Abstract:

New acoustic emission sensors are developed for use in an environment of high temperature and high level of irradiation. Some charactristics and advantages in the construction design and technological process are summed up.(l)Two high curie point materials, Lead Metanio bate(PbNb2O6) and Lithium Niobate(LiNbO3), are selected as active elemant, which have good high temperature piezoelectric properties.(2)A sintering method with simple supporting is developed to bond the active element to the sensor case and eletrical leads, as a result the high temperature quality of the piezoelectric crystals is ensured and the technological process is fairly simplified.(3)A nickll alloy is spattered to the surface of the sensor to form wear film instead of a conventional protective plate and there is no problem of the delamination between the piezoelectric unit and the plate.(4)A mineral insulated cable made in a nickll wire, a nickll shield tube and a magnesia insulant is used for providing the signal output, it has a good performance resistant to high temperature and irradiation.The proof tests of the sensors are carried in the two following ways:(1)a comparative test of the new sensor with a sensor from abroad in a heated plate;(2)a sensitivity measurement of the sensor before and after the gamma irradiation.The results of the comparison tests are reported and they indicate that the sensors are capable of operation at temperatures above 400 ℃ and the levels of gamma irradiation as high as 2.4 ×106GY(lGY=1J/kg).

Key words: acoustic emission, piezoelectric sensors, high temperature, irradiation