Several distinct reactor strategies are proposed within the context of the IP Eurotrans framework programme for the transmutation of nuclear waste. A pool type reactor filled with liquid heavy metal and containing a subcritical core is one of the promising designs. Additional neutrons required for the nuclear reaction are generated by a spallation reaction inside the core. A high power proton beam is guided through a vacuum tube from an accelerator into the liquid heavy metal pool i.e. into the reactor core. At the point where the beam hits the metal surface special construction effort is indispensable to handle the high heat production.
A specific target design is used to ensure a high fluid velocity and a stable surface at the beam entry. This design employs a concentric vertical feeder establishing a free conical surface with velocity up to 2.5 m/s ensuring stable surface flow and appropriate heat removal. The proposed target geometry has been constructed using underlying rules developed by the MYRRHA design group for the free surface target in the MYRRHA research reactor.
A full scale model of this design using lead bismuth eutectic (LBE) has been set up and experimentally investigated at the of the Karlsruhe Institute of Technology (KIT). Measurements taken by high speed digital imaging visualize both conical inner and outer jet free surface. They show a stable surface in a wide range of operating conditions starting from 35% of the nominal flow rate and agree well with numerical investigations using commercial CFD code Star-CD and Star-CCM+. Previous concerns related to splashing or cavitation during the start-up or shut-down procedure proofed unjustified.