The Danish nuclear reactor company Seaborg Technologies is currently completing important experiments in collaboration with both experts from Neutron and Muon Source (ISIS) at Oxford (UK) and European Spallation Source (ESS) research centre in Lund in Sweden. The goal is to understand how neutrons in modern reactors behave. The new knowledge should allow Seaborg to optimise their reactor design. The company is aiming for 2025 for having its first reactor online. Seaborg is developing compact thorium-based Molten Salt Reactors (MSRs). 

In the early summer, the company reached an important milestone when one of the salts acting as a neutron moderator was tested. The moderator slows down the neutrons that cause the chain reactions. If the neutrons move too fast, the probability of a fission reaction decreases, so the reactor powers down or stops completely. The experiment at ISIS Neutron and Muon Source is important because it provides verification of how neutrons in Seaborg's moderator behaves.

Co-founder and reactor physicist Dr Esben Klinkby said collaboration with the experts from ISIS and ESS has been “formidable”. He added: “We have obtained extremely accurate measurements from it. The analyses have yet to be finalised, but I can already say, that from looking at the data it seems like a confirmation of our expectations of NaOH's good moderator properties.”

The MSR was initially developed in the US in the 1950s and 1960s but the project was terminated and never commercialised due to heavy technical challenges with the moderator that could not last more than four years in the harsh environment. Seaborg has a proprietary type of liquid moderator also based on molten salt – NaOH (sodium hydroxide), which itself is a powerfully caustic base, often used as a drain cleaner. The NaOH has great properties as a moderator. One advantage with NaOH as a moderator compared with graphite is that the radiation does not wear down the materials over time. As a result, Seaborg’s reactor will last 12 years, without having to refuel or change the moderator during that time.

The lifetime of the reactor is a decisive factor in assessing whether the economy of the molten salt reactors is good or not. For Seaborg, the goal is to become price competitive with fossil energy, for instance, in Southeast Asia, where strong financial growth and geographical conditions make renewable energy unfavourable.

With data from the experiments, researchers from Seaborg and ESS can create a computational model that reveals the degree to which the moderator slows down the neutrons in the reactor. For Seaborg, the experiment is a key enabler for the optimization of the reactor design and an important piece in the regulatory process.

The company is developing an inherently safe 4th generation nuclear Compact Molten Salt Reactor (CMSR) with an essential proprietary moderator. With its uranium-based fluoride fuel salt, the CMSR has several prominent features; it cannot melt down or explode, it cannot release radioactive gasses to air or water, and it cannot be used for nuclear weapons.

The CMSR will be installed on modular power barges, providing clean and affordable electricity worldwide. The power barge design is enabling configurations with two, four, six, or eight CMSRs delivering up to 800 MWe or 2000 MWt. The first power barges will have two reactors installed delivering 2 x 100 MWe for the 24-year lifetime of the power barge. The CMSR Power barge is competitive whether it plugs into the grid in an existing coal port or power production of hydrogen and ammonia.

Seaborg said its goal is to execute a rapid worldwide deployment of the CMSR Power barge via shipyard serial production. The ambitious plan is to bring the first CMSR Power barge into service in 2025. The company was issued a feasibility statement in 2020 for the CMSR reactor by the American Bureau of Shipping. Seaborg is utilising the maritime New Technology Qualification process as a cornerstone in the regulatory licensing process.

Date: Thursday, 02 September 2021
Original article: neimagazine.com/news/newsseaborg-completes-experiments-to-optimise-its-molten-salt-reactor-design-9048040