# How a Portable Nuclear Reactor Stays Stable During Operation > This patent describes a small, portable nuclear fission reactor designed to be moved by ship, train, or truck, featuring a special internal design to keep its fuel and control rods stable and centered during operation. - **Patent:** US 11495363 - **Original title:** Small modular mobile fission reactor - **Owner:** BWXT Advanced Technologies - **Granted:** 2022 - **Status:** Active - **Times cited:** 6 - **Field:** energy, mechanical, nuclear_power, telecommunications ## What it does This patent describes a "mobile, graphite-moderated fission reactor" (Claim 1) that is small enough to be transported by "ship, train or truck" (Claim 1). The reactor includes a "pressure vessel" that holds an "active core region" with "fuel assemblies" and "control systems" (Claim 1). A key part of the design involves "flow annulus features" (Claim 1), which are small structures attached to the inner surface of the cladding (the outer tube) around the fuel rods. These features are placed at different points along the rod's length and are rotationally offset from each other at successive points (Claim 1). This specific arrangement helps keep the fuel rods perfectly centered within their channels, ensuring stable operation by maintaining a consistent gap for coolant flow. For example, such a reactor could be built in a factory, loaded onto a flatbed truck, and driven to a remote location to provide power. ## What it does NOT cover - Does not cover large, stationary nuclear power plants that are not designed for mobile transport. - Does not cover reactors that are not specifically "graphite-moderated" (Claim 1). - Does not cover mobile reactors that lack the specific "flow annulus features" for stabilizing fuel and control rods as described in Claim 1. - Does not cover reactors where the "flow annulus features" are not rotationally offset at successive longitudinal locations (Claim 1). - Does not cover reactors that are not sized for transport using a "ship, train or truck" (Claim 1). ## The clever bit The clever bit is the specific design of the "flow annulus features," which are not just simple spacers. By distributing them circumferentially and then rotationally offsetting them at different points along the rod, the design ensures robust centering and stability of the fuel and control rods within their channels. This is crucial for safety and efficient heat transfer, especially in a reactor designed for mobility. ## Real-world examples 1. BWXT Advanced Technologies microreactor designs 2. Other Small Modular Reactor (SMR) development projects 3. Future mobile power units for military or disaster relief 4. Deployable power solutions for remote mining or research outposts ## Why it matters Small Modular Reactors (SMRs) are a growing area of interest for providing flexible, carbon-free power to remote locations, disaster relief efforts, or specialized industrial sites. This patent addresses a critical engineering challenge for such reactors: ensuring the stability and safety of the core components, like fuel and control rods, especially when the reactor is designed to be moved. By focusing on transportability and internal stability, it contributes to making SMRs a more viable option for diverse energy needs. ## Frequently asked questions ### What does How a Portable Nuclear Reactor Stays Stable During Operation cover? This patent describes a small, portable nuclear fission reactor designed to be moved by ship, train, or truck, featuring a special internal design to keep its fuel and control rods stable and centered during operation. ### Who owns patent US 11495363? BWXT Advanced Technologies owns this patent, granted in 2022. ### When does this patent expire? This patent is expected to expire on May 1, 2040, when the invention enters the public domain. ### What is patent US 11495363 cited by? This patent has been cited by 6 later patents that build on its ideas. ### What problem does this patent solve? Small Modular Reactors (SMRs) are a growing area of interest for providing flexible, carbon-free power to remote locations, disaster relief efforts, or specialized industrial sites. This patent addresses a critical engineering challenge for such reactors: ensuring the stability and safety of the core components, like fuel and control rods, especially when the reactor is designed to be moved. By focusing on transportability and internal stability, it contributes to making SMRs a more viable option for diverse energy needs. ### What does this patent NOT cover? Does not cover large, stationary nuclear power plants that are not designed for mobile transport. **Full plain-English explainer:** https://patentbrief.org/patent/us/11495363/small-modular-mobile-fission-reactor **Original patent:** https://patents.google.com/patent/US11495363 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How a Molten Metal Buffer Improves Heat Transfer in Nuclear Reactors](https://patentbrief.org/patent/us/11942229/molten-metal-fuel-buffer-in-fission-reactor-and-method-of-manufacture) — This patent describes a nuclear fission reactor design that uses a liquid molten metal to fill gaps between the nuclear fuel and its protective casing, improving heat transfer and reactor safety. - [How a Nuclear Reactor's Rotating Drum Controls Power](https://patentbrief.org/patent/us/11417435/control-drum-for-a-mobile-nuclear-reactor) — This patent describes a rotating drum for nuclear reactors, especially mobile ones, that uses tubes filled with different materials to absorb or scatter neutrons, precisely controlling the reactor's power output. - [How Nuclear Power Plants Reuse Fuel Between Multiple Reactors](https://patentbrief.org/patent/us/10818403/inter-module-fuel-shuffling) — This patent describes a method for nuclear power plants with several reactors to efficiently reuse partially used fuel by moving it between different reactor cores across multiple operating cycles. - [Using Gas Pressure to Safely Control Liquid Fuel Nuclear Reactors](https://patentbrief.org/patent/us/12073952/fail-safe-reactivity-compensation-method-for-a-nuclear-reactor) — This patent describes a method to control a nuclear reaction in liquid-fueled reactors by using gas pressure to adjust the amount of fuel solution in special pipes, ensuring the reactor always returns to a safe state if something goes wrong. - [TerraPower's Molten Salt Reactor with Internal Heat Exchangers](https://patentbrief.org/patent/us/11728052/fast-spectrum-molten-chloride-test-reactors) — This patent describes a unique molten salt nuclear reactor design by TerraPower, featuring an open-topped vessel and integrated heat exchangers for efficient internal cooling and fuel circulation.