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| Decommission San Onofre |
SONGS Insider
Secret: Southern California came close to having
a level 3 nuclear incident (or worse, a nuclear disaster), at both SONGS Unit 2 and Unit 3.
A radioactive
disaster was narrowly averted because of the off chance discovery that one of Unit 2 SG tubes had experienced a
loss of 90 % percent of its wall thickness!
This was discovered before the tube had a chance to fail (like the eight
tubes that failed in-situ testing in
Unit 3) because Unit 2 happened to be shut down for a scheduled refueling
outage, so its SG tubing were also inspected after the radioactive SG tubing leakage
problems were discovered in Unit 3. Note: These SG tubes have a wall thickness (wear) plugging limit of 35%, so this
single tube remained in use long after its safety limitation had been exceeded
by almost double (55%)! A single tube
failure does not sound important, unless you realize it contains highly
radioactive reactor core coolant that
is under both very high pressure and temperature; then any leak is very bad (think
massive radioactive atmospheric releases). A single tube rupture can also lead
to a cascade of tube ruptures.
A Perfect Example of highly radioactive
reactor core coolant: in
1991, leakage of about 55 tons of primary coolant occurred due to the failure
of one SG tube in a steam generator built by Mitsubishi in the No. 2
pressurized water reactor at the Mihama nuclear power station in Japan. At the same time, water pressure in the core
had dropped drastically and the ECCS kicked in, flooding the reactor and
shutting it down. If the core had been
left exposed, a meltdown -- an overheating of the fuel that can, if
uncontrolled, lead to a large release of radioactivity -- could have occurred. In
the following week an estimated 7 million Bq was released into the sea and an estimated 5 billion Bq of radioactive gas was released
into the atmosphere. This tube rupture caused the first International Nuclear Events Scale (INES) level 3 nuclear incident in Japan and ignited
social concerns all over Japan because it shattered the nuclear industry’s myth
of 100% safe reactors! SONGS MSLB Analysis + 12-11-19, page 14
To date,
there have been too many guesses, too many probabilities built around gamed
safety margins and too many already damaged tubes (thousands of which have not
been visually inspected) that any one or combination of, could cause a major
nuclear accident even without something like a Main Steam Line Break (MSLB) or
a big quake!
Given the
documented UNSAFE condition of Unit 2, there is no excuse for SCE to even consider
seeking a restart of Unit 2 except greed.
The NRC needs to make that crystal clear to SCE, otherwise they, like
SCE, have failed the public’s trust! – The DAB Safety Team
=================================================================================
Nuclear Safety Is
No Accident
The DAB Safety Team along with the support of an ever-growing
number of SONGS Concerned Insiders and Whistleblowers have prepared this analysis,
which is consistent with the conclusions presented in the publicly available
reports provided earlier on this subject by:
· Internationally Known Nuclear Consultant Arnie Gundersen and his
team of Anonymous Industry insiders, who had lengthy careers in the design,
fabrication, and operation of nuclear steam generators.
·
Professor Daniel Hirsch and
Internationally Known Nuclear Consultant Dale Bridenbaugh.
·
Publicly available posted
documentation by Dr. Joram Hopenfeld, a retired engineer from the Office of
Nuclear Regulatory Research and NRC's Advisory Committee, and
Background
Quote No 1: SCE is ultimately responsible for the
work done by their vendors and contractors.
NRC Chairman Allison Macfarlane
Quote No 2: Both San Onofre units will remain shut
down until repairs are made and we and the Nuclear Regulatory Commission are
satisfied it is safe to operate. Pete Dietrich
Quote No 3: Running the reactor at a 30 percent reduction in power may not
fix the problems but rather make them worse or shift the damage to another part
of the generators. It’s a real gamble to restart either unit without
undertaking repairs or replacing the damaged equipment. Arnie Gundersen
Quote No 4: AREVA States, "The nominal distance
between extrados and intrados locations of neighboring U-bends in the same
plane ranges from 0.25 inches to 0.325 inches due to the tube
indexing. There are 36 U-bends in Unit 2 SG E-088 and 34 in SG E-089 with
a separation less than or equal to 0.050 inches. The U-bends with the
smaller separation distances are much better candidates for wear
by rubbing yet do not exhibit TTW.”
Based on SONGS
Unit 3 experience, this behavior can change because of plugged/staked tubes due
to shifting of localized steam-dry out regions in the hot leg U-Tube Bundle
region of these U-bends with these extremely low clearances. These
extremely low clearances can cause very high steam velocities, which can then result
in fluid elastic instability, EVEN during the proposed 150-day monitoring
period EVEN at reduced power levels and EVEN
at higher steam pressures.
The DAB Safety Team Solve the Big Mystery Behind The Destruction
of SONGS Unit 3 Replacement Steam Generators (RSG’s) And The Limited Damage to
Unit 2 RSG’s:
Start
With Some Basic Thermodynamics: At lower steam pressures (~833 psi),
steam-water mixture has a saturation temperature of 5230F and more
internal energy aka HEAT (1198.2 Btu/lb.) as compared with higher steam
pressure (~942 psi), steam-water mixture has saturation temperature of 537.50F
and less internal energy aka HEAT (1194.7 Btu/lb.). Therefore, you can generate more Megawatts
out of the steam generator running it at lower steam pressure, if you supply
more reactor thermal power (HEAT) to the steam generator tubes from the
reactor. Lower steam pressures combined
with high reactor thermal power (HEAT), high steam velocities and narrow tube
clearances also promotes bad things,
like localized steam dry-out regions (vapor fraction >99%) in the hot leg
side of the U-Tube bundle, which can cause fluid elastic instability,
flow-induced random and severe vibrations, and excessive hydrodynamic pressures
(aka Mitsubishi Flowering Effect). These
adverse effects can, in turn cause excessive tube-to-tube fretting wear leading to cascading tube leakages and or ruptures,
increased tube support clearances and/or tube-to-AVB gaps, and even deformation
of the anti-vibration bar structure.
Tube-tube/AVB wear and deformation (aka Mitsubishi Flowering Effect) of the
floating anti-vibration bar structure without structural beams and lateral/mid-span
supports causes redistribution of tube-to-tube/AVB gaps and clearances, when
the steam generator reverts back from hot operating to cold conditions. This redistribution of gaps can lead to
differences in measurements during steam generator refueling inspections
compared with the original manufacturing/design gaps in the cold condition and can
lead to wrong projections and misleading conclusions regarding past and future
cycles operating conditions.
Add Some Operational History: The original SONGS CE Model 3410 steam generators
(OSG’s) were rated for 1705 MWt reactor thermal power. Over the years of operation of the SONGS OSG’s,
it became evident that the steam generator tubes, made predominantly of Alloy
600, were susceptible to primary water stress corrosion cracking (PWSSC). This
corrosion mechanism resulted in tube degradation necessitating plugging large
numbers of tubes after each tube inspection. In addition, the SONGS OSG’s
design had shown to be susceptible to tube through-wall wear and severe
corrosion of the tube supports. Continuing to operate with these highly
degraded steam generators involved substantial economic risks from forced
outages, extended refueling outages, as well as the direct costs of inspections
and repairs. SCE’s bid specification
required that the stay cylinder feature of the original steam generators be
eliminated to maximize the number of tubes that could be installed in the
replacement steam generators and to mitigate past problems with tube wear at
tube supports caused by relatively cool water and high flow velocities in the
central part of the tube bundle. Mitsubishi employed broached trefoil tube
support plates instead of the egg crate supports in the original design. In
addition to providing for better control of tube to support plate gaps and
easier assembly, the broached tube support plates were intended to address past
problems with the egg crate supports by providing less line of contact and
faster flow between the tubes and support plates, reducing the potential for
deposit buildup and corrosion. Mitsubishi
selected a u-bend configuration for the upper part of the tube bundle instead
of the square bend design of the original steam generators based on its
experience that u-bends were easier to fabricate and support and were easier to
inspect.
The original steam generators installed
throughout the domestic fleet of pressurized water reactors, including SONGS, experienced
widespread corrosion of the tubes and tube support plates, stress corrosion
cracking of the tubes, and wear at tube supports. These problems led to the replacement of
nearly all of the original steam generators, in most cases well before the end
of their design lifetime. For SONGS, the
design of the replacement steam generators included a number of design changes
to correct life limiting problems with the original steam generators, based in
part on consideration of SONGS-specific and industry-wide operating experience.
This included use of more corrosion resistant materials for the tubing and tube
support plates to mitigate corrosion. The tubes in the new Replacement Steam
Generators (RSGs) were fabricated with thermally treated Alloy 690, which has
superior corrosion resistance. The only
drawback the new Alloy 690 has, is that it has a 10% less thermal
conductivity/heat transfer rate compared with old tube alloy 600.
Therefore, to
achieve the thermal output of 1729 MWt from the new RSGs as approved by the NRC
in 2001 SONGS Power Uprate Application, SCE engineers needed to install 11%
more tubes in the new RSGs. By removal of
the stay cylinder from the OSGs, there was enough space to add only 4% (377)
more tubes. Since there was no room to add the additional 7% tubes, SCE
increased the length of each tube in the U-Tube Bundle (Outside the Industry
NORM and is partially responsible for Mitsubishi Flowering effect) by more than
7 inches to obtain 1729 MWt out of the RSGs. The Unit 2 RSGs were built with bigger tube-to-AVB
Gaps and no in-plane protection from vibrations caused by potential fluid
elastic instability conditions, because the OSGs did not experience that
phenomena.
Based on
information from anonymous SONGS operations personal, the root cause team of concerned
insiders, a cursory review of plant records (plant procedures, system
descriptions and plant daily briefing sheets), engineering calculations performed
using SONGS procedures and review of NRC AIT Report, SCE Operators were running Unit 2 RSGs at higher steam pressures (~863-942
psi) and lower reactor thermal power (HEAT 1715-1725 MWt) for almost 22 months with no reported and detected abnormality
(6 tubes with 28 to 90 percent wear of the tube wall thickness due to retainer
bar vibrations). Because of the short
measured lengths of these flaws, only the 90 percent indication was in-situ
pressure tested as part of condition monitoring. The affected tube was
successfully pressurized to 5300 psi with no leakage (Southern Californians were
saved from another nuclear accident).
The Unit 3 SG
manufacturing process used more accurate and tighter
tolerances, which improved tube-to-AVB alignment such that tubes had
more contact forces with AVB's and provided an effective “zero”
tube-to-AVB gap under operating (hot) conditions. According to trusted SONGS
operation insiders, SCE Engineers were convinced that Unit 3 RSGs were built
better than Unit 2 RSGs in terms of providing in-plane protection due to better
control of tube-to-AVB gap. Therefore, SCE
Engineers decide to operate Unit 3 RSGs at lower steam pressures (~833 psi) to
get more Megawatts out of the RSGs by supplying more reactor thermal power (HEAT
~1729 -1739 MWt) to the RSG’s tubes from the Unit 3 reactor. This was unfortunately their biggest
miscalculation. What happened next is
well known, because of the low steam pressures (~833 psi), combined with low
tube clearances (SONGS design: 0.250 inches; some found as low as 0.050
inches) and no effective in-plane tube support protection, the high reactor
power (HEAT) resulted in fluid elastic instability, flow-induced random
vibrations, excessive hydrodynamic pressures and localized steam dry-out
regions (vapor fraction >99.6%) which resulted in the destruction of SONGS
Unit 3 RSGs (1 tube leak, 8 tubes failures at MSLB conditions, 1800 tubes with tube-to-tube
/anti-vibrations bars/support plates wear – this amount of damage is unprecedented
in the history of the US Operating Nuclear “fleet”). Fluid
elastic instability and Mitsubishi Flowering Effects increased the tube-to-AVB
gaps, decreased tube-to-tube clearances and created lower and insufficient
contact forces in Unit 3, which were described inaccurately by the NRC and SCE
as a MHI manufacturing defect ,
presumably due to political and/or
financial reasons.
After 22
months of operation the severity of wear in Unit 2 was determined to be similar
to that experienced by Unit 3 after 11 months of operation. The steam generator in Unit 2 had about 2600
wear indications at AVB’s compared to about 3400 wear indications in Unit 3.
Without an effective in-plane support system, these high fluid velocities and
localized steam dry-out regions resulted in very large or uncontrolled
vibrations (amplitudes) of tubes in the in-plane direction and caused
fluid elastic instability, flow-induced random vibrations, excessive
hydrodynamic pressures and increased tube-to-AVB gaps and created insufficient
contact forces in Unit 3.
Analysis
Solves The Mystery: High steam pressures (~863-933 psi) and lower reactor
thermal power (HEAT 1715-1725 MWt), coupled with low tube clearances and no in-plane
tube support design accompanied with high steam velocities caused flow-induced
random vibrations and excessive hydrodynamic pressures, which resulted in SONGS
Unit 2 RSGs damage (high tube-to-anti-vibrations bars/support plates wear). Since the steam pressures were higher, the void
fractions were less than 98.5% and no fluid elastic instability occurred in Unit
2, which is consistent with the Westinghouse finding. The NRC,
AREVA, Westinghouse, MHI
and SCE all missed this key operational observation in the NRC AIT Report, SCE
Unit 3 Root Cause Evaluation and SCE Unit 2 restart Plan. MHI indirectly alluded to this fact in their
technical report but did not say it publicly for reasons unknown to the DAB
Safety Team -- perhaps they were afraid of backlash from SCE and NRC. At least one person working at SONGS discussed
this fact about operational differences with other personnel between Units 2
and 3, but nobody listened to him. His
findings were intentionally or unintentionally ignored because everybody inside
SCE was focused on blaming MHI in order to recover the insurance money and/or
absolving themselves of all blame. The DAB Safety Team is sure that MHI
will pursue this fact during arbitration proceeding to absolve them of this
blame and protect their reputation as a builder of high quality RSG’s.
Public Expectations: The public expects that the NRC complies
with President Barack Obama, Senator Barbara Boxer and the NRC Chairman’s Open Government
Initiative by using the
Reactor Oversight Process, when it audits SCE’s Licensing Basis Documents,
facility procedures/records, 10 CFR 50.59 Safety Evaluations, Unit 2 Restart
Documents and issues/approves Safety Evaluation, License Amendment Applications
and Inspection Reports, Responses to Confirmatory Action Letters and other
enforcement violations, as appropriate.
The NRC must complete its mission of ensuring public safety with
transparency and public involvement by issuing all documents, emails, telephone
records along with holding open and trial-like public hearings without any time
limitations from SCE, its vendors and/or contractors.
Questions
which must be answered by NRC and SCE prior to any Unit 2 restart: The questions
which NRC in its 95 page AIT Report the SCE and its vendors in their 1200 page San Onofre Nuclear Generating Station
Unit 2 Return to Service Report have
not answered completely, convincingly and unanimously are as follows:
(1) Whether fluid
elastic instability occurred, occurred for a limited time or did not occur at
all in the SONGS Unit 2 Replacement Steam Generators (RSG’s)?
(2) What was the contribution
of fluid elastic instability and “Mitsubishi flowering effect” in increasing
the Unit 3 Tube-to-AVB gaps, which were built better than Unit 2 and designed to provide
an effective “zero” tube-to-AVB gap under operating (hot) conditions?
(3) How were the SONGS RSG’s specified,
designed and fabricated as comparable replacements on a like-for-like basis for
the original steam generators in terms of fit, form and function with such numerous
untested and unanalyzed design changes under the 10CFR50.59 rule?
(4) Were these numerous untested and
unanalyzed design changes responsible for damage to SONGS RSG’s?
(5) Were SONGS RSG’s operating beyond their
design basis or Industry NORMs and if so, how did that impact the degradation
of RSGs?
(6)
Was this degradation the fault of SCE’s in-house design team, their
Performance Specifications coupled with their numerous design changes and/or
the MHI Fabrication/Testing Technology combined with Faulty Thermal-Hydraulic
Computer Codes, which caused the unprecedented damage to SONGS RSG’s?
(7)
Are the Unit 2 RSG’s qualified in the
“As-designed and Degraded Condition” for a MSLB or other Anticipated
Operational transients?
The DAB Safety Team and the Public expects that SCE
and their three NEI Qualified, “US Nuclear Power Plant Designers”,
Westinghouse, AREVA and MHI will revise their reports and arrive at concise and
clear answers (meeting the NRC Quality Assurance requirements as stated by NRC
Chairman Allison Macfarlane) to the puzzling public safety questions in the
Unit 2 Return to Service Report.
SONGS
Poor RSG’s Design: Due
to unsubstantiated claims, complacency, challenges and rewards of innovative
steam generators, time and financial pressures, both inexperienced Southern
California Edison (SCE) and Mitsubishi Heavy Industries (MHI) Engineers did a
very poor job of Industry Benchmarking and keeping up with the Academic
Research Papers on the basic lessons of steam generator design (how to prevent
the adverse effects of fluid elastic instability, flow-induced random
vibrations, excessive hydrodynamic pressures and preventing localized steam
dry-out regions observed in SONGS Units 2 and 3 RSG’s with high steam flows to
produce more megawatts than the original steam generators (1729 MWt vs. 1705 Mwt)).
In addition, SCE made numerous untested
and unanalyzed design changes under the pretense of 10 CFR 50.59 process (like for like change) and intentionally
(Public Perception) avoided the NRC 50.90 License Amendment Process. These factors contributed to the catastrophic
failure of a 570 million dollars piece of equipment vital to the safety of Southern
California.
SCE Restart Report for SONGS Unit 2: To address the tube leak and its causes,
SCE assembled a technical team from MPR Associates, AREVA, Babcock & Wilcox
Canada, PVNGS, EPRI, INPO, Westinghouse, Intertek APTECH and MHI, as well as
experienced consultants including former NRC executives and a research
scientist. On October 3, 2012, SCE submitted a 1200 page report
prepared by these experts (Under the closed Scrutiny, Guidance and Leadership
of SCE Managers) to NRC Region IV. The SCE Root Cause Evaluation Report,
Operational Assessments reports prepared by SCE, AREVA and Westinghouse, and
MHI Technical reports conflict and contradict with each other on the
causes and extent of degradation pertaining to the fluid elastic instability in
SONGS Unit 2 Replacement Steam Generators (RSGs) and Tube-to-AVB gaps in both
Unit 3 and Unit 2 RSG’s. MHI truly states that specific causes that
resulted in tubes being susceptible to fluid-elastic excitation are not yet
completely known.
PRESS RELEASE
The DAB Safety Team: November 28, 2012
Copyright November 28, 2012 by The DAB Safety Team. All
rights reserved. This material may not be published, broadcast or redistributed
without crediting the DAB Safety Team. The contents cannot be altered without
the Written Permission of the DAB Safety Team Leader and/or the DAB Safety
Team’s Attorneys.
