IR 05000346/1993023

Insp Rept 50-346/93-23 on 931115-19.No Violations Noted. Major Areas Inspected:Insp of Compliance W/Sbo Rule

ML20059A312
Person / Time
Site:	Davis Besse
Issue date:	12/22/1993
From:	Gardner R, Neisler J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
Shared Package
ML20059A310	List: IR 05000346/1993023 ML20059A307
References
50-346-93-23, NUDOCS 9312300102
Download: ML20059A312 (10)

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U. S. NUCLEAR REGULATORY COMMISSION

REGION III

Report No. 50-346/93023(DRS)

Docket No. 50-346 License No. NPF-3 Licensee: Centerior Energy c/o Toledo Edison Company 300 Madison Avenue Toledo, OH 43652 Facility Name: Davis-Besse Nuclear Power Station Inspection At: Oak Harbor, OH 43449 Inspection Conducted: November 15-19, 1993 Inspection Team: J. H. Neisler, Team Leader D. S. Butler, Reactor Inspector R. Mendez, Reactor Inspector C. Osterholtz, . Operator Examiner F. Burrows, Electrical Engineer, NRR J. Vitella, Observer, PUC0 f

o/j Approved By:( G. H.[e/jn/ Neislerf, Team Leader /}-10-F} Date Approved By: Nb *N ' 2 O R. H. Gardner, Chief, Plant .IE e Systems Section Inspection Summary inspection on November 15-19. 1993 (Report No. 50-346/93023(DRS)) . .

. Areas inspected: Routine, announced inspection of compliance with the SB0

= rule, 10 CFR 50.63 per Tl 2500/120 (SIMS Number MPA-A-22) .

.Results: No violations or deviations were identified.

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9312300102 931222 PDR ADOCK 05000346 i G PDR

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F DETAILS Temporary Instruction (TI) 2500/120 (SIMS Number MPA-A-22)

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Concern about SB0 arose because of the accumulated experience regarding the reliability of AC power supplies. Many operating plants have experienced a total loss of offsite power, and more occurrences are expected in the futur In almost every one of these loss of offsite power events, the onsite emergency power supply has been available immediately to supply the power needed by vital safety equipment. However, in some instances, one of the redundant emergency AC power supplies has been unavailable. In a few cases, there has been a complete loss of AC power. In addition, there have been numerous instances when emergency diesel generators (EDGs) have failed to start and run in response to tests conducted at operating plant The rest:ts of Unresolved Safety Issue, A-44, " Evaluation of Station Blackout Accidents at Nuclear Power Plants," indicated, that for one of the two plants ,

evaluited, an SB0 event could be an important contributor to the total risk from nuclear power plant accidents. Although this total risk was found to be

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small, the relative importance of SB0 events was established. This finding and the accumulated diesel generator failure experience increased the concern about 5B In a Commission proceeding addressing SB0, it was determined that the issue -

should be analyzed to identify preventive or mitigative measures that can or should be taken. The purpose of this inspection was to verify the adequacy of plant programs, procedures, training, equipment and systems, and supporting documentation for implementing the SB0 Rule,10 CFR 50.63 and to document the results of this review in this inspection repor . Inspection Results Conino Duration Analysis The SB0 Rule required that systems provide sufficient capacity and capability to ensure that the core is cooled and appropriate containment integrity is maintained in the event of an SB0 for the specified duration. The specified duration was calculated based on factors such as the offsite power design characteristics, emergency AC power supply configuration, and EDG. reliabilit A minimum acceptable 580 duration of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> was calculated for Davis-Bess ,

The licensee provided the proposed four hour SB0 duration in a letter to the ~

NRC dated April 17, 1989. The NRC reviewed the proposed SB0 duration and agreed with the licensee's evaluation as documented in a NRC safety ' evaluation ,

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During the inspection, the team verified selected factors which were used to >

determine the SB0 duration and reviewed plant documentation to verify that these characteristics were appropriate. The team also reviewed EDG reliability data up to 1993. The reliability value was 0.96 for the last 100 j valid start and load run demands for the EDGs, 1.0 for the last 50 demands for i

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i the EDGs, and 1.0 for the last- 20 demands for the EDG Based on a review of l the diesel reliability data, the team determined that the selection of a 0.9 EDG reliability target value was appropriat *

The team concluded that the 580 duration of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, .that had been calculated in accordance with NUMARC 87-00, Revision 1, " Guidelines and Technical Bases for Humarc Initiatives," was acceptabl '

The licensee chose to install an alternate AC (AAC) power: source which met the criteria specified in NUMARC 97-00, Appendix 8. The AAC power source can be i available within tr. minutes of the onset of the SB0 and has sufficient '

capacity and capapility to operate systems necessary for coping with a SB0 for the required SB0 duration of four hours to bring and maintain the plant in a- _!

safe shutdown conditio .2 Station Battery Caoacity I

The AAC source can provide power to cae division of the onsite AC distribution '

system within 10 minutes. The AC divisions powered by the AAC w'il provide power through the divisional battery charger to the battery and DC slfste Since the battery is without a charge for only 10 minutes, battery izin calculations for the coping duration were not necessary. The design basis load profile for the batteries (LOOP /LOCA plus loss of AC to the battery charger for one hour) shows the batteries to be adequate for the 10 minute 1 duratio :i Severe Weather Procedures  :

The team verified that the severe weather orocedures provided adequate I guidance to prepare the site for ensu b9 severe weather. The licensee issued ,

sevare weather guidelines in Emergency Plan Procedure No. EP-4100 and Procedure No. No. HS-EP-01500, " Tornado and Emergency Classification Procedure." In the event that offsite power was lost, Toledo Edison load ,

dispatchers hate been instructed to give the highest priority to restoring power to Davis-Bess jt

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The team concluded the severe weather procedures were consistent with the guidance provided in NUMARC 87-0 # EDG Reliability Proaram The team verified that the EDG reliability program target levels were consistent with the plant category and coping duration selected. Surveillance testing of .the EDGs is performed periodically in accordance with the Technical Specification The reliability program monitors each start and load run of .

the EDGs and SB0 DG and trends the reliability data.. Unavailability and key j components' parameters are trended and trigger values. are factored into the -l acceptance criteria / corrective action decision process associated with the i reliability progra Program oversight is. provided by the systems' engineering - !

manager with the system engineers responsible for the implementation. Various '

reports on DG performance and reliability are provided to the station -

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l The team concluded that the EDG and SB0 DG reliability program was detailed,- .

appeared to be functioning properly, and was consistent with the guidance o RG 1.155, Sections 1.,1 and 1.2, and tiUMARC 87-00, Appendix D- ,

! Alternate AC (AAC) Power Source j

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The team concluded that the station blackout diesel generator (SBODG) had j adequate capacity to power the SB0 loads, had a reliability o.f greater than j 0.95, could power SB0 loads within 10 minutes, and met all' the requirements of .

NUMARC 87-00, Appendix The licensee installed a new, : tlf contained SB00'G . fThe unit has a continuous -

rating of 2865kW or 3580kVa at a 0.8 power factor and can be connected to .

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either safety train. The SB0DG's rating is larger than the emergency diesel i generators (2600kW). The team considered the SBODC acceptabl !

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The SB0 building is located inside the protected area near the plant and was designed to meet the State of Ohio uniform building' code. The SB0DG and its air start system, control systems, switchgear, fuel oil and battery system ,

were located in this buildin Besides the diesel engine's keep warm systems, !

the building was provided with an adequate heating and ventilation syste Post modification test No. DB-PF-10117, Revision 0, " Station Blackout Load Test," demonstrated that the SBODG could energize the SB0 busses in 3 minutes and 50 seconds from the onset of SBO. Following bus energization, representative SB0 loads were started and the equivalent largest load was tripped to verify the diesel's load rejection capability. All of the ,

performance testing was completed satisfactorily. The team considered the ;

SBODG start and load characteristics acceptabl ;

NUMARC 87-00 requires the AAC power source to be started and brought to :

operating conditions that are consistent with its function as an AAC source at intervals not greater than 3 months. In addition, a timed start and rated '

load capability test is required each refueling outage. Periodic test No. DB-SC-04271, "SBODG Nonthly Test," performs a rated load capacity test that is j similar to monthly EDG surveillance testing. The team considered monthly ,

SB0DG testing acceptabl .

The refueling outage test, DB-SC-04274, is currently a draft procedure. .This "

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is considered to be an inspection followup item (50-346/93023-01(DRS)) to review the approved procedur >

t 2. Instrumentation Preventive Maintenance (PM) j

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The licensee has incorporated SB0 equipment protective relays, time delay relays, meter indication, gauges and bistable tripping devices in their PH progra The PM intervals were commensurate with the device type and  !

functio The team considered this acceptabl l

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2.5. AAC Ground Detection System The team noted that the DC-ground detection system for the AAC diesel generator system was not sufficiently sensitive to detect high and moderate resistance grounds in the AAC control circuits. The detector did not have audible alarms or meters indicating the presence of a ground on the syste Ground indication is determined by comparing the relative brightness between two lights. Multiple high resistance grounds cannot be detected. Multiple -

grounds in the DC control circuits can cause DC circuits to become inoperabl The licensee's calculations indicated that a ground of 1600 ohms or less could be detected. However, the manufacturer states that the detector ground setpoint could not be quantified and the detector could only detect soliii (essentially zero resistance) grounds. Since the detector may not detect high resistance or multiple grounds and the grounds could impact the operation of-affected control circuits, the operators may not be'able to start the diesel generato The licensee is investigating alternative methods to datect the presence of

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grounds in the.DC control system . AAC Battery /Charaer Capacity The design basis for the AAC battery is to provide sufficient power to start-the AAC diesel generator and connect it to the plant's 4.16kV system within one hour of the onset of SB0. The licensee developed a load profile for the AAC battery based on the SB0 scenario. The results of the calculation I

indicated that a battery with at least a 40.20 ampere-hour (Ah) capacity rating was required. The installed AAC battery has a 60 Ah rating which ,

exceeds the capacity required for the design basis scenario and is considered l acceptable.

l The battery charger was supplied with the battery as a package from the AAC ;

l' diesel generator supplier. The normal load on the battery charger is 0.985A due to battery float charge and miscellaneous small loads. The charger has a 2 maximum output of 20A which is considered adequat '

The licensee was in the process of developing battery maintenance procedures and determining the maintenance interval. This is considered an inspection followup item (50-346/93023-02(DRS)) for the NRC to review the SBODG battery maintenance progra . Station Blackout Modification 89-0109 The team identified that. post modification test no. DB-PF-10117 did not verify auxiliary transformer lockout relay 86/XDF8, and SBV0DG phase overcurrent relay 51V-1/DG3_would trip the SBV0DG. These trips, along with SB0 generator differential na engine overspeed, remain unbypassed when the control- room

" ELECT PROTECT-MODE SELECT" switch is in the emergency positio In response, the licensee provided the team a primary injection checkout procedure that was used during installation testing. The team concluded the

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. installation test provided sufficient testing overlap to demonstrate the j

identified relays would trip the SB0DG as per design. However, the team

considers this a testing weakness for not including these relays in the post l

-modification test. Installation testing verifies individual component 1

. function and as-built plant configuration. This type of. testing does not -

establish.the actual operating scenario' that verifies the system response. . In

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this case, these trips remained in effect during all modes' of operation such ~

that overlap in testing could be verifie l The team also noted that draft periodic test No. DB-SC-04274, "SBODG _ Dead-Bus ,

Load Test," which closely.followed the post modification test, included onl ;

.the generator differential and engine overspeed trips. The potential exists '

for a quality related procedure to inadequately test the SB0DG unbypassed ;

trip ;

In response, the licensee indicated they would develop a procedure to test the ,

other unbypassed trips. This is considered an inspection followup item l (50-346/93023-03(DRS)).

2.5. Drawino Control The team identified several discrepancies between electrical wiring caanection . i drawings and the as-built configuration in the AAC diesel generator control panels. .A-total of seven terminations were incorrectly represented on as-built drawings WEDID-1010A, Sheets 1 and 2, and WEDID 1033, Sheet The licensee verified' that the terminations were correctly installed and ' initiated

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i corrective action to effect the necessary drawing changes. The team concluded 1 that the seven drawing discrepancies did not affect the operability of the.AAC

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diesel generato .5. Electrical Cable Installation 'I The team reviewed documentation relative to AAC source electrical cable installation. The team noted the electrical contractor had exceeded the cable manufacturer's specified pull tension for the 3 conductor,. 500 mcm cables between the SB0 generator and the Davis-Besse plant. The licensee contractor -j had used incorrect values in their calculations for determining the cable '

pulling force. Using information provided by the licensee and vendor information, the team's calculations indicated ~that the pulling force applied to the cable was more than twice the maximum allowable force for this installation. A high potential (hi-pot) test was performed on the cable subsequent to installatio The hi-pot test p'rocedure did not contain an ;

acceptance criteria for determining the acceptability of the cable. ' Data l sheets did not list all hi-pot voltages used on. Phase ;

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The team recognized that the cable was not a Class IE cable. However, the team concluded that the licensee exercised poor control over contractor activities including review of initial calculations, permitting use of procedures without adequate acceptance criteria and accepting incomplete test data from the contracto .6 Comoressed Air Systems The team verified by review of plant drawings and operating procedures that the plant does not rely on air operated equipment during the first ten minutes of an SB0 event. The licensee has provided an emergency instrument air compressor that automatically starts on low instrument air header pressure immediately upon the energization of the SB0 (D2) bus. This air compressor has the capacity to maintain normal instrument air system header pressur The team concluded that there was reasonable assurance that no SB0 functions were dependent on compressed air, and that normal instrument air header pressure would be automatically restored when energizing the SB0-(D2) bu .7 Containment Isolation The team concluded that the licensee had correctly identified the containment isolation valves that are required to function during an SBO. Verification of containment isolation is accomplished by completion of the containment isolation checklist in the emergency operating procedure .8 Condensate Storace Caoacity

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The team verified that Davis-Besse had adequate condensate storage capacity to cope with an SBO. Condensate inventory calculations indicated that approximately 62,800 gallons of condensate are required for decay heat removal for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The plant Technical Specifications minimum permissible condensate storage tank level is 250,000 gallons of water which exceeds the required quantity for coping with a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> station blackou .9 AAC Preventive Maintenance The team reviewed the AAC preventive maintenance program including work planning and review, corrective action processes, root cause analyses, procurement, spare parts availability, functional' testing maintenance, surveillance and personnel qualifications. The team concluded that the licensee had implemented or was developing adequate preventive. maintenance procedures and-program . AAC Battery Maintenance / Surveillance The AAC battery was installed in 199 Electrolyte levels and cell voltages -

were checked-and recorded in June 1992 and November-1993. Interconnections resistance measurements and a-service test-has been performe The licensee stated that- the battery maintenance and surveillance- procedure will follow the guidance in the last revision of IEEE 1106, " Recommended-Practice for Maintenance, Testing and Replacement of Nickel-Cadmium Storage

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Batteries for. Generating Stations and Substations." The licensee's procedures-for maintaining the battery were being developed and were not ready for the~ ,

team's review. This is an inspection followup item (50-346/93023-04(DRS)). j 2. SB0 Circuit Breaker Maintenance l

The team's review of maintenance on the SB0 4kV and 480V circuit breakers :

noted that the preventive maintenance procedure for these circuits had not i been fully developed and implemented. This is an inspection followup-item to I

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be accomplished when procedures have been developed and implemented'  !

(50-346/93023-05(DRS)). ,

2.10 Procedures and Proarams .

The team verified thr(ugh the review of SB0 procedures, QA audit and surveillance reports, observation of a simulated SB0 scenario, walkdown' of various SB0 equipment and interviews with operators and trainers'that SB0 procedures had been ar,equately developed and implemented and that the -i operators were sufficiently trained to respond to an SB '

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The licensee demonstrated the adequacy of the SB0 ' procedure by performing a simulated station blackout event on the plant simulator. The team observed .

one staff crew and one plant operations shift crew perform the dynamic '

simulator scenarios that required different flow paths through the emergency and abnormal procedure Both crews successfully recognized the SB0. event, started the AAC diesel generator, energized the 580 bus (D2) and restored AC-power to the appropriate vital bus in less than ten minutes from the onset of *

the SB The team concluded that the emergency and abnormal procedures were i structured such that the mitigation of an SB0 is ensured and that the t operators were adequately trained to respond to an SB l

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The team verified and concluded that procedures for restoring offsite and onsite AC power to vital buses, containment isolation verification, l.imiting reactor coolant inventory a loss and reactor trip verification were adequately- >

developed and implemente SB0 training is included in the operator qualification and requalification !

training programs. Quality of the SB0 training was demonstrated by-the good

. performance of the operators during the simulator demonstratio l

' Inspection Followuo Items  ;

Inspection followup items are matters.which have been discussed with the I licensee, which will be reviewed further by the inspector (s), and which-involve some action on the part of the NRC or licensee or both. Inspection !

followup items disclosed during the inspection are discussed in_ Sections :

and 2.9 of this repor '

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L Exit Meetina

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The team met with licensee representatives (denoted in Appendix A) at.the' :

l conclusion of the inspection on November 19, 1993.. The team summarized the !

scope and findings of the inspection activities. The licensee acknowledged i the inspection findings. The team also discussed the likely informational ;

content of the inspection report with regard to documents or processes reviewed by the ' inspector during the inspection. The licensee did not ;

identify any such document / processes as proprietar ;

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APPENDIX A

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PERSONNEL CONTACTED

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Toledo Edison Company G. Gibbs, Director, Engineering S. Jain, Director, Nuclear Services J. Wood, Manager, Davis-Besse Plant i N. Peterson, Licensing Engineer ,

P. Jacobsen, Supervisor, Design Electrical Engineering .

S. Byrne, Manager, Plant Operations W. O'Connor, Manager, Regulatory Affairs i P. Smith, Supervisor, Compliance J. Rogers, Manager, Maintenance R. Zyduck, Manager, Nuclear Engineering "

J. Holden, Manager, Design Engineering P. Roelant, Senior Engineer G. McIntyre, Supervisor, E/C Systems S. Saunders, Engineer, Nuclear A. Stallard, Senior Operations Advisor B.l Gallatin, Test Engineer G. Warner, Senior Electric Design Engineer

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U. S. Nuclear Reaulatory Commission J. Shine, Resident Inspector t R. Gardner, Chief, Plant Systems Section, Division of Reactor Safety Others a

J. Vitellas, Ohio Public Utilities Commission

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