Mr. Giessner joined the U.S. Nuclear Regulatory Commission (NRC) in 2004 as a Reactor Engineer in Region III. From 2005 to 2008, he was a Resident and Senior Resident Inspector at the Palisades Resident Office. In 2008, Mr. Giessner returned to the Region III office and held progressively responsible positions including Chief, Branch 4; Acting Deputy Director, Division of Reactor Safety; and Deputy Director, Division of Nuclear Materials Safety (DNMS). In 2014, he was selected to be the Deputy Director, Division of Reactor Projects, Region III. In 2015, he was selected as Director, DNMS, and in 2018 he was selected as Deputy Regional Administrator. Mr. Giessner also completed a detail as Acting Deputy Regional Administrator for Region I.
Before joining the NRC, Mr. Giessner was an officer in the U.S. Navy. He also worked at the DC Cook Nuclear Power Plant Station as an Assistant Operations Manager and then Engineering Director. Mr. Giessner was also a Licensed Senior Reactor Operator at the Salem Nuclear Generating Station.
He received a Bachelor’s Degree in Physics from the U. S. Naval Academy and a Master’s Degree in National Security Affairs from the Naval War College. Mr. Giessner is a graduate of the NRC's Senior Executive Service Candidate Development Program.
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