Patent Number: 055442102
Section: summary

TECHNICAL FIELD This invention relates to a pressure vessel apparatus for containing fluid under high temperature and pressure. The apparatus disclosed herein has particular application for use as a nuclear reactor vessel and incorporates safety features. BACKGROUND ART My U.S. Pat. No. 5,217,681, issued Jun. 8, 1993, discloses a prestressed pressure vessel safety enclosure 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. 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. Upper and lower ring girders, connected to each other by tension tendon members, in conjunction with upper and lower jacket bearing plates and skirts are used to apply force to the respective upper and lower jackets for moving the jackets toward or away from each other. My U.S. Pat. No. 5,465,280, issued Nov. 7, 1995, discloses a nuclear reactor vessel employing bellows in the construction thereof which operate as fluid barriers, confine lead material filler, and allow for relative movement of structural components of the apparatus in a controlled manner. Additionally, the apparatus disclosed in U.S. Pat. No. 5,465,280 incorporates connector tendons of a specialized construction, incorporating two sets of tendons, one of which is prestressed almost to yield point, and the other of which is prestressed to a lesser degree. U.S. Pat. No. 5,204,054, issued Apr. 20, 1993, discloses a nuclear reactor system pressure vessel comprising a steel inner liner part, an intermediate insulative layer part and an outer concrete encasing part pre-stressed by cable tendons located inside the casing. Use of the pre-stressed construction allows for construction of pressure vessels of larger size. The outer vessel part can be of a cast single piece structure or it can be an integrated concrete segment assembled structure embodying pre-stressing cable tendons arranged in various orientations to effect pre-stressing. Further, the major portion of the pressure vessel can be disposed below grade to lessen the presence of vessel structure in a nuclear system containment. Cooling passages are provided in the pressure vessel to carry off reactor decay heat as well as heat in the concrete outer vessel part. Applicant is aware of a publication entitled Recent Investigations and Tests With the BBR Winding System for Circumferential Prestressing of Concrete Vessels and Containments authored by K. Schutt and F. E. Speck, published in 1993 by Elsevier Science Publishers B. V. in SMiRT-12 Transactions. The publication discloses the use of elongated reinforcement elements in the form of continuously wound prestressing wire strands or bands which are wound about the periphery of large prestressed concrete pressure vessels for nuclear power stations. The prestressed strands are applied in layers spirally wound over the whole width of channels formed at the outer periphery of the concrete pressure vessel, requiring much less space and making them easier to install and inspect compared to cable tendons. The following publications and United States patents are also believed to be representative of the state of the prior art: U.S. Pat. No. 3,433,382, issued Mar. 18, 1969, U.S. Pat. No. 3,775,251, issued Nov. 27, 1973, U.S. Pat. No. 4,192,718, issued Mar. 11, 1980, U.S. Pat. No. 3,445,971, issued May 27, 1969, U.S. Pat. No. 3,512,675, issued May 19, 1970, U.S. Pat. No. 3,653,434, issued Apr. 4, 1972, U.S. Pat. No. 3,606,715, issued Sep. 21, 1971, U.S. Pat. No. 5,229,067, issued Jul. 20, 1993, U.S. Pat. No. 5,047,201, issued Sep. 10, 1991, U.S. Pat. No. 4,859,402, issued Aug. 22, 1989, U.S. Pat. No. 4,650,642, issued Mar. 17, 1987, and U.S. Pat. No. 4,032,397, issued Jun. 28, 1977. Applicant has authored a paper entitled Prestressed Safety Enclosure (PSE) with Metallic Cushion for New or Existing Reactor Pressure Vessels, published in SmiRT 11 Transactions Vol. SD2 (August, 1991). DISCLOSURE OF INVENTION The present invention relates to pressure vessel apparatus defining a pressure vessel interior for containing fluid under pressure. The invention has particular application to nuclear reactor system pressure vessels, especially large size vessels. Existing pressure vessel designs have two major limitations which tend to restrict the overall safety and capacity of the vessel: 1. Diameter and pressure capacity of the vessel head is limited by the number, size and capacity of the studs tying the head to the vessel body. This limitation in turn limits the number and spacing of the various penetrations which can be located there. PA1 2. Diameter and pressure capacity of the vessel main body and top and bottom is limited by the maximum vessel shell thickness as dictated by manufacturing or fabrication technologies. For nuclear reactor vessels this limitation imposes upper limits on core size and aspect ratio and makes any system integrated design difficult, restricting the space available for steam separation or heat exchangers, spent fuel storage, and a large water reservoir. The invention described below overcomes these limitations. The pressure vessel of the present invention incorporates a number of features contributing to the structural stability and safety of such pressure vessels. In particular, such features contribute to the containment of radioactive or toxic materials within the pressure vessel in the event of generation of high pressures therein, for example due to a core melt event, steam explosions, and/or hydrogen explosions. The vessel is always (except during extreme accident) in a state of three dimensional compression. Relative movement between certain structural components thereof due to temporary high pressure conditions within the vessel interior is permitted to avoid structural failure and emission of dangerous materials from the pressure vessel. The pressure vessel apparatus of the present invention includes a vessel main body having a bottom and an outer peripheral wall extending upwardly from the bottom and defining a vessel main body top opening. A vessel top body having an outer peripheral wall is positioned on the top opening of the outer peripheral wall of the vessel main body to form a joint therebetween. The vessel top body defines a vessel top body bottom opening communicating with the vessel main body top opening, and the vessel top body defines a top opening. A vessel head is positioned on the vessel top body and covers the top opening. First securement means secures the vessel top body to the vessel main body. Second securement means secures the vessel head to the vessel top body. The second securement means comprises a plurality of double-ended, elongated tendons under tension extending between and secured to the vessel top body and the vessel head. The outer peripheral walls of the vessel main body and the vessel top body define a plurality of spaced throughbores extending vertically alongside and spaced from the pressure vessel interior. The first securement means includes a plurality of double-ended tendons under tension extending through the throughbores and secured to the vessel main body and the vessel top body. The tendons secured to the vessel main body and the vessel top body permit movement of the vessel top body away from the vessel main body due to a pressure surge or explosion caused by core melt or other accident within the pressure vessel interior before the tendons secured to the vessel top body and the vessel head permit movement of the vessel head away from the vessel top body due to the pressure surge within the pressure vessel interior. Other features, advantages, and objects of the present invention will become apparent with reference to the following description and accompanying drawings.