Thursday, 10 July 2025
Terrestrial Energy and NRG-Pallas are starting the final phase of the graphite irradiation testing programme for Terrestrial’s molten salt reactor at the High Flux Reactor in Petten, the Netherlands.
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NRG-Pallas is providing technical services to support Terrestrial Energy for “in-core” materials testing and development of its Integral Molten Salt Reactor (IMSR) power plant. The testing programme at NRG is designed to confirm the predicted performance of selected graphite grades throughout the seven-year cycle of the IMSR. Its scope simulates IMSR core conditions, encompassing the full range of IMSR operating temperatures and of the neutron flux. The programme aims to enable Terrestrial to select the most suitable graphite grade for use in the IMSR reactor, as well as qualifying graphite for IMSR use.
The company sourced multiple graphite grades from suppliers of nuclear graphite in western markets, including the USA, to commence the test programme in November 2020.
“Comprehensive irradiation tests are essential for advanced reactor development and reactor licensing, as they validate the performance of critical materials under actual operating conditions,” said Terrestrial Energy CEO Simon Irish. “Our pioneering work with NRG-Pallas is providing the data needed to make our final graphite grade selection for the IMSR, marking another important milestone in our supply chain development.
“NRG-Pallas’ technical expertise and research capabilities are unparalleled in the world of advanced reactor development, and this work will be a major step toward Terrestrial Energy’s goal of achieving early fleet deployment.”
Arjan Vreeling, manager of R&D Nuclear Fuels and Materials at NRG-Pallas added: “NRG-Pallas is committed to leveraging its test reactor and research capabilities to support advanced reactor development. We have been collaborating with Terrestrial Energy now for five years and are delighted to be moving to the final stage of in-core irradiation testing of IMSR graphites, the first developer to commence such testing.”
Terrestrial’s IMSR is a 4th generation reactor that uses molten salt as both fuel and coolant, with integrated components, which can supply heat directly to industrial facilities or use it to generate electrical power. The use of molten salt as both fuel and coolant also enables passive, or inherent, safety features to be built into the reactor design. The design integrates the primary reactor components, including the graphite moderator, into a sealed and replaceable reactor core unit with an operating lifetime of seven years. The reactor uses about 125 tonnes of graphite as a neutron moderator.
