ML17059B709
| ML17059B709 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 09/12/1997 |
| From: | Thadani A NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Sylvia B NIAGARA MOHAWK POWER CORP. |
| References | |
| EA-96-079, EA-96-79, NUDOCS 9709170212 | |
| Download: ML17059B709 (12) | |
Text
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 205554001 September 12, 1997 EA 96-079 Hr.
B. Ralph Sylvia, Executive Vice President Generation Business Group
& Chic'f Nuclear Officer Niagara Mohawk Power Corporation Nuclear Learning Center 450 Lake Road Oswego.
New York 13126
Dear Mr. Sylvia:
This is a response to a July 16, 1996, letter, from Niagara Mohawk Power Corporation (NMPC),
a transcribed public meeting held between NHPC and the Nuclear Regulatory Commission (NRC) at the NRC Headquarters offices on January 6,
- 1997, and a February 19, 1997, letter submitted by Winston 8 Strawn on behalf of NHPC.
The subject of these letters and this meeting was the repor tabi lity of pressure relief panels on the Nine Mile Point, Unit 1 (NHP-1) reactor and turbine buildings being outside of their design basis'.
In October
- 1993, NMPC determined that oversized bolts (larger than specified in the plant's design) had been installed in the blowout panels for the reactor and turbine buildings.
As a result, NHPC calculated that the blowout panels'elief function for both buildings exceeded the 45 pounds per square foot (psf)'s stated in the Final Safety Analysis Report (FSAR).
Specifically, the NHP-1 FSAR provides in Section III.A.l. that the purpose of the Turbine Building blowout panels was to prevent failure of the superstructure due to steam line break.
This pressure relief function is accomplished by a wall area of 1800 square feet being attached to the superstructure with bolts that will fail due to an internal pressure of
'his issue was originally cited as a single Severity Level IV violation of the requirements of 10 CFR 50.72 and 10 CFR 50.73 in a Notice of Violation (Notice) issued June 18, 1996.
In a letter dated July 16,
- 1996, NHPC denied the violation (Violation II.B in the June 18, 1996, Notice).
In a December 3,
1996. letter, the NRC informed NHPC that an adequate basis for the NRC to withdraw the violation had not been provided.
Accordingly, the violation was not withdrawn.
'he blowout panels initiate the internal pressure relief function and prevent structural failure of the buildings.
NHPC calculated the relief functions imtiate at approximately 63 psf and 60 psf for the reactor and ~ ~ 0 lllllllllillllllllllllllllllllllllllllll
Niagara Mohawk Power Corporation approximately 45 pounds per square foot, thus relieving internal pressure.
Wall or building structure failure would occur at an internal pressure in excess of 80 pounds per square foot.
Additionally.Section VI.B.1. states that pr essure relief for the Reactor Building is provided to prevent collapse of the superstructure due to a break of an emergency cooling system, or other primary coolant system line in the reactor building.
This pressure relief function is accomplished by a wall area of approximately 1800 square feet being attached to the superstructure with bolts that are designed to fail with an internal building pressure of'pproximately 45 pounds per square foot of wall area.
Relief of pressure through this area in case of an energy release will prevent excessive internal pressure on the superstructure walls, roof and their supports which would fail at an internal pressure in excess of'0 pounds per square foot.
4 NMPC's contention-is that the design bases for internal building pressure is only to provide pressure relief at or below 80 psf.
However, the NRC concluded that the design bases include both the 80 psf building pressure relief and the 45 psf blowout panel pressure.
The 45 psf blowout panel pressure provides the necessary margin to prevent the building's internal pressure from exceeding 80 psf.
Absent the 45 psf blowout panel pressure or any other blowout panel pr essure, the design bases of the buildings might not have been acceptable when previously reviewed by the NRC.
Regardless of the acceptability of the blowout panel pressure, there should be no question that the blowout panel pressure was a technical consideration when evaluating the design bases; therefore.
the NRC 'considers the blowout panel pressur e to be part of the design bases.
In general, the design bases include any information that was used to determine the acceptability of the nuclear power plant design.
10 CFR 50.2 defines design bases as follows:
Oesign bases means that information which identifies the specific f n by a structure.
- system, or component of a facility, and the specific values or ranges of'alues chosen for control ling parameters as These values may be (1) restraints derived from generally accepted "state of the art" practices for achieving functional goals, or (2) requirements derived from analysis (based on calculation andlor experiments) of the effects of a postulated accident for which a structure,
- system, or component must meet its functional goals.
(emphasis added)
Niagara mohawk Power Corporation The NRC has concluded that the oversizing of the blowout panels'olts affected all the blowout panels and, therefore, the entire function to be performed of protecting the buildings from superstructure damage in an overpressure condition.
- Further, the NRC determined that the blowout panel pressure of 45 psf establishes the reference for the acceptability of the facility's design.
Therefore, based on our analysis, the NRC has concluded that this event was reportable.
The description of this issue involving the blowout panels in the reactor and turbine buildings meets the reporting requi rements of both
~ 10 CFR 50.72(b)(1)(ii)(B) and 10 CFR 50.73(a)(2)(ii)(B), and, therefore, violations occurred.
Accordingly, the NRC has concluded that citations are warranted and is denying NHPC's request that the violation be withdrawn.
Therefore, you are required to respond to the violation cited in the June 18, 1996. Notice, within 30 days of the date of this letter, by providing the corrective steps taken to avoid further violations.
The NRC recognizes the issues raised by NNPC concerning the undesirability of one hour reports for matters of'elatively low safety significance.
While overreporting information may, in certain circumstances.
not be desirable. it is nonetheless important for the NRC to receive necessary information in a timely manner, in order to support decisions on actions pertaining to public health and safety.
For that reason.
the NRC would rather receive more information, reported pursuant to the requirements. of 10 CFR 50.72, than less.
However, the staff acknowledges that some information currently required to be reported within one hour may more appropriately be reported at a later time..
In that regard.
the staff is continuing to review this generic matter.
In accordance with 10 CFR 2.790 of the NRC's "Rules of Practice,"
a copy of this letter and its enclosure will be placed in, the NRC's Public Document Room.
Sincerely.
Docket No. 50-220 License No.
DPR-63 Ashok C. Thadani Acting Deputy Executive Director for Regulatory Effectiveness cc:
See'ext page
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Niagara Mohawk Power Corporation 4
CC:
R. Abbott, Vice President 8 General Manager
- Nuclear C'. Terry, Vice President-Nuclear Engineering H. McCormick, Vice President
- Safety Assessment and Support N. Rademacher, Unit 1 Plant Manager J.
Conway. Unit 2 Plant Manager D. Wolniak. Manager, Licensing J.
- Warden, New York Consumer Protection Branch G. Wilson, Senior Attorney N. Reynolds, Winston and Strawn M. Wetterhahn, Winston and Strawn Director, Electric Division, Department of Public Service, State of New York 1
C. Donaldson, Esquire, Assistant Attorney General, New York Department of Law J.. Vinquist, MATS, Inc.
P.
- Eddy, Power Division, Department of Public Service, State of New York State of New York SLO Designee
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Niagara Mohawk Power Corporation PUBLIC SECY CA
- LJCallan, EDO
- DRoss, AEOD OE:EA (2)
NUDOCS Nuclear Safety Information Center (NSIC)
NRC Resident Inspector
- Nine Mile
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Niagara Mohawk Power Corporation DISTRIBUTION:
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- DRoss, AEOD OE:EA (2)
NUDOCS Nuclear Safety Information Center (NSIC)
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