Reactor Start-up and Control Methodologies: Consideration of the Space Radiation Environment
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States)
The use of fission energy in space power and propulsion systems offers considerable advantages over chemical propulsion. Fission provides over six orders of magnitude higher energy density, which translates to higher vehicle specific impulse and lower specific mass. These characteristics enable the accomplishment of ambitious space exploration missions. The natural radiation environment in space provides an external source of protons and high energy, high Z particles that can result in the production of secondary neutrons through interactions in reactor structures. Initial investigation using MCNPX 2.5.b for proton transport through the SAFE-400 reactor indicates a secondary neutron net current of 1.4x107 n/s at the core-reflector interface, with an incoming current of 3.4x106 n/s due to neutrons produced in the Be reflector alone. This neutron population could provide a reliable startup source for a space reactor. Additionally, this source must be considered in developing a reliable control strategy during reactor startup, steady-state operation, and power transients. An autonomous control system is developed and analyzed for application during reactor startup, accounting for fluctuations in the radiation environment that result from changes in vehicle location (altitude, latitude, position in solar system) or due to temporal variations in the radiation field, as may occur in the case of solar flares. One proposed application of a nuclear electric propulsion vehicle is in a tour of the Jovian system, where the time required for communication to Earth is significant. Hence, it is important that a reactor control system be designed with feedback mechanisms to automatically adjust to changes in reactor temperatures, power levels, etc., maintaining nominal operation without user intervention. This paper will evaluate the potential use of secondary neutrons produced by proton interactions in the reactor vessel as a startup source for a space reactor and will present a potential control methodology for reactor startup procedures in the event of source fluctuations.
- OSTI ID:
- 20632869
- Journal Information:
- AIP Conference Proceedings, Vol. 699, Issue 1; Conference: STAIF 2004: 21. symposium on space nuclear power and propulsion: Human space exploration, space colonization, new frontiers and future concepts, Albuquerque, NM (United States), 8-11 Feb 2004; Other Information: DOI: 10.1063/1.1649623; (c) 2004 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
FLUCTUATIONS
MONTE CARLO METHOD
NATURAL RADIOACTIVITY
NEUTRON FLUX
POWER DENSITY
PROTON TRANSPORT
RADIATION EFFECTS
REACTOR COMPONENTS
REACTOR CONTROL SYSTEMS
REACTOR OPERATION
REACTOR START-UP
REACTOR VESSELS
SECONDARY EMISSION
SOLAR FLARES
SPACE PROPULSION REACTORS
STEADY-STATE CONDITIONS
NESDPS Office of Nuclear Energy Space and Defense Power Systems