ML20092J232

Forwards Detailed Description & Evaluation of Turbine Bypass Transient on 840528,per 840531 Meeting W/Nrc & Util 840606 Rept 7-84, Investigation of Unit 2 Power Transient of 840528

ML20092J232
Person / Time
Site:	Susquehanna
Issue date:	06/08/1984
From:	Kenyon B PENNSYLVANIA POWER & LIGHT CO.
To:	Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20090A536	List: ML20092J232 ML20092J239
References
PLA-2229, NUDOCS 8406260398
Download: ML20092J232 (6)

Text

- -

l' . tn

. NJCLEAR DCPT R LENTCEN GO P.02 ,

@ Pennsylvania Power & Ught Company l Two North Ninth Street

• Allentown. PA 18101

• 215 l 770 5181 Stuce D. Kenyon Wee MeaWent.Nueber OpereWone i miserm.nse JUN 0 81964 - .

Dr. Thomas R. k riey Regional Administrator. Region 1 , y, U.S. Nuclear Regulatory Commission 631 Park Avenue t

Eins of Prussia. FA 19406 8USQUEHANNA $ TEAM ELECTRIC STATION TUnsINE BYPAS$ TRAN51ENT

• IR 100508 FILE $41 FLA-2229 Docket No. 50-388 Dear Dr. k riey

['

As a followup to our meeting with your staff as May 31, 1984, attached is a . '

detailed description and evaluation of the turbina bypass transient which occurred at Susquehanna SE8 Unit 2 on.May 28,1984. Also attached is the NSAG h report on the transiaar. '

Yery truly yours, b' i

e

3. D. Eeny Vice President-Nuclear Operations Attachment ces R. W. Staroetecki = NRC Region 1

1. W. Jacobe = NRC Resident Inspector R. L. Perch - NRC Bethesda * '

b P

1,

? .

64 / y.

4. ..

NJCLEAR EEPT R LENTC4ri to P.03 1

Attachment 1 l FLA-2229 Turbine trusse Transient Following shift turnover on May 27, 1934 Operatione pereoanel began establishing plant conditions to perform the RCIC controller het functional tune-up test (NF-250-010). The INC pressure setpoint wee reduced from an fattial value of appremiastely 950 pSIG to 920 PSIG at the completion of CED seres time testing at 00:10 on May 28. 1984. Control rode were them withdrawa -

to inerasse resetor power to open the #1 turbine bypass valve to approminately 502 to ensure adequate pressure control during the acIc hot fumational test.

Steam dilution flew to the secondary Steen Jet Air Ejector ($ JAI) began to oscillate (+/=130 lb/hr) at approximately 23:50 based on strip chart recorder data. This corresponde to the decrease of the EMC pressure setpoint. At approminately 00:45 the SJAR eteam flow increased from 9400 lb/hr to 9650

• lb/hr se reactor pressure increased. The flow then decreased to 9400 lb/hr as ,

resetor pressure decreased.

At approaimately 01:00 a control rod was selected and withdrawn. This action directly preceded an increastas emplitude oscillation of turbine bypass valve positten as the #1 bypees valve re-poettioned to maintala pressure setpoint.

The assillation induced roaster pressure and bypese steem flow perturbations which apparently induced effgas system eteam dilution flow oseillations.

Variations in the effgas system flow rate would have a negligible effect on reactor pressure and would not be espected to influence EEC operation. The offges system oscillations were further complicated by the fast that two root valves to the offsas main steen pressure reducing centro 11er (PC-20701A) were teolated c.ueing the pressure control valves to be open fully. A review of previous escillations in the SJAE eteen fisw showed two oscillations occurred on May 27, 1934 when reactor pressure was adjusted. Had the pressure '

regulating valves been operable. the oscillations would have been dampened.

Offgas teolated on low steam dilution flow at approximately 01:01:03 due to the oscillatione in the steam flow caused by the increasing magnitude of the '

oscillations in the total bypass valve espaatty. This generated the first indication to the plant control operator (PCO) that an abnormal plant condition existed. Subsequent engineering simulattene of the resulting transient support the suppeetties that the #2 turbine bypass valve opened at 01:01:15 which pressurised the #2 bypese valve diesberge piping and caused marrow range reactor pressure to drop to 894 PSIO. Data in the attached-Figure 1 shove an espected remeter pressure drop of 20 pounds based on mais steen line surge flow when two bypass valves initially opea. This correlates well with the recorded pressure deeresse of 19 pounds and recorded steen flow insrease. As roaster preneure decreased vessel level swelled to approsimately +53" due to increased.veid forestion and a EpCI high level trip signal wee generated. Procese temputer data ladiantes the bypass valves went

• fully elooed to recover reactor pressure. Vessel level dropped to 30" and the feedveter system, in automatic vessel level control using the low lead centre 11er (LIC-2R602), responded to the level perturbatten by increasing feedwater flow. The effect of resocor pressure increasing due to the bypase Valve closure provided a net reactivity incrosse end subsequest small power epike. -

e .

, ttJCLEAR ECPT R.1.INTOm (c. P.04 i

i 2

! The emaisua AFRM power level recorded in the Shitt Superviser and Startup Test loss during the tramasses was 102 on Ap M 'I'. This ApBN had a seia

adjustment fester of 1.85 as determined by startup Test (ST) 12.1 which would

' indiaate am setual power level of 5.45 rated power. This to supported by the fact that a red bleek wee received, however ne reseter seres signals were generated. Based oja APat settings for a red block at 112 indiested power and seven faaetion at let indicated power. and applying the current sais adjustaaet fastere for individual AFRN's the minimum power at which a red block would oscur was 4.42 estual' power. The minimum power at which a half serem would eseur yes 3.92 actual power. This would indicate that the actual power level reashed duttas the tranatest to benaded by 4.65 to S.95 rated j power. A separate treasiest power analyste using the actual IEN recorder I i traces, as adjusted by a Mot punctional test which correlated observed IRN readings to the aalibrated APEN readings indicates the initial power level .  !

wee 3.22 and that actual power reached during the tranatest was between 4.7X 1 and 5.02 rated power. - '

t '

4 Roseter pressure aestiaued to ineresse te a monimum value of 923 PSIG at '

l 01:01:44 et which peine turbine bypass valvee #1 and #2 re-opened t'a 343 of i total bypass valve espasity. Rosator pressure decreased to til PSIC and both ,

l bypase valves realesed at 01:01:33 to regulate pressure based on the pressure  :

setpoint. The #1 bypsea valve re-opened at 01:02:03 and oest11sted three times while attempting to stabilies reacter pressure. When pressure again oneseded the pressure seapoint at 01:02:5g the #2 bypese valve re-opened and a  !

i

{ assimum of 235 total bypese valve espasity was recorded by the process i I

semputer. Manimum reactor pressure reached prter to the second bypese valve <

operation was 924 PSIC. Figure 2 graphically depicts the total bypese valve 1

opea positten and marrow range reacter pressure reopense during the transient. ,

At 01:03:09 the #1 bypese valve reelooed and the #1 bypase velve etabilised .

reseter pressure at approainstely 918 PgIO. Minor resator vessel level swinge

and a power transiest less severe than the tattial power spikes slee escurred ,

durtag these embeequest bypass valve operations. '

1 To mitigate the transient. Operatione personnel began to insert control rode and placed'the feedwater low lead controllar in asaval to minimise further I vessel level oseillations. plaat aseditions stabilised at approminately 01:04 and the effgas system hydrogen resembiner was returned to service. Shift oupervistem, believing the effgas system had tuitiated the traseisat. then 1

! directed the pCO to meaually feelate the offsee system to proelude further f transient operaties. At 01:05:19 the asia steen supply (NT-20701A/3) to  !

i effgas wee iselsted. At 01:15 the Unit #2 recombiner wee shutdown and the  :

I asehemical vaevue pump wee placed is seretse. 27-2$0-010 and ST 14.2 (RCIC Quick Start to the Yeeeel) were satisfestertly esopleted at 04:34. ,

y i

j Subsequent plant staff 14C and General Electria inveettgaties of the WIC i .

pressure esserel and bypese valve sentrol legia indicated that all centrol fumettens were operating sermally. Plant staff Meehanteel Naistenesse investigaties of the #1 bypese valve revealed that a shipping haemer was found wedged between the bypees valve seat and the valve dise preventing the #1 bypese valve free fully closing. sinee the valve indicated fully closed en i

two oesseiens during the transient. At een be reaseeably soeused that the hemmer became ledged is the valve either duttag the final stages of the l

I e

9

- ._-,.-_ _,_._- -.,.,~,.m,. y_ - , _ , _ _ . - , - - - _,-___._-_.,_.-o,..c-- ,w-,----. ,.,- ,

/ MXLEM CCPT ALLENTOW1 CO P.05 3

.- transient or when plaat tenditions had stabilised following the tranatent.

N presease of the hessier is the vicialty of the #1 bypees valve may have impeded the steen flew rate through the valve possibly producing the pressure ineresse which preeipitated the initial observed bypese valve sea 111ation.

N ahipping her that was retrieved was the type typically used during welding precedures. The head of the hammer wee 6" wide and tapered to a point with a chisel design at the oppeetta and. Apparently the bypass vel */e. upon sleeing, severed the spring portion free the handle and the spetag wee leet la the main eendesser. Apprestaately 4" of the handle remained 1staat. The upper porties of the headle was flattened on both sidee due to operation of the bypass valve. Neehesteal interferesse of the bypass valve operation saused by either the hammer er the spring destee attached to the handle saa only be taferred but not samalusively deseestrated. Disaseeably of the #1 bypass valve ekswed small dents on the dise and the seat of the valve. All the deste em the dies appeared to be concentrated in an area approminately 1 square inch. The deste en the seat serresponded to the pene relative positten as on the dise. The seat see maahimed to remove the dente and the disc wee replaced due to the difficultiae in removing the old dise.

An evaluaties of the e*ent by PP&L's Engineerlag Analysie Group has determined that the event is less limiting them the main turbine trip without bypass transient from e30% power which is dieauseed in Section 13.2.3 of the FSAR.

N turbine trip event resulta in a greater reduction la steam flew and is

~ fattiated free a higher power level. The higher tattial power level resulte in a larger void ee11apee in the sore caustag a higher power spike. Secties 13.2.3.3.3.3 of the FSAR states that the turbine trip without bypsea event results in a high vessel pressure seren. Therefere. the peak power remaine below the flew biased simulated thermal power upeesle trip seapoint and the MCPR remains well above the GETAE safety limit. Sinee the lattial power wee lower the steem flew reducties and subsequent pressuriaation was less. The e

pressurisatten ineresse was attigated by bypese valve operaties, and therefore the event that securred on May 28. 1984 was lose severe than a turbine trip withe.ut bypese event free low power. -

e a e

b

?

t 4

0 S

.1. '

,' itXLDWt DEPT R.LENTCut GO P.06 l

l O

m M

g m

M o E -8~

9

, e.

O .

_g d

" >g -

0>

C 5

M

-0

.- c

$.I m

5 W

b o g g.

f 8 o-

% R 2 s (ISd) osoeaoed sansseJd ewoa lucets ao4ocoy '

ewe . . = .. . _ _ _ ~' - - -

w

......I T- ,

tilCLEAR DEPT R.LENTCidi 00 P.E7

. \

(OISd) eanssa.y ao46 oeg e6uos mo.uoM C

. . . h. Ni = w I i 1

=m O s - a o

,~~~,

emme .#

<r -

x -g g c- - g

. ..e

\ } --

~.

s - -___

e

~ ~ ~ ow 11 ' ' -.gg 8

N.

e -

g I

t

'~-3 A

. gg, p_r -

g ,

o- 2 s -- - -

r 1 .

~_

-l ggu )

~

lt 91 \

~- <[-

6 e ~i

• s; I

=

\ N<>

1 . . . . . . . .

_g

.. . ..mlg_

I . ..

f l o_ i

. > i i i -

o -C h '

(p4c1 }o %) uogisod e'AjoA ssedAe outcpn1 0