New Monte Carlo Simulations of the LLNL Pulsed-sphere Experiments PDF Download

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Languages : en
Pages : 119

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Book Description
From the late 1960s to about 1985, the Pulsed-Sphere Program at Lawrence Livermore National Laboratory (LLNL) was carried out to measure 14-MeV neutron leakage spectra from target spheres made out of various elements, compounds, and mixtures Data from these experiments have been and continue to be fundamental in the evaluation of neutron Monte Carlo transport codes and cross section data libraries In addition, the data provide important integral information for stockpile stewardship, fusion technology, neutron therapy, and other applications Therefore, comparisons between computer Monte Carlo simulations and the results of these experiments are pivotal for the integral testing of processed nuclear data libraries and transport codes Fortunately, a large subset of data from the pulsed-sphere program (some 70 experiments) is available as a computer file called disp93in Furthermore, in the past few years, there has been a remarkable improvement in computer performance that allows for more realistic simulations by Monte Carlo codes such as TART 4 Previous TART simulations of the pulsed-sphere experiments were performed using simplified models with relatively small numbers of histories and very large solid angle detectors to offset the limitations in computer power. Also, not all the TART input files were created with the same level of detail For example, some input files included the air around the sphere while others did not These factors prompted a study to simulate in more detail all of the available pulsed-sphere experiments using the Monte Carlo transport code, TART, and the LLNL evaluated neutron data library, ENDL The timing of this study is significant because many years have passed since those experiments were done, and only a few people who participated in them are still working at LLNL Their help has been essential for an accurate documentation of the experiments For the Stewardship Program it is important to preserve and make use of as much of the data as possible, because it represents a unique resource and an enormous effort that would be very costly to reproduce The initial part of this study consisted of an analysis of the experimental setup and neutron source characteristics necessary to create the foundation for a TART input file The next task was to create the input files for the various experiments by incorporating particular settings, such as flight path, sphere materials and dimension, etc, to the basic TART input The results of the TART simulations of these experiments will be used to help assess the quality of evaluated data currently in ENDL Further, other nuclear libraries, e g, ENDF/B-VI, JENDL-3, and JEF-2, will be used in the Monte Carlo simulations after being reformatted for TART and other Laboratory codes Finally, this work will be part of the integral check of the new evaluations being prepared for the Stewardship Barn Book by the LLNL Nuclear Data Group.