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Fukushima No. 1 meltdowns stir industry quest for ‘safer’ nuclear fuel

Designs by U.S. researchers offer hope of heading off future meltdowns

AP

In response to the disaster at the Fukushima No. 1 plant, the U.S. government dramatically increased funding to develop tougher protective skins for nuclear fuel, hoping to spur innovation in designs that had not changed much in years.

While the Department of Energy was spending $2 million on fuel designs before the March 2011 meltdowns, the funding reached as much as $30 million afterward.

Now scientists at multiple institutes are in the middle of developing designs that could start finding their way into test reactors as early as this summer, followed by larger tests later on.

The goal is to create nuclear fuel that is more resistant to damage and melting in extreme situations and less prone to a chemical reaction that makes its metal wrapping brittle and produces explosive hydrogen gas.

If researchers succeed, their work could give plant workers more time to keep an accident from spiraling into a meltdown that releases massive amounts of radiation. The work is no cure-all to prevent accidents, but it is a way of reducing risk.

“It’s basically buying time for the reactor,” said Andrew Griffith, the Energy Department’s director for fuel cycle research and development. “It’s basically an insurance policy.”Scientists in the U.S. government- and industry-funded efforts are experimenting with multiple solutions before narrowing their focus on the most-promising technologies.

Nuclear fuel has remained similar for decades.

Uranium dioxide is compressed into a pellet about the size of a fingertip. Those pellets are stacked into fuel rods up to 4.5 meters long and placed in a tube, called cladding, made from zirconium alloy.

That metal cladding resists corrosion in a reactor, holds up against heat and serves as a barrier that keeps radioactive elements in place without cutting too much into the energy produced by a nuclear plant.

Nuclear fuel is supposed to withstand accidents, but the catastrophe at the Fukushima No. 1 plant on March 11, 2011, shows how it can fail when pushed to extremes.

Tsunami crashed over the plant’s seawall and disabled the electrical gear needed to run the reactors’ cooling systems. When the cooling systems and backups stopped working, the reactors overheated.

As water levels dropped, the metal cladding around the fuel reacted with steam and oxidized, producing hydrogen gas. Scientists blame that escaping hydrogen gas for causing multiple explosions that damaged the facility.

The same reaction also produces heat, further contributing to the extreme temperatures that allowed fuel to melt and radioactive byproducts to escape. Some oxidation occurs during a reactor’s normal operation, but nowhere near the levels that occur in an extreme accident.

Scientists are considering a range of improvements.

Some are proposing fundamental departures.

The Electric Power Research Institute is experimenting with cladding made of molybdenum, which maintains its strength in higher temperatures than the zirconium alloys do. A stronger metal will do a better job keeping fuel from melting and slumping in a reactor in extreme accidents.

Engineers at the University of Tennessee are trying to coat cladding with ceramics that can withstand higher temperatures than existing cladding, while Westinghouse Electric Co. hopes to use silicon carbide as the base for its cladding in future fuel designs.

Quicker improvements may come from changing existing fuel designs.

Brent Heuser, a nuclear engineer at the University of Illinois, received U.S. funding to develop coatings that could be applied to existing cladding to prevent the chemical reaction that produces hydrogen, heat and weakens the cladding.

His team is also interested in “self-healing” fuel, which has added materials that migrate to the surface of a fuel rod during an accident and form a protective coating.

Any change must make financial sense. Adding safety improvements costs more money. That’s not attractive to cost-conscious utilities since the existing cladding already meets safety rules.

To get around the economic obstacles, some researchers hope to offset the extra cost of the protection measures by combining them with fuel that produces more energy before it must be replaced. Others, like Heuser, say regulators will need to force utilities to use the safer products.

“It’s often where businesses and regulatory bodies butt heads,” said Heuser.

  • midnightbrewer

    Or, rather than spending tens of millions of dollars trying to put lipstick on a pig, they could just switch to any of a half-dozen existing reactor designs that don’t melt down. Then there’s thorium.

    • Guest

      Thorium reactors are a THEORY! Most are on paper and none have ever gone much beyond the experimental stages of a lab. They will take decades to develop commercially and obtain licenses. There was one built at Oak Ridge, but if you read this, you’ll see a thorium reactor is actually Thorium and U-233. Thorium is converted to U-233. And this is actually a breeder reactor. This technology will take decades to be commercially viable.

  • George Henry

    Problem is they want more plutonium to make more bombs and such. Disgusting. Why not do away with nukes entirely and use solar, wind, geothermal, wave, and a host of must less costly and far safer technologies. I’d much rather drive by acres of solar panels than a nuke plant. Just sayin…

    • http://batman-news.com CHPer

      Have you done any research on the toxic brew of hazardous chemicals that are found in solar panels? I would not want to live or drive by “acres of solar panels” if they happened to catch on fire. I Would rather live or drive past a nuclear power plant since I have researched the emergency response, relative hazards of an event and the probabilities of an event as compared to the other “safer” technologies you list. Before you make a claim about the relative safety of an energy source, make sure you do some research first. Also, plants used to make energy from nuclear power are not used to make plutonium or bombs.

      • Leonard Suschena

        “Have you done any research on the toxic brew of hazardous chemicals that are found in solar panels?” If I was a betting person, my paycheck would say NO!

  • woohooman

    There is and has always been a better solution – THORIUM . . the decision to go with uranium was purely because of the weapons it can produce.