Use of the 'DRAGON' program for the calculation of reactivity devices

DRAGON is a computer program developed at the Ecole Polytechnique of the University of Montreal and adopted by AECL for the transport calculations associated to reactivity devices. This report presents aspects of the implementation in NASA of the DRAGON program. Some cases of interest were evaluated. Comparisons with results of known programs as WIMS D5, and with experiments were done. a) Embalse (CANDU 6) cell without burnup and leakage. Calculations of macroscopic cross sections with WIMS and DRAGON show very good agreement with smaller differences in the thermal constants. b) Embalse fresh cell with different leakage options. c) Embalse cell with leakage and burnup. A comparison of k-infinity and k-effective with WIMS and DRAGON as a function of burnup shows that the differences ((D-W)/D) for fresh fuel are -0.17% roughly constant up to about 2500 MWd/tU, and then decrease to -0.06 % for 8500 MWd/tU. Experiments made in 1977 in ZED-2 critical facility, reported in [3], were used as a benchmark for the cell and supercell DRAGON calculations. Calculated fluxes were compared with experimental values and the agreement is so good. d) ZED-2 cell calculation. The measured buckling was used as geometric buckling. This case can be considered an experimental verification. The calculated reactivity with DRAGON is about 2 mk, and can be considered satisfactory. WIMS k-effective value is about one mk higher. e) Supercell calculations for ZED-2 vertical and horizontal tube and rod adjuster using 2D and 3D models were done. Comparisons between measured and calculated fluxes in the vicinity of the adjuster rods. Incremental cross sections for these adjusters were calculated using different options. f) ZED-2 reactor calculations with PUMA reveal a good concordance with critical heights measured in experiments. The report describes also particular features of the code and recommendations regarding its use that may be useful for new users. (author)