Space debris from a nuclear fission reactor
|SNAPSHOT-10, the first US nuclear powered reactor flow in space. From: Wikipedia.
In the 70s, the spacecraft began shedding parts. It's not certain why this occurred, presumably due to some type of a system failure or due to a collision by space debris. In any case, there is now a cloud of debris in space associated with this spacecraft. It's not certain what this cloud of debris consists of, but probably there are droplets of sodium-potassium liquid metal coolant and maybe fragments of the spacecraft.
I stumbled upon this interesting factoid is when investigating two clusters of space debris that I identified in a recent beam-park radar observation using the Tromsø and Svalbard radars. There are two clear clusters of space objects, which are not within the NORAD catalog of space objects. These are at an altitude of about 1300 km, and they occur around 10 and 22 UTC. You can see these clusters in the figure shown below. It is perhaps not a coincidence that these cluster occur at the same range and time as the expected crossing of the SNAP-10A spacecraft. The reason for the clustering is somewhat unknown. For an old fragmentation event, one would expect the cloud of debris to have dispersed more -- but it is hard to say without more modeling.
Here's a short documentary about SNAP-10A on youtube: