Monday, November 22, 2010

Safety and Security Advantages of Small Nuclear Reactors

Ever since Chernobyl, much of the public has been afraid of nuclear power plants. While there are no nuclear plants in Western Europe, North America, or Oceania which are designed so badly or operated so irresponsibly as Chernobyl was -- thus offering nothing like the Chernobyl disaster experience -- the public is still concerned.

Along comes the small modular nuclear fission reactor (SMRs) -- which are even more safe and secure than modern western designs. The public should feel better about nuclear by learning more about SMRs. And government regulatory agencies should be feeling much better about licensing the new SMR designs, given their improved safety and security aspects. Here is more from John Wheeler:
small modular reactors offer several big advantages that make them safer:

They are smaller, so the amount of radioactivity contained in each reactor is less. So much less in fact, that even if the worse case reactor accident occurs, the amount of radioactive material released would not pose a risk to the public. In nuclear lingo we say SMRs have a smaller “source term.” This source term is so small we can design the plant and emergency systems to virtually eliminate the need for emergency actions beyond the physical site boundaries. Then, by controlling access to the site boundary, we can eliminate the need for off-site protective actions (like sheltering or evacuations).

These smaller reactors contain less nuclear fuel. This smaller amount of fuel (with passive cooling I’ll mention in a minute) slows down the progression of reactor accidents. This slower progression gives operators more time to take action to keep the reactor cool. Where operators in large reactors have minutes or hours to react to events, operators of SMRs may have hours or even days. This means the chance of a reactor damaging accident is very, very remote.

Even better, most SMRs are small enough that they cannot over heat and melt down. They get all the cooling they need from air circulating around the reactor. This is a big deal because if SMRs can’t melt down, then they can’t release radioactive gas that would pose a risk to the public. Again, this means the need for external emergency actions is virtually eliminated.

Also, some SMRs are not water cooled; they use gas, liquid salt, or liquid metal coolants that operate at low pressures. This lower operating pressure means that if radioactive gases build up inside the containment building there is less pressure to push the gas out and into the air. If there is no pressure to push radioactive gas into the environment and all of it stays inside the plant, then it poses no risk to the public.

SMRs are small enough to be built underground. This means they will have a smaller physical footprint that will be easier to defend against physical attacks. This provides additional benefits of lower construction costs because earth, concrete and steel are less costly than elaborate security systems in use today, and lower operating costs (a smaller footprint means a smaller security force).

In summary, small modular nuclear reactors offer potential safety and security advantages over larger commercial reactors because they can be designed (1) to have smaller source terms, (2) to have accident scenarios that progress more slowly, (3) to be meltdown proof, (4) to operate at lower pressures, and (5) to have smaller security footprints.

These safety and security advantages can result in considerable cost advantages. A large percentage of a nuclear plant’s operating expenses go into emergency planning and security. It is possible that four or five SMRs packaged together to provide the equivalent of a large nuclear unit could operate with a smaller staff size and lower costs. However, because existing rules were written for larger reactors, some changes to NRC regulations will be required for SMRs to take full advantage of their inherent safety and security features. There are groups already working on these changes.

These safety and security advantages offered by SMRs, when combined with lower initial capital costs, shorter construction times, and scalability, may tip the scales in favor of a new generation of small, factory built modular reactors. _ThisWeekinNuclear

SMRs are less expensive to build and install, with a much quicker installation period from start to finish. The main obstacle to SMRs -- besides public ignorance and left-Luddite opposition -- is the lazy laggardness of government regulatory agencies. US NRC bureaucrats are so slow and lazy to get off their fat asses, that it may be ten more years before they license the first SMR -- despite a solid decades-long safety record by SMR manufacturers who supply the US military.

Some SMRs are designed to go as long as 20 years between refueling. SMRs of the future are likely to be designed to go much longer.

Sometime between now and the next ice age, it would be nice if government bureaucrats would do their jobs so that we can at least stay warm and well-lit in our underground bunkers.



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