Saturday, September 19, 2009

Near Term Future of Nuclear Reactors

Newer nuclear reactors are designed to be safer, last longer, produce less waste, and be less likely to abet nuclear weapons proliferation. The following is excerpted from an earier Wall Street Journal article. AF
The current generation of nuclear plants requires a complex maze of redundant motors, pumps, valves and control systems to deal with emergency conditions. Generation III plants cut down on some of that infrastructure and rely more heavily on passive systems that don't need human intervention to keep the reactor in a safe condition reducing the chance of an accident caused by operator error or equipment failure.

For example, the Westinghouse AP1000 boasts half as many safety-related valves, one-third fewer pumps and only one-fifth as much safety-related piping as earlier plants from Westinghouse, majority owned by Toshiba Corp. In an emergency, the reactor, which has been selected for use at Southern Co.'s Vogtle site in Georgia and at six other U.S. locations, is designed to shut down automatically and stay within a safe temperature range.

The reactor's passive designs take advantage of laws of nature, such as the pull of gravity. So, for example, emergency coolant is kept at a higher elevation than the reactor pressure vessel. If sensors detect a dangerously low level of coolant in the reactor core, valves open and coolant floods the reactor core. In older reactors, emergency flooding comes from a network of pumps which require redundant systems and backup sources of power and may also require operator action....

...Further out, Gen IV reactors, which use different fuels and coolants than Generation II and Generation III reactors, are designed to absorb excess heat better through greater coolant volume, better circulation and bigger containment structures. Advanced research into metal alloys that are resistant to cracking and corrosion should result in more suitable materials being used in plants, too, and giving them longer useful lives....

...Some researchers see the answer to the safety problem in revolutionary reactor designs that promise to be more "inherently safe" physically incapable of suffering a catastrophic meltdown. One such design, at least in theory, is the Pebble Bed Modular Reactor, being developed in China and South Africa. It's powered with balls of uranium-filled graphite rather than the typical fuel rods. If the cooling system were to fail, the reactor temperature stays well below the balls' melting point and then automatically cools down....

... Makers of Generation III models are addressing the cost issue in a number of ways. For one, they claim the reactors will remain in service more years, so construction costs will be spread over a longer operating life. Today's plants are being designed to last at least 60 years longer than any other plants except hydroelectric dams. Existing nuclear plants were expected to be retired after 40 years, though roughly half have gotten 20-year license extensions.

The new plants are also designed to be much simpler and quicker to build, reducing financing costs by potentially hundreds of millions of dollars. For instance, there's the ABWR reactor, which has been built in Japan by GE-Hitachi and which NRG Energy Inc. hopes to build with Toshiba's help in South Texas. The reactor is built in modules, vastly speeding construction time. GE-Hitachi, a joint venture of General Electric Co. and Hitachi Ltd., says it has built the plant in 42 months in Japan, which is more than twice as fast as the Generation II reactors it built in the 1980s. The company compares construction methods to putting up a modular home versus constructing a stick-built house....

...Babcock & Wilcox, a unit of McDermott International, has designed a small 125-megawatt reactor that would be built at its U.S. factories and then delivered to power-plant sites by rail or barge. This would eliminate a bottleneck and the associated higher costs for ultra-heavy forgings that are required for large reactors. Small reactors could be built at a number of domestic heavy-manufacturing sites. The Lynchburg, Va., company has been building small reactors and other key components for Navy ships for decades, at plants in Indiana and Ohio.

Another plus of small reactors: They're designed to be refueled less frequently, reducing the number of refueling outages. Instead of every 18 months to two years, they could go four or five years, reaping a saving from having less down time. Another feature of some reactors is the ability to do more maintenance while plants are running, again reducing idle time....

...Some Generation IV reactors, known as fast reactors, may offer a breakthrough in the future because they're designed to burn previously used fuel.

GE-Hitachi, for example, is developing a fast reactor called Prism that would take spent fuel or weapons waste, sitting in storage today, and use nearly all of it as fuel, leaving little waste. What's left would also be less radioactive than current waste, and would need to be stored for hundreds of years instead of thousands of years, scientists say. Fast reactors are able to unlock energy in waste because they can burn plutonium, neptunium and other materials that Generation II and Generation III reactors leave behind.

GE-Hitachi estimates there's enough energy sitting in nuclear storage sites in the U.S. to completely meet the nation's energy needs for 70 years, if fast reactors were used to convert waste into electricity...

Excerpted from a Wall Street Journal story

In addition to these designs, several other small, modular reactors are being built by scientists formerly at Los Alamos, Sandia, Microsoft, and other reputable firms and labs. Thorium cycle reactors and reactors that run on depleted and non-enriched uranium are also on the way.

All in all, the issues of safety, waste, and proliferation are being answered admirably by designers, engineers, and technologists. Now it is time for the governments of the world to facilitate the best form of baseload large scale power generation currently in existence (along with promoting further research into bioenergy, clean CTL, GTL, BTL, oil shales, oil sands, enhanced geothermal, etc).

The alternative is energy starvation -- something the faux environmental dieoff.orgiasts want to see, but not something that any sane person wishes.



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