NODEX: A high order NEM-based nodal code

Conference · Wed Feb 01 04:00:00 EST 1989

OSTI ID:6358592

Sutton, T. M.

NODEX is a multigroup nodal diffusion theory code for general three-dimensional reactor analysis. The nodal solution procedure used in the code is based on a high order version of the Nodal Expansion Method (NEM). This transverse integrated nodal method is capable of obtaining extremely accurate solutions to the node-wise homogeneous diffusion equation on a very coarse computational mesh. NODEX uses a nonlinear iteration strategy in which the source iterations are performed using the low order Coarse Mesh Finite Difference (CMFD) method. The coupling coefficients used during this phase of the calculation are periodically recomputed using the NEM in order to cause the CMFD solution to match that of the higher order method. Source acceleration is achieved using a version of Wielandt's method that permits the group-wise computation of the node averaged flux values. Unlike many nodal codes that are limited to a one-and-a-half or two group energy treatment, NODEX has the ability to handle an arbitrary number of energy groups. When combined with an advanced homogenization scheme based on Generalized Equivalence Theory (GET), the code has the potential to solve heterogeneous reactor problems in a small fraction of the time required by a detailed finite difference or finite element calculation. In this report the NODEX solution algorithm is described in detail, including a discussion of the source acceleration scheme. This paper presents a method of using NODEX, or any other advanced nodal code, for accurate three-dimensional depletion calculations. Finally, briefly mentioned are some of the directions that NODEX development may take. 12 refs.

• Research Organization: Knolls Atomic Power Lab., Schenectady, NY (USA)
• DOE Contract Number: AC12-76SN00052
• OSTI ID: 6358592
• Report Number(s): KAPL-4708; CONF-890408-14; ON: DE89010546
• Country of Publication: United States
• Language: English

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99 GENERAL AND MISCELLANEOUS
990220 -- Computers
Computerized Models
& Computer Programs-- (1987-1989)
ALGORITHMS
COMPUTER CODES
COMPUTERIZED SIMULATION
DIFFERENTIAL EQUATIONS
EQUATIONS
FINITE DIFFERENCE METHOD
ITERATIVE METHODS
MATHEMATICAL LOGIC
N CODES
NEUTRON DIFFUSION EQUATION
NUMERICAL SOLUTION
SIMULATION
THREE-DIMENSIONAL CALCULATIONS