Ambient office = 106 nanosieverts per hour

Ambient outside = 132 nanosieverts per hour

Soil exposed to rain water = 128 nanosieverts per hour

Mini bella mushroom from Central Market = 83 nanosieverts per hour

Tap water = 65 nanosieverts per hour

Filter water = 56 nanosieverts per hour

Ambient office = 113 nanosieverts per hour

Ambient outside = 119 nanosieverts per hour

Soil exposed to rain water = 119 nanosieverts per hour

Green onion from Central Market = 100 nanosieverts per hour

Tap water = 79 nanosieverts per hour

Filter water = 63 nanosieverts per hour

Dover Sole from Central = 98 nanosieverts per hour

     The safety and efficiency of a large, complex nuclear reactor can be improved by hardware as simple as a tiny sensor that monitors a cooling system. Researchers at the Department of Energy’s Oak Ridge National Laboratory (ORNL) are working to make those basic sensors more accurate by combining them with electronics that can withstand the intense radiation inside a reactor.
     The ORNL research team recently met with high success using a gallium nitride semiconductor for sensor electronics. A transistor made with this material continued with operations near the core of a nuclear reactor operated by research partner The Ohio State University.
     Gallium nitride is a wide-bandgap semiconductor. It had previously been tested against the ionizing radiation encountered when rockets travel through space. Devices that employ wide-bandgap semiconductors can operate at much higher frequencies, temperatures and irradiation rates. However, gallium nitride had not faced the even more intense radiation of neutron bombardment.
     Kyle Reed is a member of the Sensors and Electronics group at ORNL. He is the lead researcher for the transistor research. He said, “We are showing it is great for this neutron environment.”
     This discovery could offer a big boost for equipment monitoring in nuclear facilities. The information collected by sensors provides early warnings about wear and tear on equipment. This allows timely maintenance to avoid broader equipment failures that cause reactor downtime. Currently, this sensing data is processed from a distance. It must travel through yards of cable connected to electronics with silicon-based transistors.
     Reed said, “Our work makes measuring the conditions inside an operating nuclear reactor more robust and accurate. When you have lengthy cables, you end up with a lot of noise, which can interfere with the accuracy of the sensor information. By placing electronics closer to a sensor, you increase its accuracy and precision.” In order to meet that goal, scientists need to develop electronics that can better tolerate radiation.
     Researchers irradiated gallium nitride transistors for three days at temperatures up to one hundred and twenty-five degrees Celsius close to the core of The Ohio State University Research Reactor.
     Reed added, “We fully expected to kill the transistors on the third day, and they survived. The team pushed the transistors all the way to the reactor’s safety threshold which was seven hours at ninety percent power.”
     The gallium nitride transistors were able to withstand at least one hundred times higher accumulated dose of radiation than a standard silicon device, said researcher Dianne Ezell, leader of ORNL’s Nuclear and Extreme Environment Measurements group and a member of the transistor research team.
     She said that the transistor material must be able to survive at least five years, the normal maintenance window, in the pool of a nuclear reactor. The research team exposed the gallium nitride device to days of much higher radiation levels within the core itself. They concluded that the transistors would exceed that requirement.
     This is a critical technical advance as researchers turn from the large-scale existing fleet of nuclear energy plants to microreactors that could generate from tens to hundreds of megawatts of power. These novel reactor designs are still in the development and licensing stage. Their potential portability could allow them to be deployed on the back of a truck to a military or disaster zone.

Ambient office = 130 nanosieverts per hour

Ambient outside = 76 nanosieverts per hour

Soil exposed to rain water = 81 nanosieverts per hour

Blueberry from Central Market = 139 nanosieverts per hour

Tap water = 126 nanosieverts per hour

Filter water = 109 nanosieverts per hour

     Swedish company Kärnfull is a small modular reactor (SMR) project development firm. Kärnfull has formed a strategic partnership with Finnish SMR developer Steady Energy to introduce SMRs for district heating in Sweden.
     The partners said the collaboration “leverages Kärnfull’s innovative financing structures and delivery models to bring Steady Energy’s world-leading district heating reactors to Sweden”.
     Steady Energy was spun out in May 2023 from the VTT Technical Research Centre of Finland. It has previously signed letters of intent for the delivery of up to fifteen LDR-50 reactors to Helsinki’s local utility Helen and Kuopio Energy in eastern Finland. The construction of the first commercial plant is estimated to begin in 2028, with the first unit anticipated to be operational by 2030. Construction of the first SMR pilot plant in Finland will start next year with candidate sites in Helsinki, Kuopio and Lahti.
     The LDR-50 district heating SMR has a thermal output of fifty megawatts. It has been under development at VTT since 2020. The LDR-50 is designed to operate at around one hundred and fifty degrees Celsius and below ten bar (one hundred and forty five psi). The LDR-50 reactor module is composed of two nested pressure vessels, with their intermediate space partially filled with water. When heat removal through the primary heat exchangers is compromised, water in the intermediate space begins to boil. This forms an efficient passive heat transfer route into the reactor pool, the company said. The system does not rely on electricity or any mechanical moving parts. These could fail and prevent the cooling function.
     Kärnfull Next is a fully-owned subsidiary of Kärnfull Future AB. It intends to have the first commercial SMR operational at a new nuclear site in Sweden by the early 2030s.
     Christian Sjölander is the CEO of Kärnfull Next. He said, “We are delighted to collaborate with Steady Energy to bring their sleek, cost-effective solution to. With Steady’s reactor in our portfolio, we complement our electricity-focused Re:Firm SMR program with a new bespoke district heating program called Re:Heat. It will target municipalities in need of sustainable heating solutions.”
     Tommi Nyman is the CEO of Steady Energy. He added, “We are very proud to partner with trailblazers Kärnfull Next. Sweden’s electricity consumption is projected to increase significantly to meet net-zero targets, driven by the electrification of transport and industry. This necessitates corresponding clean heating energy to maintain Sweden’s carbon commitments.”
     According to the partners, Sweden’s district heating consumption totals fifty terawatts per year. Two-thirds of this consumption comes from biomass, with fuel costs rising sharply in recent years. The future of biomass within district heating is debated because it is seen to have more valuable alternative uses. In addition, the combustion of biomass leads to the emission of biogenic greenhouse gases.
     Nyman said, “Heating a large city with biomass requires a pile of logs the size of a football field every single day, with a constant stream of trucks around the clock. It is high time that our societies limit burning wood to heat our homes. By combining our expertise, Steady Energy and Kärnfull Next are poised to bring SMR district heating to Sweden. It will help meet ambitious climate and sustainability goals.”