Rick Perry, Vogtle, Plutonium Letter (copy)

U.S. Secretary of Energy Rick Perry, a former governor of Texas, pictured here during a visit to Plant Vogtle earlier this year.

A Democratic congressman is demanding the immediate resignation of U.S. Secretary of Energy Rick Perry, as his colleagues and other officials blast the U.S. Energy Department for what they call "egregious" – if not negligent – acts, driving another wedge between the already feuding parties.

U.S. Rep. Steven Horsford of Nevada on Wednesday said Perry should step down following revelations the department shipped noncompliant, and potentially mischaracterized, waste to the Nevada National Security Site over a period of six years.

Horsford's congressional district, the fourth, includes NNSS, which is about two hours northwest of Las Vegas.

"Today we found out that, against the will and consent of Nevadans, the Department of Energy has been covertly shipping dangerous radioactive waste into our state. While the DOE has long claimed it supports collaboration with the state of Nevada, today's findings, like those of the recent past, prove otherwise," the congressman said in a prepared statement posted to his website.

That statement ostensibly calls back to a half-metric ton of defense plutonium that was sent from the Savannah River Site to NNSS last year, a court-driven campaign that roiled lawmakers and sparked a war of words.

"Secretary Perry has repeatedly disrespected the people of Nevada," Horsford said in a Wednesday evening tweet.

U.S. Deputy Secretary of Energy Dan Brouillette contacted Nevada Gov. Steve Sisolak July 3 to discuss the waste that was recurrently sent from the Y-12 installation in Tennessee to Nevada for disposal. Two days later, the governor and U.S. Sens. Catherine Cortez Masto and Jacky Rosen – all Democrats – sent a letter to Perry detailing health concerns and pressing for answers and oversight.

"The implications could be significant for both our environment and public health," Horsford said separately. He added, "The people of Nevada adamantly oppose the storage of nuclear waste in Nevada."

A spokesperson for the Energy Department, Shaylyn Hynes, in a lengthy statement said what was shipped was handled safely and securely, adding that the general public and site workers aren't at risk. Future shipments from Y-12 have been paused.

Senior officials, including National Nuclear Security Administration chief Lisa Gordon-Hagerty, led briefings with Sisolak and his staff Tuesday.

Nine total shipments – 32 total containers – were sent to NNSS between 2013 and 2018, according to the NNSA, the Energy Department's semiautonomous stockpile and nonproliferation arm. Sisolak's office on Wednesday stated it was 32 total shipments, drawing rebukes.

The NNSA has launched an internal investigation, according to Hynes, "to determine how this went undetected" for six years. Brouillette, at the direction of Perry, has ordered an audit of radioactive waste policies and procedures.

"Secretary Perry remains committed now more than ever to his promise to identify and address challenges within the DOE enterprise, and reaffirm the Department of Energy's credibility and trust in delivering on all aspects of its mission," Hynes said.

This latest nuclear tussle plays out as Nevada, South Carolina and the Energy Department lock horns in an escalating legal battle. The NNSA in 2018 sent a half-metric ton of weapons-usable plutonium to Nevada for staging. That cache will be moved again by the end of 2026, Perry has promised.

"Unfortunately, these latest revelations relating to DOE shipments of radioactive material into Nevada are not anomalous," the governor and the state's two senators wrote in the letter to Perry.

Last year's clandestine operation was made public by NNSA General Counsel Bruce Diamond in a later court declaration. Nevada had sued to prevent the plutonium from even arriving.

The NNSA does not openly discuss the movement of nuclear materials, citing safety and security concerns.

"So I'm not at liberty to discuss the movements, the shipments, the dates, the times, the locations, the routes of those materials," Gordon-Hagerty said during a U.S. House Armed Services Committee hearing. She was responding to U.S. Rep. Joe Wilson, a South Carolina Republican.

Colin Demarest is the government and Savannah River Site reporter with the Aiken Standard. Follow him on Twitter: @demarest_colin