ML19260B589
| ML19260B589 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 10/09/1979 |
| From: | Schwencer A Office of Nuclear Reactor Regulation |
| To: | Groce R YANKEE ATOMIC ELECTRIC CO. |
| References | |
| NUDOCS 7912100413 | |
| Download: ML19260B589 (5) | |
Text
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UNITED STATES g
NUCLEAR REGULATORY COMMISSION E
WASHINGTON, D. C. 20555 November 9, 1979 m.
Docket No. 50-271 Mr. Robert a. Groce Licensing Engineer Yankee Atomic Electric Company 20 Turnpike Road Westboro, Massachusetts 01581,
Dear Mr. Groce:
RE:
Containment Purging and Venting During Normal Operation By letter dated November 29, 1978, the Commission (NRC) requested all licensees of opeating reactors to respond to generic concerns about containment purging or venting during nomal plant operation. The generic concerns were twofold:
(1) Events had occurred where licensees overrode or bypassed the safety actuation isolation signals to the containment isolation valves.
These events were determined to be abnormal occurrences 'nd reported to Congress in January 1979.
(2) Recent licensing reviews have required tests or ani.iyses to show that containment purge or vent valves would shut without degra;ing con-tainment integrity during the dynamic loads of a design basis loss of coolant accident (DBA-LOCA).
The NRC position of the November 1978 letter requested that licensees take the following positive actions pending completion of the NRC review:
(1) prohibit the override or bypass of any safety actuation signal which would Nfect another safety actuation signal; the NRC Office of Inspection and Enfon:ement would verify that administrative controls prevent improper manual defeat of safety actuation signals, and (2) cease purging (or venting) of containment or limit purging (or venting) to an absolute minimum, not to exceed 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year. Licensees were requested to demonstrate (by test or by test and analysis) that containment isolation valves would shut under postulated DBA-LOCA condition. The NRC positions were amplified by citation (and an attached copy) of our Standard Review Plan (SRP) 6.2.4 Revision 1 and the associated Branch Technical Position CSB 6-4, which have effectively classed the purge and vent valves as
" active" invoking the operability assurance program of SRP 3.9.3.
The NRC staff has made site visits to several facilities, hat met with icensees at Bethesda, Maryland, and has held telecon conferences with many other licensees and met with some valve manufacturers. During these discussions, the NRC staff has stressed that positive actions must be taken as noted above to assure that containment integrity would be maintained in the event of a DBA-LOCA.
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Mr. Robert H. Groce i i
As a result of these actions, we have learned from several licensees l
that at least three valve vendors have reported that their valves may not close against the ascending differential pressure and the resulting dynamic loading of the design basis LOCA. All identified licensees who are affected have proposed to maintain the valves in the closed position or to restrict the angular opening of the valves whenever primary containment integrity is required until a re-evaluation is provided which shows satisfactory valve perfomance under the DBA-LOCA condition.
i Recently, a report under 10 CFR Part 21 was received by the NRC from i
the manufacturer of butterfly' valves which are installed in the primary I
containment at the Three Mile Island Unit 2 Nuclear Station. These butterfly valves are used for purge and exhaust purposes and are required to opera:e during accident conditions. The report discusses the use of an unqualified solenoid valve for a safety-related valve function which requires operation j
under accident conditions. The solenoid valve is used to pilot control the pneumatic valve actuators which are it. stalled on the containment ventilation butterfly valves at this facility.
Your re-evaluation of valve perfomance for conditions noted in the previous paragraph must consider the concerns identified in IE Bulletin 79-OlA.
As the NRC review progresses, licensees which might have electrical override circuitry problems are being ad.. sed not to use the~ override and to take compensatory interim measures to minimize the problem.
In light of the information gained during our reviews of your submittal dated January 9,1979, and the information cited above, we believe an interim commitment from you is required at this time. This is the case, even though you may have proposed Technical Specification changes or other long or short-term measures, which we are reviewing. For your use, we have provided as an attachment an interim NRC staff position.
In addition, our recently developed " Guidelines for Demonstration of Operability of Purge and Vent Valves" were provided by separate letter to licensees of each operating reactor. This letter in no way relaxes any existing licensing requirements for your facility.
Because of the potential adverse effects on the public health and safety which could result from the postulated, DBA-LOCA while operating with open purge or vent valves, we believe your prompt response to this letter is required.
In accordance with 10 CFR 50.54(f), you are requested 1521 181
Mr. Robert H. Groce to infom us in writing within 45 days of receipt of this letter of your commitment to operate in confomance with the enclosed interim position and to provide us with information which demonstrates that you have initiated the purge and vent valve operability verification on an expedited basis. The information provided in your response will enable us to de', ermine whether or not your license to operate Vemont Yankee Nuclaar Power Station should be modified, suspended, or revoked.
Sincerely,
,~
%-/d'*
n' kr Thomas./Ippolito, Chief Operat ng Reactors Branch #3 Division of Operating Reactors
Enclosure:
Interim Position for Containment Purge and Vent Valve Operation cc: w/er:losure See next page 1521 182
^
l Mr. Robert H. Groce.
cc:
Ms. J. M. Abbey John R. Stanton, Director Vermont Yankee Nuclear Power Radiation Control Agency Corporation Hazen Drive 77 Grove Street Concord, New Hampshire 03301 Rutland, Vermont 05701 John W. Stevens Mr. Donald E. Vandenburgh, Conservation Society of Vice President Southern Vermont Vermont Yankee Nuclear Power P. O. Box 256 Corporation Townshend, Vermont 05353 Turnpike Road, Route 9 Westboro, Massachusetts 01 581 Dr. Mars Longley, Director Div. Occupational Health John A. Ritsher, Esquire 32 Saaulding Street Ropes & Gray Barra, Vemont 05641 225 Franklin Street Boston, Massachusetts 02110 New England Coalition on Nuclear Pollution Laurie Burt Hill and Dale Farm Assistant Attorney, General West Hill-Faraway Road Environmental Protection Division Putney, Ver %,t 05346 Attorney General's Office One Ashburton Place,19th Floor Public Service toard Boston, Massachusetts 02108 State of Vermont Ricnard E. Ayres, Esquire 120 State Street Natural Resources Defense Counsel Montpelier, Vermont 05602 hington b.
b05 W. F. Conway, Plant Superintendent Vermont Yankee Nuclear Power Honorable M. Jerome Diamond Corporation P. O. Box 157 Attorney General State of Vermont Vernon, Vermont 05354 109 State Street Pavilion Office Building Mr. Charles Sheketoff Montpelier, Vermont 05602 Assistant Director Vermont Public Interest John A. Calhoun Research Group, Inc.
Assistant Attorney General 26 State Street State of Vermont
. Montpelier, Vermont 05602 109 State Street Pavilion Office Building Brooks Memorial Library Montpelier, Vermont 05602 224 Main Streot Brattleboro, Vermont 05301 Anthony Z. Roisman Natural Resources Defense Council 917 15th Street, N. W.
Washington, D. C.
20005 1521 183
~
INTERIM POSITION FOR CONTAINMENT PURGE AND VENT VALVE OPERATION PENDING RESOLUTION OF ISOLATION VALVE OPERABILITY Once the conditions listed below are met, restrictions on use of the containment purge and vent system isolation valves will be revised based on our review of your responses to the November 1978 letter justifying your proposed operational mode. The revised restrictions can be established separately for each system.
1.
Whenever the containment integrity ;s required, emphasis should be placed on operating the containmen; in a passive mode as much as possible and on limiting all purging and venting times to as low as achievable. To justify ventina or purging, there must he an established need to meet Technical Specifications or improve working conditions to perform a safety related surveillance or safety related maintenance procedure.
(Examples of improved working conditions would include deinerting, reducing temperature *, humidity *, and airborne activity sufficiently to permit efficient performance or to significantly reduce occupational radiation exposures), and 2.
Maintain the containment purge and vent isolation valves closed whenever the reactor is not in the cold shutdown or refueling mode until such time as you can show that:
a.
All isolation valves greater than 3" nominal diameter used for containment purge and venting operations are operable under the most severe design basis accident flow condition loading and can close within the time limit stated in your Technical Specifications, design criteria or operating procedures. The operability of butter-fly valves may, on an interim basis, be demonstrated by limiting the valve to be no more than 30 to 50 open(90 being full open). The maximum opening shall be determined in consultation with the valve supplier. The valve opening must be such that the critical valve parts will not be damaged by DBA-LOCA loads and that the valve will tend to close when the fluid dynamic forces are introduced, and b.
Modifications, as necessary, have been made to segregate the containment ventilation isolation signals to ensure that, as a minimum, at least one of the automatic safety injection actuation signals is uninhibited and operable to initiate valve closure when any other isolation signal may be blocked, reset, or overridden.
- Only where temperature and humidity controls are not in the present design.
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