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# Accession Number:

## AD0478895

# Title:

## VERIFICATION OF ANALYTICAL TECHNIQUES (GAPLSN--TRANSPORT THEORY AND 05R-- MONTE CARLO THEORY) BY UTILIZATION OF MEASURED FAST NEUTRON SPECTRA IN INFINITE PARAFFIN AND SPHERICAL PARAFFIN SHIELDS.

# Descriptive Note:

## Final rept. 22 Dec 64-1 Oct 65,

# Corporate Author:

## GENERAL DYNAMICS SAN DIEGO CA GENERAL ATOMIC DIV

# Report Date:

## 1966-03-01

# Pagination or Media Count:

##
214.0

# Abstract:

## High resolution measurements of the angular flux spectrum of fast neutrons in CH2 were made in point-source, infinite medium and point-source, finite medium, sphere geometries. Angular flux spectra were calculated with the GGSN and GAPLSN Sn transport codes and the 05R Monte Carlo code. Comparison with experiment established that P3 anisotropic scattering and S16 angular mesh in the Sn codes were required to calculate neutron penetration to 30 cm. Results were relatively insensitive to the method of obtaining group average cross sections in the GAM-2 code, but discrepancies above 8 MeV and below 1 MeV may arise from cross section errors. The Sn code did not calculate the zero-degree flux properly and future work should include small-angle calculations with a variable-angle Sn code. The Monte Carlo results were in good agreement with comparable Sn results, but disagreed with experiment above 8 MeV. Below 1-2 MeV statistical fluctuations were large at 30 cm penetration, even for 100,000 neutron histories and with source energy biasing to reduce variance. Small-angle spectra were not calculated too well, particularly at the lower energy. However, part of this discrepancy is due to neglect of the uranium target in the 05R calculations. Recommendations are given for further investigations to resolve the remaining problems in the sphere measurements, and to extend the work to a two-dimensional geometry. Author

# Distribution Statement:

## APPROVED FOR PUBLIC RELEASE

#