EP-4736193-A2 - A NUCLEAR REACTOR SYSTEM AND METALLIC COOLANT COMPOSITION

EP4736193A2EP 4736193 A2EP4736193 A2EP 4736193A2EP-4736193-A2

Abstract

One variation of a system includes: a nuclear reactor; a shield arranged about the nuclear reactor; a metallic coolant; and a set of melt seals. The nuclear reactor includes a pressure vessel and nuclear fuel arranged within a lower region of the pressure vessel. The metallic coolant includes a mixture of metals and is configured to: occupy a liquid state within an operating temperature range; occupy an interstitial volume between the nuclear reactor and the shield; and occupy the lower region of the pressure vessel encompassing the nuclear fuel. The set of melt seals are arranged on the pressure vessel and configured to open to enable transfer of a volume of the metallic coolant from the interstitial volume into the lower region of the pressure vessel in response to temperatures within the pressure vessel exceeding the operating temperature range.

Inventors

KUGELMASS, BRET
BLOMSTROM, Mark
COLE, CHARLES
LIND, Phoebe
THEOBALD, DANIEL

Assignees

Last Energy Inc.

Dates

Publication Date: 20260506
Application Date: 20240627

Claims (1)

CLAIMS I claim: 1. A system comprising: • a shield: o defining an internal volume; and o configured to absorb radiation; a nuclear reactor comprising: o a pressure vessel: ■ arranged within the internal volume; and ■ defining: • an upper region; • a lower region arranged below the upper region; and • an upper seal slot interposed between the upper region and the lower region; o a nuclear fuel arranged within the lower region of the pressure vessel and configured to heat a working fluid entering the pressure vessel, via a fission reaction; and o a set of control rods configured to transition between the upper region and the lower region of the pressure vessel to moderate the fission reaction within the nuclear fuel; a metallic coolant: o comprising a mixture of metals in a liquid state within an operating temperature range of the nuclear reactor; and o configured to: ■ occupy an interstitial volume between the shield and the pressure vessel; ■ transfer thermal energy from the pressure vessel into the shield to distribute heat around the pressure vessel within the operating temperature range; and ■ absorb radiation emitted by the nuclear reactor; and a first melt seal: o arranged in the upper seal slot of the pressure vessel; o configured to retain a volume of the metallic coolant within the interstitial volume between the shield and the pressure vessel during operation of the nuclear reactor; and o configured to unseal from the upper seal slot to release the volume of the metallic coolant, in a first direction, into the lower region of the pressure vessel in response to temperatures within the pressure vessel exceeding the operating temperature range. 2. The system of Claim 1: wherein the pressure vessel defines a lower seal slot: o proximal a base of the pressure vessel; and o aligned with and vertically offset from the upper seal slot along a vertical axis of the pressure vessel; and further comprising a second melt seal: o arranged in the lower seal slot of the pressure vessel; o configured to cooperate with the first melt seal to retain the volume of the metallic coolant within the interstitial volume between the shield and the pressure vessel during operation of the nuclear reactor; and o configured to unseal from the lower seal slot to release the volume of the metallic coolant, in a second direction opposite the first direction, into the lower region of the pressure vessel in response to temperatures within the pressure vessel exceeding the operating temperature range. 3 The system of Claim 1, wherein the mixture comprises: a first proportion of lead configured to decrease an effective melting temperature of the mixture and absorb gamma radiation emitted by the nuclear fuel; and a second proportion of bismuth configured to absorb gamma radiation emitted by the nuclear fuel and to increase an effective boiling temperature of the metallic coolant. 4 The system of Claim 3, further comprising a set of particles, in suspension within the metallic coolant: comprising a third proportion of metal-impregnated ceramic; defining a diameter less than a minimum diameter of the first melt seal; and configured to flow through the first melt seal into the lower region of the pressure vessel, in response to temperatures within the pressure vessel exceeding the operating temperature range and in response to pressures within the pressure vessel exceeding an operating pressure range. 5. The system of Claim 1: • wherein the nuclear reactor is configured to operate within the operating temperature range between 150 degrees Celsius and 450 degrees Celsius; and • wherein the metallic coolant is characterized by an effective boiling temperature greater than the operating temperature range to maintain homogeneity of the mixture of metals at temperatures outside of the operating temperature range. 6. The system of Claim 1, wherein the pressure vessel comprises: a fluid inlet configured to: o receive the working fluid from an external water reservoir, via a working fluid supply line, at a first flow rate; and o direct the working fluid toward the nuclear fuel to moderate the fission reaction and absorb thermal energy from the nuclear fuel; and a fluid outlet configured to: o emit the working fluid from the pressure vessel to an external thermal power generation system for conversion of thermal energy into electricity, at a second flow rate proportional to the first flow rate; and o cooperate with the fluid inlet to maintain pressures within the pressure vessel within a target pressure range. 7 The system of Claim 1: wherein the pressure vessel defines a second upper seal slot interposed between the upper region and the lower region of the pressure vessel; wherein the first melt seal comprises a first melt plug: o arranged in a first lateral position in the upper seal slot of the pressure vessel; o laterally offset from a vertical axis of the pressure vessel; and o configured to release a first subvolume of the metallic coolant, in the first direction, into the lower region of the pressure vessel in response to the temperature within the pressure vessel exceeding the operating temperature range; and further comprising a second melt plug: o arranged in a second lateral position in the second upper seal slot of the pressure vessel; o laterally offset from the vertical axis of the pressure vessel opposite the first melt plug; and o configured to unseal from the lower seal slot to release a second subvolume of the metallic coolant, in the first direction, into the lower region of the pressure vessel in response to the temperature within the pressure vessel exceeding the operating temperature range. 8. The system of Claim 1: wherein the nuclear fuel comprises a fissile material; and wherein the pressure vessel comprises a set of fuel rods, each fuel rod in the set of fuel rods: o defining a minimum diameter within a target diameter range; o defining a lateral pitch distance: ■ greater than the minimum diameter; and ■ less than a maximum diameter of the lower region of the pressure vessel; o configured to house the fissile material; and o arranged in a radial pattern about a vertical axis of the pressure vessel to enable working fluid to maintain the operating temperature range of the nuclear reactor. 9 The system of Claim 8: wherein the nuclear reactor defines the upper seal slot of a first size; wherein the set of fuel rods are arranged at a first height within the lower region of the pressure vessel; and wherein the first melt seal is: o characterized by a second size less than the first size; o arranged at a second height, greater than the first height, between the upper region and the lower region of the pressure vessel; and o configured to transport the volume of the metallic coolant into the lower region of the pressure vessel at a first coolant flow rate, corresponding to the first size and the second height, to reduce impact between the volume of the metallic coolant and the set of fuel rods. 10 The system of Claim 1, wherein the mixture comprises: • a first proportion of lead configured to decrease an effective melting temperature of the mixture and absorb gamma radiation emitted by the nuclear fuel; • a second proportion of bismuth configured to absorb gamma radiation emitted by the nuclear fuel and to increase an effective boiling temperature of the metallic coolant; and • a third proportion of tin configured to decrease a viscosity of the metallic coolant. n. A system comprising: a nuclear reactor comprising: o a pressure vessel; and o a nuclear fuel arranged within a lower region of the pressure vessel; a shield arranged about the nuclear reactor; a metallic coolant: o comprising: ■ a first proportion of a first metal; and ■ a second proportion of a second metal; o operable in a first configuration, the metallic coolant: ■ occupying a liquid state within an operating temperature range of the nuclear reactor; and ■ occupying an interstitial volume between the nuclear reactor and the shield in the first configuration; and o operable in a second configuration, the metallic coolant: ■ occupying the liquid state within the operating temperature range; ■ occupying the interstitial volume between the nuclear reactor and the shield; ■ occupying the lower region of the pressure vessel encompassing the nuclear fuel; ■ absorbing radiation and thermal energy emitted by the nuclear fuel; and ■ displacing moderator and working fluid from the lower region of the pressure vessel toward the shield in the second configuration; and a set of melt seals: o arranged on the pressure vessel; and o configured to open to enable transfer of a volume of the metallic coolant from the interstitial volume into the lower region of the pressure vessel in response to temperatures within the pressure vessel exceeding the operating temperature range. 12. The system of Claim n: • wherein the pressure vessel defines: o an upper region; o the lower region arranged below the upper region; and o an upper seal slot interposed between the upper region and the lower region; wherein the nuclear fuel is arranged in the lower region of the pressure vessel; and wherein the set of melt seals comprises a set of melt plugs: o arranged within the upper seal slot of the pressure vessel; and o configured to rupture at a threshold operating temperature, exceeding the operating temperature range, of the nuclear reactor to pass subvolumes of the metallic coolant from the interstitial volume into the lower region of the pressure vessel. 13. The system of Claim 11: wherein the first proportion of the first metal comprises lead and is configured to absorb gamma radiation emitted by the nuclear fuel and reduce a melting temperature of the metallic coolant; and wherein the second proportion of the second metal comprises bismuth and is configured to: o absorb gamma radiation emitted by the nuclear fuel; o increase an effective boiling temperature of the metallic coolant; and o cooperate with the first proportion of the first metal to reduce the melting temperature of the metallic coolant. 14. The system of Claim 11: wherein the pressure vessel defines: o an upper region; and o the lower region arranged below the upper region; and further comprising: o a set of control rods: ■ extending parallel to a vertical axis of the pressure vessel; and ■ configured to transition between a retracted position in the upper region and an extended position in the lower region to moderate a fission reaction within the nuclear fuel; o a metallic coolant reservoir: ■ arranged within the upper region of the pressure vessel; ■ defining a diameter: • less than a minimum inner diameter of the pressure vessel; and • greater than a combined diameter of the set of control rods; and ■ configured to contain a second volume of the metallic coolant during an operating period; and o a second set of melt seals: ■ arranged on a base of the metallic coolant reservoir; and ■ configured to unseal from the base to pass the second volume of the metallic coolant from the metallic coolant reservoir toward the nuclear fuel during a cooldown period; and wherein the set of melt seals are configured to maintain the volume of the metallic coolant within the interstitial volume during the cooldown period. 15. The system of Claim 11, wherein in a third configuration, the metallic coolant: transitions from the liquid state to a solid state to render a nuclear coffin encasing the nuclear fuel; and prevents emission of nuclear radiation from the nuclear reactor. 16. A metallic coolant composition comprising: a first proportion of lead configured to absorb gamma radiation emitted by a nuclear fuel within a nuclear reactor; and a second proportion of bismuth configured to: o absorb gamma radiation emitted by the nuclear fuel; o increase an effective boiling temperature of the metallic coolant composition; and o cooperate with the first proportion of lead to: ■ maintain the metallic coolant composition in a liquid state within an operating temperature range of the nuclear reactor; and ■ occupy a volume adjacent the nuclear reactor. 17- The metallic coolant composition of Claim 16: • wherein, in a first configuration, the metallic coolant composition: o occupies the volume between the nuclear reactor and a shield arranged about the nuclear reactor; and o transfers thermal energy from the nuclear reactor to the shield in the first configuration; and wherein in a second configuration, the metallic coolant composition flows through a melt seal, in response to a temperature within the nuclear reactor exceeding an operating temperature range, to: o occupy an internal volume of the nuclear reactor proximal the nuclear fuel; o replace moderator within the nuclear reactor to maintain the nuclear reactor in a subcritical state; o displace working fluid within the internal volume of the nuclear reactor; o absorb radiation from the nuclear fuel; and o pass thermal energy from the nuclear fuel to the shield. 18. The metallic coolant composition of Claim 16: exhibiting a first density between 5 g/ cm3 and 20 g/ cm ; and comprising a set of particles in suspension within the metallic coolant composition: o comprising a third proportion of boron carbide configured to absorb neutron radiation emitted by the nuclear fuel succeeding the over-temperature event; and o comprising a fourth proportion of tungsten; and o exhibiting a second density less than the first density. 19. The metallic coolant composition of Claim 16, further comprising: a third proportion of tin configured to decrease a viscosity of the metallic coolant composition; and a fourth proportion of cadmium configured to: o absorb neutron radiation emitted by the nuclear fuel succeeding an overtemperature event of the nuclear reactor; and o cooperate with the first proportion of lead, the second proportion of bismuth, and the third proportion of tin to maintain the metallic coolant composition in the liquid state within the operating temperature range of the nuclear reactor. 20. The metallic coolant composition of Claim 16: • wherein the first proportion of lead and the second proportion of bismuth form an eutectic alloy: o comprising between 55% and 56% by weight of lead; o comprising between 44% and 45% by weight of bismuth; and o characterized by the effective boiling temperature greater than the operating temperature range of the nuclear reactor; and wherein the operating temperature range is between 150 degrees Celsius and 400 degrees Celsius.

Description

A NUCLEAR REACTOR SYSTEM AND METALLIC COOLANT COMPOSITION CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This Application claims the benefit of U.S. Provisional Application No. 63/523,885 filed on 28-JUN-2023, which is incorporated in its entirety by this reference. TECHNICAL FIELD [0002] This invention relates generally to the field of nuclear reactors and more specifically to a new and useful nuclear reactor system with an emergency heat removal system in the field of nuclear reactors. BRIEF DESCRIPTION OF THE FIGURES [0003] FIGURE 1 is a schematic representation of a system; [0004] FIGURE 2 is a schematic representation of one variation of the system; [0005] FIGURES 3A and 3B are a schematic representation of one variation of the system; [0006] FIGURE 4 is a schematic representation of one variation of the system; [0007] FIGURE 5 is a schematic representation of one variation of the system; and [0008] FIGURE 6 is a schematic representation of one variation of the system. DESCRIPTION OF THE EMBODIMENTS [0009] The following description of embodiments of the invention is not intended to limit the invention to these embodiments but rather to enable a person skilled in the art to make and use this invention. Variations, configurations, implementations, example implementations, and examples described herein are optional and are not exclusive to the variations, configurations, implementations, example implementations, and examples they describe. The invention described herein can include any and all permutations of these variations, configurations, implementations, example implementations, and examples. 1, System [0010] As shown in FIGURES 1 and 2, a system 100 includes: a shield no; a nuclear reactor 120; a metallic coolant 140; and a melt seal 150. [oon] The shield no defines an internal volume and is configured to absorb radiation. [0012] The nuclear reactor 120 includes: a pressure vessel 130; a nuclear fuel 124; and a set of control rods 122. The pressure vessel 130: is arranged within the internal volume; defines an upper region 132; defines a lower region 134 arranged below the upper region 132; and an upper seal slot 152 interposed between the upper region 132 and the lower region 134. The nuclear fuel 124 is arranged within the lower region 134 of the pressure vessel 130 and is configured to heat a working fluid 160 entering the pressure vessel 130, via a fission reaction. The set of control rods 122 are configured to transition between the upper region 132 and the lower region 134 of the pressure vessel 130 to moderate the fission reaction within the nuclear fuel 124. [0013] The metallic coolant 140: includes a mixture of metals in a liquid state within an operating temperature range of the nuclear reactor 120; is configured to occupy an interstitial volume 112 between the shield no and the pressure vessel 130; transfers thermal energy from the pressure vessel 130 into the shield no to distribute heat around the pressure vessel 130 within the operating temperature range; and absorbs radiation emitted by the nuclear reactor 120. [0014] The melt seal 150 is: arranged in the upper seal slot 152 of the pressure vessel 130; configured to retain a volume of the metallic coolant 140 within the interstitial volume 112 between the shield 110 and the pressure vessel 130 during operation of the nuclear reactor 120; and configured to unseal from the upper seal slot 152 to release the volume of the metallic coolant 140, in a first direction, into the lower region 134 of the pressure vessel 130 in response to temperatures within the pressure vessel 130 exceeding the operating temperature range. 1.1 Variation: Eutectic Alloy + Multiple Melt Seals [0015] In one variation shown in FIGURE 4, the system 100 includes: a nuclear reactor 120; a shield no; a metallic coolant 140; and a set of melt seals 150. [0016] The nuclear reactor 120 includes a pressure vessel 130 and a nuclear fuel 124 arranged within a lower region 134 of the pressure vessel 130. [0017] The shield 110 is arranged about the nuclear reactor 120. [0018] The metallic coolant 140 includes: a first proportion of a first metal; and a second proportion of a second metal. The metallic coolant 140 is operable in a first configuration, the metallic coolant 140 occupying a liquid state within an operating temperature range of the nuclear reactor 120 and occupying an interstitial volume 112 between the nuclear reactor 120 and the shield no in the first configuration. The metallic coolant 140 is further operable in a second configuration, the metallic coolant 140: occupying the liquid state within the operating temperature range; occupying the interstitial volume 112 between the nuclear reactor 120 and the shield no; occupying the lower region 134 of the pressure vessel 130 encompassing the nuclear fuel 124; absorbing radiation and thermal energy emitted by the nuclear fuel 124; and displacing moderator and working fluid 160 from the lower region 134 of the pr