ML19354D468
| ML19354D468 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 11/01/1989 |
| From: | Gierich T, Pleniewicz R COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BYRON-89-1059, LER-89-008, LER-89-8, NUDOCS 8911090266 | |
| Download: ML19354D468 (7) | |
Text
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Commonwealth Edison
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, ) Byron Nuclear Station ,
( , 4450 North C ermin Church Road l
/ Byron,lillnois 61010 .
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November 1, 1989 ;
Ltts BYRON 89-1059 I !
U. S. Nuclear Regulatory Commission f
- Document Control Desk .
Washington, D.C. 20555 i
f ;
l Dear Sir .[
i The enclosed Licensee Event Report from Byron Generating Station is being l transmitted to you in accordance with the requirements of 10CFR50.73 as a Supplemental Report. ,
i This report is nwnber 89-006-01; Docket No. 50-454. !
Sincerely, i
R. Plenlewics fe4 Station Manager Byron Nuclear Power Station j RP/kr (0457R/0058R) ,
Enclosures Licensee Event Report No. 89-008-01 cc A. Bert Davis, NRC Region III Administrator ,
W. Kropp, NRC Senior Resident Inspector INPO Record Center CECO Distribution List ;
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Litt $tt EvtNT REPORT (LER) rgr,nov 2.0 Facility Name (1) Docket Number (2) Pane f31 8ttan.Jnit 1 -
013LDLDL9LaL5Lt._1Eil.0 l 6 Title (#) AUXILIARY FEIDWAf tR $UCTION PRE $$tet $WITCHt$ FOUND OUT OF CALIBRATION 00010 FAILURE TO CON 51 DER HEAD CORR (CTION lytaLDattlL _ LER Number _f61 ReggrLQale (71 Other Facilities Inse1ved (81 Month Day Year Year ///
jff Sequential /// Revision Month Day Year _ltcility Names Dotigt.Numberiti 77 llL BunktL._ llL, hunkt.t_
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POWER _._ 20.405(a)(1)(1) __ 50.36(c)(1) 50.73(a)(2)(v) 73.71(c)
Ltytt _ 20.405(a)(1 Hit) _ 50.36(c)(2) ___ 50.73(aH2)(vii) Other ($pecify
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//}//////////////////////// _ 20.405(a)(1)(v) _ 50.73(a)(2)(til) _ 50.73(a)(2)(x) Text)
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C$iRACT (Limit to 1400 spaces, i.e. approximately fif teen single-space typewritten lines) (16)
There were two related events involving the function and design of the Avulliary Feedwater (AF) Pump Suction Pressure $ witches (AF$P$s).
t UtiLinnt l
During an Institute of Nuclear Power Operations evaluation of the Auxiliary Feedwater System it was noted that the one AF Suction Pressure Transmitter (AF$PT) calibration was not head corrected. A Nuclear Work Request was written February 9. 1989 to make the head correction. Later it was determined that the remaining three transettters (two transmitters per unit) may also need head correction. On the morning of August 30, 1989, the AF$Pis were head corrected to the most Ilmiting case as a conservative measure. Per a 16tter from Sergent and Lundy, received on August 30 at approximately 1500. it was deterwined that the switch setpoints, corresponding to three of the four AFSPis, had not been within the Technical
$pecification allowable values. The root cause of the first event was that design documents and procedures addressing instrument installation and calibration did not clearly indicate that the AF$Pis required head correction.
$ttDAd_Ltini i
While investigating the impact of the first event on safety, the bases of the original setpoints were questioned. The spectfic question was whether the AF Pumps would rundown the Condensate Storage Tank (C$f) l l supply and induce air through the suction line prior to switchover to the safety related source or pump l
trip. As compensatory measures, the AF5PS setpoints have been set to conservatively high values.
I Also, conservative administrative Ilmits have been placed on the CST level (the normal source for the l Auxiliary Feedwater $ystem). Calculations have been performed to establish the final AF$PS setpoints and CST level requirements. The root cause of the second event was that the instrument setpoint calibrations i did not consider the cumulative effect of pump suction pressure drop with increased instrument uncertainty, ihls event is reportable per 10CFR$0.73 (a)(2Hi)(B) for operation in a cundition prohibited by our Technical $pecifications. There have been no previous stellar occurrences.
(0457R/0059R)
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l LICLitHLEyLtli REPORTJLERI TEKT CONT [tfyM10N I Fere Rev 2.0 FACILITY NAME (1) DOCKET NUMBER (2) ,,,,.t[R NUPBLR.(61 _ __ Pane O n Year fjj/
// $equential / Revision l
/// Number
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// NumlttI, l I
Jstsa.Jinit 1 015101010141.514._019 - 01018 - 0I1 01.11.(L1 s 1 TEXT Energy Industry Identification System (t!!$) codes are identified in the text as (xx) ,
A. PLANT C0lelTIONS PRIOR TO [YENT: l Event Date/ Time 8/30/a9 / 1100 I
Unit i MODE 1 . _ Power DegrAtigtL. Rx Power ,_1RQL RCS (AB) Temperature / Pressure _119fatl DetIAling. !
Unit 2 MDDE 1 = P. swat Qparation___ Rx Power SfL RCS (AB) Temperature / Pressure MorinaL0peratina. l t
- 8. DESCRIPTION OF EVENit There were two related events involving the function and design of the Auxiliary feedwater (AF)(BA) Pump
- I Suction Pressure Switches (AFSP$s).
First Event ,
It was noted that the one AF Svetion Pressure Transmitter (AF$PT) calibration was not head corrected. 1 The head correction requirement for the transmitter was questioned during an INPO review of the AF System at Byron. Resolution of the INPO concern was scheduled to be completed by September 1,1989. A Nuclear Work Request (NWR 8%4834) was written February 9,1989 to calibrate AF$PT IPT-AF051 (Unit IA Train) to :
compensate for the difference in elevation. Prior to recalibration, confimation was required on whether the pump centerline or the process tap elevation should be used as the basis for the head correction.
All four AFSPTs (two transmitters per unit) were located at or above the pump centerline, and therefore, l;~
had entsting setpoints that were conservative with respect to that elevation. However, three of the four AF$Pis were located below the process tap and, therefore, had setpoints that were not conservative with respect to that elevation.
l As a conservative measure, the AF$Pis had been calibrated to the head corrected setpoints based on the process tap elevation on the evening of August 29 and the morning of August 30. Sargent and Lundy ($&L) provided infomation in a letter, received at approximately 1500 on August 30, 1989, which stated that the process tap elevation must be used as the basis for the head correction of the AF$Pis. Once it was determined that the process tap level was to be used as the basis of the head correction, it was known l that the previous setpoints were not within the range of allowa' ole values in Technical Specifications.
Upon receipt of the August 30, 1989 $&L letter, this Licensee Event Report was initiated.
1 1
$aennd Event l
The Second Event involved the analytical bases of the original setpoints, which were questioned as a result '
of the evaluation of the first event.
. $6L was asked to review the first event for operability of the AF Pumps and evaluate any impact on safety. l l In a letter dated September 5,1989. $&L addressed the Technical Specification allowable values and the system safety analysis. Upon review of the $&L letter, the Station Technical Staff questioned the flow and
- l. frictional loss assumptions used in the S&L calculation. As a result, additional calculations were i
performed and revised conservative setpoint values were established on September 13, 1989. The AFSPS setpoints were changed to their revised values that evening. An evaluation has been performed to establish whether the AF$P$s would have been able to perf orm their design functions prior to the September 13, 1989, I
setpoint corrections.
(04$7R/00$9R)
LICIM1LL.IYLMI_R[I'Qfd tLCALILKLCQR11NUAfl0N Fo tIflty.2d.
. FACIL1TY NAME (1) DOCK [T NUMB (R (2) _,L(lLNWtBER f 6) J ege f3) i Year j/j/ Sequential /// Revision !
jjf ul,/ __Hwtea r UI __Humbat
.g gpn. Unit 1 0 1510 10l0lal$14 8191 -
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- oIi _91 3 or eLs itK1 Energy Industry Identification System (Cl!$') codes are identified in the tent as (KK) r
- 8. QL$mtfl0W OF EYENT (Continue 02 In conjunction with the switch setroint change, the level in the Unit 1 Condensate Storage Tank (0$f) (50) is being maintained above 90 percent as a conservative measure to prevent inadvertent suction source switchover to tssential Service Water ($X)(BI) during AF initiation. $1stlarly, the recomended minimum level for the Unit 2 C$T was set at 80 percent. The dif ference in level requirements is due to the AFSP$ i setpoint time delay relays installed on the Unit 2 Hotor Driven AF Pump which are not yet installed on the Unit 1 Pump. An additional administrative limit of 70 percent C$f level for both units has been leirosed as the point for initiation of the Limiting Condition for Operation Action Requirement for Technical
$pecification 3.7.1.3. This limit was estabilshed by a Comonwealth Edison Engineering letter dated September 15, 1989. This Ilmit assures that a minimum volume of 200,000 gallons is available for the AF !
System while the revised conservative setpoints are in place. On October 23, 1989, Engineering issued a fina) set of reconsnended switch setpoints and a safety analysis for the two events.
There were no other systems or components inoperable at the beginning of the event that contributed to the event. No personnel errors were involved, anc all operator actions were correct. This event is reportable per 10CFR$0.73 (a)(2)(1)(B) for operation in a condition prohibited by our Technical Specifications.
C. CAMLQf_1Ylhl:
fusLLYtAt The root cause of the first event was that the design documents and procedures addressing instrument installation and calibration did not clearly indicate that the AF$Pis required a head correction.
Consequently, no head correction was used when calibrating the AF$Pis. The head correction was a significant portion of the calibrated range of the instruments. Three of the four instruments (1PT-AF051, IPT-AF055, 2PT-AF0$$) calibrated without head correction had non-conservative settingt with l respect to the Technical $pecification allowable value.
SesoniLLytnt l
The root cause of the second event is that the Instrument setpoint calculations did not consider the
(
cumulative effect of revised pump suction pressure drop and the increased instrument uncertainty. This was necessary to demonstrate that the installed piping configuration would result in suction pressure conditions consistent with the AFSPS setpoints with worst case instrument uncertainty considered, l
i The AFSP$s have three design functions:
l l
- 1. To annunciate on low suction pressure to warn of an impending automatic switchover f rc<m the CST to l
I $K or an AF pump trip.
1 1
1 2. To automatically transfer the suction source of the AF Pump from a non-safety related source (C$T) to a safety related source ($K) prior to a loss of suction.
- 3. To automatically trip the AF Pump on low-low a suction pressure to prevent pump operation with an inadequate suction supply due to the failure of the automatic switchover function.
(0457R/0059R)
i LICfjpt[ EVENT REPORT (LERI TEXT CONTit M TION Form pov 2.0 FACILITY NAME (1) DOCKET NVPSER (2) LER Nupe[R (6) Page (3)
Year /// $equential /// Revision fff fff
/// _ Number /// _ Number.
JyrphJtdt 1 0 l $ 1 0 1 0 1 0,,jJJl 4 ff l9 - 010l8 - Ol1 01 4 QLjJ 1rti (n6rgy Indrstry identification $ystem (EII$) codes are identified in the text as (XX)
C. CAUSE of EVENT (Continutill:
The pressure values established for these setpoints are dependent on pressure drop through the system, on pump Net Positive $uction Head (NPSH) requirements, and on Instrument oncertainty of the pressure switches and strociated transmitters.
Calculations were performed to establish suction system pressure drop in 1977 and 1983. These calculations considered system flow to be 990 ppe per pump in accordance with the FSAR (Section 10.4.9.3) and assumed both clean (new) pipe and dirty (old) pipe. These calculations established that the pump NPSH requirements were met. The pressure drops resulting f rom these calculations were then utilised as input in calculations to establish AFSP$ setpoints that considered both pump NP$H protection and switchover of AF suction to $X.
Tb setpoint calculations utill ed methodologies and instrument uncertaintles consistent with the standard practice at that time.
Subsequent to establishing the instrument setpoints, the pressure drop calculations for the pump suction were revised to account for design modifications and to utt11:e new (computerited) calculational methodology. The modifications that were accounted for included adding a standpipe near the pump suction and increasing the site of the suction piping to reduce an observed suction pressure transient on pump start. Calculations were performed on a steady state and transient basis for these modifications to confirm that pump NPSH requirements were met. Because pump NPSH requirements were met, the AF5PS setroints were not revised as a part of the modification and calculations.
The AF$P$ setpoint calculations were revised several times between 1983 and the piesent to account for design modifications that replaced the AF$P$s and to (ncorporate changes in the instrument setpoint calculation methodology. These calculation revisions demonstrated that the switch setpoints were sufficiently above pump NPSH requirements to assume that suction pressure could not fall below NPSH requirements without switch actuation. These calculations cor.sidered instrument uncertainty.
D. SAFETY ANALY$1}!
To evaluate the safety significance of the as found situation (e.g., original instrument setpoints with no head correction included in the calibration), caleviations were done using the design basis assumptions from the UFSAR. These calculations determined that the most Ilmiting design feature is the ability of the pump to develop sufficient vacuum to reach the instrument setpoints including uncertainty. The vacuum is developed by the flow through the piping from the suction standpipe to the pressure switch tap in the suction pipe. The instrument uncertainty used for these safety significance calculations considered all i normal components of instrument uncertainty except seismic error consistent with the guidance provided in USNRC Inspection and Inforcement Manual Part 9000: " Technical Guidance", Standard Technical $pecifications l
$ection 1. These calculations also took credit for location specific temperature data.
I l
! (0457R/0059R)
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Ll(LM&I l lyLNI REPORT fLER) IIKLIQNIllfu&Il0N Fete Rev 2 9., ,
FACILITY NAM (1) DOCKET *#etR (2) LER NLDRER (61 pane (3)
Year /// $equential //j/ Revision fff ff
/// Number ULJughg.t,
_Istom_unii 1 0Is101010141514 819 - 01018 - 011 01 s or 01 6 TEXT Energy Industry Identification System (EXI$) codes are identified in the text as (XX)
D. 1 Mill &81ALYS15 foatinued!
The results of these calculations are susuiarized in the following table which identifies for each pump and <
each of the three switch functions, whether the trip setpoint could be achieved considering worst case instrument uncertainty:
114119A bat Al&In Sw.11thar.tr ltia Byron IA Yes No No Byron IB Yes Yes No Byron 2A Yes Yes No Byron 2B Yes No No This table demonstrates that the alarm setpoint was achievable for both pumps on both units, thereby identif ying low suction pressure to the operator and providleg him with the basis for manual intervention. ;
In addition, the switchover setpoint was achievable for AF pumps 18 and 2A, by providing automatic pump suction protection to one pump on each unit. Assuming worst case instrument uncertainty, the trip setpoint '
was not achievable for any of the pumps. The trip setpoint is not addressed in the Technical
$pecifications.
An additional calculation was completed to confirm that the Technical $pecification ilmit of 200,000 '
gallons of water was available prior to pump suction switchover to $X. This calculation utilfred the assumptions discussed above and confirmed that the Technical $pecification requirement was met for both ,
units.
During the time prior to taking the corrective actions stated below, there were no challenges to the Af System that required automatic source switchover to occur. Manual actuation of the AF source switchover
-was available thrtaghout the events. 3 As described below under Corrective Actions, new setpoints have been developed. Until these new setpoints are fully implemented, the conservative interim AF$PS setpoints and administrative limits on C$T level will '
be maintained to ensure that the AF system is capable of performing all required safety functions. At no time has there been any significant risk to plant equipment or to the health and safety of the general public as a result of these events. !
[. CORRLCIlyE ACTIONS in the Initle) event, conservative head corrections were made when the potential Technical $pecification vloistion was recognised. In the subsequent event, the setpoints were adjusted to conservatively higher values untti the calculations could be finall ed. In addition, administrative limits were placed on the l C$T 1evel to assure adequate suction for the AF Pumps.
t o
(0457R/0059R)
L((LM$1L_[y1MI_RL['QRf f LtR1 TEXY CONIINQATION Fere Rev 2.0 '
FA&lLITY NAME (1) DOCKET NV@[R (2) LER NU4tR (6) Pane (3)
Year j/jf// Sequential /j//,
p Revision di Number ML _MumhtI
.hf 96.MDit_.i 0 l B l 0 1 0 1 0 1_41_$j 4 8l9 - 01018 - 010 0l6 0F_ Q_j_6 TEXT Energy Industry Identification System (E!!$) codes are identified in the text as (KK)
E. (QRRECTIVE ACfl0NS (Continutjl.lt ,
New Ar$p$ setpoints and C$T level requirements have been developed as described below. Untti these new setpoints are fully implemented. the conservative interim AFSPS setpoints and administrative limits on CST level will be maintained. ;
Conservative assumptions were utt11:ed in establishing the new setpoints. These conservative assumptions include a lower flow rate than that considered in the UFSAR (720 versus 990 ppm). The enveloping line loss for the lower flow rate was utilized for both units to establish the worst case line losses. The setpoint ;
calculations included an instruw.ent uncertainty of 4.5" Hg calculated in accordance with Regulatory Guide 1.105.
The new recommended AF$pS setpoints calculated based on these assumptions aret ,
't Alarm : 17" Hg *
$witchover s 6.5" Hg Puep Trip : 3.0" Hg ;
When the new setpoints are incorporated, the condensate storage tank level required to assure that 200.000 gallons of water is available prior to switchover can be reevaluated. Based on the recomunended switchover setpoint, the Technical Specification ilmit for water level can remain at 423 feet (40%) for Byron. This calculation assumes line losses based on operating conditions anticipated at the time when the 200.000 gallons in the CST have been exhausted. Procedure revisions and Setpoint Scaling Change Requests will be submitted concurrently to install the final reconsnended AFSp$ setpoints. AIR 454-225-89-29600 will track :
this action. ,
Other safety significant instruments will be reviewed per Action item Record (AIR) 454-225-89-27600 to ,
verify head correction requirements. Review of progransnatic changes required to c16tify head correction instructions will be tracked by AIR 454-225-89-27700. An additional review of all Technical $pecification instruments is being completed to confirm that the Regulatory Guide 1.105 calculations adequately assess the system design. AIR 454-225-89-29000 wl11 track this action. Technical $pecification 3.3.2 (fable 3.3-4 Functional Unit #6g) will be revised to more accurately represent the new setpoint and allowable value for suction switchover. AIR 454-225-89-29700 will track this action. A UFSAR amendment will be requested for UFSAR Section 10.0.3.4 and will be tracked by AIR 454-225-89-29800.
F. ERLY1QV$_QCCURRENCE$1 i
There have been no previous siellar events.
(0457R/0059R)