Outline for a multi-cell nuclear thermionic fuel element that may be pretested with electric heat

A nuclear thermionic converter electrical generating system is proposed in which the nuclear fuel is clad in tungsten (W) and transmits heat to a tungsten emitter by radiation. The tungsten clad is a single unit, containing a continuous fuel stack with an unfueled section extending through one end of the reactor. The emitters are electrically insulated from the heat source; therefore, several converters may be connected by short leads to produce more voltage per fuel element and to reduce the power losses in the leads. A fast reactor design was chosen; consequently, tungsten may be used for the fuel cladding and the emitters without a significant reactivity penalty due to neutron capture by tungsten epithermal resonances. The ability to use all-tungsten emitters may permit high emitter temperatures. Calculations indicate that at an emitter temperature of 2150 K and current density of 10 A/cm², a 36 cm long thermionic fuel element (TFE) with 9 converters in series should produce 4500 W_e at 9.2 V and 15.7% efficiency. One major advantage of this approach, relative to typical multicell designs is that the system can be tested by electrical heaters in the fuel cavity before loading fuel