Abstract: A method of storing high level radioactive waste, and specifically a method of adjusting or controlling the temperature of ventilation air flowing through a storage cavity of a ventilated system. The method includes positioning a metal canister containing high level radioactive waste in a storage cavity of the ventilated system. The ventilated system includes a cask body, a cask lid, a plurality of inlet ducts, and at least one outlet duct so that ventilation air can flow from atmosphere into the storage cavity where it is heated and then back out to the atmosphere. The method includes progressively reducing a cross-sectional area of one or more of the inlet ducts and/or the outlet duct over time so that a rate at which the ventilation air is heated within the storage cavity is maintained above a predetermined threshold to mitigate the risk of stress corrosion cracking in the metal canister.

Abstract: A container and system for handling damaged nuclear fuel, and a method of making the same. In one embodiment, the invention is a damaged fuel container having a specially designed top cap that can be detachably coupled to the elongated tubular wall by simply translating the top cap into proper position within the elongated tubular wall, wherein biased locking elements automatically lock the top cap to the elongated tubular wall. In another embodiment, the vent screens of the damaged fuel container are integrally formed rather than being separate components. In still other embodiments, the lower vent screens are arranged on an upstanding portion of the damaged fuel container. In an even further embodiment, the elongated tubular wall is formed by an extrusion process.

Abstract: A nuclear reactor cooling system with passive cooling capabilities operable during a reactor shutdown event without available electric power. In one embodiment, the system includes a reactor vessel with nuclear fuel core and a steam generator fluidly coupled thereto. Primary coolant circulates in a flow loop between the reactor vessel and steam generator to heat secondary coolant in the steam generator producing steam. The steam flows to a heat exchanger containing an inventory of cooling water in which a submerged tube bundle is immersed. The steam is condensed in the heat exchanger and returned to the steam generator forming a closed flow loop in which the secondary coolant flow is driven by natural gravity via changes in density from the heating and cooling cycles. In other embodiments, the cooling system is configured to extract and cool the primary coolant directly using the submerged tube bundle heat exchanger.

Abstract: A canister for storing spent nuclear fuel includes an elongated shell, baseplate enclosing the bottom end of the shell, and removable top lid bolted to the shell. The shell may have a dual thickness comprising a lower portion with first thickness and upper portion with greater second thickness by comparison. The upper portion is formed by an annular boss defining a fastening portion of the shell including plural threaded bores for engaging the lid bolting. The fastening portion may protrude radially outwards or inwards in different embodiments. The lid has a mounting flange receiving the bolts and is seated on the top end of shell. The mounting flange does not protrude radially beyond the outer surface of the fastener portion to minimize the diameter of the canister for placement inside an outer radiation shielded overpack or cask for transport/storage. The shell may optionally include cooling fins.

Abstract: A component cooling water system for a nuclear power plant. In one embodiment, the system includes an inner containment vessel housing a nuclear reactor and an outer containment enclosure structure. An annular water reservoir is formed between the containment vessel and containment enclosure structure which provides a heat sink for dissipating thermal energy. A shell-less heat exchanger is provided having an exposed tube bundle immersed in water held within the annular water reservoir. Component cooling water from the plant flows through the tube bundle and is cooled by transferring heat to the annular water reservoir. In one non-limiting embodiment, the tube bundle may be U-shaped.

Abstract: A nuclear steam supply system includes an elongated reactor vessel having an internal cavity with a central axis, a reactor core having nuclear fuel disposed within the internal cavity, and a steam generating vessel having at least one heat exchanger section, the steam generating vessel being fluidicly coupled to the reactor vessel. The reactor vessel includes a shell having an upper flange portion and a head having a head flange portion. The upper flange portion is coupled to the head flange portion, wherein the upper flange portion extends into the internal cavity, and the head flange portion extends outward from the internal cavity. The flanges have a space saving design which are configured to minimize outward extension from the cavity while still providing desired leak protection at the interface between the shell and the head.

Abstract: A nuclear reactor cooling system with passive cooling capabilities operable during a loss-of-coolant accident (LOCA) without available electric power. The system includes a reactor vessel with nuclear fuel core located in a reactor well. An in-containment water storage tank is fluidly coupled to the reactor well and holds an inventory of cooling water. During a LOCA event, the tank floods the reactor well with water. Eventually, the water heated by decay heat from the reactor vaporizes producing steam. The steam flows to an in-containment heat exchanger and condenses. The condensate is returned to the reactor well in a closed flow loop system in which flow may circulate solely via gravity from changes in phase and density of the water. In one embodiment, the heat exchanger may be an array of heat dissipater ducts mounted on the wall of the inner containment vessel surrounded by a heat sink.

Abstract: A control rod drive system (CRDS) for use in a nuclear reactor. In one embodiment, the system generally includes a drive rod mechanically coupled to a control rod drive mechanism (CRDM) operable to linearly raise and lower the drive rod along a vertical axis, a rod cluster control assembly (RCCA) comprising a plurality of control rods insertable into a nuclear fuel core, and a drive rod extension (DRE) releasably coupled at opposing ends to the drive rod and RCCA. The CRDM includes an electromagnet which operates to couple the CRDM to DRE. In the event of a power loss or SCRAM, the CRDM may be configured to remotely uncouple the RCCA from the DRE without releasing or dropping the drive rod which remains engaged with the CRDM and in position.

Abstract: A fuel rack for nuclear fuel assemblies includes a base plate and an array of cells for holding fuel assemblies. The array of cells includes: a plurality of first slotted plates slidably interlocked with one another to form a top portion of the array of cells, the plurality of first slotted plates formed of a first material; a plurality of second slotted plates slidably interlocked with one another to form a middle portion of the array of cells, the plurality of second slotted plates formed of a second material, the first and second materials being metallurgically incompatible; and a plurality of third slotted plates slidably interlocked with one another to form a bottom portion of the array of cells, the plurality of third slotted plates formed of the first material and connected to a top surface of the base plate.

Abstract: A nuclear reactor in one embodiment includes a cylindrical body having an internal cavity, a nuclear fuel core, and a shroud disposed in the cavity. The shroud comprises an inner shell, an outer shell, and a plurality of intermediate shells disposed between the inner and outer shells. Pluralities of annular cavities are formed between the inner and outer shells which are filled with primary coolant such as demineralized water. The coolant-filled annular cavities may be sealed at the top and bottom and provide an insulating effect to the shroud. In one embodiment, the shroud may comprise a plurality of vertically-stacked self-supported shroud segments which are coupled together.

Abstract: Described herein are compositions for use in the brazing of metal substrates. Methods of making and using these compositions are also described herein.

Abstract: A system and method for storing multiple canisters containing high level waste below grade that afford adequate ventilation of the spent fuel storage cavity. In one aspect, the invention is a ventilated system for storing high level waste emitting heat, the system comprising: an air-intake shell forming an air-intake cavity; a plurality of storage shells, each storage shell forming a storage cavity; a lid positioned atop each of the storage shells; an outlet vent forming a passageway between an ambient environment and a top portion of each of the storage cavities; and a network of pipes forming her sealed passageways between a bottom portion of the air-intake cavity and at least two different openings at a bottom portion of each of the storage cavities such that blockage of a first one of the openings does not prohibit air from flowing from the air-intake cavity into the storage cavity via a second one of the openings.

Abstract: A ventilated apparatus for storing and/or transporting high level radioactive waste. In one aspect, the invention is a ventilated apparatus comprising: an overpack body having an inner surface forming a cavity about a longitudinal axis. A bottom portion of the overpack body is formed by a plurality of segments. Each of the segments extends from a first end wall having a projection to a second end wall having a channel. The segments circumferentially surround a longitudinal axis and are arranged in an intermeshing and spaced-apart configuration such that the projections of the first end walls of the segments project into the channels of the second end walls of adjacent ones of the segments, thereby forming inlet ducts between adjacent ones of the segments. The inlet ducts form air inlet passageways from the external atmosphere to a bottom portion of the cavity.

Abstract: A nuclear steam supply system utilizing gravity-driven natural circulation for primary coolant flow through a fluidly interconnected reactor vessel and a steam generating vessel. In one embodiment, the steam generating vessel includes a plurality of vertically stacked heat exchangers operable to convert a secondary coolant from a saturated liquid to superheated steam by utilizing heat gained by the primary coolant from a nuclear fuel core in the reactor vessel. The secondary coolant may be working fluid associated with a Rankine power cycle turbine-generator set in some embodiments. The steam generating vessel and reactor vessel may each be comprised of vertically elongated shells, which in one embodiment are arranged in lateral adjacent relationship. In one embodiment, the reactor vessel and steam generating vessel are physically discrete self-supporting structures which may be physically located in the same containment vessel.

Abstract: A passively cooled storage module for spent nuclear fuel includes an elongated body including a top end, bottom end, sidewall, baseplate, detachable lid, and cavity for holding a fuel canister containing heat-emitting spent nuclear fuel assemblies. Cooling air inlet ducts spaced draw ambient cooling air radially inwards into a lower portion of the cavity. The air flows upwards in the cavity along the canister and is discharged from the top end of the module to atmosphere via natural circulation. The air inlet ducts may have a multi-angled and recurving configuration comprising one or more obliquely angled sections in one embodiment. The exterior inlet end openings of the inlet ducts are arranged at a higher elevation than the interior outlet end openings to prevent the ingress of standing and flood-related waters. The ducts and lid include radiation shielding features.

Abstract: A nuclear reactor in one embodiment includes a cylindrical body having an internal cavity, a nuclear fuel core, and a shroud disposed in the cavity. The shroud comprises an inner shell, an outer shell, and a plurality of intermediate shells disposed between the inner and outer shells. Pluralities of annular cavities are formed between the inner and outer shells which are filled with primary coolant such as demineralized water. The coolant-filled annular cavities may be sealed at the top and bottom and provide an insulating effect to the shroud. In one embodiment, the shroud may comprise a plurality of vertically-stacked self-supported shroud segments which are coupled together.

Abstract: A control rod drive system (CRDS) for use in a nuclear reactor. In one embodiment, the system generally includes a drive rod mechanically coupled to a control rod drive mechanism (CRDM) operable to linearly raise and lower the drive rod along a vertical axis, a rod cluster control assembly (RCCA) comprising a plurality of control rods insertable into a nuclear fuel core, and a drive rod extension (DRE) releasably coupled at opposing ends to the drive rod and RCCA. The CRDM includes an electromagnet which operates to couple the CRDM to DRE. In the event of a power loss or SCRAM, the CRDM may be configured to remotely uncouple the RCCA from the DRE without releasing or dropping the drive rod which remains engaged with the CRDM and in position.

Abstract: A control rod drive system (CRDS) for use in a nuclear reactor. In one embodiment, the system generally includes a drive rod mechanically coupled to a control rod drive mechanism (CRDM) operable to linearly raise and lower the drive rod along a vertical axis, a rod cluster control assembly (RCCA) comprising a plurality of control rods insertable into a nuclear fuel core, and a drive rod extension (DRE) releasably coupled at opposing ends to the drive rod and RCCA. The CRDM includes an electromagnet which operates to couple the CRDM to DRE. In the event of a power loss or SCRAM, the CRDM may be configured to remotely uncouple the RCCA from the DRE without releasing or dropping the drive rod which remains engaged with the CRDM and in position.

Abstract: An autonomous self-powered system for cooling radioactive materials comprising: a pool of liquid; a closed-loop fluid circuit comprising a working fluid having a boiling temperature that is less than a boiling temperature of the liquid of the pool, the closed-loop fluid circuit comprising, in operable fluid coupling, an evaporative heat exchanger at least partially immersed in the liquid of the pool, a turbogenerator, and a condenser; one or more forced flow units operably coupled to the closed-loop fluid circuit to induce flow of the working fluid through the closed-loop fluid circuit; and the closed-loop fluid circuit converting thermal energy extracted from the liquid of the pool into electrical energy in accordance with the Rankine Cycle, the electrical energy powering the one or more forced flow units.

Abstract: An environmentally sequestered nuclear spent fuel pool in one embodiment includes sidewalls and a base slab that confine a water impoundment. The pool includes fuel racks containing spent fuel assemblies which heat the water via radioactive decay. A dual liner system enclosing the pool forms an impervious barrier providing redundant provisions for preventing leakage of contaminated pool water into the environment. An interstitial space is formed between the liners which may be maintained at sub-atmospheric pressures by a vacuum pump system that evacuates the space. By maintaining the pressure in the space at a negative pressure with corresponding boiling point less than the temperature of the pool water, any leakage through the inner-most liner into the interstitial space will vaporize and be extracted via the pump for signaling a potential leak in the liner system.