Exposure buildup factors of UO₂ using the Monte Carlo method

When the gamma dose rate around an irradiated nuclear reactor fuel element is calculated, it is important to know the attenuating characteristics of the fuel element itself, one of them being the buildup factor. Exposure buildup factors of uranium dioxide (UO₂) for ten gamma-ray energies (0.050 to 10.0 MeV) have been computed for ten material thicknesses (0.5 to 10.0 mean free paths) using the MCNP code. The accuracy of the MCNP model was checked by computing the buildup factors of oxygen and uranium and comparing these results with the data given in the literature for these elements. The results indicate that the UO₂ exposure buildup factors, for the energies and distances studied, are close to those of uranium.