This is a pretty narrow-cast post. I figure frequent commenter Jeff Gauch and one or two other nucs read the blog, and might find it of interest.
In the late 1950s, the Army was looking to small nuclear reactors to provide power to certain remote locations, such as DEW Line sights, where resupply of fuel for conventional generators was problematical at best.
And so the Atomic Energy Commission commissioned the design and construction of a prototype small powerplant know as the Argonne Low Power Reactor. Later known as the SL-1, the reactor was built in Idaho, and training of Army personnel to operate it began under the supervision of the operating contractor, Combustion Engineering.
On January 3rd, 1961, the reactor was shut down for routine maintenance. Three Army personnel were conducting that maintenance. An error in manually withdrawing one of the control blades too far allowed a “prompt critical” incident. For us non-nucs, basically a the reactor not only achieved a criticality, it reacted at a far, far greater rate than normal power generation. Not an explosion, per se, but the criticality formed a steam bubble instantly inside the pressure vessel. The steam formed so rapidly that rather than rising to the top of the vessel, it instead pushed the cold water above it up like a slug, displacing the vessel itself, and blasting the control rod mechanisms free from their fittings at the top of the vessel. Two of the three Army personnel were killed instantly. The third was found alive by first responders, but died during transport to medical facilities.
The reactor pressure vessel was breached, and considerable nuclear materiel and other radioactive contamination was released into the reactor building, with small amounts released to the outside environment. It would take eighteen months to dismantle the reactor building, decontaminate the site, and determine the cause of the accident.
This was the first, and to date, worst, reactor accident in US history.
Jeff and the other nucs have almost certainly heard of the incident. They may appreciate this AEC report on it.
The latter parts of the film show the actual reactor, fuel plates and control blades and associated fittings.