ML19254F773
| ML19254F773 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 10/23/1979 |
| From: | Schwencer A Office of Nuclear Reactor Regulation |
| To: | Peoples D COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 7911190002 | |
| Download: ML19254F773 (5) | |
Text
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[pa areg o UNIT ED STATES g
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NUCLEAR REGULATORY COMMISSION g
E WASH WGTON, D. C. 20555
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OCTOBER 2 ; 1979 D**}D
- ]D h]Y Docket Nos. 50-295 WJuuSu.
and o o Ju Mr. D. Louis Peoples Director of Nuclear Licensing Commonwealth Edison Company Post Office Box 767 Chicago, Illinois 60690
Dear Mr. Peoples:
RE:
Containment Purging and Venting During Normal Operation By letter dated November 28, 1978, the 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 occurred where licensees overrode or bypassed the safety actuation isolation signals to the containaent isolation valves.
These events were determined to be abnorac.1 occurrences and reported to Congress in January 1979.
(2) Recent licensing reviews have required tests or analyses to show that contdinment purge or vent valves would shut without degrading con-tainaent integrity during the dynanic loads of a desicn basis loss of cool ant accioent (DBA-LCC A).
The MC position of the NoveiiDer 1970 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 affect another safety actuation signal; the NRC Office of Inspection and Enforcenent 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 nininun, 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 containnent isolation valves would shut under postulated DBA-LOCA condition. The NRC positions were anplified 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, has net with licensees at Bethesda, Maryland, and has held telecon conferences with many other licensees and net with some valve manufacturers. During these discussions, the NRC staff has stressed that positive actions nust 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. D. Louis Peoples OCTOBER
. 1975 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 installM in the primary containment at the Three Mile Island Unit ? 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 pneunatic valve actuators which are installed on the containment ventilation butterfly valves at this facility. Your re-evaluation of valve perfurmance for conditions noted in the previous paragraph must consider the concerns identified in IE Bulletin 79-01 A.
As the NRC review progresses, licensees which might have electrical override circuitry problems are being advised not to use the override and to take coopensatory interin measures to minimize the problem.
In light of the information gained during our reviews of your submittals dated January 2, July 2, July 5, July 30, September 25 and October 4,1979 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 interin NRC staff position.
In addition, our recently developed " Guidelines for Denonstration 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 I
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 1353 101
Mr. D. Louis Peoples OCTOBER 4 :, 7379 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 infomation 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 detemine whether or not your license to operate Zion Station Unit Nos. I and 2 should be modified, suspended, or revoked.
Sincerel,
'?kttV/W W A.,Schwencer, Chief Oparating Reactors Branch #1 Division of Operating Reactors
Enclosure:
Interim Position for Containment Purge ano Vent Valve Operation cc: w/ enclosure See next page i
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i Mr. 3. Louis Peoples Connonwealth Edison Company OCT0eER to79 cc:
Robert J. Vollen, Esquire 109 fiorth Dearborn Street Chicago, Illinois 60602 Dr. Cecil Lue-Hing Director of Research and Development Metropolitan Sanitara District of Greater Chicago 100 East' Erie Strc*t Chicago, Illinois 60611 Zion-Benton Public Library District 2600 Emmaus Avenue Zion, Illinois 60099 Mr. Phillip P. Steptoe Isham, Lincoln and Beale Counselors at Law One First fiational Plaza 42nd Floor Chicago, Illinois 60603 Susan fl. Sekuler, Esquire Assistant Attorney General Environmental Control Division 188 West Randolph Street, Suite 2315 Chicago, Illinois 60601 1353 103
INTERIM POSITION FOR CONTAINMENT PURGE AND VENT VALVE OPEEATION PENDING RESOLUTION OF ISOLATION VALVE OPERABILITY Once the conditions listed below are met, restrictions on use of the containment purge and vent systen isolation valves will be revised based on our review of your responses to the November 1978 letter justifying your proposed operational mode. Tha revised restrictions can be established separately for each system.
l l
1.
Whenever the containment integrity is required, emphasis should be placed on operating the containnent in a pass've mode as much as possible and on limiting all purging and venting tine: to as low as achievable.
To justify venting or purging, there must be an established need to 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.
Mainta'in the cor.tainment 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 Specificattns, 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 l
maximum opening shall be determined in consultation with the valve l
suppl ier. The valve opening must be such that the critical valve parts will not be damaged by DBA-LOCA loads and that the valve will i
I tend to close when the fluid dynamic fon:es 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 nay be blocked, reset, or overridden.
- Or.ly ur.ere ten;erature and humidity control s are not in the present design.
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