Multigroup coupled neutron-gamma cross-section library for deterministic and Monte Carlo borehole logging analysis

A special purpose multigroup cross-section library optimized for nuclides and reactions arising in nuclear oil well logging was prepared for use in deterministic and Monte Carlo transport codes. The library is based on the recent ENDF/B-VI.8 evaluation, which includes among others improved oxygen and chlorine cross-sections. A 175 neutron and 45 gamma ray energy group structure was selected in a way to take into account the requirements of oil well logging applications. This library is expected to improve the prediction of the neutron and gamma spectra at the detector positions of the logging tool and its use for the interpretation of the Carbon/Oxygen (C/O) neutron logging measurements in boreholes was studied. For the Monte Carlo codes this library can be useful in particular in calculations requiring multigroup cross sections, like adjoint or MIDWAY methods. Furthermore, comparison of deterministic and Monte Carlo calculations using same or similar cross sections can reveal the uncertainty linked to the computational method and model. Preparation and testing of this library is described.