Quake risk to reactors greater than thought
From p.2 of 3, http://wtop.com/?nid=41&sid=2524357&pid=0&page=1
<http://wtop.com/?nid=41&sid=2524357&pid=0&page=1>
9/2/11
The Perry 1 reactor in Ohio tops the list with the steepest rise in the
chance of core damage: 24 times as high as thought in 1989. The four
other plants with the largest increases include River Bend 1 in
Louisiana, up nine times; Dresden 2-3 in Illinois, eight times; Farley
1-2 in Alabama, seven times, and Wolf Creek 1 in Kansas, also seven
times. The smallest increase was the 38 percent at North Anna.
Todd Schneider, a spokesman for First Energy Corp., which operates the
Perry plant, said the increase in its seismic risk estimated by the NRC
is misleading. He said Perry is capable of withstanding an even larger
earthquake than is typical for the region.
Personnel at a handful of other plants, including Indian Point outside
New York City and Oconee in South Carolina, have already redone the
NRC's calculations, and they show a much lower risk of core damage from
earthquakes. Those calculations have not yet been reviewed by the
agency, which along with other federal agencies is developing a baseline
earthquake risk for every nuclear power plant to use.
The average risk to U.S. reactors of core damage from a quake remains
low, at one accident every 500 years, according to the AP analysis of
NRC data. But predicting earthquake probability and damage is dicey; the
Japanese nuclear industry was taken by surprise in March when a
quake-driven tsunami far surpassed predictions and swamped the Fukushima
Dai-ichi site.
The U.S. nuclear industry may not be fully ready, either. Current
regulations don't require the NRC to make sure nuclear reactors are
still capable of dealing with a new understanding of the threats.
It's not just earthquakes. It is all types of events, including floods,
tornadoes and hurricanes, said an NRC official, who spoke on condition
of anonymity because he was not authorized to speak about the agency's
recent seismic work.
The worry about earthquakes is not so much direct damage to the reactor
vessel, the hardened enclosure where the nuclear reaction takes place,
but to water tanks and mechanical and electrical equipment needed when
disaster strikes. The failure of those systems could disable cooling
needed to prevent meltdowns of radioactive fuel.
In some of the emails obtained by the AP, NRC staffers worried that U.S.
reactors had not thoroughly evaluated the effects of aftershocks and the
combined impact of a tsunami and earthquake. They suggested plants might
need more durable piping as well as better flood barriers and waterproof
storage of essential equipment. Staffers talked of a need for bigger
supplies of fuel and batteries for extended losses of all electrical
power. One email expressed concern about some key pumps at Dresden that
might fail in an earthquake.
In a separate problem reported last month, GE Hitachi Nuclear Energy
acknowledged that its older control rods could get stuck if an
earthquake struck when reactors were running at low power. Control rods
are needed to stop the nuclear reaction. The manufacturer has alerted
the operators of 35 U.S. reactors at 24 sites, who are checking whether
replacements are needed. The AP documented scores of instances of such
wear and tear in a range of equipment in a June investigative series
showing that safety standards have been relaxed to keep aging reactors
within the rules.
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