Friday, May 27, 2011

Modeling meltdowns in reactors and the media

Computer predictions of failure at Fukushima

tsunamiWorld Nuclear News has a report that computer analysis of reactor damage at Fukushima has indicated more serious fuel melting has probably occurred than previously thought at units 2 and 3. Two simulations show the water levels in the reactor pressure vessels far below where battered instruments said they were following sea water injection.

WNN reports that for unit 2, the first scenario suggests that water only recovered to about three meters below the top of fuel, and the second shows levels below the core entirely. For both scenarios the fuel temperature would have risen to 2,700 F which resulted in the zirconium fuel cladding reacting with water that released hydrogen.

WNN reports for unit 3 the simulation puts the water level at two meters below the top of the fuel. Extremely high temperatures resulted with 48 hours.

TEPCO has already reported nearly complete destruction of the fuel assemblies in unit 1.

According to the Washington Post for May 26, nuclear fuel in reactors units 1-3 at the Fukushima site began melting just five hours after Japan’s March 11 earthquake, a Japanese nuclear engineer told a panel of U.S. scientists. About 11 hours later, all of the uranium fuel in the facility’s unit 1 reactor had collapsed to the bottom of the reactor.

University of Tokyo’s Naoto Sekimura told a committee of the National Academy of Sciences it took all of 11 hours for the melting fuel to punch holes in the bottom of the reactor pressure vessel. Now it is leaking radioactive water. (March 18, 2011 NHK TV interview)

The newspaper also reported that NRC Commissioner George Apostolakis said that NRC staff members “thought the cores were melting” early in the crisis.

According to the Post, this conclusion, and the lack of credible information from Japan, resulted in the commission’s controversial recommendation to evacuate Americans within 50-mile radius of the facility, which is four times larger than the 13 mile evacuation zone set by the Japanese government.

“The 50 miles was very conservative,” Apostolakis told a National Academy of Sciences panel. “You can’t say someone was right or wrong in this situation.”

IAEA may have known about potential for meltdowns in March

While these simulations were being reported this week, a Japanese English language newspaper credits a former scientist at the Idaho National Laboratory with coming to similar conclusions in late March. The Mainichi Times reported May 23 that Chris Allison, Ph.D., an independent software developer, told the IAEA a meltdown occurred at one of the reactors at the Fukushima No. 1 Nuclear Power Plant three and a half hours after its cooling system started malfunctioning.

reactorcoreAccording to Allison's report, as obtained by the Mainichi, the simulation was based on basic data on light-water nuclear reactors at the Laguna Verde Nuclear Power Plant in Mexico that are about the same size as that of the No. 1, 2, and 3 reactors in Fukushima.

Nicole Stricker, Ph.D., a science writer at the Idaho lab, told this blog in an email that Allison’s work is independent of the lab and that neither the lab nor the Department of Energy had any communication about it with the IAEA.

“He took software developed at the lab and has been working with it on his own, but his current work is not affiliated with INL. Furthermore, it's worth pointing out that no simulation software can predict exactly what happened at Fukushima, especially without precise data about plant conditions.”

There is no word on what the IAEA did, if anything, with the results of Allison’s report. It’s not clear how the Japanese newspaper got word of it.

Dr. Allison received his doctorate in Mechanical Engineering from the University of Idaho in 1987 and BS and MS in Mechanical Engineering from the University of Wyoming in 1972 and 1973. He’s headed his own nuclear reactor software simulation firm located in Idaho since 1996.

Media meltdown gets a dose of reality

While reactor meltdowns in Japan were getting media attention, here in the U.S. people who follow the work of the U.S. Nuclear Regulatory Commission (NRC) have been wondering when the agency would respond to a piece of work published May 8th in the New York Times which portrayed the NRC as a toothless regulator in bed with the industry. bbq

The article, which is basically a BBQ of the agency roasting it on a spit turned by its critics, was penned by energy and environmental editor and reporter Tom Zeller, Jr., who has since left the newspaper to work for the Huffington Post.

It may be that what the critics of the NRC really want is to create a perception that the if the agency can’t do its job, that the nation’s 104 nuclear reactors should all be shut down. If so, Zeller helped them along toward achieving that objective with his article.

So it seems only reasonable and prudent that the NRC answered the NYT article with an OP ED published at the Huffington Post under the byline of NRC Chairman Gregory Jaczko.

He defended the agency’s record with surprising fortitude reminding readers, and presumably the former NYT editor and reporter now working at HP, of the agency’s responses to issues like the reactor lid at Davis-Besse. Jaczko also pointed out the agency’s safety concerns about the Westinghouse AP1000 reactors design are long-standing.

The New York Times article can only be described as a shameful departure from the standards of ethics and fairness the newspaper claims to uphold. Federal regulatory agencies usually just roll over when newspapers swat them with articles like this one.

In his OP ED at the Huffington Post the NRC Chairman seems to have found some backbone standing up for the broad principles of nuclear safety rather than rolling with the tactics of political expediency which he has been accused of doing over Yucca Mountain. That’s a step in the right direction.

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robert steinhaus said...

I am grateful for the effort required to research of of the information provided in this fine story. I would like to request help from anyone reading this Blog with regard to a simple question of fact relating to the GE BWR Mark 1 Containment design.

What is the wall thickness and composition of the Reactor Pressure Vessel for the GE BWR Mark 1 Containment?

My best information is that the Reactor Pressure Vessel for the GE BWR Mark 1 Containment is manufactured out of 6 inch thick forged steel, with extremely temperature, vibration, and corrosion resistant Inconel 600 plate on both the inside and outside (but many sources of information offered in the press lately have not been reliable and I have not been able to get any responce from a reputable industry source).
In the TMI accident, the hot corium produced by the partial melting of the core slumped to the bottom of the Reactor Pressure Vessel and penetrated a maximum of approximately 5/8th of an inch into the inner lining of the RPV.
How is it possible that the corium covered by water in Units 1-3 at Daiichi Fukushima has burned all the way through the bottom of the 6” thick Reactor Pressure Vessel?
Since molten corium is significantly heavier than water, how is it possible for corium to end up anywhere other than the very bottom of the Reactor Pressure Vessel?
How could molten corium burn a hole halfway up the side of the RPV if all of this heavy molten fuel rod material immediately sinks to the bottom of the vessel?

Anonymous said...

..... went to work for the Huffington Post. That figures.