Year
1992
Abstract
Cerenkov glow image observation from boiling-water reactor(BWR) and pressurized-water reactor (FWR) irradiated fuel assemblies is used for the inspection. There is, however, a case where it is difficult or impossible to identify the image by the Cerenkov Viewing Device(CVD), such as STA/CRIEPI type ultra-violet region light image intensifier(UV-I.L) CVD, because of the long cooling time and/or low burnup. Now a new UV-I. I. CVD, which can observe the very weak Cerenkov glow from those spent fuel assemblies, has been developed. As this new device uses the proximity focused type UV-I.I., the efficiency to detect Cerenkov light and the image quality are improved. Moreover, since the image is transferred to the video signal, it is easy to improve the signal to noise ratio(S/N) and measure the Cerenkov light intensity. The new CVD was tested at BWR and PWR power plants in Japan, the fuel burnups ranged from 6,200 to 33,000 MWD/MTU and the cooling time ranged from 370 to 6,200 days. The test shows that the new CVD is superior to the STA/CRIEPI type CVD, and possibilities of the S/N improvement by the image integration and the burnup measurement by the Cerenkov glow intensity were discussed.