In a solid spallation target of an accelerator driven system, high energy particles and high density heat are generated in the target material by irradiating a proton beam. Therefore, it is essential to establish a heat removal technique in the high energy radiation field. In addition, although heat transfer characteristics, especially boiling phenomena, are affected by the surface wettability, there is no research on the relation between the proton beam irradiation and the surface wettability. Thus, in this study, the effect of the proton beam irradiation on the surface wettability was investigated by comparing with those of ultraviolet and gamma ray irradiations with a titanium dioxide (TiO₂) sample. On the other hand, a photoelectric effect of TiO₂ on the wettability has not been studied in the past. Therefore, the photocurrent was detected when TiO₂ was irradiated by ultraviolet. And then, its effect on the surface wettability was investigated by measuring water contact angle on the sample surface. Furthermore, in order to study the photoelectric reaction due to the radiations, the photocurrents were also measured when TiO₂ samples were irradiated by gamma ray and proton beam. As a result, it was shown that the photocurrent behaviors in the radiations were much different from well-known photoelectric reaction of TiO₂.