## Estimation of fission source bias in Monte Carlo eigenvalue calculations

Monte Carlo eigenvalue calculations using a fixed number of histories per generation are biased. Previous work has shown that the bias in eigenvalue is generally smaller than observed standard deviations. In this paper, the authors propose a method for bounding [delta][psi] the bias in the unnormalized fission source. In addition, the authors construct a plausibility argument suggesting that the bias is generally insignificant. Results presented are for discretized diffusion calculations based on a Monte Carlo-generated source. Additional calculations have been run for true transport problems using a very fast, but more conventional, Monte Carlo code.