MADRID—Few parts of the world have experienced a psychosis comparable to that of a good many Europeans following the events unfolding at Japan’s earthquake-damaged Fukushima Daiichi nuclear power plant.

The European Union’s energy commissioner, Guenther Oettinger, went from declaring a nuclear “apocalypse” to confirming an atomic “catastrophe” to stating that a number of Europe’s reactors are unsafe. German Chancellor Angela Merkel, the EU’s most influential leader, ordered a shutdown of all German reactors built before 1980.

The European media encouraged citizens to buy iodine tablets as an antidote to radiation, God knows from what since any radiation from Fukushima would be carried in an eastern direction, over the Pacific Ocean. Several outlets explained that insufficient levels of iodine in salt can produce a variety of ailments, including fetal malformations—the implication being that if European citizens consume more iodine, they will not only protect themselves against radiation in the case of a nuclear accident but they also will be healthier.

Politics and ignorance combined to fuel this campaign of fear. In the case of Germany, the connection between what Oettinger, a member of the governing Christian Democratic Union, was saying and what Merkel, who faces difficult elections at the state level, was doing by shutting down nuclear plants in the face of widespread panic is all too evident. This, despite the fact that the German government had fought hard six months ago to extend the useful life of several reactors nearing the end of their cycle.

The manner and timing of the announcement, furthermore, that all 143 reactors in the European Union will be subjected to major tests contributed to the widespread impression that the nuclear industry, which has been experiencing a revival, is a threat to Europe. Longtime efforts in Spain, where there are eight reactors in operation, to overcome a deeply ingrained resistance have been undercut by the panic: The Madrid government is now suggesting that it might rethink its partial support for nuclear energy. Apart from France, whose industry—particularly through major companies such as Areva and EDF—has a big stake in building and operating plants worldwide, only Britain’s David Cameron has kept his cool and given signs that plans are still on to have new plants up and running by 2025.

Few authorities and news outlets explained, as the days went by, that the main issue at Fukushima was not the reactors themselves but the spent fuel pools, whose cooling systems had been affected because an electrical blackout hindered the operation of the water pumps. Why is this distinction important? Because the impression was given that the reactors might explode like a nuclear bomb. This is considered to be impossible.

Fukushima is a testament to the relative safety of those reactors in the face of a monstrous natural disaster unlikely to be replicated in other countries where similar plants are operating. This is not to say the safety of the spent fuel pools is unimportant. As Julio Gutierrez, a Spanish nuclear physicist, explains, in the future the industry will pay more attention to the safety of the pools. Safety efforts up to now have largely been concentrated on ensuring that nuclear reactor cores could not experience total meltdowns. The industry has succeeded in this.

In half a century, except for the accident at Chernobyl, the very few notable incidents involving commercial reactors had minor consequences. This includes Three Mile Island in 1979, despite a partial meltdown: No one died and the levels of radiation released into the atmosphere were roughly similar to those produced by natural sources. Chernobyl, by contrast, was a victim of the Soviet Union’s political system. Despite the decrepit state of its nuclear technology, the Soviet state refused to acknowledge a problem, let alone ask for help. Those had also been key factors in the disaster at the Soviet military’s Mayak plant in the 1950s.

Past experience teaches how counterproductive overreactions can be in this sensitive field. The United States would be less dependent on fossil fuels and the Middle East (and Venezuela) if Three Mile Island had not caused three decades of virtual paralysis in its nuclear industry. Perhaps the fiasco of ethanol subsidies, which have contributed to the scarcity of food supplies, might have been avoided too.

It would be a tragic mistake for Europe to reverse the encouraging trend of recent years toward the revival of nuclear energy for civilian use. Only Russia’s autocrats and Middle Eastern tyrants, on whom European energy has an unhealthy reliance, would stand to gain.