Neutron and gamma ray dose studies in CAGR instrumentation and fuel components

Monte Carlo methods used within the United Kingdom for energy deposition assessments have sufficient flexibility to model a wide variety of reactor problems both in terms of geometry and nuclear data. However the modelling must also extend to the correct dosimetric representation of the system under examination. The assumption of energy deposition at a point which is inherent in all transport simulations of this kind is shown not to be valid when considering core instrumentation and small components, when secondary particle ranges become comparable with their dimensions. To illustrate this effect, calculations including the effect of secondary electron transport processes for CAGR calorimeters and burnable poison fuel components have been compared with standard dose evaluations and important differences have been found. (Auth.)