Two 500-kw fused-fluoride-to-Nak heat exchangers, two 500-kw NaK-to-air radiators, and a 20-tube high-velocity heat exchanger were fabricated for a heat-exchanger development program. A construction procedure, utilizing both inert-arc-welding and high temperature dry-hydrogen brazing, was used successfully on all of the units. The tube-to-header joints were welded and back-brazed; the manifold joints were inert-arc-welded with full penetration; and the tube-to-fin joints were brazed. A detailed description of the fabrication of each type of component is discussed and a cost analysis of the 500-kw units is presented.

The Homogeneous Reactor Test (HRT) is the experimental reactor facility (Frontispiece) being designed and constructed at ORNL as the next step in homogeneous reactor development between the 1-Mv HRE and a "full-scale" power station. The HRT will provide an integrated test at 5 to 10 Mv for the flowsheet and equipment designs on which the full-scale effort will be based. Furthermore, its design is such that several homogeneous systems which require essentially the same operating equipment may be tested with comparatively minor modifications of the original reactor installation. The reactor will be assembled in the building which housed the HRE, located in the experimental reactor exclusion area approximately one mile south of the oak ridge laboratory. (See figure 1) / It is the purpose of this report to provide information with which the hazardous aspects of this reactor may be evaluated. Briefly, it will be shown after a statement of purpose and a general description of the reactor that: 1. The design characteristics and equipment requirements are such that escape of highly reactive material from the reactor piping is unlikely. 2. Should the entire core and blanket contents suddenly escape from the reactor system, a seal-welded steel tank surrounding the …