Reactor Neutron Activation Cross Sections for a Number of Elements

Covariance analysis on the thermal neutron capture cross sections using an Am-Be neutron source

We measured the thermal cross sections of 71Ga(n, γ)72Ga using an Am-Be neutron source having strength of 4 × 107 neutrons/sec using the two monitor reactions 197Au(n, γ)198Au and 55Mn(n, γ)56Mn, and obtained 4.07±0.27 b and 3.97±0.31 b as the values measured relative to Au and Mn neutron captures, respectively. We constructed their covariance matrix by taking into account the correlation of parameters which are not independent in derivation of these two thermal cross sections (e.g., Ga sample weight, decay data of 72Ga, detector efficiency of γ -ray emitted from 72Ga). The off-diagonal weighted mean of the two cross sections 4.04±0.27 b was derived from the two thermal cross sections and their covariance matrix.

Neutron capture cross section measurements and theoretical calculation for the 186W(n,γ)187W reaction

Neutron capture cross section (σ 0) and resonance integral (I 0) of the reaction 186W(n,γ)187W were measured experimentally using the research reactor (ETRR-2) and an Am–Be neutron source, also calculated using TALYS-1.6 code. The present results of σ 0 are (39.08±2.6, 38.75±0.98 and 38.33 barn) and I 0 are (418.5±74, 439.3±36 and 445.5 barn) by using the reactor, neutron source and TALYS-1.6, respectively. The present results are in acceptable agreement with most of the previous experimental and evaluated data as well as the theoretical calculations.

41K(n,γ)42K thermal and resonance integral cross section measurements

We measured the41K thermal neutron absorption and resonance integral cross sections after the irradiation of KNO3samples near the core of the IEA-R1 IPEN pool-type research reactor. Bare and cadmium-covered targets were irradiated in pairs with Au-Al alloy flux-monitors. The residual activities were measured by gamma-ray spectroscopy with a HPGe detector, with special care to avoid the42K decayβ-emission effects on the spectra. The gamma-ray self-absorption was corrected with the help of MCNP simulations. We applied the Westcott formalism in the average neutron flux determination and calculated the depression coefficients for thermal and epithermal neutrons due to the sample thickness with analytical approximations. We obtained 1.57(4) b and 1.02(4) b, for thermal and resonance integral cross sections, respectively, with correlation coefficient equal to 0.39.

Neutron capture cross-section measurement for the 186W(n,gamma)187W reaction at 0.0536eV energy

The thermal neutron-induced activation cross section for the (186)W(n,gamma)(187)W reaction was measured at 0.0536eV neutron energy using TRIGA Mark-II research reactor, Atomic Energy Research Establishment, Savar, Dhaka, Bangladesh. The (197)Au(n,gamma)(198)Au monitor reaction induced in a high-purity gold foil was used to determine the effective neutron beam intensity. The activities induced in sample and monitor foils were measured nondestructively by a high-resolution HPGe gamma-ray detector. The present experimental cross-section value is the first one at 0.0536eV. The obtained new cross section that amounts to 26.6+/-1.6b is 2% higher than the recently reported data in ENDF/B-VII and 5% lower than that of JENDL-3.3.

Factor for correcting the ruthenium interference in instrumental neutron activation analysis of barium in uraniferous samples

The fission spectral interference of ruthenium on the instrumental neutron activation analysis of barium in samples containing uranium is extensively discussed. In particular the dependence of the correction factor on the phi epi/phi th ratio is studied. An excellent agreement between experimental and calculated values is achieved. A procedure is suggested for the resolution of multiple interferences in the general case where uranium, barium and/or ruthenium are present in samples to be analysed.