**
1. NAME AND TITLE**

FPZD: Code System for Multigroup Neutron Diffusion/Depletion Calculations.

**2. CONTRIBUTOR**

Marshall Space Flight Center, NASA, Huntsville, Alabama.

**3. CODING LANGUAGE AND COMPUTER**

FORTRAN 77; PC 386 and PC 486.

**4. NATURE OF PROBLEM SOLVED**

FPZD calculates the spatial power and neutron flux distributions of a nuclear reactor along with its effective multiplication factor and time-dependent material compositions.

**5. METHOD OF SOLUTION**

The depletion subroutines permit a very generalized nuclide depletion scheme to be used in which the materials may be distributed into a number of burnup subregions each containing a different atom density set. Depletion of the nuclides is calculated separately for each burnup subregion assuming exposure to the average flux of the spatial region. The macroscopic properties of a spatial region are calculated by giving the appropriate volume fraction weighting factors to the cross sections of the burnup subregions.

**6. RESTRICTIONS OR LIMITATIONS**

Non noted.

**7. TYPICAL RUNNING TIME**

On a 20 megahertz PC 386 with a math co-processor, the following times were noted: FPZDIN.INI took 45 minutes; FPZDIN.KIC took 25 minutes; FPZDIN.IC took 35 minutes; FPZDIN.KRL took 45 minutes; FPZDIN.RL took 40 minutes.

**8. COMPUTER HARDWARE REQUIREMENTS**

FPZD runs on the PC 386 or PC 486 under the DOS 5.0 operating system; a math co-processor is required.

**9. COMPUTER SOFTWARE REQUIREMENTS**

The code was written in FORTRAN 77 and was tested using the Microsoft Version 5.01 compiler.

**10. REFERENCES**

B. Emmrich, "A One-Dimensional Multigroup Neutron Diffusion/Depletion Code for Performing Control and Fuel Loading Searches and for Determining the Fuel and Poison Distributions Required to Achieve Burnup Independent Power Distributions with Optional Thermal-Fluid Feedback," NASA informal document, Marshall Flight Center, Huntsville, Alabama.

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced documents and 3 5.25-inch DS/HD (1.2MB) diskettes which include source and executable codes, sample input and output.

**12. DATE OF ABSTRACT**

June 1992.

**KEYWORDS: **BURNUP; DIFFUSION THEORY; NEUTRON; REACTOR
PHYSICS; MICROCOMPUTER; MULTIGROUP; ONE-DIMENSION