Zero Power Tests, SM-1A Core III

Abstract

The zero power tests on SM-1A Core III were performed at The Babcock & Wilcox Company's Critical Experiment Laboratory in Lynchburg, Virginia. The core was assembled using grid plates, a skirt, control rod boxes, and a shield mockup especially constructed for the tests. The results are summarized below. 1. The plant-site instrument response was established for the core loading sequence. 2. The differential and integral worths of all seven rods were measured from the initial clean critical position to the fully withdrawn position using boric acid in the moderator for holddown. The differential worth at the clean critical position (25.3 cm withdrawn) is 85 cents/cm; the total excess reactivity (/cap delta/k/k) of the core is 0.0899. 3. The critical positions for a variety of rod patterns were measured. The stuck-rod measurements showed that the core was subcritical with any three rods fully withdrawn. 4. The temperature coefficient of reactivity was measured from 20 to 70 C for both five-rod bank and seven-rod bank cases. The coefficient changes from -0.7 cents/$sup o$C to -2.1 cents/$sup o$C over this range. A slight difference was noted between the two cases. 5. The spare fuel assemblies were shown to have almost the same reactivity as the normal fuel assemblies have; the difference is only 2.5 cents. 6. Fast and thermal fluxes were measured from the center of the core to the mockup pressure vessel. The fast flux was attenuated by a factor of 2 x 10 $sup 4$. In absolute units, the fast flux is approximately 4.2 x 10$s4$ neut/cm2-sec-watt at the pressure vessel wall. (author)