Calculating the effective delayed neutron fraction using Monte Carlotechniques

摘要

We present a true Monte Carlo estimator of the effective delayed neutronrnfraction βeff. The advantage of this method is that by using the physics at thern. Microscopic level, it obviates the need for adjoint calculations, withoutrnmaking any approximations. We have implemented this estimator intornMCNP. In a standard keff calculation, the code now reports a βeff value. Thernmethod does not slow down the code by more than 0.5%. We define anrnextensive benchmark set for βeff, which we use to test our method, and tworn, known approximate methods. Our method reproduces all experimentalrnvalues.