Nuclear Energy and Safety Research Division

The Hot Laboratory division (AHL) within PSI’s Nuclear Energy and Safety (NES) division continually upgrades and advances its analytical infrastructure to provide cutting-edge scientific service to PSI’s researchers and industrial customers. A new, fully automatable and highly flexible Ion Chromatograph (IC) furthers AHL’s efforts in sample miniaturization and extends the spectrum of destructive analytical capabilities to element and speciation specific analyses. With the new IC and its modern ICP-MS (Inductively Coupled Plasma Mass Spectrometry) facilities, AHL offers innovative scientific options for nuclear and general research. Moreover, speciation analyses by IC-ICP-MS for polyvalent inorganic water pollutants such as Cr or As and the acquisition of a new ICP-OES system (Inductively Coupled Plasma Optical Emission Spectrometry) enable future autonomy in wastewater management.

Geological waste disposal, cement clay interaction

• A considerable reduction of HTO and ³⁶Cl⁻ was observed after 6 years interaction.
• The chloride flux showed a much stronger reduction compared to HTO.
• For HTO the relation between the D_e and the porosity in the clay part can be described using Archie's law.
• No complete clogging of the porosity was observed after 6 years interaction.

Several stress corrosion cracking (SCC) incidents recently occurred in Alloy 182 - reactor pressure vessel (RPV) dissimilar metal welds in boiling water reactors (BWR). These SCC cracks tend to grow towards the RPV due to weld microstructure and residual stress profiles and might grow into the RPV. They thus represent a serious potential safety concern. PSI has evaluated under which conditions such cracks could grow into the RPV and also developed SCC crack growth disposition curves for the RPV steels that can be used for safety assessments of such cracks. With these curves that were recently accepted as a new Code Case N-896 in the ASME Boiler and Pressure Vessel Code, sufficient safety margins could be demonstrated for such crack configurations with the current inspection intervals of the periodic in-service inspection.

All matter in the universe is made of atoms and all atoms are made of particles. Spontaneous changes within atoms as well as collisions between atoms and surrounding particles are nuclear reaction processes guided by nuclear physics laws. To simulate these processes using computer models, probabilities for the various involved nuclear reactions are required. This is precisely the role of nuclear data: supply the computational models with evaluated quantities representing these nuclear reaction probabilities. Through this, nuclear data can effectively be seen as the fundamental link between nature and any computer simulation involving nuclear reactions. It is thus of primary importance to continuously improve knowledge on nuclear data. In that context, researchers at the laboratory for reactor physics and thermal-hydraulics have recently focused on the development and application of Bayesian frameworks combining both differential and integral experiments for the improvement of nuclear data. By considering the different experiments together, the aim is to achieve enhancements of the nuclear data evaluations while preserving the basic nuclear physics sum rules.