In 1954, Claus oversaw the testing of samples from the Marshall Islands for radioactivefallout from the Castle Bravo explosion. From 1949-1955 he held the position of Chief in the Division of Biology and Medicine, AEC. Then from 1955-1967 he served as Special Assistant to Division Director, AEC.
Claus was a key member in the formation of the Health Physics Society and represented the U.S. Atomic Energy Commission. In 1955, he was one of the founding members and part of the initial board of directors. He would also serve as the society's president during 1961 and 1962.