Patent ID: 7873138

Claim:
A reactor vessel comprising: a neutron reflector; a lower core plate; a core vessel, the core vessel including a flange portion extending in a direction towards the neutron reflector; and a neutron reflector bolt fastening structure, the neutron reflector bolt fastening structure including: a plurality of divided stage portions composing said neutron reflector which is situated in said core vessel in said reactor vessel; a plurality of tie rods that fix said neutron reflector to said core vessel; and a plurality of bolts that fasten solely a lowermost stage portion of said plurality of stage portions of said neutron reflector to said core vessel, wherein said lowermost stage portion of said neutron reflector includes a plurality of flange portions extending in a direction towards the core vessel and positioned above the lower core plate, and wherein the plurality of bolts are configured to extend through each of the plurality of flange portions of the lowermost stage portion and the lower core plate, and the plurality of bolts extend partially into the flange portion of the core vessel positioned below the lower core plate, to secure the lowermost stage portion of the neutron reflector to the core vessel.