**1. NAME AND TITLE**

VPI-NECM: Nuclear Engineering Computer Models for In-Core Fuel Management Analysis.

The original VPI modules were developed on an IBM computer at Virginia Polytechnic Institute
and State University, Blacksburg, Virginia.

**2. CONTRIBUTORS**

The Institute of Atomic Energy, Swierk, Poland, and the International Atomic Energy Agency,
Vienna, Austria, through the OECD NEA Data Bank, Gif-sur-Yvette, France. SKODA Works in
Czechoslovakia as part of the Coordinated Research Project through the NEADB contributed the PC
version.

**3. CODING LANGUAGE AND COMPUTER**

Fortran IV; CDC CYBER 740 (A), VAX-11 (B). Fortran 77; PC 386 or 486 (C).

**4. NATURE OF PROBLEM SOLVED**

VPI-NECM is a nuclear engineering computer system of modules for in-core fuel management
analysis. The system consists of 6 independent programs designed to calculate: (1) FARCON - neutron
slowing down and epithermal group constants, (2) SLOCON - thermal neutron spectrum and group
constants, (3) DISFAC - slow neutron disadvantage factors, (4) ODOG - solution of a one group
neutron diffusion equation, (5) ODMUG - three group criticality problem, (6) FUELBURN - fuel
burnup in slow neutron fission reactors.

**5. METHOD OF SOLUTION**

FARCON solves the diffusion equation for a homogeneous medium composed of N isotopes in 33
groups in fast and resonance energy region. The solution in the thermal energy region carried out by
module SLOCON is based on the Wigner-Wilkins approximation and applies the Runge-Kutta method.
The burnup calculations are carried out in 3 energy groups. Only Xe-135 and Sm-149 are treated
directly. All the other fission products are represented by 2 pseudo isotopes. Module ODOG solves
the finite difference diffusion equation by a direct method. Module ODMUG uses the Chebyshev
acceleration of outer iterations. It gives a possibility for calculating a critical boron concentration.
VPI-NECM is designed for educational purposes. It is based on simple physical models and numerical
techniques. Very short computing times and low computer requirements have been achieved in this
way. At the same time, the package consists of the basic modules necessary for modern in-core fuel
management analysis and its usage delivers realistic cases to the student.

**6. RESTRICTIONS OR LIMITATIONS**

It is assumed that the elementary reactor cell consists of the fuel rod surrounded by water. The
library data are limited to isotopes typical for water power reactors. The reactor can be treated in one
dimension only, i.e. as a slab, sphere, or cylinder with one-dimensional symmetry.

**7. TYPICAL RUNNING TIME**

On the CDC CYBER 740, each module ran in less than 10 seconds. On the VAX-11/780,
FARCON ran in 5 seconds, SLOCON in 5 seconds, DISFAC in 3 seconds, ODOG in 4 seconds,
ODMUG in 5 seconds, and FUELBURN in 24 seconds. The test problems ran a few seconds on a PC
486 (33 megahertz).

**8. COMPUTER HARDWARE REQUIREMENTS**

VPI-NECM is operable on the CDC CYBER 740 computer, the VAX-11 computer and PC 386
or PC 486 with math co-processor. The programs work entirely in the core memory of the computer.
600,000 words are needed to compile and run the modules.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A Fortran IV compiler is required for versions (A) and (B). The PC version (C) requires the
Fortran 77 Compiler Microsoft Fortran Version 5.1 under MSDOS 4.1.

**10. REFERENCES**

T. Kulikowska and B. Szczesna, "The VPI Program Package," Preliminary version (1984).

T. Kulikowska, "Report on Work Performed During the Third Year of the Coordinated Research Programme on Codes Adaptable to Small and Medium Size Computers in Developing Countries for In-Core Fuel Management."

T. Kulikowska and B. Szczesna, "Remarks and VPI Program Package Usage."

T. Kulikowska and B. Szczesna, "Translation of VPI Program Package to the CDC Computer," (1983).

H. A. Kurstedt, Jr., "Nuclear Safety Module, NSM-1 Reliability Analysis for Reactor Safety."

H. A. Kurstedt, Jr., "Nuclear Safety Module, NSM-2 Fission Product Release."

R. L. Whitelaw, "Nuclear Power Plant Module, NPP-1 Nuclear Power Cost Analysis."

M. C. Edlund, "Fuel Management Module, FM-1 Fuel Burnup in Slow Neutron Fission Reactors."

M. C. Edlund, "Fuel Management Module, FM-2 Fast Reactor Fuel Cycle Program."

G. H. Beyer, "Fuel Management Module, FM-3 Feed Material and Separation Work Requirements for Enriching Uranium by Gaseous Diffusion."

R. J. Onega, "Reactor Dynamics Module, RD-2 Reactor Kinetics with Feedback."

R. J. Onega, "Reactor Dynamics Module, RD-1 The Reactor Kinetics Equations."

T. Kulikowska, K. Andrzejewski, K. Maskowski, S. Stelmachowski, and B. Szczesna, "Progress Report No. 5," (March 1984).

R. J. Onega, "Reactor Statics Module, RS-2 The Numerical Solution of the One Group Neutron Diffusion Equation."

R. L. Bowden and M. C. Edlund, "Reactor Statics Module, RS-3 Neutron Slowing Down and Epithermal Group Constants."

P. F. Zweifel, "Reactor Statics Module, RS-4 Resonance Absorption."

M. C. Edlund, "Reactor Statics Module, RS-5 Multigroup Constants for Fast Breeder Reactors."

R. J. Onega and M. C. Edlund, "Reactor Statics Module, RS-6 Slow Neutron Disadvantage Factors."

R. J. Onega, "Reactor Statics Module, RS-7 Thermal Neutron Spectra and Thermal Group Constants for Light Water Reactors."

J. R. Thomas, "Reactor Statics Module, RS-8 Three-Group Criticality Program."

Final Report - "In-Core Fuel Management Programs for Nuclear Power Reactors," IAEA-TECDOC-314.

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced documents and one (1.2MB) DOS diskette which contains the source
codes, cross section libraries, and sample problem input. The PC version is distributed on one DS/HD
5.25 inch diskette (1.2MB) which includes source files, executables, data files, batch files, and sample
cases in compressed mode.

**12. DATE OF ABSTRACT**

June 1986; September 1992.

**KEYWORDS: ** REACTOR PHYSICS; MICROCOMPUTER