OPTICAL-PROPERTIES IN FIBERS DURING IRRADIATION IN A FISSION REACTOR

The effects of irradiation on the performance of optical fibers with s ilica core were examined during irradiation in a fission reactor, JMTR . The fibers performed well in terms of their radiation characteristic s up to the fast neutron fluence of 1.06 x 10(20) n/cm(2) and the gamm a ray dose rate of 4.3 x 10(9) Gy at 460 K. Three kinds of optical rad iation induced by the reactor irradiation were observed during irradia tion. Origins of these optical radiations were studied. Broad optical radiations centered at 0.45 and 0.73 mu m are thought to be Cherenkov radiation. The sharp optical radiation at 1.27 mu m was thought to be generated in the silica core by the gamma-ray irradiations in the reac tor.