In a blow to Fluor [FLR] and Amentum, the National Nuclear Security Administration (NNSA) said Monday it canceled a potentially 10-year, $28 billion contract for a joint venture of the two companies to manage the agency’s main nuclear-weapon production sites.

The semiautonomous Department of Energy nuclear weapons agency awarded the big-money deal to the Nuclear Production One joint venture in November, but losing bidders quickly protested the award, citing a conflict of interest involving a former NNSA employee who joined a subcontractor of the Fluor team.

“[C]ancellation of the solicitation and termination of the resulting award is appropriate to safeguard the integrity of the procurement process,” the NNSA wrote in a press release issued Monday afternoon.

The agency arrived at the decision after putting the award to Nuclear Production One on hold in December, in the wake of losing bidders’ protests with the Government Accountability Office and reevaluating the award internally. One losing team was led by Bechtel National, another by BWX Technologies [BWXT].

Along with killing the award, the NNSA announced that it will no longer allow one contractor to manage both the Pantex Plant in Amarillo, Texas, the main nuclear-weapons service center, and the Y-12 National Security Complex in Oak Ridge, Tenn., where the agency processes uranium for nuclear-weapon secondary stages.

Instead, as they were before the 2010 experiment to combine their operations to trim administrative costs, Pantex and Y-12 will again be managed under separate contracts for which the agency will solicit bids at some indeterminate point in the future, according to Monday’s press release.

As part of the process, NNSA will create separate federal field offices for Pantex and Y-12, which today are overseen by civil servants in the combined NNSA Production Office.

Meanwhile, Consolidated Nuclear Security (CNS), the incumbent at Pantex and Y-12 will again be extended at the sites, now that the NNSA has scrapped the award to Nuclear Production One. When NNSA decided to boot CNS off the sites in 2020, citing failings in criticality safety and cyber security, among other things, the agency thought the incumbent would be gone by Sept. 30, 2021.

Now, CNS may well be on the job for almost as long as it would have if the NNSA decided in 2020 to pick up the three years of options that were left on the contract, and which could have kept CNS on site into fiscal year 2024.

CNS got its contract in 2012 but did not begin work at until 2014, thanks to a protest by the company now called BWX Technologies, which managed Pantex and Y-12 under separate contracts prior to the sites’ consolidation under CNS.