disclosed is a power plant having a nuclear reactor as a heat source and turbine assemblies comprising turbine , compressor and heat exchanger elements . the nuclear reactor is encased within a thermal barrier which is encased within a liner so as to form a free space between the thermal barrier and the liner . the free space is in communication with a cooling gas source , and the interior of the thermal barrier is in communication with a gas source . also disclosed is a method of cooling a nuclear reactor plant by passing a cooling gas into the free space between the liner and the barrier which is then passed to a recuperator after which it is passed within the thermal barrier surrounding the reactor .