3-DIMENSIONAL ELASTIC RECOIL DETECTION ANALYSIS OF HYDROGEN IN MATERIALS FOR USE IN THE YUCCA MOUNTAIN NUCLEAR WASTE REPOSITORY

An original system has been developed capable of performing three-dime nsional Energy Recoil Detection Analysis (ERDA) of hydrogen in materia ls with scanned and finely focused heavy-ion beams. The technique is b eing used at the Lawrence Livermore National Laborotory Multi-user Tan dem Laboratory to measure the hydrogen content in materials under cons ideration for use in the Yucca Mountain nuclear waste repository. From the measurement of hydrogen concentration profiles we can extrapolate reaction rates. A critical problem is the rate of dissolution of the glass being used. The HI-ERDA (Heavy Ion-ERDA) technique can provide t his information which is needed in order to predict the overall rate o f nuclear waste glass degradation in a waste repository. The technique is calibrated using a silicon wafer implanted with a known concentrat ion of hydrogen. The sample is illuminated by a Cl-35 ion beam that is micro-scanned across the sample. From these measurements we reconstru ct three dimensional profiles of hydrogen content which can then be us ed to obtain spatially-resolved hydrogen depth profiles. (C) 1997 Else vier Science B.V.