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Conference Article: Present HTR physics calculational methods at the Paul Scherrer Institute.

Abstract

In this paper a general description of HTR related calculational methods and data available at the Paul Scherrer Institute (PSI) is given. The cell codes used are MICROX-2, WIMS-D, and TRAMIX. MICROX-2 is an integral transport theory spectrum code which solves the neutron slowing down and thermalization equations on a detailed energy grid for a two region lattice cell. A second level of heterogeneity can be treated, i.e. the inner region may include two different types of grains (particles). WIMS-D contains tabulations of temperature dependent resonance integrals accurately evaluated for homogeneous mixtures of moderator and absorber at many energy points. Equivalence theorems are utilized to obtain few-group effective cross sections in heterogeneous problems. The intermediate resonance absorption shielding (IR) method of resolved resonances is employed. The spherical geometry of the pebble can be converted into an equivalent cylindrical geometry, and the double heterogeneity can be treated using the available cluster option with a method developed by Segev. TRAMIX is a flexible computer (cell) code which reads fine group nuclear data from a library in the Los Alamos National Laboratory (LANL) format MATXS and produces fine group cross sections using the IR methods. Self-shielded multigroup cross sections produced with these cell codes can be used in connection with the one- and two-dimensional discrete-ordinates finite difference transport codes ONEDANT and TWODANT from LANL for full reactor calculations. Additional interface modules which are available include a B_N module for leakage calculations and some library management codes plus the PERT-V diffusion perturbation theory code. Most of the nuclear data libraries for the cell codes are based on the JEF-1 (Joint European File) evaluation. They were processed using the NJOY nuclear data processing system from LANL with additional PSI developments. These libraries include the fast, thermal and resonance data tapes FDTAPE, GGTAPE, and GARTAPE for MICROX-2, the WIMS-JEF file for WIMS-D, and MATXS formatted files in a variety of group structures for TRAMIX.

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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:130-135