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Document analysing the (un)safety status of San Onofre Nuclear Power Plant

San Onofre Nuclear Waste Generating Station Decommission San Onofre 29 sept 12 Aging Nuke Plants On Fault Lines In Tsunami Hazard Zones = Fukushimas… Any Questions? PLEASE Turn off a light for Fukushima USA / San Clemente

The Number 1 US Nuclear Safety Concern ==> San Onofre’s Replacement Steam Generators The DAB Safety Team is thankful to numerous anonymous concerned SONGS Workers, who have provided factual information in the interest of the Public Safety to us so that we could arrive at these “Reasonable Conclusions” regarding SONGS Replacement Steam Generators
Degradation.  We acknowledge Fairewinds Energy Association, Professor Daniel Hirsch, Friends of the Earth, San Clemente Green, Media, News Papers and the SD Reader, whose material has contributed to the successful completion of this document.

NOTE: These Preliminary Conclusions are subject to change upon receipt
of Southern California Edison’s (SCE) SONGS Unit 2 Restart Plan and
Mitsubishi Heavy Industries (MHI) Root Cause Evaluation.

If SONGS Unit 2 is allowed to operate at reduced power, an Un-isolable
main steam line break accident can occur at any time, due to a
postulated design basis earthquake and/or any other associated
failure.  Due to this event, the depressurization of the steam
generator caused by the steam line break coupled with the excessive
vibrations due high differential pressure (> 2250 psi), high reactor
coolant water temperature inside the tubes, the compact space between
the SONGS U-Tube Bundle and the moisture separators (compared with
other Mitsubishi Steam Generators) and the steam over-pressurization
would cause the elastic deformation (NRC AIT Report, Mitsubishi
Preliminary Cause Evaluation) of the taller U-tube bundle due to
increased U-tube bundle height, high localized steam-voids or dry-outs
(two-phase mist region, almost devoid of water in undefined central
portion of the U-tube bundle above the 7th support plate) and
narrow-pitch/tube diameter ratio.  This unanalyzed and rare phenomena
not experienced in the Steam Generators operating history, in turn,
would cause the onset of fluid elastic instability conditions due to
the 100% localized steam voids in the central portion of U-Tube bundle
above the 7th Support Plate.  The fluid elastic instability conditions
would result in further lowering the already low in-plane tube
clearances (Attributed to unanalyzed effects because of addition of
more tubes to achieve more thermal MWt out of the SGs). The
combination of these factors along with a poorly designed
anti-vibration support structure [low damping capability of the
support structure (i.e., the tube support plates, the tube-sheet, and
the anti-vibration bars)] would result in excessive and violent
vibrations, cause tubes to hit each other in the in-plane direction,
result in leaking tubes, which would cause high-pressure primary
sub-cooled water jets.  These high-pressure jets would cut holes into
other already worn tubes and create undetermined number of cascading
tube ruptures.

The cumulative effects of the above conditions along with the
unanalyzed effects of plugged and staked tubes would rupture other
damaged, plugged, staked and worn tubes.  The amount of leaking
reactor coolant through these ruptured tube cuts is beyond the
analyzed limits of a SONGS UFSAR Analysis  [Three combined independent
events loads (DBE + MSLB + LOCA)] that would be released via the
blowing radioactive steam carrying Un-partitioned reactor coolant from
the Un-isolated steam generator into the environment.  This
uncontrolled radiological accident would release significant amounts
of radiation, which could adversely affect the health and safety of
all Southern Californian residents plus the transient population
within the 10-mile Emergency Planning Zone.   We believe that this
scenario can also progress into a nuclear meltdown of the reactor due
to potential errors by plant operators unable to diagnose and control
rapidly changing plant conditions due to the confusion caused by the
non-user friendly and complex, abnormal, emergency operating and
emergency plan implementing procedures.  …
http://decommission.sanonofre.com/

September 29, 2012 - Posted by Christina Macpherson | safety, USA