Reactor fuel hold-down assemblies

Abstract

Abstract 1,018,481. Reactors; fuel elements. BABCOCK & WILCOX CO. Aug. 22, 1962 [Aug. 23, 1961], No. 32222/62. Heading G6C. A nuclear reactor has fuel elements formed of clusters of cylindrical fuel cans, some of the elements being provided with retaining means to prevent their displacement by coolant flow, the retained fuel elements themselves retaining adjacent fuel elements not possessing said retaining means. The retaining fuel elements, Fig. 5, include grapples 104 which engage lugs on the under face of the lower grid plate 60 (Fig. 1), and can be released by means of a rod 108 actuated from above the fuel element to withdraw the locking wedge 112. Adjacent fuel elements are retained by springs 126 mounted on the top casting 88 of the fuel element, and also by lugs mounted at the lower ends of said adjacent fuel elements which engage beneath the shoulder formed by the cylindrical body portion 94 of the retaining fuel element. Dowels are provided for lateral constraint. The reactor is adapted to operate with spectral shift control as described in Specification 894,902, and uses a combined moderator and coolant in the form of a mixture of light and heavy water. The pressure vessel 54, Fig. 1, is supported on a base 200 during construction, but on completion its weight is supported by a cylindrical biological shield 196 which is waterfilled. The moderator-coolant enters through a pipe 17 and passes downward, cooling the thermal shields 140, 150, 152, into a lower plenum chamber 62, from which it flows up through the core to an upper plenum chamber 66 and out of the reactor through a pipe 18. The upper plenum chamber includes a filler casting 178 to reduce the required volume of moderatorcoolant. Top mounted control rods 12 are used for emergency shut-down, and a portion of the coolant is allowed to leak through the controlrod guide tubes 158 into the uppermost part of the pressure vessel. The lattice (Fig. 2, not shown), is arranged so that each retaining fuel element is surrounded by four retained fuel elements having within them cruciform control rod passages. Fuel elements (Fig. 5).-The individual fuel cans are retained in each element by top and bottom grip plates 78, 80 and an intermediate grid 82. The fuel cans 84 at the corners and 86 at the side mid-points are made of thicker section tubing and constitute structural members for connecting the top and bottom fuel element grid plates. Similar tubes are used in the same manner in the control rod-passage-containing fuel elements. The structural cans are threaded for retention in the upper grid plate.

Inventors

• 👤 Felix S Jabsen

Bibliographic Details