Fission probability density functions for super prompt criticality accident analysis in weakly coupled systems by integral kinetic model

Kinetic analysis in criticality accident is necessary for the estimation of the integral power and the dose. The analysis must be performed even for the geometry of several regions which are weakly coupled, i.e. each region is apart from other regions or/and moderating material exists between the regions. A kinetic analysis method for weakly coupled systems has been developed to analyze the first pulse in super prompt criticality accidents. In the method, time dependent fission probability density functions after a fission in each region are calculated by Monte Carlo method from the time between the collisions. By using the fission probability density functions, kinetic behavior of each region can be calculated. The difference of the functions between the different systems is discussed based on the difference of compositions and geometry of the systems. (author)