ML19317D487
| ML19317D487 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 10/23/1979 |
| From: | Reid R Office of Nuclear Reactor Regulation |
| To: | Parker W DUKE POWER CO. |
| Shared Package | |
| ML19317D489 | List: |
| References | |
| NUDOCS 7912060750 | |
| Download: ML19317D487 (4) | |
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION E
WASHWGTON, D. C. 20066 e
%.... f October 23, 1979 Dockr,Nos. 50-269 50-270 and 50-287 Mr. William O. Parker, Jr.
Vice President - Steam Production Duke Power Company P. O. Box 2178 422 South Church Street Charlotte, North Carolina 28242
Dear Mr. Parker:
RE:
Containment Purging and Venting During Nomal Operation By letter dated November 29,1978, ':he Commission (NRC) requested all licensees of operating reactors to respond to generic concerns about containment purging or venting during nomal plant operation. The generic concerns were twofold:
(1) Events had cccurred where 1icensees overrode or bypassed the safety actuation isolatio:1 signals to the containment isolation valves.
These events were detemined to be abnomal occurrences and reported to Congress in January 1979.
(2) Recent licensing reviews have required tests or analyses to show that containment purge or vent valves would shut without degrading con-tainment integrity during the dynamic loads of a design ba:is loss of coolant accident (DBA-LOCA).
The NRC position of the November 1978 letter requested that licensees l
take the following positive actions pending completion of the NRC review:
l (1) prchibit the override or bypass of any safety actuation signal which would affect another safety actuation signal; the NRC Office of Inspection and Enforcement would verify that administrative controls prevent improper manual defeat of safety actuation signals, and (2) cease purging (or venting) of centainment or limit purging (or venting) to an absolute minimun, 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 CSS 5 4, which have effectively classed the purge and vent valves as
" active" invcking the operacility assurance program of SRP 3.9.3.
ihe NRC staff has made site visits to several facilities, has met with licensees at Sethesda, Maryland, and has held telecon conferences with many other licensees and met with some valve manufacturers. During these discussicrs, the NRC staff has stressed that positive actions must be taken as noted aoove to assure that containment integrity would be maintained l
in tne event o# a CBA-LOCA.
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, As a result of these actions, we have learned from several licensees 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 performance under the DBA-LOCA condition.
Recently, a report under 10 CFR Part 21 was received by the NRC from the manufacturer of butterfly valves which are installed in the primary containment at the Three Mile Island Unit 2 Nuclear Station. These butterfly valves are used for purge and exhaust purposes and are required to operate during accident conditions. The report discusses the use of an unqualified solenoid valve for a safety-related valve function which requires operation under accident conditions. The solenoid valve is used to pilot control the pneumatic valve actuators which are installed 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 advised 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 submittals dated January 5 and September 25, 1979 and the infomation 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 Operacility of Purge and Vent Valves" were provided by separate letter
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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 prcmpt response to this letter is required.
In accordance with 10 CFR 50.54(f), you are requested
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-3 to infonn us in writing within 45 days of receipt of this letter of your commitment to operate in confonnance with the enclosed interim position and to provide us with infonnation which demonstrates that you have initiated the purge and vent valve operability verification en an expedited basis. The information provided in your response: will enable us to determine whether or not your license to operate Oconee Units Nos.1, 2 and 3 should be modified, suspended, or revoked.
Sincerely, ert W. Reid, Chief Operating Reactors Branch #4 Division of Operating Reactors
Enclosure:
Interim Position for Containment Purge and Vent Valve Operation cc: w/ enclosure See next page
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Duke Power Company cc:
Mr. William L. Porter Duke -Power Comoany Post Of fice Box 2178 422 South Church Street Charlotte, North Carolina, 25242 J. Michael McGarry, III, Esquire DeBevoise & Libernan 700 Shorenam Building 806 15th Street, N.W.
Wasnington, D. C.
20005 U. S. Nuclear Regulatory Commission Region II Office of Inspection and Enforcement ATTN: Mr. Francis Jape P. O. Box SS Seneca, South Carolina 29678 Mr. Robert B. Borsum Babcock & Wilcox Nuclear Power Generation Division Suite 420, 7735 Old Georgetown Road Bethesda, Maryland 20014 Manager, LIS NUS Corporation 2536 Countryside Soulevard Clearwater, Florida 33515 Oconee Public Library 201 South Spring Street Walhalla South Carolina 29691
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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 Noverter 1978 letter justifying your proposed operational mode. The revised restrictions can be established separately for each system.
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Whenever the containment integrity is required, emphasis should be placed on operating the containment in a passive mode as much as possible and on limiting all purging and venting times to as low as achievable.
To justify venting or purging, there must be an established need to improve working conditions to perfom a safety related surveillance or safety related maintenance procedure.
(Examples of improved working conditions would include deinerting, reducing temperature *, humidity *,
and airtorne activity sufficiently to pemit efficient perfomance 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 greate6 than 3" nominal diameter used for containment purge and venting operations are operable under the nost severe design basis accident flow condition loading and can close within the time limit stated in your Technical Specifications, design criteria or operating paedures. The operability of butter-fly valves may, on an interim basis, be demonstrated by limiting the valve to me no more than 30* to 50' open (90* being full ocen). 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 danaged 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 tne containment ventilation isolation signals to ensure that, as a minimum, at least one of the automatic safety injection actuation signals is uninhibited and operaDie to initiate valve closure when any other isolation signal may be blocked, reset, or overridden.
- Only wnere temperature and humidity controls are not in the present design.
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