William Bookless will resign as acting administrator of the National Nuclear Security Administration (NNSA) on inauguration day, Jan. 20, setting up career civil servant David Huizenga to shepherd the nuclear-weapons agency through the early days of the Joe Biden administration.

Bookless announced his impending departure Monday in an all-hands memo to NNSA staff. Bookless has led the semiautonomous Department of Energy agency since the first week of November, when Secretary of Energy Dan Brouillette demanded that Lisa Gordon-Hagerty resign as administrator.

“Working alongside all of the dedicated women and men of the NNSA these past two years has been the pinnacle of my 43-year association with the Department of Energy and NNSA,” Bookless wrote in the memo. “Led by former Administrator Gordon-Hagerty, and in conjunction with the Department of Defense, we developed a compelling case that has resulted in unprecedented support from the Administration and bipartisan support from Congress that will enable us to take our modernization efforts to the next level and turn back decades of deterioration of our infrastructure and loss of capability.”

Bookless joined the NNSA in May 2019. With his swearing-in, former Lawrence Livermore National Laboratory PhDs occupied two of the four senior political leadership positions at the NNSA that required Senate confirmation. Charles Verdon, the deputy administrator for defense programs, was the other Livermore alum in such a slot.

With the DoE veteran Huizenga poised to take the reins until the Biden administration appoints its own leadership, the civilian weapons agency can hope to avoid some of the leadership churn that followed after the Obama administration’s last administrator, retired Air Force Lt. Gen. Frank Klotz, left the NNSA in early 2018.

In the month-or-so gap between Klotz and Gordon-Hagerty, William “Ike” White, chief of staff to Klotz and then-associate principal administrator, was in line to be acting, until the agency appointed Steve Erhart, then director of NNSA’s Office of Policy and recently retired from DoE, as the agency’s temporary steward.

When Gordon-Hagerty came aboard, she shook up the organization, splitting the chief-of-staff role and the associate principal administrator role and promoting Huizenga to the latter position after years as the number-two in the NNSA’s Office of Defense Nuclear Nonproliferation. The goal was to backstop NNSA’s appointed leadership with a steady, career hand.

Huizenga has also had a long stint in a senior leadership position outside the NNSA, leading DoE’s massive effort to clean up shuttered nuclear weapons production sites as acting assistant secretary for environmental management. He held the position for four years during the Obama administration.