Fast Neutron Flux in the University of Maryland Reactor

Abstract

The fast neutron flux distribution in the experimental facilities of the University of Maryland Reactor (UMR) was studied by means of neutron activation threshold foils with the reactor at a power level of 10 kw. The foils used were sulfur, magnesium, and aluminum which detected neutrons of energies greater than 3.0 Mev, 6.3 Mev, and 8.1 Mev, respectively. The activities of the foils were measured by calibrated beta and gamma scintillation detection systems. A central row of fuel elements, the west beam port, and the through tube were studied using all three types of foils. The fast neutron flux above 3.0 Mev was measured in each element of the core. The maximum fast neutron flux above 3.0 Mev available in the central ''glory hole " was about 2x10^10 n/cm^2 -sec. The flux above 6.3 Mev and above 8.1 Mev was about 5.5x10^8 n/cm^2 -sec and about 4.5x10^8n/cm^2 -sec, respectively. Available in the west beam port was a maximum fast neutron flux above 3.0 Mev of about 2.6x10^9 n/cm^2 -sec adjacent to the core and of about 1.2x10^7 n/cm^2 -sec at the inner face of the beam port shield plug. The fast neutron flux above 3.0 Mev available in the center of the through tube was 1.7x10^9 n/cm^2 -sec. The minimum at both east and west ends, at the inner faces of the shield plugs, was about 7x10^5 n/cm^2 -sec.