A few years ago NASA decided to take another look at one of their projects from the "Golden Age" of space, a compact nuclear reactor for use on extended space missions where batteries and solar panels wouldn't be viable.
Going by the updated acronym of KRUSTY, for Kilopower Reactor Using Stirling Technology, the researchers have built a 1kW test unit loaded with a small amount of Uranium-235. The system is designed to be entirely passive until turned on, and doesn't contain enough radioactive material to go critical and go into a meltdown.
The Stirling engine, which is the component that actually generates the electricity, operates on a temperature differential ie. the heat generated by the nuclear reactor is greater than that of the surrounding environment. The greater the temperature difference, the greater the power produced. The engine was invented back in the early 1800s and has proven the best method of converting heat energy to electrical energy in small, space and weight-constrained applications like spacecraft.
The experiment is ongoing through the northern Spring using a reactor core that has been described as the size of a paper towel roll. Assuming the project gets the go-ahead to progress to a 10kW unit the size will grow to about two metres in height with a large sunshade-style heat radiator. The full size unit is expected to produce the full 10kW of electricity for more than 10 years and would be deployed singly for space probes or in groups of four or more to power camps on the Moon or Mars.
So, why is this project of interest to the maritime community? For starters underwater research labs could certainly make use of the power, as could unmanned underwater vehicles (UUV) and remote monitoring stations.
This would not be the first time that civilian oceanographic researchers have had access to nuclear power. The NR-1 submarine launched in 1969 and operated numerous oceanographic and geological research voyages. The 45-metre-long vessel is the smallest nuclear submarine yet built and remained in US government service until 2008.
Whilst 10kW might now seem like an enormous amount of electrical power, a UUV that spends its time drifting with the subsurface currents would find it more than sufficient for minor course corrections and the occasional journey to the surface and back for data-dumps via satellite. In a subsea oceanographic lab the heat generated might prove to be more valuable than the electricity, allowing for research labs in cooler waters that might not have been viable otherwise.
UUVs could also operate on a "trickle charge" method where a bank of batteries, say a few hundred kilowatt hours, is charged by the generator and once full uses the battery power to transit from point A to point B whereupon it settles onto the seafloor or deploys an anchor and monitors the local area using a small fraction of the generator output as the rest of the electricity goes to recharging the batteries. A fleet of these UUVs could easily form the backbone of a wide area submarine monitoring network.
Because of the small size of the unit decommissioning can be done at a central, specialised facility which would reduce costs. The uranium could be reprocessed with a fair amount of it being reused in new reactor cores and the other radioactive products produced being disposed of responsibly
Production wise, Uranium-235 isn't particularly rare or overly expensive and if a standard reactor were designed these things could be mass-produced to bring the cost down drastically. It's not unreasonable to think these KRUSTY generators could become a plug-and-play power source much like a AA battery.
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