EnviroReporter.com wrote about the SNAP reactor’s two partial meltdowns in a September 23, 2004 Ventura County Reporter article entitled “In Hot Water – More good news about contamination from your friends at Rocketdyne,” where it was noted:
“At the meeting last week, Rocketdyne divulged that two new wells had high levels of tritium registering approximately 82,000 and 15,400 picocuries per liter near two former Systems for Nuclear Auxiliary Power (SNAP) reactors that were designed for use in space. The SNAP 8 Experimental Reactor Facility suffered a major accident in 1964 in which 80 percent of its nuclear fuel rods cracked and released radiation from the unconfined building. An adjacent SNAP 8 Development Reactor suffered a similar fate in 1969, with about a third of its fuel also cracking. Tritium readings near the most infamous Rocketdyne site, the Sodium Reactor Experiment that experienced a partial meltdown in 1959, registered only background levels of the radionuclide.”
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SNAP-10A was the only nuclear reactor launched and flight tested by the United States. The reactor was developed under the Systems Nuclear Auxiliary Power Program (SNAP) program overseen by the U.S. Atomic Energy Commission.
Launched by an ATLAS Agena D rocket on April 3, 1965, SNAP-10A maintained a low earth orbit for 43 days, while its nuclear electrical source, made up of thermoelectric elements, provided over 500 watts of electrical power.
An on-board voltage regulator within the spacecraft -- unrelated to the SNAP reactor itself -- failed, causing the reactor core to be shut down. The reactor was left in a 700-nautical-mile (1,300 km) earth orbit having an expected duration of 4000 years
The SNAP-10A has three major components: a compact nuclear reactor, the reactor reflector and control system, a heat transfer and power conversion system.
The reactor measured 22.4 cm wide by 39.62 cm long and held thirty seven fuel rods containing uranium-zirconium-hydride fuel.
The SNAP-10A reactor was designed for a power output of 30 kWt and unshielded weighed 650 lb (290 kg)
The reactor can be identified at the top of the SNAP-10A unit.
Reflectors were arranged around the outside of the reactor to provide the means to control the reactor. The reflectors were composed of a layer of beryllium which would reflect neutrons thus allowing the reactor to begin and maintain the fission process.
The reflectors were held in place by a retaining band anchored by an explosive bolt. When the reflector was ejected from the unit, the reactor could not sustain the nuclear fission reaction and the reactor permanently shut down.
The eutectic sodium-potassium (NaK) alloy was used as a coolant in the SNAP-10A. The NaK was circulated through the core and thermoelectric converters by a liquid metal direct current conduction-type pump.
The thermoelectric converters (identified as the long white 'apron') were doped silicon germanium materials thermally coupled but electrically isolated from the NaK heat transfer medium.
The temperature difference between the NaK on one side of the thermoelectric converter and the cold environs of space on the other created an electric potential and usable electricity.