TENDL random files for Pu-239 and the Jezebel experiment with the Halfway Monte Carlo method

Sammanfattning

The aim of this thesis is to simulate how uncertainties propagate in the Jezebel experiment. Jezebel was an experiment performed by the Los Alamos National Laboratory in 1954-1955 and consisted of three main parts made of mostly 239Pu with the aim of determining the critical mass of this isotope. A lot of data was collected and is still used in research today; an example being the quest to determine the critical mass of 239Pu which has been revisited multiple times. One way the data can be used is for simulations of nuclear assemblies and Monte Carlo methods are one approach to simulate nuclear physics. The Halfway Monte Carlo method uses pre-calculated sensitivity matrices, unique for each reaction channel and geometry, in order to simulate neutron transport and propagate uncertainties in nuclear data. In this thesis we use sensitivity matrices constructed from Jezebel data in order to propagate uncertainties in cross section data to the uncertainty in the criticality of the assembly, ∆keff. Here, criticality being whether the reactions sustain themselves or not. Another purpose of this study is to generalize an existing code to work with any compatible dataset, i.e. random files and sensitivity matrices. The code now functions with a configuration file containing all of the relevant directories and settings. We have also been able to obtain values of ∆keff for four different configurations of Jezebel with four reaction channels for each configuration. However, comparing the results with results from Lady Godiva and other Jezebel results, the results of this thesis seem implausible and should be re-evaluated if used in further research. The issue appears to be the set of sensitivity matrices used, which yielded large full-width-at-half-maximum (FWHM) values in the ∆keff histograms compared to Lady Godiva and other Jezebel results.