Molten-salt reactor
Increased research into Generation IV reactor designs renewed interest in the 21st century with multiple nations starting projects.
FHR retains the safety and cost advantages of a low-pressure, high-temperature coolant, also shared by liquid metal cooled reactors.
Chlorine, unlike fluorine, must be purified to isolate the heavier stable isotope, 37Cl, thus reducing production of sulfur tetrachloride that occurs when 35Cl absorbs a neutron to become 36Cl, then degrades by beta decay to 36S.
In some thorium breeding scenarios, the intermediate product protactinium 233Pa would be removed from the reactor and allowed to decay into highly pure 233U, an attractive bomb-making material.
Because 232U has a short half-life and its decay chain contains hard gamma emitters, it makes the isotopic mix of uranium less attractive for bomb-making.
Variations include: The molten-salt fast reactor (MSFR) is a proposed design with the fuel dissolved in a fluoride salt coolant.
They have been studied for almost a decade, mainly by calculations and determination of basic physical and chemical properties in the European Union and Russian Federation.
The core's shape is a compact cylinder with a height to diameter ratio of 1 where liquid fluoride fuel salt flows from the bottom to the top.
[28] MSFRs contain an emergency draining system that is triggered and achieved by redundant and reliable devices such as detection and opening technology.
[citation needed] The LS-VHTR can work at very high temperatures (the boiling point of most molten salt candidates is >1400 °C); low-pressure cooling that can be used to match hydrogen production facility conditions (most thermochemical cycles require temperatures in excess of 750 °C); better electric conversion efficiency than a helium-cooled VHTR operating in similar conditions; passive safety systems and better retention of fission products in the event of an accident.
Private companies from Japan, Russia, Australia and the United States, and the Chinese government, have expressed interest in developing this technology.
Pumping of the fuel salt, and all the corrosion/deposition/maintenance/containment issues arising from circulating a highly radioactive, hot and chemically complex fluid, are no longer required.
The MSR program closed down in the early 1970s in favor of the liquid metal fast-breeder reactor (LMFBR),[37] after which research stagnated in the United States.
Engel et al. 1980 said the project "examined the conceptual feasibility of a molten-salt power reactor fueled with denatured uranium-235 (i.e. with low-enriched uranium) and operated with a minimum of chemical processing."
[citation needed] The UK's Atomic Energy Research Establishment (AERE) was developing an alternative MSR design across its National Laboratories at Harwell, Culham, Risley and Winfrith.
It included theoretical and experimental studies, particularly the investigation of mechanical, corrosion and radiation properties of the molten salt container materials.
[38][49] Terrestrial Energy, a Canadian-based company, is developing a DMSR design called the Integral Molten Salt Reactor (IMSR).
The main design features include neutron moderation from graphite, fueling with low-enriched uranium and a compact and replaceable Core-unit.
[50] Terrestrial completed the first phase of a prelicensing review by the Canadian Nuclear Safety Commission in 2017, which provided a regulatory opinion that the design features are generally safe enough to eventually obtain a license to construct the reactor.
[56][57] China then accelerated its program to build two 12 MW reactors underground at Wuwei research facilities by 2020,[58] beginning with the 2 megawatt TMSR-LF1 prototype.
[65] In 2022, Shanghai Institute of Applied Physics (SINAP) was given approval by the Ministry of Ecology and Environment to commission an experimental thorium-powered MSR.
The Copenhagen Atomics Waste Burner is a single-fluid, heavy water moderated, fluoride-based, thermal spectrum and autonomously controlled molten-salt reactor.
The CMSR is a high temperature, single salt, thermal MSR designed to go critical on commercially available low enriched uranium.
[75] The German Institute for Solid State Nuclear Physics in Berlin has proposed the dual fluid reactor as a concept for a fast breeder lead-cooled MSR.
[citation needed] In 2015, Indian researchers published a MSR design,[76] as an alternative path to thorium-based reactors, according to India's three-stage nuclear power programme.
[84][85] The Alvin Weinberg Foundation is a British non-profit organization founded in 2011, dedicated to raising awareness about the potential of thorium energy and LFTR.
In 2011, Sorensen founded Flibe Energy,[38] a company aimed at developing 20–50 MW LFTR reactor designs to power military bases.
[32][93][94][95] Transatomic Power pursued what it termed a waste-annihilating molten-salt reactor (WAMSR), intended to consume existing spent nuclear fuel,[96] from 2011 until ceasing operation in 2018 and open-sourcing their research.
[97][98] In January 2016, the United States Department of Energy announced a $80m award fund to develop Generation IV reactor designs.
[100] In February 2024 DOE and Kairos Power signed a $303M Technology Investment Agreement to support the design, construction, and commissioning of the reactor.
