Was Chernobyl really worse than Fukushima?

Fukushima is no Chernobyl. The unfolding Japanese nuclear crisis may be a Level 7 accident on the international severity scale – the same rating given the Chernobyl fire and explosion. But today, 25 years after that occurred, the reactor catastrophe in what was then the Soviet Union remains the worst such accident in history.

Chernobyl shot a plume of radioactive emissions high into the atmosphere, from whence winds scattered it around the globe. It eventually leaked radiation equal to that released by 400 Hiroshima-sized atomic bombs.

At least 50 emergency workers who fought to contain the meltdown’s initial effects died. Some 600,000 people were exposed to dangerously high radiation doses, according to the International Atomic Energy Agency (IAEA).

The social consequences of the accident were extensive, noted Yukiya Amano, IAEA director general, at a conference on Chernobyl’s effects held earlier this month near the accident site, in what is now Ukraine. Some 100,000 people were immediately ordered from their homes. Eventually, 350,000 residents from the surrounding area were permanently relocated.

“This was deeply traumatic for all concerned and had a lasting impact on their lives,” said Mr. Amano.

That said, the Fukushima Daiichi accident may be comparable to Chernobyl in that it appears likely to lead to a worldwide reevaluation of nuclear-power safety standards and new nuclear-power projects.

Different countries will react to Fukushima in different ways, writes Nathan Hultman, a Brookings Institution international economic expert. China may forge ahead with ambitious nuclear expansion efforts, while Japan and some European countries scale back.

“Fukushima simply exposed what has always, and always will, persist with nuclear power – it is a technology that is perceived as dangerous, and no amount of redundancy will ever be able to completely scrub the spectre of nuclear risk from discussions of energy policy,” Mr. Hultman wrote in an analysis of the accident’s effects.

Technically speaking, the Chernobyl reactor was a generation older – and an order of magnitude more dangerous – than its Fukushima counterparts.

Chernobyl had no containment vessel – the thick bottle of steel in which today’s reactors hold their fissile core. Chernobyl was also huge by today’s standards, with a core some three times larger than that of modern plants. Such larger reactors are more difficult to control.

The Chernobyl accident was simpler in that only one reactor unit was involved, however. The Fukushima Daiichi plant is the site of six reactors, with at least four suffering damage of some sort. Spent-fuel pools at Fukushima also experienced loss of coolant.

But Chernobyl’s release of radiation was far worse than Fukushima’s, according to the Japanese government. The Fukushima Daiichi accident has leaked only about 1/10th the radioactivity that escaped from the Chernobyl catastrophe, chief government spokesman Yukio Edano said Tuesday.

“It is clear that the two cases are different in nature,” Mr. Edano said at a press conference.

However, some European experts claim that Fukushima’s release of certain radioactive isotopes is within range of Chernobyl’s. Fukushima has emitted amounts of cesium 137 and iodine 131 that are close to those that escaped from Chernobyl’s burning core, according to estimates from Austria’s national weather service.

Chernobyl was located in the heart of Europe, so its fallout affected a large, populated area. Fukushima is on the edge of the Pacific Ocean, and prevailing winds have carried much of the emissions over the vast, uninhabited deep.

Today, the remains of the Chernobyl reactor are entombed in a giant concrete casing. That sarcophagus is crumbling, and the Ukrainian government is asking for international aid to help pay the $1 billion cost of a replacement.

Some 1,500 square miles of land around the reactor site remain a prohibited zone. Trees are bursting through the walls and roofs of buildings as nature retakes the area.

Despite the dire aftereffects of Chernobyl, Fukushima could end up having a greater negative effect on the credibility of the nuclear industry, some say.

The accident in the former Soviet Union affected one reactor in a totalitarian state with no culture of industrial safety, notes a recent report from the investment firm UBS. Fukushima occurred in an advanced industrial nation with state-of-the-art equipment and a reputation for engineering thoroughness.

“At Fukushima, four reactors have been out of control for weeks – casting doubt on whether even an advanced economy can master nuclear safety,” wrote UBS analysts in the study, released April 4.