Nuclear reactor system inside a borehole
A nuclear reactor system includes a drillhole that extends from a terranean surface through one or more subterranean formations. The nuclear reactor system includes a reactor core positioned in the drillhole, the reactor core comprising at least one nuclear fuel element. The nuclear reactor system includes a primary coolant system configured to transport a primary fluid coolant between the reactor core and a heat exchanger. The nuclear reactor system includes a secondary coolant system thermally coupled to the primary coolant system via the heat exchanger and configured to transport a secondary fluid coolant between the heat exchanger and the terranean surface.
1 . A nuclear reactor system, comprising:
a drillhole that extends from a terranean surface through one or more subterranean formations;
at least one reactor core positioned in the drillhole, the reactor core comprising at least one nuclear fuel element positioned at a first depth of the drillhole below the terranean surface;
a heat exchanger positioned in the drillhole, the heat exchanger including a fluid barrier positioned at a second depth of the drillhole that is less than the first depth;
a primary coolant system positioned in the drillhole and configured to transport a primary fluid coolant between the at least one reactor core and the heat exchanger, the primary coolant system comprising:
a first pipe having a diameter less than a diameter of the drillhole and being positioned in the drillhole, the at least one reactor core being positioned inside of the first pipe; and
a first annulus defined between the first pipe and a wall of the drillhole,
wherein the first annulus surrounds the first pipe,
wherein the primary coolant system is configured to convey the primary fluid coolant in a downhole direction through the first annulus from the fluid barrier to the at least one reactor core at the first depth, and
wherein the primary coolant system is configured to convey the primary fluid coolant, heated by the reactor core, in an uphole direction inside the first pipe from the at least one reactor core to the fluid barrier at the second depth; and
a secondary coolant system
thermally coupled to the primary coolant system via the heat exchanger,
wherein the secondary coolant system is configured to receive heat across the fluid barrier,
the secondary coolant system comprising:
a second pipe
having a diameter less than the diameter of the drillhole and being positioned in the drillhole; and
a second annulus defined between the second pipe and the wall of the drillhole,
wherein the second annulus surrounds the second pipe,
wherein the secondary coolant system is configured to convey a secondary fluid coolant in a downhole direction through the second annulus from the terranean surface to the fluid barrier at the second depth, and
wherein the secondary coolant system is configured to convey the secondary fluid coolant, heated in the heat exchanger by the primary fluid coolant, in an uphole direction inside the second pipe from the fluid barrier to the terranean surface,
wherein the heated secondary fluid coolant is usable for generating power at the terranean surface.
2 . The nuclear reactor system of claim 1 , wherein the at least one nuclear fuel element comprises a fissile nuclear fuel element.
3 . The nuclear reactor system of claim 2 , wherein the fissile fuel element comprises at least one of enriched uranium, plutonium, uranium or plutonium oxide, or a mixed oxide (MOX).
4 . The nuclear reactor system of claim 1 , comprising at least one canister that at least partially encloses the at least one nuclear fuel element.
5 . The nuclear reactor system of claim 4 , wherein the canister includes a first opening at an uphole end of the canister and a second opening at a downhole end of the canister.
6 . The nuclear reactor system of claim 1 , wherein the primary coolant system is configured to transport the primary fluid coolant between the at least one reactor core and the heat exchanger by at least one of natural circulation or pumping.
7 . The nuclear reactor system of claim 1 , comprising one or more pumps configured to provide a force for transporting the primary fluid coolant between the at least one reactor core and the heat exchanger.
8 . The nuclear reactor system of claim 1 , wherein the secondary coolant system is configured to transport the secondary fluid coolant between the heat exchanger and the terranean surface by natural circulation.
9 . The nuclear reactor system of claim 1 , comprising one or more pumps configured to provide a force for transporting the secondary fluid coolant between the heat exchanger and the terranean surface.
10 . The nuclear reactor system of claim 1 , wherein the primary fluid coolant comprises water.
11 . The nuclear reactor system of claim 1 , wherein the secondary fluid coolant comprises water.
12 . The nuclear reactor system of claim 1 , wherein the heat exchanger is configured to transfer heat from the primary fluid coolant in the primary coolant system to heat the secondary fluid coolant in the secondary coolant system to a higher temperature liquid phase or a gas phase.
13 . The nuclear reactor system of claim 1 , comprising a power conversion system.
14 . The nuclear reactor system of claim 13 , wherein the power conversion system is located at the terranean surface.
15 . The nuclear reactor system of claim 13 , wherein the secondary fluid coolant comprises a power conversion working fluid of the power conversion system.
16 . The nuclear reactor system of claim 1 , wherein the first depth is:
0.5 km to 1.0 km from the terranean surface,
1.0 to 1.5 km from the terranean surface, or
1.5 km or greater from the terranean surface.
17 . The nuclear reactor system of claim 1 , wherein the fluid barrier is configured to fluidly isolate the primary coolant system from the secondary coolant system.
18 . The nuclear reactor system of claim 1 , comprising one or more pipes extending from the terranean surface to a third depth of the drillhole, the third depth being greater than the second depth.
19 . The nuclear reactor system of claim 18 , wherein the one or more pipes is configured to provide the primary fluid coolant to a region of the drillhole below the second depth.
20 . The nuclear reactor system of claim 1 , wherein a diameter of the drillhole is:
thirty-six inches or less, and
eight inches or more.
21 . The nuclear reactor system of claim 1 , wherein the wall comprises a casing that is installed in the drillhole.
22 . The nuclear reactor system of claim 21 , wherein the casing is comprised of a material sufficient to act as a reflector to reflect neutrons generated in the at least one reactor core.
23 . The nuclear reactor system of claim 21 , wherein a material of the casing comprises at least one of carbon steel, stainless steel, ceramic, a plastic material, or fiberglass.
24 . The nuclear reactor system of claim 1 , wherein the at least one reactor core is controllable between a low power output and a maximum power output.
25 . The nuclear reactor system of claim 24 , wherein the at least one reactor core is controllable with a fluid that comprises a neutron absorber.
26 . The nuclear reactor system of claim 25 , wherein the neutron absorber is controllably added to the primary fluid coolant.
27 . The nuclear reactor system of claim 24 , wherein the at least one reactor core is controllable with at least one control rod configured to move near or adjacent the at least one nuclear fuel element.
28 . The nuclear reactor system of claim 1 , wherein the at least one reactor core comprises a first reactor core and the nuclear fuel element comprises a first nuclear fuel element, the system comprising a second reactor core positioned in the drillhole, the second reactor core comprising at least one second nuclear fuel element.
29 . The nuclear reactor system of claim 28 , wherein the first and second reactor cores are individually controllable between a low power output and a maximum power output.
30 . The nuclear reactor system of claim 28 , wherein each of the first and second reactor cores is individually controllable with a fluid that comprises a neutron absorber.
31 . The nuclear reactor system of claim 30 , wherein the fluid is individually transported to each of the first and second nuclear reactor cores through one or more tubes that extends from the terranean surface to the first and second nuclear reactor cores.
32 . The nuclear reactor system of claim 31 , wherein the neutron absorber is controllably added to the fluid.
33 . The nuclear reactor system of claim 1 , comprising one or more void collectors positioned in the primary coolant system and within a flowpath of the primary fluid coolant,
wherein each void collector has a cup shape, a closed end of each void collector facing an uphole direction and an open end of each void collector facing a downhole direction.
34 . The nuclear reactor system of claim 33 , wherein each of the one or more void collectors is attached to a cladding of the at least one nuclear fuel element.
35 . The nuclear reactor system of claim 1 , comprising a reflector configured to reflect neutrons generated in the at least one reactor core without absorbing the neutrons.
36 . The nuclear reactor system of claim 35 , wherein the reflector comprises at least one of beryllium, carbon, a beryllium alloy, or a carbon alloy.
37 . The nuclear reactor system of claim 1 , wherein a particular subterranean formation, of the one or more subterranean formations, that is adjacent the at least one reactor core is configured to act as a reflector to reflect neutrons generated in the at least one reactor core.
38 . The nuclear reactor system of claim 1 , wherein the diameter of the second pipe is less than the diameter of the first pipe, and a downhole end of the second pipe extends into an uphole end of the first pipe.
39 . The nuclear reactor system of claim 1 , wherein a diameter of a downhole portion of the second pipe is greater than a diameter of an uphole portion of the first pipe, and an uphole end of the first pipe extends into a downhole end of the second pipe.
40 . The nuclear reactor system of claim 1 , wherein the fluid barrier includes a pressure equalizer barrier, the pressure equalizer barrier including a permeable material configured to permit fluid to flow through the pressure equalizer barrier, an amount of fluid flow through the pressure equalizer barrier being dependent on a difference in pressure across the pressure equalizer barrier.
41 . A method, comprising:
operating a nuclear reactor system that comprises:
a drillhole that extends from a terranean surface through one or more subterranean formations;
at least one reactor core positioned in the drillhole, the at least one reactor core comprising at least one nuclear fuel element positioned at a first depth of the drillhole below the terranean surface;
a heat exchanger positioned in the drillhole, the heat exchanger including a fluid barrier positioned at a second depth of the drillhole that is less than the first depth;
a primary coolant system positioned in the drillhole, the primary coolant system comprising:
a first pipe having a diameter less than a diameter of the drillhole, the first pipe being positioned in the drillhole, the at least one reactor core being positioned inside of the first pipe; and
a first annulus defined between the first pipe and a wall of the drillhole,
wherein the first annulus surrounds the first pipe; and
a secondary coolant system
thermally coupled to the primary coolant system via the heat exchanger,
wherein the secondary coolant system is configured to receive heat across the fluid barrier,
the secondary coolant system comprising:
a second pipe
having a diameter less than the diameter of the drillhole and
being positioned in the drillhole,
a second annulus defined between the second pipe and the wall of the drillhole,
wherein the second annulus surrounds the second pipe,
wherein the secondary coolant system is configured to convey a secondary fluid coolant between the heat exchanger and the terranean surface,
the operating comprising:
transporting a primary fluid coolant in the primary coolant system
in a downhole direction through the first annulus from the fluid barrier to the at least one reactor core at the first depth and
in an uphole direction inside the first pipe from the at least one reactor core to the fluid barrier at the second depth;
transporting the secondary fluid coolant, heated in the heat exchanger by the primary fluid coolant, in the secondary coolant system in an uphole direction inside the second pipe from the fluid barrier at the second depth to the terranean surface;
generating power with the heated secondary fluid coolant at the terranean surface; and
transporting the secondary fluid coolant in the secondary coolant system in a downhole direction through the second annulus from the terranean surface to the fluid barrier at the second depth.
42 . The method of claim 41 , wherein the fluid barrier fluidly isolates the primary fluid coolant from the secondary fluid coolant.
43 . The method of claim 42 , comprising transporting the primary fluid coolant into the drillhole through one or more pipes extending from the terranean surface to a third depth of the drillhole that is deeper than the second depth of the fluid barrier.
44 . The method of claim 41 , wherein the primary and the secondary fluid coolants comprise water.
45 . The method of claim 41 , wherein the at least one reactor core comprises a first reactor core and the at least one nuclear fuel element comprises a first nuclear fuel element, the nuclear reactor system comprising a second reactor core positioned in the drillhole, the second reactor core comprising at least one second nuclear fuel element.
46 . The method of claim 45 , comprising individually controlling the first and second reactor cores between a low power output and a maximum power output.
47 . The method of claim 41 , comprising maintaining pressure stability of the primary fluid coolant in the drillhole using one or more pipes extending from the terranean surface to a third depth of the drillhole that is deeper than the second depth of the fluid barrier.
48 . The method of claim 41 , wherein the fluid barrier includes a pressure equalizer barrier, the method comprising maintaining pressure stability of the primary fluid coolant in the drillhole using the pressure equalizer barrier.
49 . The method of claim 48 , wherein the pressure equalizer barrier includes a permeable material configured to permit fluid to flow through the pressure equalizer barrier, an amount of fluid flow through the pressure equalizer barrier being dependent on a difference in pressure across the pressure equalizer barrier.