Abstract
A new method has been established to calculate sensitivity coefficients of cell parameters based on generalized perturbation theory using the collision probability method. The proposed method does not require the calculation of the changes of collision probabilities due to cross section changes, so it is as powerful as the commonly used generalized perturbation theory in diffusion theory, We demonstrate the validity of the method by comparing the calculated sensitivity coefficients with those obtained from the direct cell calculations. As an application, we calculate the sensitivity coefficients of neutronic properties in cells with different moderator to fuel volume ratios, and discuss the physical meaning of the difference between the sensitivity coefficients.
With the analysis of hypothetical accident in a nuclear power reactor, a molten fuel and coolant interaction (MFCI) leads a vapor explosion under certain circumstances. The author has performed fundamental experiment on the vapor explosion with a mass of grains of certain particle sizes which simulate the molten fuel fragments, to verify the relation between the particle size and the magnitude of pressure pulses.
The standard temperatures of water and liquid nitrogen used as cold liquid set prior to the test are 25°C and 77 K respectively, and that of grains (SiC) are 600°C for the former and 25°C for the latter experiments. For both experiments, the maximum pressure pulse has the greatest value at the grain size of 0.27 mmφ. This value of diameter agrees approximately with the median of the size distribution of the fragments measured in some vapor explosion experiments with a hot molten metal.
In the results of using water as cold liquid, boiling pressure traces show the oscillations of higher frequency than 100 Hz with particle sizes ranging 0.20.5 mm. The initial temperatures of grains and water little effect on generating such oscillations as far as it is tested in this study.
