Pressure began to build in three reactors soon after the tsunami hit because the plant’s cooling system stopped operating when the electricity went off. Without an adequate flow of cool water in the reactors, the fuel rods began to overheat and produce explosive hydrogen gas.

Managers were worried about venting because it would release significant amounts of radioactive materials, but when they finally gave the order to do so — after being told to by the government — the workers found the venting system inoperable. With the power out, their commands from the control room did not open the valves. They then discovered that that radiation levels at one reactor were so high they could not attempt to manually open the valve. And at two other reactors, their attempts to open the valves failed, possibly because the equipment itself was damaged in the earthquake.

In Units No. 1 and No. 3, the gas leaked from primary containment structures and fueled explosions that ripped apart the reactor buildings, spewing radioactive material into the air. Unit No. 2 suffered a hydrogen explosion inside the primary containment.

Mr. Sarrack, reached by telephone, said that his proposal was opposed by the operations department officials at his company, who wanted direct control over the reactor rather than employing automatic systems. He was working at the time at the nuclear plant in Monticello, on the Mississippi River near Minneapolis.

He said he continued to believe that a passive system, like one using a rupture disk, would work better and could be set to rupture at a pressure just slightly less than the pressure at which the containment would rupture. In those cases, he said, venting is always preferable; the releases of radioactive materials during deliberate venting are expected to be lower than those resulting from explosions.

But the consensus in the nuclear industry supports the existing systems. Douglas E. True, the president of ERIN Engineering and Research of Walnut Creek, Calif., said: “In some cases you can argue it might be better to have a rupture disk. In other cases, it would certainly be better to have a manually controlled system.” For example, he said, the disk is backed up by a valve that is normally in the open position. If the disk ruptured and there was no electricity, it might be impossible to close the valve, and the venting would be permanent.

The Fukushima plant was designed by General Electric, and the venting systems that failed in Japan exists at similar plants designed by G.E. in the United States.

In a statement, James Klapproth, the nuclear energy chief consulting engineer at GE Hitachi, said that his company believed that the venting system would have operated in an accident within the “design basis” of the plant,” but that the Fukushima disaster was worse than what the plant was designed for. He said that the industry in this country had considered passive systems “at one time.”