LRS Research Programs

Nuclear Safety Phenomenology (STARS)

The STARS project centers around the in-depth analysis of the dynamic behavior of Light-Water Reactors (LWRS) with focus on Switzerland’s 5 operating NPPs (neutronics coupled to thermal-hydraulics and fuel behavior).

As such, it provides the key framework for safety-related analytical research in the laboratory. The generic mission of the research is to maintain and further develop a comprehensive state-of-the-art, best-estimate, safety analysis methodology for reactor states ranging from normal operation to beyond design conditions (before core melt) as well as for out-of-core applications, and to integrate the necessary tools into a consistent system of simulation codes. Particular emphasis is currently being given to aspects requiring greater inter-disciplinarily of treatment as well as more rigorous strategies to validate and quantify the reliability of the simulation results. For this reason, significant efforts are being invested in the development and application of novel multi-physics multi-scale computational schemes as well as uncertainty quantification and sensitivity analysis methodologies

On the basis of its research activities, a specific mission of STARS is to effectively act as a technical safety organization unit for LWR safety analysis and provides scientific support to national (as well as international) partners, including primarily the Swiss Federal Nuclear Safety Inspectorate (ENSI) for safety related support and the Swiss utilities or special studies for operation and optimization related support. Finally, STARS also aims at acting as an education center with the integration of trainees, master, PhD and post-doctoral projects as part of its research and with contribution to teaching, primarily within the framework of the Swiss EFPL/ETHZ nuclear engineering master program.


Generation-IV nuclear reactors with a fast neutron spectrum (FAST)

FAST is an R&D project on-going in LRS since 2002 and the current goals are
  1. to study neutronics, thermal hydraulics and fuel behaviour of advanced fast-spectrum nuclear reactors using modern computational tools (TRACE/PARCS/FRED, Eranos/EQL3D, Serpent 2, OpenFOAM);
  2. to evaluate safety of fast reactors considered for construction in Europe (in particular, ASTRID SFR);
  3. to analyse innovative design solutions for Generation-IV Molten Salt Reactor;
  4. to represent Switzerland internationally (in GIF, IAEA, OECD, EURATOM);
  5. to educate young researchers and students (in particular, via the ETHZ/EPFL Master of Science in Nuclear Engineering and EPFL PhD programs).
The cross-cutting topics are equilibrium fuel cycle, transient analysis, and validation of the codes, using available experimental data.


Experimental Reactor Physics (ERP)

During its lifetime (1968-2011), the versatile critical facility PROTEUS in LRS was used to investigate a wide range of advanced reactor concepts - gas-cooled fast reactor (GCFR), tight pitch high-converting light water reactor (HCLWR), high temperature reactor (HTR) - and to support the current LWR technology by providing precise experimental data for code validation.

Modern LWRs were studied as a joint program between PSI and the Swiss nuclear utilities since 2000’s. The experiments particularly addressed the heterogeneities of real advanced BWR fuel assembly designs through detailed three dimensional power mappings, and investigated highly burnt fuel rod samples (up to 120 GWd/t) in a variety of PWR-representative neutron spectra. The burnt fuel samples isotopic compositions were measured in the PSI Hot-Laboratory, which allowed validating depletion calculations and characterizing precisely their burnup credit effects and neutron source strengths.

Physics of highly enriched spent fuel in today’s nuclear power plants, and particularly the characterization of the strong flux and spectrum gradients at the interface between newly loaded highly enriched fresh fuel assembly and highly burnt fuel assembly, was the focus of the next experimental program co-funded with the Swiss utilities. A large bundle of spent fuel was to be inserted in PROTEUS requiring a refurbishment of the facility. Unfortunately, for strategic reasons the refurbishment of PROTEUS has been cancelled in May 2011 and the facility is currently decommissioned.

The activities of the Experimental Reactor Physics group are now mainly reoriented towards the CROCUS zero-power reactor at the Ecole Polytechnique Fédérale de Lausanne (EPFL). New experiments related to safety, measurement technique and detector development are currently designed. In addition, the group continues re-interpreting the vast experimental database produced in PROTEUS to validate code and nuclear data libraries and, under the umbrella of international expert groups, safeguards them for future generations of nuclear engineers.