Development of a remote inspection robot for nuclear reactor containment vessel

At the Unit 2 reactor (1F-2) of Fukushima Daiichi Nuclear Power Station, fuel debris inside the reactor pressure vessel (RPV) and primary containment vessel (PCV) is supposed to have fallen partly into the RPV bottom or into the pedestal. Prior to the removal of nuclear fuel debris, at 1F-2, remote equipment used for the inspection of platform conditions after accessing PCV bottom has been developed. This pater describes this developing state. The purpose of the inspection of platform conditions is to confirm the existence of fallen objects or damage on the platform inside the pedestal, as well as dose and temperatures. The inspection of platform conditions firstly performs a holistic confirmation using a camera-mounted pre-verification device with an expanding/contracting function, and then ensures the path of the remote inspection robot using the deposit removal device having a high-pressure water jet nozzle and scraper to remove obstacles. The remote inspection robot has the following features: (1) small so as to be able to pass through the inside of a 10cm diameter pipe, (2) crawler type that can get rid of bad road and obstacles, (3) having visibility under a dark place or steamy environment, and (4) having falling resistance and radiation resistance. The robot has been improved through repeated mock-up tests that simulate the inside of PCV. In the future, field verification tests will be performed. (A.O.)