ML19257A367
| ML19257A367 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 11/19/1979 |
| From: | Schwencer A Office of Nuclear Reactor Regulation |
| To: | Burstein S WISCONSIN ELECTRIC POWER CO. |
| References | |
| TAC-44877, TAC-44878, NUDOCS 8001030852 | |
| Download: ML19257A367 (5) | |
Text
Len
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UNITED STATES
{ )5i 3 i NUCLEAR REGULATORY COMMISSION 3'\\*
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WASHINGTON, D. C. 20555 Sk2i i
b November 19, 1979
+
Docket Nos. 50-266 and 50-301 Mr. Sol Burstein Executive Vice President Wisconsin Electric Power Company 231 West Michigan Street Milwaukee, Wisconsin 53201
Dear Mr. Burstein:
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 normal 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 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 basis loss of coolant accident (DBA-LOCA).
The NRC position of the November 1978 letter requested that licensaes 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 Enforcement 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, has met with licensees 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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8001030 2
Mr. Sol Burstein November 19, 1979 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 i
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 l
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 performance 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 compensatory interim measures to minimize the problem.
In light of the information gained during our reviews of your submittals dated January 16, April 11, July 3, August 10, and September 6,1979 and the information cited above, we believe an additional interim co mitment from you is required at this time. This is the case, even though you have committed to keeping the purge valves closed above cold shutdcwn (LER of April 11, 1979 and letter of Septerter 6,1979).
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 ope, ating 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 1668 211
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t i
Mr. Sol Burstein November 19, 1979 t
to inform us in writing within 45 days of receipt of this letter of your comitment to operate in confermance 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 determine whether or not your license to operate Point Beach, I
Unit Nos.1 and 2 should be modified, suspended, or revoked.
I S neerely, ht(&d/$V A. Schwencer, Chief Operating Reactors Branch #1 Division of Operating Reactors
Enclosure:
Interim Position for Containment Purge and Vent Valve Operation cc:. w/ enclosure See next page 1668 212
e
c.~ Sol Burstein 1.isconsin Electric Power Company November 19, 1979 cc:
'.r. Bruce Churchill, Esquire Shaw, Pittman, Potts and Trowbridge 1800 M Street, N.W.
Washington, D. C.
20036 Document Department University of Wisconsin Stevens Point Library Stevens Point, Wisconsin 54481 Mr. Glenn A. Reed, Manager Nuclear Operations Wisconsin Electric Pow'er Company Point Beach Nucleir Plant 6610 Nuclear Road Two Rivers, Wisconsin 54241 1668 213
d INTERIM POSITION FOR CONTAINMENT PURGE AND VENT VALVE OPERATION PENDING RESOLUTION OF ISOLATION VALVE OPERABILITY Once the cenditions 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 Novenber 1978 let:er justifying your proposed operational mode.
The revised restrictions can be established separately for each system.
1.
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 perform a safety related surveillance or safety related maintenance procedure.
(Examples of improved working conditions would include deinerting, reducing tenperature*, 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 operat'e 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 minir:um, 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 wnere temperature and humidity controls are not in the present design.
1668 214