[falling]

as you can read from what I think is the original source (http://www.democratandchronicle.com/article/20120511/NEWS01/...) californium was the neutron source and uranium was used in the multiplier.

«A steady stream of neutrons is needed for these purposes. Kodak used small research reactors, including one at Cornell University, and possessed a dollop of californium-252, a radioactive isotope that endlessly sheds neutrons.

But it wanted a more potent in-house system, so in 1974 it acquired a californium neutron flux multiplier, known as a CFX. Small plates of highly enriched uranium multiplied the neutron flow from a tiny californium core.»

[mcclung]

Reading the original source completely changes everything. Thank you.