Advanced two-phase flow instrumentation program

The performance of the Westinghouse Reactor Vessel Level Indicating System (RVLIS) during tests S-UT-6 and S-UT-7 (5% cold-leg breaks in the Semiscale Test Facility) was analyzed. The RVLIS, a system employing differential pressure (dP) cells, gave estimates of vessel level similar to those of Semiscale level instrumentation when measuring over equal spans. These RVLIS measurements are conservative to vessel coolant levels for both S-UT-6 and S-UT-7. At times, the RVLIS indications are greater than the vessel collapsed liquid level measured by Semiscale instrumentation. During S-UT-6, level estimate differences between RVLIS and Semiscale dPs of up to 215 cm (85 in.) were observed. These discrepancies may be explained by differences in Semiscale and Westinghouse pressurized-water reactor internal designs. Excellent agreement was noted between Semiscale and Westinghouse vessel levels for S-UT-7, an upper-head injection test.