Patent ID: 9721681
Date: 2017-08-01
CPC Classifications: G21C,Y02E

Claim:
1. An apparatus comprising: a cylindrical pressure vessel including an upper vessel section, a lower vessel section, and a mid-flange, the upper vessel section and the lower vessel section being joined by the mid-flange; a cylindrical central riser disposed concentrically inside the cylindrical pressure vessel and including an upper riser section disposed in the upper vessel section and a lower riser section disposed in the lower vessel section; a reactor core comprising fissile material disposed inside the cylindrical pressure vessel in the lower vessel section; control rod drive mechanism (CRDM) units controlling control rod insertion actively into the reactor core, the CRDM units being disposed inside the cylindrical pressure vessel above the reactor core and in the lower vessel section with no vertical overlap between the upper vessel section and the CRDM units; a riser transition section disposed between the upper riser section and the lower riser section, the riser transition section being connected to the mid-flange by gussets having first ends welded to the mid-flange and second ends welded to the riser transition section, the gussets being angled downward such that the riser transition section is disposed below the mid-flange; a CRDM support plate disposed below the riser transition section and supporting the CRDM units; and tie rods suspending the CRDM support plate from the mid-flange.