An assessment of the BWR fuel box-lattice-cell homogenization procedures with the Tarapur BWR incore and excore measurements

A code system has been developed to provide the incore fuel-management guidelines to the Tarapur BWR reactors. The operating data include cold/hot criticals and detailed incore flux/power maps. Besides these, the burnups and isotopic composition of a few irradiated fuel pins obtained by mass-spectrometric analyses, are also available for validation of the BWR core and lattice-cell modelling. The calculated eigen values for different power levels and at different core average burnups are found to have a spread of less than 0.25% ΔK. Analyses of a number of TIP measurements show that the core power distribution can be predicted in a satisfactory manner for uncontrolled fuel bundles and non-peripheral fuel assemblies (< 10%). For prediction of cold-criticals the void-history effects are found to be unimportant. The pin burnups and isotopic densities of important U and Pu isotopes relative to 238U have been compared with mass-spectrometric measurements. The pin-burnup profile comparison is found to be good for fuel pins, which are not near water gaps. Deviation histograms of various isotopes are presented. 235U is predicted within +- 3% (r.m.s.). The total Pu is overpredicted by 5-8% while the quality of Pu is predicted within +- 1.0% (r.m.s.). (author)