Testing the Lawrence Livermore National Laboratory SImulation of Neutron and Gamma Ray Emission from Fission and Photofission in MCNPX 2.7.0
Open Access
- Author:
- Weldon, Robert Allen
- Area of Honors:
- Physics
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Jorge Osvaldo Sofo, Thesis Supervisor
Dr. Richard Wallace Robinett, Thesis Honors Advisor
Michael Fensin, Thesis Supervisor - Keywords:
- MCNP
Physics
Nuclear Engineering - Abstract:
- MCNP is the most widely used particle transport code by nuclear engineers throughout the world, and is constantly being upgraded. Lawrence Livermore National Laboratory (LLNL) developed a physics model for the simulation of neutron and gamma ray emission from fission and photofission that was included in MCNPX 2.7.B in 2009. The LLNL multiplicity capability provided the ability for MCNPX to simulate neutron and gamma-ray distributions for neutron induced, spontaneous and photonuclear fission reactions. This thesis examines and supports the accuracy of LLNL’s physics model by comparison with experiment and similar physics models already in MCNP. The components of the LLNL capability tested included the multiplicity capability, the four different multiplicity options, and the correlation options. The LLNL multiplicity capability was tested and compared with experiment. The percent difference between the capability and experiment was less than 6% in the first five multiplicities for the neutron induced fission of U-233, U-235, Pu-239, and Pu-241. For the spontaneous fission of U-238, Pu-238, Pu-240, Cm-242 and Cm-244, the percent error was less than 3% in the first five multiplicities. The testing of the five FISM options with the LLNL capability showed LLNL as having the closest results to consensus experimental data for neutron induced fission for U-235 with a percent difference in the first five multiplicities of less than 8%. The four multiplicity options tested showed general agreement with experiment. The average value for the energy of fission neutrons induced by thermal neutrons was 2.06 MeV for U-235. This has a percent difference of 3% from the accepted value of 2 MeV. The average value of photons resulting from a thermally induced fission reaction was 6.00 MeV with a percent difference of 14% from the average experimental value of 7 MeV. The correlation options tested showed agreement between Beck and Vogt.