The full-scale precast concrete structure used for radiation testing at Kairos Power’s Reactor Demonstration Campus in Oak Ridge, Tenn. (Photo: Kairos Power)
Kairos Power has completed shielded radiation performance testing on a full-scale precast concrete structure at the company’s Reactor Demonstration Campus in Oak Ridge, Tenn., involving the use of an iridium-192 source to measure the movement of radiation through the concrete’s walls, joints, and seams. Kairos expects the results to contribute to schedule and cost estimates for its planned commercial power plants.
Testing method: The testing involved construction of a 26-foot-tall shielding structure made out of precast concrete elements, like those used to quickly build tunnels, bridges, and other types of common infrastructure. The elements were connected with various types of joint designs, some grouted and others not, to evaluate the different designs’ impact on radiation shielding.
After the shielding structure was completed, Kairos Power worked with two companies—TechCorr and Barnard Construction—to test whether the modular construction provided the same level of radiation protection as would a solid concrete wall. A sealed iridium-192 radiation source—as is frequently used in industrial inspections and medical treatments—was directed at the structure to see if any of the radiation passed through the gaps, seams, or imperfections.
The test results indicated that the structure performed well, with radiation measurements closely matching predictions made by engineering models. Kairos Power principal engineer John Perry explained, “One of the major drivers of schedule for precast concrete is grout, which can ultimately increase the cost for the project. If we can evaluate that certain joints don’t need to be grouted or are successful from a radiation perspective and a shielding perspective, that’s a boon for our company.”
Hermes test reactors: Kairos said that further testing will be performed to better quantify the results—and to directly inform the design and construction of the Hermes low-power demonstration reactor, which is under construction at the Oak Ridge campus.
Hermes was the first non–light water reactor to receive a construction permit from the Nuclear Regulatory Commission, which was granted in December 2023. The 35-MWt fluoride salt–cooled, high-temperature reactor is intended to demonstrate Kairos’s nuclear systems, manufacturing capabilities, supply chain, and licensing certainty. Both Hermes and the company’s Hermes 2 test reactor, which is also planned for construction at Oak Ridge, will use TRISO fuel pebbles and FLiBe molten fluoride salt coolant.
Hermes and Hermes 2 are key parts of Kairos’s “iterative pathway” to eventual commercialization of a 150-MWe fluoride salt–cooled, high-temperature reactor, known as KP-FHR.
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