Mr. Giessner is the RIII Regional Administrator. Prior to his appointment as Region III Regional Administrator in April 2020, he served as the Deputy Regional Administrator. Before that, Mr. Giessner served as the Director for the Division of Nuclear Materials Safety. Mr. Giessner graduated in 1983 from the U.S. Naval Academy and served 13 years on active duty for the US Navy. He qualified and served as Engineer Officer with the US submarine force. He qualified and served as a Joint Staff Officer for the U.S. Strategic Command in the area of Nuclear Force Strategy and Operations. After he left the Navy, he worked for two commercial utilities in the areas of Engineering and Operations. He received his Senior Reactor Operator (SRO) license at the Salem Nuclear Generating Station. Mr. Giessner joined the NRC in 2004 and began his NRC career in 2004 as a Reactor Engineer and later as a Resident Inspector at the Palisades Nuclear Plant in Region III. Mr. Giessner also served as Branch Chief and Deputy Division Director in the Division of Reactor Projects. Mr. Giessner graduated from the NRC’s Senior Executive Service Candidate Development Program.

Mr. Giessner received a BS degree in Physics and a MA degree in National Security Affairs.