ANALYTIC SCORE DISTRIBUTIONS FOR A SPATIALLY CONTINUOUS TRIDIRECTIONAL MONTE-CARLO TRANSPORT PROBLEM

The interpretation of the statistical error estimates produced by Mont e Carlo transport codes is still somewhat of an art. Empirically, ther e are variance reduction techniques whose error estimates are almost a lways reliable, and there are variance reduction techniques whose erro r estimates are often unreliable. Unreliable error estimates usually r esult from inadequate targe-score sampling from the score distribution 's tail. Statisticians believe that more accurate confidence interval statements are possible if the general nature of the score distributio n can be characterized. Here, the analytic score distribution for the exponential transform applied to a simple, spatially continuous Monte Carlo transport problem is provided. Anisotropic scattering and implic it capture are included in the theory. In large part, the analytic sco re distributions that are derived provide the basis for the ten new st atistical quality checks in MCNP.