A technical problem was identified in the HFR reactor, and it could not be launched on January 20 as had been planned, according to the National Centre for Nuclear Research (NCBJ) in Świerk, Poland. The Maria reactor took over production of the isotope on January 21.

The HFR reactor is one of the world's few molybdenum suppliers, the NCBJ said. The Maria reactor's quick response was possible because it has been ready since 2010 to perform irradiation of uranium targets for Mo-99 production.