Nuclear Space Application Program The Martian Surface Reactor: An Advanced Nuclear Power Station for Manned Extraterrestrial Exploration A. Bushman, D.M. Carpenter, T.S. Ellis, S.P. Gallagher, M.D. Hershcovitch, M.C. Hine, E.D. Johnson, S.C. Kane, M.R. Presley, A.H. Roach, S. Shaikh, M.P. Short, M.A. Stawicki MIT-NSA-TR-003 December 2004MSR - Abstract - i - Abstract As part of the 22.033/22.33 Nuclear Systems Design project, this group designed a 100 kWe Martian/Lunar surface reactor system to work for 5 EFPY in support of extraterrestrial human exploration efforts. The reactor design was optimized over the following criteria: small mass and size, controllability, launchability/accident safety, and high reliability. The Martian Surface Reactor was comprised of four main systems: the core, power conversion system, radiator and shielding. The core produces 1.2 MWth and operates in a fast spectrum. Li heat pipes cool the core and couple to the power conversion system. The heat pipes compliment the chosen pin-type fuel geometry arranged in a tri-cusp configuration. The reactor fuel is UN (33.1w/o enriched), the cladding and structural materials in core are Re, and a Hf vessel encases the core. The reflector is Zr3Si2, chosen for its high albedo. Control is achieved by rotating drums, using a TaB2 shutter material. Under a wide range of postulated accident scenarios, this core remains sub-critical and poses minimal environmental hazards. The power conversion system consists of three parts: a power conversion unit, a transmission system and a heat exchanger. The power conversion unit is a series of cesium thermionic cells, each one wrapped around a core heat pipe. The thermionic emitter is Re at 1800 K, and the collector is molybdenum at 950 K. These units, operating at 10+% efficiency, produce 125 kWe DC and transmit 100 kWe AC. The power transmission system includes 25 separate DC-to-AC converters, transformers to step up the transmission voltage, and 25 km of 22 gauge copper wire for actual electricity transmission. The remaining 900 kWth then gets transmitted to the heat pipes of the radiator via an annular heat pipe heat exchanger that fits over the thermionics. This power conversion system was designed with much redundancy and high safety margins; the highest percent power loss due to a single point failure is 4%. The radiator is a series of potassium heat pipes with carbon-carbon fins attached. For each core heat pipe there is one radiator heat pipe. The series of heat pipe/fin combinations form a conical shell around the reactor. There is only a 10 degree temperature drop between the heat exchanger and radiator surface, making the radiating temperature 940 K. In the radiator, the maximum cooling loss due to a single point failure is less than 1%. The shielding system is a bi-layer shadow shield that covers an 80º arc of the core. The inner layer of the shield is a boron carbide neutron shield; the outer layer is a tungsten gamma shield. The tungsten shield is coated with SiC to prevent oxidation in the Martian atmosphere. At a distance of 11 meters from the reactor, on the shielded side, the radiation dose falls to an acceptable 2 mrem/hr; on the unshielded side, an exclusion zone extends to 14 m from the core. The shield is movable to protect crew no matter the initial orientation of the core. When combined together, the four systems comprise the MSR. The system is roughly conical, 4.8 m in diameter and 3 m tall. The total mass of the reactor is 6.5 MT.MSR - Acknowledgements - ii - Acknowledgements The design team would like to acknowledge our advisor Professor Andrew Kadak for creating such an exciting project for us to work on and coordinating our efforts with the Department of Aeronautics and Astronautics to provide context and meaning to our work. We would also like to extend our thanks to him for giving us feedback at every major milestone of the project. Peter Yarsky, the Teaching Assistant for this class, was an invaluable guide and resource to the design team. He tirelessly answered our questions, provided us extra material to consider, edited our chapters, prepared us for our final presentation and generally supported us every step of the way. The design team would like to sincerely thank Mr. Yarsky for going above and beyond his role as a TA; in addition to his technical expertise, his enthusiasm for this project sustained ours. We would like to extend our deepest gratitude to Joseph Palaia, a graduate student in the Nuclear Science and Engineering Department. In addition to helping us locate information relevant to Martian operation, he spent countless hours with our group creating CAD drawings of the MSR system. The design team would like to thank the Nuclear Science and Engineering Department of MIT for supporting our project, and the faculty for answering our endless stream of questions. Graduate student Marc Berte supplied valuable feedback on our initial design. We would like to extend a special thanks to Professors Linn Hobbs, Michael Golay, Elias Gyftopoulos, and Neil Todreas for taking the time to come to a preliminary presentation and critiquing our work. Additionally, we would like to express our appreciation to Dr. Larry Foulke of Bechtel Bettis, Dr. Paul Baldasaro of Knolls Atomic Power Laboratory, and Dr. Ady Hershcovitch of Brookhaven National Laboratory, for attending our final presentation and providing insightful commentary and critique of the MSR design. Finally, the design team would like to acknowledge Professor Jeffrey Hoffman of the Department of Aeronautics and Astronautics at MIT for being a resource for information specific to space and extraterrestrial exploration.MSR - Table of Contents - iii - Table of Contents Abstract................................................................................................................................ i Acknowledgements............................................................................................................. ii Table of Contents...............................................................................................................iii List of Figures................................................................................................................... vii List of Tables ...................................................................................................................... x 1