Californium-252 Sources (1970s, 1980s)

These photos show two different dummy source capsules for californium-252. Californium-252 is produced in the High Flux Reactor at Oak Ridge National Laboratory by the neutron irradiation of uranium, and is used exclusively as a neutron source. 

The photo below shows a dummy source (6" long, 3/4" diameter) attached to a 44" stainless steel cable. The source itself is solid steel and has "dummy" etched on the side. It was produced at either Oak Ridge Associated Universities or Oak Ridge National Laboratory, and would have been used to practice the loading and unloading of sources.

The photos to the right and below show a different dummy source capsule. This one was manufactured at Oak Ridge National Laboratory. It is approximately 6" long (including the stem) and 3/4" in diameter.

The outer capsule has a threaded top with a stem on it that could be picked up by a handling device. The stem has a flat section so that it can be more easily gripped for threading or unthreading the cap. There are two welded stainless steel capsules inside the outer capsule—each of these is 1 1/2" long and 1/2" in diameter. Inside each of these is a smaller welded stainless steel container in which the californium would be loaded.

Actual source capsules similar to these dummies would have been used to hold something like 1 to 20 milligrams of californium.

Californium-252 primarily decays by alpha emission, but a certain percent of the time it "decays" by spontaneous fission. When an atom of Cf-252 fissions, it usually emits 3 to 4 neutrons. The average energy of the neutrons is in the 4 to 5 MeV range but some will have energies up to 10 MeV. The problem with Cf-252 is its relatively short half-life of 2.6 years.