Comparison calculations for a BWR lattice with adjacent gadolinium pins

Within the frame of the Coordinated Research Program (CRP) safe core management with burnable absorbers in WWERs the BWR simplified fuel element with two adjacent gadolinium pins was chosen as the square lattice benchmark problem. The input calculation data, the format and the comparison of the results of the CRP participants were defined according to the NEACRP comparison as previously done at Eidg. Institute fuer Reaktorforschung, Wuerenlingen (EIR). The results were received from the following CRP participants: Skoda Czechoslovakia; Technical Research Center of Finland (VTT); VEN Bergman-Borsig Stammbetrieb des Kombinates Kab, Germany; Institut fuer Kernenergetik Universitaet Stuttgart, Germany; Bhabha Atomic Research Center, India and Boris Kidric Institute of Nuclear Sciences, Yugoslavia. Besides the comparison of these six CRP available data sets, an analysis was performed taking into account the 10 NEACRP data sets, which when added to the results of CRP participants gave the totals of 16 sets all together. This is a number with more significance from statistical point of view. To illustrate the significance of the number of data sets taken into account, both treatments were compared to NEACRP results. Variation coefficients of the most important parameters were compared to typical target accuracies for power reactors recommended by IAEA. The variations of most CRP results are in good agreement with the target accuracies except for the lifetime and Pu-239 build-up for the poisoned lattice. The variations of NEACRP+CRP and NEACRP results are larger than target accuracies for both the regular and the poisoned lattice. On the whole, an acceptably good agreement is obtained for the results supplied by CRP participants when treated separately. Smaller variations are observed in treating 16 sets of results (NEACRP+CRP) than in NEACRP comparison. (author). 10 refs, 7 tabs