NOVELTY - Alternative 1 module has power-generating assemblies in condensing zone of high-temperature heat pipe whose emitters and collectors are connected into electric circuit by electrode-to- electrode switching inside power-generating channel carrying cesium vapors and incorporating cathode and anode current leads.    USE - Direct heat-to-power conversion; spacecraft nuclear power sources.    ADVANTAGE - Enhanced service life and reliability of spacecraft nuclear power plant.    DETAILED DESCRIPTION - Power-generating element is built into neutral vessel of module accommodating high-temperature heat pipe. The latter has annular fuel element in evaporation zone and multielement power-generating channel with 2 to 20 series-connected power-generating elements to form electric circuit in condensing zone. At least one emitter of the latter is directly on condensing zone section and connected to cathode current lead which is reverse and coaxial relative to other ones electrically insulated from it by means of wet ceramic emitter insulation in cesium vapors. Inner surface of emitters is joined through wet ceramic emitter insulation and cathode current lead to outer surface of heat-pipe condensing zone. Evaporating zone of heat pipe may be located in gap between annular fuel element and high-temperature heat pipe which is in vacuum. Alternative 2 module has its high-temperature heat pipe built into electrically neutral vessel of module and gas-controlled. Condensing zone of heat pipe accommodates two multielement power-generating channels parallel-connected inside module vessel and with common interelectrode medium of cesium vapors, cathode and anode current leads, 2 to 10 power-generating elements in each power-generating channel. Emitters are in condensing zone of gas-controlled heat pipe. Evaporating zone of the latter may be located in gap between annular fuel element and heat pipe. Alternative 3 module has emitters of power-generating channel built into module vessel and on dry ceramic insulation connected to Filde tube.