San Onofre Nuclear Generating Station Design and Emergency ...

San Onofre Nuclear Generating Station (SONGS)
San Onofre Nuclear Generating Station
Design and Emergency Response Capability
THE JAPAN NUCLEAR CRISIS – A major earthquake and subsequent tsunami damaged the reactor cooling and
back-up power systems at the Fukushima Daiichi Nuclear Power Station in Japan. With these systems out of operation, the fuel
became overheated and the interaction between the hot fuel rods and the water resulted in the generation of hydrogen gas.
The operators vented the gas from the reactor system to the surrounding secondary reactor building. The buildup of hydrogen gas from
the venting led to explosions in two of the reactor buildings, damaging their structures and allowing radioactive materials to escape.
DESIGN DIFFERENCES BETWEEN
SAN ONOFRE AND FUKUSHIMA DAIICHI
Pressurized Water vs. Boiling Water: Fukushima Daiichi
uses a boiling water design, while San Onofre has
pressurized water reactors. One of the key advantages of
a pressurized water reactor is that it has two cooling
loops, a primary and secondary, separated by steam
generators. The significance of the steam generators is
that water and steam from the secondary system can be
vented into the atmosphere to remove heat from the
nuclear fuel without releasing radioactive steam/gases
because the water being vented has not been in contact
with the nuclear fuel rods.
Robust Containment and Tsunami Wall: San Onofre has
a four- to eight-foot thick, post-tensioned, steel
rebar-reinforced concrete containment that includes an
internal steel liner. In addition, the San Onofre facility is
protected by a tsunami wall that extends 30 feet above
“mean lower low water,” the common reference point
used by geophysical professionals to talk about a
structure or facility's height. The most severe tsunami
for SONGS was calculated after extensive studies and
assumes that it occurs at the same time as a high tide
and storm surge, with wind driven waves.
Spent Fuel Storage: At San Onofre, the spent fuel
storage pools are located in a separate building adjacent
to the containment structure that encloses the reactor or
primary system. The used fuel rods are stored much
closer to ground level than they are at Fukushima
Daiichi, making it easier to add water if necessary. San
Onofre’s spent fuel pools are structurally robust, with
hardened, steel-reinforced concrete enclosures.
COMPARISON OF SEISMIC RISKS
Fault Types: The earthquake fault system that generated
the devastating earthquake near Honshu, Japan,
originated in a subduction zone. Tsunamis that can be
produced by an earthquake in a subduction zone are
projected to be larger than those resulting from
earthquakes in a strike-slip fault system, such as the
Newport-Inglewood/Rose Canyon faults near San
Onofre.
Richter Scale vs. Ground Movement: Much attention has
been focused on the Richter scale measurements of the
Japan earthquake – a 9.0 – and the implications of such a
quake in California. While the Richter scale is one
common way to measure the magnitude of earthquakes
at their epicenters, when assessing the seismic safety at
nuclear facilities, “peak ground acceleration” at the
facility’s location is a more meaningful way to measure
an earthquake’s potential impact, especially when the
epicenter is miles away. As approved by the U.S.
Nuclear Regulatory Commission, San Onofre was built
to withstand a peak ground acceleration of 0.67g
(g refers to the force of gravity). The maximum ground
acceleration experienced at Dai-Ichi was 0.561g in a
horizontal direction.
For more information, please visit www.songscommunity.com.
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last updated on 03/07/2012
SONGS13

San Onofre Nuclear Generating Station (SONGS)
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SAN ONOFRE BACK-UP AND SAFETY FEATURES
Back-up Generators: If a power outage occurred at San
Onofre, a total of four emergency diesel generators on
site, two per unit, each can provide approximately
5,000-kilowatts of power. Each generator can be
connected to provide back-up power to the other unit.
The generators are located in a reinforced concrete
building, separate from the containment structure that is
designed to withstand earthquakes and flooding.
Underground Fuel Tanks: Each generator has its own
fuel oil tank located in an underground vault, and each
tank provides a seven-day supply of fuel oil, which
allows adequate time to obtain more fuel oil if needed.
The structures that protect the generators and their fuel
supply are designed to withstand earthquakes and
flooding.
Battery Back-up: Emergency batteries and dedicated
switchgear are also part of San Onofre’s design to
achieve safe shutdown of the plant. They are located on
upper levels inside buildings that can withstand seismic
events and flooding.
Redundant Cooling: To provide redundant cooling for
each unit, two separate lines of safety systems are
available. In addition, a steam-driven cooling pump is
available to operate without electrical power, using the
steam generated by the reactor to circulate cooling
water.
Firefighting: San Onofre has its own on-site,
professional firefighting crew, with mutual aid
agreements with nearby fire departments.
EMERGENCY RESPONSE
Coordinated Response: SCE and nearby communities
have worked together since 1982 to develop and
continuously update a joint emergency response plan
that is tested regularly for reliability and practicality. This
working group includes emergency response
professionals from SCE, Orange County and San Diego
County, the cities of San Clemente, Dana Point, San
Juan Capistrano, Marine Corps Base Camp Pendleton
and California State Parks. Members of this group meet
monthly to ensure that coordinated plans are in place to
protect public health and safety in the region
surrounding the plant. The organizations routinely plan,
KEY FACTS
• Earthquake fault structures offshore of San Onofre are not of
the type that would produce significant tsunamis. San
Onofre’s critical equipment is located behind a tsunami wall
that is above the height of the most severe wave height.
• San Onofre has robust and redundant emergency backup
power capabilities, and stores approximately 4.5 million
gallons of water on site that can be used for replacement
cooling, even in the event of a loss of power.
• Southern California Edison is committed to learning from the
Fukushima accident, and is re-evaluating the capability of its
equipment, procedures and training to respond to “beyond
design basis” response events. We will incorporate the
operating experience from the events in Japan, enhancing
and further hardening the facility as needed.
train and perform multiple practice drills on all aspects of
the emergency program, including scenarios such as
earthquakes, terrorist attacks, loss of offsite power and
core damage. Every two years the Nuclear Regulatory
Commission and Federal Emergency Management
Agency evaluate the emergency program’s preparedness
through an integrated exercise.
Informing the Public: In the event of an emergency, a
Joint Information Center is activated to provide updates to
the public to keep them informed of the plant’s status.
SCE also maintains a community alert siren system, and
residents within the Emergency Planning Zone – a 10-mile
radius surrounding San Onofre – are regularly reminded
to turn on their radios or televisions for additional
information in the event that an emergency siren is
activated.
“Beyond Design Basis” Response: In the highly unlikely
case of an event larger than that for which the plant was
designed were to occur, Severe Accident Management
Guidelines (SAMGs) would be implemented in
cooperation with emergency responders. The SAMGs
work in concert with actions taken by both on-site and
off-site resources to protect the reactor core, containment
and spent fuel pools, and to prevent radioactivity release.
In addition to the SAMGs, additional procedures, operator
training and equipment are in place to ensure the reactor
remains cooled and covered.
last updated on 03/07/2012