**1. NAME AND TITLE**

FEMB: A Two-Dimensional Diffusion Theory Finite Element Program.

**2. CONTRIBUTOR**

Riso National Laboratory, Roskilde, Denmark.

**3. CODING LANGUAGE AND COMPUTER**

ALGOL; BURROUGHS 6700.

**4. NATURE OF PROBLEM SOLVED**

FEMB computes the neutron flux and multiplication in a two-dimensional (x-y) geometry.

**5. METHOD OF SOLUTION**

FEMB solves the diffusion-theory equations using finite elements for one group at a time using the ordinary power iteration technique. The equation for one group is solved by a pointwise successive overrelaxation technique. There is only one inner iteration for each outer one.

The iterations are accelerated by extrapolation for removal of the dominating error-mode. The
iterations are stopped when the local error is less than a given input parameter (eps).

**6. RESTRICTIONS OR LIMITATIONS**

It is not a fast program, and therefore should be used when high precision is needed.

**7. TYPICAL RUNNING TIME**

No study has been made by RSIC of typical running times for FEMB.

**8. COMPUTER HARDWARE REQUIREMENTS**

The code is operable on a BORROUGH 6700 computer.

**9. COMPUTER SOFTWARE REQUIREMENTS**

An ALGOL compiler is required.

**10. REFERENCE**

I. Misfeldt, "The Program FEMB Users Manual," Riso-M-1929 (March 1977).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced document and one (1.2MB) DOS diskette which contains the source
code written in ALGOL and the sample problem input.

**12. DATE OF ABSTRACT**

January 1982.

**KEYWORDS:** NEUTRON; TWO-DIMENSIONS; DIFFUSION THEORY; FINITE ELEMENT
METHOD