40 lines
2.7 KiB
Markdown
40 lines
2.7 KiB
Markdown
# Executive Summary
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MARVEL stands for Microreactor Applications Research Validation and Evaluation. MARVEL
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is an 'open-source' microreactor design that is coming out of the Idaho National
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Laboratory. This 'open-source' idea is a response to commerical reactors such as eVinci
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from Westinghouse being closed-door endeavors. This isn't great, because it doesn't
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allow a place for everyone to communicate about designs. This is especially relevant
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for microreactors, where the low power model and economy-of-production model really
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benefits from common knowledge being out there.
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MARVEL is a unique design that I haven't really seen before. First of all, coolant
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is by natural convection. This reactor system uses two coolant loops: the primary loop
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is sodium-potassium salt, while the secondary coolant is lead. These two fluids
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drive 'Stirling Engines', which are how the system generates power.
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>[!info] # What are Stirling Engines?
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>- [x] What are Stirling Engines? #MARVEL ✅ 2025-03-21
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>
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> Stirling engines are heat engines that directly convert heat energy into mechanical energy.
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> How they work is they have a piston that travels back and forth from a hot side to a cold side.
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> When the cylinder travels over the hot side the volume of air on that side heats up from the hot
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> walls and expands, forcing the cylinder in the direction of the cold fluid. At the same time,
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> that fluid is getting colder, decreasing in pressure, and creating a vacuum. Then, once the piston
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> moves to the cold side, the chamber compresses, removing the cooling, and heats up pushing
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> the piston back towards the hots side. Here's a graphic:
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> ![[Pasted image 20250321163711.png]]
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>
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Anyways, MARVEL also uses an interesting drum based system to do power control.
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They use one big central 'insurance' rod, but also have four drums around the cylindrical
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core. These drums have a poison side, whose angle of incidence on the reactor plays a large part in how much neutron fission is allowed to happen. These drums have a fail-close state, that if something
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were to happen to the controller, they would passively return to a shut position. To keep the poison
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faces from killing with the reactor, the controller must actively apply force to the drums to prevent
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them rotating.
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These drum based control systems have a significant advantage that they don't create a
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longitudinal imbalance in reaction rate, compared to a typical control rod. Since they face / shy from
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the entire core equally along its length, they can probably be more efficiient, and take up way less
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space. The insurance rod is a typical rod however, as it would not be possible to put a rotating
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control drum in the middle of a cylinder. 🤷♂️ |