Robotic suction nozzle design optimization for severe accident portable air-cleaning system

Highlights: •Radioactive release to the atmosphere can be effectively stopped by the portable filtered air-suction system. •The covering capacity of the robot suction nozzle for the six cases of damaged sections is verified by mathematical model. •The mathematical model was verified with the fabricated scaled-down prototype (error∼5%). -- Abstract: A new portable filtered air-suction system (PoFASS) is proposed in this paper to prevent the release of radioactive fission products into the atmosphere from severe core meltdown accidents in nuclear power plants (NPPs), which has become very important after the Fukushima accident. The PoFASS consists of a robot arm with a vent line, a robot body equipped with a radioactive filter, and a robot suction nozzle that is the shape of a hand with fingers. By controlling the angle of the robot fingers on the robot suction nozzle, it can change its own shape to completely adapt to cover the damaged sections found in NPPs, and consequently, radioactive release to the atmosphere is effectively prevented. Surveying all the possible shapes of damaged sections in non-containment structures, six distinctive cases were identified. The minimum number of robot fingers that can cover all six cases of damaged sections was mathematically determined to be four, but in the design of the suction nozzle, six robot fingers were included to take into consideration the extension limit of the extensible cover of the suction nozzle as well as the area to be covered at the damaged sections. A complete mathematical model was developed to validate the covering capacity of the designed suction nozzle for all six cases. The minimum number of robot arm rods to access to any damaged section in NPPs was also determined to be three; hence, the PoFASS can access the hatch door of a containment buildings or the damaged sections of containment buildings, turbine buildings, and auxiliary buildings in NPPs. Experimental verification for the proposed PoFASS was successfully done with a prototype suction nozzle for the six cases of damaged sections.