ML20003J100
| ML20003J100 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 04/20/1981 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Maine Yankee |
| Shared Package | |
| ML20003J096 | List: |
| References | |
| NUDOCS 8105080448 | |
| Download: ML20003J100 (6) | |
Text
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O UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of
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MAINE YANKEE ATOMIC POWER COMPANY Docket No. 50-309 (Maine Yankee Atomic Power Station} }
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ORDER CONFIRMING LICENSEE'S C05ITNENTS FOR EVENT V 5
The Maine Yankee Atomic Power Company (the licensee) holds Facility Operating License No. DPR-36, which authorizes the licensee to operate the Maine Yankee Atomic Power Statien (the facility) at power levels not in excess of 2630 megawatts thermal. The facility, which is located at the licensee's site in Lincoln County, Maine is a pressurized water reactor (P J )
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used for the comercial 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-seric: check valves isolating' the high pressure Primary Coolant The System (PCS) from the Low Pressure Safety Injecticn (LPSI) system pipinc;.
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 overpresseridation and rupture of the LPSI icw pressure piping l
which results in a LOCA that byoasses containment.
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2 In order to better define the Event V concern, all light water reactor licensees were requested by letter dated February 23, 1980, to provide tne following in accordance with 10 CFR 50.54(f):
1.
Describe the valve configurations and indicata if
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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 in series, or (2) two check valves in series with a motor operated valve (MOV);
2.
If either of the above Event V configurations exists, indicate whether continuous surveillance or periodic tests are being performed on such valves to ensure integrity.
Also indicate whether valves have been known, or found, to lack integrity; and 3.
If either of~the above Event V configurations exists, indicate whether plant procedures should be revised or if plant modifications should be made to increase reliability.
In addition to the above, licensees were asked to perform individuhl check valve leak testing prior to plant startup after the next scheduled outage.
By letter dated March 13, 1980, the licensee responded to our February letter. Based upon the NRC review of this response as well as the review of previously docketed information for the facility, I have concluded that one valve configuration of concern exists at the facility.
3 The staff's concern has been exacerbated due net cnly to the large number of plants which have an Event V configuratien but also because of recent unsatisfactory operating experience. Specifically, two plants have leak tested check valves with unsatisfactory results. At Davis-Besse, a pressure isolatica check valve in the LPSI 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 that when pressure isolation is provided by two in-series check valves and when fai. lure 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 icw probability of gress failure. As a result, I have detendined that actions must be un'dertaken by the licenses to verify that each valve is seated properly and functiening as a pressure isolation device.
Such testing will reduce the overall risk cf an intersystem LOCA.
III The licensee's sub6ittal dated March 9,1931, ccmmitted to implement each of the acticns s;ecified in Secticn IV. h's have reviewed che licensee's submittal and determined that it is accectable because:
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1.
The licensee's action ensures two in a series closed valves that provide a pressure barrier that isolates the high Pressure Primary Coolant System from the Low Pressure Safety Injection (LPSI) system.
2.
The licensee's actions ensure the pressure boundary by leak testing the valves periodically.
Acccrdingly, I have determined that these ccamitments are required in the interest of public health and safety and, therefore, should be ccnfir=ed by an immediately effective order.
IV Accordingly,pursuanttoShetions10'and1511oftheAtomicEnergy 3
Act of 1954, as amend'ed, the Commissien's regulatiens in 10 CFR F:rts 2 and 50, IT IS HEREEY ORDERED EFFECTIVE It'. MEDIATELY THAT the license be amended to include the following conditions:
1.
The licensee will assure that MOV's LSI-M 11, 21 and 31 remain in their normally closed position during power operatien by modifying existing surveillance crocedures to include menthly meni cring of the dcwnstream check valve, affix a CAUTION tag to each valve switch, and provide training to the opera:crs relative to the reisens for these modificattens including relief frem.cnthly cerformance testing cf these valves. These actions are receirec until the "aine Yankee Atemic Fo..er Station is shu dcwn fer :.e Ecrir; 19El Cycle 5 refuelir.g.
5-I e
2.
Frier to returning to pewer after the Spring 1931 Cycle 5 refueling, the li:ensee shall (1) instail an additienal leak tight check valve and its associated leak testing capabilities between the two existing LPSI check valves and (2) obtain approval for apprcpriate technical specificatiens for periedic surveillance to verify the integrity of the L?SI check valves.
V Any persen who has an interest affected by this Order may request a hearing en this Order within-25 days of its publicatter: in the Federal Reciscer. A request for a hearing shall be submitted to the Director, Office of Nuclear Reacter Regulation, U.S. Nuclear Regulatory Ccmmission, Washington, D.C.
205E5. A ce;y cf the request shall also be sent to the Secretary f the Cc==issicn and the Executive Legal Directcr at the same address.
If a hearing is requested by a persen other than the licensee, that persen shall describe, in accordance with 10 CFR 2.714(a)(2) the nature of the persen's interest and m;y...,g...
- g the =anner in which that interest is affected by this Order.
n:4 :si rv A HEARING SHALL NOT STAY THE IMMEDIATE EFFECTIVENESS OF THIS CROER.
If a hearing is held concerning this Crier, : e iss e :: te c: sitt.i:
a: ta,e heari*g sha'.I be whe her, On the basis cf :?.e irf0rCati:T. se: fcrth 4'-
. c, 6-Sections II and TII of this Order, the license should be modified as set forth.
in Section IV of this Order.
R THE NUCLEAR REGULATORY COMMISSION O
urrellu.{Isennu, 1 rect r Divisicn of.icensing Office of Nuclear Reactor Regulation Dated at Bethesda, Maryland this 20th day of April
, 1981 e
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