Production to begin of innovative fuel for German research reactor

The 20 MWt FRM II, operating since 2005, is one of the most effective and modern sources of high-flux neutrons in the world. The reactor is not used to generate electricity, but to provide a neutron source for industrial and scientific use. Its neutrons are also used to produce medical radioisotopes and for the doping of high-purity silicon for the semiconductor industry, and the reactor has a facility for teletherapy of malignant tumours using fast neutrons.

TUM's FRM II research reactor (Image: B Ludewig / Framatome)

However, FRM II currently uses fuel enriched to over 95% uranium-235 to generate its dense neutron flux - and such high-enriched uranium (HEU) is seen as a nuclear proliferation risk. TUM has agreed with the German government and the Bavarian State - who finance the reactor - to work towards converting it to fuel with lower enrichments when a suitable fuel is available. This is also a condition of the reactor's operating licence, which was issued in 2003.

Monolithic U-Mo is the only fuel which can enable the reactor to perform as intended while using a low enrichment of less than 20% uranium-235, according to TUM. This is possible due to the high uranium density in the fuel, Framatome said.

In 2019, TUM contracted Framatome to develop the U-Mo foils manufacturing technique to support the existing technology of embedded foils in a cladding of aluminum. The first U-Mo foils were successfully manufactured in 2022 at Framatome's CERCA Research and Innovation Laboratory (CRIL) at Romans-sur-Isère in France. Inaugurated in 2019, CRIL is dedicated to developing uranium-based fuel for international research in physics and nuclear medicine.

CRIL, in cooperation with TUM, developed the key steps of the manufacturing process for a high-quality U-Mo fuel, including the manufacturing of small-scale prototypes, established a qualification procedure, and installed a pilot line in its research facility in Romans.

Irradiation of the first monolithic U-Mo fuel plate prototype is scheduled for late 2024.

"We have been working on this project since 2019 and we are proud to celebrate this important milestone with our client," said François Gauché, Vice-President of CERCA. "Our teams rose to the challenge of developing a high-tech fuel to meet the needs of research reactors and ensure their sustainability. We are now ready to take this to the next level and manufacture this innovative fuel."

"FRM II and Framatome have been working since 2019 to set up a European production line for monolithic U-Mo fuel," added Christian Pfleiderer, scientific director of the FRM II. "The hard work of our teams has paid off. This new fuel is the guarantee for a reliable and sustainable supply of neutrons for research and innovation."