Closed Brayton Cycle Power Conversion Research Articles

Neutronics Analysis of Small Compact Prismatic Nuclear Reactors for Space Crafts

Due to the advantages of small volume, light weight, and long-time running, nuclear reactor can provide an ideal energy source for space crafts. In this paper, two small compact prismatic nuclear reactors with different core block materials are presented, which have a thermal power of 5 MW for 10 years of equivalent full power operation. These two reactors use Mo-14%Re alloy or nuclear grade graphite IG110 as core block material, loaded with 50% and 39.5% enriched uranium nitride (UN) fuel and cooled by helium, whose inlet/outlet temperature of the reactor and operational pressure are 850/1300 K and 2 MPa, respectively. High temperature helium flowing out of the reactor can be used as the working medium for closed Brayton cycle power conversion with high efficiency (more than 20%). Neutronics analyses of reactors for the preliminary design in this paper are performed using reactor Monte Carlo (RMC) code developed by Tsinghua University. Both the reactors have enough initial excess reactivity to ensure 10 years of full power operation without refueling, have safety margin for reactor shutdown with one control drum failed, and remain subcritical in the submersion accident. Finally, the two reactors are compared in aspect of the 235U mass and the total reactor mass.

Model Fidelity Requirements for Closed-Brayton-Cycle Space Power Systems

C LOSED-BRAYTON-CYCLE (CBC) power conversion is one technology that can be used in space power systems for spacecraft, surface bases, and planetary rovers.More than 270works on Brayton space power system topics appear in the literature over the last 30 years. Brayton system conceptual designs for milliwatt to megawatt power converters have been developed [1–9]. When optimizing a CBC power conversion system (PCS), numerous factors affect overall system performance; a partial list includes turbomachinery efficiency, heat exchanger effectiveness, workingfluid composition, and cycle temperatures and pressures. The present work also addresses the significance of compressor bleed flows and different internal loss mechanisms. Unfortunately, in much of the literature, CBC modeling fidelity is unclear. If items such as the aforementioned factors are not specifically addressed, a reader cannot confidently rely on the results. Effecting CBC model improvements, the present work has two objectives: to demonstrate system-level impacts of fidelity differences in CBC models and to recommend a minimum CBC modeling fidelity for conceptual design studies.

Predicting the Behavior of Solar Dynamic Closed Brayton Cycle Power Conversion Systems

Since space power conversion systems must operate both in the sun and in the earth’s shadow, they seldom encounter design operating conditions. As a consequence, consideration of off-design performance is essential in the preliminary design of these systems. To illustrate the necessity and utility of an off-design system model, this paper presents the results of a study of the solar dynamic closed Brayton cycle power conversion system for use on the NASA Space Station.

Closed Cycle Gas Turbine as a Proposed Undersea Power Source

Undersea application of compact and lightweight closed Brayton cycle power systems currently being developed for space is discussed. Design details of a 50 kwe hydrogen-oxygen fueled system for a short-duration undersea mission of 1000 kw-hr are presented. For this same mission, a new hydrogen-oxygen injection gas turbine cycle is described. Performance characteristics of undersea long-duration 10 to 150 kwe power systems, using radioisotope and nuclear reactor heat sources, are also presented. Development status of closed Brayton cycle power conversion systems is presented.