ML20059K195

Clarifies Auxiliary Feedwater Sys Commitments Concerning Ability of Sys to Prevent Total Loss of Feedwater Following Various Pipe Breaks & Component Failures

ML20059K195
Person / Time
Site:	Calvert Cliffs
Issue date:	09/18/1990
From:	Creel G BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9009210211
Download: ML20059K195 (10)

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BALTIMORE

- OAS AND ELECTRIC CHARLES CENTER _ e P.O. BOX 147C e BALTIMORE,. MARYLAND 21203 1475 Gromot C. CRttL Vice Patsiotut  !

i Wucitan tutmov '

(801)#60**499 i

September is,1990 -

U. S. Nuclear Regulatory Commission '

-Washington, DC 20555-ATTENTION: Document Control Desk-

SUBJECT:

Calvert Cliffs Nuclear Power Plant '

Unit Not l' & 2: Docket Nos. 50-317 & 50-318:

Clarification bf Aurillarv Feedwater System Commitments i y;w '

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. Gentlemen:

j While reviewing. the technical 'adequack andJiicensingibasis Of ~ ouri A'uxiliary- Feedwater' g_ (AFW) System in: conjunction with a ' recent Facility Change,' .we- found the L documentation i

surc staff, L and--- this.

of some - is ues unclear. ThisJ matterLhas been Jdiscussed . with letter is . provided to ? communicate our resolution of 'the. issues, q

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gP ISSUE

SUMMARY

This issue concerns the . ability of ourf AFW systenbo lprevent 's, total . loss of . feedwater in . response to -' various pipes breaks 'andscomponent- failures. The criticals element of -j this capability is captured in 'a November 7, ~1979 NRC letter fstemming : from .the i

Bulletins and' Orders Task- Force review of operating reactors, subsequentnto the1 accident at .TMI-2. The ' pertinent recommendation stated-gi

'"S. Recommendations ---

The licensee should L e~ valuate , ~ the ' . following : -

concerns: i

. . . b) The Calvert . Cliffs AFW systems, do; not; meet the high / energy 2 line break criteria ini SRP '10.4.9 and- Branch' Technical:. Positionf 10al;- namely, a

that the AFW system should ' maintain the capability - toL supply the required -

flow to ' the steam generator (s) assuming 'a. pipe' break anywhere in the AFW' pump discharge lines concurrent with a single' active, failure."

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-At the time' of- this review, our AFW system' consisted of- two - turbine-driven pumps .

. feeding a common discharge --header. In response to these concerns, BG&E committed 'to

- adding a third train of AFW supplied by an electrically-driven pump. Specifics of the ~ ,"

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. system design were provided in' correspondence ' and meetings ~ during the course of 1980 -

ant 1981, in a meeting .on March 4,1981, NkC requested- that BG&E confirm by letter that the AFW system modifications had been reviewed to ensure that they would maintain

- the = capability to - supply = the ' required flow: to '. the steam ' generators assuming ~ a pipe L break anywhere in the AFW. purrp. discharge lines concurrent- with's single active failure. '

We confirmed ' this capability in our letter of' March 9,11981, stating:

"The- design and procedural changes required to implement the - AFW : system ,

modifications have= been reviewed to . ensure - that : they will maintain ' the -

capability to supply the required flow to the steam generator (s) assuming a pipe break anywhere in the AFW: pump discharge line concurrent with'a single active ' failure. The design and procedural changes are sufficient' tot ensure the capability J to-. - detect and ; isolate the L: break, " and direct: the required feedwater flow to the steam; generator (s)- before they boil dry"-

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. NRC accepted this position in a Safety: Evaluation. Report dated May 8, 1981, statingL

' that, "We find' the response to this - recommendation acceptable."

DISCUSSION ,

Two technical concerns arise out of reviewing this matter. First, what ' . is L Calvert Cliffs' capability in meeting the High Energy Line Break (HELB) . criteria in its AFW system design? Second, what is Calvert Cliffs' capability in responding / to a break- in  ;

the remainder of. its / FW pump discharge piping? : H

~1n response to the first concern, it is important to understandf that : the appropriate' I HELB criteria for Calvert Cliffs, as a pre-1975 plant, were defined - by. the y NRC's ,

(Giambusso) letter- of- December 15, 1972. For the AFW.- system, this; is documented in i Section 10A of the Updated Final Safety Analysis Report, which states in Section 10A.5, d (page 10A-59):

"During normal operation, the only portion of .the turbine - driven auxiliary a feedwater0 system which would have contained a high energy = fluid _(900 psia 1

and 532 F) is the section of pipe downstream of the? isolation valve before .;

the steam generator. This system has been modified' by Einstalling al check valve inside the containment,- thus . eliminating , the line outside ' of.

containment 'as a high energy system."

i Consequently, rupture of the AFWS discharge line outside containment does not need .to be postulated' from the standpoint of HELB considerations. A. 'later. revision of- Branch  !

Technical Position 10-1 modified the standard ~used in Recommendation 5.b of" the ~ l November 7,1979 letter to read,

. . . the system should .be so arranged as to assure . the capability to supply necessary emergency feedwater to the steam generators,- despite the postulated rupture of - any hiah enerav section (emphasis added) . of the system, assuming a concurrent single active failure."

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Do. ant C:ntr:I Desk .

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Given Calvert Cliffs' curient design, this capability is ~ more! than . adequately-' met with j any :- two of ~the three installed auxiliary feedwater pumps in each unit. L This is the ~ j appropriate licensing ~ basis for plants of our vintage, and ' et is reflected in the-l current Technical Specifications governing l AFW/ _ system availability. '

p In response to the second question, which regards Calvert Cliffs' capability to respond i to a break anywhere in the AFW pump discharge piping, our answer in the March _9,1981:

letter is accurate. This - response _ was made baseo on the presence _ of a crow,-connect between - the motor-driven trains' - discharge : lines. - The design 1 of. the AFW = System - still ~ -l contains- the cross-connect and - its associated - control ._ valves, . and procedures exist .;

which - describe = its use under emergency. circumstances. The cross-connect capability isE i routinely tested under the existing surveillance program. The cross-connect capability. I is not always OPERABLE. During periods - when " both Units are not in MODE 3 A or higher, the cross-connected = pump may be -inoperable as a ' result of- maintenance'in the.

1 opposite Unit.

1 A more detailed chronology. of the relevant correspondence is provided as an: attachment to this letter.

CONCLUSION Based on the above discussions, it is clear that our , AFW system is; an exception - to the. general understanding that AFW ' systems - are ? to . be : considered : _ high - energy ,

everywhere in the system. These~ exceptions - were negotiated with,Tand approved, by, - the 1'

NRC. The existing system is _ designed -to ' function following a breakLin the- high energy.

portion of the system concurrent with a single - active failure. The cross-connect a .  ;

capability improves system reliability and our - Technical . Specifications only - consider x

its use when two AFW pumps are unavailable for up to 72' hours." Plants without' this '

cross-connect capability are required to ' shutdown:- with~ six hours after - declaring two AFW pumps inoperable.

Our AFW system was, and continues to be, a redundant,' reliable system which meets all m of the appropriate design and licensing = requirements.

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Should you have any further questions regarding - this matter, we will be - pleased - to  !

discuss them with you. i I

Very truly your , l si

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. i' GCC/GLD/ PSF / dim j Attachmer.is:  :

Attachment (1), References to Attachment -(2)

Attachment (2), Chronology Attachment (3), Basic ' AFW System Diagram "

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• ' ~ . Sept:mber 18,'1990'

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cc: D. A.' Brune - Esquire

, J. ' E. . Silberg,. Esquire -

.a - R. A.Caprs, NRC D. G. Mcdonald,' Jr., NRC -

y_ - T. T. Martin, NRC L. E. Nicholson, NRC R.-I. McLean, DNR ~

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REFF" ENCES ,

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References:

.(a). Letter . from Mr. D.. G.- Eisenhutz (NRC) - to ' Mr. TA. E. . Lundvall -

.' (BG&E). dated November 7,1979,' NRC Requirements for Auxiliar'y Feedwater Systems at Calvert Cliffs!

~'(b) Letter from Mr.L A. E. ' Lundvall - (BG&E)' to Mr.1 D. G. Eisenhut (NRC),^ dated December, :13 1979. . ' Response to. Letter. dated c NovemA. 7,1979 w-(c) Letter from Mr.- A. E.-L Lundvall (BG&E) to Mr. R. A. Clark; (NRC),

dated: March . 9, : 1981, NRC 7 Requirementsi for.p Auxiliary ; Feedwater System ; s 4

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- (d) [ Leiter from Mr. R,0A. Clark (NRC) to Mr. . Al E. Lundvalli(BGAE), .

dated November 8,1981, Issuance of Amendments No. 54 and 37 -s

.l(e) Letter from 'Mr. A. Giambusso (NRC) 'to Mr. J..-W. ; Gore (BG&E), -

dated December.15,11972,: Piping Failures Outside Containment (f) Letter from Mr. W.7J.?Witte (BG&E) to MrdL.LM! Nuntaing '(NRC), '!

.-dated April 27,1973, Amendment 36 to Calvert Cliffs Final < Safetyj l Analysis Report 1

, 4 (g) Supplement If to the Safety' Evaluation for 'the Operation of' Calvert -  !

Cliffs, May- 1973 L o

.11 (h) Letter from" Mr. R. F. ! Ash' (BG&E) to Mr. ' R.l A. Cla'rk ' (NRC), -!

dated . December 18, ; 1980, .NRC Requirements - - for : Auxiliary > -i Feedwater System.

(1)- Letter from Mr. R.= A.-' Clark -(NRC)' to / Mr. ; A); E. Lundvall (BG&E), 4

- dated January 27, 1981, Auxiliary- Feedwater cSystem -

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l (j) ' Letter from c Mr. A.

E. Lundvall l(BG&E) 1 toe Mr. J. R. Miller (NRC), dated September -16,= 1983, Supplement 2 to Unit 1 Cycle 7-License Amendment'-

a' (k)L. Iletter from Mr. D. H. Jaffe (N5'.C)' to Mr. AL E. Lundi .*i (BG&E)E v, dated November-17,1983,~ Issuance of Amendment 88,' Unit 1J q 1

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After the _ accident at Three - Mile; Island, the NRC issued requirements that derived from their NRR Bulletins and Orders Task Force. At- this time, we only had two steam-driven AFW pumps. The turbines for these pumps were supplied stram from each  !

steam generator by the lines combined at one point in a common headt . The same was '

true on the discharge side of. the AFW pumps. One of the- long-term items, as issued in an NRC letter dated November 7, 1979 (Reference a), for Calvert Cliffs was as

' follws

l "5. Recommendations -- The licensee should evaluate the following concerns:

a) The AFW pump discharge lines and turbine-driven AFW steam supply lines combine into different single lines through which all AFW water or steam must flow. (See Figure 1.) A pipe break in either of these. single flow paths would cause loss of the entire AFW function, b) . . . b) The Calvert Cliffs AFW systems do not meet the high energy ,

line break criteria in SRP 10.4.9 and Branch Technical Position 10-1; namely, that the AFW system should maintain the capability to supply the required flow to the steam generator (s) assuming a pipe- break anywhere in the AFW pump discharge lines concurrent with a single active failure."

In a December 13, 1979 letter to the NRC (Reference b), we committed to install a motor-driven AFW pump.

" . . . the concern expressed abdut the common location of the AFWS pumps and associated equipment has resulted.in our commitment to add a third pump ,

train to the Calvert Cliffs AFW system . . . . We feel that the addition of a third pump train is the best was to eliminate concerns rf.garding the reliability of the aux feed system at Calvert Cliffs. With this approach i outage related construction t,me is minimized, concern about common headers is eliminated, instrumentation is relocated to an area removed from a possible steam environment, diversity in- pump motive power is obtained, and overall system reliability is greatly enhanced. The new system will be automatically initiated with a manual start back-up. The _ new system in combination with the existing system - will pnvide superior protection against single failures including pipe breaks and operator induced failures."

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Installation of the third pump with associated piping headers and controls satisfied the first Recommendation (Sa). The second Recommendation (Sb) was addressed in a BG&E letter to the NRC dated March 9 1981 (Reference c), .vhere we made the following statement in regard to the capabilities of our AFW system ' modifications:

"The design and procedural changes required to ' implement the AFW system >

modifications have been reviewed to ensure that they will maintain the.

capability to supply the required flow to the steam generator (s) assuming a pipe break anywhere in the AFW pump discharge line concurrent with a l

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1 single active fallu. . The design and procedural changes ate sufficient to ensure the capability to detect and isolate the: break,- &nd direct : the required- feedwater flow to the steam' generator (s) before they boil dry.'

The NRC ' responded to - this in their Safety Evaluation Report dated May 3,,1931 (Refe.ence d) as follows:

'By letter dated November 18, 1980, the licensee proposed . auxiliary feedwater system modifications _ in response , to our . long-term AFWS. >

requirements. By letter dated March 9, _1981, the licensee stated ' that the design: and- procedural changes required to implement the AFWS modifications have been reviewed to ensure that they will maintain the capability to supply the required flow to the ~ steans penerator(s), assuming a pipe break anywhere in the AFWS pump' dischwic lines concurrent with= a single active failure. The design and procedural changes are sufficient to ensure the capability to detect and isolate ' the break. and direct the required feedwater flow to the steam _ generator (s) before they _ boil dry. We ,

find the response to this recommendation acceptable."

We have confirmed with the original technical evaluator ' that ' the statement In' 14 March 9,1981 letter was made based on the presence L of a cross-connect between o motor-driven trains discharge lines. The design ' of the AFW System, with the cross-connect included, . made this a valid ' statement at the _ time. The design of < the Auxiliary Feedwater System still contains this cross-connect and its associated control valves and procedures exist which describe its use under emergency circumstances.

Therefore, this statement remains valid.

Our commitment to meet the passive and singie failure requirement of SRP.10A.9 and Branch Technical Position 10-1, out of a frame of reference to only High Energy. Line Break, went beyond what was necessary in light of the design and licensing basis for  ;

our plant. Our requirements for High Energy Line Breaks derived from- the Giambusso '

NRC letter dated December 15,1972 (Reference e). How we met the ' requirements is

, detailed in Final Safety Analysis Report (FSAR) Chapter 10A (submitted in-Reference f, approved by Grs NRC in Reference g). The Giambusso~ letter' required us to ensure that a pipe break in one system, such as Main Feedwater, would not have an-impact on any other system via pipe whip, compartment pressurization, or. jet 4 impinsement loads. The letter required the utilities to assume a high energy line '

break concurrent with a single active failure. Our original AFW design, with only the steam-driven pumps could meet this, details are described below.

(1) Main Steam to the AFW Pump Turbines: FSAR ' 10A.2 states,. " . . a break in .

this system between the CY4 and the auxiliary feed pump turbines is not considered credible." This is based on the level of quality control, ; ISI low usage factor. and the short time this portion of the system exceeds 200 F or 1

l 275 psig. Paragraph 10A.2.1 further states that the only portion of the line containing high etergy fluid is from the main steam lines to the control valves.

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j Therefore, a passive failure in either survive a single active failure. of the high energy portions could also (2)

Steam-Driven portion of contalument the system AFW thatPump contains=high Discharge energy is Piping:_

from- the check FSAR 10A.$ '

exposure of to thethe' steam generator. This check valve was installed valve insideto d h, "Tnis . system has line ecrease been to high modified energy'

._ b) conditions.'

installing a The FSAR specifically states,'

containment, thus eliminating system." Therefore, t .e system wouldthe line outside as a high of' energy containmentcheck ' va failure in the high energy portions, continue and to function a singlefollowing activeafailurepassive (3)

Motor-Driven modifications AFW above.):

discussed Pump FSAR Discharge'10A Piping (This pump was - adde of the system is only used ' for emergency .5 states that the motor-driven portion moderate' energy December 10, system. This was proposed conditions and was thus classified as a h), and to the NRC ' in bya NRC letter dated 1930There (Reference 1) letter (Reference are . approved in January

, 1981 27 AFW modification." stated,no ambiguitiesainhigh

'Therefore, this 'energy Issue in' that linethebreakNRC' analysis is not necessary for this Based on the above 4 :ussion, ~ the requirement active high ener and passive fallo.e (located for Calvert anywhere in the system regardless of ' Cl licensing' gy line conditions) simultaneously is whether it has basis. The issue was raised by the beyond the scope of . our design r.nd NRC In system that are exposed to high energy ' nconditions. of our AFW requirement 4-The need fw ' the moto. wriven trainsd cross-connect ' isi tion 311.2. In our retto for am Specifica-cross connect in Ae followin; manner:endment (Reference j),efined by Technical 4 we . describe the need- for the

'The remedial action statement maintains the intent sligned for autom@ of the LCO by requiringassociated that a second pump with two inoperable AFW ' pum be that the neit be initiating placed statas la hotwithinshutdown72 hours, or falling this, within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. During this 72-hour period the operators must also verify ur that (within one ho )

Unit 2 motor-driven pump is , perable . and %tthethe. cross connect va (2-CV-4550) has been exercised within the, rec'ious unit 4 hot shutdnwn w2th 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. or place the 31 days The above ' remedial improvement provided by actions, the addition when of conskieted the rootor-driven witht . (ht, system relia rain, the cross feedwater actuation system, provideconnect between for , n .overall matic -

the Unit I and 2 moto of safety currently provided in _ the technical specificaticia. The maxim period of operat;on that would be altowed with only one um automatically 3

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Therefore, a passive . failure in either of the high energy portions could also survive a single active failure.

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'(2) Steam-Driven AFW Pump Discharge Piping: SAR 10A.5 states that the only' l portion of- the system that contains high energy is from the check valve inside  ;

containment to the steam generator. This check valve was installed' to - decrease j

exposure of - the line . to high energy 1 conditions. The FSAR - specifically T states,  ;

, 'This system .has been modified by: Installing a check- valve . Inside the i l containment, thus eliminating the ;line outside of containment :as a high energy )

system.' Therefore, ' the system would continue . to function L following a' passive  :

failure In the high energy portions, and a single ~ active failure.  !

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(3) Motor-Driven ' AFW Pump Discharge Piping (This pump was addedL under the  !

modifications discussed above.): FSAR - 10A.5 states that the motor-driven portion i of the ' system is. only used for emergency ' conditions and was thus classified as a 1 moderate energy system. . This was proposed to the NRC ' in a letter dated  ;

December 10, 1980 (Reference h), and approv(d by NRC in January ; 27, 1981 i (Reference 1) letter. There are no ambiguities in this issue In that the NRC ,

stated, 'Therefore, a high energy . line break analysis is not necessary for' this AFW modification."

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Based on the above discussion, ' the requirement for : Calvert Cliffs to meet a single  ;

ac'ive and passive failure (located anywhere in the system regardless; of, whether it has  :

hit h energy line conditbns) simultaneously is beyond the scope s of our design ~ and liceesing basis. The iss a was raised by ' the . NRC in light of High Energy - Break >

requirements. The FSAP demonstrates that there are no common portions of our AFW system' that are exposed to high ' energy conditions. <  ;

The need for the motor-driven trains cross-connect isI defined by Technical Specifica- 1 l tion 3.7.1.2. In our request for amendment (Reference j) we describe the need for the  ;

cross-connect in the following manner:

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'The remedial action statement associated 'with .two inoperable AFW pumps maintains the intent of the LCO by requiring - that - a 'second pump be

aligned for automatic initiating status within. 72 : hours, or failing this, that the unit be placed in hot shutdown within ' 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. During this 72-hour period the operators must also verify (within one hour) that the i Unit 2 motor-driven pump is operable and that the cross: :onnect valve (2-CV-4550) has been exercised within the previous 31 days, or - place ,the '

unit in hot shutdown with 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

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" The above remedial actions, when considered with the' system reliability improvement provided by the addition of the taotor-driven train.' the cross connect between the Unit I and 2 motor-driven pumps, and the new automatic .

feedwater actuation system, provide for an overall increase in the margin '

of safety currently provided in the technical specificetions. - The maximum ,

period of operation that would - be allowed with only one automatically. .

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l actuated AFW pump in operable status (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />) ~ is not bting . Increased, while the proposed ' specification would require additional re:0edial actions .;

(verification of cess-connect operability) by- the operators bqond that i

. which is. currently . required . by the technical specifications," . l The NRC - approved this use of the cross-connect capability in . Reference : (k). - I describing it as follows: i

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• In addition, . the proposed TS .would allow two of the three ' AFW ~ pumps to I be-inoperable for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> provided that the AFW cross-connect and [

the - Unit 2 motor : driven AFW pump are verified to be operable. This 1*

proposed M is At least. equivalent ' to the existing M in . that ' a . ' total of two AFW pumps are required to be operable; in this case on Unit < 1 and .i one Unh 2 auxiliary feedwater pump would be required."-  !

It is clear from the NRC's response t that our . AFW system is considered sufficiently.  !

redundant that additional controls were not necessary. . '

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