Thulium oxide can be irradiated to meet the desired specific heat generation of 1.5 watts per gram as part of a flux amplification test, which will be conducted the early part of FY-1965. To obtain the heat generation level, is calculated that a 120-day irradiation will be required at a flux of 1.1 {times} 10{sup 14} neutrons/cm{sup 2}-sec. if the proposed target element is modified by reducing the thulium oxide wafer thickness from 0.080 to 0.050 inch. Also, the length of the target element should be reduced to not more than 20 inches to minimize the possibility of sticking in the process tube. This would require four targets rather than a single element as proposed. Prior to undertaking this irradiation, it would be desirable to place a prototype target element in the Hanford Test Reactor to determine the approximate rise factor (change in neutron flux level between the target element and adjacent tubes of fuel elements) in order to more precise data for planning the loading pattern in the production test.