APPLICATION OF THE DIRECT STATISTICAL APPROACH ON A MULTISURFACE SPLITTING PROBLEM IN MONTE CARLO CALCULATIONS.

The direct statistical approach was used recently to obtain analytic expressions for the second moment and the average time per source particle in a general case of multisurface geometry splitting. A practical algorithm is given for the calculation of the second moment as a function of the splitting parameters on the surfaces. The algorithm is used to calculate an explicit expression for the efficiency in a problem involving streaming of neutrons in a straight section of a concentric coolant pipe of a fast reactor. The results are used to obtain the optimum splitting range on four surfaces.