Behavior of newly-developed radiation resistant optical fibers in a variety of irradiation environments

Highly radiation resistant optical fibers, pure silica with OH content core and pure silica with fluorine doped core, were developed with gamma-ray irradiation testing. The developed optical fibers were examined on their dynamic optical phenomena during the irradiation in a 60Co gamma-ray irradiation facility, 14 MeV fusion neutron facility FNS, and a medium power fission reactor JMTR. As a result, the following optical phenomena have become clear. The behavior of transparency on the irradiated optical fibers was quite different in different radiation sources. The absorption loss induced by neutrons can be selective in a shorter wavelength region. Large and permanent absorption loss at wavelength shorter than 700 nm was observed under irradiation with fusion and fission neutrons. On the contrary, the increase in absorption loss was quite low in the wavelength from 700 to 1700 nm. The developed radiation resistant optical fibers were survived under irradiation up to about 3 x 1023 n/m2, and to gamma ray dose of 3.3 x 109 Gy. Optical radiation in the optical fibers were observed in the wavelength from 400 to 1700 nm, when the optical fibers were irradiated in the core region of JMTR. (author)