USA: nuclear reactors – assurances of safety precautions

they are unlikely to be affected by strong winds or unusually high tides.

Hurricane Sandy and N.J. nuclear power plants: Keeping it cool in high
winds http://www.newjerseynewsroom.com/science-updates/nj-nukes-prepare-for-sandy , 28 OCTOBER 2012 BY ROBERT KINKEAD On Sunday, New Jersey’s four nuclear power stations, along with another dozen or so along the Eastern Seaboard,were prepped to deal with Hurricane Sandy as that massive storm crawls up the East Coast toward the Garden State.

Federal regulators require nuclear reactors to be in a safe shutdown condition at least two hours before hurricane force winds strike, according to Alec Marion, VP of nuclear operations at the Nuclear Energy Institute, an energy industry association.

Typically, plant operators begin shutting down reactors about 12 hours before winds exceeding 74 miles per hour arrive. One of the most significant challenges in the shutting down process is keeping the reactor core cool. Stopping the fission, or
atom-splitting, process can be accomplished simply by lowering control
rods into the core. However, the heat-producing decay of nuclear
materials continues long after fission is terminated – at high
intensity for days and at progressively lower intensity for very long
periods.

Because potentially dangerous heat levels persist, it is essential
that cooling pumps continue to operate long after the reactor has been
shut down.

When the reactor is operating, it produces abundant electricity,
enough to power tens of thousands of homes and businesses and power
its own cooling pumps. When it is shut down, the reactor requires
electricity produced at other, distant generating plants to power its
cooling pumps. If hurricane force winds, or some other phenomenon,
damage the power lines connecting a shut-down nuclear station to the
power grid, there are emergency generators located at each nuclear
station that can supply power to the cooling pumps.

At the Fukushima nuclear disaster in Japan last year, the plants were
cut off from the national power grid and the emergency generators were
also knocked out of service by a powerful Tsunami, a gigantic wave of
sea water created by a nearby earthquake.

Nuclear operators such as Exelon and PSE&G in New Jersey seek to
locate and protect emergency generators and other key equipment so
that they are unlikely to be affected by strong winds or unusually
high tides. Federal regulations require that companies keep a minimum
seven days of fuel on site to keep generators operating.

There are four nuclear generating stations in Jersey: Salem I, Salem
II, and Hope Creek all situated next to one another in
Salem County on Delaware Bay; and Oyster Creek located in Lacey
Township near the Jersey Shore. Each of these reactors is enclosed in
a containment building, a protective shell of four-foot-thick concrete
designed to keep radioactive materials from escaping in case of
emergency. Such containment structures are tough enough to withstand
the impact of a 747 airliner crashing into it.