[23] In 1965, UNC won a contract from the Atomic Energy Commission to operate the reactor and fuel fabrication facilities at the AEC's plant.

[43] The next year, 1979, saw the company's second nuclear incident, when a dam at their Church Rock mine broke, leaking radioactive waste into a tributary of the Puerco River.

[44] In 1984, following the decline of the uranium industry near the end of the cold war,[45] the United Nuclear Corporation rebranded to "UNC" and transitioned over the next decade into a business aviation and jet engine service provider.

Ambrosia Lake was a uranium mine and mill built in 1957 and operated by the Phillips Petroleum Company[21] until it was purchased by UNC in 1963.

[48][50] The Church Rock uranium mine and mill, located in McKinley County, New Mexico, first began exploration in 1968 as the company looked to expand its operations to meet demand.

[44][51][52] In 1983 the site was added to the Environmental Protection Agency's the National Priorities List, following investigations and minor cleanup efforts in the previous four years.

[53][54] In 1997, following their purchase by General Electric, the Nuclear Regulatory Commission fined UNC $100,000 for failing to set aside funds for the decommission of the site.

[55] In 2008, a five-year plan for the cleanup of contaminated uranium sites on the Navajo reservation, of which Church Rock is part, was authorized.

[23] As a result of the incident, the Atomic Energy Commission charged UNC with 14 violations of nuclear safety regulations, however no fines were ever levied against the company.

[62][65] In 1979 Combustion Engineering applied to decommission the site, however the proposal was rejected because decontamination and disposal activities were not included in the plan.

The most notable of these was conducted in 1983 by the Radiation Management Corporation with the goal of discovering the sites Mallinckrodt and UNC had used to dispose of nuclear waste.