The space dependent treatment of pebble bed reactor fuel management using the burnup code FRIZLE

Abstract

An outline is given of the model used in the FRIZLE code complex in order to treat the two dimensional space dependent fuel management problem. The model is an extension of the zero dimensional burnup model, which allows the linking up of some existing codes. The code complex is capable of determining, for all envisaged pebble bed reactor fuel management schemes, the core power distribution based on the calculated average composition and temperature in specified core zones. The code is used for assessing several practicable management schemes applicable to a pebble bed reactor. These show that the same achievable burnup is obtained as with the zero dimensional method, based on the assumption of infinite recirculation. However, because of the markedly different core power distributions produced by various schemes, it is more important to arrange the management to reduce the core size and capital cost, than to increase burnup. Details are given of the code complex and data requirements.