The cabling options were limited, as most manufacturers will not guarantee the integrity of their cables in radiation environments. The Dalton tests were consistent with the literature that states polymers are susceptible to radiation damage and should be avoided for the use of cabling. However, the MICC cable types are water-tight and display no material degradation due to gamma or neutron + gamma radiation.
TWI identified two suitable radiation facilities for testing the sensors that had been constructed by the project partners PAL and Ionix, as well as suitable cabling solutions for connecting the sensors to the UT equipment during testing. Fibre optic, piezo-polymer and piezo-ceramic sensors underwent gamma and neutron + gamma testing at the two facilities.
The piezo-ceramic UT sensors, developed by Ionix, withstood the gamma + neutron and gamma exposure with no observable change in performance.
The piezo-polymer and fibre optic sensors, developed by PAL, survived longer than predicted, however, the polymer sensors were determined to be unsuitable for use under neutron radiation but could be utilised for the long term monitoring of radioactive waste. The fibre-optic sensors, with further development, could be implemented in an environment subject to neutron and gamma radiation.
UoS successfully modelled the radiation exposure at Dalton and were able to advise how to selectively radiation harden the sensor electronics.
XRD investigations revealed that gamma radiation reduced the crystallinity of polymer samples, nullifying the piezoelectric effect, whilst neutron + gamma radiation significantly altered the structure of the polymer, totally diminishing the piezoelectric effect.
The piezo-ceramic UT sensors developed by Ionix with the MICC type cabling were able to withstand the gamma + neutron and gamma exposure with no observable change in performance, allowing fixed point monitoring of asset integrity without shutdown or isolation in a high shine environment.