The purpose of this work is to simulate the fuel burnup of the Missouri S&T; Reactor. This work was accomplished using the Monte Carlo software MCNP. The primary core configurations of MSTR were modeled and the power history was used to determine the input parameters for the burnup simulation. These simulations were run to determine the burnup for each fuel element used in the core of MSTR.

With these simulations, the new predicted isotopic compositions were added into the model. New core configurations were determined, and the burnup corrected model was used to predict the excess reactivity and control rod worth of the three shim rods in the new configurations labeled 125 and 126. The reactor core was arranged to these configurations in order to determine excess reactivity and control rod worth for the shim rods. When core 125 was tested, the reactor could not attain criticality without external source, which was predicted by the simulations. Core 126 had sufficient excess criticality to support measurement. Those measurements had inconsistent results, and indicated methodology errors.

Based on this work, it is recommended to revise the code for temperature gradients and Doppler effects. The experimental methodology for the rod drop tests should also be revised to ensure the methods are applicable to core parameters. These corrections allow the model and the reactor itself to better reflect each other so that the predictions by MCNP will better reflect the measurements at MSTR.