“SAIRS” — Scalable Amtec Integrated Reactor space power System

Abstract

Conceptual Designs of three, 111 kWe, Scalable AMTEC Integrated Reactor Space Power Systems (SAIRS) are developed. These systems employ fast-spectrum reactors cooled by sodium (Na) heat pipes, C-C armored, potassium (K) heat pipes radiators, and Alkali Metal Thermal-To-Electric Conversion (AMTEC) units. The reactor Na- and the radiator K-heat pipes operate at <47% of their prevailing capillary and/or sonic limit. The reactor core is comprised of 60 modules, each has 3 UN fuel pins with rhenium (Re) cladding brazed to a central Na/Mo-14%Re heat pipe of the same OD (1.5 cm). Although heavy, Re is compatible with UN fuel and an effective Spectral Shift Absorber (SSA) that ensures reactor's sub-criticality when fully submerged in wet sand or water, following a launch abort accident. Each of the 6 radiator panels in SAIRS has 6 double-vapor-cavity potassium heat pipes for removing the rejected heat from one of six AMTEC blocks. Each block consists of either 3 or 4 Na-AMTEC units that are heated by ten reactor Na-heat pipes. The AMTEC unit measures 410 × 594 × 115 mm in outside dimensions and weights 44.3 kg. These units are connected in series in 3 or 4 parallel strings for redundancy, while providing a terminal voltage of 400 V DC. At an AMTEC cold side temperature of 700 K and reactor exit temperatures of 1202 K, 1176 K and 1133 K, the nominal efficiencies of the three SAIRS options are 27.3%, 26.9% and 22.7% respectively, resulting in low system masses. The Na-AMTEC units in SAIRS operate at 64–86% of their peak electrical powers, providing for up to 14–36% passive load-following increase in demand without actively increasing the reactor power. The three SAIRS options are identical, except in the efficiency and the number (18 or 24) and electrical connections of Na-AMTEC units, and have alphas ≤30.5 kg/kWe and total heights and major diameters of ≤6 m and ≤4 m, respectively.