Development of ultrasonic waveguide techniques for under-sodium viewing

Ultrasonic Imaging in Hot Liquid Sodium Using a Plate-Type Ultrasonic Waveguide Sensor

“…Therefore, immersion sensors may have a limited lifetime in such a hostile liquid-sodium environment (Recently, electromagnetic acoustic transducer phased arrays have been developed to overcome such drawbacks of classical piezoelectric sensors in sodium environment [10]). On the other hand, waveguide sensor technology [11][12][13] uses an ultrasonic transducer in a relatively cold region, i.e., outside the reactor vessel (above the reactor head), and transmits ultrasonic waves to the target using a long waveguide, part of which is submerged in hot liquid sodium. In this configuration, the transducer can perform with better sustainability and it has been possible to inspect the space between the bottom of the upper internal structure (UIS) and the top of the core during the refueling process without thermal and radiation damage.…”

High temperature ultrasonic immersion measurements using a BS-PT based piezoelectric transducer without a delay line

“…Past experience, specifically, with regard to long term maintenance experience from the French Phenix reactors has underlined the need to provide effective and reliable inspection of components [3]. The use of liquid metal (sodium) coolants in NPP provide for a low operating pressure and a high-power density although there are major challenges with regards to in-service inspection (ISI) and repair [4][5]. The opacity and electrical conductivity of a sodium coolant makes optical and electromagnetic techniques less effective for ISI of NPP components.…”

“…During the operation of a sodium fast reactor various system components can be displaced, for example, the head of a Fuel SubAssembly (FSA) may undergo a lateral shift from its original position due to the fast neutron induced damage on its structural material. Visualization based on ultrasonic imaging has been found feasible to guide robotic arm motion and for the inspection of components [5][6][7][8]. This series of needs has resulted in development of various under sodium measurement and viewing capabilities.…”

“…For high temperature and extended operation two approaches to design have been investigated: a) waveguide based transducer and b) fully immersion transducer. A waveguide acts as a buffer rod and isolates the transducer from the high temperature and sodium environment [5,19,25,26]. Recently, a flexible or re-configurable waveguide concept has been developed for temperature sensing applications [32].…”

Analysis of high temperature effects on piezoelectric based ultrasonic transducers

“…Past experience, specifically, with regard to long term maintenance of the French Phenix reactors, has underlined the need to provide effective and reliable inspection of nuclear components [CEA, (2012)]. The use of liquid sodium coolant in NPP enable a low operating pressure and a high-power density although there are major challenges with regards to in-service inspection (ISI) and repair [Wang et al (2012), Lubeigt et al (2015)]. The opacity and electrical conductivity of a sodium coolant makes optical and electromagnetic techniques less effective for ISI of NPP components.…”