An evaluation of Super Phenix 1 core reactivity levels using cross-section adjustment techniques in diffusion theory and a comparison with measurement

The use of the diffusion theory approximation offers a relatively inexpensive method for the estimation of fast reactor core reactivity levels. However, for accurate results, calculated reactivities need to be corrected due to the nature of the approximation as well as the limited spatial and energetic resolution with which whole core geometries can be practically represented. Rowlands has proposed two separate cross-section adjustment techniques to obviate the need for reactivity corrections due to the effects of: - detailed heterogeneous control rod geometry - the over prediction of neutron streaming in rod follower channels made by diffusion theory when the diffusion coefficient is defined as 1/3ΣΤ. This paper examines the performance of these cross-section adjustment techniques for the prediction of core reactivity levels and absorber rod worths measured in the start up programme of the Super Phenix 1 (SPX1) Fast Reactor