ML19347E364
| ML19347E364 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 04/20/1981 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| Shared Package | |
| ML19347E365 | List: |
| References | |
| NUDOCS 8104270144 | |
| Download: ML19347E364 (7) | |
Text
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O 7590-01 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of
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VIRGINIA ELECTRIC AND POWER COMPANY
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) Docket No. 50-338 (florth Anna Power Station,
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Unit No.1)
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ORDER FOR MODIFICATION OF LICENSE I
The Virginia Electric and Power Company (the licensee) holds Facility Operating License No. NPF-4, which authorizes the licensee to operate the North Anna Power Station, Unit No.1, (the facility) at power levels not in excess of 2775 megawatts (thermal) rated power. The facility, which is loct ed at the licensee's site in Louisa County, Virginia is a pressurized water reactor (PWR) used for the commercial generation of electricity.
II The Reactor Safety Study (RSS), WASH-1400, identified in a PWR an inter-system loss of coolant accident (LOCA) which is a significant contributor to risk of core melt accidents (Event V). The design examined in the RSS contained in-series check valves isolating the high pressure Primary Coolant System (PCS) from the Low Pressure Injection System (LPIS) piping. The scenario which leads to the Event V accident is initiated by the failure of these check valves to function as a pressure isolation barrier. This causes an overpras3urization and rupture of the LPIS low pressure piping ei-h res ts in a LOCA that bypasses containment.
0104270V4t
7590-01
. In order to better define the Event V concern, all light water reactor licensees were requested by letter dated February 23,196J, to provide the following in accordance with 10 CFR 50.54(f):
1.
Describe the valve configurations and indicate if an Event V isolation valve configuration exists within the Class I boundary of the high pressure piping connecting PCS piping to low pressure system piping; e.g., (1) two check valves t
in series, or (2) two check valves in series with a motor operated valve (MOV);
2.
If either of the above Event V configurations exist, indicate whether continuous surveillance or periodic tests are being perfomed.on such valves to ensure integrity.
Also indicate whether valves have been known, or found, to lack l
integrity; and 3.
If either of the above Event V configurations exist, indicate whether plant procedures should be revised or if plant nodifications should be made to increase reliability.
In addition to the above, licensees were asked to perform individual check valve leak testing prior to plant startup after the next scheduled outage.
By letter dated March 14, 1980, you responded to our February letter.
Based unon the NRC review of this response as well as the review of previously docketed information for your facility, I have concluded in consonance with the attached Safety Evaluation ( Attachment 1) that one or more valve configura-tion (s) Of cnneern exist at the facility. The attached Technical Evalvetien T,acort (TER) ' At:achnent 2) provides, in Section 4.0, a ubalation of the subject valves.
7590-01
., The staff's concern has been exacerbated due not only to the large number of plants which have an Event V configuration (s) but also because of recent unsatisfactory operating experience. Specifically, two plants have leak tested check valves with unsatisfactory results. At Davis-Besse, a pressure isolation check valve in the LPIS failed and the ensuing investigation found that valve internals had become disassembled. At the Sequoyah Nuclear Plant, two Residual Heat Removal (RHR) injection check valves and one RHR recirculation check valve failed because valves jammed open against valve over-travel limiters.
It is, therefore, apparent thit when pressure isolation is provided
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by two in-series check valves and when failure of one valve in the pair can go undetected for a substantial length of time, verification of valve integrity is required. Since these valves are important to safety, they should be tested periodically to ensure low probability of gross failure.
As a result I have determined that periodic examination of check valves must be untiertaken by the licensee as provided in Section III below to verify that each valve is seated properly and functioning as a pressure isolation device. Such testing will reduce the overall risk of an irder-i system LOCA. The testing mandated by this Order may be accomplished by direct volumetric leakage measurement or by other equivalent means l
capable of demonstrating that leakage ifmits are not exceeded in accord-ance with Section 2.2 of the attached TER.
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7590-01 In view of the operating experiences described above and the potential consequences of check valve failure, I have determined that prompt action is necessary to increase the level of assurance that multiple pressure isolation barriers are in place and will remain intact. Therefore, the public health, i
safety and interest require that this modification of Facility Operating License No. NPF f be immediately effective.
III Accordingly, pursuant to Section 1611 of the Atomic Energy Act of 1954, as amended, and the Commission's regulations in 10 CFR Parts 2 and 50, IT IS HEREBY ORDERED THAT EFFECTIVE IMMEDIATELY, Facility Operating License No. NPF-4 is modified by the addition of the following requirements:
1.
Implement Technical Specifications (Attachment 3) which require periodic surveillance over the life of the plant and which specify limiting conditions for operation for PCS pressure isolation valves.
i 2.
If check valves have not been (a) individually tested within 12 months preceding the date of this Order, and (b) found to comply with the leakage rate criteria set forth in the Technical Specifications described in Attachment 3, the MOV in each line shall be closed within 30 days of the effective date of this Order and
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quarterly Inservice Inspection (ISI) MOV cycling ceased until the check l
valve tests have been satisfactorily accomplished.
(Prior to closing the MOV, procedures shall be implemented and operators trained o assure
that the MOV remains closed. Once closed, the MOV shall be tagged closed to further. preclude inadvertent valve opening).
3.
The MOV shall not be closed as indicated in paragraph 2 above unless a supporting safety evaluation has been prepared. If the MOV is in an emergency core cooling system (ECCS), the safety evaluation shall include a determination as to whether the. requirements of 10 CFR 50.46 and Appendix K to 10 CFR Part 50 will continue to be ratisfied with the MOV closed.
If the MOV is not in an ECCS, the safety evaluation shall include a deter-mination as to whether operation with the MOV closed presents an unreviewed safety question as defined in 10 CFR 50.59(a)(2).
If the requirements of 10 CFR 50.46 and Appendix K have not been satisfied, or if an unreviewed safety question exists as defined in 10 CFR 50.59, then the facility shall be shut down within 30 days of the date of this Order and remain shutdown until check valves are satisfactorily tested in accordance with the Techr.f-cal Specifications set forth in Attachment 3.
4.
The records of the check valve tests required by this Order shall be made available for inspection by the NRC's Office of. Inspection and Enforcement.
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7590-01 IV The licensee or any other person who has an interest affected by this Order may request a hearing on this Order within 25 days of its publication in the Federal Register. A request for hearing shall be submitted to the Secretary, U.S. Nuclear Regulatory Commission, Washington,.D.C. 20555.
A copy of the request shall also be sent to the Executive Legal Director at the same address, and to Michael W. Maupin, Esq., Hunton, Williams, Gay and Gibson, P. O. Box 1535, Richmond, Virginia 23212 attorney for the licensee.
If a hearing is requested by a person other than the licensee, that person shall describe, in accordance with 10 CFR 2.714(a)(2), the manner in which his or her interest is affected b[ this Order. ANY REQUEST FOR A HEARING SHALL HOT STAY THE IMMEDIATE EFFECTIVENESS OF THIS ORDER.
If a hearing is requested by the licensee or other person who has an interest affected by this Order, the Comaission will issue an order designating the time and place of any such hearing.
If a hearing is held, the issues to be considered at such a hearing shall be:
(a) Whether the licensee should be required to individually leak test check valves in accordance with the Technical Specifications set forth in Attachment 3 to this Order.
(b) Whether the actions required by Paragraphs 2 and 3 of section III of this Order must bn taken if check valves have not been tested within 12 months preceding the date of this Order.
i 7590-01 7-Operation of the f acility on terns consistent with this Order is not stcyed by the pendency of any proceedings on this Order.
In the event that a need for further action becames apparent, either in the course of proceedings on this Order or any other time, the Director will take appropriate action.
OR THE NUCLEAR REGULATORY COMMISSION
$N]l N
uarrein G.GEisEn'nus,' Director
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Division of Licensing Effective Date: This 20th day of April, 1981 Bethesda, Maryland Attachments:
1.
Safety Evaluation Report 2.
Technical Evaluation Report 3.
Technical Specifications s
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION j,
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WASHINGTON, D. C. 20555 r
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SAFETY EVALUATION REPORT NORTH ANNA POWER STATION, UNIT NO. 1 PRIMARY COOLANT SYSTEM PRESSURE ISOLATION VALVES (WASH-1400, EVENT V) 1.0 Introduction The Reactor Safety Study (RSS), WASH-1400, identified in a PWR an intersystem loss of coolant accident (LOCA) which is a significant contributor to risk of core melt accidents (Event V). The design examined in the RSS contained in-series check valves isolating the high pressure Primary Coolant System (PCS) from the Low Pressure Injection System (LPIS) piping. The scenario which leads to the Event V accident is initiated by the failure of these check valves to function as a pressure isolation barrier. This causes an overpressurization and rupture of the LPIS low pressure piping which results in a LOCA that bypasses containment.
In order to better define the Event V concern, all light water reactor licensees were requested by 10 CFR 50.54(f) letter, dated February 23, 1980, to identify valve configurations of concern and prior valve test results, if any. By letter dated March 14, 1980, the licensee responded to our request and this information was subsequently transmitted to our contractor, the Franklin Research Center, for verification that the licensee had correctly identified the subject valve configurations.
2.0 Evaluation In order to prepare the Technical Evaluation Report (TER) it was l
j necessary that the contractor verify and evaluate the licensee's response to our February 1980 letter. The HRC acceptance criteria used by Franklin were I
baser' on WASH-1400 findings, probabilistic analyses and appropriate Standard l
Review Plan requirements. With respect to the verification of the licensee's l
response to our information request, the Franklin evaluation was based on FSAR information, ISI/IST site visit data, and other previously docketed information.
The attached Franklin TER correctly identifies the subject valve configurations.
3.0 Conclusion Based on our review of the Franklin TER, we find that the valve configurations of concern have been correctly identified.
Since periodic testing of these PCS pressure isolation valves will reduce the probability of an intersystem LOCA we, therefore, conclude that the requirement to test these valves should be incor-porated into the plant's Technical Specifications.
Dated: April 20, 1981
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