NRC Generic Letter 1979-54
| ML031320368 | |
| Person / Time | |
|---|---|
| Issue date: | 10/22/1979 |
| From: | Ippolito T A Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| GL-79-054, NUDOCS 7911190063 | |
| Download: ML031320368 (5) | |
0V- --.-VDocket Nos.and 50-296a AIORY BOE1iET RL LI' LJLlOCTOBER 2 2 1979DistributionL,, DocketORB #3NRR ReadingLocal PDRNRC PDRTIppolitoEReeVesAtty, OELDOI&E (3)TERAACRS (16)SSheppardRACIarkMr. Hugh G. ParrisManager of PowerTennessee Valley Authority,500 A Chestnut Street, Tower IIChattanooga. Tennessee 37401Dear Mr. Parris:RE: Containment Purging and Venting During Normal OperationBy letter dated November 29, 1978, the Commission (NRC) requested alllicensees of operating reactors to respond to generic concerns aboutcontainment purging or venting during normal plant operation. Thegeneric concerns were twofold:(1) Events had occurred where licensees overrode or bypassed the safetyactuation isolation signals to the containment isolation valves.These events were determined to be abnormal occurrences and reportedto Congress in January 1979.(2) Recent licensing reviews have required tests or analyses to show thatcontainment purge or vent valves-would shut without degrading con-tainment Integrity during the dynamic loads of a design basis lossof coolant accident (DBA-LOCA)..The ARC position of the November 1978 letter requested that licenseestake the following positive actions pending completion of the tRC review:(1)-prohibit the override or bypass of any safety actuation signal whichwould affect another safety actuation signal; the NRC Office of Inspectionand Enforcement would verify that administrative controls prevent impropermanual defeat of safety actuation signals, and (2) cease purging (orventing) of containment or limit purging (or venting) to an absoluteminimum, 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 requestedto demonstrate (by test or by test and analysis) that containment isolationvalves would shut under postulated DBA-LOCA condition. The NRC positionswere amplified by citation (and an attached copy) of our Standard ReviewPlan (SRP) 6.2.4 Revision 1 and the-associated Branch Technical PositionCSR 6-4, which have effectively classed the.purge and vent valves as*active" invoking the operability assurance program of SRP 3.9.3.The 'ARC staff has made site visits to several facilities, has met withlicensees at Bethesda, Maryland, and has held telecon conferences withma +1s.. 14-sn ~t s.L....A~C________________(A'D _._F+ussions, the NRC staff has stressed that Apo.o img.xt Qn.>t. e Akn.............as t-d-.. AUve-; assure that ontainment irtegrity Would be maintaineURNA ti e e v t o ...................................................... .. ....... .......................... ................'rs' ........................... ..... ...................... .... ..... ................. ......... ..... ................................... ......................N=-IORM 318 (9-76) NzRCK 0240** U.S. GOVURNtAKNT PRINTING oFFects 1977 -7l5 -769 Mr. Hugh G. Parris 2 -As a result of these actions, we have learned from several licenseesthat at least three valve vendors have reported that their valves maynot close against the ascending differential pressure and the resultingdynamic loading of the design basis LOCA. All identified licenseeswho are affected have proposed to maintain the valves in the closedposition or to restrict the angular opening of the valves whenever primarycontainment integrity is required until a re-evaluation is provided whichshows satisfactory valve performance under the DBA-LOCA condition.Recently, a report under 10 CFR Part 21 was received by the NRC fromthe manufacturer of butterfly valves which are installed in the primarycontainment at the Three Mile Island 'Unit 2 Nuclear Station. These butterflyvalves are used for purge and exhaust purposes and are required to operateduring accident conditions. The report discusses the use of an unqualifiedsolenoid valve for a safety-related valve function which requires operationunder accident conditions. The solenoid valve is used to pilot controlthe pneumatic valve actuators which are installed on the containmentventilation butterfly valves at this facility.. Your re-evaluation ofvalve performance for conditions noted in the previous paragraph mustconsider the concerns identified in IE Bulletin 79-01A.As the NRC review progresses, licensees which might have electricaloverride circuitry problems are being advised not to use the overrideand to take compensatory interim measures to minimize the problem.In light of the information gained during our reviews of your submittalsdated March 1, 1979-and June 12, 1979, and the information cited above,vie believe an interim commitment from you is required at this time. Thisis the case, even though you may have proposed Technical Specificationchanges or other long or short-term measures, which we are reviewing.For your use, we have provided as an attachment an interim NRC staffposition. In addition, our recently developed "Guidelines for Demonstrationof Operability of Purge and Vent Valves' were provided by separate letterto licensees of each operating reactor. This letter in no way relaxesany existing licensing requirements for your-facility.Because of the potential adverse effects on the'public health and safetywhich could result from the postulated- DBA-LOCA while operating withopen purge or vent valves, we believe your prompt response to this letteris required. In accordance with 10 CFR 50.54(f), you are requestedorrlucco .; ....... .......................... .................................. ................. ,.............*RIN ..... ac....................... ...... ... ,.................. ....... ......................GURNNK0................... ...... ... ......................... ... ....................... ... ....................... .. ..................... '.. ..... ............ ......;........ .t .I .. .__.__NARC FORMX 318 (9-76) NR.CM 0240* U.S. GOVKRKlMlKNT PRIN~TING OrFFC: *1*7 -,265 -If#
'5 -: W%'JMr. Hugh C. Parris-3 -to inforr us in' 4iriting.w ittiin 45 days ot receipt of this letter ofyour commitment to operate ti confoviianceiwith the enclosed interimposition and to provide us with information w~hich demonstrates thatyou have initiated the purge id vent valve operability verificationon an expedited basis. The Information provided in your response willenable us to determine whether or not.your license to operate BrownsFerry Units Nos. 1, 2 and 3 should be modified, suspended, or revoked.Sincerely,I .. .II1 -4 1-1I I.I E- clEncl'II !:j.it: -r,IOriginal Signed byT. A. WppoftoThonjas A. Ippolito, Chief ,Operating Reactors Branch #3Division of Operating ReactorsIntfPtlosure:er1m Position for Containmentirge and Vent Valve Operationcc: w/enclosureSee next pageAB' #3t ORB # 0 O 3.... ....-.----i ....... ..... ... .. ... ...... -.................. ........ ... ...... ......................RClark:mj E.. e 'relTISU NA O. .......................... ... ............. .... ...................... ... ......... ......................I __7_ 1 0/__1f79 .10/g2,79......... ................ .. ....... ......................... .......................... ......................Mc FWC $ (9-740 MM 02* U.S. GOVUYMNMT PRINTNGe SrrscCM C197 -16S -76 Mr. Hugh G. ParrisTennessee Valley Authority -4 -cc:H. S. Sanger, Jr., EsquireGeneral CounselTennessee Valley Authority400 Commerce AvenueE llB 33 CKnoxville, Tennessee 37902Mr. Dennis McCloudTennessee Valley Authority400 Chestnut Street, Tower IIChattanooga, Tennessee 37401Mr. E. G. BeasleyTennessee Valley Authority400 Commerce AvenueW lOC 131CKnoxville, Tennessee 37902Robert F. SullivanU. S. Nuclear Regulatory CommissionP. 0. Box 1863Decatur, Alabama 35602Athens Public LibrarySouth and ForrestAthens, Alabama 35611 INTERIM POSITION FOR CONTAINMENT PURGEAND VENT VALVE OPERATION PENDING RESOLUTION OF ISOLATION VALVE OPERABILITYOnce the conditions listed below are met, restrictions on use of the containmentpurge and vent system isolation valves will be revised based on our reviewof your responses to the November 1978 letter justifying your proposedoperational mode. The revised restrictions can be established separatelyfor each system.1. Whenever the containment integrity is required, emphasis should beplaced on operating the containment in a passive mode as much as possibleand on limiting all purging and venting times to as low as achievable.To justify venting or purging, there must be an established need toimprove working conditions to perform a safety related surveillanceor safety related maintenance procedure. (Examples of improved workingconditions would include deinerting, reducing temperature*, humidity*,and airborne activity sufficiently to permit efficient performanceor to significantly reduce occupational radiation exposures), and2. Maintain the containment purge and vent isolation valves closed wheneverthe reactor is not in the cold shutdown or refueling mode until suchtime as you can show that:a. All isolation valves greater than 3" nominal diameter used forcontainment purge and venting operations are operable under themost severe design basis accident flow condition loading and canclose 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 thevalve to be no more than 300 to 50° open (90' being full open). Themaximum opening shall be determined in consultation with the valvesupplier. The valve opening must be such that the critical valveparts will not be damaged by DBA-LOCA loads and that the valve willtend to close when the fluid dynamic forces are introduced, andb. Modifications, as necessary, have been made to segregate the containmentventilation isolation signals to ensure that, as a minimum, at leastone of the automatic safety injection actuation signals is uninhibitedand operable to initiate valve closure when any other isolation signalmay be blocked, reset, or overridden.* Only where temperature and humidity controls are not in the present design.