NEA irradiation system ready to deploy at MITR

A new irradiation experimental system is ready for deployment. The rig, which is the focus of In-Core Real-Time Mechanical Testing of Structural Materials (INCREASE-I), an OECD Nuclear Energy Agency project, will be used to conduct stress-relaxation tests of stainless steel at the Massachusetts Institute of Technology Reactor (MITR), according to the OECD NEA.

INCREASE-I was launched under the Second Framework for Irradiation Experiments (FIDES-II), which is facilitating the use of international irradiation facilities and collective experience for OECD NEA member countries. It is the first phase of a two-phase program focused on testing structural materials for light water reactors.

According to a 2025 OECD NEA report on FIDES-II, INCREASE-I is focused on testing stainless steel materials, and it will lay the groundwork for INCREASE-II, which will adapt the design to the High Flux Reactor in Petten, the Netherlands, to "investigate the effects of differences in neutron spectra and fluxes."

"Unlike conventional reactor experiments, where the design and analysis are tailored to a single reactor and a specific experiment, INCREASE-I employs a generalized design and analysis framework that can be adapted to the requirements of testing multiple materials," according to the OECD NEA. "The INCREASE-I capsule was intentionally developed using a modular and adaptable architecture to facilitate deployment in multiple international research reactors."

The experiment is expected to generate unique data on how materials behave when exposed simultaneously to neutron irradiation, high temperatures, and mechanical stress that supports improvements to structural materials used in nuclear systems and validating predictive models of material performance.

Over several years, researchers completed fabrication, qualification, and verification of both active and passive irradiation capsules-four of each-creating a fully integrated experimental system. The assembly is now ready to be deployed at MITR.

The active capsules will provide in situ stress relaxation measurements during irradiation. The passive irradiation capsules also contain stress relaxation specimens as well as static specimens for postirradiation microstructural characterization. They incorporate passive temperature sensors and passive neutron fluence monitors.

According to the OECD NEA, "These efforts included instrumentation verification, weld development and qualification, leak testing, autoclave testing, sensor validation and bench-scale functional testing of critical components. Completing these activities significantly reduced technical risk and demonstrated readiness for deployment."

International partnership: The project brought together a range of organizations from different countries, including the U.S. Department of Energy, Idaho National Laboratory, the U.S. Nuclear Regulatory Commission, the Electric Power Research Institute, the French Alternative Energies and Atomic Energy Commission, NRG PALLAS, the European Commission's Joint Research Center, and the Czech Research Centre Řež.

More from FIDES-II: Last year, the OECD NEA announced that the first test had been completed for another FIDES-II project called High Burnup Experiments in Reactivity Initiated Accident (HERA).

HERA's aim is to understand the performance of LWR fuel at high burnup under reactivity-initiated accidents (RIA), and the first test was conducted on a commercially irradiated fuel segment. The data from HERA is expected to provide information for new fuel designs that could extend the life of the current fleet of commercial reactors around the world.