Verification of a Triga Mark III MCNP model for neutron flux calculations

One of the concerns of any fuel configuration change in a research reactor is the ability to produce the same neutron flux. For assessing the impact of fuel changes in the Triga Mark III Mexican research reactor, a detailed model was developed with MCNP-5. The verification was done comparing the fluxes obtained with the ones of the manufacturer. Relative errors in the order of 1% were found in the irradiation core facilities. Using the same model but with the 17th core configuration, the neutron flux was calculated. Neutron flux differences between the initial and the 17th configuration are presented and discussed. Total flux calculated at the irradiation facilities was fitted into correlations providing a valuable way to predict neutron flux as function of height. The developed model can be used to evaluate further changes like the one done in 2012 in which the HEU fuel was replaced with LEU.