[en] The Gas-Cooled Fast Breeder Reactor (GCFR) Demonstration Plant uses three helium loops to transfer heat from the reactor core to the steam generators. Helium flow in each loop is provided by a circulator driven by a 24,000 horsepower electric motor. Experimental verification of the designs of the circulator, circulator service system, main and pony motors, main and pony motor controllers, loop isolation valve instrumentation and control systems is needed to demonstrate that operational and safety requirements are met. A GCFR helium circulator test facility sized for full design conditions is proposed. The circulator will be mounted in a large vessel containing high pressure helium which will permit testing at the same power, speed, pressure, temperature and flow conditions present in the (demonstration) plant. The electric drive motor for the circulator will obtain its power from an electrical supply and distribution system in which electrical power will be taken from a local utility grid via a transformer