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A Strategy to Prevent the Next Fukushima


Science & Tech  (tags: radia-active, energy, environment, healthconditions, protection, research, science, Sustainabililty, world, energy, discovery, design, concept, science, scientists, study, technology, research, performance, safety )

JL
- 570 days ago - green.blogs.nytimes.com
Since that accident, whose second anniversary falls on March 11, researchers have been looking at a variety of ways to prevent a repetition.At the Electric Power Research Institute, a nonprofit utility consortium, scientists think they have zeroed in on



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JL A. (275)
Tuesday February 26, 2013, 9:06 am
A Strategy to Prevent the Next Fukushima
By MATTHEW L. WALD

Among the most striking elements of the catastrophe at Fukushima Daiichi nuclear reactors in Japan were the hydrogen explosions that destroyed the upper parts of some of the reactor buildings. The hydrogen was released by a metal called zirconium in the overheated core.

Since that accident, whose second anniversary falls on March 11, researchers have been looking at a variety of ways to prevent a repetition. At the Electric Power Research Institute, a nonprofit utility consortium, scientists think they have zeroed in on one strategy: replacing some of the zirconium with a ceramic.

Zirconium is used not for its strength or for its resistance to heat or its price but because it is nearly transparent to neutrons, the subatomic particles that are released from the nucleus when an atom is split and go on to split other nuclei in a chain reaction.

Zirconium has always been known to release hydrogen when overheated, and that gas will burn or explode at a variety of concentrations, making it particularly troublesome. And under some circumstances, the fire cannot be extinguished with water.

The most prominent use of zirconium at nuclear reactors is in making the long metal tubes that hold the pellets of uranium fuel. In a boiling water reactor of the type that melted down at Fukushima Daiichi, each group of zirconium tubes, called a fuel bundle or assembly, sits inside a so-called channel, a tall metal box that is open at the top and bottom so that fuel can flow through.

Forty percent of the zirconium in the core is in those channels, said Christine King, the director of nuclear fuels and chemistry at the research institute. During an accident, she said, operators hope they can buy “coping time” to stave off the release of hydrogen from the channels.

That expression is widely used by nuclear scientists to refer to how long the reactor can cope with problems like a loss of electrical power, which led to the meltdown at Fukushima. “A few hours can make a big difference,’’ she said.

The institute, with $800,000 in research funds from the Energy Department, is looking at the feasibility of using silicon carbide in place of the zirconium. That is the ceramic that nuclear engineers use for the “pebble bed” type of reactor: the ceramic wraps around the fuel so that it cannot get hot enough to melt, and the ceramic will not burn.

It would be easier to persuade the Nuclear Regulatory Commission to approve its use in the reactor’s channels than in the fuel itself, they say.

Another potential use that could win early approval is using silicon carbide in the four-bladed control rod that is inserted between the channels to choke off the flow of neutrons when it is time to shut a reactor down.

Among the challenges is to manufacture the channels, which are about 10 feet long, in such a way so that they will not easily shatter or deform as they are heated, which could block the functioning of the control rods.

Beyond the Nuclear Regulatory Commission, scientists working toward a solution on replacing zirconium will need to convince reactor owners, who will be reluctant to introduce anything new that could could go wrong.

In normal operation, the existing fuel, with the zirconium fuel and the zirconium channels, performs nearly perfectly, said Kurt Edsinger, director of nuclear fuels at the institute.
 

SuSanne P. (182)
Tuesday February 26, 2013, 11:10 am
Thank you.
This is the bottom line IMO..."Beyond the Nuclear Regulatory Commission, scientists working toward a solution on replacing zirconium will need to convince reactor owners, who will be reluctant to introduce anything new that could could go wrong."
 

JL A. (275)
Tuesday February 26, 2013, 2:03 pm
You are welcome SuSanne and may well be right. You cannot currently send a star to SuSanne because you have done so within the last week.
 

Angelika R. (143)
Tuesday February 26, 2013, 4:17 pm
well, I am reading tis with mixed emotions, -naturally! Besides the point SuS already mentioned, -just think how far they could go on these $ 800,000 in research funds from the Energy Department if invested in CLEAN and safe energy research!
 

JL A. (275)
Tuesday February 26, 2013, 5:08 pm
Excellent point Angelika! You cannot currently send a star to Angelika because you have done so within the last week.
 

Julie F. (65)
Tuesday February 26, 2013, 5:18 pm
interesting
 

John B. (215)
Wednesday February 27, 2013, 4:57 am
Thanks J.L. for the very informative post. I have my own strategy, shut the plants down, problem solved. Read and noted.
 

JL A. (275)
Wednesday February 27, 2013, 8:14 am
You are welcome John--that is probably the most effective strategy.You cannot currently send a star to John because you have done so within the last week.
 
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