IR 05000498/1999016

Insp Repts 50-498/99-16 & 50-499/99-16 on 990808-0918.No Violations Noted.Major Areas Inspected:Aspects of Licensee Operations,Maint,Engineering & Plant Support

ML20217C329
Person / Time
Site:	South Texas
Issue date:	10/07/1999
From:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:
Shared Package
ML20217C326	List: IR 05000498/1999016 ML20217C322
References
50-498-99-16, 50-499-99-16, NUDOCS 9910130235
Download: ML20217C329 (10)

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ENCLOSURE U.S. NUCLEAR REGULATORY COMMISSION l REGION IV l

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Docket Nos.: 50-498 l 50-499

License Nos.: NPF-76 <

NPF-80 Report No.: 50-498/99-16 ,

50-499/99-16 Licensee: STP Nuclear Operating Company Facility: South Texas Project Electric Generating Station, Units 1 and 2 Location: FM 521 - 8 miles west of Wadsworth l Wadsworth, Texas 77483 Dates: August 8 through September 18,1999 1 Inspectors: Neil F. O'Keefe, Senior Resident inspector Gilbert L. Guerra, Resident inspector Tony Gody, Senior Resident inspector, Comanche Peak Approved By: J. l. Tapia, Chief, Project Branch A l

l I i ATTACHMENT: SupplementalInformation i

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9910130235 991007 PDR ADOCK 05000498 G PDR k j

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EXECUTIVE SUMMARY (

South Texas Project Electric Generating Station, Units 1 And 2 NRC Inspection Report No. 50-498/99-16; 50-499/99-16

L ' This inspection included aspects of licensee operations, maintenance, engineering, and plant l support. The report covers a 6-week period of resident inspection.

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Operations l

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Inspectors identified two examples where operators did not determine the operability of safety-related equipment in a timely manner. Operators identified that charcoal was -

leaking out of the fuel handling building emergency ventilation exhaust filter bed, but did not properly communicate the magnitude of the spilled charcoal to the weekend duty engineering staff. As a result, a performance test to determine the impact of the spill on operability was not conducted until Monday. The filter was found to have been

operable. Similarly, operators did not properly communicate the symptoms of a failed power range nuclear instrument following a Unit 1 trip and, as a result, misdirected troubleshooting to find the problem. Specifically, operators did not indicate that cll outputs from the instrument were affected. The instrument was declared operable after troubleshooting failed to identify a problem. During the subsequent startup, the instrument failed a channel check. Operators complied with the Technical Specifications, entered the applicable limiting condition for operation, and repaired the instrument (Section 01.1 and 04.1).

• Operators pursued an equipment operability question until it was clearly resolved. A reactor coolant system hot-leg temperature detector failed low and continued to impact average hot-leg temperature calculations even after it was selected out, contrary to available documentation (Section E2.1).

• Unit 2 experienced a partialloss of offsite power event when a lightning arrestor failed on the standby transformer. Emergency equipment in trains B and C were powered by the associated standby diesel generator until offsite power was restored through the Unit 1 standby transformer. All safety systems performed as expected. The failure was apparently caused by moisture intrusion (Section O2.2).

• Unit 1 experienced a plant trip due to a material deficiency in the turbine protection system. While the licensee was unable to reproduce the problem, available indications led the licensee to the conclusion that the test switch caused a brief trip signal in Channel 2 at the same time operators were testing Channel 1. The switch was found to have been covered in dust and lint. The licensee's investigation of the trip was prompt and thorough (Section O2.3).

Maintenance

• The maintenance and surveillance activities observed were carefully performed and well controlled. High quality prejob briefings were consistently observed. Operators and technicians were very knowledgeable of their assigned tasks. A reactor coolant loop flow transmitter was recalibrated after careful deliberations to effectively balance the

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reactor trip potential with the required instrument accuracy to support reactor safet I New fuel receipts were well supported and supervised. A control rod dimensional tolerance problem was resolved by working closely with the fuel vendor (Section M1.1).

Enaineerina

. System engineering personnel provided excellent response fo: lowing the failure of a reactor coolant system hot-leg temperature detector on a weekend. The system j engineer provided a recommendation to declare the instrument inoperable, removed the i bad input, and performed a thorough evaluation of the impact of the problem on the design basis operation of the system (Section E2.1).

Plant Support

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The emergency drill effectively exercised the response capabilities of the licensee. The emergency response team's prioritization of actions was effective in combating the simulated problems. The technical support center team demonstrated initiative by brainstorming ways to mitigate a simulated release when traditional methods were ineffective (Section P4.1).

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r Report Details S_ummary of Plant Status Un;t 1 began this inspection period at 100 percent power. The unit tripped on September 12 due to a spurious turbine trip while testing the turbine protection circuit. The reactor was started up on September 13 and was returned to full power the following da Unit 2 operated at 100 percent power throughout this inspection period. On August 24, a lightning arrestor on the Standby 2 transformer faulted, causing a lockout of the south  !

switchyard bus. Offsite power was lost to Unit 2, Trains B and C, which were re-energized automatically by the associated standby diesel generators. Offsite power was restored to all safety trains within a few hours.

l 1. Operations 01 Conduct of Operations 01.1 General Comments (71707)

Using Inspection Procedure 71707, the inspectors conducted frequent reviews of ongoing plant operations. In general, the conduct of operations was safety conscious; specific events and noteworthy observations are detailed in the sections belo Operators performed well during the Unit 1 startup on September 13. The crew was given just in time simulator training on plant startup procedures in preparation for this evolution. Reactivity manipulations were carefully controlled, with good supervisory oversight and peer checking evident throughout the startup. Reactor engineering ,

personnel provided excellent support throughout the startup and early power ascensio !

Startup was interrupted when Power Range Nuclear Instrument 41 did not come on  !

scale as power entered the power range. This instrument had been reported as having failed downscale after the reactor tripped on September 12, but troubleshooting personnel did not identify anything wrong because the symptoms were not fully reported in the condition report. Specifically, operators did not indicate that the instrument failed below the zero value. The instrument was declared operable after troubleshooting failed !

to identify a problem. During the subsequent startup, the instrument failed a channel check. Operators complied with the Technical Specifications, entered the applicable limiting condition for operation, and repaired the instrument. As a result of the incomplete report, an opportunity was missed to correct a material deficiency in NI-41 i i

while the instrument was not required and a limiting condition for operation entry and startup delay could have been avoided. This was one example of where operators did not aggressively question the operability of safety-related equipment.

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02 . Operational Status of Facilities and Equipment lO2.1 ' TEnaineered Safety Feature (ESF) Systems Walked Down ' Inspection Scoos (71707)

l ' The inspectors used Inspection Procedure 71707 to walk down accessible portions of - . the following ESF systems:

e'- - Fuel Handling Building Ventilation Exhaust System' (Unit 1) .-

• ' ~ Standby Diesel Generator 21 and support systems (Unit 2)

l L Observations and Findinos i

!l Equipment operability and material condition were acceptable in all cases. The

! inspectors verified that the systems were aligned properly for the existing mode of l .~ operation. The inspectors conducted daily control board walkdowns to verify that ESF L systems were aligned as required by Technical Specification for the existing operating -

I mode, that instrumentation was operating correctly, and that power was available.

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The three ventilation exhaust trains of the. Unit 1 fuel handiing building were walked l- down, including the control board and electrical panel lineups. Equipment operability

' and material condition were acceptable in all cases. However, the inspectors noted a number of nomenclature differences in the lineups. The inspectors had also identified nomenclature errors during previous walkdowns of different plant systems. The L ' inspectors reported these errors to the control room. Condition reports for the L deficiencies were written by the licensee. The inspectors verified that the system was l

aligned properly for the existing mode of operatio ' Standby Diesel Generator 21 and support systems were observed to be in good condition. Existing minor oil leaks were wiped up and identified for maintenanc Conclusions Equipment operability and material condition of the ESF systems walkdown were acceptable in all cases. The license entered into the corrective action program any l: discrepancies identified by the inspector '

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. O2.2 Isolation of Unit 2 Standbv Transformer Due to Liahtina Arrestor Failure (71707)

An automatic actuation of ESF components occurred in Unit 2 on August 24. A loss of

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. power to Standby Buses 2G and 2H occurred when the C-phase lighting arrester failed oc the Unit 2 standby transformer. Standby Buses 2G and 2H supply power to the Train B and C ESF buses, respectively. As a result of the power loss to the Train C ESF bus, Standby Diesel Generator 23 started and loaded. Normally, the Train B ESF bus would also have been de-energized; however, Standby Diesel Generator 22 was running for a surveillance test, so Bus E2B remained energized throughout the event.

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l-3-i l The licensee reported this event pursuant to 10 CFR 50.72(b)(2). Offsite power was i l

restored to the affected ESF buses using the Unit 1 standby transformer while repairs were made to the Unit 2 standby transformer. The suspected cause of the failure was 4 an intemal fault due to moisture intrusion. The manufacturer was conducting further analysis to verify the specific failure mechanism. The inspectors determined that corrective action was appropriate and promptly tracked by the licensee's condition L reporting system.

l 02.3 Unit 1 Triooed Due to Dirtv Electrical Switch Insoection Scope (93702)

The inspectors responded to the site when the Unit 1 turbine tripped, causing a reactor trip. The plant was verified to be in a stable condition, and appropriate engineered safeguards systems were verified to have functioned as required. Control room l _ operators were interviewed and logs were reviewed to determine what testing was in

- progress and what indications of abnormal conditions were available. The following l procedures were reviewed

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OPOP07-TM-0001, Revision 4, " Main Turbine Overspeed Test" OPOP07-TM-0003, Revision 9, " Main Turbine Emergency Trip System Test" ,

i Observations and Findinas l

At 3:44 a.m. on September 12, Unit 1 tripped automatically from 100 percent power during performance of Plant Operating Procedure OPOP07-TM-0003, Revision 9," Main Turbine Emergency Trip System Test." Computer printouts indicated that the turbine protection circuit sensed a false Channel 2 trip condition at the same time operators were checking Channel 1. The reactor tripped as expected with all control rods fully

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inserting, and all plant equipment responded as expected. Operators noted that Power Range Nuclear Instrument 41 appeared to fail downscale, howeve ~ An hour prior to the trip, operators had twice unsuccessfully performed testing of the

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- mechanical overspeed trip using Plant Operating Procedure OPOP07-TM-0001, l Revision 4," Main Turbine Overspeed Test." Each time the manual trip level did not reposition hydraulically as required, so both tests were declared unsatisfactor The licensee formed an Event Review Team and conducted a thorough investigation of the trip. This investigation was able to rule out the mechanical overspeed trip mechanism as a possible cause. The cause was narrowed down to the test selector switch not properly blocking a Channel 2 trip while testing Channel 1. The licensee inspected the switch and found it covered with dust and lint. The problem could not be reproduced, so the switch was cleaned and successfully reteste The inspectors interviewed control room operators and concluded that the turbine testing had been conducted in accordance with plant procedures. The system I

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indications did not provide any warning of abnormal system response until the turbine i

tripped. The shift supervisor immediately ordered that the turbine controls be left as-is in order to facilitate a root cause investigatio The inspectors noted that this was the second Unit 1 trip caused by a material condition deficiency in the turbine protection system, and the third maintenance preventable trip, during this operating cycle. The previous trips occurred in May and June 1999 and were documented in NRC Inspection Reports 498;499/99-13 and 99-14. The inspectors verified these were properly documented and dispositioned within the Maintenance Rule program, Conclusions Unit 1 experienced its second plant trip this operating cycle due to material deficiencies in the turbine protection system. While the licensee was unable to reproduce the problem, available indications led to the conclusion that the Channel 1 test switch I caused a brief trip in Channel 2 at the same time operators were testing Channel 1. The l switch was found to have been covered in dust and lint. The licensee's investigation of {

the trip was prompt and thoroug Operator Knowledge and Performance 04.1 Charccal Adsorber Leak in Fuel Handlina Buildina Ventilation Exhaust System inspection Scope (71701)

The inspectors reviewed the event concerning a charcoal adsorber leak in the Train B fuel handling building exhaust ventilation syste Observations and Findinas

On August 19,1999, during the routine rounds, a plant operator identified that charcoal l had spilled from the charcoal bed of the fuel handling building train B exhaust filteruni l

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The condition was documented in a condition report, and duty engineering personnel were contacted to determine the significance of the problem. The operators were told that some spillage of charcoalin the adsorber filter units was common. The operability of this safety system was not further questioned until August 23, when the system engineer returned to the site. He looked at the exhaust unit and determined that the amount of charcoal that had been spilled, estimated to be 25 pounds, was more than he expected to see. The spilled charcoal was removed from the exhaust unit floor. The system engineer recommended performing a leakage test to determine whether the system was capable of performing its required function. The halide leak test found no break through in the charcoal adsorber and the system was determined to be operabl !

Visual inspections determined that the unit was losing charcoal though a loose portion of the screen mesh that held the charcoal adsorber in place. This was determined to be

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, caused by manufacturing errors on welds used to attach the screen to the filter housing.

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On August 25, the charcoal retention screen was repaired and the exhaust system was retumed to service the following da Conclusions l

Operators identified that charcoal was leaking out of the fuel handling building emergency ventilation exhaust filter bed. When the weekend duty engineering staff was contacted, the magnitude of the problem was not properly communicated. Not until the -

following Monday when the system engineer saw how much charcoal had leaked was a ,

performance test conducted to properly determine the operability of the filter. This was j a second example of where operators did not question the operability of safety-related equipment in a timely manne . Maintenance M1 Conduct of Maintenance M1.1 - Maintenance and Surveillance Observations Insoection Scone (62707. 61726)

- The inspectors observed all or portions of the following maintenance and surveillance activities. For surveillance tests, the procedures were reviewed and compared to the

' Technical Specification surveillance requirements and bases to ensure the procedures satisfied the requirements. Maintenance work was reviewed to ensure adequate work instructions were provided, the work performed was within the scope of the authorized work and was adequately documented. Work practices were also observed. In each case, the impact to equipment operability and applicable Technical Specifications actions were independently verifie Surveillances observed:

• - OPSP06-PK-0006,"4.16KV Class 1E Degraded Voltage Relay Channel Calibration-Channel 2," Revision 5, (Unit 1)

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• OPSP03-SI-0002, " Low Head Safety injection Pump 1B(28) Inservice Test," l Revision 4, (Unit 1)

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• - OPSP03-SI-0005, "High Head Safety injection Pump 1B(2B) Inservice Test,"_

Revision 5,(Unit 1)

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• OPSP03-CP-00108, " Emergency Load Sequencer Manual Test" (Unit 2)

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-6-Niaintenance activities observed:

RCS Loop 18 Flow Transmitter Calibration (Unit 1)

• New Fuel Receipt and Inspection (Unit 2)

Main steam line flow transmitter calibration (Unit 2)

b. Observations and Findinas The inspectors observed that surveillance tests were performed utilizing the proper procedures. Prejob briefings were consistently of good quality. Personnel pedorming surveillance activities had experience with the task. Equipment manipulations during tests were very well controlled by operators. Where required, independent verification techniques were properly conducted. Communications were precise and sufficiently detailed. The inspectors verified that surveillance activities satisfied Technical Specifications requirement The inspectors observed the calibration of the Reactor Coolant System Loop 1B Flow I Transmitter in Unit 1. The fact that this evolution had the potential to cause a reactor trip was clearly documented in the procedure and was discussed thoroughly in the prejob brief. The calibration was required to be performed online because the flow t transmitter was approaching the maximum allowable deviation. The technicians performing the work were very knowledgeable of the system and the calibration procedure. Communications between technicians in the various work locations were good. All personnel involved were cognizant of the reactor trip risk while performing this activity and supervisors periodically checked on the progress of the evolutio The inspectors observed the receipt process for new fuel for the upcoming Unit 2 refueling outage. The unloading, inspection, and storage of fuel was systematic, !

efficient, and performed in accordance with plant procedures. The evolution was !

adequately supported by engineering, operations, maintenance, security, and health physics personnel. The inspectors noted good coordination between the different department The licensee worked closely with the fuel vendor to resolve a potential dimensional tolerance problem with some of the new control rod assemblies. Since the vendor reported the problem after a number of assemblies had already been stored in the spent fuel pool, removing and inspecting each assembly was complicated by radiological controls. The inspectors observed that the licensee was well prepared for the control rod change out evolution. Very good radiation protection coverage was provided during the extraction of the control rod assemblies from the spent fuel pool. The inspectors noted that the reactor engineering, operations, maintenance, and health physics departments coordinated very well during this unusual evolution. By the conclusion of 4 this inspection, each of the out of tolerance control rod assemblies had been replace c. Conclusions The maintenance and surveillance activities observed were careful and controlled. High quality prejob briefings were consistently observed. Operators and technicians were

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-7- I very knowledgeable of their assigned tasks. A reactor coolant loop flow transmitter was recalibrated after careful deliberations to effectively balance the reactor trip potential with the required instrument accuracy and to support reactor operation by satisfying .

Technical Specification requirements. New fuel receipts were well supported and i supervised. A control rod dimensional tolerance problem was resolved by working closely with the fuel vendo lit. Enaineerina E2 Engineering Support of Facilities and Equipment i l

E2.1 Excellent System Enaineerina Support in Response to a Plant Operational issue Insoection Scope (37551)

The inspectors conducted a followup to an operability evaluation performed following the failure of a reactor coolant system hot leg temperature detector. The indications, operator actions, and engineering analysis were discussed with the system engineering and operations personnel. Condition Report 99-11979 and procedure OPOP04-R , Revision 9, * Failure of RCS Loop RTD Protection Channel" were reviewed.

f Observations and Findinas

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On August 20, Unit 1 control room operators identified that one of the reactor coolant system hot leg temperature detectors had failed low. Each reactor coolant loop contained three hot leg temperature detectors equally spaced around the circumference of the pipe, which were averaged to produce the hot leg temperature value. Operators responded to the failure in accordance with Procedure OPOPO4-RP-0004, Revision 9,

" Failure of RCS Loop RTD Protec, tion Channel."

After selecting out the failed indicator, operators reviewed documentation which indicated that the affected channel of the Qualified Data Processing System (ODPS)

would perform the average hot leg temperature calculation using the two remaining l good inputs. However, operators continued to question their indienc.s and the ,

operability of the channel, so they contacted the system engineer d home. The system engineer recognized that there was still a problem with the calcula an and recommended declaring the channelinoperable. The system engineer reported to the j

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site and was able to manually remove the failed input from the calculation in the ODPS computer, restoring the channel to an operable condition. He then performed an engineering evaluation of the conditio The ODoS calculation performed a power level correction to the hot leg temperature calculation. This correction factor did not properly account for data gats from failed instruments. Manually removing the erroneous input corrected the proble The engineering evaluation successfully demonstrated that the error resulting from the improper power level correction was small and within the Technical Specification allowable value under all conditions. The error would have caused the reactor

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-8-f protection system setpoints that used hot leg temperature as an input to be conservative, so that one channel would have reached its setpoint earlier than it otherwise would during a design basis transien .

The licensee concluded that the existing supse procedure should include a clarification to reflect the impact of pow comeg i error and conservatively direct declaring the channel inoperable until tne P6J iN - 1 could be remove I Conclusions j The inspectors determined that this was an example where operators continued to ,

pursue an equipment operability question untilit was clearly resolved. System j engineering personnel provided excellent response to an operational problem on a i weekend in the form of a recommendation to declare the instrument inoperable, reporting to work to remove the failed input, and performing a thorough evaluation of the impact of the problem on design basis operation of the syste IV. Plant Support P4 Staff Knowledge and Performance in Emergency Preparedness P1.1 Site Emeraency Drill Observations Insoection Scope (71750)

The inspectors observed a site emergency preparedness drill on August 1 Observations of the conduct of the drill from the simulated control room and the l'

technical support center were mad . Observations and Findinas The inspectors noted that the scenario was challenging and exercised a broad spectrum l of the site's emergency response capabilities. Participants were enthusiastic in their i roles. Site-wide accountability was completed satisfactoril In the simulated control room, operators utilized emergency operating procedures appropriately to respond to the scenario. Briefings were frequent and detaile However, the inspectors observed that, at times, the lines of responsibility between the ,

Operations Manager and the Shift Supervisor became blurred. The inspectors noted that passage through tM emergency operating procedures appeared somewhat slow, and the attempt to reduce the reactor coolant system pressure to reduca the leak rate ,

was also slo Personnel staffing the technical support center functioned as an effective tea Manager meetings and briefings were conducted frequently. Communications betweeq all responding groups was good. Priorities were established and coordinated effectively with other group r

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The technical support center set up a brainstorming session to consider ways to mitigate the simulated radioactive release from a stuck open containment ventilation valve. A number of ideas appeared to be practical and at least partially effective, including some that might be explored for possible implementatio c. Conclusions The emergency drill effectively exercised the response capabilities of the licensee. The emergency response team's prioritization of actions was effective in combating the simulated problems. The technical support center team demonstrated initiative by brainstorming ways to mitigate a simulated release when traditional methods were i ineffectiv VI. Manaaement Meetinas X1 Exit Meeting Summary l

l The inspectors presented the inspeHan results to members of licensee management on September 21,1999. Management personnel acknowledged the findings presente The inspector asked whether any materials examined during the inspection should be considered proprietary. No proprietary information was identified.

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L PARTIAL LIST OF PERSONS CONTACTED

L Licensee l

P. Arrington,' Licensing Specialist

- T. Cloninger, Vice President, Generation

S. Head, Licensing Supervisor A. Kent, Manager, Electrical / Instrumentation and Controls

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. D. Leazar, Manager, Nuclear Fuel and Analysis Department ( R. Lovell, Manager, Operations Support B. Mackenzie, Manager, Operating Experience Group M. McBumett, Director, Quality and Licensing G. Parkey, Plant General Manager J. Phelps, Manager, Unit 1 Operations P. Serra, Manager, Emergency Response

. J. Sheppard, Vice President, Engineering and Technical Services

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J. Springfield, Manager, Unit 1 instrumentation and Controls

. S. Thomas, Manager, Design Engineering Department B. Valagura, Assistant Manager, Unit 2 Operations NBC

!' None INSPECTION PROCEDURES USED IP 37551: Onsite Engineering _

IP 61726:-Surveillance Observations IP 62703: Maintenance Observations IP 71707: Plant Operations IP 71750: Plant Support Activities IP 93702: Prompt Onsite Response to Events at Power Reactors ITEMS OPENED AND CLOSED Opened Non Closed None.

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