Glossary of Terms

Glossary: ReCore.One terminology

Terms used in the ReCore engineering concept (nuclear physics, materials, heat transport, pyroprocessing). Definitions support educational pages; they are not design guarantees.

Reactor & Physics

• SFR (Sodium Fast Reactor): A reactor that uses liquid sodium as a coolant and operates in the fast neutron spectrum, allowing for the burning of transuranic elements.
• Fast Spectrum: A neutron energy regime where neutrons have high kinetic energy, enabling them to fission heavy isotopes that build up as waste in traditional reactors.
• Negative Void Coefficient: A safety characteristic where the loss of coolant density (voiding) naturally reduces the reactor’s power level.
• Actinides: Heavy radioactive elements with atomic numbers 89 to 103. In the context of waste, it specifically refers to long-lived Transuranics.
• TRU (Transuranic Elements): Elements heavier than Uranium (e.g., Plutonium, Americium, Curium) that are the primary cause of long-lived nuclear waste radiotoxicity.

Engineering & Materials

• ALIP (Annular Linear Induction Pump): An electromagnetic pump with no moving parts that moves liquid sodium using travelling magnetic fields.
• Bayonet HX (vertical shrouded bayonet-tube exchanger): Na→N₂ module in which nitrogen flows down a removable cartridge and back up the annulus around it, while sodium flows axially on the shell. ReCore’s baseline primary heater: six 120 MWth modules, smooth Alloy 709 pressure tubes, one top tubesheet in the dry argon plenum. See architecture.
• Swirl cartridge: Removable thin-walled stainless insert inside each bayonet pressure tube. Insulated so the cold downward nitrogen does not short-circuit against the hot return. Helical ribs or wire-wrap on its outer surface drive swirl in the annulus. It is a flow insert at near-zero differential pressure, not the 80 bar boundary.
• PCHE (Printed-circuit heat exchanger): Diffusion-bonded block with fine chemically etched channels. Not used on the primary sodium boundary: the channels are hard to inspect, and widening them loads the block in bending. It is the class used for the nitrogen recuperator, where a smooth gas channel keeps pressure drop down. The coolers are a different class (plate-and-shell or shell-and-tube).
• Alloy 709: Fe-20Cr-25Ni advanced austenitic stainless steel. Screening reference for the smooth 80 bar pressure tube and the single top tubesheet — higher creep strength near 600 °C than 316LN, so a ~1.5 mm wall is the reference. Commercial tube supply and the code case are open.
• Alloy 800H: Iron–nickel–chromium alloy (UNS N08810, about 30–35% Ni). Widely available as heat-exchanger tube and already in high-temperature code practice. A candidate for the bayonet tube, not the selected alloy: the higher nickel content raises sodium mass transfer between the hot and cold legs, which still has to be qualified.
• RVACS: Reactor vessel auxiliary cooling — air on the outside of a guard vessel. On the screening vessel (about 2.4 m × 6.2 m) the area rejects on the order of 1 MW, short of blackout decay heat.
• DRACS / dip cooler: A decay-heat exchanger in the primary sodium, with the sink outside. In-vessel units need annulus space this vessel does not have. The matching form for this loop plant is an always-open external sodium-to-air loop with a fail-open stack, on the order of 10 MW for the first hour. Not sized.
• ALD (Acoustic Leak Detection): High-temperature ultrasonic hydrophones in sodium, able to hear gas entering liquid sodium. In this concept, an optional diverse monitor only. The baseline tube-shear argument is buoyancy into the argon plenum, not acoustic detection.
• Swirl ribs: Helical ribs or wire-wrap on the outside of the removable bayonet cartridge. They sit in the gas annulus and are not part of the pressure tube.
• HT9: Ferritic–martensitic steel used as the baseline fuel cladding for ReCore metallic fuel; strong heritage in SFR metal-fuel programmes (e.g. FFTF / EBR-II class).
• P92 / NF616 / Grade 92: Advanced 9%Cr creep-resistant steels (power-plant pedigree). Optional cladding upgrades at fuel exchange when qualified for SFR metal-fuel duty — not required for FOAK cores.
• ODS Steel (Oxide Dispersion Strengthened): Oxide-dispersion alloys studied for high-flux cladding; not the ReCore baseline (kept only as a possible long-term R&D option outside the core concept).
• LVEB (Local Vacuum Electron Beam Welding): A precision welding technology that creates a localized vacuum over the weld seam, allowing for high-integrity joining of large structures on-site without a full vacuum chamber.

Recycling & Chemistry

• Pyroprocessing: A high-temperature, electrochemical recycling method for nuclear fuel that operates in molten salts rather than aqueous acids.
• LCC (Liquid Cadmium Cathode): A specialized component in an electrorefiner that co-deposits Plutonium and other actinides, ensuring they are never isolated in pure form.
• Electrorefiner: The heart of the pyroprocessing facility where electricity separates uranium and transuranics from fission products.
• Sodalite: A synthetic ceramic waste form used to permanently immobilize salt-based nuclear waste.

Strategy & Deployment

• TRL (Technology Readiness Level) {#trl}: A 1–9 maturity scale (NASA/EU-style) from basic principles to proven commercial systems. ReCore pages use estimated component TRLs and heritage notes; they are not official certified scores, and a full FOAK plant is not claimed as TRL 9.
• Iso-Breeder: A reactor design that produces exactly as much fissile material as it consumes, allowing for long-term operation without requiring fresh enrichment or fuel imports.
• FOAK (First-Of-A-Kind): The first full-scale deployment of a new technology or design.
• Bridge Fuel: Metallic U-Pu-Zr made from separated civilian plutonium and depleted uranium, used for the first cores before a pyroprocessing hub returns U-TRU-Zr. Fresh bridge fuel is Category I material. It is not self-protecting.
• EPZ (Emergency Planning Zone): The area around a nuclear plant with specific emergency planning requirements. EPZ size is a regulatory outcome, not something a concept document can assert; ReCore does not claim a site-boundary EPZ as achieved.