Measurement of Thermal Neutron Cross Section of ~(135)Cs

The thermal neutron cross sections of the long-lived fission products are important for the study of nuclei structure,partitioning-transmutation of radioactive waste,neutron activation analysis,and so on. 135Cs emits pure β ray,and it has a half-life of …     

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 Cross Section of ^135Cs

350keV高压倍加器辐照装置的真空系统自2005年1月安装完成后，到目前已运行12个月，其运行状况正常。     

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 good agreement with the present result within the limits of error on the thermal neutron capture cross section for ^134mCs. On the other hand, the resonance integral for ^134m+g Cs was 32% smaller than the experimental value by Steinnes et al.     

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.     

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 Westcott's 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.     

Measurements of Thermal Neutron Cross Section and Resonance Integral for 237Np(n, γ)238Np Reaction

Making use of a standard neutron spectrum field with a pure Maxwellian distribution, the thermal neutron cross section for the ²³⁷Np(n, γ)²³⁸Np reaction was measured at a neutron energy of 0.0253 eV by the activation method. The result is 158±3 b, which is obtained relative to the reference value of 98.65±0.09 b for the ¹⁹⁷Au(n, γ)¹⁹⁸Au reaction. Although the data in JENDL-3 is larger by about 15% than the present value, the recently revised data in JENDL-3.2 is close to the present. The ENDF/B-V, ENDF/B-VI, JEF-2 and Mughabghab's data are also larger by 7–15%. Old measurements are larger by 7–18% than the present data.

The resonance integral for the ²³⁷Np(n, γ)²³⁸Np reaction was also measured relative to the reference value of 1,550±28 b for the ¹⁹⁷Au(n, γ)¹⁹⁸Au reaction with a 1/E standard neutron spectrum field. By defining the Cd cut-off energy as 0.5 eV for the ²³⁷Np(n, γ)²³⁸Np reaction, the present resonance integral is 652 ± 24 b, which is in good agreement with the JENDL-3, -3.2, ENDF/B-V, -VI, JEF-2 and Mughabghab's data. However, most of the old experimental data are, in general, larger by 24–38% than the present measurement.     

Discussion of Data Difference Among Measured Thermal Neutron Cross Section of ~(135)Cs

Fission product 135Cs emits pure β rays, it has a half life of 2.3×106 a and a yield of 6.53% in 235U fission. It’s one of the most important nuclides for high-level waste disposal.     

Measurement Cross Section of D（d, γ）4He Reaction

The study of D（d, γ）^4He radioactive capture reactions at low energy is very important in the fusion diagnose, but it is hard to measure for small yield and serious background. In the present work, several measures were adapted. 1） A big NaI plastic anti Compton spectrometer for low yield of high energy γ-ray was used; 2） The method of the time of flight was employed for rejecting background neutrons and cosmic rays;     

Progress on Measurement of Neutron Capture Cross Section

In recent years,neutron capture cross sections of Ag,Hf and W relative to that of Au in the energy range from 10 to 100 keV have been measured withtime-of-flight method.Kinematically collimated neutrons were produced by ~7Li(p,n)~7Be reaction with the pulsed 2.5MV Van de Graaff accelerator.Captureevents were detected by two Moxon-Rae detectors.The resolution time of thewhole system,that is,the full-width at half-maximum(FWHM)of the promptgamma-ray peak was 1.60 ns.The total uncertainty is about 7% for most of thedata points.     

Measurement of Neutron Capture Cross Section for ~(71)Ga

The excitation curve for ~(71)Ga(n,γ)~(72)Ga reaction has been measured from 0.2 to 2.0 MeV by different authors. All of these measured cross sections are not in very good agreement with each other. To clarify the discrepancy it is necessary to measure the cross sections for ~(71)Ga(n,γ)~(72)Ga reaction again.     

Discussion of Data Difference Among Measured Thermal Neutron Cross Section of ^135Cs

“天光一号”系统采用诱导空间非相干（FEISI）和像传递技术实现了对靶平面的均匀辐照，但该技术并不能确保光束在激光传输路径上的近场分布均匀。虽然MOPA系统中大多数光学元件表面平均光通量不大于 1J／cm^2，     

Fast Neutron Dosimetry by 238U(n,2n) Reaction together with Thermal Neutron Dosimetry by 238U(n, γ) Reaction

The fast neutron flux in the central thimble of a TRIGA-II reactor was estimated by using the ²³⁸U(n,2n)²³⁷U reaction as flux monitor. The thermal neutron flux also was estimated by ²³⁸U(n,γ)→ ²³⁹Np and ²³²Th(n,γ)→ ²³³Pa reactions. The latter flux was further measured at the same time by γ-ray spectrometry of the product nuclides and by chemical separation and β counting with αemitting isotopes as tracer. The values of flux thus obtained were compared with those estimated from the amounts of ²⁸Al, ²⁷Mg and ²⁴Na respectively produced by the (n,γ), (n,p) and (n,α) reactions on ²⁷Al. Furthermore, for the first time, the effective cross section for the ²³⁸U(n,2n)²³⁷U reaction was estimated to be 2.8 b from a comparison with that for the ²⁷Al(n,α)²⁴Na reaction.     

Measurement Cross Section of D(d,γ)~4He Reaction

The study of D(d,γ)4He radioactive capture reactions at low energy is very important in the fusion diagnose[1], but it is hard to measure for small yield and serious background. In the present work, several     

Measurement of Cross Section for ~(92)Mo(n,p)~(92m)Nb Reaction and Deduction of Low Energy Neutron

Introduction Molybdenum is an important component of structural material for fission and future fusion reactors. It consists of seven isotopes. Therefore, fast neutrons can lead to many nuclear reactions. One of them is ~(92)Mo(n,p)~(92m)Nb reaction. Several authors published their data for this reaction, while most of the cross section determinations were     

Measurement of the ~(107)Ag(n,2n)~(106m)Ag Reaction Cross Section

The measurement of the ~(107)Ag(n,2n)~(106m)Ag reaction cross sections in theneutron energy range 13.50～14.73 MeV were done by the activation method with     

Differential Cross Section Measurement for the ~6Li(n,t)~4He Reaction

The differential cross sections and integrated cross sections of the 6Li(n,t)4He reaction were measured at 1.85 and 2.67 MeV by using a gridded ionization chamber. Neutrons were produced through the T(p,n)3He reaction. The absolute neutron flux was determined through the 238U(n,f) reaction. Present results are compared with existing data.     

Activation Cross Section Measurement for the Eu(n,γ) Reactions

The cross sections for ~(151)Eu(n,γ)~(152m)Eu, ~(151)Eu(n,γ)(152g)Eu and ~(153)Eu(n,γ)~(154)Eu reactions have been measured relatively to that of ~(197)Au for neutron energy from 22 to 1100 keV, using the activation technique. Neutrons were generated via the ~7Li(p,n)~7Be and T(p,n)~3He reaction with a 4.5 MV Van de Graaff accelerator at Peking University. The activities after irradiation were measured with two calibrated high resolution HPGe detectors. The accuracy of the measurement is 6～7%. The experiment results were compared with existing data.     

Cross Section Measurement of ~(64)Zn(n,p)~(64)Cu Reaction from 4 to 7 MeV

Introduction In the areas of activation and neutron scattering cross sections, there are still deficiencies in the nuclear database. Activation cross sections were found to be unsatisfactory in 83 of the 183 reactions reviewed. The excitation curve for ~(64)Zn(n,p)~(64)Cu reaction has been measured from threshold to 10 MeV by different authors. All of these measured cross sections are not in very good agreement with each other. To clarify the discrepancy it is necessary to measure the cross sections for ~(64)Zn(n,p)~(64)Cu reaction once again.     

Cross Section Measurement in Neutron Energy Range of 6～12 MeV

Introduction The cross section measurements in neutron energy range from 6 to 12 MeV for the reactions with low threshold are very important to obtain a whole excitation function and to make datum eveluation. But in this energy range, purely monoenergitic neutron source is not available, which make the measured data very few. And there is a serious effect of low energy neutrons on the activation cross section measurement. The correction for the effect of the low energy neutrons are not sufficient for some available data, which cause the published data largely discrepant.