Experience in the application of a shielded secondary ion mass spectrometer for nuclear reactor material research

A secondary ion mass spectrometer (SIMS) was installed in 1978 in the Hot-Laboratory of the Swiss Paul Scherrer Institute (PSI). The equipment was subsequently modified to allow for the remote handling and analysis of alpha-, beta- and gamma-radioactive samples up to an activity level of 1 MeV GBq. Following an extended period of inactive commissioning including test runs on steel and glass samples, the SIMS was brought into active operation in 1982 as the only shielded instrument worldwide. Since that time, the instrument has been intensively utilized for material research in nuclear fuel cycle optimization. Radial actinide-, fission product- and gadolinium isotopic profiles were determined in uranium (gadolinium) oxide- and (uranium, plutonium)-oxide fuel. The effect of Li uptake and corrosion enhancement in the waterside Zirconium-oxide layer on PWR cladding was studied. Actinide- and fission product-distributions were also analyzed at the cladding inner surface after fuel leaching during reprocessing. Depth profiling was intensely applied to study the concentration profiles of 18 different nuclides through the gel layer of corroded highly active glass samples. SIMS was successfully applied when participating in the OECD project for TMI-2 core debris characterization, to classify groups of elements from fuel and structural material. Included were minor fission products that regrouped following melting to form new ceramic and metallic phases. By using a Cs ion gum, it was possible to quantify the carburization of stainless steel fast breeder reactor cladding following irradiation with uranium plutonium carbide fuel. During the 10 years application of SIMS for radioactive material research, the equipment had to be decontaminated and refurbished on several occasions. The paper reviews the highlights of analytical results gained mainly on non-conducting sample material and evaluates possibilities for future applications in the nuclear fuel cycle with currently available SIMS equipment. (author). 7 refs, 9 figs