Fuel design for high power density boiling water reactor

A fuel element design for a boiling water nuclear reactor having a central core for containing nuclear fuel in sealed tubes for undergoing fission reaction in the presence of circulating moderator-coolant, said fuel element comprising in combination:

• a moderator-coolant flow path for supplying said reactor with a moderator-coolant flow for producing in said reactor a continuous moderator-coolant flow path for the extraction of heat from said reactor;
• side by side fuel elements disposed in said reactor flow path, each element including,
• a central vertically disposed fuel rod, said fuel rod sealed at both ends and containing interior thereof fuel for undergoing fission reaction interior of said fuel element;
• a concentric channel individually surrounding each said fuel rod, said fuel channel open at the bottom of said core for receiving moderator coolant from the bottom of said channel and for discharging moderating coolant at the top of said channel and defining a coolant annulus therebetween;
• spacer means in said moderator coolant annulus extending from said channel to said fuel rod for maintaining said fuel rod in spaced apart relation relative to said channel;
• and,
• flow control means on said spacer means for imparting to moderator coolant passing upwardly between said channel and fuel rod in said modertor coolant annulus controlled fluid flow.

A fuel rod cladding to fuel channel fuel element design for a boiling water nuclear reactor having:

• a reactor pressure vessel;
• a core central of said pressure vessel for containing fuel in sealed tubes for undergoing fission reaction;
• moderator coolant for circulation through said pressure vessel for extracting the heat of fission from said sealed tubes;
• a defined flow path for circulation of said moderator coolant through said vessel including a first upwardly passing leg in said flow path from the bottom of said core to the top of said core in contact with said sealed tubes for undergoing fission reaction for the extraction of heat to said moderator coolant and a second upwardly passing leg in said flow path from the bottom of aid core to the top of said core away from said sealed tubes for undergoing fission;
• a power discharge path interior of said pressure vessel for the discharge of heat energy imparted at said core to said moderator coolant;
• and,
• a moderator-coolant inflow for resupplying said reactor with moderator coolant for producing in said vessel a continuous power generation cycle;
• the improvement to said core comprising in combination:
• a plurality of vertically upstanding fuel rods;
• a corresponding plurality of vertically upstanding channels, each said channel surrounding discretely a fuel rod to define a moderator path within said channel and around said fuel rod isolated from a core bypass volume exterior of said channel;
• a core plate at the bottom of said core, said core plate and embedded fuel support pieces providing a boundary between said plenum and said core;
• a fuel tie plate at the bottom of a collection of said fuel rods resting on fuel support pieces embedded within said core plate;
• means for connecting each said channel to receive moderator coolant at the bottom of said core defined in said core plate and said lower tie plate for passing moderator between said fuel rods and said channel to establish said first upwardly passing leg in said flow path from the bottom of said core to the top of said core in contact with said sealed tubes for undergoing fission reaction for the extraction of heat to said moderator coolant each said collection of fuel rods and said plenum;
• means for distributing coolant by apertures in said fuel tie plate to said fuel channels;
• and
• means for connecting the core bypass volume exterior of each said channel to said plenum defined by said core plate and said fuel tie plate to establish said second upwardly passing leg in said flow path from the bottom of said core to the top of said core away from said sealed tubes for undergoing fission whereby said discrete channels exterior of said fuel rods are surrounded by moderator coolant.

In a core for a boiling water nuclear reactor wherein said reactor includes:

• a reactor pressure vessel;
• a core central of said pressure vessel for containing fissionable fuel in sealed tubes for undergoing fission reaction;
• moderator coolant for circulation through said pressure vessel for extracting the heat of fission from said sealed tubes;
• a defined flow path for circulation of said moderator coolant through said vessel including a first upwardly passing leg in sad flow path from the bottom of said core to the top of said core in contact with said sealed tubes for undergoing fission reaction for the extraction of heat to said moderator coolant and a second upwardly passing leg in said flow path from the bottom of said core to the top of said core away from said sealed tubes for undergoing fission;
• a power discharge path interior of said pressure vessel for the discharge of energy imparted at said core to said moderator coolant;
• and,
• a moderator-coolant inflow for resupplying said reactor with moderator coolant for producing in said vessel a continuous power generation cycle;
• the improvement to said core comprising:
• a plurality of vertically upstanding fuel rods;
• a corresponding plurality of vertically upstanding channels, each said channel surrounding discretely a fuel rod;
• spacer means for connecting said fuel rods and channels into a rigid unitary structure;
• means for binding groups of said fuel channels with said spacers therein for defining unitary fuel assemblies containing a plurality of fuel rods and a corresponding plurality of channels;
• means for connecting each said channel to receive moderator coolant at the bottom of said core;
• means for connecting each said channel to discharge said moderator coolant at the top of said core whereby said first upwardly passing leg in said flow path from the bottom of said core to the top of said core in contact with said sealed tubes for undergoing fission reaction for the extraction of heat to said moderator coolant;
• and,
• means for connecting the interstital volume defined by said channels outside of said channels to said moderator coolant flow path whereby a second upwardly passing leg in said flow path from the bottom of said core to the top of said core away from said sealed tubes for undergoing fission.