NSUF 25-5218: Elevated temperature gamma irradiation of optical fibers sensors for spent nuclear fuel dry cask storage system canister structural health monitoring applications

Methods to Be Employed The project will assess and demonstrate feasibility for deployment of silica based optical fiber sensors for structural health monitoring of stainless-steel canister surfaces utilized in spent fuel dry cask storage systems. In-situ optical monitoring of optical fibers and sensors will be performed during elevated temperature (T=200C) and gamma irradiation with total dosage representative of spent fuel canister deployments. Optical fiber sensors will include Fiber Bragg Gratings inscribed through high temperature stable femtosecond laser processing and Multimode Interferometer sensors. Sandia National Laboratory Gamma Irradiation Facility (GIF) will be utilized for conduct of experiments and duplicates of optical fibers and sensors will be included for sampling over a range of total exposure times. Optical transmission responses will also be characterized before and after irradiation, in addition to in-situ monitoring. During irradiation, optical fibers and sensors will be mounted on the surface of small diameter (2.5”) stainless steel hollow cylinders using two different methods, namely (1) Kapton tape and (2) a polymer adhesion layer TDA Research provided Macropoxy 646N. Both adhesion materials have been utilized previously for experiments within the GIF and the latter has been investigated as potential corrosion mitigation coatings for stainless steel. Post-irradiation will include (1) digital photographs and (2) optical transmission of sensors and devices, and (3) optical microscopy of fiber coating and cladding as well as adhesion integrity.

Potential Impact to State-of-the-Knowledge Through prior experimental investigations, pure silica core and F-doped silica clad fibers have been identified as the superior choice commercially available for gamma irradiation. Proposed experiments build upon past work by specifically testing this class of fibers, and sensor devices constructed therefrom, under elevated temperatures and total dosages relevant for the surface of canisters in dry cask storage systems. Combined experiments investigating both silica fibers and sensor devices, any sources of observed instabilities can be differentiated between underlying instability of optical fiber materials or the fabricated device construction. At the conclusion of the experiments, potential for silica-based fibers to be deployed on the surface of dry cask storage systems for structural health monitoring applications will be assessed and any technical challenges that require mitigation prior to future commercial deployment will be clarified.

Expected Period of Performance The expected period of performance will be a continuous, dedicated irradiation experiment conducted sometime during the 2025 cycle with a maximum time of 80 hours (~2 weeks).

Anticipated Scientific Outcome from this Experiment The proposed experiments will yield numerous insights regarding the potential for silica fiber deployment on spent fuel canister surfaces for in-situ monitoring. Through in-situ monitoring of silica fibers, any measured instability of the silica fiber material can be quantified and correlated to irradiation time and dosage at a fixed temperature representative of canister applications. By in-situ monitoring of selected silica fiber devices in parallel, the stability of additional processing required for device fabrication can also be benchmarked and clarified, such as the femtosecond laser inscribed Fiber Bragg Grating (FBG) sensors and the junction between single and multimode fibers in Multimode Interferometer (MMI) sensors.

Papildoma informacija

Laukas	Reikšmė
Award Announced Date	2025-08-06T10:05:53.72
Awarded Institution	University of Pittsburgh
Facility Tech Lead	Christopher Smyth
Irradiation Facility	Gamma Irradiation Facility
PI	Paul Ohodnicki
PI Email	[email protected]
Project Type	RTE
RTE Number	None