Estimation of error propagation in Monte-Carlo burnup calculations

A formulation has been established to estimate the error propagation in Mon te-Carlo burnup calculations. The uncertainties in cross sections and the s tatistical errors in Monte-Carlo calculations are considered as error sourc es, and the error propagation of number densities of individual nuclides ov er a burnup period is formulated. The present formulation is applied to the burnup calculation of a simplified fast reactor core. The components of th e errors in number densities due to tie statistical error are lip to 0.92% even when the history number is small as 10(x1). On the other hand: the com ponents due to the cross section error are about 2-5% for the number densit ies of U-235, Pu-239, Pu-2.10, Pu-2.11, and Pu-2.12, and about 7.3% for the fission product. Thus the contribution is mainly due to the cross section errors. The error propagation of the number densities due to the statistica l errors at individual burnup steps is investigated by dividing the burnup period into two steps. The error propagation is not serious for the problem treated here because the component due to the statistical error is much sm aller than that due to the cross section error.