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Manuscript Title: GRENADE: a coarse-mesh reactor physics program to solve the static diffusion equation for neutrons.
Authors: T.A. Beu, D.I. Simionovici, V.N. Anghel
Program title: GRENADE
Catalogue identifier: AALJ_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 42(1986)197
Programming language: Fortran.
Computer: CDC CYBER 170/720.
Operating system: NOS 1P4 552/552.
RAM: 26K words
Word size: 60
Keywords: Reactor systems, Diffusion equation, Nodal method, Eigenvalue problem, Neutron, Fission source iteration, Extrapolation, Coarse-mesh rebalancing.
Classification: 22.

Nature of problem:
The program is designed to solve the static multigroup diffusion equation for neutrons in multidimensional problems, assuming Cartesian geometry. The program yields flux- and power distributions and the effective neutron multiplication factor (keff).

Solution method:
GRENADE (Green's Funtion Nodal Algorithm for the Diffusion Equation) is based on the linear form of the nodal balance equation written in terms of the average net interface currents across the surface of a subdomain (node). Green's functions for the one-dimensional in-group diffusion- removal operator are used to generate a coupled set of one-dimensional integral equations defined over a node. These integral equations represent an exact (local) solution to the coupled set of one- dimensional differential equations obtained by spatially integrating the multidimensional diffusion equation over directions transverse to each coordinate direction. The integral equations are approximated using a weighted residual procedure. The resulting matrix equations, when solved in conjunction with the linear form of the nodal balance equation, provide the necessary additional relationships between the net interface currents and the flux within a node.

Restrictions:
The size of the reactor model that can be handled is limited by computer core capacity.

Running time:
On CDC CYBER 170/720 the solution of the two-dimensional two-group IAEA benchmark problem with a 9*9 points mesh grid took about 9 seconds CPU time.