Effective Neutron Capture Cross Section Research Articles

Reactor production of promethium-147

In this paper, we describe the 147Pm production yields and level of impurities from several targets that consisted of milligram quantities of highly enriched 146Nd oxide irradiated at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory for durations ranging from 24 to 180 h. A comparison between theoretical and experimental data are also presented, and attempts were made to empirically evaluate the neutron capture cross-sections of 41.3-d 148mPm and 5.4-d 148gPm. For a one-cycle irradiation (~24 days), 147Pm yield reaches a maximum value of 101.8 MBq/mg (2.75 mCi/mg) at 60 days after the end of bombardment. Because of large neutron capture cross-sections of 147Pm, the yield of 147Pm does not significantly increase with longer irradiation. Our estimates of the thermal neutron capture cross-section and resonance integral for 146Nd at 1.48 ± 0.05 b and 2.56 ± 0.25 b, respectively, were consistent with the reported values. The effective neutron capture cross-section of 147Pm to 148mPm was 53.3 ± 2.7 b–a factor of 2 lower than the 98.7 ± 6.5 b calculated from reported cross-sections. The measured σeff to the ground state (5.37-d 148gPm) was 82.0 ± 4.1 b; ~34% lower than the value of 139 ± 10 b calculated from reported cross-sections. In this work, we also describe the development of a chemical process based on extraction and ion-exchange chromatography for separation of 147Pm from milligram quantities of 146Nd and other impurities. Sequential separation of Pm from the Nd target and from other radioisotopic impurities (153Gd and 154&155Eu, 192Ir, and 60Co) was achieved using a LN extraction resin in HCl media followed by further purification of Pm from 60Co and 192Ir using a low cross-linking cation exchange resin. Based on these data, we estimated that two rounds of purification under our experimental conditions can provide a mass separation factor of >104 between Pm and Nd. Our data indicate that curie quantities of 147Pm with suitable chemical and radioisotopic purity for applications in beta voltaic batteries can be produced by irradiating gram quantities of highly enriched 146Nd in the flux trap of HFIR for one cycle.

MANTRA: An Integral Reactor Physics Experiment to Infer the Neutron Capture Cross Sections of Actinides and Fission Products in Fast and Epithermal Spectra

This paper presents an update of an on-going collaborative INL-ANL-ISU integral reactor physics experiment whose objective is to infer the effective neutron capture cross sections for most of the actinides of importance for reactor physics and fuel cycle studies in both fast and epithermal spectra. Some fission products are also being considered. The principle of the experiment is to irradiate very pure actinide samples in the Advanced Test Reactor at INL and, after a given time, determine the amount of the different transmutation products. The determination of the nuclide densities before and after neutron irradiation together with the neutron fluence will allow inference of effective neutron capture cross-sections in different neutron spectra.

MANTRA: An Integral Reactor Physics Experiment to Infer Actinide Capture Cross-Sections from Thorium to Californium with Accelerator Mass Spectrometry

The principle of the proposed experiment is to irradiate very pure actinide samples in the Advanced Test Reactor at INL and, after a given time, determine the amount of the different transmutation products. The determination of the nuclide densities before and after neutron irradiation will allow inference of effective neutron capture cross-sections. This approach has been used in the past and the novelty of this experiment is that the atom densities of the different transmutation products will be determined using the Accelerator Mass Spectrometry technique at the ATLAS facility located at ANL. It is currently planned to irradiate the following isotopes: 232Th, 235U, 236U, 238U, 237Np, 238Pu, 239Pu, 240Pu, 241Pu, 242Pu, 241Am, 243Am, 244Cm and 248Cm.

112Cd(n, γ)113mCd反応の実効中性子捕獲断面積測定

112Cd(n, γ)113mCd反応の実効中性子捕獲断面積測定

Time variability of α from realistic models of Oklo reactors

We reanalyze Oklo {sup 149}Sm data using realistic models of the natural nuclear reactors. Disagreements among recent Oklo determinations of the time evolution of {alpha}, the electromagnetic fine structure constant, are shown to be due to different reactor models, which led to different neutron spectra used in the calculations. We use known Oklo reactor epithermal spectral indices as criteria for selecting realistic reactor models. Two Oklo reactors, RZ2 and RZ10, were modeled with MCNP. The resulting neutron spectra were used to calculate the change in the {sup 149}Sm effective neutron capture cross section as a function of a possible shift in the energy of the 97.3-meV resonance. We independently deduce ancient {sup 149}Sm effective cross sections and use these values to set limits on the time variation of {alpha}. Our study resolves a contradictory situation with previous Oklo {alpha} results. Our suggested 2{sigma} bound on a possible time variation of {alpha} over 2 billion years is stringent: -0.11{<=}{delta}{alpha}/{alpha}{<=}0.24, in units of 10{sup -7}, but model dependent in that it assumes only {alpha} has varied over time.

Prospective Large-Scale Transmutation of Fission Iodine

The effective neutron capture cross section of 129I was determined at irradiation of 11.3±0.55 mg of KI (83.5% 129I and 16.5% 127I) for 6 h in a V10 channel of the beryllium reflector of VVR-M water-cooled water-moderated reactor (PINF) at average power of 12 MW. The neutron spectrum was measured by the activation procedure. For this purpose a series of thermal, resonance, and threshold detectors and a weighed portion of iodine were irradiated. The neutron spectrum was restored from the γ-ray spectra of these samples by the best fit procedure. The neutron capture cross section of 129I, averaged over the neutron spectrum in the beryllium reflector of VVR-M reactor, was 17.8±3.2 b. The activities of products formed from a model 127I portion of iodine were irradiated. The neutron spectrum was restored from the γ-ray spectra of these samplesby the best fit procedure. The neutron capture cross section of 129I, averaged over the neutron spectrum in theberyllium reflector of VVR-M reactor, was 17.8±3.2 b. The activities of products formed from a model 127Isample irradiated in a loop of VVR-M reactor under steady-state conditions were calculated.

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. The of 134Cs obtained is 140.6±8.5 barns and agrees with the value measured by Bayly et al.with a mass analysis method within the limits of error.

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

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

Contributionàl'étude de la température dans les réacteurs fossiles d'Oklo par la mesure du rapport isotopique du lutétium

The measurement of the 176Lu/ 175Lu ratio in the Oklo uranium ore zones where nuclear reactions have been identified, can be related to the average equilibrium temperature of the neutrons at the time of the nuclear reactions; indeed, the effective neutron capture cross section of the isotope 176Lu is particularly sensitive to temperature. A simple model has been developed to calculate the temperature. The results obtained on seven samples from three reactor zones are presented. From six samples an average value of 280 ± 50°C is obtained, the corresponding integrated neutron flux τ varies from 0.06 × 10 20 to 6 × 10 20 n/cm 2 and 176Lu/ 175Lu from 0.0254 to 0.0054. From one sample a very high temperature is obtained: T > 1000°C, τ = 4.4 × 10 20n/cm 2, 176Lu/ 175Lu= 0.0032 . The validity of this result is sharply dependent on the relative stability of uranium and the rare earths during and after the nuclear reactions; so, it can be noticed that the two samples giving the highest temperatures present a surprisingly high enrichment in heavy rare earth elements.

The thermal neutron capture cross-sections and resonance capture integrals of 44Ca, 62Ni, 168Yb, 174Yb, 169Tm, and 203Tl

The effective neutron capture cross-sections of the isotopes 44Ca, 62Ni, 168Yb, 174Yb, 169Tm and 203Tl have been measured by the activation method. By irradiating samples with and without cadmium covers, and by assuming a 1/v dependence in the sub-cadmium region, the 2200 m/sec cross-sections and the resonance integrals have been calculated using the Westcott convention. The values for σ o are 44Ca 0·88±0·01 barns, 62Ni 14·2±0·3 barns, 168Yb 3470±50 barns, 174Yb 141±2 barns, 169Tm 106±3 barns and 203Tl 8·9±0·4 barns. The resonance integrals (Σ) are 44Ca 0·56±0·01 e barns, 62Ni 9·6±3·5 barns, 168Yb 21000±4200 barns, 174Yb 68·6±7·2 barns 169Tm 2240±130 barns and 203Tl 349±17 barns. All measurements are relative to a 59Co cross-section of 37·5 barns and a 59Co resonance integral of 69·9 barns. Errors are experimental and quoted at the 95 per cent confidence level.

The thermal neutron capture cross section and resonance capture integral of 35Cl for ( n, γ) and ( n, p) reactions

The effective neutron capture cross section of 35Cl for ( n, γ) and ( n, p) reactions has been measured by the activation method. By irradiating samples in a reactor with and without a cadmium cover and by assuming a 1/v dependence in the sub-cadmium region, the 2200 m/sec cross sections and the resonance integrals for both reactions have been calculated using the Westcott convention. The values found for the ( n, γ) reaction are α 0=41·8±1·2 barns and Σ=<20 barns. For the ( n, p) reaction σ 0=0·492±0·014 barns and Σ=0·369±0·015 barns. All measurements are relative to a 59Co cross section of 37·5 barns and a cobalt-59 resonance integral of 69·9 barns.

The thermal neutron cross-sections and resonance integrals of 64Zn, 74Se, 85Rb and 98Mo

The effective neutron capture cross-sections of the isotopes 64Zn, 74Se, 85Rb and 98Mo have been measured by an activation method. By irradiating samples with and without cadmium covers and by using the Westcott convention the 2200 m/sec cross-sections and the resonance integrals (including the 1/ v part) have been calculated. The respective values for each isotope are: 64Zn, 0·821 ± 0·011 and 1·34 ± 0·06 barns; 74Se, 66·8 ± 1·4 and 589 ± 12 barns; 85Rb, 0·396 ± 0·005 and 24·7 ± 1·7 barns; 98Mo, 0·137 ± 0·006 and 6·79 ± 0·42 barns. The measurements are relative to a 59Co cross-section of 37·5 barns and quoted errors are at the 95 per cent confidence level.

The thermal neutron cross-sections and resonance integrals of the europium isotopes

The effective neutron capture cross-sections of 151Eu and 153Eu have been measured by an activation method with and without a cadmium cover. Using the Westcott convention the 2200 m/sec cross-sections and the resonance integrals Σ and Σ′ have been calculated assuming the cross-sections obey a 1/ν law in the thermal region. The measured cross-section value of 2951 ± 85 barn for the production of 152 m Eu (9·3 hr half-life) is based on a cross-section of 98·8 barn for 197Au. The values of 4410 ± 66 barn for the production of 152Eu (12·4 yr half-life) and 639 ± 7 barn for the production of 154Eu are based on a cross-section of 37·5 for 59Co. The respective resonance integrals are 11,410 ± 450 barn, 3847 ± 270 barn abd 3887 ± 62 barn. Quoted errors are at the 95 per cent confidence level. The effect of neutron self shielding on the measurements has been determined, and sample weights were chosen to reduce this effect to negligible proportions.

Thermal neutron capture cross section and resonance capture integral of the lanthanide nuclei 14Ce, 142Ce, 146Nd, 158Nd, 150Nd and 159Tb

The thermal neutron capture cross sections σ th and the resonance capture integral I 0 for some lanthanide nuclei are measured by an activation method. Thin gold foils ( σ 0 = 98·8 barn, I 0 = 1558 barn) were used as flux monitors. The values found for σ th and I 0 are as follows: 140Ce 142Ce 146Nd 158Nd 150Nd 159Tb δth(barn) 0.54±0.04 0.94±0.09 1.3±0.1 2.5±0.2 1.0±0.2 22±2 I 0(barn) 0.49±0.05 1.6±0.2 3.0±0.3 14±2 14±4 450±50 The resonance integrals for 142Ce, 146Nd and 150Nd have not been published previously. In addition are given the effective neutron capture cross sections σ eff in the JEEP reactor at JENER, Kjeller.

The thermal neutron capture cross-section and resonance capture integral of 22Na

The effective neutron capture cross-section of 22Na has been measured by a depletion method with and without a cadmium cover. Using the Westcott convention the 2200-m/sec cross-section has been calculated as 35,900 ± 1200 barn and the resonance integrals Σ and Σ′ have been calculated as 203,000 ± 27,000 barn and 191,000 ± 25,000 barn respectively. In the calculations it was assumed that the cross-section of 22Na followed the “1/v law” in the thermal region. All measurements are relative to a 59Co cross-section of 37·5 barn, and the quoted errors are at the 95 per cent confidence level.

EFFECTIVE AND THERMAL NEUTRON CAPTURE CROSS SECTION AND RESONANCE CAPTURE INTEGRAL OF Pr-143

The effective neutron capture cross section,[Formula: see text]; the 2200 meters/sec neutron capture cross section, σ0, and the resonance capture integral, RI, of Pr-143 have been measured by an activation method. The values are: [Formula: see text], σ0 = 89 ± 10, and RI = 190 ± 25 barns respectively. The neutron fluxes have been measured with cobalt monitors. All these values have been calculated according to the Westcott convention, which has been outlined insofar as it can be applied to activation work.

Effective Capture Cross Section of Pa-233 for Thermal Reactor Neutrons

Thorium metal was irradiated in the thermal neutron flux of the Low Intensity Test Reactor and of a graphite reactor. From mass spectrographic analysis of the U234 content and assumption of an effective capture cross section (including epithermal as well as thermal neutron capture) of 8.0 barns for Th232, the effective neutron capture cross section of Pa233 for thermal reactor neutrons was determined to be 140 ± 20 barns.