LRC - Laboratory of Radiochemistry

Knowledge about the cross sections data of the target materials used for spallation neutron facilities (SNF) and accelerator driven systems (ADS) is essential for the licensing, safe operation and decommissioning of these facilities. In addition, these data are important to evaluate and improve the existing computer simulation codes. Especially the α-emitter ¹⁴⁸Gd has a large contribution to radio-toxicity of spallation target facilities with its 74.6 years of half-life.

One of the long-lasting unsolved problems in Nuclear Astrophysics is the so-called "Cosmological Li Problem", i.e. the large discrepancy between the primordial ⁷Li abundance predicted by models of Big Bang Nucleosynthesis and the one inferred from astronomical observation. The study of the production/destruction rates of the radioactive precursor ⁷Be is one of the clues for solving this problem.

PSI radiochemists now finished the radiochemical analysis of the residue nuclei production in the Lead-Bismuth Eutectic (LBE) of the MEGAPIE target. Twenty – mostly safety-relevant – radionuclides could be identified and quantified. Comparisons with theoretical predictions show acceptable agreement in most cases, but also considerable discrepancies for some selected radionuclides. Moreover, the scientists learned that noble elements like Gold, Silver, Mercury or Rhodium are homogeneously distributed in the bulk LBE, while others, sensitive to reduction/oxidation (Lanthanides, Iodine, Chlorine), tend to accumulate at exposed positions like vessel walls and free surfaces. These results will help to improve models and codes for predictions and, thus, will improve the safety of existing and future facilities.