ML19325E691

LER 89-012-00:on 891003,plant Operators Received Indication That RWCU Sys Experiencing High Differential Flow Which Resulted in Isolation of Primary Containment Isolation Sys Valves.Caused by Component failure.W/891031 Ltr

ML19325E691
Person / Time
Site:	Hatch
Issue date:	10/31/1989
From:	Hairston H, Tipps S GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
0365V, 365V, HL-808, LER-89-012-01, LER-89-12-1, NUDOCS 8911080272
Download: ML19325E691 (7)

Text

_ . _ _ _ _ _ _ _ _ _ _ _ _

f,: ,

e av %, ctnw,,

enemven, ,

's s 4'lon Goato a 3330h i

, . . 1NopNv4 4D4 'M 3195 '

I-vusnou urm 43 inAvretst Center FyLway ,

i P0bt OffiCf dot 1E95 liitm4rg'iam. Alatein 3520) {

t itMh0% 005 (46 bbf;1 i I

Ut*, w emt4<;IT.O, rem )

W G. Hatraton, til

$enitw W4 bit +0 erd 4 h'p0lO&f OpefAOC#iB k HL-808 0365V October 31, 1989 ,

t U.S. Ruclear Regulatory Commission ATTN: Documint Control Desk r Washington, D.C. 20555 l

[

PLANT HATCH - UNIT 1  !

NRC DOCKET 50-321 i OPERATING LICENSE DPR-57  !

LICENSEE EVENT REPORT i LEAKING RELIEF VALVE LIFTS CAUSING BIACTOR WATER CLEAN-UP ISOLATION i Gentlemen:

(

In accordance with the requireatats of 10 CFR 50.73(a)(2)(iv), i Georgia Power Company is submitting the enclosed Licensee Event Report i (LER) concerning the unanticipated actuation of an Engineered Safety This event occurred at Plant Hatch - Unit 1.

Feature. i Sincerely,  !

N. G. Hairston, III  !

SHR/GKM/eb

Enclosure:

LER 50-321/1989-12 i c: (See next page.)  !

?

f 9

8911080272 891031

/I  :

PDR ADOCK 05000321 gI G PDC

i l

e .

(i$c$glali>ntr adh. l i

U.S. Nuclear Regv'atory Commission Li october 31, 1989 {

'j '  :

Page Two l 1

c: Georgia Power Comoany l Mr. H. C. Nix. General Manager - Nuclear Plant  !

Mr. J. D. Heidt, Manager Nuclear Engineering and Licensing - Hatch- l GO-NORMS l

t U.S. Nuclear Regulatory Commission. Washington..D.C. i Mr. L. P. Crocker, Licensing Project Manager - Hatch i U.S. Nuclear Regulatory Commission. Region II l Mr. S. D. Ebneter, Regional Administrator  !

Mr. J. E. Menning, Senior Resident Inspector - Hatch  !

?

i i

k i

I l

l i

i l

i I

i r

0365V

F asenovo ow wo ameim LICENSEE EVENT REPORT (LERI * * *'a' * ' 80" t

. .o6. , , . ni ca . ii =v... a u. ma PLAILLJtATCH. UNIT 1 0 161010101312 11 1 IOkQji LEAKING RELIEF VALVE LIFTS CAUSING RTU ISOLATION t vt =, ca n > ii . =t . . it, ...oni .n in or n e acitn. =vomo mi wDhTH DAY vtah t i a.i 'Q( ,,

j 6 ,',d ,7,Q MOh1H Dav ita t .

• DL11 t h awl 8 DLM 4 41 %vwDial8' 0161010101 1 1

~ ~

1 l0 O! 3 8) 8l9 0 l1 l 2 0l0 ll 0 3 l1 8!9 0 1 61 0 1 0 1 0 1 1 I

,,,,,,,,,, v.u neon, . .v.= urn o evneva=i vo ,HS miovi. . un o, n u n e ,o . ., . ., . ,,, mi  :

"'* 5 a *omi no ni.iun i nnai a *asi.i l

n oi.inno . so ni.nu ee ni.nen.i n m.i

, , 1 io i 0 . .,n n , . .i . n.n.n..,

n oi.inniii, o n.nlno o ni.n n.iiin i m.,,,

- ,g 7,,,,, .

30 ao6i.ninut .013 l13 H.) .0 tBi.iiinvu.Hel

1. 9 4861.il1Hel M 934.*ittlan .0 tai.ittnal LiCO N64 8 contact DDR THit 48 A till Niet fit lPHO49 NUMD4M Ah6 A (Q00 Steven D. Tipps. Manager Nuclear Safety and Compliance. Hatch 91112 31617 I -17 l 81511 COMPLtit DNE t>44 00014 ACH C0sdPONtWT f A144 fat in tchietD QN THl$ lilPOflT ()Si CZE $ttflM C CsMPOh t N1 0

T p',,[g CAu&l S t IT E M COM'ONINT S '

lO I 1 1 I l I l 1 I I i 1 1 1 I I I l l 1 1 I I I I i i i pts.YttutWT AL PtPORT l aPICit0 Het MONIH DAT VI A.I iit fit ..6 temp N i.PlCHO SV0WSSION OMib NO l l l aw r _ ac, ,o .. . . . . ,..-. .a . . . . w n ei On 10/03/89, at approximately 2315 CDT, Unit I was in the Run Mode at an approximate power level of 2436 MWt (approximately 100% of rated thermal power). At that time plant operators received indication that the Reactor Water Cleanup (RWCU) system was experiencing high differential flow. This resulted in the isolation of the Group 5 primary Containment Isolation System valves. Plant equipment operators inspected the RWCU system and determined that no leakage had occurred outside the system. When no system problems could be identified which would have caused the isolation, -

operators concluded that system operation could be safely resumed, and the system was returned to service by approximately 0400 CDT on 10/04/89. A subsequent and more detailed investigation revealed elevated temperature on the tailpipe of relief valve 1G31-F3058. This valve was apparently leaking to the radwaste system and thus no water or steam had been observed during the initial inspection.

The root cause of this event was concluded to be component failure.

Elevated tailpipe temperature showed relief valvo 1G31-F3058 was leaking past its valve seat. The leakage exposed an increased proportion of valve seat surface to high pressure water and flashing steam, thus decreasing the lift pressure setpoint, leading to a spurious blowdown of the RWCU l system, followed by the isolation caused by the leak detection system.

Corrective actions for this event includea functionally testing and calibrating the differential flow instrumentation and replacing the l

leaking relief valve with a new valve.

L "x"U"-"

g

=ac ee. men v cucm. cerumon co >oa l LICENSEE EVENT REPORT (LERI TEXT CONTINUATION maono w wo moe sums s n a f actuf t haa,6 tln DMt 41 w6sambt t 636 gg,wg egn ei page tai

. .. "tu;;~ ~ 's,n PLANT HATCH, UNIT 1 016101010131211 81 9 -

0111 P -

0 10 012 0' 015 PLANT AND SYSTEM IDENTIFICATION General Electric - Boiling Water Reactor Ener as (gy EllsIndustry Identification System codes are identified in the text Code XX).

4HMARYOFEVENT On 10/03/89, at approximately 2315 CDT, Unit I was in the Run Mode at an approximate power level of 2436 MWt (approximately 100% of rated thermal power). At that time plant operators received indication that the Reactor Water Cleanup (RWCV, Ells Code CE) systen, was experiencing high differential flow. This resulted in the isolation of the Group 5 Primary Containment Isolation System (PCIS, Ells Codo JM) valves. Plant equipment operators inspected the RWCV system and determined that no leakage had occurred outside the system. When no system problems could be identified which would have caused the isolation, operators concluded that system operation could be safely resumed, and the system was returned to service by approximately 0400 CDT on 10/04/89. A subsequent and more detailed investigation revealed elevated temperature on the tailpipe of relief valve IG31-F3058 (E!!S Code RV). This valve was apparently leaking to the radsaste system (Ells Code NE) and thus no water or steam had been observed during the initial inspection.

The root cause of this event was concluded to be component failure.

Elevated tailpipe temperature showed relief valve 1G31-F3058 was leaking past its valve seat. The leakage exposed an increased proportion of valve seat surface to high pressure water and flashing steam, thus decreasing the lif t pressure setpoint, leading to a spurious blowdown of the RWCV system, followed by the isolation caused by the leak detection system.

Corrective actions for this event included functionally testing and calibrating the differential flow instrumentation and replacing the leaking relief valve with a new valve.

1 D_ESCRIPTION OF EVENT At approximately 2315 CDT on 10/03/89, with Unit 1 in the Run Mode at rated thermal power, plant operators received control room annunciation indicating a high differential flow condition existed in the RWCV l system. At that time there were no maintenance or surveillance l activities in progress. Operators imediately checked the differential flow meter and found it reading approximately 75 gpm, compared to the RWCV system differential flow trip setpoint of approximately 56 gpm.

The assistant plant operator throttled total system inlet flow in an attempt to correct the differential flow condition. When the 45-second time delay for the high differential flow cor.dition expired, a Group 5 isolation of the primary containment isolation system (PCIS) valves 1G31-F001 and F004 occurred per design.

. . . . , . . u s amm o n< sn ais L

r ri .nc ..;. m v , m.m.waion, ca. inio ,

UCENSEE EVENT REPORT (LER) TEXT CONTINUATION **aom o e =o nuo. ,

i .ais e n =

l

. .c s, . . , n , m.. .s . , , , , , . . , , , ....,,,

i.a "m;r ':03.7:

l

! PLANT HATCH, UNIT 1 o 1610 lo l o 13 [211 8 19 0 l1 l 2 -

0D 0 13 0' 0 15 '

I Upon receipt of the isolation, the Shift Supervisor dispatched plant equipment operators (PE0s) to the three principal areas of RWCU system piping and components: the RWCU hest exchanger room, the RWCU system pump room, and the RWCU system " valve nest". The PL0s found no visible system leakage. When no system problems were identified which would have caused the isolation, operations personnel concluded system operation could be safely resumed. Therefore at approximately 0035 CDT on 10/04/89 the Shift Supervisor ordered the RWCU system returned to service, and this action was completed by approximately 0400 CDT.

Since all control roo:a indications were that this isolation occurred in response to a valid signal, investigation focused on possible modes of system leakage which would not have been apparent to the PE0's who had i first inspected the system following the isolation. Therefore measurements of relief valve tailpipe temperatures were taken to check for steam leakage. The tailpipe of relief valve 1G31-F3058, located on i the shell side of the RWCU regenerative heat exchanger 1G31-B001 A (Ells Code HX), measured 1700F whereas two other similar valves measured 1020F and 1050F. This indicated some steam leakage past the valve ,

seat. The relief valve 1G31-F3058 was replaced on 10/18/89.

CAUSE OF THE EVENT lt was concluded that the root cause of this event was component "

failure, i.e., a degraded relief valve,1G31-F3058. Because the '

tailpipe of relief valve 1G31-F3058 was found to have elevated temperature compared to similar valves in the system, and because the lif ting of this relief valve would have caused the RWCU system to  :

isolate on the high differential flow condition, it was concluded that the valve had in fact lifted, causing the event.

The mechanism of failure is that relief valve leakage exposes an increased proportion of the valve seat surface area to high pressure water and flashing steam. This can decrease the lift setpoint due to the additional steam force applied to the larger exposed surface area of the under side of the va'ive seat. Thus in the leaking condition, 1G31-F358 is believed to have opened spuriously, causing a blowdown of its associated heat exchanger and inducing a condition of high differential flow between the lines entering and leaving containment.

The RWCU system then isolated as designed to mitigate the consequences of a pot 3ntial system leak.

.u w.o m. o.u sw 4, g.,,o.. .

L)CENSEE EVENT REPORT (LERI TEXT CONTINUATION **aoiio ove =o im-em >

iaiais e rie f &CittTy haast tu poc a e T erveste a tai 4 4

• t#ptatt R i.e .*64 (3' ,

ma tup. WJ,n PLANT HATCH, UNIT 1 o p l o l o l o l3 [' 1 1 89 1

011 l 2 - 0p 0 14 sor 0 15 REPORTABILITY ANALYSIS AND SAFETY ASSESSMENT This event is reportable under 10 CFR 50.73 section (a)(2)(iv) because an event occurred which resulted in the unplanned automatic actuation of an engineered safety feature (ESF). Specifically, the RWCU isolation >

valves,1G31-F001 and 1G31-F004, closed in response to an indication of ,

high differential flow between the pipes entering and leaving .

containment.

The purpose of the RWCU Leak Detection System (LDS, Ells Code BD) is t0 t detect leakage in the prccess flow of the RWCU system external to the primary containment and to mitigate the consequences of such leakage.

This is accomplished by utilizing leak detection instrumentation which initiates closure of the PCIVs upon detecting a parameter indicative of a system leak.

Once of the methods used for detecting system leakage is flow comparison of the RWCU system influent and effluent. If the influent exceeds the effluent by at least 56 gpm for 45 seconds, a high differential flow condition exists and an isolation of the Group 5 PCIVs is initiated. In the event addressed in this report, an actual high dif ferential flow  ;

condition existed resulting in an isolation of the Group 5 PCIVs. i Investigations conducted by the PE0's immediately following the event proved that no leaks to the atmosphere existed from system piping and valves outside primary containment. The leaking relief valve was not discovered at that time because it exhausts to radwaste system piping such that its effluent was concealed and therefore not visible to the PE0's. Moreover, since the relief valve exnausts to the radwaste system, all effluent was completely contained within plant systems designed to handle it. Required reactor (oolant sampling was initiated in accordance with Unit 1 Technical Specifications section 4.6 F.2.a.1.  !

Reactor water conductivity experienced no excursions during the event.

Based on the above analysis, it is concluded that this event had no adverse impact on nuclear safety. Since the isolations occurred at rated thermal power, it is concluded that this event would not have been ,

more severe under other operating conditions, gRECTIVEACTIONS v

Corrective actions for this event included:

1) performing a functional test and calibration on the RWCU system differential flow sensing equipment to verify proper operation of the instrumentation and trip logic. This action is completed. '

2) removing and replacing heat exchanger relief valve 1G31-F3058.

This action is completed.

g.oa. . . v . w ... o en o. J.

{ l 4 4

• w ,J; n v i .ucau e uuvao., c-imim UCENSEE EVENT REPORT (LER) TEXT CONTINUATION .~.oiso oue uo .m-em o in. n . ,i .

..mn, n, ca. i . .m . a, ,,,,,,,,...,, ...,,,,

l'

.n.. "ttw  :%',t:

PLANT HATCH, UNIT 1 o p to jolo13l2 11 8 l9 .-

0 l1 l 2 Op 0 l5 or 0 l5 m . . c % mm,nn ADD 1TIONAL INFORi% TION

1. Other Affected Equipment:

No plant systems other than the RWCU system were affected by this event. No surveillances or proce: lures were involved in this event.

2. Previous Similar Events

r Similar events in which the RWCU system isolated due to high differential flow were previously reported in the following LER's: ,

50-321/1989-001 dated 03/06/89 50-366/1988-015 dated 08/26/88 ,

50-366/1988-021 dated 09/21/88 The corrective actions for these events included revis..., dt.fective procedures, repairing and replacing valves, and counseling persor.nel involved in the previous events. These corrective actions would not .

have prevented the event addressed in this report because no procedural deficiencies were involved, the valves repaired or replaced were l

different from the one which is believed to have caused this event, and ,

because personnel error did not cause this event.

3. Failed Components Identification:

Master Parts List Number: 1G31-F3058 Manufacturer: Consolidated Valve Company ,

Model Number: 1975T  :

Typo: 3/4-inch Relief Valve l Root Cause Code: EBAA ,

l Manufacturer Code: C568 l EIIS Component Code: RV EIIS System Code: CE '

l Reportable to NPROS: No 1 ,

l f,. .. . .v. m ne. . .s.

!