# Is the NEA's INCREASE-I Irradiation System Ready to Deploy at MIT's Reactor?

Yes. The OECD Nuclear Energy Agency's INCREASE-I experimental rig has completed fabrication, qualification, and verification and is ready for deployment at the Massachusetts Institute of Technology Reactor (MITR). The system — eight capsules in total, four active and four passive — will conduct in-core stress-relaxation tests on stainless steel under simultaneous neutron irradiation, high temperatures, and mechanical stress. The data generated is intended to improve predictive models of structural material performance in light water reactors, directly supporting both current fleet life extension and advanced reactor design qualification.

This is not a routine materials coupon drop. The INCREASE-I rig uses what the OECD NEA describes as a "generalized design and analysis framework" specifically engineered for reuse across multiple international research reactors — the first time such a modular, multi-facility architecture has been applied to an in-core mechanical testing program of this kind under the FIDES-II framework.

The partnership behind the project includes 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.

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## What Is INCREASE-I and Why Does It Matter?

INCREASE-I — In-Core Real-Time Mechanical Testing of Structural Materials, Phase I — is an OECD NEA project launched under the Second Framework for Irradiation Experiments, known as FIDES-II. That overarching framework is designed to facilitate shared use of international irradiation facilities and collective expertise among OECD NEA member countries.

The specific focus of INCREASE-I is stainless steel, a primary structural material in LWR internals. The core challenge this experiment addresses is well-known to reactor engineers: in-service structural components are subjected not just to neutron bombardment or heat in isolation, but to all three stressors simultaneously. Conventional post-irradiation examination gives you the end state; it cannot capture real-time mechanical response during irradiation. INCREASE-I's active capsules are designed to provide exactly that — in situ stress-relaxation measurements while the irradiation event is occurring.

The passive capsules serve a complementary role. In addition to containing stress-relaxation specimens, they carry static specimens for post-irradiation microstructural characterization, along with passive temperature sensors and passive neutron fluence monitors. Together, the active and passive capsule sets create a dataset that links real-time mechanical behavior to microstructural evolution — the kind of combined evidence base that regulatory bodies and materials modelers need to validate predictive codes.

According to the OECD NEA, the qualification program that brought the system to deployment readiness included instrumentation verification, weld development and qualification, leak testing, autoclave testing, sensor validation, and bench-scale functional testing of critical components. The NEA characterizes these activities as having "significantly reduced technical risk and demonstrated readiness for deployment."

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## The Modular Architecture Is the Architectural Bet Worth Watching

The design choice that distinguishes INCREASE-I from prior irradiation programs is the intentional modularity of the capsule architecture. The OECD NEA states explicitly that the capsule "was intentionally developed using a modular and adaptable architecture to facilitate deployment in multiple international research reactors."

That framing points directly at INCREASE-II, the planned second phase of the program. INCREASE-II will adapt the INCREASE-I design to the High Flux Reactor in Petten, the Netherlands, operated by NRG PALLAS. The stated scientific objective of that transition is to "investigate the effects of differences in neutron spectra and fluxes" — meaning the same material under similar stress conditions will be tested in two reactors with meaningfully different neutron environments, enabling spectrum-dependent effects to be isolated. That comparative dataset would be difficult to obtain any other way, and the modular design makes it achievable without a full redesign cycle.

From a broader industry perspective, the FIDES-II model — shared facilities, shared costs, shared data across member nations — represents a template that advanced reactor developers should be watching. Irradiation campaign costs and scheduling delays at national facilities have historically been one of the underappreciated bottlenecks in reactor materials qualification. A framework that distributes that burden internationally while standardizing methodology could materially accelerate qualification timelines for new cladding materials, core internals, and structural components in advanced designs.

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## FIDES-II's Broader Portfolio: HERA Delivers First Test Data

INCREASE-I is not FIDES-II's only active project. The OECD NEA previously announced that the High Burnup Experiments in Reactivity Initiated Accident project — HERA — completed its first test on a commercially irradiated fuel segment. HERA is focused on understanding LWR fuel behavior at high [fuel burnup](https://smrintel.com/glossary/burnup) under reactivity-initiated accident conditions.

The data from HERA's first test is expected to inform new fuel designs capable of extending the operational life of the existing commercial reactor fleet. Taken together, INCREASE-I and HERA represent two complementary research vectors under FIDES-II: one targeting structural material integrity, the other targeting fuel performance at operational limits.

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## Skeptical Read: What the Deployment Announcement Doesn't Tell Us

The OECD NEA announcement confirms readiness for deployment but does not specify a deployment date, irradiation campaign duration, or the timeline for data publication. "Ready to deploy" and "deployed" are meaningfully different milestones in research reactor scheduling, where beam time and facility availability introduce their own lead times.

The partnership list is broad and prestigious, but multi-organization international projects carry coordination complexity that can extend timelines. The INCREASE-II transition to the High Flux Reactor in Petten depends on INCREASE-I generating sufficient data at MITR first — and that sequencing creates a dependency chain that is not yet resolved.

Additionally, the announcement does not specify which grades of stainless steel are under test, nor the specific stress-relaxation regimes being targeted. For reactor designers trying to assess whether this data will be directly applicable to their material specifications, that detail matters and will only be available once results are published.

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## Key Takeaways

- The INCREASE-I experimental rig is fully fabricated, qualified, and verified — eight capsules (four active, four passive) are ready for deployment at MIT's research reactor.
- Active capsules will capture real-time, in situ stress-relaxation data on stainless steel during neutron irradiation — a capability conventional post-irradiation examination cannot provide.
- The modular capsule architecture is designed for reuse across multiple research reactors, with INCREASE-II planned for deployment at the High Flux Reactor in Petten under NRG PALLAS.
- The project involves the U.S. DOE, Idaho National Laboratory, NRC, EPRI, the French CEA, NRG PALLAS, the European Commission's Joint Research Center, and the Czech Research Centre Řež.
- FIDES-II's multi-facility, multi-nation model is an emerging template for distributing irradiation campaign costs and accelerating materials qualification — relevant to both fleet life extension and advanced reactor development.
- No deployment date, campaign duration, or data publication timeline has been disclosed.

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## Frequently Asked Questions

**What is the INCREASE-I project?**
INCREASE-I (In-Core Real-Time Mechanical Testing of Structural Materials, Phase I) is an OECD Nuclear Energy Agency project under the FIDES-II framework. It uses a newly developed irradiation rig to conduct in-core stress-relaxation tests on stainless steel at the MIT Reactor, generating data on material behavior under simultaneous neutron irradiation, high temperatures, and mechanical stress.

**What reactor will INCREASE-I be deployed in?**
The initial deployment is at the Massachusetts Institute of Technology Reactor (MITR). Phase II of the program — INCREASE-II — is planned for the High Flux Reactor in Petten, the Netherlands, to compare material behavior across different neutron spectra and flux levels.

**Why does in situ mechanical testing during irradiation matter?**
Conventional irradiation experiments measure material properties before and after exposure. In situ testing captures real-time mechanical response during irradiation, enabling researchers to track how neutron damage, temperature, and stress interact dynamically — data critical for validating predictive material performance models used in reactor design and licensing.

**Who is funding and participating in INCREASE-I?**
The project involves 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.

**How does INCREASE-I relate to fleet life extension and advanced reactors?**
The stress-relaxation and microstructural data generated will support improvements to structural materials used in nuclear systems and help validate predictive models — directly applicable to extending the service life of operating LWR internals and to qualifying structural materials for advanced reactor designs.