What became clear was that Japan lacked some of the basic hardware to respond to a nuclear crisis and, after initial resistance, had to look abroad for help. For a country proud of its technology, the low point occurred on March 31 when it had to use a 203-foot-long water pump — shipped from China, an export market for Japanese nuclear technology — to inject 90 tons of fresh water into the No. 1 reactor building. But perhaps more than anything else, the absence of one particular technology was deeply puzzling: emergency robots.

Japan, after all, is the world’s leader in robotics. It has the world’s largest force of mechanized workers. Its humanoid robots can walk and run on two feet, sing and dance, and even play the violin. But where were the emergency robots at Fukushima?

The answer is that the operators and nuclear regulators, believing that accidents would never occur, steadfastly opposed the introduction of what they regarded as unnecessary technology.

“The plant operators said that robots, which would premise an accident, were not needed,” said Hiroyuki Yoshikawa, 77, an engineer and a former president of the University of Tokyo, Japan’s most prestigious academic institution. “Instead, introducing them would inspire fear, they said. That’s why they said that robots couldn’t be introduced.”

Even before the accident at Three Mile Island in 1979, Mr. Yoshikawa, a robotics expert, and other researchers began building emergency robots capable of responding to a nuclear accident, eventually producing a prototype called Mooty. The robots were resistant to high levels of radiation and capable of surmounting mounds of rubble.

But the robots never made it into production, forcing Japan, in the aftermath of Fukushima, to rely on an emergency shipment of robots from iRobot, a company in Bedford, Mass., more famous for manufacturing the Roomba vacuum. On Friday, Tepco deployed the first Japanese-made robot, which was retrofitted recently to handle nuclear accidents, but workers had to retrieve it after it malfunctioned.

Image The industry's public relations campaign extends beyond the exhibits at plants in Shika and elsewhere. Credit... The New York Times

The rejection of robots, Mr. Yoshikawa said, was part of the industry’s overall reluctance to improve maintenance and invest in new technologies.