Bridging Europe’s neutron gap

24 April 2020

The recent closure of reactors means making the most of existing facilities while preparing accelerator-based sources, says Helmut Schober.

The Institut Laue-Langevin

In increasing its focus towards averting environmental disaster and maintaining economic competitiveness, both the European Union and national governments are looking towards green technologies, such as materials for sustainable energy production and storage. Such ambitions rely on our ability to innovate – powered by Europe’s highly developed academic network and research infrastructures.

Neutron science holds enormous potential at every stage of innovation

Europe is home to world-leading neutron facilities that each year are used by more than 5000 researchers across all fields of science. Studies range from the dynamics of lithium-ion batteries, to developing medicines against viral diseases, in addition to fundamental studies such as measurements of the neutron electric-dipole moment. Neutron science holds enormous potential at every stage of innovation, from basic research through to commercialisation, with at least 50% of publications globally attributed to European researchers. Yet, just as the demand for neutron science is growing, access to facilities is being challenged.

Helmut Schober

Three of Europe’s neutron facilities closed in 2019: BER II in Berlin; Orphée in Paris; and JEEP II outside Oslo. The rationale is specific to each case. There are lifespan considerations due to financial resources, but also political considerations when it comes to nuclear installations. The potentially negative consequences of these closures must be carefully managed to ensure expertise is maintained and communities are not left stranded. This constitutes a real challenge for the remaining facilities. Sharing the load via strategic collaboration is indispensable, and is the motivation behind the recently created League of advanced European Neutron Sources (LENS).

We must also ensure that the remaining facilities – which include the FRM II in Munich, the Institut Laue-Langevin (ILL) in France, ISIS in the UK and the SINQ facility in Switzerland – are fully exploited. These facilities have been upgraded in recent years, but their long-term viability must be secured. This is not to be underestimated. For example, 20% of the ILL’s budget relies on the contributions of 10 scientific members that must be renegotiated every five years. The rest is provided by the ILL’s three associate countries (France, Germany and the UK). The loss of one of its major scientific members, even only partially, would severely threaten the ILL’s upgrade capacity.

Accelerator sources

The European Spallation Source (ESS) under construction in Sweden, which was conceived more than 20 years ago, must become a fully operating neutron facility at the earliest possible date. This was initially foreseen for 2019, now scheduled for 2023. Europe must ask itself why building large scientific facilities such as ESS, or FAIR in Germany, takes so long, despite significant strategic planning (e.g. via ESFRI) and sophisticated project management. After all, neutron-science pioneers built the original ILL in just over four years, though admittedly at a time of less regulatory pressure. We must regain that agility. The Chinese Spallation Neutron Source has just reached its design goal of 100 kW, and the Spallation Neutron Source in Oak Ridge, Tennessee, is actively pursuing plans for a second target station.

The value of neutron science will be judged on its contribution to solving society’s problems

We therefore need to look to next-generation sources such as Compact Accelerator driven Neutron Sources (CANS). Contrary to spallation sources that produce neutrons by bombarding heavy nuclei with high-energy protons, CANS rely on nuclear processes that can be triggered by proton bombardment in the 5 to 50 MeV range. While these processes are less efficient than spallation, they allow for a more compact target and moderator design. Examples of this scheme are SONATE, currently under development at CEA-Saclay and the High Brilliance Source being pursued at Jülich. CANS must now be brought to maturity, requiring carefully planned business models to identify how they can best reinforce the ecosystem of neutron science.

It is also important to begin strategic discussions that aim beyond 2030, including the need for powerful new national sources that will complement the ESS. Continuous (reactor) neutron sources must be part of this because many applications, such as the production of neutron-rich isotopes for medical purposes, require the highest time-averaged neutron flux. Such a strategic evaluation is currently under way in the US, and Europe should soon follow suit.

Despite last year’s reactor closures, Europe is well prepared for the next decade thanks to the continuous modernisation of existing sources and investment in the ESS. The value of neutron science will be judged on its contribution to solving society’s problems, and I am convinced that European researchers will rise to the challenge and carve a route to a greener future through world-leading neutron science.

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