Temperature-Compensated Tuning Fork Sensor for Internal Pressure Monitoring of Spent Fuel Canisters

Measuring internal pressure is crucial in industrial applications, including non-destructive evaluation (NDE) of spent fuel canisters. This study utilized a double-ended tuning fork (DETF) to measure internal pressure by detecting changes in hoop strain on the canister’s surface, which affects the tuning fork’s resonance frequency. Finite element simulations were conducted to analyze strain distribution and sensor response, followed by calibration and temperature compensation experiments. The sensor outperformed other strain sensors such as strain gauges and surface acoustic wave sensors, achieving a minimum measurable strain of $0.0679~\mu $ and pressure of 0.3 kPa, with a pressure sensitivity of 0.6221 kHz/MPa (35286 ppm/MPa). The study highlights the effectiveness of DETF sensors for precise pressure measurement, demonstrating their suitability for use in harsh environments using the temperature compensation technique demonstrated in this work. The sensor’s performance highlights its potential for widespread adoption in applications where accurate pressure measurement is critical.

I. Introduction

Securing nuclear fuel rods after their operational lifespan, termed as spent fuel, is an important concern within the nuclear industry. While these rods are no longer used for energy generation, they are still radioactive. Presently, canisters stand as the favored method for the safe storage of spent fuel rods [1], [2]. The internal pressure of the canisters can fluctuate due to factors such as helium gas leakage, structural issues like cladding degradation and corrosion, the presence of residual water, the formation of oxygen and hydrogen, and temperature variations [3], [4], [5]. Therefore, monitoring the internal pressure allows for early detection and warning when pressure exceeds a predefined threshold to conduct timely maintenance, prevent potential hazards, and maintain system integrity. However, conventional pressure and temperature sensors encounter significant hurdles due to the hostile environment. Drilling into the canister is prohibited, and the extreme temperature and radiation within can nullify sensor efficacy. An effective pressure sensing approach must tackle challenges such as sensor power, data acquisition, extended deployment, high temperatures, radiation, and accessibility postinstallation amidst harsh conditions. Internal pressure measurement has broader applications, promoting safety in pressurized systems by tracking pressure in real-time and issuing warnings when limits are reached.