ML13155A436

Comment (446) of Vinod Arora Opposing Restart of San Onofre Unit 2 Until NRC Completes Comprehensive Investigation

ML13155A436
Person / Time
Site:	San Onofre
Issue date:	05/03/2013
From:	Arora V - No Known Affiliation
To:	Rules, Announcements, and Directives Branch
References
NRC-2013-0070, 78FR22576 00446
Download: ML13155A436 (3)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001

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Wright, Darlene From: Vinod Arora [vinnie48in@gmail.com]

Sent: Friday, May 03, 2013 12:45 AM To: vinnie48in

Subject:

fyi The World's Foremost Renowned Professeur Titulaire, Michel J. Pettigrew, Ecole Polytechnique de Montreal, on the subject of fluid elastic instability and turbulence-induced vibration in 1970's states, "It is concluded that, although there are still areas of uncertainty, most flow-induced vibration problems can be avoided provided that nuclear components are properly analysed at the design stage and that the analyses are supported by adequate testing and development work when required.

There has been no case yet where vibration considerations have seriously constrained the designer." Violette R., Pettigrew M. J. & Mureithi N. W. state in a 2006 research paper, "In nuclear power plant steam generators, U-tubes are very susceptible to undergo fluid elastic instability because of the high velocity of the two-phase mixture flow in the U-tube region and also because of their low natural frequencies in their out of plane modes. In nuclear power plant steam generator design, flat bar supports have been introduced in order to restrain vibrations of the U-tubes in the out of plane direction.

Since those supports are not as effective in restraining the in-plane vibrations of the tubes, there is a clear need to verify if fluid elastic instability can occur for a cluster of cylinders preferentially flexible in the flow direction.

Almost all the available data about fluid elastic instability of heat exchanger tube bundles concerns tubes that are axisymmetrically flexible.

In those cases, the instability is found to be mostly in the direction transverse to the flow. Thus, the direction parallel to the flow has raised less concern in terms of bundle stability." Channel 1ONews Question to MHI: Edison says that a letter from MHI to the NRC proves that SCE believed the San Onofre nuclear plant's steam generators were safe when installed and that safety measures were not sacrificed for licensing reasons. Is that true?MHI Answer: MHI's top priority is, and always has been, the safe and reliable operation of all the plants and components that it designs, engineers, supplies and supports.

In designing steam generators, minimizing tube wear due to tube vibration is always given a high priority, and this was a priority for MHI during the design of the SONGS replacement steam generators (RSGs). The SONGS RSGs were designed according to industry standards and our customer's specifications.

The design went through an extensive review process which included the participation of third-party experts and MHI believed they would operate as expected:

safely and successfully.

No safety measures were sacrificed in the design.Note: MHIl Root Cause states, "The forced outage of Unit 3 and the subsequent discovery of thousands of U-bend tube wear indications in both Unit 2 and Unit 3 after such a short operating period was wholly unexpected.

Such an. outcome should have been prevented by the conservative design and the precision manufacture.

The identification of the unexpected tube degradation led to an extensive evaluation as to the causes the degradation and the questioning of the original design assumptions." Root Cause: Root Causes" are defined as the basic reasons [e.g., hardware (design deficiency), process (e.g., mechanistic or operational parameters), or human performance errors (e.g., Root Cause: Root Causes" are defined as the basic reasons [e.g., hardware (design deficiency), process (e.g., mechanistic or operational parameters), or human performance errors (e.g., lack of critical questioning

& investigative attitude, lack of solid team work and alignment between the designer and manufacturer, lack of academic research and Industry benchmarking, etc.) for a problem, which if corrected, will prevent recurrence of that problem., etc.) for a problem, which if corrected, will prevent recurrence of that problem.SONGS SG Root Cause: Negative Safety Culture (Production over Safety)Contributing Causes 1. Human Performance Errors* Lack of critical questioning

& investigative attitude by SCE/MHI* Lack of solid team work and alignment between MHI & SCE AVB Design Team* Lack of academic research and Industry benchmarking by SCE/MHI 1 a"

of 10CFR 50.90 License Amendment Process by SCE/MHI and Defective 10 CFR 50.59 Evaluation/Screen

• Complacency, Ignorance and Time Pressure by SCE/MHI* Lack of Benchmarking of Computer Codes and Full Scale Mock-up Testing by MHI* Inexperienced Designer and Low Cost/Inexperienced/Aggressive/Ignorant Manufacturer Blind Trustby NRC Commission in SCE's Error Likely Conservative Assumptions, Unexpl ained Safety Explanations and False Public Safety Sermons 2. Design Deficiencies

-SCE* Increase of the tube bundle heat transfer surface area from 105,000ft2 (OSG) to 116,100 ft2 (an 11% increase) to generate more heat, more heat and more profits* Increase in the number of tubes from 9,350 (OSG) to 9,727 (RSG), 7% increase in heat transfer surface area and low tube-to-tube clearances 0 RSG tube bundle being taller than that of the OSG (Average Length of Heated Tube increase from 680- 750 inches -equivalent to 700 tubes, 7% increase in heat transfer surface area* Lack of In-Plane AVBs (Incorrect Assumptions)

• Low-frequency 56 HZ retainer bar to fit excessive number of tubes* Reduction in Tube Wall thickness from 0.048 inches to 0.043 inches to pump more RCS Flows* Removal of Stay Cylinder 3. Operational Causes -To generate more heat, more power and profits -SCE* Operation at Low Steam Pressures* Increased Reactor Coolant Flows* Poor Circulation Ratios 2