Determination of Neutron Multiplication Factors as a Function of Temperature with the High Temperature Lattice Test Reactor

The High Temperature Lattice Test Reactor (HTLTR) is a unique critical facility specifically built for studying reactor lattices at temperatures up to 1000°C. A description of the reactor is given and the unpoisoned technique for determining as measured by the unpoisoned method and the well known Physical Constants Testing Reactor null reactivity method method are given for a natural UO₂-2.2 wt% PuO₂ (8% ²⁴⁰Pu) graphite lattice and for a UO₂ (97.42 wt% ²³³U)-²³²ThO₂-C fuel element in a graphite array. Experimental values for the neutron multiplication factor have been determined as a function of temperature using the HTLTR for a graphite moderated lattice fueled with a ²³⁵UC₂ -²³²ThO₂ -C fuel mixture. These results provide valuable check points for testing computational methods currently being applied in the design of high temperature gas cooled reactors.