Direct cycle steam cooled reactor

A compact and economical nuclear superheat reactor suitable for power plants and ships is provided. The reactor core contains a plurality of double pipes, each comprising an upcomer surrounded coaxially by a downcomer. Steam superheated in the core is introduced into a first header disposed thereabove. Part of the superheated steam is fed to an external turbine via an outlet provided on a pressure shell, with the remaining part by-passed and ejected, through a plurality of ejecting tubes, into light water serving as a moderator and reflector and surrounding the reactor core thus producing saturated steam when the load of the turbine is temporarily decreased. The saturated steam is pumped into the first header in order to be superheated in the core. The present reactor is advantageous in that the supply of superheated steam to the turbine is quickly adjusted in response to changes in the turbine load. Reactor core failures are reduced since the water is not in direct contact with fuel elements. The temperature of the superheated steam does not abruptly elevate even when the load of the turbine is reduced since the excessively superheated steam is used to generate the saturated steam. (T. Yamaguchi)