BES-5

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BES-5 reactor
BES-5 type reactor
Generation	Experimental
Reactor concept	Unknown
Status	~29 units in earth orbit
Main parameters of the reactor core
Fuel (fissile material)	235U
Fuel state	37 solid cylinders
Neutron energy spectrum	Fast
Primary control method	six rods, BC 2 with LiH inserts
Neutron reflector	Beryllium
Primary coolant	NaK
Reactor usage
Primary use	US-A satellites
Power (thermal)	100 kW
Power (electric)	1.3–5 kW

BES-5, also known as Bouk or Buk (Russian: бук, lit. 'beech'), was a Soviet thermoelectric generator that was used to power 31 satellites in the US-A (RORSAT) project. The heat source was a uranium 235 fast fission nuclear reactor (FNR).^{[citation needed]}