron Capture Cross Section of Cesium-134 by Triple Neutron Capture Reaction Method

The measurement of effective neutron capture cross section( ) of 134Cs was carried out with a method using a triple neutron capture reaction,133Cs(n, γ)134Cs(n,γ)135Cs(n, γ)136Cs. The target used for the experiment was natural cesium(133Cs), and was irradiated for 23 days and 17 hours in the reactor JRR-3 at Japan Atomic Energy Research fnstitute(JAERI). The neutron field of the reactor was monitored by Au/Al and Co/Al alloy wires. A high purity Ge detector was employed for the measurement of γ-rays from the irradiated target and monitor wires. Gamma-rays emitted in the decay of 134Cs and 136Cs nuclides induced by single and triple neutron capture reactions of 133Cs were seen at the energies of 563, 569. 605, 796, 802, 819, 1,039, 1,048, 1,168 and 1,235 keV. Decays of the 819 and the 1,048 keV γ-ray intensities were followed; it was confirmed that these γ-rays originated in the 136Ba, the decay product of 136Cs. Data obtained were analyzed with values of neutron capture cross sections of 133Cs and 135Cs. ...