Saturday, November 3, 2012

San Onofre ALMOST Caused A Nuclear Disaster

DAB Safety Team   November 02, 2012
Media Contact: Don Leichtling (619) 260-0160 or Ace Hoffman (760) 720-7261

Fluid Elastic Instability (FEI) is a phenomenon that can occur in poorly designed Steam Generators (SG’s) due to very 'dry' steam (low moisture content, aka high steam void fractions) causing the SG tubes to vibrate vigorously along their length (called the in-plane direction) until they hit their neighboring tubes due to tight clearances.  These forces can cause tube-to-tube ruptures, while the tight clearances between the tubes can be attributed to operating, poor design and or even manufacturing defects.  

At the end of January 2012, a radioactive leak in SONGS RSG Unit 3, resulted in an emergency shut down, the cause of which was later determined to have been fluid elastic instability (FEI >1) caused by higher vapor fractions (~99.6 %).  Later 8 tubes failed their “in-situ” pressure testing and leaked with a flow > 0.5 gallons per minute at Main Steam Line Break Testing Conditions which resulted in more than 800 additional tubes having to be plugged; which is something that has never happened before in the USA.  It is important to note that SCE’s poorly designed RSG’s now have more damaged and or plugged tubes than all the rest of the US reactor fleet put together and that is with only 7% of the tubes in Unit 3 and 8% of the tubes in Unit 2 having been visually inspected to date!

Imagine what would have happened if something like an “ordinary” Main Steam Line Break (MSLB) occurred where the void fractions would have reached 100% causing the vibration amplitude to increase exponentially, which would then cause hundreds of tubes to leak and or rupture, which would have then over-pressurized the steam generators, lifted the main steam safety valves and released 60 tons of radioactive coolant and steam into the Southern California environment within a matter of minutes. This would have caused a Fukushima Type of Nuclear Reactor Meltdown in SONGS Unit 3 Reactor, so Southern Californians were very lucky this time (See all the DAB Safety Team Papers.).

The truth is that San Onofre escaped becoming an International Nuclear Events Scale (INES) Level 7 nuclear disaster by the slightest of margins, unlike Fukushima!
The DAB Safety Team assisted by several SONGS Anonymous Insiders has concluded that SONGS Unit 2 Replacement Steam Generators (RSG’s) are in worse shape now than certified by the SCE and their three NEI Qualified, “U.S. Nuclear Plant Designers.”  Even at 70% power operations, if a steam line break outside containment were to occur in Unit 2, the depressurization of the steam generators with the failure of a main steam isolation valve to close, it would result in 100% void fraction in the degraded U-Tube bundle and the “straight leg portion” between the Tube Support Plates.  This condition of ZERO Water in the steam generators would cause fluid elastic instability (FEI) and flow-induced random vibrations, which would then result in massive cascading SG tube failures, involving hundreds of degraded active SG tubes, along with all the damaged inactive (all the plugged /stabilized) SG tubes.  With an undetermined amount of simultaneous tube leaks/ruptures, approximately 60 tons of very hot high-pressure radioactive reactor coolant would leak into the secondary system.  The release of this amount of radioactive primary coolant, along with an additional approximately 200 tons of steam in the first five minutes from a broken steam line would EXCEED the SONGS NRC approved safety margins.  So, in essence, the RSG’s will become loaded guns, or a nuclear accident waiting to happen.  Any failure under these conditions, would allow significant amounts of radiation to escape to the atmosphere and a major nuclear accident would easily result causing much wider radiological consequences and even a potential nuclear meltdown of the reactor!  Since these events would happen at an extremely fast pace, no credit is assumed in the first 5 minutes of the main steam line break accident for: (1) Enhanced Unit 2 Defense-In-Depth Actions - SCE Restart Plan Enclosure 2, Item 9.0, and (2) The differential pressure across the SG tubes necessary to cause a rupture will not occur if operators prevent RCS re-pressurization in accordance with their Emergency Operating - Enhanced Unit 2 Defense-In-Depth Actions - SCE Restart Plan Enclosure 2, Item 5.2,2, Probabilistic Risk analysis.

The above statement is consistent with the conclusions and reports provided earlier on this subject by:
1.     Fairewinds Associates Internationally Known Nuclear Consultant Arnie Gundersen and his team of Anonymous Industry insiders, who have had lengthy careers in steam generator design, fabrication, and operation.

2.     Professor Daniel Hirsch and Internationally Known Nuclear Consultant Dale Bridenbaugh.

3.     Dr. Joram Hopenfeld, a retired engineer from the Office of Nuclear Regulatory Research and NRC's Advisory Committee on Reactor Safeguards (ACRS) report issued in February 2001, which substantiated many of Dr. Hopenfeld's concerns,

4.     David A. Lochbaum, Director of the Nuclear Safety Project for the Union of Concerned Scientists (UCS).

The Operational Assessments reports prepared by AREVA, and Westinghouse “conflict and contradict” * with MHI’s Technical Report and Press Statements, on the causes and extent of degradation pertaining to the SONGS Unit 2 Steam Generator Replacement Generators.  The DAB Safety Team Expert Panel and SONGS Concerned Insiders opinion is that these reports are not comprehensive and fail to arrive at a concise and clear conclusion, because:

(1)  SCE Engineers have either not provided, or they are withholding all the information to these parties because of  “The consequences of being Wrong, Terminated or Fired”,

(2)  Due to competing and proprietary interests between the three NEI qualified, “US Nuclear Plant Designers”, these reports have not been openly and candidly discussed,

(3)  Time/Pressure exerted by SCE on these parties to prepare Operational Assessments in order to rush to Restart Unit 2 have led to incomplete conclusions,

(4)  Since nobody really knows, what really happened, all the Parties have a shared interest to “Operate Unit 2 at reduced power as a  “Test Lab to conduct Nuclear Experiments “ to determine, “What really went wrong with unit 3, so SCE can determine the Root Cause, corrective actions, repair and test plans to return both units 2 and 3 to full power operations.”

*NOTES: Just some examples of the conflicting and contradicting statements are shown below:

1. Independent Expert 1 states, “U-tube out-of-plane direction is more susceptible to flow-induced excitation than the in-plane direction due to lower U-bend natural frequency in the out-of-plane direction. U-tube FEI in the in-plane direction has never been observed in the U-tube SGs before its occurrence in the SONGS SGs. However, recent academic studies report (2005) that FEI may also occur in the in-plane direction, if tube motion in the in-plane direction is possible (no tube in-plane supports or low tube contact forces with the out-of-plane supports). “

2. Independent Expert 2 states, “Out-of-plane fluid-elastic instability has been observed in nuclear steam generators in the past and has led to tube bursts at normal operating conditions. However, the observation of in-plane fluid-elastic instability in steam generators in a nuclear power plant is a true paradigm shift.”

DAB Safety Team Comment to items 1 & 2: FEI in the in-plane direction has been identified as early as 1983 by Academic Scholars and Palo Verde Replacement Steam Generator manufactured in the early 2000s are designed for FEI. Weaver and Schneider in 1983 examined the flow induced response of heat exchanger U-tubes with flat bar supports. It is worth quoting the first conclusion of their paper: “The effect of flat bar supports with small clearance is to act as apparent nodal points for flow-induced tube response. They not only prevented the out-of-plane mode as expected but also the in-plane modes. No in-plane instabilities were observed, even when the flow velocity was increased to three times that expected to cause instability in the apparently unsupported first in-plane mode.”

3. Independent Expert 1 states, “ECT-based AVB locations are compared with design-based locations. It is evaluated that AVB insertion depth in actual SG is not changed compared with the design-based location. There is some Pattern-1 wear identified by visual inspection, for which Bobbin ECT was not able to detect as this type of wear.”

4. Independent Expert 2 states, "It should be noted that because of field spread effects the bobbin probe typically overestimates wear scar lengths." Even though no evidence of elongated wear scars is evident in Unit 2, it doesn’t necessarily rule out undetected in-plane instability. Wear scars at AVB locations may be too shallow to evaluate properly and AVB wear scar lengths may be shortened by a contact length that is small because of the presence of AVB twist. The best evidence of in-plane instability is the detection of TTW, not the detection of elongated AVB wear scars. Extensive inspections of the regions of interest with the +Pt™ probe show that possible undetected TTW would be less than 5 %TW. It is unreasonable to expect detectable elongation of AVB wear scars without the detection of TTW. The significance of elongated AVB wear scars is that the amount of elongation reveals the extent of unstable tube motion in-plane.

5. Independent Expert 3 states that he does not have access to the assembly procedures. The 0.12 to 0.14 dimensions are anecdotal (based on personal observation, case study reports, or random investigations rather than systematic scientific evaluation) without verification.

DAB Safety Team Comments to items 3 & 4 & 5: Will be provided later

Copyright November 02, 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.

AVB: Anti Vibration Bar
CPUC: California Public Utilities Commission
DBA: Design Basis Accident
ECT: Eddy Current Testing
FEI: Fluid Elastic Instability
MHI: Mitsubishi Heavy Industry
MSLB: Main Steam Line Break
NRC: Nuclear Regulatory Commission
SCE: Southern California Edison
TTW: Tube-to-Tube Wear