Power distribution unfolding on the basis of in-core rhodium powered detector readings

The task of unfolding of core power distribution for WWER reactors consists of processing of Self Powered Neutron Detector measurements to obtain estimated values for the uninstrumented assemblies. The method described in the report relies on 3-D power distributions calculated with BIPR-5 code and adjusted to instrumented assemblies to reproduce SPND measurements. The multiplicative modifying function is used for this purpose. Earlier a simple method was proposed and evaluated, in which measured power densities served as internal boundary conditions in the BIPR-5 calculations of the 3-D distributions for the entire core. Both methods have been tested using data from Loviisa-1 reactor core, consisting of 349 hexagonal fuel assemblies, each 14.7 cm across and 250 cm in length (active length). The SPNDs were placed on 4 levels: 50, 100, 150, 200 cm above the bottom of reactor core in 36 instrumented assemblies. Refs, figs and tabs