ML20094M459
| ML20094M459 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 03/27/1992 |
| From: | William Cahill TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TXX-92143, NUDOCS 9203310290 | |
| Download: ML20094M459 (15) | |
Text
.
PT leg (i TXX-9?!43
~ ' " -
- file (! 10130 J lR 91-202,91-201 r.
r Ref. Il 10CfRP.201 lllELEC1RIC u maam J. c.hm, Jr.
ww n ranke U. S. Nuc lear Peyulatory Commission Atin: Documen' Control Desk Washington, DC 20$55 SUBJEC1: COMANCHC PEAK STEAM EL EClRIC STA110N (CPSES) - UN!!S 1 AND 2 DOCKEl NOS. 50-445 AND 50-446 NRC INSPECTION REPORT N05. 50-445/91-202:50-446/91-201 RESPONSE 10 DEF ICIENCY AND UNRESOLVED ITEMS Gentlemen:
TV Electric has reviewed the NRC's letter dated January 27, 1992, concerning the Configuration Management inspection (CMl) conducted by the NRC staf f f rom November 18 through December 13, 1991, This inspection covered dcliVities authorized by the NPC operating license NPf *87 and construction permit CPPR-127 The January ?7, 1992, letter requested that TU Electric respond to the Of f ice of Nuclear Reactor Regulation within 60 days regarding actions taken relatec to deficiency 50-445/91-202-01; 50-446/91-201-01 and both unresolved items identified within the report. The letter also expressed a concern about the number of examples of failure to verify or to check the adequacy of the design and requested that TV Electric review this matter and advise the NHC as to what, i' '9y, additional corrective actions are planned. The response to this con- and to the individual findings is addressed in tne enclosed attachment.
Sincerely,
/
L, William J Cahill, Jr.
RHS/tg Attachment c - Mr. R. D. Mart in Region IV Mr. l.. A. Vandell, Region IV Mr. B. A. Boger, NPR Pesident Inspectors, CPSES (2) 3J 00M. / \' i 9 03310290 920327 P. O. Dos l(02 Okn Rme Texas ?OO 1(02 PR ADOCK 05000445 O PDR
httachment to TXX-9P143 Page 1 of 14 pef icjynty 445/91-202-01 446/91-201-01 finding
Title:
failure to verify or check the adequacy of design.
OfA(fint_ ion of _ Congjlign:
The licensee's design-basis documents (DBDs) and supporting design calculations contained a number of f alse assumptions and erroneous calculations and computations. Some of these f indings are discussed below.
(See below for detailed description of findings.)
Requiremeni:
Criterion 111 of Appendix B to 10 CF R Part 50, requires that desigri control measures be established f or verif ying or checking the adequacy of design, and for assuring that applicable regulatory requirements and the design basis are correctly translated into applicable specif ications, drawings, procedures, and instructions.
Omrall R_cspgofe_i_g_4151LL02-0L_M0/31-101-01 BAL.karound:
The Project approach to resolve the deficiency included addressing each finding for cause, extent of condition, significance, actions to correct the finding, and actions to prer- 1e ;ecurrence. Secondly, the individual l f indings were reviewed collec. lvely to determine underlying causes to l~
develop preventive actions. .
l Although the findings variec by ditripline, type, and nature, an underlying trend existed throughout in that the findings, in most cases, could have been prevented had the preparers been more careful in developing the calculations and the reviewers or design verifiers been more thorough in their review of calculations and applicable design inputs.
, in addition to the actions taken in the past to enhance the quality of l calculatiens (including monitoring programs, technical training, training on l attention to detail, and responsibility of calculation preparers and I reviewers), the Project is instituting a training program which discusses
'the oesign verification provisions in N45.2.ll. This training. focuses on the purpose, methods, and importance of complete and thorough verification of design using actual examples to reenforce design concepts. CPSE5
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4 Attathment to 1XX-97143 Page 2 of 14 1
training began March 16, 1992, and inc ludes site engineers involved in calculat ion review, verif icat ion, and approval. In addition, the results of f uture 10 Electric QA audits and surveillances will be closely monitore'i by
- Unit 2 Engineering Assurance to evaluate the ef fectiveness of these and other actions being taken to enhance calculation quality.
In addition to training, a number of reviews and procedure changes have been 3 or will be performed for the individual findings. These actions are disc ussed below. Where correct ive actions are identif ied, the results of these activities will be available f or onsite review by the noted due dates.
80sponse m to 445/91:202 1 0 Land 446/&201-OLEimilng.JH ll RS.CL}RlloD_QLCQDdillDDI !
incorrect design temperature and pressure values were used in vendor-provided Class 1 piping analyses for the emergency core cooling system (ECCS). Westinghouse Calculation 10 2-0152 for pipe stress contained inconsistcht values for the design temperature and pressure in different sections of the calculation. Westinghouse had issued revised temperature and pressure values that had not been entered into the Unit 2 " ACCESS" data base until af ter portions of the -calculation had been completed. Vendor Calculatico 2-0157 used design temperatore and pressure values (2735 nsig and 3007) that dif fered f rom the correct values listed in the . licensee's "ACCE5S" data bdse (2485 psig and 650 f ) and provided by Wastinghouse in its letter WPT-12394. These revised values were also applicable to the equivalent Unit 1 syst ems. Therefore, Westinghcuse had failed to reconcile the latest available design ter*perature and pressure values in some of its Unit I final piping calculations. The licensee issued Operation Notification and Evaluation (ONE) Form FX-91-1660 to formally identify and resche this issue. Westinghouse subsequently identified an additional 14 Unit 1 piping calculations with problems that resulted f rom the revised design tamparature and pressure values. All 14 calculations were evaluated by the licensee and found to have sufficient margin to a:commodate the ,
revised values. The team concurr ed with the licensee's determination that suf f ic it nt margin to accommodate the revised va lue were present. :
Pe6 son for Finding; i
The following paragrapns sunmarize the reasons for the finding concerning Unit 1.
o Training of piping and support personnel to the Westinghouse program and-implementing procedures was esident. However, training to the specific project procedures f or design change control-was considered inadequate o Specif ic Westingnause CPSES Unit 1 procedures describing methods for pipirg analysis and the procedure describing final reconciliation referenced the Piping. Designation l ist (CPES-M-1017), but did not reference pcssible applicable Design Cnange Authorizations (OCAs).
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i Attachment to IXX-92143 $
Page 3 of 14 o On September 11, 1991, the CPSES Piping and Support Group was placed on controlled distribution f or the P1 ping Designation L ist (PDL),
Spec if icat ion CPE S-M-1017. Prior to that, the POL, (Revision 0) was referenced in specific CPSES procedures, and DCAs were transmitted to the Westinghouse Piping and Support Grnup f rom West inghouse projects. l Revisions to the PDL and DCAs were retened and filed with the revised l list. The users of the list were required to review each DCA to ensure the inf ormat ion (input ) was current. However, this process involved ;
numerous DC As and their cont (nt was scnet Wee detailed. Consequently this process was cumbersev.
o lhe it mperature and pressure t.hanges made by the WestinghDuse fluid System group to the line list were transmitted to CPSES using the correspondence procedure, lhese chenges were incorporated into CPES-N-1017 by the DCA process. The DCAs were transmitted to f Westinghouse projects, and projects forwarded the documents to the Westinghouse Piping and Support group. However, DCAs pertaining to the fourteen (14) piping analysis problems were not incorporated into the ,
original analysis, ifLLaf_Lt2 Action:
Unit 1 Line List Reconciliation ONE form, FX-91-1660 was issued, to identif y and resolve this finding. A sunmary of the actians associated with the Unit 1 Class 1 piping calculations is discussed below, i
o Westinghouse reviewed CPES-M-1017, Revision 4, for the Westinghouse ,
Unit 1 suope Class I lines to identify differences between specification and analysis design pressures and temperatures. The review was performed on a stress problem basis. Fourteen (14) piping analysis problems were impacted by temperatures and pressures changes.
The design calculations have been revised to reflect the correct design pressures and temperatures. The revised calculations do not ref lect any signif icant increase in pipe stress, and the design loading requirements are still met, A review of other correspondence including WPT-12394, -8946 and MED-AEE-6911 was also completed. Inconsistencies were identified but were determined by Westinghouse Fluid Systems to be insignificant, ,
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'At tachment to IXX-92143 Page 4 of 14 o A review will be conducted to compare CPES-M-1017, the Westinghouse line list, ACCESS, and the equipment fuhctional design requirements, with respect to temperatures and pressures to ensure that these dacuments are in agreement, lhis review will be completed by May 31, 1992.
I o Unit 1 Westinghouse internal procedures governing the appropriate source and use of design temperatures and pressure have been revised to l 4 reflect that CPES-M-1017, Revision 4 with DCAs is the source of the Unit 1 design temperatures end pressures. The procedure tables were i corrected to be consistent with CPES-M-1017 Rev. 4. l 2 Pesolution of Unit 2 L ine t ist -Discrepancies ;
Westinghouse did not use the correct design pressures and temperatures in '
some of the Unit ? piping analysrs because ACCESS was being validated when the analysis was being made. The database has subsrauently been validated.
Westinghouse will use ACCESS to define the appropriate design temperatures i
. and pressures. The intent was always for Westinghouse to use ACCESS; however, it was not employed because the needed information had not yet been incorporated into the database at the time the design analyses were performed. The As-Built Reconciliation program wil1 provide f or a single verified source of' design inputs and the means to identify and reconcile discrepancies related to the subject design inputs.
Piping and support specification and Design Basis Document Review
[
Programs and procedures for Unit ? are in place between CPSES and Westinghouse for processing, oistribut ing and incorporating design changes.
Design changes, initiated by Westinghouse, are documented and controlled in accordance with the-CPSES program. These design change documents are being transmitted to af fected groups on a controlled distribution list. These same design change documents, along with the design document, are controlled by ACCESS. Westinghouse personnel performing work for-CPSES have access to the database.
To ensure other errors related to DCAs were not made, the following Specifications and Design Basis Documents (DBDs) were reviewed and were all related to the piping analysis, o floor Response Spectra, Rev. O,
! o- - Pipeline Designation List, Rev. O to Rev. 4 o Reflection Insulation, Rcy. 2, o Valve Weight List, Rev. O o Design Basis Document, Building and Secondary Wall Displacements, Rev.-2 o- Piping and Equipment Insulation - Non-Nuclear Saf ety Related, Rev.1
- 0. penetration Seal Schedule No additional findings that may have af fected the integrity of CPSES piping-L - analysis were found.
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Attachment to TXX-92143 Page 5 of 14 training DCA training had twen S;ven, Out not documented, during the Westinghouse ,
unit 1 piping ana'ysis efrort. Since the error occurred, the importance of adequately reviewing DCAs has been re-emphasited in the Unit 2 Westinghouse l Piping and Suppurt Group bi-weekly meetings. In these meetings the ,
engineers are made awcre of changes that are occurring in the specifications and design documents that are important to the analysts and designers.
Onsite Westinghouse personnel have received training to ensure that the Equipment Qualification and Testing group (EQLT) is provided with DCAs and :
IDES (corrective action documents) that affect Westinghouse supplied-equipment. _1 raining has been provided to personnel in the fluid System >
group working on the Comanche Peak Project. This training included a i discussion of the controls used for system parameter changes transmitted _to i CPSES, that system parameters be compatible with the Westinghouse f unctional
- Requirements Document, and notif icat ion of any system parameter change to the applicable unit (s).
Resnonie 140L & Roh o h E 6/ & 20 hol.ljndin9 32 :
ksctJunottoLCondiMon; F The Class IE- 125 Vdc short circuit calculations and associated protective device coordination f ailed to consider the contribution of the battery charger which resulted in a lack of coordinatton and the replacement of 125 Voc distribution panel protectivc fuses. lhe short circuit and protective device coordination calculations for Units -1 and 2 failed to consider short- 1 circuit test data of. the battery vendor to determine _ internal cell resistances and voltages, The calculation incorrectly used a Thevenin-equivalent representation based on the 140 Vdc equalizing charge voltage, which resulted in using an unrealistically high internal battery cell resistance in the calculation, in addition, the short-circuit current i
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contribution for the battery charger was intorrectly assumed.to be limited to 375 A by internal electronic control during the initial f ault current surge. However, because the battery charger ontrol elements are silicon-controlled rectiflers, current limiting control would not be effective until the first zero crossing of the ac supply current waveform is reached. This i might take more than half a Cycle _ depending on the ac supply Circuit time l
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constant (X/R ratio). There was a concern that the small-f rame molded-case f eeder circuit breakers and feeder protect ion fuses would attempt to ,
interrupt bolted f aul_t currents in a-comparable time lapse. Thus, the higher initial battery charger short-circuit contribution, combined with the battery contribution, could result in excessively high short circuit duty and/or loss of coordination between protective devices. The licensee implemented timely actions to avoid affecting Unit I restart. The licensee prepared new short-circuit and protective device coordinat ion calculations and replaced the 200 A' distribution panelboard supply circuit fuses with a type having slower blowing cnaracteristics in the high-current region. The new short-circuit calculat ion correct ly used the vendor's short-circuit test l _ _ _ _ _ _ _ _ _
At tat hment to 1W 92143 Page 6 of 14 uata together with the applicable triteria of AN $1 C 3 7,14 '19 79 to determine the batterj tel1 intrrna1 rt sistom e lhe t cam t ont urred nit h t he licensee actions.
St3Rn 1pr f ifid Ing:
lhe preparer anJ reviener f olle.a u the guidelines in ILLL-946-19Bb Sect ion 7.9/ t or ca lculat ing the short c irc uit contr ibut ion f rom t he battery
( har gers . Actording io lLfl~-946-19R5. the manimum short tircuit current that a charger will deliver will 1,pically not exceed 150X of the charger amp ( t e rat ing. However, the preparer and reviev,er did not rec ognite that the battery charger current limit inq f eature does not start until after the short ( ircuit (urrent wave c rosws t he first toro into the v avef orm.
'he DC tatt(r, short ( it ( uit ourront r a ll u lat icn used Thevenin's model of the tatte y source usinq 140V CC caualizing voltage because it was assumed te be a Nre conservat ne voltage Honever, it was not recognized that this madel would result in higher interna l bat tery resistante Olrrii',iee I Q ipnj:
The following DC short circuit and coordinat ion C alculat ions were revised to ref lect the correct short circuit currents based on the manuf acturer's data and industry standard ANSI L37.14-1979.
o Short Circuit Study for Cl ss Il IPbvDC System-Unit 1 Pev, 2 o Short Circuit Study f or Llass il 125 VDC $ ster.s 3 Unit T 125 VDC tourdination lhe PDOA distribution panel board supply c irc uit f uses were replaced with slow-blow type f uses to accomplish coordination. Add it iona lly , DBD-((-044, "DC System" will be revised to incorporate the criteria f'or calculat ing the DC short circuit currents f rom t atteries based on 125VDC potent ial, the manufacturer's supplied internal resistance, and AN51 5td. C37.14-1979 for battery charger fault current (entribution. Ibis attinn will be completed by August 30,199?,
lois f inding could be abplicah h> to any equipment that has a current limit ing f eature, suc h as buttery charger and inverters, lhis equipment has been evaluated f or FDth Units acd any similar errors have been determined to hdve no iFpdct on the esisting design.
' Attachment to TXX-92143 .
Page 7 of 14 i
Renom e_tL4.45M L-202-0k440lRzoh 0 L Lt od ing JI3 NKt pt.10tLQLC00ditj9M i
Analyses to ensure that electrical components or cables met the design basis !
requirements of DB0s CE-03. 05P and 10 CTR 50,49,d had not been performed, ;
The calculation or analysis that demonstrated that the voltage drop margin ;
was adequate for equipment required to mitigate a main steam line break (M$LB) outside containment, The licensee stated that no documentation existed to demonstrate that there was adequate voltage margin. Licensee engineering staff performed a preliminary analysis that the resistance of t the cable had increased by 30 percent, which suggested the safety margin had changed. The preliminary analysis and supporting documentation revealed I that components met the containment pressure transmitter equipment qualifications and the voltage loop criteria for the transmitters to operate properly under accident conditions, lhe licensee agreed to f ormalire the calculdtional results, lhe team determined that the licensee actions were ;
appropriate.
- Renon for finding!
- 1he preparer and reviewer believed the differences were negligible and therefore, did not address the irrpact of the higher ambient temperature on the resistance of the cable lengths routed in areas of postulated Main Steam Line Break (MSLB), Since the duration of this temperature is high enough to increase the cable resistance by approximately 24 % (for power cables .
based on 90*C) to 30 % (f or irstrument and control cables - based on 75"C) f rom its non-accident value, a potential for not having adequate voltage at >
- the safety devices existed. !
Comnlyeltt lon: ,
Safety-related equipment in rooms subject to an MSLB temperature of 334T
- outside containment was evaluated. The power equipment-in these rooms that-operate during an M5LB consis M '
sixteen motor operated valves.
Calculations show thal even at , higher temperature of 334T, a margin of more than 100% is:avallable beten the calculated and acceptable cable ;
lengths.
Also.. safety-related equipment inside containment subject to an tiSLfi tem;)erature of 346'f was evaluated, Eighteen containment isolation valves are_ required to operate upon receipt of a saf ety injection signal.within the first 60 seconds. The margin between the actual length and the acceptable cable length for the valves was found to range from 3B0% to 1700% based on the_ minimum bus voltage of 428 volts (i.e., during the largest motor - -
starting and a minimum MOV starting voltage of 368 volts),
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4 Attathment to 1 W 9P143 Page 8 of 14 i
Additionally, four other in-containment MOVs provide isolation between the
, high and low pressure piping of the Reactor Coolant System and Residual Heat Renoval (RHR) system. These MOVs are normally closed and remain closed under M5LB conditions. If required to operate under any accident scenario, l (cincident with the start of the largest motors and minimum system voltage ;
conditions, the voltage at the MDV terminals could be less than 80X or 368V I (ca h ulat ion 2-E L-0008 Rev. 3). This condition was determined to last for !
no more than 0.5 setunds, wh nh is the max imum rec overy t ime of the voltage .
when starting the largest load off a diesel generator (Diesel Generator lest i Report CPI-MEOGLE-01). During the 0.5 seconds, either the contactor of the !
MOV will not pickup or the motor will stall until adequate voltage is I available at its terminal. The maximum stroke time of these MOVs is 120 i seconds. A delay of 0,5 seconds, for completely closing or opening these ;
valves, would have a negligible af f ect on the safety function of these ,
va lves. i i
ihe electrical loads in the High [nergy Line break (HlLB) areas were also eva lua t ed. Ca lculation P-El20008 Fev. 3 indicateo that a minimum of 500% .
margin e3 ists between the pernissible and the design cable lengths. ;
theref ore, the impact of higher design resistance due to the HELB j temperatures on the available voltage at the loads can be neglected.
for Class 10 control and ins;rumentation circuits, the following Unit P calculations were revised to address the ef fect of the higher ambient temperature of 3347. Although the bounding ambient temperature due to an '
MSLB is 345T inside containment, the conductor temperature will not exceed 334'T. The same temperatures can t4e applied to the f ollowing in-containment devices; IPS VOC Control Circuits MCC (120 VAC) Lontrol Circuits Miscellaneous 120 VAL Control Circuits in calculating' the minimum voltages available at the device,15'C cable ;
resistances were multiplied by a f actor of 1.3 to account f or the higher '
M5LB temperature. The new miniinum required voltages were compared against the available voltages f or acceptability. The minimum required voltages were below the available voltages and were, therefore, acceptable. Changer to the above Unit 2 calculations are underway to evaluate the impact of i Unit 1/ Unit 2 interf ace catiles. These attions will be completed by August 30, 1992. Similar changes will be ref lected on Unit I calculations by September 30, 1992. DBD-LL-ObP will be revised to require the temperature eff ect on cable resistance under DBA condit ions be considered ;
when Calcolatirq the minimum voltage at the equipment. This action will be completed by September 1,199?.
l l The Cp$f 5 design engineering ' group has- been advised-of the requirement to L use.the appropriate temperature when calculating the voltage drop due to the length of cable which is routed in an MSLB or LOCA environment.
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' Attachment to 1XX-92143 Page 9 of 14 B espostto_M 5/31-207- Oh_440M1 -?0L-01lincU ngl 4 DestrJountoL0onditiont
- An incorrec t service water temperature was used in a vendor perforrbed RHR Cooldown analysis. Westinghouse Calculat ion FR55/SS-TEX-1076, " Comanche Peat 1 & ? 1 rain Cooldaan limes,' assumed a constant service water temperdture of 10?~f over the P4 to 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> of the cooldown, rather than assuming an increasing terrperature in response to heat rejection to the heatsink. However, technical specifications (15) required the units to be in a cold shutdown condition within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> if the maximum service water temperature was exceeded. The licensee performed Calculation I FSE/SS-TEX-1678. Revision 0, which assumed a worst-case scenario of one unit experiencing a design basis loss-of -coolant accident (LOCA) and the other unit being shut down. The licensee predicted the temperature increase on the basis of lable 4 4.of the study of J. E, Edinger Associates, Ir$c.,
entitled, " Hydrothermal Simulations of Comanche Peak Safe Shutdown Impoundment." The licensee performed a new analysis that showed that two-train cooldown of the non.ircident unit could be achieved. lne team reviewed the _ new calculat ion and agrees with the licensee's conclusion.
Reason for The f irtdjng: J l
The finding occurred because of inadequate communications between ;
organizations concerning details regarding the time dependence of the Safe Shutdown impoundment (SSI) temperature, tn a.,dition, an erroneous constant 551 temperature value was assumed, ;
[EEtEljXt_.0LLi&O:
In addition to the new analysis noted in the finding, Engineering will ;
determine the $51 temperature as a f unction of time.' A dual unit normal cooldown, which maximizes the f. eat rejected to the 551, will be assumed, i Westinghouse will de' ermine via formal calculation the cooldown capability
of the RHR system using the above results. The calculation will be addeo to DBD-ME-260. These actions will be completed by April 30, 19)?. The RHR Design Basis Document and TSAR will be reviewed f or potential impact. t Changes to these documerts will be made, as necessary, by April 30, 199?. !
l Project personnel will be instructed to review requests for informatinn from ;
l_ .Other contractors for completeness and to communicate with the contractor any perceive 1 incompleteness as well as to request complete boundary condition.information,_when necessary. It will be emphasi7ed that I assumptions regarding critica l analysis parameters cannot be made. This action will be accomplished through the quality accountability process.
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4 Attachment to 1XX-92143 Page 10 of 14 Res pons e_.19343131-201-01. 146/3 b?01-O LID:md5 l
. UcKdpilottoLCqudtLlont During the design review, the team found eight calculations that contained nonconservative assumptions, inconsistent information with other calculations, incomplete information, or errot s. Although these calculation deficiencies were not saf ety significant, reanalysis was required in several i instances to confirm design adequacy. In the case of the residual heat l removal (RHR) cooldown analyses and the diesel generator intake temperature ;
stress analyses, previous design margins were reduced.
Ernon f tr Finding:
Each identified discrepancy, responsible organization, and individual was :
different. However, the common trend was that each error, although not ;
impacting the calculation results, could have been prevented through a more detail (d preparation and rigorous review and verification process. Although ,
similar minor errors may exist in other mechanical calculations, f urther review is not warranted, based on the type and nature of the findings.
C.OryecLin,At11gg l As a r*sult of the findings f rom the NRL and those by QA via an audit, the Unit 2 mechanical engineering discipline reevaluated the group of personnel performir.g calculation reviews and limited the group based on experience and performance, lhis group received refresher training on review requirements.
No additional mechanical calculaticos were issued until the reviewers had been-trained. Additional training was conducted on the responsibilities of ;
calculat ,on preparers and reviewers. l As described in the NRC Int.pection Report, ident if ied discrepancies have or ,
will be corrected by April 1, 199P. Addit ionalij, one set of cair.ulations. [
f or f ire protection sprink .ers, was ident ifled thrna4h a.10 f.lcrtr1r QA >
audit as having 6n unacceptable level of accuraty r elative to piping ,
takeoffs. The completed sprinkler calculations were ccerected.
L Responie_lo M#9L-2.0h01.340/91-RQEDLLtndingJ6 L
DeicdpLica .nf_Condli.ioni The team also found en error in the Calculation ikE-f E-CA-0008-267, _.
- Revision 1 of the backup protective relay (device 51 V) settings for the l EDGs. The tcmputation of the 6.9 kV bus short' circuit voltage _ level (Vb) l incorrectly useG the 2000 kVA transformer per unit impedance
- instead of the EDG impedance. Inis error resulted in improper application of device 51 V characteristics in the associated coordination curves shown in the 4
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Page l! of 14 .
- calculation. Dur mg iso'ated emergency operation, the [0G proter.t ive devices were bypassed with the enception of dif f erential and overspeed '
protection. Honever, the EDG needed adequate protection to support i su/veillant:e tc5 ting while in parallel with the preferred power sources, in response, the licensee performed a supplonentary calculation that showed i that in this scenario the fault current contribution of the system would :
result ir5 short er f au lt clearing t ime. The shcrter f ault ex.posure would not j excoed the (06 therre.1 limits, thus, resulting in atteptable prottction. The !
licensee egreed to correct the ulculation, lhe team agreed with the !
1itensee's act ions and f atu, e r Derer t ion *., l PdakW1.12f.1.1011irg l The finding is attricuted to inaccatdte attent ion ',o detail on the part of the calculation preparer, rav )euer. and approver.
CfIreg,1v(d3jf;g:
Calculat ion IN[-[f-CA-000b267 will be revised to torrect the 6.9KV bus voltage temputat ion, and tne correct characteristic turve for relay SIV will i be ut illtf d in caltulat ions ifd -( t L A-000ii-P67 and T NL-f E-C/r 0008-157 This attion will be completed by August 30, 199?.
I in addition to the . raining planned f or design verif ication, engineers who i prepare, review, and approve Elec9 ital Engineering calculations have been i advited to pay more attention te details, i i
B n pon s tLt o.JH/91 -702-01.3%/9 h 20 h0111nd inq E pescrJRtlon_9f_Jondit iont ;
The licensee's se%mic support ca kulat ion ([hasco Calculat ion No. Vol IV . Book $2) for the battery room explosion proof heater used an intcrrect. heater asstebly we Ojht , The licensee used a Weight of 900 pounds f or the seismic suopert of the henter assembly in the computer analysis I rather than the weight of 1160 pounds as indicated in vendor Drawing 66L.
No justification f or the use of the 900-pound weight was noted in the calculation. The licensee generated a ONE form fX-91-1661 to adaress the issue for both units and to correct the calculation. There was sufficient ;
margin in the cdiculation to accomTdate the increased weight and this type '
of heater was ont used elsewhere in either unit. The team reviewed the license e action and egreed tnat Suf fi.: lent margin in the calculation was present. ,
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- Attachment to IXA-92143 l-Page !? of 14 l 1
EGWn f on,[(n11ng:
Review of the finding following the NRC inspection revealed that during the copying process of the calculation, a second book in the calculation package ;
was inadvertent ly omitted. This was not readily apparent to the liVAC :
engineer during review of the calculation. When the calculation was
- requested f or revisien and the calculation package provided (including the sewnd book) it was found that the original calculation had considered the j appropriate weight of the heater and the (ondition was not a deficiency. !
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W H O h t_! n ien:
Calculation Change Notice (CCN) Number 1 was issued to clarif y the ,
calculMion table of contents to preclude recurrence of this situation.
BR5 por1Rtitfj! /Eh202 .0L _%/9h201.0 LfJ nd199 J!8 l DescrJpliotoLCondidoni >
I Another potentially adverse effect of the high primary transformer protective device setting was the extended (approximately 4.5 seconds) EDG exposure to a fault in the transformJr secondary terminals. Such a fault could result in EDG loss' of excitation due to low output voltage
.(approximately 60%) with attendant loss of the 6.9 kV bus. Ine team considered this an unanalyzed condition Of the Class 1[ emergency power supplies of the generating station, requiring resolution in support of ,
continued plant operations. The licensee consulted w!th the EDG exciter vendor who stated that the excitation systen would not collapse under the extended low voltage exposure caused by_the postulated fault condition.
This was attributed to the EDG time constant of five seconds and the vector summing design of the excitation system, The licensee then determined that adequate design margin was present. The team agreed with thef? ,
determination.
Relig Fer .[1.nting:
The unanalyzed condition in the calculation is attributed to the preparer's and reviewer's inadequate attention to details.
Corrective Action:
Ca lculat ion - TNE-EE-CA-0008-?67 will be revised to address the effect of the-power center transformer overcurrent relay setting on EDG perf ormance/ availability by August 30,199?.
. Addit ionally, preparers, reviewers, and approvers, work ing on calculations have been advised to pay more attention to details in regard to the protective cevice settings and their potential ef f ects on the overall
- Electrical System protection.
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i Attachment to 1XX 92143 ;
Page 13 of 14 i Unte s o.1 yedJ t em A45/91 dO2-01. . A40/k 201 -01 j ReitrJm is;LJ1nAiLipa: :
I F SAf: Section 3,1.1.5 contained a commitment by the licensee to ccmply with i 10 CFR 50 General Design Criteria 5. _ Structures, systems, and com;ionents i important to safety shall not be shared among nuclear power units unless it ;
can be shewn that such sharing will not significant ly impair their stpility to perform their taf ety f unctions, including, in the event of an accident in ;
or4e unit, an orderly-shutdown and couldown of the remaining units. The team l requested documentation from the licensee to show compliance with GDC 5, !
lhe licensee's evaluation of GDC 5 compliance was -in the process at the time ,
of ihe' inspection, with r.o firm toripletion date established. However.-the !
automatic transfer system for the six 480 V MCCs shared tietween Units 1 and -!
2 (i.e., XEul-1 f. 2, Xf BP 1 & 2, XED3-2 and XEB4-2) were energized and. !
available for connection to Unit 2. ,
The team reviewed the automatit transfer scheme and f ound that there was no l provision to prevent an automatic transf er of a f aulted 480 V MCC from ;
occurring upon loss of the preferred power supply due to a fault on the . '
affetted shared 480_V MCC. The lack of interlocks to prevent the ' automatic transf er of a f aulted 480 V MCC f rom Unit l_ to Unit 7, or vice versa, could poten',ially impact the operation of other safety equipment.
The licensee stated tne f ault would only arf ect one safety train ( A or B)
?
and that the other trahi would be available to perform the required safety i functions, lhe team remained concerned that the design allowed the >
i automatic transfer of a faulted MCC from one unit to the other without a full evaluation having been performed by the licensee to address the '
- potentia 1Torisequences. The licensee agreed to further review
- the automatic '
' ;ransfer-scheme to determine whether it it satisfactory or if design modifitations are required.
Remonic_1(L4AS/MdC2:01.346/91 dol:q1 l Compliance to GDC 5 has been addressed in DDD EE-057, Rev. 8, Attachment 20, entit led "Separat ion .E vcluation Re port ," Sections.l.3,-4.0, 5.1.2 and 5.4 -
of the 000 describe general cummitments and the program methodology for Unit 1/ Unit 2 interfaces through shared systems, while Section 3.14 ,
identifies requirements for shared circuits.
As discussed with the inspection team- analysis of the shared mechanical system is scheduled to_be completed as part of the Unit ? overall program for shared systems. A modification which would prevent the automatic transfer of a f aulted 480V common MCC f rom Unit I and Unit 2, or vice versa, is being evaluated for imp ~ mentation prior to Unit 2 fuel load. -i l
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Page 14 of 14 l t
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1he licensee's Class lE 125 VDC short circuit calculations indicated that. ;
under fault conditions with initial current surges in excess of 5600 i amperes.- a potential f or damage to the bat tery chargers esisted. IEEE ;
standard ?/9-1971 states that clau IE systems should be protected. This L item requires f urther evaluation by the licensee and the battery charger vendor.
Res ports tLt(L3 H/9 b202:02. _ A W91 - 70h 02 Battery chargrr vendor. Power Conversion Products (PCP), conducted a test at its f acility on a battery charger model which is the same as.the type used l at CPSES. ihe Vendor has provided the resuits of that test to CPSES and has ;
confirmed that the f usos provided to protect the Silicon Controlled Rectifiers (SCRs) ble( alnost instantaneously upon a dead short on the DC
- side of the battery charger. PCP battery charger test report ,
1U P.O. #C0000163-701 indicated that there was no damage to the SCRs af ter !
the test. .
i Dead short circuits on buses of electrical equipment manuf actured and tested in accordance with proven industry standdrds qualif ied to lLfE qualif ir6 tion and seismic requirements and operated in a controlled mild '
environment, are less likely to occur. However, if postulated, the fault would be cleared by the protective f uses as demonstrated by the vendor's test. The resulting temporary loss and isolation of the charger meets the ;
intent of 10,I-?79 and 308 because; of the following features provided in the
- CPSES design:
- 1. The loss of AC input to the battery charger is alarmed in the control room,
?, A readily tonnectable backup battery charger is provided for each !
safety train, ;
t it. is therefore. concluded that the Class lE DC Power Supply System supported by dual battery (hargers provides a reliable power supply source ands is
-adequately proteci,ed-and monitored against postulated faults in the system.
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