Generation of the problem-dependent data libraries for IFIN-HH WWR-S spent fuel storage criticality and dose calculation

The methods used for the radioactivity inventory calculation and dose evaluation of the fuel elements irradiated in the WWR-S IFIN-HH reactor are discussed in this work. A particular attention is paid to the processed problem-dependent nuclear libraries. SAS2H, a complex sequence of the SCALE-4.3 code system containing the modules BONAMI - NITAWL - XSDRNPM - COUPLE - ORIGEN-S - XSDOSE, has been assimilated on the IFIN-HH computer and applied to update the ORIGEN-S libraries by producing problem-dependent processed data libraries needed to perform the depletion and shielding analysis. This sequence uses one of the eight associated data libraries of the SCALE-4.3 system according to the choice of the user. The method consists in the following analysis processes: i) lattice cell neutron analysis to produce the flux weighting spectrum for activation library updating; ii) update of the nuclear data constants of the ORIGEN-S libraries; iii) depletion and decay analysis for a specified fuel assembly and irradiation history in order to generate gamma and neutron source strength and spectra. iv) one-dimensional radial shielding calculation for the evaluation of the angular neutron and gamma flux at the surface of a spent fuel shipping cask and further calculation of the dose rates at various points outside the cask. An efficient alternative of the calculation sequence mentioned above is the ARP (Automatic Rapid Processing) method conceived in order to generate independently ORIGEN-S libraries and to reduce substantially the running time. The substance of this method is the generation of the problem-dependent libraries from basis libraries a priori created by SAS2H for specific fuel assembly type and further interpolation of two independent variables, enrichment and burnup. Specific applications concerning WWR-S spent fuel were performed: i) generation of three problem-dependent libraries for the S-36 fuel assembly taking into account the maximum value of the burnup of this type of fuel for an average value of the reactor power; ii) calculation of the radioactive inventory for a dummy fuel element with maximum values for its parameters using both the library 'complex cycle' and 'fresh cycle'; iii) determination of the dose rates outside a standard container and the optimisation of the number of the S-36 fuel elements contained inside. (authors)