1. NAME AND TITLE
FAMREC: Fuel Assembly Mechanical Response Code System.
The basic subcodes used in FAMREC were taken directly from the Fortran Matrix Analysis (FORMA) library developed at the Martin Marietta Corporation, Denver Division, Denver, Colorado. Several additional subcodes were incorporated into this library to allow for various methods of calculating fuel assembly impact forces and spacer grid crushing loads.
2. CONTRIBUTOR
U.S. Nuclear Regulatory Commission, Washington, D. C. and Idaho National Engineering Laboratory, Idaho Falls, Idaho through the Energy Science and Technology Software Center, Oak Ridge, Tennessee.
3. CODING LANGUAGE AND COMPUTER
Fortran IV; CDC 7600 (P00167C760001).
4. NATURE OF PROBLEM SOLVED
FAMREC calculates the lateral mechanical response of a row of pressurized water reactor fuel assemblies while allowing for two types of nonlinearities. The first type is a geometric nonlinearity in the form of gaps between individual assemblies and between peripheral assemblies and a boundary wall. Impacting is monitored across these gaps. The second nonlinearity is the permanent deformation of the fuel assembly spacer grid to compressive loading. The primary results obtained are fuel assembly impact forces and spacer grid crushing loads.
5. METHOD OF SOLUTION
FAMREC is designed to determine PWR core region mechanical response to lateral excitation. The main structural element considered is the fuel assembly which is modeled as behaving in a linear fashion. The mode shapes and frequencies of the fuel assembly are incorporated directly into the solution procedure. A mass matrix is assumed for the assembly at each spacer grid elevation. Planar motion of the fuel is assumed to take place.
Impact may occur among the various core region structural components in a PWR. The fuel assemblies are positioned in the core region such that small gaps exist between neighboring elements. These small gaps allow impacting to occur between elements. This impacting is assumed to occur at spacer grid elevations. Permanent deformation of the fuel assembly grids is possible due to this impacting, and this phenomenon is accounted for in FAMREC.
The overall problem solution is carried out in several steps. Lateral core plate accelerations are applied through the appropriate transformations to each fuel assembly node translational degree-of-freedom as reverse inertia forces in a time history fashion. The lateral response of each fuel assembly degree-of-freedom is then obtained. At each time step, impact forces are calculated and are applied as forces at the next time step at the appropriate locations. The spacer grid crushing loads are obtained from or in conjunction with the fuel assembly impact forces.
FAMREC is basically the manipulation of a library of subcodes to obtain the nonlinear problem solution. A main program is used as the base in which the various parameters are defined and upon which the solution algorithm in the form of subprograms is built. The transient response subcode is called directly from the main program which in turn chooses one of the algorithms for solving the impact problem. The response is calculated in the modal plane. The uncoupled differential equations are solved close form using Laplace Transforms. The discrete displacements and velocities are then calculated and the gaps in the system monitored at each axial elevation for impacting. These impact forces are then applied statically at a given time step and equilibrium is found using a Gauss Elimination technique.
6. RESTRICTIONS OR LIMITATIONS
The version Dimension and Data statements must be modified if the number of applied forces is to be greater than 30, the number of modes greater than 80, the number of assemblies greater than 15, the number of total times and forces greater than 3601, or the number of grids per assembly greater than 5.
7. TYPICAL RUNNING TIME
The running time is not only problem dependent but also dependent upon which of three available impact calculation procedures is chosen. For a 17 assembly row with five grids on each assembly for 1000 time steps on the CDC 173/176 system, the central processor time was 86 sec while the peripheral processor time was 155 sec. This problem used the impact calculational procedure which falls in the middle as far as run time is considered.
8. COMPUTER HARDWARE REQUIREMENTS
FAMREC is operable on the CDC 7600 computers.
9. COMPUTER SOFTWARE REQUIREMENTS
A Fortran IV compiler and a SCOPE 2.1.3 Operating System are required.
10. REFERENCE
R. L. Grubb, "Pressurized Water Reactor Lateral Core Response Routine, FAMREC (Fuel Assembly Mechanical Response Code)," NUREG/CR-1019 (September 1979).
Aerojet Nuclear Company, "INEL-IGS" (March 1976).
11. CONTENTS OF CODE PACKAGE
Included are the referenced document and one (1.44MB) DOS diskette which contains the source code and sample problem input.
12. DATE OF ABSTRACT
April 1984, November 1999.
KEYWORDS: NUCLEAR SAFETY; PWR; STRUCTURAL MODELS