For the decommissioning of the Fukushima Daiichi Nuclear Power Station, the primary containment vessel (PCV) internal survey for fuel debris spreading has been needed. The survey has been implemented using remotely operated robots. Localization of the robots during their operation is necessary to adjust sensor positions. In this research, we propose a localization method which combines a stereo camera-based method for absolute localization and a periodic structure tracking method for relative localization. The position accuracy for proposed method was verified in a mock-up test field, and it was confirmed that the position accuracy satisfied the required accuracy of 30[mm].