The industry push to use more nuclear power is under attack in many places as a result of the disaster in Japan. For example Germany to shut down seven reactors and may mothball them entirely.

Germany will shut down its seven oldest nuclear power reactors and may not restart them, German Chancellor Angela Merkel said Tuesday.

The plants will be closed for at least three months under a moratorium imposed in response to the Japanese nuclear crisis, she said.

“Power plants that went into operation before the end of 1980 will be shut down for the period of the moratorium,” Merkel said.

The moratorium shelves a decision to extend the lifetime of Germany’s 17 reactors by an average of 12 years. Nuclear power supplies nearly one-fifth of Germany’s electricity and it’s an integral part of the European energy mix.

Reactor Design in Japan Has Long Been Questioned

Inquiring minds are reading Reactor Design in Japan Has Long Been Questioned

The warnings were stark and issued repeatedly as far back as 1972: If the cooling systems ever failed at a Mark 1 nuclear reactor, the primary containment vessel surrounding the reactor would probably burst as the fuel rods inside overheated. Dangerous radiation would spew into the environment.

Now, with one Mark 1 containment vessel damaged at the embattled Fukushima Daiichi nuclear plant and other vessels there under severe strain, the weaknesses of the design — developed in the 1960s by General Electric — could be contributing to the unfolding catastrophe.

When the ability to cool a reactor is compromised, the containment vessel is the last line of defense. Typically made of steel and concrete, it is designed to prevent — for a time — melting fuel rods from spewing radiation into the environment if cooling efforts completely fail.

In some reactors, known as pressurized water reactors, the system is sealed inside a thick, steel-and-cement tomb. Most nuclear reactors around the world are of this type.

But the type of containment vessel and pressure suppression system used in the failing reactors at Japan’s Fukushima Daiichi plant — and in 23 American reactors at 16 plants — is physically less robust, and it has long been thought to be more susceptible to failure in an emergency than competing designs.

G.E. began making the Mark 1 boiling water reactors in the 1960s, marketing them as cheaper and easier to build — in part because they used a comparatively smaller and less expensive containment structure.

American regulators began identifying weaknesses very early on.

In 1972, Stephen H. Hanauer, then a safety official with the Atomic Energy Commission, recommended in a memo that the sort of “pressure-suppression” system used in G.E.’s Mark 1 plants presented unacceptable safety risks and that it should be discontinued. Among his concerns were that the smaller containment design was more susceptible to explosion and rupture from a buildup in hydrogen — a situation that may have unfolded at the Fukushima Daiichi plant.

“What are the safety advantages of pressure suppression, apart from the cost saving?” Mr. Hanauer asked in the 1972 memo.

Questions about the G.E. reactor design escalated in the mid-1980s, when Harold Denton, an official with the N.R.C., asserted that Mark 1 reactors had a 90 percent probability of bursting should the fuel rods overheat and melt in an accident. A follow-up report from a study group convened by the commission concluded that “Mark 1 failure within the first few hours following core melt would appear rather likely.”

Michael Tetuan, a spokesman for G.E.’s water and power division, staunchly defended the technology this week, calling it “the industry’s workhorse with a proven track record of safety and reliability for more than 40 years.”

Mr. Tetuan said there are currently 32 Mark 1 boiling water reactors operating safely around the globe. “There has never been a breach of a Mark 1 containment system,” he said.

Several utilities and plant operators also threatened to sue G.E. in the late 1980s after the disclosure of internal company documents dating back to 1975 that suggested the containment vessel designs were either insufficiently tested or had flaws that could compromise safety.

In the late 1980s, all Mark 1 reactors in the United States were also ordered to be retrofitted with venting systems to help reduce pressure in an overheating situation, rather than allow it to build up in a containment system that regulators were concerned could not take it.

It is not clear precisely what modifications were made to the Japanese boiling water reactors now failing, but James Klapproth, the chief nuclear engineer for General Electric Hitachi, said a venting system was in place at the Fukushima plants to help relieve pressure.

What role the specifics of the G.E. design is playing in the rapid deterioration of control at the Fukushima plant is likely to be a matter of debate, and it is possible that any reactor design could succumb to the one-two punch of an earthquake and tsunami like those that unfolded last week in Japan.

Record of Safety in Question

GE relies on a “record of safety”. However, questions abound.

  • The question is what level of safety should be required?
  • How much of GE’s “record of safety” is attributable to design flaws corrected after implementation?
  • What tradeoffs in cost vs. safety are acceptable, even if there have been no accidents to date?
  • Germany does not have the same risks as Japan, but does it matter and if so how?

I do not have the answer to those questions but I can point out that when dealing with nuclear reactors, a track record of safety is good up until the first failure.

Bear in mind there were many design failures in Japan including a very poor decision to put emergency power generators at a level susceptible to flooding. Certainly the decision to extend the life of those reactors looks like a poor decision, especially in earthquake prone Japan.

One thing is for sure, older style reactors as well as reactors using “MOX” are going to come under intense scrutiny everywhere.

Mike “Mish” Shedlock
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