NISKAYUNA — Federal officials are seeking state permission to store radioactive waste at Knolls Atomic Power Labs, where it was collected during the troubled decade-long cleanup of a Cold War-era atomic research facility.

The state Department of Environmental Conservation is reviewing an application from the U.S. Department of Energy to "safely store 22 containers of radioactive and chemically hazardous waste" at the site until an outside treatment and disposal facility can be found.

The waste is the result of a DOE-managed cleanup at the facility's former Separations Process Research Unit that began in 2006. The buildings were used during the 1950s in experiments to extract uranium for atomic weapons development.

According to DOE paperwork, there are more than 2,600 gallons of so-called transuranic (TRU) waste. That means waste which has been "contaminated with alpha emitting transuranic radionuclides."

This type of waste is a byproduct of weapons production, and requires special precautions for safe disposal.

In October 2015, DOE notified DEC that "due to temporary and uncontrollable circumstances" this waste could not be shipped offsite to comply with limits on storage time, according to DOE paperwork.

Currently, the DOE uses a special disposal facility in the desert near Carlsbad, N.M., called the Waste Isolation Pilot Plan. The $19 billion facility is meant to permanently dispose of TRU radioactive waste for 10,000 years.

"A national backlog for shipment and disposal of all TRU wastes has resulted in the need to store

this waste (at Knolls) for greater than 90 days," the DOE stated. The waste is currently being kept in four so-called Conex metal shipping containers "for radiation shielding and weather protection."

The radioactive waste could remain in Niskayuna for several more years while that backlog is reduced.

Officials at DOE, which in February held a public hearing on the radioactive waste storage issue, said that the cleanup process at the Niskayuna facility should be completed later this year. In October, DOE announced that workers had begun "the last phase of building demolition" at the facility.

DEC received the DOE application on March 29 to continue the radioactive waste storage. That application is being reviewed, the state agency said Monday.

The initial cleanup contract at Knolls was for about $69 million, but the project was hit with delays after it was revealed that workers accidentally allowed radiation to get into the air during demolition. Total costs had ballooned to about $145 million by 2012.

In 2014, DOE agreed to pay a $155,000 fine after admitting that workers in 2006 and 201o had released three different forms of radiation — Cesium-137, Americium-241 and Plutonium-239. Some radioactivity got into the ground and washed into the nearby Mohawk River.

The cleanup has involved five of the facility's 170 acres, including two buildings.

The project was shut down by DOE in late 2010 amid safety concerns. In March 2012, the U.S. Environmental Protection Agency issued an order requiring numerous safety measures; work resumed in 2013.

Note: An earlier version of this story included an inaccurate number for the amount of waste stored at the facility.