ML20071P731

Proposed Findings of Fact & Conclusions of Law on Contention 9a Re Water Hammer

ML20071P731
Person / Time
Site:	Byron
Issue date:	05/31/1983
From:	DEKALB AREA ALLIANCE FOR RESPONSIBLE ENERGY, SINNISSIPPI ALLIANCE FOR THE ENVIRONMENT (SAFE)
To:
Shared Package
ML20071P729	List: ML20071P722 ML20071P731
References
REF-GTECI-A-01, REF-GTECI-PI, TASK-A-01, TASK-A-1, TASK-OR NUDOCS 8306080145
Download: ML20071P731 (19)

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Sinnissippi Allianco far the Enviranmant 326 North Avon Street Rockford, Illinois 61103 Waterhammer Findings May 31, 1983 OPINION I. CONTENTIONS e**********

DAARE/ SAFE ' Contention 9(a) ~-Waterhammer DAARE/ SAFE Contention 9(a) raises a concern over the possibility of a waterhammer event occurring in the feedwater bypass line at the Byron Station.

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Specifically, the contention' addresses ~so1ely the question of whether or not the steam generator'feedwater bypass line installed in Byron will be suscept-ible to bubble collapse waterhamer such as the one that occurred in the feed-water bypass line at the KRSKO plant in Yugoslavia in mid-1981. Bubble collapse

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waterhammer is a phenomenon that can occur.when'a volume of steam is trapped in anenclosedarea,such'asapipe,byslugsodjwater. Cold water in the slugs t -

trould cause the steam to cohdense rit' p idly,] thereby triggering a sequence of r

f events that could cause; a waterhamer even't resulting in damage to the pipe and/

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or its supports.

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. Applicable Law Before an operating licenNe may issue, NRC must find that reasonable assur-i ance exists such that the activities authorized by the operating license can be conducted without endangering the health and safety of the public and that such activities will be conducted in compliance with the Com.ission's regulations.

10 C.F.R. 50.57 (a) (3). One of the means for statisfying the requirements imposed by this regulation is to comply with the General Design Criteria for light water nuclear power reactors set forth in Appendix A to 10 C.F.R. Part 50.

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'These criteria establish' principal design requirements for determining reactor safety. With regard to the potential for the occurrence of waterhammer in the feedwater bypass line, General Design Criterion 4 " Environmental and missle de-sign bases" states in pertinent part:

Structures, systems, and components important to safety shall be . . . appropriately protected against dynamic ef-facts . . .that may result from equipment failures and from events and conditions outside the nuclear power unit.

The actual review and/or evaluation for the design for or avoidance of water hammer is normally reviewed through dif-forent portions of the safety review plan. (Finding 1)

Section 15.2.8 of the Standard Review Plan, NUREG-75/087, describes the review pertinent to the evaluation of potential water hammer effects, as:

APCSB reviews the auxiliary feedwater system to verify that it can function following a feedwater line break, given a single active component failure and with either onsite or offsite power. This review is performed as described in Standard Review Plan (SRP) 10.4.9.

RSB reviews the auxiliary feedwater system to confirm that the flow provided is acceptable for controlling the transiant following a feedwater line break.

MEB evaluates potential water-hammer effects on safety valve integrity.

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The ability of the auxiliary feedwater system to supply adequate feedwater flow to the unaffected steam generators during the accident and subsequent shutdown is evaluated by APCSB as to availability and by RSB as to capability to effect an orderly shutdown. Since auxiliary feedwater system designs are diverse and may require both automatic and manual actuation, preoperat-

! ional tests should be specified to identify any necessary oper-ator actions and to determine the maximum times permitted for i

their completion.

Waterhammer events such as occurred at KRSKO, create a." dynamic effect" against which systems important to safety are to be " appropriately protected." The feedwater bypass line is "important to safety" because this line serves as part of the Auxiliary Fecdwater System which is designed to facilitate safe plant shutdown in the event of a loss of heat sink accident. (Finding 5) Preoperat-

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-(3) ional testing is specifi6d as a:meansAw$e rt function of the. auxiliary feedwater system has been appr6priately protected against the dynamic effect.

The issue before us then is whether the auxiliary feedwater system at the Byron plant is appropriately protected against the dynamic effects of a KRSKO-type waterhammer svent so. as % 1 meet Standard Review Plan.. criteria.

DMSC/ SAFE stipulated Contention 9(a) suggests that there should be a demo-natration that a KRSKO-type waterhammer event will never occur at Byron. (Find-ing 3) In view of the standard set forth in General Deisgn Criterion 4, and u

applicant and staff witness testimony, the Contention may set forth an overly strict acceptance criterion. (Finding 47) However, although General Design

• Criterion 4 does not require a guarantee that a KRSKO-type waterhammer event

, will not occur at Byron, operation of the Byron plant with the proposed implem-

,entation of Westinghouse recommendations to mitigate waterhaumer,should be re-quired to meet the " appropriate protection" standard..

Byron and KRSKO Steam Generator Design Byron and KRSKO share the same..model of steam generators, the Westinghouse Model D preheater counterflow type steam generator. They also have a connon design of feedwater systems which serve these steam generators. There are basically three feedwater systems: the Main Feedwater System, the Feedwater Bypass System, and the Auxiliary Feedwater System. The last two systems intr'o-duce feedwater-into the steamig enerator through an auxiliary nozzle located in the upper shell.of the vessel. The Feedwater Bypass System was specifically designed to limit the possibility of occurrence of waterhammer events in the preheater section of the steam generator which is located inside the lower

'shell of the vessel adjacent to the main feedwater nozzle. The Feedwater Bypass i System accomplishes this purpose by diverting cold feedwater to the auxiliary I

nozzle throuyh the feedwater bypass line. (Finding 5) The waterhanner event considered here, however, did not occur in the preheater section, but in the

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Feedwater Bypass Syistem; specifically, the feedwater bypass line.

The KRSKO Waterhanumer Event ,

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The Applicant's expert witness oti the waterhammer phenomenon reconstructed The KRSKO waterhammer event based on the available data. The event was a " bub-ble collapse" type waterhamuner. The waterhanuner apparently occurred during Hot Functional Testing of the Auxiliary Feedwater System pumps in July, 1981, but damage was not discovered till early August, 1981. The first indications of the waterhammer event were the discoveries of blistered paint on the pipes of .tfie Auxiliary Feedwater System as far back as the motor driven pumps, movement'ofr several pipe hangers, and piping, and a quarter-inch bulge on a six to eight inch section of the bypass piping within containment near the secondary shield wall. (Findings 2, 4)

As a result of the event, the section of bypass piping containing the bulge was replaced. (Finding 6)

The evidence gathered during the assessment of the damage at KRSKO provid-ed a basis for a reconstruction of the event'as related by Applicant',s expert

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witness, although he sta,ted the exact time and sequence of events is not known.

(Finding 7) Apparently', auxiliary feedwater check valves "which were known to leak" permitted backleakage througK that system. Secondly, the water level in the steam generator fell below the discharge end of the internal extension of the auxiliary nozzle, thus allowing steam to flow out through the auxiliary i

nozzle and into the Feedwater Bypass System piping. With steam present in the bypass piping, the Auxiliary Feedwater Syptem motor driven pumps were started as part of Hot Functional Testing, thereby introducing cold water into the by-pass piping. The cold water rapidly condensed the steam and thus caused the waterhammer. (Findings 8, 9)

The Westinghouse' Recommendations Westinghouse has made four recomunendations to Applicant to avoid a KRSKO-

v e s (5) type waterhamer event in the Feedwater Bypass System at the Byron Station.

First, temperature sensors shoisld be installed on the bypass piping close to the auxiliary nozzle to detect backleakage of hot water or steam. Applicant's Assist-Superintendent of Operations at Byron, witness Pleniewicz, testified that the temperature monitoring system will consist of temperature sensors on the feed-water piping adjacent to the aur.iliary feedwater nozzle on each of the steam generetors at Byron, which will feed information to the plant process computer, I programed to alarm when an abnormally high temperature is detected in the by' pass piping. Temperature senscrs will provide continous checking on check valve leak-age, howeverr as only one of the 6-inch valves and two of the 8 four-inch valves will be routinely inspected during refueling and maintance outages, these temp-erature sensors will be the relied upon indication of check valve condition. The temperature sensors used will be RTD's, which Pleniewicz admitted have been known to fail. (Findings 10, 11, 12, 13, 14)

NRC Staff witness, Serkiz, conceeded the possibility that a schedule of check valve or sensor maintance might . help reduce the possibility of water hamer bubble collapse at a facility, but'neither he nor Applicant witness, Carlson, A

were familiar with check va,lve or temperature censor maintance or inspection pro-ceedures. (Findings 15, 16, 17)

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Second, in the event backleakage in the system is detected, Westinghouse l

has recommended that the bypass piping should be slowly refilled or the plant brought to a cold shutdown conditilon. The recomended refill rate was one w .

which was derived from an analytical study done by the Westinghouse R & D Cen-ter, but applicant is still in the process of developing procedures to enable the reactor operator to perform the task, and the hot functional testing itself will determine whether or not the tempering flow system at Byron can achieve the low flow rate as recommended. (Findings 18, 19, 20, 21)

Third, Westinghouse recomended that the water level in the steam gener-e

-(6) ator be maintained above the auxiliary nozzle discharge pipe as much as pos-si~ ole. In general, the water level in the steam generators would not fall be-low the auxiliary nozzle discharge pipe, unless under an accident situation such as a feed line break. (Finding 22) '

rourth, the check valves of the Auxiliary Feedwater System should be maintained to minimize backleakage. As indicated earlier, although applicant-witnesses stated stated that some of the valves at Byron will be routinely in-spected during outages, temperature sensors with some unreliability will be the sole continous monitor of check valve condition. (Findings 12, 13, 14)

The Staff Review The KRSKO water hammer event is within the purview of NRC Unresolved Safety Issue A-1, Waterhammer. Waterhammer is treated as a generic issue by the NRC yet, every instance of waterhammer, including bubble collapse water-hammer is considered to be plant specific.. (Findings 23, 24)

-The NRC does not have a task force studying water hammer. The Auxiliary Systems. Branch and the Reactor Systems Branch are the primary branches invol-( .'

! ed in reviewing waterhammer. With the exception of the International Atomic l h Energy Agencyavisit to KRSKO, which concerned examination of the Flow-induced Vibration phenomena at that plant, neither of these two branches have directly investigated the KRSKO waterhammer event. (Findings 25, 26, 27)

The Staff witness, Serkis, the task manager for Unresolved Safety Issue A-1,Waterhammer,wasresponsigleforconductingtheNRCevaluationoftheKRSKO j event, the KRSKO and Byron plant designs, and the Westinghouse recommendations.

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As Serkiz: stated,- Staff's evaluation of the KRSKO waterhammer event has been limited to review of information it recieved from Westinghouse and applicant at a meeting and through several items of correspondence. (Findings 28, 29, 30)

Staff's evaluation also relied in part on NUREG/CR-3090 " Evaluation of 1 terhanner Potential in Preheat Steam Generators", which was introduced into

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evidence as Board Exhibit 2, in reaching their conclusions about the generic 4

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(7) implication of bubble collapse waterhammer events to preheat steam generators, and in this case, to Byron. (Findings 31, 32)

NRC Staff did not participate directly in drawing up NUREG-3090, but Ser-kiz provided the contractor with the details concerning the KRSKO event and

-design specifics for the McGuire, Summer, and Byron plants. (Finding 33)

Other than informaticn related to backleakage, NRC Staff was not able to 3

obtain explicit details of the type of preoperational tests being run at the moment of the DRSKO event, including as to whether proceedures were being fol-lowed or' specialty tests being performed. Lacking the specifics on what occur- .

red, Staff categorized the KRSKO event as a plant specific event, not generic in nature. Staff's conclusion that the event was plant specific and not generic was not^therefore intended to imply it could not occur in U.S. domestic steam generators.

Rather, the KRSKO event reveals that a waterhammer due to bubble collapse can occur in the Auxiliary System of preheat steam generators. (Findings 34, Staff review of the KRSK0 event was neither thorough 35, 36) or independent from that of: Westinghouse or Edison.

Serkia stated that the Westinggouse recoinmendations constitute good engin-eering design practices and prudent operating procedures. He clarified it by

, e saying it was bas 6d upon the assumption that good engineering design practices and prudent operating procedures would be followed in implementing those recom-l mandations. Upon that basis.he was able to reach the conclusion that had those corrective measures been in place g at the time of the KRSKO event, it likely would not have occurred. By that, he does not mean to imply that instances of faulty design or operation do not occur, as of course KRSKO demonstrated, it's cause attributed to backleakage through auxiliary feedwater check valves "which were known to leak". (Findings 37, 38, 39, 40, 41)

With respect to the Westinghouse reconsnendations, witnesses stressed the a

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, contributing' effectiveness of the continous, tempering flow to be provided to the steam generator auxiliary nozzle to minimize bac,cleakage of steam from the

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. e (8) steam generator during power operation. Applicant has indicated though that this flow will not be present during the heat-up phase; and, during cooldown and h6t standby, the feedwater supplied through the auxiliary nozzle is relat-4 ively small, not always enough to permit a continouseflow soothat the opportun-

! ity for steam backleakage does exist if valve 1 failure and low water level oc-j curs. (Findings 41, 42) .

According to the testimony of Applicant and Staff witnesses, the KRSKO waterhammer. event did not compromise the ability of the affected systems to l

function. The Staff witness testified that similarly, there would be no con-u sequences if a KRSKO-type waterhamer event of the same mpgnitude occurred at r

Byron, i. e, if there was a pipe rupture, there would be no breach of the pri-mary co61 ant system and thus no release of radiation. The facts remain how-ever that the KRSKO event did result in damage; was at the upper end in mag-nitude of such possible events involving that plant system, and that the pipe could have ruptured had it been larger. (Findings 4, 43, 44,.45, 46 )

J Furthermore, as Applicant's" witness said,* It should be clearly stated

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that waterhammer will continue to occur", and the number of instances that it

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may occur over the lifetime of a steam generator cannot be predicted. As noted earlier, the Feedwater Bypass System was developed and implemnted to reduce the possibility of bubble collapse water hammer occuring in the preheater of pre-heat steam generators. In it'gs development there was nottesting conducted by Westinghouse prior to the KRSKO event which could have led it to conclude that e i the bypass system would be succes'sful without, in turn, inducing waterhammer in the bypass line itself. ,The removal of a fast-acting type check valve from the Byron Auxiliary Feedwater System at Byron from it's position by the auxil-iary foedwater nozzle, 'due to cor.cern over possible " acoustical" waterhamer occurance under at.least one accident sequence in'dicates the Auxiliary System may be susceptible to moregthan one typq of waterhammer. (Findings 47, 48, 49),

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It is convg}vable that the results of a bubble-collapse waterhammer and classical waterhammer events could be the same in their effects on piping sys-

., tems. Both result in a change in water pressure which has the potential for dam-N .

aging piping components, and possiblo piping rupture. There are metal fatigue factors associated with bubble collapse waterhamer occurring in the preheater i section of a steam generator, and as Carlson admitted, all bubble collapse wa-l i

l terhammer events have comon elements regardless of where they occur. Their effact differp only according to the geometry of their location; wh' ether they l

occur in piping, preheater passes, etc. (Findinga 53, 54, 55, 56)

Westinghouse anticipates Bypass System failure to occur on four occasions l within the 40-year lifespan of a steam generator. The initial susceptibility l

l of the Byron steam generators or feedwater system to bubble-collapse waterhamer has yet to be determined in preoperational testing. The Byron plant will essent-ially be the first operational plant to implement the Westinghouse recommend-(

l ations with a feedwater system representative of the type of system at the KRSKO plant prior to the event. NRC Staff is comtemplating changes to the Stan-r dard Review Plan as part of the resolution of the Waterhamer ' issue, but it has -

l not been shown what these changes will be or that preoperational testing will encompass them. Applicant has not demonstrated that the preoperational p'ro ,

cedures or. operation plans bein'g developed can specifically address feed line breaks or accident sequences so as to maintain Auxiliary Feedwater Systeth integ-rity to meet Standard Review Plan criteria. (Findinos 57, 58, 59, 60)

Conclusion Based upon the uncontroverted evidence in the record, the Board finds that Applicant's stated intention to implement the Westinghouse recomendations; without demonstration that preoperational procedures or operation plans being developed will specifically address feed M line breaks or accident sequences

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. and changes currently comtemplated by Staff, does not constitute " appropriate protection" for the steam generator Auxiliary Feedwater System against the dy-namic effects of KRSKO-type waterhanner events occurring at Byron. Furthermore, the Board finds that there has been insufficient determination of the nature of the KRSKO event and it's generic implications to conclude to conclude that pos-sible recurrences of it at Byron do not constitute a significant health and safety concern, particularly given the test nature of the plant with respect to the Westi.nghouse recommendations.

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e FINDINGS OF FACT DAARE/ SAFE Contention 9(a) - Waterhammer

1. "The actual review and/or evaluation for the design for or avoidance of water hammer is normally reviewed through differ-ent portions of the safety review plan." (Serkiz, Tr. 1012)

2. The KRSK0 waterhammer event was a " bubble collapse" type. (Carlson, Tr. 930) 3 Applicant, Staff, DAARE/ SAFE, and the League stipulated by an agreement dated ' February 15, 1983, that, the final language of-DAARE/ SAFE Contention 9(a) shall read as follows for litigation:

During recent start-up tests at the KRSKO plant in Yugo-slavia, which has steam generators which are similar in de-

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sign to those at Byron, the plant experienced a bubble col-lapse waterhammer event in the feedwater bypass line. Ap-plicant should be required to demonstrate that a similar event will not occur at Byron.

4. The waterhammer apparently occurred-during Hot Functional testing of th Auxiliary Feedwater System pumps in July, 1981, but

. damage was not discovered till early August, 1981. The first in-dications of the waterhammer event were the discoveries of blist-ered paint on the pipes of the Auxiliary Feedwater System as far

'back as the motor driven pumps, movement of several pipe hangers, and piping, and:a quarter-inch bulge on a six to eight inch sect-ion of the bypass piping within containment near the secondary shield wall. (Carlson, Test. 8, 11-12) 5 Dyron ar.d KRSK0 share the same model of steam generators, the Westinghousa Model D preheater counterflow type steam genera-tor. They have a common design of feedwater systems which serve those steam generators. The Feedwater Bypass System was specif-9 d

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(2) ically designed to limit the possibility of waterhammer events in the preheater section of the steam generator which is located in-side the lower shell of the vessel adjacent to the main feedwater nozzle. The Feedwater Bypass System accomplishes this purpose by diverting cold feedwater to the auxiliary nozzle through the feed-I water bypass line. (Carlson, Test., pgs. 5-8)

6. As a result of the event, the section of bypass piping containing the bulge was replaced. Also the hanger damage was re paired, and the check valves were refurbished. (Carlson, Test.,

13) 7 The KRSK0 event is believed to have occurred during hot functional testing in July of 1981. Because of the nature of the testing and the damage observed Westinghouse camento;the'.:conclus-ion that a bubble collapse water event had occurred, although its not possible to specify exactly what the conditions were when it happened. (Carlson,Tr.,108'd-1088)

8. The cause was attributed to backleakage through auxiliary feedwater check valves "which were known to leak" and were later refurbished. (Serkiz, Test., 2: Tr., 951) 9 The waterlevel in the steam generator fell below the 4

discharge end of the internal extension of the auxiliary norzle, thus allowing steam to flow out through the auxiliary nozzle and into the Feedwater Bypass System piping. With steam present in the bypass piping, the Auxiliary Feedwater System motor driven pumps were started as part of Hot Functional Testing, thereby in-tro'ducing' cold water,into the bypass piping. The cold water ra-pidly condensed the steam and thus caused the waterhammer. (Carl-e

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(3) son, Test.,-9-10: Tr., 1066-90) .,

11 0 . The corrective measures Westinghouse has recommended ares (a) maintain steam generator water level above the auxiliary feed-water discharge pipe-inside the steam generator, (b) at low load' or hot-standby conditions, the operator is instructed to supply feedwater continously as much as possible. (c) instrument the piping upstream.of the steam generator auxiliary feedwater nozzle to' monitor temperature for detecting the onset of steam backleak-age, and, proper maintance of check valves. (Serkiz, Test., 3:

Carlson, Test., 12-13, 16)

11. The temperature monitoring system will consist of temper-ature sensors on the feedwater piping adjacent to the auxiliary feedwater nozzle on.each of the steam generators at the Byron sta-tion, which will feed information to the plant process computer,

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programmed to alarm when an abnormally high temperature is detect-ed in the bypass piping. (Pleniewicz,d T est., 4: Serkis., tr., 1000) w 12, Temperature sensors will provide continous checking on check valve leakage, and during refueling and maintanat outages one of the six inch valves and two of the eight four inch check valves will be inspected. (Pleniewicz, Tr., 1109,~1108) 13 The type of temp)erature sensors used will be RTD's (Plen-iewicz, Tr. 1106)  !

14. There have been cases of RTD's failing. (Pleniewicz, Tr., 1106) 15 It is possible that a schedule of check valve or sensor maintance might be valuable in predicting the probability of water hammer bubble collapse occurrance at a facility. (Serkiz, Tr., 1004)  ;

. l'7 Mr. Serkiz is not familiar with either maintance or in--

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n (4) spection proceedures or matters of that nature with respect to the check valves or temperature sensors at the KRSK0 planth '(Serkiz, Tr., 1003) 17 Mr. Carlson is familiar with the application of check val-ves in systems: their purpose, but not with the more operational l

consideration such as valve maintenance, leakage rates, etc.

(Carlson, Tr. 907) l

10. ihe recommended refill rate was derived from an analytic-al study done by the Westinghouse R & D. (Carlson, Test., 13) ,

i 19 If backleakage is detected, the piping should be slowly refilled or the plant brought to a cold shutdown condition, dep-1 ending on the circumstances. (Carlson, Test., 16)

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20. Edison is developing procedures which will instruct the reactor operator, if the temperature monitoring system indicates backleakage. to slowly purge the bypa s piping of the steam or hot water by introducing feedwater into the bypass piping through the tempering line at a flow rate as close as possible to the 15 gpm recommended by Westinghouse. (Pleniewicz, Test., 5)

21. The Hot Functional testing will determine the ability .

of the tempering flow system to achieve the low flow rate recom-mended by Westinghouse fo'r refilling of the bypass piping. (Plen-iewicz, Test., 7)

22. In general, the water level in the steam generator, unless it's-under an accident sequence such as a feed line break or tur-bine trip, would not fall below the main or auxiliary feedwater nozzles. (Carlson, Tr., 1062, Pleniewicz, Test., 6) 23 The KRSK0 water hammer event is within the purview of Un--

resolved Safety Issue A-1, Waterhammer. (Serkiz, Tr. 1010)

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24. 24. Waterhammer is treated as a generic issue by the NRC yet, every occurance of waterhammer, including bubble collapse l waterhammer is considered to be plant specific. (Serkiz, Tr., l 1009-1010) 25 Staff does not have a task force studying waterhammer.

(Serkiz, Tr. 949) l

26. The Auxiliary Systems Branch and the Reactor Systems l Branch are the primary NRC branches involved in reviewing water-

! hammer. (Serkiz, Tr., 949) 27.- Staff has not directly investigated the KRSKO water-hammer. event. Staff has only visited the facility recently as part of the IAEA investigation of Flow-induced Vibration at the plant. (Tr., 1022-1027)

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28. Serkiz was responsible for conducting the NRC evaluation of the KRSK0 event, the KRSKO and Byron plant designs, and the Westinghouse recommendations.w(Serkiz, Test., 1: Tr., 948) 29 NRC Staff's review of the KRSK0 event has rel$ed upon in-

[ formation recieved from Westinghouse and Commonwealth Edison. (Ser-kiz, Tr., 949-952, 957)

30. Staff information on the KRSK0 event has come from a meet-ing with Westinghouse andlCommonwealth Edison staff on July 27, 1982, and a September 9, 1982 memorandum. (Serkiz, Test., 2)

31. Staff used it's information about the KRSK0 event to, eval-l l uate-the generic implications of-bubble collapse waterhammer to pre-heat steam generators. (Serkiz, Test., 958)

32. The Staff position that the KRSKO event is plant-specific and not generic in nature is based upon the generic review in NUREG '

3090, " Evaluation of Waterhammer Potential in Preheat Steam Gener-4 L A.

,u (6) ators," December 1982. (Sirkiz, Test. 5) 33 Staff did not participate directly in drawing up NUREG-3090, but Serkiz provided the contractor with the information it.

used to evaluate the KRSK0 event, and design specifics for the McGuire, Summer and Byron plants. (Serkiz, Tr. 973, 974)

34. Other than the same information provided Staff concern-ing backleakage,.the NRC could not obtain explicit details of the conditions at the time of the event, including the type of pre-operational testing underway whether procedures were being fol-lowed or some type of specialty tests being performed. Lacking the specifics on what was going on, Staff categorized the KRSKO event as a plant specific event and not generic in nature. (Ser-kiz, Tr., 1027-1029) 35 Staff's conclusion that the KRSK0 event was plant spec-ific and not generic was not intended;te imply it could not oc-(Serkiz, Tr. 1028)

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cur in domestic reactors.

36. The KRSK0 event reveals that a waterhammer ($ue to bub-ble collapse ) can occur in a plant which employs preheat steam generators. (Serkiz, Test., 3: Tr., 972) -

37 Westinghouse's recommendations constitute good engineer-

't (Serkiz, ing design practices and prudent operating procedures.

Tr. 962)

38. Serkiz statement is based upon the assumption that good engineering design practices and prudent operating procedures will be followed. (Serkiz, Tr. 968-969: 965- 967) 39 Upon that basis, Serkiz is able to conclude that if those corrective measures recommended after the fact had been in place at the time of the event, particularly the continous feedwater O

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, at the time of the' event, particularly the continous feedwater flow s m in the auxilimry feedwater line, it would likely'not have occurred.

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(derkiz Tr. 62)

. / y,0. Thatdoesnotmeanpehasnotknowninstancesof-faulty '

' ~ desighoroperation.(Tr.969,Serkiz)

\ 41. Applicant has indicated that warming flow to the auxiliary' N ,

nozzle will be maintained during all phases ofspower operation, ex- -

cept.the heat-up phase. (Serkiz, Test., 4) s

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. s hy. During the nor al operations of heat-up, cooldown, and w

'y hot standby, feedwater,is supplied only through the auxiliary nozzle.

However.,only' relatiseiy small amounts of feedwater are required, (:

i ws not always enough to permit ai ontinous flow. The opportunity d,oes s

exist for backleakage if 3te check valves fail and low water level

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l occurs. (Carlson, Test. ,11) 43., TheKR,SK0 water 6ammereven)didnotcompromisetheability e,

oftheaffectedcystemstofune*,1Nn. (Carlson, Tr.,.1091) ,

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44. There would be no consequenced if*a_KRSK0; type waterhammer event of tiie same. madnitude occurred at Byront there 4ould be no '

breach of the primary coolant-syetem and thus no release of' rad-iation. (Serkiz, Tr. 1,019, 1020) 45 That the KRSK0 gvent was at the upper end of the spectrum of possible bubble collapse waterhammer events involving that plant l- system is evident from the extent of the damage. (Carlson, Tr.,

1111)

46. If the KRSKO event had been larger (which it is conceiva-ble it could have been) the pipe could have ruptured. (Carlson, Tr. -1110) 47 It should be clearly stated that waterhammer will contin- '

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s (g) ue to occur. (Serkiz, Tr., 982: Carlson, Tr., 1130)

J 48. The number of instances that waterhammer would occur over

~the lifetime of a steam generator cannot be predicted. (Serkiz, N,.e Trs, 982) "

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49 The feedwater bypass system was developed and implemented i,o reduce the possibility of bubble collapse water hammer occurring in the preheater section of the steam generator, following an ex-perimental program conducted by Westinghouse to investigate that possibility. (Carlson, Tr., 1045)

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! 50. No testing evolved from that program or prior to the KRSKO event which could have led Westinghouse to conclude that the bypass system,woyld be successful in minimizing preheater bubble collapse

% waterhammer, without in turn, inducing it in the bypass line itself.

.- x ;;, ' ,

(Carlson,Tr., 1056-1061)

.. ( .

(; ,' l 1Q p 51. Westinghouse has recommended either replacement or removal 7^ I of fast-acting check valves located hear the auxiliary feedwater

(,

~

nozzle in Auxiliary'Feedwater Systems because it is concerned s ' over ossible " acoustical" or classical waterhammer o6 curring'in

^

'N that location, against those valves,'in the event of a feed-line w

[a>-- d s .

L J break. Edison has chosen to remove rather than replace the valves l

5 at Byron. (Carlson, Tesp., 14, 15: Tr., 1113, 1114)

. s t .. ,

5, 52r The results of a bubble-collapse waterhammer and classic-s'. al waterhammer events could be the same in their effects on pip--

-s -

[ (Serkiz, Tr., 986, 987)

i n'g s y s t e m s'.

- + t

'54. Waterhammer, whether classical or bubble collapse, will i -

\:

e _

The change in pressure has

-- result in a change ins water pressure.

J N ,D the potential forfdamaging componentr, of the piping system. The

) , (4 r

~ .

, 3 #

. ) ,

, "(9) i pressure change, if large,enough, may result in pipe deformation, or in an extreme case, rupture. It may also result ,in valve dam-

- / ages for example,' damage to valve packing and gas'ieta. .The change bh. in water pressure inside the system is accompanisd by fora,e'? trans-mit,.ted to the pipe supports. (Carlson, Test., 5) 55 There are fatigue factors associated' hith bubble coliapse f

waterhammer occu'tring in the preheater section of a steam generator

! l 6

for the normal upset class of events. (Carlson, Tr., 1076) l

56. Bubble collapse waterhammer in tne prehenter region or in the bypass line bn at KRSK0 have the common eierents regardless

) ; ,

of where they ocodr,;with an enclosed, confined volume'of steam l being rapidly condensed when cold water is bro'ught l'nto contact '

. with it, dependent upon the geome,tries involved. (Carlson, Tr.', ' i 1075, 1076) ,

57. Westinghouse anticipates Bypass Systen f&ilure to occur on four ocas-sions within the 40-year lifespan of a steam' generator. (Carlson, Tr.,1080) e, ,

58. '1he initial susceptibility of the Byron steam generatcrs or feed-water system in the Byron 3tetion will be detennined durire preo'erational p

testing. (Pleniewicz, Test., 7; Serkiz, Test., 5)

59. NBC Staff is ccznterplatirg charges to the Standard Review Plan as resolution of USI A-1, Waterhammer. (Serkiz, Tr., 1012-1013)

60. The Byron plant will be the first operational plant which will im-plement the Westinghouse rewme.Jeations and which will, essentially have a l

feedwater systen representative of the type of feedwater sytan KRSNO had at the time of the water hammr, as KRSIO's has now been modified to accamond-ate nodifications to limit flow-induced vibration. (Carlson, Tr., 1099,1101)

I l

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