BES-5, also known as Bouk or Buk (russian: бук, translation=beech), was a Soviet
thermoelectric generator
A thermoelectric generator (TEG), also called a Seebeck generator, is a solid state device that converts heat flux (temperature differences) directly into electrical energy through a phenomenon called the ''Seebeck effect'' (a form of thermoele ...
that was used to power 31 satellites in the
US-A
Upravlyaemy Sputnik Aktivnyy (russian: Управляемый Спутник Активный for Controlled Active Satellite), or US-A, also known in the west as Radar Ocean Reconnaissance Satellite or RORSAT (GRAU index 17F16K), was a series of ...
(RORSAT) project. The heat source was a
uranium 235
Uranium-235 (235U or U-235) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope that exists ...
fast fission nuclear reactor (FNR).
Background
Spacecraft nuclear reactors are typically fast reactors for the following reasons. First, normal moderator materials (carbon, water) add bulk and mass which is not desirable in a spacecraft. Second, for reasons of nucleonics the fuel must be highly enriched to have a lightweight critical mass (similar to small reactor designs on nuclear submarines). Note that some of the
238U (which is fertile and not fissile) will be converted to
239Pu during operation, and this is taken into consideration during the design and while estimating the power output and design life expectancy.
Reactor design
The design of the BES-5 FNR is such that a sub-critical assembly exists into which a rod of fissile material is inserted. Feedback and monitoring of the power level will keep the reactor delayed critical and not
prompt critical
In nuclear engineering, prompt criticality describes a nuclear fission event in which criticality (the threshold for an exponentially growing nuclear fission chain reaction) is achieved with prompt neutrons alone (neutrons that are released immed ...
, which can be done by a mechanical control system.
The fuel core of the reactor was in diameter, long and weighed, as an assembly, , and contained of enriched uranium. The entire reactor, including the radiation shielding, weighed .
The uranium fuel was more than 90% enriched
235U
and generated of electrical power
[A.V Zrodnikov, V.Y Poupko, G.M. Gryaznov, "Experimental detection of neutron gas pressure on the control rods of a nuclear reactor under microgravity conditions", Proceedings of 11 th symposium on space nuclear power and propulsion, January 9–13, 1994, Albuquerque, American Institute of Physics, new York, 1994.] created by thermoelectric conversion of of thermal output.
Use in space
The BES-5 reactor was used in more than 31 satellite missions to power the radar units of the US-A surveillance satellites. The reactor was designed to be boosted to a high orbit at the end of its operational life, to prevent the radioactive fuel from re-entering earth's atmosphere.
There were several mishaps related to failures in the ejection system, most notably
Kosmos 954
Kosmos 954 (russian: Космос 954) was a reconnaissance satellite launched by the Soviet Union in 1977. A malfunction prevented safe separation of its onboard nuclear reactor; when the satellite reentered the Earth's atmosphere the follow ...
, which scattered debris over Canada.
Kosmos 1402
Kosmos 1402 (russian: Космос 1402) was a Soviet spy satellite that malfunctioned, resulting in the uncontrolled re-entry of its nuclear reactor and its radioactive uranium fuel. Kosmos 1402 was launched on August 30, 1982, and re-entered the ...
also re-entered the atmosphere, but burned up over the Atlantic Ocean, away from populated areas. Kosmos 1900 failed to reach its disposal orbit, and remains in low earth orbit.
See also
*
Romashka reactor
The Romashka reactor (russian: Ромашка, translation=chamomile) was a Soviet experimental nuclear reactor. It began operation in 1964, and was developed by the Kurchatov Institute of Atomic Energy. The reactor used direct thermoelectric conv ...
*
SNAP-10A
SNAP-10A (Systems for Nuclear Auxiliary Power, aka Snapshot for Space Nuclear Auxiliary Power Shot, also known as OPS 4682) was a US experimental nuclear powered satellite launched into space in 1965 as part of the SNAPSHOT program.[TOPAZ nuclear reactor
The TOPAZ nuclear reactor is a lightweight nuclear reactor developed for long term space use by the Soviet Union. Cooled by liquid metal, it uses a high-temperature moderator containing hydrogen and highly enriched fuel and produces electricity us ...]
*
List of nuclear power systems in space
This list of nuclear power systems in space includes nuclear power systems that were flown to space, or at least launched in an attempt to reach space. Such used nuclear power systems include:
* radioisotope heater units (RHU) (usually produce he ...
References
{{Reflist
Nuclear power in space
Nuclear technology in the Soviet Union
Satellite nuclear reactors