ANS is committed to advancing, fostering, and promoting the development and application of nuclear sciences and technologies to benefit society.
Explore the many uses for nuclear science and its impact on energy, the environment, healthcare, food, and more.
Division Spotlight
Radiation Protection & Shielding
The Radiation Protection and Shielding Division is developing and promoting radiation protection and shielding aspects of nuclear science and technology — including interaction of nuclear radiation with materials and biological systems, instruments and techniques for the measurement of nuclear radiation fields, and radiation shield design and evaluation.
Meeting Spotlight
2025 ANS Annual Conference
June 15–18, 2025
Chicago, IL|Chicago Marriott Downtown
Standards Program
The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
Latest Magazine Issues
May 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
July 2025
Nuclear Technology
June 2025
Fusion Science and Technology
Latest News
High-temperature plumbing and advanced reactors
The use of nuclear fission power and its role in impacting climate change is hotly debated. Fission advocates argue that short-term solutions would involve the rapid deployment of Gen III+ nuclear reactors, like Vogtle-3 and -4, while long-term climate change impact would rely on the creation and implementation of Gen IV reactors, “inherently safe” reactors that use passive laws of physics and chemistry rather than active controls such as valves and pumps to operate safely. While Gen IV reactors vary in many ways, one thing unites nearly all of them: the use of exotic, high-temperature coolants. These fluids, like molten salts and liquid metals, can enable reactor engineers to design much safer nuclear reactors—ultimately because the boiling point of each fluid is extremely high. Fluids that remain liquid over large temperature ranges can provide good heat transfer through many demanding conditions, all with minimal pressurization. Although the most apparent use for these fluids is advanced fission power, they have the potential to be applied to other power generation sources such as fusion, thermal storage, solar, or high-temperature process heat.1–3
Charles Forsberg, Dean Wang, Eugene Shwageraus, Brian Mays, Geoff Parks, Carolyn Coyle, Maolong Liu
Nuclear Technology | Volume 205 | Number 9 | September 2019 | Pages 1127-1142
Technical Paper | doi.org/10.1080/00295450.2019.1586372
Articles are hosted by Taylor and Francis Online.
The flouride-salt-cooled high-temperature reactor (FHR) uses graphite-matrix coated-particle fuel [the same as high-temperature gas-cooled reactors (HTGRs)] and a clean liquid salt coolant. It delivers heat to the industrial process or the power cycle at temperatures between 600°C and 700°C with average heat delivery temperatures higher than for other reactors. The melting point of the liquid salt coolant is above 450°C. The high minimum temperatures present refueling challenges and require special features to control temperatures, avoiding excessively high temperatures and freezing of the coolant that could impact decay heat cooling systems. This paper describes a preconceptual FHR design that addresses many of these challenges by adopting features from the British advanced gas-cooled reactor (AGR) and alternative decay heat cooling systems. The bases for specific design choices are described.
The AGRs are carbon dioxide–cooled and graphite-moderated reactors that use cylindrical fuel subassemblies with vertical refueling at 650°C, which meets the FHR high-temperature refueling requirements. Fourteen AGRs have operated for many decades. The AGR uses eight cylindrical fuel subassemblies, each 1 m tall coupled axially together by a metal stringer to create a long fuel assembly. The stringer assemblies are in vertical channels in a graphite core that provides neutron moderation. This geometric core design is compatible with an FHR using graphite-matrix coated-particle fuel. The FHR uses a once-through fuel cycle. The design minimizes used nuclear fuel volumes relative to other FHR and HTGR designs. The primary system is inside a secondary liquid salt–filled tank that (1) provides an added heat sink for decay heat, (2) helps to ensure no freezing of primary system salt, and (3) helps to ensure no major fuel failures in a beyond-design-basis accident. The refueling standpipes above each stringer fuel assembly in the AGR core with modifications can be used in an FHR for refueling and can provide efficient heat transfer between the primary system and the secondary liquid salt–filled tank. The passive decay heat removal system uses heat pipes that turn on and off at a preset temperature to avoid overheating the core in a reactor accident and to avoid freezing the salt coolant as decay heat decreases after reactor shutdown.