Development of radiation resistant in-water transmission system using visible light with environmental robustness

Takeuchi, Tomoaki   ; Otsuka, Noriaki ; Nakano, Hiroko  ; Shibagaki, Taro*; Komanome, Hirohisa*; Tsuchiya, Kunihiko 

Considering that reactor buildings could be filled with water under severe accidents, a development of the wireless transmission system in water is necessary. In this study, transmission method using visible light was adopted because of its relatively lower attenuation rate and higher transmission rate in water. In the designed transmission system, two-dimensional transmission devices were adopted. LEDs arranged in a two-dimensional array and a camera using a CMOS image sensor, that is like a 2D aggregation of PDs, were used as the light emission and receiving devices, respectively. Moreover, both of pattern and flicker signals can be simultaneously emitted. To confirm the environmental robustness, the in-water transmission tests using the two-dimensional transmission devices were performed with and without air bubbles. The results indicated the pattern signals were more easily influenced than the flicker signals by the air bubbles. In addition, surface mounting LEDs were more suitable than bullet-type LEDs because of their good distinctiveness of the light spots from each LED. On the other hand, irradiation tests for the LEDs were performed. The results again indicated surface mounting LEDs were advantageous because the decrease rates of the total luminous flux with absorbed dose were lower than that of the bullet-type LEDs.