FRM II

FRM II. The FRM II is a high-flux neutron source reactor and a central scientific facility operated by the Technische Universität München at the research campus in Garching bei München. It is the successor to the older FRM I reactor and serves as the core instrument of the Heinz Maier-Leibnitz Zentrum, providing intense neutron beams for a wide spectrum of fundamental and applied research. The reactor is renowned for its compact core design and its heavy water moderator, which enables exceptional neutron brightness for experiments in fields such as condensed matter physics, materials science, and structural biology.

Overview

The reactor functions as a user facility for the international scientific community, hosting hundreds of researchers annually from institutions like the Max Planck Society and various European Union member states. Its primary purpose is to generate neutrons for use in scattering experiments, which probe the structure and dynamics of materials at the atomic scale. The facility is integrated within the larger Heinz Maier-Leibnitz Zentrum, which also includes an accelerator-driven neutron source, the Munich Compact Accelerator-Driven Neutron Source. Management and scientific coordination are handled by the Technische Universität München in close cooperation with the Bundesministerium für Bildung und Forschung.

Technical specifications

The reactor achieves a thermal power of 20 MW using a single, compact fuel element containing highly enriched uranium-235. This element is cooled by light water and surrounded by a large tank of heavy water (D₂O) that acts as an excellent moderator and reflector, concentrating neutrons into beam tubes. Key parameters include a maximum unperturbed thermal neutron flux of approximately 8 × 10¹⁴ n/(cm²s), one of the highest in the world. The core is designed for a long operation cycle, typically lasting 60 full-power days. Numerous instruments, such as the high-resolution powder diffractometer SPODI and the small-angle scattering instrument KWS-2, are positioned at beam ports surrounding the reactor block.

Research applications

Neutron beams from the reactor are utilized for diverse investigations, including studying magnetic materials for spintronics, analyzing stress in industrial components like turbine blades, and determining protein structures for pharmaceutical development. The facility supports advanced techniques like neutron imaging, which can non-destructively examine the interior of objects such as archaeological artifacts or fuel cells. Research programs often involve collaborations with major facilities like the Institut Laue-Langevin in Grenoble and the European Spallation Source in Lund. Experiments have contributed to studies in quantum mechanics, superconductivity, and the development of new alloys.

History and development

Planning for a successor to the aging FRM I began in the 1980s, with formal approval granted by the Bayerische Staatsregierung in the early 1990s. Construction commenced in 1996 following a lengthy licensing process involving the Bundesministerium für Umwelt, Naturschutz und nukleare Sicherheit. The reactor achieved first criticality in March 2004, after overcoming significant political and public debate regarding the use of highly enriched uranium. The facility was officially named after physicist Heinz Maier-Leibnitz in 2005. Its development was a major project for the Technische Universität München and represented a significant investment by the Federal Republic of Germany and the Free State of Bavaria to maintain a leading position in neutron science.

Safety and operation

The reactor operates under a stringent safety concept approved by German authorities, including the Bayerisches Staatsministerium für Umwelt und Verbraucherschutz. Its design incorporates multiple passive safety systems, such as a large water storage pool for decay heat removal and containment structures. The single fuel element design minimizes nuclear inventory and simplifies handling and disposal. Operational safety is overseen by the Technische Universität München in compliance with regulations from the International Atomic Energy Agency. The reactor's spent fuel is managed under contracts with reprocessing facilities, and the site maintains comprehensive emergency plans coordinated with local agencies in Garching bei München.

Category:Research reactors Category:Neutron sources Category:Buildings and structures in Bavaria Category:Technische Universität München