IR 05000458/1990200

Electrical Distribution Sys Functional Insp Rept 50-458/90-200 on 900521-0622.No Violations Noted.Major Areas Inspected:Design & Implementation of Plant Electrical Distribution Sys & Adequacy of Engineering Support

ML20058L546
Person / Time
Site:	River Bend
Issue date:	07/26/1990
From:	Gautam A, Konklin J, Lanning W Office of Nuclear Reactor Regulation
To:
Shared Package
ML20058L543	List: IR 05000458/1990200 ML20058L536
References
50-458-90-200, NUDOCS 9008070282
Download: ML20058L546 (28)

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U.S. NUCLEAk REGULATORY COMMISSION 0FFICC 0F NUCLEAR REACTOR REGULATION l

NRC Inspection Report 50-458/90-200 Licensee No.: NFF-47 l

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Docket: 50-458

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Licensee: Gulf States Utilities facility Nase: River Bend S.ation Inspction at: River Bend Station, St. Francisv111a, Louisiana 70775 Inspection Conducted: May 21 through June 22, 1990

• . Ir.spection Team: A. S. Gautam, Team Leader, NRR 0. P. Chopra, Electrical Engineer, NRR T. O. McKernon, Reactor Inspector, Region lY R. B. Vickrey, Reactor Inspector, Region !Y NRC Consultants: H. Leung, AECL (Atomic Energy Canada Ltd)

5. Inamcar, AECL T. J. Delgaizo, AECL 0. S. Mazzoni, AECL Approvea by: ____

-Art- M##h0 pnn s. sono, Team teader osse Team Inspection Section A Sp6cial Inspection Branch .

Division of Reactor Inspection and Safeguaros Office of Nuclear Reactor Regulation Approved by: _ MBSAB gdes E. Konklin, Chief Date

/1easiInspectionSectionA Special Insp ction Branch Division cf Reactor Inspection anc Safeguards Office of Nucle Reactor Regulation l .

Approved by: <

26 O y ie . tenning, chief Dge i Speci 1 Inspection Branch Divistori of Reactor Inspec' on nd Safeguards Office of Nuclear Reactor Reg ation 9008070282 900801 8 ADOCK 0500

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EXECUTIVE SupMARY A Nuclear Regulatory Commission (NRC) team conducted an electrical distribution system functional inspection (EDSFI) at the River Bend Station. The inspection was conducted by the Special Inspection Branch of the Office of Nuclear Reactor Regulation (NRR) from May 21 through June 22, 199 The NRC inspection team reviewed the design and implementation of the plant electrical distribution system (EDS) and the adequacy of associated engineering and technical support. To accomplish this, the team reviewed the design of electrical and mechanical systems and equipment affecting the EDS, examined installed EDS equipment, reviewed test programs and procedures affecting the EDS, and determined the adequacy and interfaces of technical disciplines and functions by interviewing appropriate corporate and site personne The team considered the design and implementation of the EDS at River Bend to

, be generally acceptable. The design attributes of the EDS were retrievable and

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verifiable, in most cases, engineering calculations had conservative assump-tions and conclusions and were technically sound. The scope of the site test program for EDS equipment was appropriate. Engineering control of modifica-tions to the EDS appeared to be effective and there appeared to be proper interfacing between engineering disciplines and functions. EDS equipment was properly installed in the plant and had adequate traceability to design docu-ments. Few deficiency tags were observed and the equipment appeared to be well maintained. Engineering and technical support for the EDS appeared to be adequate. Although the team found a significant backlog of modification requests, condition reports, and unincorporated drawing changes, the licensee was addressing the backlog through specific task force recommendations and appropriate planned action The team also considered the engineering and technical support for the mechanical systems inspected to be a licensee strength, in that the associated technical staff was knowledgeable, and a significant amount of information was available, through calculations and system testing, to assess the mechanical system The team had several findings regarding inadequate design reviews for certain conditions of operations and postulated failures of certain EDS equipmen Protection and coordination studies for the 120 volt ac and 125 volt de control circuits had not been performed. The licensee prepared an analysis to demonstrate that these circuits were operable based on sufficient independenct and redundancy of these circuits to perform their safety functions, assuming a single failur Capacities of EDGs 1 and 2 to sustain loads, if loads were sequenced at various times within the setpoint band, and the capacity of the EDGs to sustain postulated accident transient loads had not been analyzed. Protection of load center 4160/480 volt transformers for power surges had not been analyzed. The possible loss of the Divisic.,3 bus due to incorrect annunciation by the high resistance ground scheme on the 4160 volt safety system had not been evaluate A stress analysis for potential damage to mechanical piping duris; the possible simultaneous starting of both standby service water pumps had not been per-formed. The sizing of the EDG grounding resistors with regard to current and thermal considerations was not analyze i

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The team found that postulated failurvs of the hiph-pressure cooling systes l (HPCS) pump motors and stanoby service water (SSWs pues setors that could  !

result from high transient currents generated during tie fast transfer of the l M vision 3 bus to offsite power had not been analyzed. DJe licensee had ,

semporarily suspended the fast transfer scheme before this inspection because l of other problems, and was currently feeding the Division 3 bus from the of fsite grid rather than f rom the rein generator. Because of the team's concerns, the licensee decided to continue using the temporary operating procedure while performing studies to evaluate the possible failures of the -

HFCS and $5W pump motor '

Examples of other unanalyzed conditions of operation were identified, including the potsntial for the battery electrolyte temperature falling below assumed values; capability of equipment to sust61n the short circuit contribution from an energency diesel generator (EDG) when tested in parallel with the unit generator or the offsite grid; effect of the air start lockout feature on the

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,. autoratic starting of the diesel at low air receiver pressure setpoint; and ,

the adecuacy of the low differential pressure setpoint for initiating the SSW

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l pumps under certain nor:41 service water flow conditions.

l Ir. addition, the USAR incorrectly stated the initiating signals for the .

I starting of the SSW pumps; the EDG loading calculations did not take into account the magnetizing inrush current for the load center transformers; and the calculations for raximum piping tunnel temperatures and other temperatures applied an incne set rethocology. Examples of unsubstantiated assumptions, missing references, and missing reviews of design calculations were also foun The team noted that the engineering and technical support staff had not per-formed a critical review of the calculations p6rforsed by the architect-engineer, and that many of the missing calculations and other deficiencies would have been identified by such a review. The licensee comitted to perform appropriate analysis and to revise calculations by March 1991.

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TABLE OF CONTENTS i

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PAGE EXECUT!YE SUMMARY ....................................................... 7

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1.0 INTRODUCTION ........................................................ 1 2.0 E L E C T R I C AL S Y ST D.S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.1 C la s s 1 E 4160 Vo l t AC Sy s tem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.1 C l a s s 1 E 480 Vo l t Sy s tem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Class 1E 125 Volt DC and 125 Volt AC Systesi .................... 6 2.4 Conclusions .................................................... 7 .

3.0 MECHANICAL SYSTEMS .................................................. 7

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3.1 Trip Signal for Stanoby Service Water Systeni ..............-.... 7 l' 3.2 EDG Ai r St a rt L oc k Ou t F ea tu re . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 l 3.3 Maximum Temperature in Piping Tunnels .......................... 8 L 3.4 B a t t e ry Room Tes1pe ra tu re . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.5 USAR Inconsistency on Service Water Pumps ......................

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3.6 Una na ly z ed P i pi n g S tres s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.7 Conclusions .................................................... 9

, 4.0 EDS EQUIPMENT ....................................................... 9 Equipment Walkdowns ............................................ 9 Equipment Modifications ........................................ 10

' Equipaent Testing and Calibration .............................. 10 Conclusions .................,.................................. 11 5.0 ENGINEERING AND TECHNICAL SUPPORT ................................... 11 5.1 Organization and Key Staff ..................................... 12 l 5.2 Root Cause Anslysis and Corrective Actions ..................... 12 l 5.3 Engincering Involvanent in Operations .......................... 12 5.4 Self Assessment and Training ................................... 12

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5.5 Conclusions .................................................... 13 6.0 GENERAL CONCLUSIONS ................................................. 13 ,

Appendix A - Findings ............... .................................... A-1 Appendix B - Personnel Contacted ......................................... B-1

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. 1.0 INikODUCTIDN

. Before this inspection the Nuclear Regulatory Cosmission (NRC's staff had ,

l identified several electrical distribution system (EDS) def tr,iencias during electrical inspections at various operating plants in the ccantry. The Special Inspection Branch initiated inspections of the EDS at operaf.ing nuclear plants

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after it determined that such eeficiencies could affect the EDS power sources '

I ar.d equipment, and could compromise the design safety margins of nuclear plants.

l Examples cf these deficiencies thcluded unmonitored and uncontrolled load l growth on safety buses, inacequate engineering socifications, design calcula-tions, testing of EDS equipnent and qualification of cossnercial-grade equip-mentusedinsafety-relatedapp$1 cations. The NRC considered one cause of these oeficier.cies to be inadequate engineering and technical suppor The cbjectives of this inspection were to assess the performance capability of

, the River Bend EDS and the capability and performance of the licensee's engi-neering and technical support in this area. For the purpose of this inspec-

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tion, the EDS included all emergency sources of power and anscciated equipment i

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provicing quality power to systems relied on to remain functional during and following design basis events. The EDS cosiponents included the emergency

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diesel generators; 125-V de Class 1E batteries; two offsite circuits from the 230-kV of f site power grid switchyard; distribution transforsers; 4160-V switchgear; 480-V ac load centers; 480 Y ac,120-V ac, and 125-V dc motor control centers; and battery chargers, inverters, associated buses, breakers, relays and device The team reviewed the adequacy of emergency onsite and offsite power sources for EDS equipment, the regulation of powcr to essential loads, protection for postulated fault currents, and coordination of the current interrupting capa-bility of protective devices. The team reviewed mechanical systems affecting the EDS, including air start, lube oil, and cooling systems for the energency diesel generator as well as cooling and heating systems for EDS equipment. The team physically examined originally installed hDS equipeent and modifications for configuration and ratings and reviewed qualification testing and calibra-tion records. The team also assessed the capability and performance of the j licensee's engineering technical support functions with regard to organization

, and key staf f, timely and adequate root-cause analysis for f ailures and recur-

! ring problenis, and engineering involvesent in design and operation TheteamverifiedconformancewithGeneralDesignCriteria(GDC)17and18and appropriate criteria of Appencix B to 10 CFR Part 50. The team reviewed plant technical specifications, the updated safety analysis report, and appropriate safety evaluation reports to verify that technical requirements and licensee comitments were being se The areas reviewed and the safety significance of identifico ceficiencies are described in Sections 2, 3, 4, and 5 of this report. Conclusions are provided at the end of each of these sections. A summary of the conclusions and weak-nesses is given in Section 6 of this report. Each finding addressed in the report is considered an open or unresolved item and provided in Appendix A with a corresponding number and a reference to the section of this report in which it is discussed. A list of personnel contacted is provided in Appendix B and persons attending the' exit reeting are indicated with an asterisi before their name .__.__ __ ___ _ _ _ _ . . . _ _ - . _ _ _ _ . _ _ . _ _ _ _ . _

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2.0 ELECTRICAL SYSTEMS The team reviewed a sample of specific electrical design attributes at each ac and de level of the EDS. This included verifying the adequacy of plant load calculations for the regulation of electrical loads needed for the safe shut-down of the plant, overcurrent protection calculations for short circuit and ground faults, and the sizing and coordination of protective oevice The team reviewsd a number of cocuments related to loacs associated with the EDS. The cocusents reviewed adcressed design calculations for ac and de syste loading, voltage regulation during normal and degraded conditions, voltage regulation during sequencing of safety-related loads onto the esergency diesel generators (EDGs), degraced voltage relay setpoints, Class IE battery selec-l tion, short circuit ano ground-fault analysis, f ault current system protection, protective device coordination, and the protection of the EDS from poweF  ;

surgss. The teas, also reviewec cesign basis documents for the EDS; procedures 4 and guidelines governing design calculations otsign control, and plant mocif1-1 cations; several randoely selected design deficiency reports; repcrts on EDG ,

qualification tests, and ac system voltages during degraded voltage conditions; '

and EDS single-line, schematic, and protective relay setting crawing ' Class 1E 4160-Volt AC System

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The 4160-V (4.16-kV) Class 1E distribution system consisted of the onsite EDGs, the power feeds from the offsite grid source, and the power distribution equipment and circuits to accident mitigating loads. Three incependent EDGs provice onsitt power, one EDG for each of the safety divisions, with each diesel capable of being connected to supply its corresponding 4160 V safety bus. The 4160-V buses primarily supplied accident mitigating pump motor safety l loads and three 400-V load center safety loads per bus. The 4160-V buses and 4

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transformers were connected by 5-kV cables. Divisions 1 and 2 safety buses were nort.11y energized from the of fsite grid, which is the preferred source of power. The Division 3 safety bus feeds the high pressure coolant system (HPCS)

dnd standby service water pumps (SSW). and has normally energized f r9m a ,

non-1E " swing" bus. All reoundant safety loads were divided between l Divisions 1 and 2 buses, except for the SSW which has one pump powered from Division l To assess the adequacy of the regulation of EDS loads, the team reviewed '

I (1) the characteristics of the offsite electrical grid to verify reliability of power, (2) preferred source transformers to assess their ratings ano connec-tions to the safety buses, and (3) EDGs to assess the adequacy of their load capacity ano their ability to start and accelerate the assigned safety loads in the required time sequence. The team also reviewea (1) the transient, steacy-stato, s.aximum and sinimum voltages and tr nsient frequencies associated with the 4160-V system, (2) the capability of the 4160-V system to sustain a single feilure concurrent with a loss of offsite power, and (3) the capability of the system to transfer 4160-V safety buses to available power sources under condi-tions of postulated failure The team examined the adequacy of the size (kVA) of transformers and the load l capacity (kW) of the EDGs. The 4160-V ac safety buses end connected cables and breakers were reviewed to assess load current capabilities. The review l

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lengths versus tha ability of control transformers to covelop scequate voltage '

to energize the contactor coils and auxiliary relay The team reviewed the adequacy of the overcurrent fault protection (short circuit and ground fault) and coordination of protective devices for the 4160-V system. The electrical attributes examined included characteristics of the offsite grid with regard to its short circuit contribution to a fault in the EDS at.c the fault current protection of the off site source transforvers. The faultcurrent, overload,andreversepowerrela) protection for the EDG were reviewed for adequac .1.1 Transforser Magnetizing Inrush Current Calculation E 192-2, Revision 2, titled " Standby Diesel Generator Loading,"

, established a load profile for the diesel generator units. The team noted that

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the emergency diesel generators loading calculations did not take into account

the transf ormer sagnetizing inrush current that would occur if a 4160/480-V loao center transformer was duenergized and reener612ed under full load corici-tions. The resulting inrush kilovolt amperes of a transformer could cause an instantaneous voltage 6 top and loss of connected loads. The licensee agreed to perform an additional analysis to address the inrush curren .1.2 Emergency Diesel Generator 1 and 2 Load Sequence Timers The EDG 1 and 2 loading sequence calculation assumed that sequence tisers would operate at specitic time settings. Contrary to this assumption, calculation 12210-1A-SWP-23 regarding the tiser setting for the SSW pump (as a typical exas.ple) indicated that the timer had an o >erating time band of between 50 and 70 seconds. The EDG loading calculation,10 wever, had only evaluated the sequencing of the SSW load for a load sequencing time of 70 seconds. The team was concerned that the calculation had not considered the effects of the load being sequenced at the 50 second limit as at this limit the SSW load could overlap with the sequencing of other loads and compromisa the loading capacity of the EDG. The team had similar concerns for the sequencirJ of other loads as each load had a time band. The licensee agreed to analyze Jhe full bano of the timer's tolerances for other loads (see Appendix A, Unresolved item Nurber 90-200-01).

2.1.3 Emergency Diesel Generator Load Capacity The calculation demonstrating the loading capacity of the EDGs 1 and 2 was based on the manufacturer's shop test. The calculation concluded that the EDGs were blockscap kW)(able of carrying assured the pcstulated in the calculation loadthan were lower in the the plant because loading values the load assumed for the ciesel curing the shop test. However, the calculations cid not analyze the following conditions:

• The calculation did not analyze the potential differences between the actual accident transient and steady-state loads and the ones simulated in the shop test. For exampic, the test motors were running unloaded during the test, which was less severe than the postulated accident load condition . - -- - - . - - - - . - - - - - -.

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The loacing profile did not analyze the possibility of having to restart the load that imposes the most severe cuty (such as the low pressure core spray pusp), when the EDG was running at the saximum loa In adoition, the licensee could not provide an analysis to demonstrate that EDG 3 had the capacity to pick up postulated accident transient loads in the proper sequence. The licensee stated that additional tests were available f rom the ciesel manufacturer and agreed to perform an aoditional analysis to address the load sequencing and profile of the EDGs (see Appendix A, *

Unresolved Item Number 90-200-02).

2.1.4 fast Bus Transfer Scheme

The safety Division 3 bus was normally powered by the station unit generato The River Bend electrical ocsign, according to the updated safety analysis report (USAR), incorporated a last bus transfer scheme when normal power to the

. safety bus was lost. Under such conditions the transfer schene fast-transferred this safety bus to the preferred offsite power supply. Both the HPCS pump and

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the SSW pump were powered by this bus and there was no synchronization of the voltages of the normal power and the offsite power curing transfer. The lack of synchror.ization of these voltsges could result in motor failures due to high inrush current and transient torques in these motor The licensee acknowledgeo this concern and stateo that the fast transfer scheme L had been temporarily suspended before this inspection because of recent prob-

lems with the non-lE system. Changes to operating procedures were in place t

requiring the Division 3 bus to be temporarily powered from the offsite grid

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and not from the main generator. However, the licensee agreed to continue using the temperary operating procedure of supplying power from the offsite grio untti studies were performed to evaluate the postulated failures of the HPCS and SSW pump motors during a fast bus transfer (see Appendix A, Unresolved Item Nunter 90-200-03).

2.1.5 EDG Short Circuit Contribution Calculations for the short circuit contribution of the Divisions 1, 2, and 3 emergency diesel generators did not consider the short circuit contribution during the independent testing of the diesel generators in parallel with the unit generator. Such an event was assumed in the calculations to be hypotheti-cal while the USAR stated that the testing of the standby diesel generators could be performeo by paralleling them with the unit generator. On the basis of its own calculations, the team was concerned that the short circuit ratings of the Cisss IE switchgear including the circuit breakers could be exceeded under such conditions. For example. the value of short circuit currents for a postulated fault at the Division 3 bus would be 35,783 amperes interru> tin This value exceeded the 35,000 ampere current interrupting rating of tie associated switchgear. The short circuit ratings at the other two divisional buses were similarly affected. The team concluded that the design calculations

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did not demonstrate acceptable short circuit capability for the safety-related

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switchgear during possible incependent testing of the EDGs in parallel with the unit generator. The licensee indicated that operating procedures will be revised to preclude the possibility of testing EDGs for Divisions 1 and 2 in

! p6tellel with the onsite a in generator and that Division 3 bus would continue to be temporarily powwred from the offsite power sourc .

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The team also noted that short circuit calculations for the independent paral-leling of EDGs 1 and 2 and the preferred offsite source indicated low margins ,

between the calculated short circuit values and the equipment short circuit  :'

ratings (as low as 0.5 percent). The team considered this low sargin to be insufficient to account for possible calculation inaccuracies and load change ,

In sodition, the calculations assumed a 1.00 PU (per unit) for the Division 3 '

bus rather than a postulated 1.05 PU on this bus when testing the Division 3 EDG. The licensee e a short circuit capabi$ reed to perform an additional analysis to address the1ty of the a'

Item Nunber 90-200-04). y 2.1.6 Neutral Resistor Sizing No calculation could be provided for the sizing of the EDG 3 grounding resis-tor. Calculations for sizing of neutral grounding resistor for EDGs 1 and 2 did not address the requirements of current capability and related thermal considerations for the resistors, in particular, the time rating of the

- resistcrs, and the effect of prolonged ground fault current was not addresse The licenste agreed to perform meditional calculations to address the sizing of the resistors (see Appendix A Unresolved item Number 90-200-04).

2.1.7 Transformer Surge Protection ,

The design calculations did not consider protection of the 4160/480 V load center transformers against lightning and system surges. These transformers powered 480-V safety division buses. The licensee had installec a surge arrester on the high voltage side of the 230/4.16-kV offsite source trans-former, however, they had not consicered the potential for a high discharge from the arrester damaging the 4160/480-Y load center transfomers connected cown the line. The licensee stated that a modification request (MR) hao been prepared before the inspection to add arresters on ti.e low voltage side of the '

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offsite scurce transformers. The team reviewed the MR and was concerned that since the proposed arresters were not directly connected to the 4160/480-V load center transforraers, the protection of the transformers may be inadequat The 11ct. 3e agreed to perform an analysis to verify the protection of the load L centertransforcers(seeAppendixA,OpenItemNumber 90-200-05).

l 2.1.8 Undetected Ground Fault During a LOCA and a concurrent loss of offsite power, the Division 3 bus (carrying HPCS and SSW system loads) would be powered by the EDG However, should the preferred offsite source become available, a transfer of the HPCS bus to the offsite power would be manually initiated. EDG 3 was protected through a high resistance grounding scheme which limited the ground fault current to a small value. The ground f ault protection for the Division ; bus

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load feeder circuits was set to pick up at a much higher current. The team was i concerned th6t if a ground fau~t developed in one of the bus loads while it was H being fed by EDG 3 the EDG 3 grounding scheme rather than the bus load p ounding system could operate. For ex6mple, a ground fault that developed in the SPCS motor could be annJnciated in the control room as a ground fault at EDG 3. Under such concitions the operator (since no procedural restraint existed) could have allowed the bus to be transferred back to the of fsite grid, resulting in a trip of the faulted load. This load trip was postulated to

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occur because the preferred offsite source grounding scheme could allow a

. current of about 1000 amperes to flow to a ground fault. The team concluded M

i that under such conditions a transfer to the offsite power source should be precluded. The licensee immediately issued a written operator restraint to prevent transferring the Division 3 bus from the EDG 3 power source to offsite power underground fault conditions (see Appendix A, Unresolved item Number 90-200-06).

2.2 Class 1E 480 Volt System The team reviewed selected 480-V Class 1E motors o overcurrent protection, including cable voltage drops during the starting and running of these motor '

This review included verifying the selection of the trip coils and motor overload heaters for the 480-V Class 1E motor-operated valves (MOVs), and the length ad size of the cables connecting these MOVs to the motor control cen* The team also reviewed preventive maintenance procedures for thermal over':a relays and r?W ' case circuit breakers, and for the selection of 600-V power and cont m m oles.

Errors were found on oaign drawings including inconsistent load data, incor-rect connections of load center buses on the single-line diagrams, and nonnally open contacts beina incorrectly noted as normally closed. In addition, the calculation for the starting voltage at the air compressor motor assumed a cable impedance for 93 feet of 2/0 AWG cable while the single-line diagram indicated that the motor cable had a length of 250 feet. The licensee agreed to correct the identified drawings and calculation .3 Class 1E 125 Volt DC and 120 Volt AC Systems The team on a sample basis reviewed (1) the voltage drop and short circuit calculations for the dc distribution system to ensure t1at the associated equipment allowed adequate voltage to associated loads and had adequate protec-tion for postulated fault currents, (2) the 125-Y de control circuit voltage

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drop calculations to verify that the circuit lengths did not compromise the energization of the closing coils used in the control circuits of the 4.16-kV and 480-V circuit breakers, (3) the coordination between the fuses at the switchgear and the dc distribution panels to ensure that the installed fuses did not cause a loss of a Class 1E bus and associated accident mitigating loads during postulated fault currents, and (4) fuse ratings to ensure that they were properly selected to sustain the starting current of the charging motor and to open the circuit in case of postulated short circuit faults. Two findings in these areas are discussed belo . V-DC Cable Sizing The calculation for sizing of de cables did not consider the short circuit contribution from the battery chargers to the 125-V dc system. The battery chargers could supply up to 375 amperes (based on the current limit mode feature) during a short circuit on the distribution panel bus. The calculation also did not consider the effect of the ambient battery room temperature (60* F) on the resistance of the cables connecting the battery to the dc distribution panel. The team determined that the resistance of the cables would be much lower than the value used in the calculation, thereby increasing the short circuit current. The licensee performed calculations and agreed to add an appendix to the calculatio __ _

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2.3.2 Short Circuit Analysis for Control Circuits The licensee had not performed a short circutt analysis' for the protection and coordination of 125-V de and 120-Y ac control circuits. The team was concerned that based on inedequate documentation, numerous control. circuits critical for the safe shutdown of the plant may not be acequately protecteo against postu-lated faults. For example, calculations did not exist to demonstrate that the fuses in the switchgear were coordinated with the upstream fuses at the dc distribution panels. The team was concerned that a potential lack of coordina-

tion-could cause the loss of an entire switchgear and compromise the safe shutdown of the plan The licensee performed an issnediate analysis which verified the operability of these specific circuits baseo on the sufficient independence and redundancy of these circuits to perform their safety function assuming a single failure. The licensee also concitted to complete calculations for all control circuits by

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March 1991 (see Appendix A, Unresolved Item Nutter 90-200-07). q 2.4 Conclusions The team concluded that the electrical design of the electrical systems for the electrical. distribution system at the River Bend station was generally i acceptable. Voltage regulation of loads as well as protection and coordination of most EDS equipment were appropriate. Most design docusents were accessible .,

and relatively easy to retrieve. Staff support consisted of an adequate l number of engineers with an understanding of the relevant technical issue The team identified various tindings with regard to inadequate design reviews for certain conditions of operation and postulated failure of certain EDS j

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1 equipment. .In addition, certain calculations had mistakes in methodology,

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assumptions and missing references. The tean,noted that the plant engineering staff had not performed a critical review of the calculations performed by the architect-engineer. 1he licensee concittec to perform analyses and comnlete revisions of all appropriate calculations >y March 199 .0 MECHANICAL SYSTEMS  !

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To ceterstine the ability of mechanical systems supporting the emergency diesel generators (EDG) to function during postulated design basis accioents, the team on a sample basis reviewcd oocumentation and conducted walkdowns of fuel oil storage and transfer, lubricating oil, starting air, and diesel heating and i

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cooling equipnent. The team reviewed equipnent associated with the heating, i ventilating, and air conditioning (HVAC) of the diesel generator building, '

I i- battery rocms, essential switchgear rooms, and selected EDG and HVAC design mcdifications. The team reviewed the translation of various techani al loads j (selected pumps and MOVs) to electrical loads for input into design basis calculation l 3.1 Trip Signal for Standby Service Water Pumps

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By design, the standby service water (SSW) system initiates on low differential

' pressute and replaces the normel service water (NSW) to the safety-related hest exch6ngers(includingtheaieselgeneratorcoolers). However, under postulated l accident conditions, if one of the three NSW pumps remainec energized and

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operating, the low-system pressure trip to start the SSW pumps may not actuate.

Under such conditions the NSW would continue to supply the safety-related heat

, exchangers, but at less than the design flow rates. This condition had not been previously analyzed by the licensee and therefore actual discharge pres-sures or resulting flow rates were not known. The licensee agreed to analyze thisconditionofoperation(seeAppendixA,UnresolvedItemNumber 90-200-08).

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3.2, EDG Air Start Lock Out Feature .

The EDG air start system had a lock out feature that prevented automatic starts when the air pressure dropped to 150 psig. Operators were nomally directed to maintain pressure above the 210 psig alarm setting. However, the plant Techni-cal Specifications allowed the pressure in the starting air accumulators to '

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drop to 160 psig. - The team was concerned that the lock out feature could prevent the automatic start of the EDG if, during the first start attempt at 160 psig, the air accumulator pressure dropped to 150 psig (start cycles typically require 10 to 20.psig). -The licensee agreed to review the Technical

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SpecificationlimittoensureautomaticstartingoftheEDGbeforereaching)the lock out feature setpoint (see Appendix A, Unresolved Item Number 90-200-09 . .3 Maximum Temperature in Piping Tunnels Calculation PB-261 determined maximum temperatures in electrical and piping tunnels.during LOCA conditions. This calculation erroneously concluded that the' tunnels would reach a maximum temperature of 122' F over an infinite period ,

of time. The team determined that this error was caused by the misapplication I of an equation that related time and temperature. The licensee subsequently l demonstrated that the maximum temperatures in these tunnels would remain below l the design maximum of 122' F during accident conditions. Because this same  !

equation was used in a number of time and temperature plant design calcula- .

tions, the team was concerned that there may be other misapplications of the l

. equation. The licensee reviewed all calculations using this methodology and

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reported that no other similar deficiencies existe .4 Battery Room Temperature The station battery capacity was calculated on the basis of an electrolyte temperature of 60' F. However, no alarms were in place to monitor for low temperatures in the battery rooms. Apparently, if the battery room temperature dropped below 60' F as a result-of non-1E heater failure or because of I extremely cold weather, the battery capacity would be in an unanalyzed condi-tion and the contiol room operators would not be alerted to the problem. The team had no immediate safety concerns because temperatures are normally main-

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tained in the 70' F range. The team, however, concluded that appropriate  !

administrative controls are required to be in place to ensure battery room  :

temperatures remained above 60' F. The licensee agreed to review for proper j control J 3.5 USAR Inconsistency on Service Water Pumps The USAR stated that all SSW pumps started automatically during the initial l phase of recovery from a LOCA. However, the SSW pumps are automatically l initiated only on low differential pressure in either the normal service water )

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or r6 actor plant closed cooling water system. Therefore the statement in the USAR was incorrect unless the LOCA occurred simultan6cusly with a loss of offsite power or other events resulting in low differential pressures. The team was concerned that the above USAR stattment was aisleading. The licensee agrt6d to take action to correct this statemen .6 Unanalyzed Piping Stress Under LOCA conditions the SSW pumps could start simultaneously when powered by the Division 1 and 3 safety buses. Simultaneous starting of these two pumps or.

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the sage service water loop coulo impose significantly higher hydraulic stress on the associated piping. The team noted that such piping stress had not been analyzed. The licensee agreed to analyze this condition (see Appendix A, Unresolved Item Number 90-200-10).

3.7 Conclusions

The tear, concluded that appropriate technical staff were knowledgeable of the sechanical systems. . A significant amount of infomation was available through calculations and system testing to assess the sachanical systesis. The team considered this a strength in regard to engineering and technical suppor .

A nut.ber of fincirgs were identified in the eachanical area with regard to inactquate design reviews which indicated a weakness in the design control of EDG equipment. However, the team had no concerns regarding the operability of the associat;d equipment because of the findings, based upon evaluations perforred by the licensee during the inspectio .0 EDS EQUlFMENT To confirm the implenentation of the electrical system design, the team inspected the as-built configuration of a sar.ple of selected safety-related equipnent in the plan Theteamalsoexar.inedalimitednumberofmodificationrequests(MRs), control proceoures field change notices (FCNs), and 06 sign change notices (DChs)

related to ths EDS. The design evaluation review and approval process were evaluated for its adequecy and comprehensiveness to include screening MRs for required 10 CFR 50.59 saftty evaluation .1 Equipment Walldowns The EDS equipment conformed to design requirements. Switchgear and buses were properly labeled, eksily identifiab e, and accessible. Proper physical septration existed in the field for the EDS equipment and components. Gooc housekeeping was 6pparent in the plant,16w deficiency tags were observed, and the equipnent appeared to weil siaintained. The support staff was knowledge-able, c apetent, and tinely in answering question The licensee hed controls in place for fuse replacerent through administrative precedure ACM-0022. "Concuct of Operations" which required that replacement iuses be verified for proper size end type usir.g the applicable design occu-ments. Instclied fuse sizes could not be reviewed by the tehm due to energized equipmen . . . . . . . . . . . . . . . . . . , . _ . _ . . . _

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.' Drawings used to facilitate the walkdowns were clear, traceable, and in must cases, reflecteo the fielo certified configuration.- Minor inconsistencies between design dramings and installation of certain EDS equipsent were noted, i

The ranges of sume relays were incorrectly noted on the drawings; and some equipment was mislabeled. The licensee confirsed that the equipment in the field ret design requirements but that drawings had not been updated. The licensee issued DCN's to correct these document errors and to implement the necessary corrective action. The identified deficiencias were not safety significan .2 Equipment Hootfications i

The tean: reviewed 27 modifications af f ecting the EDS. Mocifications included changes to EDG systems, breakers, fuses, and relays. A significant backlog of secoification' requests, condition reports, and unincorporated crawing changes existed. The licensee confirmed that they were addressing these concerns through specific task force recossnendations and planned appropriate actio '

The engineering design and modif1 cation control process was well procedur-ai? zed. Design changes were reviewed and approved in accordance with the Technical Specifications and established QA/QC controls. The licensee co ducted post-modification tests, and performed test result evaluations before declaring the affected components and systems operable. Most test results reviewed were within previously established acceptance criteria. The licensee reviewed test deviations and, where applicable, accomplished ratesting. The licensee's procedures controlling modification work and doeurantation records were generally complete and comprehensiv The design evaluation review process appeared to effectively incorporate, where appropriate, 10 CFR 50.59 safety evaluations. The licensee had adopted and implemented the huclear Safety Analysis (hSAC-125) guidelines for 10 CFR 50.59 safety evaluations. Aoditionally, the licensee had performed engineering cesign control QA audits, surveillances, and safety system functional inspec-tions (SSFis) which apparently were beneficial in self-identification of problem area .3 Equipment Testing and Calibration River Bend had well-structured programs in place for performing preventive saintenance, surveillance and testing of EDS equipment and components. The programs addressed the testing of emergency diesel generators and associated syster.6, transformers, motcrs, batteries, battery chargers, inverters, circuit breakers, and protective relaying. The preventive maintenance program was found based on vendor recommendations, and the surveillance testing was in accordance with the plant Technical Specification requiren.ent The scope of the test program was adequate. The maintenance and surveillance test procedures were well written and easy to follow. The technicians were well trained and were familiar with the equipatnt. The test program samples reviewed appeared to be adequate to verify the functional performance of the equipmen l

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Batteries appeared well seintained and were tested in accordance with Technical Specification requiresents. The results of preventive saintenance and testing peiformed on the inverters were consistent with the acceptance criteria estab-lished in the plant procedure The team observed that surveillance test procedure STP-30-1602 indicated that the acceptance triteria of the data sheets for relay setpoints were not consistent with the relay setpoints specifiec in Table 3.3.3-2 of the plant Technical Specifications. The licensee performed an inneciate review of the Technical Specification and determined that there was an error in the accep-tance criteria of the cata sheets, but that the installed relay settings were within the range of setpoints specified for both time and voltage in the lechnical Specifications. The licensee agreed to revise the appropriate procedures to cortect voltage levels and tise setpoints consistent with the the Technical Specification . During recalibration of relays, the team observed that if relay drifting was

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found within a range specified in Table 3.3.3-2 of_ the plant Technical Specift-cations,. the relays were placed back in service "as-found" without any adjustaents to the settings. The licenne stated that the "as-found" toler-anc(; were within the calibration tolerances. The licensee also stated that the applicable procedures were being reviewed to determine arty impact and need for revisio .4 Conclusions The installation of EDS equipment was adequat Modifications were well procedura11 zed and design changes were approved before bair.g implerented. Adequate post-modification testing was parforse Overall the licensee had instituted a well structureo periodic preventive

. maintenance and test program for electrical systems and components. The frequency of maintenance and surveillance and testing was adequate to verify functional performanc .0 ENGINEERING AND TECHNICAL SUPPORT The team assessed the capability and perfomance of the licensee's organization toprovideengineeringandtechnicalsupport(E&TS). The team examined interfaces _between the technical disciplines internal to the engineering organization and between the engineering organization and the functional groups perfoming design reviews, field modifications, surveillance, testing, and maintenanc The team also reviewed a sampling of licensee event reports (LERs), condition reports' (CRs), independent safety enginecring group (ISEG) operating event reports (0ERs), QA audits, and recent NRC inspection reports to ascertain the adequacy of the licensee's root-cause analysis and corrective action program Further, the team reviewed licensee follow-up actions related to GE AKR-30 circuit breaker failures and the predictive maintenance trending progra _ . . . . . . . _

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5.1 Organization and Key Staff in January 1990 River Bend underwent significant organizational changes which were intended to streamline the organization and to improve management over-sight. The changes includse reducing the reliance on contracted engineering

,- effort anc placing more emphasis on the ESTS staff, including implementation of L a system engineer approach. The team noted that the system engineers and the operations st6ff appe.r te have developed a good working relationship ouring

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the six rnonths since the system engineer approach was initiate (ht licensee's organization included appropriate E&TS site groups for cesign engineering, systes) engineering, and a training section. Throughout the inspection, the E&TS :taff provideo tisely and technically sound responses with regard to the design i.nd implerrentation of the EDS. The training program for the E&TS personnel was sti)1 being formlized, however, the staff was noted to be s.aking an aggressive effort to complete required initial training.

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" 5.2 koot Cause Analysis anc Corrective Actions L The team noted that recent LERs, QA audits and other documents indicated evidence of thoroughness in root-cause analysis. Examples included the licensee's investigation, testing, and corrective actions related to the prctective relays, circuit breakers, and transmitter The mjority of the licensee's trending programs were in the developmental phase. The systems engineers die not have ready access to present trending data bases through an adequately accessible computer system, because.of this, cata collection, trending, and evaluation took several staff hours to develop trend information for a specific item at a specific time. Through discussions with key system engineering unagers.-it was learned that the licensee was developing additional trending programs (e.g., thermography, grease analysis, battery testing. and Doble testing for the EDGs and large load electric s.otors ) . r'owever, there was no program to trend the drifting of relay set-points to provide a more significant monitoring parameter to predict relay

' f ailures and to ascertain whether calibration schedule adjustsents were warranted. The licensee agreed to review the need for such a program.

L 5.3 Engineering involvement in Operations The team reviewed the involvement and effectiveness of engineering staff with regard to surveillance testing, post-maintenance testing, temporary modifica-tions,' m intenance support, and trending and testing frequencies. The licensee's recent reorganization structure for system engineering appeared to

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L l have incret angineering involvesent with operations and maintenance.

l Engineering ' volvement in cuily planning meetings with other support groups at L the site appeared to have increased the engineering group's involvement in the

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day-to-oay resolutions of operational events and problem .4 Self-Assessment and Training The.tvan, noted that both the system and design engineering groups had programs in place for self-assessment. System engineering had established a sonthly evaluation progruns for individual systens engineers to support the recent

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restructure of system engineering organization expectations. The design group was tracking items such as the total number of field change noticas per sodifi-cation request, backlogs of conditions reports, and projected versus actual staff hours expanded in various activitie '

Training program requirasents in most cases had been established, fully devel-oped and completed in a timely manne .5 Conclusions The engineering and technical support (E&TS) available to the River Beid plant appented to be adequate. Although the team found a'significant backlog of s.ocification requests, condition reports, and unincorporated drawing clanges, the licensee appeared to have appropriate plans and staff to adoress tne backlog. The licensee's organization provided appropriate E&TS groups to perform required functions. The E&TS groups adequately interfaced tr identify end resolve concerns identified at the site. The licensee had s.ade excellent

. progress in the oevelopment and implesentation of the associated training progra The inspection team concluded that the licensee's root cause analysis and corrective action programs appeared to be continually improving. Although the trencing programs were in the cavalopnental phase, their direction and emphasis appeared to be adequat .0 GENERAL CONCLUSIONS Based on the inspection sample, the team did not identify any operability problems, and concluded that the design of the EDS system was generally adequate. Emergency power sources were sized properly and adequate voltage was applied to essential buses with regard to EDS loads. In most cases, the protection ano coordination of the protective equipsent were adequate and the scope et testing the EDS equipnent was appropriate. Staff support for the EDS f rom the corporate offica and site was acequate. Staff were knowledgeable and con.peten home deficiencies existed in the area of design control with regard to inadequate design reviews for certain conditions of operation and postulated failures of certain EDS electrical and techanical equipment. Several findings in engineering calculations and drawings were identified including lack of calculations, unanalyzed postulated failures and conditions of operation, unsubstantieted assumptions, computational errors and missing references. The t am had no significant safety concerns because of additional analyses and

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information provided by the licensee during the inspectio The team conoucted an exit meeting on June 22, 1990 at the River Bend Station to discuss the major areas reviewed during the inspection, weaknesses observed, and findings. NRC management from-NRR and Region IV and licensee representa-tives who attendeo this meeting are identified with an asterisk in Appendix B of this report. The team discussed licensee actions on major issues and a.kncwledged staff constments made during the inspection. The licensee did not icer.tify any docunents or processes as proprietar l

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APPENDIX A Findings

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UNRESOLVED ITEM NUMBER 90-200-01 FINDING TITLE: Emergency Diesel Generators 1 and 2 Load Sequencer Timers (Section 2.1.2 of report)

DESCRIPTION OF CONDITION:

Thedieselgeneratorsequenceloadingcalculation(Reference 1)assumedthat timers would operate at fixed times. Contrary to this assumption, calculation 12210-IA-SWP-23 regarding the timer setting of the SSW pump (as a typical ex-ample) identified a timer operating band of between 50 and 70 seconds. The team

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noted that the timer in the field was set at 60 seconds nominal operating time, while the calculation assumed 70 seconds.

i The team concluded that the use of a fixed time could not be justified on the '

basis that a timer could operate anywhere within the time band and had the potential of overlapping loads. The team determined that the EDG loading calculations should consider both limits of the band (such as 50 and 70 seconds) so as to evaluate all potential loading condition In response to the-team's finding, the licensee performed additional analysis for the example reviewed to include the timer's tolerances and mitigate con-cerns. The licensee agreed to review the calculations for the loading of all other applicable load REQUIREMENT:

10 CFR Part 50,- Appendix B, Criterion Ill, Design Control, requires design control measures to be provided for verifying the adequacy of design by per-forming design reviews, using alternate or simplified calculational methods, or providing a suitable testing progra REFERENCE: GulfStateUtilities(GSU),RiverBend,CalculationE-192,Revisior3, dated June 23, 1989, Diesel Generator Loadir.;.

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UNRESOLVED ITEM NUMBER 90-200-02 I

FINDING TITLE: Emergency Diesel Generator Load Capacity )

(Section 2.I'.3 of report) q

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DESCRIPTION OF CONDITION:

The emergency)

(Reference diesel generators 1 acceptance 1 and criteria were 2 sequence based loading on the senuf calculation acturer's shop test (Reference 2). The criteria establishea that if the load steps oeveloped by the calculation were lower than the ones in keference 2, then the loading was acceptable (Reference 1, page 7, paragraph 4). 'In examining this approach the  ;

tean, f ound that the licensee had not analyzed the differences between the '

actual loads and the ones used in the shop test. These differences could affect the capacity of the diesel to perform its function. For example, the r largest load step performed during the shop test was for a 1000 HP motor and a 300 HP motor. However, no analysis was s.ade to determine if these two motors would result in starting transients at least as severe as the LPCS pump motor startug transient, in addition, Reference 3, page 15, paragraph 7.2.3, l

"bargin Tests," requirta "A margin test load of at least 10 percent greater j than the magnitude of the acst severe single step load within the load profile...," which would have resulted in a load of 1375 HP, which is greater '

than the total of 1300 HP made up by the two motors used in the tes The licensee also could not provide an analysis to comonstrate that EDG 3 would pick up Icads in the proper sequence so as not to overload tne diese lhe licensee provided results of an onsite test but this test did not simulate postulated accident transient load The licensee indicated that additional tests were available from the anufac-turer to accress these concerns ar.d agreed to perform an analysis based on their review of these test REQUIREMENT:

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.10 CFR Part 50, Apperidix B, Criterion Ill, Design Control, requires design centrol measures to be provided for verifying the adequacy of design by per-forming design reviews, using alternate or simplified calculational methods, or providing a suitable testing progra ;

REFERENCES: GSU, River Bend, Calculation E-192, Revision 3, dated June 23, 1989, Diesel Generator Loadin . GSU, River Send, EDG shop test, per Specification No. 244.70 . IEEE Standard 367-1984 (see River Bend USAR page 8.3-47).

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L '. ; UNRESOLVED ITEM NUMBER 90-200-03~

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-FINDING TITLE: Fast Bus Transfer Scheme (Section2.1.4ofreport)

DESCRIPTION OF CONDITION:

The River Bend design in accordance with the USAR incorporates a fast transfer I scheme in case power to the station normal buses is lost. This scheme trans-  ;

fers the affected buses to the preferred offsite power supply. Safety Divi-sion 3 bus is normally powered by the station unit generator. When normal power to this bus is lost, the transfer scheme Mast transfers this safety bus  !

to the preferred offsite power supply. Both the. high pressure coolant system I and the standby service water pump motors are powered by this bus. The team noted that there was no synchronizing of the voltages of. the normal power and l the offsite power during this transfer. The team was concerned that the lack l

. of synchronization of these voltages for the power supply to these motors may i cause high currents and transient torques that could result in failures of l these motors during an acciden The licensee acknowledged this concern and stated that the fast transfer scheme had been temporarily suspended before the inspection due to recent problems with the non-1E system. Changes to operating procedures were in place for this temporary change which required the Division 3 bus to be fed from the offsite l grid and not from the main generator as stated in the USAR. -However, in view l of the team s findings, the licensee agreed to continue using the temporary t

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operating procedure until studies were performed to evaluate-the team's con- -l cerns regarding the postulated failures of the HPCS and SSW pump motor REQUIREMENT:

10 CFR Part 50, Appendix B, Criterion III, Design Control, requires design control measures to be provided for verifying the adequacy of design by per-forming design reviews, using alternate or simplified calculational methods, or providing a suitable testing progra REFERENCE: GSU, River Bend, Drawing EE-1A-13. Main One Line Diagram Key Dwg-Power l

Distribution, Revision 13, dated May 3, 198 '

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e UNRESOLVED ITEM NUMBER 90-200-04 o

FINDING TITLE: Design Calculation Deficiencies (Section 2.1.5 and 2.1.6 of report)

DESCRIPTION OF CONDIT10h:

The tvan, noted several deficiencies in design calculations. Deficiencies include unanalyzed postulateo f ailures and conditions of operations, onsubstan-tiated assumptions, missing references, and computational errors. Apparently critical reviews were not perfor1ned by the licensee with regard to calculations perf ormed by the Architect-Enginee SSU, River Bend, 4160-V System Short Circuit Calculations E-131 Revision 1, cated February 2,1987, pace 11 indicated that in testing the diesel generators inparallelwiththenormalbuses,theshortcircuitratingsofthenorral

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bus switchgear would be exceeded. The calculation, however, referred to this parallel alignment as " hypothetical." River Bend USAR, August 1987, page 8.3-51, paragraph 8.3.1.1.5.5.1 indicated that the testing of the standby diesel generators was, in fact, performed by paralleling the EDG with the norr.a1 buses. For example, based on their own calculations and from inforra-tion in calculation E-131 page 69, the team determined that the value of short circuit current for a postulatea fault at the Divisional bus 3 would be 35,783 amperes interrupting. However, this exceeoed the 35,000 amperes switchgear and circuit breaker ratings. The short circuit rating at the other two civisions were similarly affected. The licensee a alignrent in the future (Section 2.1.5 of this renort) greed to preclude such .

Calculation E-131 assumed 1.0 (or 4160 Volts) per unit (PU) system voltage, while the plant conditions could be up to 1.05 PU voltage. E-131 Case 6A a'..o indicated marginal short circuit protection for the case of paralleling EDGs 1 or 2 with toe preferred offsite source. A 0.5 percent margin was indicate Such a_ low margin was considered not sufficient to account for possible calculation inaccuracies,. load changes, and the incorrect e .umption regarding PU system voltage (Section 2.1.5 of this report).

No calculation was provided for the sizing of the EDG 3 grounding resistor, in addition, the team noted that the alculation E-130 Revision 2, dated July 28, 1986, for the sizing of the EDC 1 and 2 grounding resistors did not address the requirements of current capab;lity and related thermal considera-tions for the resistors. in particular, tha time rating of the resistors, and the effect of prolonged ground fault current were not addressed (Section 2. of this report).

REQUIREMENT:

10 CFR Part 50, Appendix B, Criterion Ill, Design Control, requires design control measures to be provioed for verifying the acequacy of design by per-forming design reviews, using alternate or simplified calculational methods, or provicing a suitable testing progra l A-4 l m

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FINDING TITLE: Transformer Surge Protection

(Section 2.1.7 of report)

DESCRIPTION OF CONDITION:

The prot'ection of dry type 4160/480-V load center transformers against lightning'and system surges was not considered. This type of protection would consider the surge transmission through the preferred offsite source trans-former, af ter the discharge by the arrester provided on the high voltage side of the 230/4160-V preferred transformer.- The licensee irdicated that a modifi-cationrequest'(MR)hadbeenpreparedtoaddarrestersonthelowvoltageside of the preferred transformers for surge protection. However, the team was concerned that since the_ proposed arresters were not planned to be directly connected to- the dry type load center transformers, they may not provide

, adequate protection. The licensee indicated that a study would be performed to analyze the adequacy of the KR in regard to protection of the load center transformer REQUIREMENT:

10 CFR Part 50, Appendix B, Criterion !!!, Design Control, requires design control measures to be provided for verifying the adequacy of design by per-forming design reviews, using' alternate or simplified calculational methods, or providing a suitable testing progra . REFERENCES: GSU, River Bend, Calculation E-200, Revision 1, dated March 20, 1985, Overcurrent Devices Set Point . IEEE' Standard 308-1980, IEEE 141, 1986, IEEE 242, 198 .

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UNRESOLVED ITEM NUMBER 90-200-06

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FINDING TITLE: Undetected Ground Fault (Section 2.1.8 of report)

DESCRIPTION OF CONDITION:

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During a LOCA. if. the preferred offsite source is not available, the HFEi bus (Division 3) is transferred to the EDG 3 to supply the bus loads. However, should the preferreo offsite source become available, a transfer of the HPCS l bus could be mar.ually initiated. This approach generally is acceptable and L consistent with prevailing practic The team noted that in case of a ground fault on one of the Division 3 bus loads the ground fault my not be properly annunciatec. This is because the l

1 EDG 3 is groundeo through a high resistance scheme (Reference 1) which limits l

the ground f ault current to a very small value (about 2-3 amps). Since the ground f ault zero sequence protection on the load feeder is set to pick up at

! 10 amps, (Reference 2) it may not operate. Assuniing adequate sensitivity is

! afforded by the EDG ground fault protection (Reference 3), an alarm will be '

given in the control room, however, this indication will be incorrectly annunciated as a ground fault at the EDG rather than at the load. The operator may uncer such ccnditions transfer the bus to the preferred offsite source if available. However, such a transfer will cause the ground fault to trip the f aulted load because the preferred of fsite source grounding schene allows a current of about 1000 amperes to flow to a ground taul The team concluded that since continuous operation of the EDG under a LOCA l'

t would be desirable and allowable, and since the ground fault woulo be very

! stroll, such a transfer should be precluded. The operator should also be

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alerted of the possible location of the ground f ault (Reference 3). The ,

licensee agreed to modify the operating procedures to address this postulated o concition of operatio REQUIREMENT:

10 CFR Part 50, Appendix B, Criterion 111. Design Control, requires design control measures to be provided for verifying the adequacy of design by per- l r forming design reviews, using alternate or simplitied calculational tr.ethods, or providing a suitable testing program.

l REFEEENCES:

l GSU, River Bend, Drawing EE-1A-13, Main One Line Diagram Power Distribu-tion, kevision 13, dated May 3, 198 .

GSU, River Bend l. Drawings 12210-E-238 (May 1,1984), and 12210-E-233 (April 10,1985 IEEE Standard 308-1980, paragraph 6.2.1.(6) states: " Protective devices shall be provided to limit the degradation of the Class 1E power system Sufficient indication shall be provided to identify the actuation of a protective device."

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UNRESOLVED ITEM NUMBER 90-200-07 FINDING TITLE: Short Circuit Analysis for Control Circuits (Section 2.3.2 of report)

DESCRIPT10h 0F CONDITION:

The team noted that the licensee had not performed an analysis for the short circuit protection of 125 V de and 120 Y ac control circuits. These circuits, for example, provided power to close critical 4.16 KV and 480-V breakers associated with accident mitigating loads. The team reviewed some sample circuits for voltage drops and the sizing and coordination of fuses. Durin the review of voltage drop calculations (Reference 1) for dc. circuits, the team noted that the control circuits reviewed had excessive lengths. The team determined that the circuits' reviewed did not compromise the safety of the plant. However, the team was concerned that excessive cable lengths in other control circuits could prevent the clearing of shorts and that uncoordinated

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e fuses may cause loss of critical EDS equfpent. Thelicenseeperformedan immediate analysis based on available redundancy of safety divisions, and committed to complete calculations for tratection and coordination of these control circuits by March 199 REQUIREMENT:

10 CFR Part 50, Appendix B Criterion III, Design Control, requires design control measures to be provided for verifying the adequacy of design by per-forming design reviews, using alternate or simplified calculational methods, or providing a suitable testing progra REFERENCES: Calculation E-209 Revision 1 Cable Loop Length Criteria for Voltage Drop for DC Circuit . IEEE Standard 242-1975, " Recommended practice for protection and coordina-tion of industrial-and commercial power systems."

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! FINDING TITLE: Trip Signal for SSW Pumps (Section 3.1 of report)

DESCRIPTION OF CONDITION:

Under postulated accident conditions with a loss of off-site power, the nomal service water (NSW) pumps' trip, and standby service water (SSW) is initiated on a low differential pressure signal of 76 psig in the NSW system. However, if power is partially lost such that only one NSW pump remains energized (e.g.,

oneDivisicnalbusislostandtheotherisenergized) loads.a single Under continue to rua and attempt to supply all NSW cooling NSW such pump may conditions SSW may not be initiated because the NSW header pressure may not 6larly ropunder belowconditions che low differential pressure with reduced systemtrip flowsetpoint of 76 p(sig, requirements particu-such as in cold

- weather). The team considered this to be an unanalyzed conditio The licensee agreed that it was possible for one NSW pump to continue to operate but that the SSW system would normally initiate on the 76 psig low pressure trip. The licensee also stated that, under the above postulated conditions, if the 76 psig trip did not occur, the control room operator would be alerted to a reduced service water flow condition by appropriate alarm However the team noted that appropriate alarm response procedures (601-16 and 877-31),did not. acknowledge the possibility of a reduced flow condition to be a result of a non-initiation of the standby service water system. The licensee agreed to analyze this condition of operatio REQUIREMENT:

The applicable requirement is 10 CFR 50, Appendix B, Criterion Ill, Design Control, which-requires design control measures to be provided for verifying or checking the- adequacy of desig REFERENCE: USAR Chapter 17, Accident Analysi .

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UNRESOLVED ITEM NUMBER 90-200-09

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FINDING TITLE: EDG Air Start Lock Out Feature (Section3.2.ofreport)

DESCRIPTION OF CONDITION:

The EDG air start system had a Technical Specification limit (Reference 1) of 160 psig for operability and a lock out feature that actuated at 150 psi Startup testing indicated that the minimum decrease in air pressure per start cycle was approximately 15 psig. Therefore, the lock out feature could prevent the automatic start of the EDG if the first start was initiated at 160 psig and was unsuccessfu The low pressure alarm in the control room actuated at 210 psig, and operators were normally directed to maintain pressure above the 210 psig alarm settin The licensee stated that the air pressure would not be allowed to fall to a 2 lower value where the starting of the diesel would be compromised. However, the team was concerned that condition could occur because of the allowed Technical Specification limit of 160 psig. The licensee agreed to review the pressure limit setpoint for a more appropriate To hnical Specification limi REQUIREMENT:

The applicable requirement is 10 CFR 50, Appendix B,. Criterion Ill, Design Control, which requires the design basis to be correctly translated into specifications, drawings, procedures, or instruction REFERENCE: Technical Specification 4.8.1.1.2.a.7 page 3/4.8.5, AC Electric Source .

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UNRESOLVED ITEM NUMBER 90-200-10 FINDING TITLE: Unanalyzed Piping Stress (3ection 3.6 of report)

DESCRIPTION OF CONDITION:

The team observed that both standby service water pumps 1SWP-P2A and ISWF-P2C are connected to the Division 1 standby service water. loop. These two pump-rotors are powered by 4160-Y Division 1 and Division 3 buses respectivel These two pumps were designed to start 30 seconds and 60 seconds af ter their respective EDGs were available, however, these two timers were not synchro-nized. - The team was concerned that the licensee had not analyzed for the two pumps- starting simultaneously and producing significantly higher hydraulic stress in the Divisich 1 standby service water mechanical piping (Reference 1).

6 The_ licensee agreed to perform an analysis to address this deficienc REQUIREMEhT:

10 CFR 50, Appendix B, Criterion III, Design Control, recuires the design basis to be correctly translated into specifications, drawings, procedures, and instruction REFERENCE:

i 1.- Elesantary Diagrams ESK-SSWPO4 SSW pus 9 2A and ESK-55WP06 SSW pump 2 >

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l 7 APPEND 1X ,

Persons Contacted m

i Gulf States Utilities D. L. Andrews Director, Nuclear Training

• R. J. Backen Supervisor, QA Systems

• G. A. Bysfield Control System Supervisor

• J. W. Cook' Technical Assistant Licensing- 4

• T. C. Crouse Nanager, Administration  :

• D. Deabonne Assistant Plant Manager

• J. C. Deddens Sr. Vice President

• L. A. Englam Director, Licensing

• H. E. Epstein Consultant Observer, Devonrue

• A. L. Garrett Sr. Electrical Engineer

! *K. J. Giadrosich Supervisor, QE l . *P. D. Graham Plant Manager k *J. R. Hamilto Director, Design Engineering

• G. K. Henr Director Quality Operations

• T. L'. Hunt Sr. ISEG Engineer .

• L. G. Johnson Cajun, Manager Joint Operations G. ' A. Kinne11 Director, Quality Services J. W. Leavines Supervisor, Nuclear Safety Assurance

• J. C. Maher-

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Engineer, Licensing

• I M. Malik Supervisor QA 4

• J. F. Mead Supervisor, Electrical & Special Projects l

• J.'M. Miller Cajun, Director Joint Operations

• W. H. O' Dell Oversight, Manager-Oversight

• J. J. Pruitt Manager, Business Systems

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A. S. Soni Supervisor, EQ & Specialist

• K. E. Suhrke General Manager, Engineering and Administration

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Nuclear Regulatory Commission

• C. M. Abbate Project Manager NRR

• L. J. Callan Director, DRS, RIV W. T. Chiang Observer, AEC Taiwan E. J. Ford Senior Resident. Inspector, River Bend j

• B. K. Grimes Director, DRIS, NRR l

• W. B. Jones Project Engineer, RIV

• J. E. Konklin Section Chief, RSIB, DRIS, NRR h '

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• Denotes those attending the exit interview on June 22, 1990 at the conclusion x of the inspectio : l

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