Gary Wisdom, security chief in the National Nuclear Security Administration’s Production Office (overseeing Y-12 and Pantex), left federal service last week and has been replaced by Arnold Guevara. Guevara has served as director of the DOE’s Office of Headquarters Security Operations in Washington, D.C. and is transitioning to the NNSA Production Office. He’s expected to be full time by September.

It’s not immediately clear where Guevara will be based, Oak Ridge or Amarillo. Wisdom, who was a part of the NPO leadership team from its inception in June 2012, was based in Amarillo but spent a lot of time in Oak Ridge — particularly because of the last year’s security breach and all of the attention paid to that event and the subsequent improvements.

Wisdom’s departure was apparently a surprise to many. In a statement, NPO Manager Steve Erhart said: “It is with a very heavy heart for me to announce that Gary Wisdom has informed me of his plan to leave Federal service . . . I have accepted his decision, but with tremendous regret for the loss of an outstanding leader and a true professional.  He is one of the most respected and accomplished leaders in the Department of Energy for the management of strategic and operational nuclear safeguards and security.”

Erhart called Guevara a “highly respected security professional and very capable” and said he was delighted to have him join the NPO team.

Wisdom, a former Marine, has more than 30 years of government service. He held management positions at DOE headquarters and the Site Office at Pantex and also at one time was chief of security operations at the Rocky Flats Plant in Colorado.