QUARTERLY STATUS REPORT ON ULTRA HIGH TEMPERATURE REACTOR EXPERIMENT (UHTREX) FOR PERIOD ENDING SEPTEMBER 20, 1963

Construction of the UHTREX facility is about 63% complete and is about 5% behind scheule based on a completion date of February 1964. A series of 84 experimental runs were made in the half-scale flow model of the UHTREX core to investigate the degree of flow unbalance between the 312 fuel channels. It was shown that an initial source of strength of about 10/sup 3/ neutrons/sec is to be expected when UHTREX is fueled with 7 kg of enriched uranium (93.5% U/sup 235/, 1% U 94, and 5.5% U/sup 238/) loaded in graphite by solution impregnation. In an effort to refine the calculated worths of shutdown rods, several two-dimensional IBM 7090 codes, applying both neutron transport and diffusion theory, were used. To simplify the analysis of the UHTREX system's dynamic behavior, the major components for heat exchange are represented by three or four axial lump models. The UHXCOM simulation program solves the basic system differential equations on the IBM 7090 and produces time plots of different operating variables such as reactor power, period, gas temperature, etc. A separate analysis is being made with a frequency domain IBM 7090 program that solves equations written in terms of the Laplace transform variable. Very satisfactory performance was achieved with a process gas chromatograph. The second of two single-stage diaphragm compressors was operated for 20 hr in a shakedown run. Two helium blowers operating on hydrodynamic gas bearings were developed. (M.C.G.)