Negative transferred arc cleaning: a method for roughening and removing surface contamination from beryllium and other metallic surfaces

TA cleaning has been investigated for preparing the surface of beryllium plasma facing components (PFC's) inside of the international thermonuclear experimental reactor (ITER) prior to depositing beryllium by plasma spraying. Plasma spraying of beryllium was evaluated during the ITER engineering design activity (EDA) for in-situ repair and initial fabrication of the beryllium first wall armor. Results have shown that surface roughening of beryllium, during the TA cleaning process, can result in bond strengths greater than 100 MPa between beryllium surfaces and plasma sprayed beryllium. In addition, the TA cleaning process was shown to be an effective method for removing contaminate layers of carbon and tungsten from the surface of beryllium. Investigations have been performed to characterize the different arc-types that occur during the TA cleaning process (type I, I and III arcs) and the effectiveness of the TA cleaning process for potentially removing co-deposited layers of carbon and deuterium from the surface of beryllium, stainless steel and tungsten. (orig.)