Benefiel, Bradley C | Search NASA

DOE OSTI2023

Development Of A Photonic Doppler Velocimeter To Verify A Fabry-Perot Velocimeter

The laser shock system uses acoustic shockwaves to measure the interface strength of newly designed nuclear fuel plates. The quantitative measurement of interface strength will help understand fuel performance during irradiation. The laser shock technique imparts laser energy into a plate that then creates an acoustic shockwave. The amount of energy in the plate is proportional to the surface velocities measured on the back side of the plate. An accurate determination of surface velocity will enable better fuel performance predictions. The focus of this paper is on the implementation of a Photonic Doppler Velocimeter to corroborate the Fabry-Perot measurements from the laser shock system. Currently, a Fabry-Perot velocimeter takes the velocity measurements that are converted in stress. We have designed and implemented a Photonic Doppler Velocimeter to corroborate the Fabry-Perot measurements, which we discuss here along with implementing the short time fast Fourier transform to demodulate the heterodyne beat frequency into velocities. The Photonic Doppler Velocimeter has successfully corroborated the Fabry-Perot measurements.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2020

Remote Fiber Based Velocimeter For Interface Strength Measurements

The understanding of the performance of nuclear reactor plate fuels is essential when developing new fuel systems. The condition of pre and post irradiated plate fuels must be characterized effectively and efficiently prior to irradiation and then post irradiation within a high rad environment. The post characterization work must be performed remotely and in an environment hostile to instrumentation. Laser based characterization methods provide the capability to be remote and robust within a hot-cell environment. Laser based characterization can provide high spatial resolution appropriate for scanning and imaging large areas. The INL is currently developing a laser shock system for Post Irradiation Examination (PIE) station for use in the Hot Fuel Examination Facility (HFEF) at the INL. The laser shock system is designed to characterize fuel to cladding and cladding to cladding interface strength. The laser shock-technique induces large amplitude shock waves to mechanically characterize interfaces such as the fuel-clad interface. The shock wave propagates as a compressional wave through the fuel plate to the free (unconfined) backside surface and is reflected back through the test plate as a rarefaction (tensile) wave. This rarefaction wave is the physical mechanism that produces internal delamination failure. The focus or this paper is on the accurate measurement of surface velocity to quantify the amount of energy traveling through the interfaces to the back surface of the fuel plate. The original fiber based velocimeter design was biased by parasitic back reflections. This paper will discuss the discovery of the back-reflection issue and the design changes to resolve the issue. Supporting data will be presented.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗