Self-shielding effects in a tungsten layer in a fusion device

The impact of geometrical modelling and energy treatment on neutronics and activation results for materials with giant resonances, such as tungsten, i s significant. Three-dimensional (3-D) neutronics calculations have been pe rformed using the Monte Carlo codes MCNP and TRIPOLI to determine the self- shielding effect in tungsten layers in fusion environment. While excellent agreement exists between the two Monte Carlo results, the W-187 production rate is overestimated by about a factor of 4 when a homogenised model is us ed with multi-group sampling. To correctly predict reaction rates in tungst en, 3-D continuous energy Monte Carlo calculations with layered heterogeneo us modelling should be used. An effective reaction rate derived from the Mo nte Carlo pointwise results, which accounts accurately for resonance absorp tion effects, which should be used in the subsequent activation calculation . (C) 1999 Elsevier Science S.A. All rights reserved.