'Comparison between Chernobyl, Japan out of place'

By EHUD ZION WALDOKS
March 15, 2011 01:57

Israeli experts say "two blasts at Fukushima reactors were controlled explosions to release pressure."

4 minute read.



Man evacuated from radiation zone in Japan tested

Japan Nuclear Radiation 311 (R). (photo credit: REUTERS)

The risk of a radioactive leak from the Japanese nuclear reactors at Fukushima damaged by last week’s tsunamis is minimal, Israeli nuclear engineers said Monday.

“In Japan, there’s a massive disaster with thousands killed by the earthquake and tsunamis. At Fukushima, only 14 people have been injured lightly yet the media spends 80 percent of its time talking about the reactors,” Prof. Arye Dubi said Monday. Dubi is a professor in the Department of Nuclear Engineering at Ben-Gurion University of the Negev, which is the only university in Israel with a nuclear engineering program at the moment.

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Moreover, “There’s no comparison with Chernobyl. Chernobyl was a 3,200MW reactor which exploded while working at peak capacity. The three reactors in Japan are around 500MW each and they were immediately and successfully turned off with the first tremors of the earthquake. Once it turns off, its output is reduced to about 5% or 25MW,” Dubi said.

There were no cracks in the pressure chambers that contain the radioactive material, he added, “there was no integrity breach.”

“The nuclear materials continue to emit dwindling radioactivity for a week to 10 days and need to be cooled down,” Dubi said.

It is those cooling systems which have been damaged and not the pressure chambers themselves, he explained.

“With the systems damaged, the material continues to heat up and produce steam and the pressure builds. That pressure needs to be released. The two explosions were controlled explosions to release the pressure; they didn’t happen by themselves,” he said.

The white clouds that came rushing out were steam “and the amount of radiation they emit is minimal and not dangerous,” Dubi said.

Although the Japanese government has evacuated the area and started checking people, they have not found a single sick person, Dubi said.

Two of the reactors were now being cooled with seawater, so the danger of an explosion was minimal, he said.

Using seawater to cool the reactor renders it inoperable in the future.

“There are two considerations when deciding whether to use seawater – safety and economics. Each reactor costs about $100m. so it’s not a decision to take lightly.

“However, the reactors have to be cooled down to prevent a leak and that’s a chance you can’t take, so they had to use seawater,” he said.

The third reactor needs to be connected by a pipe to the sea and Dubi said he expected that to happen later Monday night.

Prof. Yigal Ronen, also of BGU’s Department of Nuclear Engineering, concurred with Dubi, although he was less emphatic.

“The earthquake and tsunamis were an extremely rare event. There are a number of systems designed to prevent a radiation leak and at least two of them seem to be holding up,” he said.

The radioactive material is wrapped, there’s an outside building made of steel that shields the reactor and there’s an iron dome that prevents leakages, he said.

“The danger is if all of the protective systems have been compromised,” he said.

The buildings that house the nuclear fuel seem to be intact and the iron domes as well, he said.

“To all appearances, the situation seems to be trending towards the positive,” he added cautiously.
Ronen also concurred that any radiation which was released with the steam was negligible.

Turning to the chances of such an occurrence in Israel, both Dubi and Ronen dismissed any such scenario.

“The reactors in Japan are second generation ones built 40 years ago and they survived a 9.0 earthquake and subsequent tsunamis. That’s very impressive for the industry,” Dubi said.

Any reactors built in Israel in the future to generate electricity would be third or fourth generation and even more resistant to earthquakes, he said.

As it is, Israel’s two research reactors, one at Dimona and one at Sorek, were so tiny as to be in a different league entirely from the Japanese ones, the two professors said.

“The power of the research reactors, and therefore its radioactive material, is about 1% of the Japanese ones,” Ronen said.

“Moreover, the Dimona reactor has been designed to withstand even 9.0 earthquakes,” he added.

Should Israel bring in reactors to generate electricity, “they would be about 200MW each and even an 11.0 earthquake wouldn't shake them,” Dubi asserted.

On Sunday, the Israel Atomic Energy Commission said in a statement that the research reactors were designed to withstand natural disasters and that the emergency forces were well trained to deal with a leakage, should one occur.


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