Abstract: This invention relates to a thermogenic swimming-pool type nuclear reactor adapted to produce hot water for use in a heating installation.The reactor comprises a generally cylindrical enclosure open at the top and filled with a cooling liquid. The enclosure is divided by a horizontal partition and the bottom zone below the partition contains the reactor core and at least one heat exchanger and at least one venturi. The cooling liquid is circulated between the outlet and inlet of the core through the heat exchanger and the venturi. At least one conduit extends through the partition so that its top end discharges into the upper zone and its bottom end discharges into an aperture formed in the wall of the venturi at its neck.