Self-regulating, Solid Core Block for an Inherently Safe Heat Pipe Reactor

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Cranberry Township, Pennsylvania
Project Term:
08/24/2018 - 07/30/2025

Technology Description:

Westinghouse Electric Company will develop a self-regulating "solid core block" (SCB) that employs solid material (instead of bulk liquid flow or moving parts) to passively regulate the reaction rate in a micro-scale nuclear reactor. The project aims for the reactor to achieve safe shutdown without the need for additional controls, external power sources, or operator intervention, enabling highly autonomous operation. The SCB is key to the reactor design, which is comprised of a core (containing fuel, moderator, and axial reflectors) and primary and decay heat exchangers, all connected end to end by horizontal heat pipes. During off-normal conditions, the reactor will shut itself down and promptly dissipate the decay heat for an indefinite amount of time without any operator intervention or using any control systems, improving safety. The team will conduct modeling and simulations to predict the SCB’s inherent self-regulating ability. It will then fabricate and test several SCB samples to validate the modeling and simulation tools and confirm feasibility of advanced manufacturing techniques. The SCB will be the central component of the team's complete micro reactor concept, a robust product that aims to overcome many common challenges of current nuclear power plants, including complicated plant designs, uncertain construction times, high operating and financing costs, and load following limitations.

Potential Impact:

If successful, developments from MEITNER projects will inform the development of lower cost, safe, and secure advanced nuclear power plants.


Nuclear power plants contribute to grid stability by providing reliable baseload power and are among the most secure facilities in the country.


Nuclear power has low life cycle emissions, making it a key source of clean electricity.


Nuclear power provides high-efficiency electrical generation for the U.S. grid. Reducing plant costs reduces exposure to price volatility.


ARPA-E Program Director:
Dr. Robert Ledoux
Project Contact:
Mr. John Lojek
Press and General Inquiries Email:
Project Contact Email:


Los Alamos National Laboratory
Idaho National Laboratory

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