Power and Propulsion Systems Technology

Loftttouse, G. D. Pincock, J. F. Ktmze, R. E. Wood (GE-Idaho), R. E. Hyland (NASA-Leuds) 

A preliminary ejqieriment was peirformed in a small (7-f liter) cavity container placed in a relatively isotropic thermal flux of a conventional reactor. A gaseous (UF ) cavity was compared with a uniform dispersion of the above-mentioned fuel sheets (93.2% U-235). For equivalent reactivities, the U-23S mass in the fuel sheets was G% greater than in the gas, and this value is approximately the same as the thermal-flux self-shielding effect for such fuel sheets. 

The cavity reactor has 3S-in.-thick radial and end reflectors of OkO.. The cavity, wall is -in. A1 oh the radius and i-in. A1 on the ends. Inside dimensions of the cavity are 4-ft. long by 6-ft. diam. The fuel sheets are supported on corrugated aluminum screens within the cavity. A total of 75 kg of aluminum and 273 g of manganese impurity form the structure in the cavity. There are 764 kg (1.0% volume fraction) of structural aluminum inside the DjO region. The heavy water contains 0.22% HtO. One end reflector contains 36 holes (void), -in. diameter, for control rods. This void represents 1.0% of the volume of an end reflector. 

The worth of a one-foot-diameter central hole in one end reflector was measured to be 0.76% Ak. In the most dilute core (largest fuel radius) the peak power (at the corner of the fuel) was a factor of 1.3 above the core-center power. In the core with a fuel radius of 10.1 in. (0.53 of the cavity radius), the peak power was 3.4 above the core center power. The fraction of fissions occurring above the cadmium cutoff for 0.020-in.-thick cadmium disks (nominally 0.45 eV) was 4.2% and 7.1%, respectively, for these two configurations. 

JARVIS and C. BYERS, AIAA Pi ulslon Joint Specialist Conf., Paper 65-555, Colorado % rings (June 14, 1965). 

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