ML19254F792
| ML19254F792 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 10/30/1979 |
| From: | Reid R Office of Nuclear Reactor Regulation |
| To: | Counsil W NORTHEAST NUCLEAR ENERGY CO. |
| References | |
| TASK-06-04, TASK-6-4, TASK-RR TAC-42588, NUDOCS 7911190030 | |
| Download: ML19254F792 (5) | |
Text
Cu f[
'o UNITED STATES
,y NUCLEAR REGULATORY COMMISSION n
w WASHINGTON, D. C. 20555
....f./
s fg October 30, 1979 Dockets Nos. 50-245 and 50-336 Mr. W. G. Counsil, Vice President Nuclear Engineering & Operations Northeast Nuclear Energy Company P. O. Box 270 Hartford, Connecticut 06101 1
Dear Mr. Counsil:
RE: Containment Purging and Venting During Normal Operation By letter dated November 29. 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 containment isolation valves.
These events were determined 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 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 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.
1353 302 D30 7911190
)
. m.w, n~,..
e....
.... 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 j
containment integrity is required until a re-evaluation is provided which shows satisfactory valve perfomance under the DBA-LOCA condition.
Recently, a report unaer 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 infomation gained during our review of your submittals dated January 2 and 3 and April 27 (two letters),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 Spect-fication changes for Millstone Unit No. 2, committed not to purge Unit No. 2 in Modes 1 through 4 and other long or short-tem measures for both units, 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 Demon-stration 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 Millstone Units Nos.1 and 2 or changes in any way your April 27, 1979 commitment not to purge Millstone Unit No. 2 in Modes 1 through 4.
I Because of the potential adverse effects on the public health and safety which could result from tne 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 303
, to infom us in writing within 45 days of receipt of this letter of your commitment to operate Millstone Unit No.1 in conformance with the i
enclosed interim position and to provide us with infomation which demon-strates that you have initiated the purge and vent valve operability veri-fication on an expedited basis. The information provided in your response will enable us to detemine whether or not your license to operate Millstone Unit No. I should be modified, suspended, or revoked. Because of your April 27, 1979 cmmitment not to purge Unit No. 2 in Modes 1 through 4, no response to this t
leter is necessary for Millstone Unit No. 2.
Sincerely, Robert W. Reid, Chief Operating Reactors Branch #4 Division of Operating Reactors
Enclosure:
Jnterim Position for Containment Purge and Vent Valve Operation cc: w/encicsure See next page 1353 304
Northeast Nuclear Energy Company cc:
William H. Cuddy, Esquire Day, Serry & Howard Counselors at Law One Constitution Plaza Hartford, Connecticut 06103 Waterford Public Library Rope Ferry Road, Route 156 Waterford, Connecticut 06385 Northeast Nuclear Energy Company ATTN:
Superintendent Millstone Plant Post Of fice Box 128 llaterford, Connecticut 06385 Northeast Utilities Service Company ATTN:
Mr. James R. Himmelwright Nuclear Engineering and Operations P. O. Box 270 Hartford, Connecticut 06101 Anthony I. Roisman, Esq.
Natural Resources Defense Council 91715th Street, N.W.
Washington, D.C.
20005 Mr. John T. Shediosky Nuclear Regulatory Commission, Region I Office of Inspection and Enforcement 631 Park Avenue King of Prussia, Pennsylvania 19406 1353 305
- -~~r -,
i INTERIM POSITION FOR CONTAINMENT PURGE AND VENT VALVE OPERATION PENDING RESOLUTION OF ISOLATION VALVE OPERABILIT 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 Noverber 1978 letter justifying your proposed operational mode. The revised restrictions can be established separately for each system.
Whenever the containment integrity is required, emphasis should be 1.
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:
All isolation valves greater than 3" nominal diameter used for a.
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 detemined in consultation with the valve 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 tend to close when the fluid dynamic forces are introduced, and Modifications, as necessary, have been made to segregate the containment b.
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.
1353 306