NESC0184 THERMOS-BRT-1.

THERMOS-BRT1

BRT1, like the original THERMOS code developed by H. Honeck of Brookhaven National Laboratory, computes the scalar thermal neutron spectrum as a function of position in a lattice by solving the integral transport equation with isotropic scattering. One-dimensional slab or cylindrical geometry may be used. As output the code supplies flux-averaged values of sigma a, sigma f, nu sigma f, sigma s, and d for the cell composition and the values of sigma a, sigma f, nu sigma f, sigma s, and sigma tr for the isotopic constituents.

The method used in solving the transport integral equation is the power iteration method. To accelerate convergence the code uses a combination of Gauss iteration, renormalization, over-relaxation, and extrapolation procedures.

Maxima of

• 30 speed groups

• 30 space points

• 30 isotopes in mixture

• 30 isotopes in the edit

• 8 mixtures

The sample problem is a 2-region slab and is solved using 10 space points and 30 speed groups. There are two mixtures used. Five materials are used in the cell and one in the edit. The time in general is a function of the number of space points and energy groups used by the problem.

Typical running time for BRT1 with the random access library is one minute with a reflecting boundary condition and 30 seconds with a white boundary condition. Succeeding cases require approximately 15 seconds each.

In BRT1 options include the white boundary condition, current calculation, transverse buckling, linear anisotropic scattering correction, and smeared cell punched output for use as region input to a succeeding case. Random access library data can be stored on drum or disk.

RLITHE updates and/or prints the BRT data tape or random access data.

• H.C. Honeck: A Thermalization Transport Theory Code for Reactor Lattice Calculations, BNL-5826 (September 1961).

• H.C. Honeck: The Distribution of Thermal Neutrons in Space and Energy in Reactor Lattices Part 1 – Theory Nuclear Science and Engineering, p. 193 (1960).

• D.R. Skeen and L.J. Page: THERMOS/Battelle..The Battelle Version of the THERMOS Code, BNWL-516 (June 1967).

64K memory, input, output, program, library, and punch units plus 3 scratch units or equivalent drum storage.

CSCX.

C. L. Bennett and W. L. Purcell

Reactor Physics Department

Pacific Northwest Laboratories

Battelle

P. O. Box 999

Richland, Washington 99352

USA