The SENDIFF solution shows no change in flux through the He-3 detector. This means that the detector cannot
detect the nuclear material of interest. This result has inherent uncertainty due to the one-group capabilities
of SENDIFF; however, one can overcome this uncertainty if SENDIFF is to be extended to a multi-group formulation.
SUMMARY AND CONCLUSIONS
This project sought to model a realistic situation in which determining flux would be critical to developing
detection methods for nuclear weapons material. The program SENDIFF provided flux distributions that are
consistent with physical phenomenon. The flux behaved as expected in the different regions modeled in the problem.
One of the main drawbacks to the practicality of SENDIFF was its long computation time. To arrive at the solution
to this problem, over one hour of computation time was required. In practice this would not be enough
computation time reduction to warrant a diffusion approximation over a full transport calculation.
However, techniques can be utilized such as compressed diagonal storage (CDS) to reduce the memory
requirements by several orders of magnitude. Iterative matrix solution techniques could also be implemented
instead of LU decomposition to reduce the number of mathematical operations necessary to solve the system
of equations. Furthermore, this calculation was performed on a single processor. If the solution was implemented in
a parallel computing environment with multiple processors, the computation time would be greatly reduced.
Finally, the applicability of SENDIFF for practical problems could also be improved if multiple energy
group considerations were included.
ACKNOWLEDGEMENTS
I would like to thank my advisor, Dr. Alireza Haghighat, for all of his advice on everything from linear algebra
to basics of particle transport. I would also like to thank Dr. Glenn Sjoden for providing cross section data as well as
a PENTRANTM model for comparison.
REFERENCES
1. J. DeMarco, Vector and Parallel Algorithms for Solving the Neutron Diffusion Equation. May, 1991 (unpublished). Back
2. R. Pozo, Template Numerical Toolkit. http://math.nist.gov/tnt Back
--top--