Supercritical CO2 Brayton Cycle Integrated System Test (IST) Design and Construction

by Eric Clementoni
Bettis Atomic Power Laboratory

Complete Paper to be Available Following the 2011 Supercritical CO2 Power Cycle Symposium

The Naval Nuclear Propulsion Program (NNPP) S-CO2 Brayton Cycle Integrated System Test (IST) is being built and operated at the Bettis Atomic Power Laboratory. The IST is a two shaft recuperated closed Brayton cycle with a variable speed turbine driven compressor and a constant speed turbine driven generator using S-CO2 as the working fluid. The purpose of the IST is to gain experience in the startup and operation of an integrated S-CO2 Brayton system, provide test data over a range of operating conditions and transients that an S-CO2 Brayton cycle may experience, demonstrate that the cycle can be controlled over these conditions, and determine if there are any fatal flaws in the concept. The IST is heavily instrumented and was designed for precise control of operations over a wide transient range of heating, cooling and power conditions. The test objectives of the IST include: demonstrate the controllability of a S-CO2 Brayton Cycle; compare control system options; determine loop component performance; focus on control of compressor inlet conditions; verify turbomachinery performance predictions; confirm heat exchanger performance predictions; and to evaluate bearings, seals, and generator cooling techniques. Pressure systems and components structural design was evaluated via techniques in the ASME Boiler and Pressure Vessel Code Section VIII, Division 2 to ensure safe operations of the IST under conditions for which no direct previous experience base existed. The main test loop and support systems have been constructed and are undergoing shakedown operations in advance of testing scheduled to commence in mid 2011. A discussion of the major components, instrumentation and control, and support systems is provided along with a representative IST heat balance.