Glass cell provides glimpse inside molten salt reactors

06 August 2024

A custom-made glass test cell created by Oak Ridge National Laboratory (ORNL) has enabled researchers to observe how gases behave inside a molten salt reactor and investigate the complex chemistry that can occur in the molten salt solution.

Scientific glassblower Carlos Rodriguez Flores is seen fabricating the glass cell (Image: ORNL)

Some of the reactors that are currently being designed will operate on liquid fuel, where the fissile materials are directly dissolved in a molten salt solution that also acts as the reactor's coolant. But nuclear and chemical reactions can result in gases that bubble out of the molten salt, which can impact reactor neutronics and thermal hydraulic performance.

The glass test cell fabricated to visualise noble gas behaviour in a molten salt column (Image: ORNL)

To help investigate these effects, ORNL researchers designed and developed a customised glass test cell that can hold up to a litre of liquid molten salt. They injected small helium and krypton bubbles into the cell to observe how they moved through the column of molten salt, and were able to measure gas bubble velocity, size distribution, and interactions with neighbouring bubbles using high-speed cameras. The insights provided from the experiment will be used to help improve and validate simulation tools for molten salt-fuelled systems.

"Understanding gas generation and transport in molten salt reactors is essential to optimising their performance and safety," said Daniel Orea, ORNL lead R&D associate. "This unique glass test cell allows us to overcome certain engineering challenges caused by the high temperature and composition of salt and its two-phase liquid glass system."

The research project was supported through the US Department of Energy's Molten Salt Reactor Program.

MobileNuclear and PTT announce collaboration

06 August 2024

MobileNuclear Energy (MNE) is to collaborate with Peregrine Turbine Technologies (PTT) to integrate its MN-1 Mobile Microreactor system with PTT's supercritical carbon dioxide energy conversion system and advanced heat exchanger technologies.

The MN-1 system would fit in a shipping container (Image: MobileNuclear)

Virginia-based MNE's mission is to develop and deploy the first truly mobile, safe, sustainable, and affordable nuclear microreactor to provide the military and other government agencies with responsive, durable, and modular energy generation capability. MN-1 is a nuclear microreactor intentionally designed for mobility. Its compact reactor core and design features are optimised for small size, light weight, efficient energy production, affordability and safety. The MN-1 is a modular system, transportable by air, land or sea, and can optionally be integrated to operate in transit to provide power for propulsion systems, directed energy weapons, or other high-power "on the move" applications.

MNE and PTT's Nuclear Energy System subsidiary (PTT NES) plan to collaborate on the integration of PTT NES' patented supercritical carbon dioxide (sCO2) energy conversion systems, thermally compliant heat exchanger technologies, and high temperature helium blower and magnetic torque coupling with MNE's MN-1.

PTT NES's sCO2 system is essentially a closed loop heat engine and is fuel agnostic, meaning that it can operate on any high-grade heat source such as nuclear and concentrated solar, as well as on all air combustible fuels including sustainable biomass, biogas, refuse-derived fuels and natural gas.

The core power module - which would generate 1 MWt and 350 kWe - is equivalent in size to a standard 20-foot (6-metre) shipping container, populated with the microreactor and PTT's sCO2 turbine-generator as baseline capability. Add-on modules can seamlessly integrate with the power module to provide atmospheric water generation, hydrogen-based fuel production, heating and cooling, and other mission-tailored capabilities.

PTT's energy conversion system - successfully developed and demonstrated in collaboration with Sandia National Laboratories' Brayton Laboratory - is tailored for advanced nuclear reactors. It offers enhanced efficiency compared with traditional steam systems and air Brayton conversion systems, with a significantly reduced footprint. PTT says its systems have 1.5 times the efficiency of steam with less than one-third of the footprint, and over three times the efficiency of air Brayton conversion systems.

"MobileNuclear is excited to partner with PTT NES to integrate their sCO2 systems with our mobile microreactor," said MNE CEO Chris Pehrson. "It's a perfect marriage that will deliver the energy capacity that our customers need while maintaining the mobility that defines our microreactor system."

PTT NES CEO and Chief Technology Officer David Stapp added: "Advanced nuclear married to advanced sCO2 power conversion technology is a game-changer for large, distributed energy markets, both commercial and military. Peregrine's technology is right-sized to match with MobileNuclear's advanced reactor technology. The combination delivers breakthrough performance and capability that is unmatched. We are excited to team with this capable company."

PTT, based in Wiscasset, Maine, was formed in April 2012 and is focused on the development and deployment of advanced sCO2 turbine power generation, energy storage and propulsion systems.

In July last year, the company announced it had established a new subsidiary, PTT Nuclear Energy Systems, after it had "identified significant potential and opportunity for its breakthrough energy conversion technologies in the accelerating VSMR (very small modular reactor) and MMR (micro modular reactor) programmes (350 kW- 10 MW), and a clear intermediate-term opportunity in the SMR (small modular reactor) 30 MW to 100 MW class range". At the time, PTT said it was "working to field a family of its proprietary modular sCO2 energy conversions systems with initial capabilities ranging from 350 kW to 10 MW".

In April this year, Ultra Safe Nuclear Corporation announced it is to collaborate with PTT to integrate its Pylon microreactor with PTT's sCO2 energy conversion system and advanced heat exchanger technologies.

Sweden, USA agree to nuclear cooperation

02 August 2024

Sweden and the USA have signed a memorandum of understanding aimed at pursuing cooperation in industrial collaboration, technology development, and research and innovation in technologies related to nuclear energy for peaceful purposes.

Granholm (left) and Busch (right) signing the MoU (Image: @BuschEbba / X)

The MoU was signed by Sweden's Minister for Energy, Business and Industry Ebba Busch and US Secretary of Energy Jennifer Granholm in Washington, DC, on 1 August.

The partners said the agreement will "provide a framework for the participants to enhance overall cooperation between their respective government bodies, enterprises, and research institutions in policies and research and development activities relating to civil nuclear energy".

The MoU means that Sweden and the USA will exchange experience on issues related to policy, research and innovation related to supply chains, financing models, skills supply and development of advanced nuclear fuel.

Specific technological areas for cooperation include: nuclear power reactors, including advanced reactors such as small modular reactors; advanced nuclear fuel development; nuclear waste management; and nuclear safety and security.

The partners plan to exchange publicly available scientific and technical information, as well as share information and experiences on policies and regulations, and share and develop best practices on security of energy supply and demand for nuclear energy technologies. They will facilitate contacts between relevant public and private sector entities in both countries and encourage and promote dialogue, networking, and cooperation at all levels among government representatives, government bodies, enterprises along the value chain and research institutions through visits, workshops, meetings and other activities.

"Sweden and the United States will now cooperate on nuclear power," Busch said. "This is good for Sweden, the United States, the labour market and competitiveness. Our countries enjoy longstanding and good relations and I look forward to strengthening our cooperation and knowledge exchange in the area of nuclear power."

"Today's agreement further strengthens US cooperation with Sweden to diversify our supply chains and nuclear fuel supply, deploy new reactors, and find solutions to the management of our spent nuclear fuel," Granholm said in a post on X.

In October 2022, Sweden's incoming centre-right coalition government adopted a positive stance towards nuclear energy. In November last year, it unveiled a roadmap which envisages the construction of new nuclear generating capacity equivalent to at least two large-scale reactors by 2035, with up to ten new large-scale reactors coming online by 2045.