Applications of Monte Carlo and discrete ordinates techniques to PWR cavity shield design

The development and application of calculational techniques needed to establish the radiation shielding effectiveness of proposed shield designs for the annular cavity between PWR reactor vessels and the primary shield is presented. A computer code, MQT, developed at Combustion Engineering, Inc., to improve 2D S/sub N/ calculations by changing angular quadratures and/or spatial meshes between successive steps of bootstrapped S/sub N/ calculations is described. The development of MQT and its application has shown the need for high order asymmetric quadrature sets for the analysis of annular shields with small gaps. Monte Carlo calculations have been improved through the use of an annular surface source, the addition of an azimuthal dependence to that source, and the limitation of the number of thermal neutron interactions per history. A method has been developed using MQT to identify important streaming pathways in 2D and 3D calculations