Abstract: A prestressed pressure vessel safety enclosure is used as a pressure safety enclosure for a nuclear reactor pressure vessel or other primary system vessel containing fluid or gaseous material under high pressure, such as, steam generators, pressurizers and pumps. The special pressure vessel enclosure comprises a first pressure vessel containment assembly surrounding the primary pressure vessel. A pair of first upper and lower pressure vessel jackets are adapted to enclose and be spaced apart, respectively, from the upper and lower portions of the first pressure vessel containment assembly with the rims of the jackets adapted to be slidable and sealed with respect to the first pressure vessel containment assembly. The spaces between the jackets and pressure vessel containment assembly are filled with a high boiling point, low melting point metal.

Abstract: A multiple shell pressure vessel is fabricated in modular sections comprising a top head module, a nozzle course module and a bottom shell module, each module utilizing telescoping shells with filled interspaces, each shell being removable for inspection and repair with all modular sections and shells being held in compression by a pair of upper and lower single or multilayer tendon skirts held in place by a number of tension members in combination with hydraulic or mechanical jacks or rams. Both tendons and rams are located outside the pressure vessel. Included is a method of arranging the shell flanges and shell radial supports to reduce or eliminate torsional forces on the flanges and flange seals. A leak detection system monitors for leaks in all shells. A method of adjusting shell stresses during operation uses pumps to adjust the pressure of the filler material in the interspaces between shells.