Experimental and Analytical Study of Steam Turbine Two-Phase Operation in Nuclear Reactor Cooling Systems

Abstract

Prior to Fukushima accident, the Reactor Core Isolation Cooling (RCIC) system operational limits were based on manufacturers data, in which the system’s Terry turbine and pump were assumed to be ideal. The Beyond Design Basis Event (BDBE) operating conditions were evaluated according to conservative Probabilistic Risk Assessment (PRA) applications.

In response to the current lack of knowledge and poor understanding of RCIC system performance under BDBE conditions, the current study investigates the Terry turbine performance at BDBEs using steam-water mixtures. These tests serve to expand the available database for model development, validation and verification, and dimensional analysis, in a cost-effective manner without the potential of severely damaging a nuclear grade full-scale Terry Turbine.

Additionally, single-phase air tests were also performed during the current testing efforts to benchmark against previous data bases of air and air-water data of a small-scale and full-scale Terry turbines. These tests will inform proposed full-scale experimental design and testing. The tests described herein were conducted at conditions as close as possible to those which were recorded during operation of plant RCIC systems and therefore provide essential data for scaling from small laboratory sizes up to full-scale RCIC system size. Toward that end, a complete set of nondimensionalized characterization of the small-scale turbine has been performed at different steam inlet pressures, back pressures, and steam qualities.

Over 20 US BWRs employ a RCIC system. If the RCIC System can be shown efficient over a wider range of conditions, the plants would like to have more cost savings and additional safety margin.