[en] The fission gas release code MINIPAT has been employed in a parametric survey to study the effect on gas release values, during the course of an isothermal irradiation, of varying the values of a number of items of input data. These include the initial grain size, diffusion coefficients, gas pressure, the extent of gas atom re-solution from grain boundaries and the effect of a temperature step. The sensitivity of gas release values with variations in the diffusion coefficients is demonstrated. Gas releases decrease with increasing grain size, the quasi-equilibrium grain diameter attained during irradiation being the operative factor. Release values at constant temperature decrease with increasing rating; this is due to the interaction of a number of factors, which either increase or decrease the gas release. These results have been compared with some obtained from similar calculations, using another gas release model, CORES, which considers in greater detail the way gas is transferred from grain surfaces to the plenum. The reasonably good agreement obtained suggests that despite its simplicity, MINIPAT is able to predict with reasonable confidence gas release values from thermal reactor pins irradiated under normal operating conditions. (author)