Live steam shut-off device for pressurized water reactors

In a pressurized water reactor having a safety vessel formed of a steel casing and a concrete wall surrounding and spaced from the steel casing, a double-wall steam discharge line extending from the steel casing through a hole formed in the concrete wall, the double-wall steam line having outer and inner walls defining an annular passage open inside the steel casing from returning steam escaping through a possible rupture in the inner wall back to the inside of the steel casing, and said line being closed outside the steel casing at a location spaced therefrom a distance at least equal to the distance between the steel casing and the concrete wall, a shut-off device disposed in said steam discharge line comprising exclusively one shut-off valve having a casing, said casing being directly connected to an end of said steam line outside said concrete wall, said casing being formed with steam inlet and outlet openings and with a further opening and means for closing said outlet opening, and at least one additional value having a casing formed with an inlet opening, said last-mentioned valve casing being directly connected by weldment to said first-mentioned valve casing so as to connect said inlet opening of said last-mentioned valve casing directly to said further openings.