Development of seal technique for optical fiber; Soldering seal and silver alloy brazing seal

Matsui, Yoshinori ; Kikuchi, Taiji; Kakuta, Tsunemi

Recently, the number of in-situ tests using optical fibers as signal transmission lines is increasing in the JMTR, because of their noise-tolerant capability and recent development of irradiation proof type fibers. The convensional seal methods, however, have the problem of trust when they applied to the penetration of the irradiation capsule using optical fibers. As the solution of the problem, we selected soldering seal method that was already applied to the deep-sea optical fiber cables and, as its modification, the silver alloy brazing method. From the result of the out-of-pile test, it was confirmed that both soldering seal and silver alloy brazing seal would be applicable to the plug seal of irradiation capsules. Then the soldering seal was applied to a capsule with optical fibers and was irradiated for 5 operation cycles of the JMTR (about 3000 hours). No deterioration was found at the seal after irradiation. This suggested that in-core use of optical fiber was thought to be promising.