ML18136A191
| ML18136A191 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 10/23/1979 |
| From: | Schwencer A Office of Nuclear Reactor Regulation |
| To: | Proffitt W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| References | |
| NUDOCS 7911190066 | |
| Download: ML18136A191 (8) | |
Text
'** i' '
Docket Mr. t*J. L.' Proffitt
~
. OCTOBER, 2 3 1979 Senior Vice President - Power Viryinia Electric and Pm,;er Company Post Office Box 26666 Richmond,_ v*i ry in,i a '23261
Dear Mr. Proffitt:
or..
r\\l.. *
. Containment Purging and Venting During.* Nonna1 'Operation By letter dated *November 28, 1978, the Comrnissioi1 (NRC) requested all -
1 icensees of operating reactors to respond to generic concerns about c.ontainF1ent purging or venting during norraa1 plant operation. The.
~generic concerns were twofold:
( T)
(2)
Events had occurred ~-,here 1 jcensees overrode or bypassed tl1e safety actuation isulat'ion si'gnals to the contai111:1ent isolation valves *
. Tliese events i*:ere determi.ned to be abnormal occurr~nces and reported to Congress in January 1979.
Recent 1 icensing reviet:1s have required tests *or analyses to shov; that, co1,1tairrment purge or vent valves Hould shut without. degrading con-tainment integrity during the dynamic *loads of*a design basis loss
- of co6~ant.accident {DBA-LOCA).
/
. The NRC posit ion of the November 1978 letter requested that 1 icenset~s take the -following* positive actions pending completion of the NRC revie\\'J:*
(1) prohibjt the override or bypass of any safety actuation si-gnal ivllich wou1 d a,ffect anotlier safety* acttwt ion signal; the NRC *Office of Inspect ion
- _me! Enforcement ~,-mulct verify
- that administrative controls prevent improper tilanual defeat of safety actucttion signals,* and (2) cease. purgin~1 (or venting) of containment or limit purtJi.ng (or venting) to an absoiute minimum*. 11ot to exceed :JO hours per year.
Licensees v1ere requested',
to demonstrate (by test or *by test and analysis) that containment isolation valves would sh~t under postulated DBA-LOtA condition. The NRC ~osit1ons
- v1er:e *arnpl ified by cltation* (and dt:1 attached copy) of our Standard Reviet*J Plan (SRP) 6.2.4 Revision 1 and the assocfated Branch Technical Position
'csn 6-4, 1,1hich have effectively c'!asse,d the pur~e and vent valves as 11activc 11 invokinJ the operabi_lity assurance prog1~am of Sf{P 3.9.J.
with JGC PORM 318 (9*76) NB.CM 0240
'* u.g. OOVl!RNMBCNT PRINTING OP'FICB: t *71
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- 71D
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J.\\s a resu1 t of these: actions. \\;e i1,ave learned from several 1 icensees that at least t.1'1ree valve vendors have reported that their valves may not close against the ascendinsJ difforentia1 pressure and the.resulting dynamic *102ding of the design basis LOCf\\.
/\\11 identified *1 icense:es who are affected have proposed to maintain the valves. in the closed position or*to restrict the anuular Op:::!nin0 of the valves t,.ihenevcr prir:1ary containr.1ent integrity is required until *a re,-evaluation is provided ~\\Illich shows satisfactory valve perforr..ance under the DBA-LOCA condition.
Recently, a report under 10 CFR Pc.1rt 21 was recE:ived by the NRC frot~i the manufacturer of butterfl.Y valves t,;ltich arc~ installed in tile prifilary corrtainment at th~ Three Mile Island Ur1it 2 Nucle~r Station. These butterfly valves are used for purge* and exlwust pµrµoses and are required to operate dL;r*ing accident conditions.
The r-::port discusses the use of an unqualified sol 2noid valve for.:i safoty-re1 ated *valve function which requires operation ur1(ier accide11t con,1itio11s.
The solenoid vulve is usc~d to pilotcontrol the pnew.1atic valve acttiators Nhich are installed on the containrnent
'1entilation butterfly valves at this facility.
Your r:e-evaluation of valve performance fur conditions noted in the previous paragraph must consider the concerns identified in IE Bu11etin 79-01/\\.
As the r-mc revie1,,-J prosresses, l'icensees 1-;ilicr, 1;1i9ht have eieetrical overr*icie circuitry µroblems are being advised not to use t!le override ancl to take corup(~nsatory interim measures to mini1n-ize the probfof;!.
In 1 ight of the inforrnation ~dined during our reviews *of your sub1;1ittal datecl January 3, 1979. ancl the inforr.ia~'ion cited above) 1*:e be] ieve an interim cornrnitrnerit from you is required at this tiwe.
This is the case, even though your Technical Specification~ restrict purging abov~ 350°F.
Our interin* requirenc~nts in Enclosure 1 do not appear to be met for all conditions other than cold shutdmm.
For your use, \\'le have provided as an attad1ment an int(~rirn MRC staff position.
In addition, our recently d2vel oped "Gui.de 1 ines for Deuonstrat ion of Operab i l it.Y* of Purge -and Vent V,Jves" v1en~ provided i\\y sep,ffa_ti::: letter to licensees of each ope.rating n::,ictor.
This letter in no *.iay relaxes any ex-isting licensing requirer,ients for your f ac n 'ity.
l
~-*
.'/
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r3ecause of the potemi~V;~dverse effects on the*put/lic health z:nd s,afety v,ihic!i c0uld l1.:sult fro,i~t'.*th~ pustulateds DG/1-LOCA \\*1hik operdtin9 \\ith op~n pur:Je or ve11t. v.-ciTve:;. 1'-/e bel icve your pro::ipt response to th;i's letter is required.
In accordance ~-,ith 10 CFR 50.~>i}(f), you an2! requl:sted
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ffl1C FORM 318 (9-76) NB.CM 02.CO U.S. CilCVERNMENT PRINTING OP'F'ICC!: t D78 - 2&8: - 7130
Mr. W. L. P~riffitt 3
/
to inform us in lf,r1ting within 4$/d11ys of receipt of this letter-of your commitment *to oplfrate in C(>flfonnanc*e with the enclosed interih1
.position and to provide us, wit!( information *1r1hich demonstrates that you have initiqtecj the purge,/and Vent VillVe operability Verificatiorl un an expcd,ted basis.
- n1E{ information provided in your-response itil l enable us to determine v-,hether or not your* 1 icense to. operate Surry Power, Station, Unit Nos. l and 2 should be modified, *suspe.ndeJ, or revoked.
/
Enclosure:
Interim Position for Containment Purge an~Yent Valv~ Operation
. cc:
H/ enc 1 osure
.see next pa9e Sincerely, Orlgim1.I Signed ~Y-.*
A. Schi,iencer ~ Chief Operati.ng-Rea~to*rs Branch #1 Di vision of Opli!rating Reactors
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DATB~ 1.91.... /.l~.......... J.9.1.... l.!.~..-....... Rl..-...1.?.~............ *.................... :...... *..................... :..........................
MlC POKM 318 (9-76) NRCM 02.(0 U,S, GOVl!RNM*NT PRINTIN~ Ol"FICB:: 1971 - 2811
- 1**
e UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 OCTOBER
Dear Mr. Proffitt:
RE:
Containment Purging and Venting During Nonnal 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 1 icensees 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 containmant 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:
(l)*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 amp,lified by citation (and an attached copy) of our Standard Review
.Plan (SRP) 6.2.4 Revision 1 and the associated Branch Technical Pbsition CSB 6-4, which have effectively classed the purge and vent valves as 11 active 11 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.
e Mr. W. OCTOBER C*
- 197~
As a result of these actions, we have 1 earned from several 1 icensees 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 perfonnance 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 condition_s.
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 perfonnance for conditions noted in the previous paragraph must consider the concerns identified in IE Bulletin 79-0lA.
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 1 ight of t,he information gained during our reviews of your submittal dated January 3, 1979 and the information cited above, we believe an interim commitment from you is required at this time.
This is the case, even though your Technical Specifications restrict purging above 350°F.
Our interim requirements in Enclosure l do not appear to be met for all conditions other than cold shutdown.
For your use, we have provided as an.~ttachment an interim NRC staff position.
In addition, our recently developed 11Gui_del ines for Demonstration of Operab i1 ity of Purge. and Vent Valves" were provided by separate letter to 1 icensees 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 prompt response to this letter is required.
In accordance with 10 CFR 50.54(f), you are requested
e Mr. W. L. Proffitt 3 -
OCTOBER 2 3 1979 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 information which demonstrates that you have initiated the purge and vent valve operability verification on an expedited basis. The infonnation provided in your response will eliab le us to determine whether or not your license to operate Surry Power, Station, Unit Nos. l and 2 should be modified, suspended, or revoked.
Enclosure:
Interim Position for Containment Purge and Vent Valve Operation cc:
w/ enclosure See next page Sincere1__;{
0, /<::i:rfttt-'1/,!et.--,--
A. Schwencer, Chief Operating Reactors Branch #1 Division of Operating Reactors
e Mr. W. L. Proffitt Virginia Electric and Power Company cc:
Mr. Michael W. Maupin Hunton and Williams Post Office Box 1535 Richmond, Virginia 23213 Swem Library College of William and Mary Williamsburg, Virginia 23185 Donald J. Burke U. S. Nuclear Regulatory Commission Region II Office of Inspection and Enforcement 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303 OCTOBER
. ~ 1979
e INTERIM POSITION FOR CONTAINMENT PURGE A!iO VENT VALVE OPERATION PEtWING RESOLUTIOr~ OF ISOLATION VALVE OPERABILEY 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 November 1978 letter justifying your proposed o~~rational 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 pas~'ve mode as much as possible and on limiting all purging and venting times to as lov, 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, reduci~g temperature*, humidity*,
and airborne activity sufficiently to permit efficient perfomance or to significantly reduce occupational radiation exposures), and
- 2.
Mainta*in the* containr,ient 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 11 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 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 deter~ined in consultation with the valve supplier.
The valve opening must be such that the critical valve parts will not be damaged by DSA-LOCA loads and that the valve will tend to close 1-1hen 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 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 te~perature and humidity controls are not in the present design.