It is interesting, I see a connection with the San Onofre failures and untimely demise with the recent NRC OIG licensing amendment changes..10 CFR 50.59. The licensees and the plant staff aren't maintaining the plant design bases and licensing bases.The principle plant design and licensing document is called the FSARs is not being updated or maintained.
Generally the operating staff calls the principle plant licensing document (the FSARs) as a comic book because during construction and licensing the principle strategy was to keep the FSARs as skimpy as possible to allow the plant to get away with as much as they can.
Ms. Allison Macfarlane, Chairman,US Nuclear Regulatory Commission Washington, DC 20555Mr. John Stetkar, ChairmanAdvisory Committee on Reactor Safeguards US Nuclear Regulatory Commission Washington, DC 20555
Subject: Nuclear Safety Concern Regarding Cooper Nuclear Station (CNS) Turbine Building (TB) Panel Blowout Pressure Unanalyzed ConditionDear Chairmen Macfarlane and Stetkar,
I am writing to you with a nuclear safety concern that I do not believe has been adequately addressed. I originally raised this safety concern nearly four years ago. I am writing to you now because of my disappointment in the timeliness and in the technical effectiveness of the reviews conducted by the NRC Region IV office. My nuclear safety concern is in regard to the assumed Turbine Building (TB) Panel Blowout Pressure related to a Design Bases Accident Turbine Building High Energy Line Break (HELB). I do not feel the nuclear safety concern has been addressed by the Region IV office in a rigorous enough manner, which is absolutely necessary to ensure nuclear safety and to protect the health and safety of the public and environment. In my opinion, the nuclear safety concern is still unresolved, because the Licensee's calculation appears to continue to use non-conservative methodology, rather than using accepted forms of ultimate stress behavior at levels high enough to ensure that complete panel failure occurs. Complete failure must be proven to occur in order to assure that the siding panel blowout occurs at, or below, the differential pressure levels assumed in other critical analyses. If the actual failure pressure is higher than assumed, redundant critical safety equipment may be damaged or destroyed, resulting in a nuclear release with an increase in dose consequences from this postulated accident. The latest values for failure pressure do not appear to be any greater than the previous values, which were based on the use of minimum material yield strength and Code-based reasoning. If the Licensee used a "greater-than-yield strength” methodology, the new analysis should have resulted in substantially higher failure pressures than the previous analyses. This leads me to believe that the current calculations are also non-conservative and technically inadequate. Any use of yield-based methodology is inherently non-conservative when actual failure must be ensured by the installed configuration.
To help understand the reasoning behind this nuclear safety concern, l have provided the following background information.
Cooper Nuclear Station TB HELB Design and Licensing Bases
Cooper Nuclear Station (CNS) was licensed to operate based on design aspects that reduced the likelihood of a steam environment entering Control Building critical areas from a Design Basis Accident Turbine Building High Energy Line Break (HELB). Several important design analyses were performed to address issues identified in the Giambusso letter regarding postulated pipe breaks outside of containment. (The Giambusso letter is cited as a reference in NUREG 0800 Section 3.6.1, Rev 2). This important document was not issued until well after the Turbine Building structure was fully erected, and no original design configuration was provided with "siding panel failure" in mind. CNS responded to the Giambusso letter in FSAR (Final Safety Analysis Report) Amendments 20 and 25. As part of the CNS FSAR Amendment 25 response, the licensee committed to the installation of four Steam Exclusion Boundary (SEB) doors, or "blast doors", to protect the Control Room and operators (along with other Control Building critical areas) from the steam environment resulting from a Turbine Building HELB. Installation of these pressure-qualified doors was one of the last action items required before the licensee was given their SER and allowed initial plant startup. These blast doors were designed to withstand a peak pressure of 0.56 psid, which was based on assuming that the Turbine Building siding panels "blew out" at 0.50 psid. Siding failure at 0.50 psid, and peak building pressure of 0.56 psid are thus Design Basis values. However, there are [12 designated blowout panels in the CNS Turbine Building siding system for relief of HELB pressurization, so these Design Basis values may not be achievable.
In 1973, during CNS plant construction, some exterior metal siding panels blew off the Turbine Building superstructure due to high winds. The plant management contacted the metal siding manufacturer, and the manufacturer came up with a revised design for fastening the metal siding to the supporting structure, and tested this configuration to show that it could withstand approximately 0.54 psid (which is about 78 psf). The manufacturer also proposed a second design configuration that they stated would withstand an even higher differential pressure, but they did not test that configuration to failure. Documentation shows that this second, more robust, configuration was actually installed on the Turbine Building, making the siding strong enough to easily withstand more than 0.54 psid. In my opinion, taking credit for Turbine Building panels blowing out at less than 0.50 psid is incomprehensible. I do not believe the current calculations prove that the Turbine Building siding system failure pressure is within the plant's design and licensing bases.
CNS Engineering Analyses
In 2003 an engineering analysis was performed that calculated the Turbine Building siding support girts could be assumed to fail at approximately 1.0 psid, rather than at 0.50 psid. This analysis was later revised to only 0.30 psid, by using inappropriate minimum yield strength methodology instead of using ultimate strength methodology. An independent contractor reviewed the calculation revision that derived 0.30 psid, and stated that an assured failure at 1.5 psid would be more realistic. The plant rejected these independent reviewers comments, and maintained that 0.30 psid was accurate as the siding system failure pressure. During this time period, it was also identified that another nuclear power plant had discovered a similar problem with their Turbine Building metal siding system failure assumptions. That plant installed modified blow out panels in order to ensure that the HELB pressures were adequately relieved (vented). CNS appears to have ignored the potential similarities between this "other plant” and the CNS configuration.
As another point of reference, in 2011, a bounding Turbine Building HELB computer model showed that if there was no panel blowout (no adequate venting/relief), peak pressures could reach as high as approximately 12 psid, which is well over the blast door design pressure of 0.56 psid. Significant venting must occur for the peak building pressures to remain below the Design Basis value of 0.56 psid. Such venting is only possible by the complete failure of Turbine Building siding panels and/or supporting members, and by complete separation of those failed panels from the building structure. Any analyses must therefore use conservative (high) material strength values, and actual failure-based methodology.
The Region lV office has recently evaluated a new Licensee calculation that was prepared in 2013. The Region IV response letter to me states that the Licensee used plastic theory to determine the load limits for the Turbine Building siding system and the maximum differential pressure it can withstand. However, it is highly suspicious that the new calculation results in a differential pressure that is roughly the same as the previous calculation, which used the non conservative yield strength methodology. After my repeated challenges, the Region IV office finally identified the use of yield-based methodology as an error in 2012, which prompted the new calculation to be completed by the Licensee in 2013.
In my opinion, the plant may still be operating in an unsafe and unanalyzed condition. A Turbine Building HELB could easily result in peak pressures higher than the original design and licensing basis conditions, which could adversely affect the 0.56 psid designed blast doors that protect the plant operators and critical safety related equipment. Other critical safety related equipment is also at risk, because these components are NOT protected by any "blast doors". Standard architectural doors currently separate the Emergency Diesel Generators and Critical Switchgear Rooms from the Turbine Building HELB environment.
My ongoing concern is that the plant is in an unanalyzed condition and outside the design and licensing bases. Instead of promptly correcting this deficiency, the plant has simply developed a new calculation that, in my opinion, remains inadequate. The NRC Region IV office stated after their review; "this calculation used a different methodology than was used previously in Calculation NEDC 03-005
Thank you for your time.Respectfully,Enclosures:1.)2.) NRC RIV Letter 12-16-133.) NRC RIV Letter 8-7-14CC:Senator E.Markey w/enc.Dr. Sam Armijo, Retired NRC ACRS Chairman w/enc. Senator D. Fischer *Senator M. Johanns *Honorable A. Smith *David Loch baum *
NE Gav. D. * *Copies of enclosures are available upon request.
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