Objective: Design an irradiation capsule compatible with multiple material test reactors capable of housing a variety of in-core mechanical testing instrumentation. Generate high-priority, stress relaxation data for stainless-steel-based materials.

Facilities: MITR (United States) in Phase I and HFR (the Netherlands) in Phase II 

Core Group: INL, NRC, EPRI (United States), CEA (France), NRG (Netherlands), JRC (European Commission), and CVR (Czechia)

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INCREASE is aimed at developing the capability to perform a variety of in-core mechanical testing measurements. A primary expense in any reactor irradiation experiment stems from the detailed neutronics, thermal-hydraulic, and structural analyses to meet the safety basis requirements for the reactor. Unlike a typical reactor experiment, in which design and analysis are limited to a single specific experiment, INCREASE will realise a design and analysis process that encompases the requirements of multiple material test reactors. Future experiments can utilise the prior design and analysis, independent of the structural material and even the mechanical testing apparatuses employed. 

The JEEP is organised in two phases. Phase I will be conducted in the MITR and produce critical stress relaxation data on stainless steel (SS) materials that are used for baffle bolts and other key LWR internals components to support aging management during the long-term operation of existing plants. Phase II supplements Phase I activities by fulfilling additional data needs. Phase II will be conducted in the HFR. Phase II includes evaluation of the same 304L SS material being tested in Phase I: HFR and MITR have very different spectra and fluxes and a direct comparison will determine the sensitivity of stress relaxation properties to these effects.