Determination of thermal neutron flux by activation of a pure target with known cross section

Abstract

The thermal neutron flux in a reactor may be determined by activation of a pure target of known cross section. Gold foils were irradiated in the core of the AGN=201 reactor and from the absolute disintegration rate the thermal flux at the core center was determined to be 5.31 x 10(6) neutrons per square centimeter per second, maximum, at a nominal power level of 100 milliwatts. The previous determination of the thermal flux by the manufacturer using a comparison method and a polonium-beryllium neutron source gave a value of 4.5 x 10(6) neutrons per square centimeter per second at the same power level. The writers wish to express their appreciation to Professor William W. Hawes of the U.S. Naval Postgraduate School for his assistance and encouragement during this investigation.