MATHEMATICAL TECHNIQUES IN TWO-SPACE-DEMENSION MULTIGROUP CALCULATIONS
Reactor design technology includes extensive application of high speed, large memory, digital computer techniques, especially in the evaluation of nuclear characteristics. One of the most vauable engineering and physics tools is the two-space-dimension multigroup calculation which has during the past year undergone a rapid metamorphosis to keep abreast of digital computer development. The first such progrsm, MUG, though hampered by mesh increment and material region limitations, was widely used from 1953 to 1956. Several alternate programs were developed during these year, and various physics concepts were introduced to enable more accurate analysis of a wider range of reactor parameters. In early 1956, the PDQ and CURE programs became available, supplanting previous codes by solving more general problems much more rapidly and at lower cost. Although a major contributing factor to the success of these programs was thee faster and larger computer memory avaliable, mathematical iteration technique advances were also of importance. Both Tchebysheff and steepest descent extrapolation parameters are automatically used to combine successive fission distribution iterates so that the number of fission source iterations is reduced considerably in many problems. In PDQ, optimum flux iteration parameters are automatically computed for the Sucgeneralized alternating-direction-impliclit scheme has replaced the less rapidly convengent SOR method. The CURE program also adjusts the flux iteration parameters to be consistent with the convergence rate of the fission source distribution. Group dependent neutron fluxes and adjoint-fluxes may be calculated. The CURE program permits a material dependent fission spectrum in order that variations in fission cross-sections which become spectrum variations in the adjoint calculations may be properly taken into account. A perturbation program, CURE-PSP, computes reactivity coefficients from input cross-section increments, and CURE flux and adjoint output as written on tape by the CURE program. This perturbation caculation is used for computing temperature coefficients, effect of local inhomogenelities, prompt generation time, and other significant reactor parameters. Burnout programs, PDQ-TURBO and CURE-BO, enable lifetime studies of reactor characterlistics with relatively little manual imput preparation between time steps. TURBO considers various isotopic chains whereas BO is restricted to fully enriched reactors calculations are at present restricted to few-group problems, these being especially useful for light-water moderated reactors. Control elements consisting of retatively thin thermally black regions have been treated by various methods, all of which take into account the inadequacy of simply diffusion theory near these regions. One useful approach for cylindrical coordinate calculations of reactors with rod banks is the window shade cross- section modification which combines the Hurwitz-Roe absorption-area theory with experimentally determined extrapolated endpoints to yield appropriate few-group constants for regions with control elements. In calculations where the controll elements are represented by geometrically thin regions, cross-sections within the elements are modified to offectively replace simple diffusion by more appropriate theories within these control elements. Correlationn with experiment has been satisfactory. (auth)
- Research Organization:
- Knolls Atomic Power Lab., Schenectady, N.Y.; Los Alamos Scientific Lab., N. Mex.
- NSA Number:
- NSA-12-014906
- OSTI ID:
- 4307836
- Report Number(s):
- A/CONF.15/P/633
- Resource Relation:
- Other Information: Prepared for the Second U.N. International Conference on the Peaceful Uses of Atomic Energy, 1958. Orig. Receipt Date: 31-DEC-58
- Country of Publication:
- United States
- Language:
- English
Similar Records
MTR-ETR TECHNICAL BRANCHES QUARTERLY REPORT PERIOD ENDING MARCH 31, 1959
MATERIALS TESTING REACTOR-ENGINEERING TEST REACTOR TECHNICAL BRANCHES QUARTERLY REPORT, OCTOBER 1-DECEMBER 31, 1960