Elysium is designing and building Molten Chloride Salt Fast Reactors with an output between 50 and 1200 MW(e). The MCSFR is a modular configuration and construction reactor. The MCSFR enables the closing of the fuel cycle, while providing reliable, passively-safe, proliferation-resistant, and environmentally-friendly energy (heat/electricity) generation. The fuel is part of the liquid heat transport eutectic fluid with heat directly deposited in the liquid fuel/coolant.

Major Technical Parameters

• Reactor type: MSR - Fast Chloride
• Coolant/moderator: NaCl-XCl-YCl2>-UCl3/4-PuCl3-FPCly fuel salt/None
• Primary circulation: Forced circulation
• Thermal/electrical capacity, MW(t)/MW(e): (125/50),(500/200),(1000/400),(3000/1200)
• NSSS Operating Pressure: 0.1+pump head+hydrostatic/ slightly higher
• Fuel type/assembly array: Molten Chloride Salt
• Fuel enrichment (%): 10% Pu fissile/(Pu+U total) or ~15% enriched HALEU
• Core Discharge Burnup (GWd/ton): 300-500 (40-60 years), fertile added, fuel never damaged
• Purification cycle (months): 480-720
• Main reactivity control mechanism: Fuel expansion in/out of core; Fertile fuel addition; Passive fuel draining
• Approach to safety systems: Passive to Air Cooling
• Design life(years): Unlimited core, 15-40 for components, 100+ for plant
• Plant footprint(m2): 1/3 size of LWR
• RV height/diameter (m): 9/4
• Seismic design (SSE): Tension skirt Lateral snubbers
• Fuel cycle requirements/Approach: U/Pu Closed Fuel Cycle SNF/DU/NU (1t/GWe-yr)
• Distinguishing features: Fast spectrum, no in-core structure, 60 years fuel life
• Design Status: Conceptual design

The MCSFR is designed for mass production for domestic use and export to address global markets for cost- competitive, low-emission electricity, and high temperature process heat (e.g.: H2, syn-fuel, syn-fertilizer, desalination, district heating, cement, steel, etc).

The MCSFR uses Spent Nuclear Fuel (SNF), plutonium (Pu), or depleted uranium (DU) ‘waste’ with fuel production denaturing and complete consumption (e.g.: US, Canada, UK, Japan, South Korea, etc.), as fuel sources for internal or export applications and developing countries with fuel take-back.

Utilities can ‘start small’, then add heat exchangers (Hx’s) to increase capacity without purchasing and licensing a new reactor.

Nuclear Heat (Steam) Supply System (NHSS) The MCSFR has a fuel/coolant loop, clean intermediate salt loop same as fuel salt, without the fuel/fission products (FPs), etc., the steam super-heater (SH) loop all inside containment, with a Loeffler steam boiler, outside of containment. The reactor has 1 to 6 Hx/pump loops for each fuel and clean salt loop. Each of the loops can be used for 6 different heat applications/customers. Loops can operate at variable power up to maximum with fuel cost not a concern at part-load.

Reactor and Core-unit The core size is minimized to barely maintain criticality with no in-core structures and is near spherical. The RV and all fuel and intermediate component shells are cooled by cold coolant inside, so includes pipe-in-pipe nozzles. The core is pure salt, except for a downcomer shroud near the edge of the core, and the lower RV is the core edge with an ex-RV radial reflector and above core reflector/shield.

Power Conversion System and Cogeneration The intermediate clean salt heats power conversion unit (PCU) saturated steam to SH steam in the SH, with 35% of SH steam to the steam rankine turbine-generator (40-50% efficiency) and 65% of SH steam to the Loeffler boiler. The use of a salt to SH, i.e. a gas Hx allows use of other process heat gasses, especially at 950oC, on a per Hx basis to allow flexibility of products. With the high outlet temperatures, process heat applications include H2, synthetic fuel and fertilizer, oil/gas recovery and refining, industrial process heat, and cement manufacturing. Other applications include district heating/cooling, thermal storage in chloride salt, and desalination. Use of salt to SH Hx’s, dramatically reduces water and potential for transient pressures in containment.

Reactivity Control Reactivity control is via the negative temperature and void coefficients. As the fuel-salt temperature increases the fuel-salt expands and fissile/fuel salt is squeezed out of the core, reducing power and vice versa. The long- term reactivity adjustments are made by on-line fertile fuel additions. The reactor can also be shut down by tripping pumps to allow draining to criticality safe/passively cooled drain/expansion tanks.

Fuel Characteristics The fuel-salt is NaCl-XClv-YClz-UCl3/4-PuCl3-FPCly, allowing it to contain ~30% total actinide Chlorides with a 10-20% fissile fraction and 99.9% actinide consumption. Fissile options include:

• 1) Preferred-Reactor Grade or Weapons Grade Plutonium (RGPu and WGPu) due to revenue and is denatured with SNF, if needed,
• 2) high assay low enriched uranium (HALEU),
• 3) high enriched uranium (HEU) denatured at fuel production site. Fertile options include:
• a) Preferred-LWR/CANDU SNF,
• b) Depleted Uranium (DU),
• c) Natural Uranium (NU), 281
• d) residual U from other mining, coal ash, or seawater extraction,
• e) thorium (Th) combined with >88% U238 for denaturing.

Pu fissile is added for startup only. HALEU requires continued feed-in declining in enrichment over 5-10 years. Fissile is iso-bred plus enough to counteract fission product poison buildup to prevent needing purification for many decades.

Reactor Vessel (RV) The RV is low pressure, thin walled stainless steel, with up to 6 nozzles, cooled by cold fuel salt everywhere inside, and submerged in a cooling/shield tank of clean salt for corrosion prevention/cooling outside. The RV near the core is the core outer diameter and is replaceable separately from the upper RV nozzle region. A reflector, if needed, is outside the RV.

Primary Loop The primary loop is chloride fuel salt. The arrangement is modular, like an HTGR to allow for low temperature containment, yet high temperature for efficiency and process heat applications. Six pipe-in-a-pipes connect in a modular arrangement to up to 6 fuel salt to clean intermediate salt Hx’s, with top mounted pumps after the Hx to prevent motor immersion and heating. Radial dimension is ≤ 4m for road shipping.

Intermediate Loop The intermediate loop is the same salt as the fuel salt without the actinides or FPs, and is at a higher pressure than the fuel salt to ensure any leakage is not of fuel salt outward, inward for dilution/shutdown of the core. The intermediate loop transports heat to the modularly mounted SH Hx, with the intermediate salt pump on top of one end of the SH. Radial dimension is ≤ 4m for road shipping.

Fuel Cycle and Length Approach On-line fertile fuelling is used. Iso-breeding ratio is ~1.014/yr to offset fission product buildup with a doubling time of 50-60 years with a fuel life of 40-60 years when it is sent to a central facility for partial purification and recycling of all actinides, carrier salt components, including all chlorine. The fuel consumption rate is ~1 ton U / GWe-yr. Fuel is added every ~8 hrs-7 days depending on the power level by dropping a fertile pebble into a perforated basket in the drain tank flow path.

Cooling System Four different cooling loops are included: the fuel salt, intermediate salt, the power/process heat loop, and the heat sink loop. With the high temperature and very low fuel cost, dry cooling is an economic alternative.

Proliferation Considerations The MCSFR never contains weapons grade materials. Fuel is not removed for 40-60 years. WGPu or HEU is denatured at the single fuel production facility. Purification at 60 years never separates Pu from U, Cs and Sr. This low separation of FPs reduces recycling cost. Only relatively short-lived, ~100 years to below U background, FPs are removed as waste.

Elysium’s team designed the MCSFR using attributes from:

• 1) water reactors, common, low cost coolant (table salt), fuels (nuclear waste), and qualified materials,
• 2) liquid metal reactors, the low pressure and materials without corrosion concerns,
• 3) gas reactors, the flow pattern for low containment temperatures, and very high peak temperatures,
• 4) heat-pipe reactors, passive temperature dependent on/off heat-pipe decay heat removal.

Elysium philosophy includes mitigating public concerns with passive safety, high thermal and fuel efficiency, SNF/Pu waste denaturing and consumption, dramatically increased fuel supply, elimination of coolant reactions with water/air/structure, significantly reduced construction, fuel, and operational costs, in addition reduced proliferation concerns.