It has been revealed that ailing imaging company Kodak had a secret nuclear reactor hidden in a US research facility for more than 30 years.

The reactor, which contained 1.5kg of enriched "weapons-grade" uranium, was a Californium Flux Multiplier (CFX) acquired by the company in 1974 and only decommissioned in 2006.

But Kodak, which filed for bankruptcy in January, claims that the device was fully licensed and perfectly safe.

"The uranium used in the CFX was highly enriched, but ... was not easily adaptable to creating a nuclear weapon," company spokesman Christopher Veronda told Fairfax Media.