Public Intelligence

Reactors No. 1 to 4 are seen at the Fukushima Daiichi Power Plant in Fukushima is seen in this satellite image, taken and released by DigitalGlobe March 18, 2011. About 300 workers are racing against time to restore power and cooling systems to the six reactors at Fukushima Daiichi and try to avert the biggest nuclear catastrophe since Chernobyl in 1986. Japan has entered its second week after a 9.0-magnitude earthquake and 10-metre (33-foot) tsunami flattened coastal cities and killed thousands of people. Mandatory credit REUTERS/DigitalGlobe/Handout

Experts Had Long Criticized Potential Weakness in Design of Stricken Reactor (New York Times):

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 is physically less robust, and it has long been thought to be more susceptible to failure in an emergency than competing designs. In the United States, 23 reactors at 16 locations use the Mark 1 design, including the Oyster Creek plant in central New Jersey, the Dresden plant near Chicago and the Monticello plant near Minneapolis.

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.

GE defends nuclear plant design (AFP):

General Electric defended its 40 year old Mark 1 reactors at the center of Japan’s nuclear crisis Friday, saying that early questions about reactor’s safety had long been addressed.

GE rejected recent reports of possible design weaknesses in the Mark 1, which accounts for five of the six reactors at the Fukushima plant, threatened with meltdowns after cooling systems failed.

“The Mark I meets all regulatory requirements and has performed well for over 40 years,” it said in a statement.

“The Mark I containment designs were modified in the 1980s to address improvements in the technology and changing regulatory requirements. All these changes required by regulatory authorities have been implemented,” it said.

GE did not address whether the Mark 1 was designed sufficiently to withstand the specific chain of events that damaged the Fukushima Daiichi (No. 1) plant — the 9.0-grade earthquake and massive tsunami that shut down the plants and their crucial cooling systems last Friday.

“We believe it is too early to know specifically what has happened in each of the reactors at Fukushima Daiichi,” it said.

Reactor crisis wipes £7.4bn from General Electric (Independent.co.uk):

The unfolding crisis at the Fukushima Daiichi nuclear plant has put a harsh spotlight on General Electric, the giant US conglomerate which built parts of the plant and which had been hoping to benefit from a renaissance in nuclear power that now looks to be on hold.

Almost $12bn (£7.4bn) has been wiped from the value of the company since Monday, and a retired nuclear engineer revealed how he and several colleagues resigned from GE in 1975 because of his safety concerns over the design of the Mark 1 containment unit used at the plant.

GE beefed up its nuclear business in 2007 by forming a joint venture with Hitachi of Japan that could bid to build new nuclear reactors around the globe. Climate change and energy security concerns are driving a global resurgence in support of nuclear energy, it said at the time.

But China and Germany are among the countries that have already said they will re-examine their nuclear building programmes in the light of events in Japan, and public opposition to nuclear power might now be expected to grow.

Meanwhile, GE is having to contend with criticism over the design of the reactors at Fukushima Daiichi, including the wisdom of housing spent fuel rods so close to reactors and their ability to withstand a loss of coolant. David Bridenbaugh, who resigned from GE in 1975, told ABC News why he had decided to quit the company. “The problems we identified in 1975 were that, in doing the design of the containment, they did not take into account the dynamic loads that could be experienced with a loss of coolant,” he said.

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4. Japan Earthquake: Nuclear Meltdowns and Thousands Dead
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