Irradiation behavior and post-irradiation examinations of an acoustic sensor using a piezoelectric transducer

Nuclear instrumentation and measurement: a review based on the ANIMMA conferences

“…A selection was made after carrying out preliminary gamma irradiation tests (CEA facility, 1.5 MGy), mixed gamma and neutron irradiation tests in SCK•CEN BR1 reactor [144], and a full-scale device with PZT (Lead Zirconate Titanate piezoelectric ceramic) was successfully tested during a two-year exposure in hot cell surroundings at CEA LECA-STAR facility [145]. In the REMORA 3 experiment in OSIRIS reactor [146] at 144°C max with a PZT transducer, signal degradations were observed in phase 1 for high neutron fluences: ∼10 19 thermal n/cm 2 , 2.5 Â 10 18 epithermal n/cm 2 , 2.4 Â 10 18 fast n/cm 2 according to the revised data given in [147]. According to the scientific literature they could be due to a decrease in the electromechanical coupling factor of PZT at such irradiation levels [146], but, later, destructive examination of the sensor also showed a sticking defect in the Ag/Sn brazing at the interface between PZT and the stainless casing, with possible air trapping and area trapping changing with internal pressure and temperature, resulting in nasty incidence on ultrasonic transmission [147].…”

“…In the REMORA 3 experiment in OSIRIS reactor [146] at 144°C max with a PZT transducer, signal degradations were observed in phase 1 for high neutron fluences: ∼10 19 thermal n/cm 2 , 2.5 Â 10 18 epithermal n/cm 2 , 2.4 Â 10 18 fast n/cm 2 according to the revised data given in [147]. According to the scientific literature they could be due to a decrease in the electromechanical coupling factor of PZT at such irradiation levels [146], but, later, destructive examination of the sensor also showed a sticking defect in the Ag/Sn brazing at the interface between PZT and the stainless casing, with possible air trapping and area trapping changing with internal pressure and temperature, resulting in nasty incidence on ultrasonic transmission [147]. A printing technique is now being developed to ensure a good and reliable bonding.…”

“…A full-scale device was successfully tested at LECA-STAR facility [145]. The first instrumented fuel experiment À REMORA 3-was carried out in OSIRIS reactor [146,177], with an estimated maximal temperature of 144°C in the acoustic cavity: during the first phase, high fluences: ∼10 19 thermal n/cm 2 , 2.5 Â 10 18 epithermal n/cm 2 , 2.4 Â 10 18 fast n/cm 2 according to the revised data given in [147] led to signal and PZT transducer degradations but, using improved signal driving and processing, molar mass evolution measurements were still possible up to the end of the second phase with total revised irradiation as follows according to [147]: ∼1.3 Â 10 19 thermal n/cm 2 , 4 Â 10 18 epithermal n/cm 2 , 3.7 Â 10 18 fast n/cm 2 , 0.25 MGy gamma dose. An ultrasonic device is also developed to measure the composition and flow (high or low) of binary gas mixtures (C 3 F 8 /C 2 F 6 , up to 25% C 2 F 6 ), in the pipes of cooling systems at the CERN LHC, LHC-ATLAS experiment [178][179][180].…”

“…At this time, magnetostrictive alloys and piezoelectric materials: PZT, lithium niobate ( [155]. In all cases, not only the piezoelectric material behaviour must be considered, but also the behaviour of other components of the transducer, and particularly electrical and mechanical bonding means (mechanical pressure, brazed junctions) that can bias the interpretation of results [147,155].…”

“…In some cases assessments have been made directly in real conditions in a power reactor (TUSHT of Sonar device in Phenix reactor), as long as it was possible. In other cases, they are performed in experimental or research reactors in France (OSIRIS), Belgium (BR1, BR2), Norway (HBWR), USA (ATR), for example [25,82,144,146,147,[150][151][152][153][154][155]. Some convenient experimental adaptations may be necessary to perform remote electric and acoustic measurements via mechanical bounding to a delay line, and to control the experimental conditions (irradiation, temperature), within volume limitations.…”