Proceedings of Annual / Fall Meetings of Atomic Energy Society of Japan

A Monte Carlo simulation technique using GEANT4 has been developed to simulate the response function and self-activity of LaBr₃:Ce detector. The internal activity of the LaBr₃:Ce crystal is due to the presence of an unstable isotope, ¹³⁸La and the contamination with ²²⁷Ac element. The simulation procedure and the preliminary result will present in the meeting

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Non-destructive assay (NDA) of ²³⁹Pu in spent nuclear fuel is possible using the integral resonance transmission (IRT) method. IRT measures the integral nuclear resonance fluorescence scattering on a mono-isotopic witness target following resonance absorption in nuclear fuel. Lowering the temperature of the witness target could substantially improve measurement sensitivity by narrowing the resonance width due to Doppler broadening. Calculations studying this effect will be presented.

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The ^6,7Li + n reactions are important not only from the basic interest but also from the application point of view. The ⁷Li nucleus is well described by the cluster model such as α + t. Therefore, it is necessary for us to treat the Li + n system with α + t + n model. In this study, cross sections for ⁷Li(n,n′) ⁷Li*→ α + t reactions are evaluated by using the CDCC, in which we adopt microscopic wave functions of ⁷Li with the α + t model. The advantage of this method is to obtain not only elastic and inelastic cross sections but also neutron spectra within the same framework. We first calculate the elastic cross sections for the ⁷Li + n scatterings with the complex Jeukenne-Lejeune-Mahaux effective nucleon-nucleon (JLM) interaction. In the present analyses, it is found that the elastic cross sections for incident energies at 11.0, 13.0, 14.1 and 18.0 MeV can be reproduced by the present cluster model with one normalization parameter for the imaginary part of the JLM effective interaction. Next, we calculate the inelastic scattering cross sections and the neutron spectra. The calculated inelastic cross sections of the 7/2⁻ resonance states and neutron spectra for ⁷Li breakup into continuum states are in good agreement with experimental data. From those results, we conclude that the CDCC method with the JLM is very powerful for the data evaluation of the ⁷Li(n,n′) reactions.

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LaBr₃:Ce detector array (LABRA) has been constructed to measure the nuclear resonance fluorescence (NRF) excitations from special nuclear materials (SNM). NRF is an active interrogation technique for assaying SNM that provides a unique signature to identify isotopic composition of an object nondestructively. At the meeting, we will present the performance of the LABRA to measure NRF excitation from ²³⁵U using quasi-mono-energetic g-ray beam at the HIgS facility.

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