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Conference Article: Nuclear data related to HTRs

Pelloni, S. (Paul Scherrer Inst. (PSI), Villigen (Switzerland)); Giesser, W. (Hochtemperatur-Reaktorbau GmbH, Mannheim (Germany, F.R.))

Abstract

A series of two-dimensional discrete-ordinates transport theory keff calculations with an (r,z) geometric model have been performed for a simple, typical LEU HTR PROTEUS configuration (7042 pebbles) without the simulation of any water ingress into the core, with LEU AVR non irradiated fuel containing 6 grams of 16.7% enriched uranium per pebble, for a filling factor of 0.74 (maximum packing) and for a moderator-to-fuel pebble ratio M/F of 1/1. All calculations were based on specific data libraries (mainly based on JEF-1) for the cell codes WIMS-D, MICROX-2, and TRAMIX, and were performed using these codes in connection with the one- and with the two-dimensional transport theory programmes ONEDANT and TWODANT from Los Alamos. WIMS-D may now be routinely used for HTR applications with a new method developed by Segev which allows the conversion of the spherical pebble bed unit cell into an equivalent (from the neutronic point of view) cylindrical unit cell. It is found that the calculated eigenvalue keff depends particularly on the transport corrected total cross sections employed in the full reactor calculation, on the number of groups, and on the nuclear data (i.e. from JEF-1 or from older evaluations) used. For a 13 neutron group calculation in the well tested structure from Hochtemperature Reaktorbau (HRB), the eigenvalue keff ranges from 0.9896 for P0 modified cross sections coming from MICROX-2 to 1.0083 for P0 modified JEF-1 cross sections from WIMS-D. Either the use of P1 modified cross sections in connection with the group structure from HRB, or that of P0 cross sections (suitably modified) in connection with a finer group structure, particularly in the thermal range, is recommended for physics calculations of small HTR cores.

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key words: Gas Cooled Reactor, Nuclear Technology
Reference:
Uncertainties in physics calculations for gas cooled reactor cores. Proceedings of a specialist's meeting held in Villigen, Switzerland, 9-11 May 1990
International Atomic Energy Agency, Vienna (Austria). International Working Group on Gas-Cooled Reactors
IWGGCR--24, pp:98-103