ML18039A793

Provides Summary of Major Activities Performed at BFN During Scheduled Unit 2 Cycle 10 Refueling Outage

ML18039A793
Person / Time
Site:	Browns Ferry
Issue date:	06/01/1999
From:	Abney T TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9906090185
Download: ML18039A793 (16)

Text

CATEGORY 1 REGULAT Y INFORMATION DISTRIBUTIO ~ STEM (RIDS)

ACCESSION NBR:9906090185 DOC.DATE: 99/06/01 NOTARIZED: NO

< FACTL:50-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee DOCKET 05000260 I

AUTH.KAME AUTHOR AFFILIATION ABNEY,T.E. Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION Records Management Branch (Document Control Desk)

SUBJECT:

Provides summary of major activities performed at BFN during scheduled Unit 2 cycle 10 refueling outage.

DISTRIBUTION CODE: D030D COPIES RECEIVED:LTR ) ENCL l SIZE:

TITLE: TVA Facilities - Routine Correspondence NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL LPD2-2 LA 1 1 LPD2-2 PD 1 1 DEAGAZIO,A 1 1 INTERNAL: ACRS 1 1 E CENTER 0 1 1 OGC/HDS3 1 0 RES/DE/SSEB/SES 1 1 EXTERNAL: NOAC 1 1 NRC PDR 1 1 D

E NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE. TO HAVE YOUR NAME OR ORGANIZATION REMOVED FROM OR REDUCE THE NUMBER OF COPIES RECEIVED BY YOU OR YOUR ORGANIZATION, CONTACT DISTRIBUTION LISTS THE DOCUMENT CONTROL DESK (DCD) ON EXTENSION 415-2083 TOTAL NUMBER OF COPIES REQUIRED: LTTR 9 ENCL 8

0~ if' Tennessee Valley Authority, Post Oflice 8ox 2000, Decatur, A'labama 35609 June 1, 1999 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:

In the Matter of Docket No. 50-260 Tennessee Valley Authority BROWNS FERRY NUCLEAR PLANT (BFN) I I UN T 2 r CYCLE 1 0 REFUEL NG OUTAGE

SUMMARY

This letter provides a summary of the major activities performed at BFN during the scheduled Unit 2, Cycle 10 refueling outage. On April 11, 1999, Unit 2 was shutdown to complete Cycle 10 power operation and start the Cycle 10 refueling outage. Initial criticality for Cycle 11 operation was achieved on May 9, 1999, at 0729 hours0.00844 days <br />0.203 hours <br />0.00121 weeks <br />2.773845e-4 months <br />. Unit 2 was connected electrically to the grid (close breaker) on May 9, 1999, at 1S21 hours and achieved 100 percent uprated power, 3458 MWt, on May 15, 1999.

During the refueling outage, TVA performed numerous major modifications and maintenance activities to support continued safe and reliable operation of Unit 2. The following modifications were made to enhance nuclear safety:

~ Installed over-pressure protection for the isolated portion of the drywell floor and equipment drain sump discharge piping inside primary containment. This eliminated the

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Oi i+i U. S. Nuclear Regulatory Commission Page 2 June 1, 1999 potential for over-pressurizing this section of piping during a design basis accident.

~ Replaced AC and DC electric motors on twenty seven motor operated valves with those of higher output and revised torque switch settings. This ensures compliance with NRC Generic Letter (GL) 89-10, Safety-Related Motor-Operated Valve Testing and Surveillance requirements.

~ Enabled the Oscillation Power Range Monitoring (OPRM) system. A modification implemented during the cycle 9 refueling outage installed Power Range Neutron Monitoring system utilizing the General Electric Nuclear Measurement, Analysis, and Control (NUMAC) equipment with the OPRM trip function in the indicate only mode. Enabling the OPRM system completes BFN's commitment to the long-term solution to core stability for Unit 2.

~ Replaced the Unit 2 Reactor Core Isolation Cooling containment isolation valves which were susceptible to thermal binding. The new valves are a double-disk gate design which is not susceptible to thermal binding. The double-disk design will also provide a reduction in local leak rate test losses through the valves. Additionally, the valve stem design reduces motor operated valve testing setup time, thus enhancing ALARA and increased GL 89-10 margin.

~ Revised the documented options for the Reactor Pressure Vessel (RPV) head 0-ring gaskets. The revisions were necessary to resolve intermittent RPV head 0-ring leakage annunciation problems. The revised options included:

Use the existing 0-ring/clip (silver plating 4 to 6 mils)

Use the existing 0-ring/clip (silver plating 10 mils)

Use a spring wound Helicoflex 0-ring and retainer clip The inner RPV 0-ring was replaced with the Helicoflex spring wound O-ring.

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U. S. Nuclear Regulatory Commission Page 3 June 1, 1999 The following modification was made as part of the implementation of a 24 month fuel cycle.

~ Replaced ten of the electrical/mechanical time delay relays with solid state electronic time delay relays. Six of the relays are associated with Automatic Depressurization System initiation and seal-in function. The other four are associated with the Core Spray Pump start sequencing when normal power is unavailable.

The following modifications were made as part of BFN's program to reduce worker dose to as low as reasonably achievable (ALARA):

~ Added a chemical decontamination connection to the Reactor Water Cleanup (RWCU) suction line immediately down stream of the RWCU inboard manual isolation valve. This installation will no longer require disassembly of the manual isolation valve for decontamination of the RWCU system. Hence, this modification will enhance and expedite chemical decontamination of RWCU system.

~ Rerouted the Source Range Monitor and Intermediate Range Monitor cables such that they no longer pass through the Control Rod Drive (CRD) under vessel platform structure.

Prior to the modification these cables were routed through the platform, thus requiring these cables to be disconnected each time the CRD under vessel platform was rotated.

~ Installed a debris filter on the main condenser waterbox 2C2 circulating water inlet pipe. Operating experience indicates the accumulation of debris in the waterbox reduces thermal performance of the condenser requiring periodic cleaning. The installation of the filter provides a means of removing the debris prior to entering the waterbox, thus minimizing required manual cleaning at reactor, power thereby, reducing personnel radiation dose associated with water box cleaning.

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U. S. Nuclear Regulatory Commission Page 4 June 1, 1999 The following modifications were made to increase plant reliability:

~ Several improvements were made in the Reactor Water Recirculation control system which will improve system performance and reliability. These included:

Installation of a digital speed control system on the reactor water recirculation motor generator set. The system utilizes a proportional-integral control system to control the reactor water recirculation pump motor generator output.

Installed three new operator initiated runbacks. An upper power runback at approximately 90 percent steam flow, a mid-power runback at approximately 78.5 percent steam flow, and a 58 percent core flow runback.

Upgraded the Fisher Porter jet pump flow transmitters to Rosemount Smart Transmitters. The upgrade will improve transmitter accuracy and allow for easier calibration.

~ To support the scram reduction program the high temperature and high pressure isolation signals were removed from the Off-Gas system control logic. The high temperature and high pressure signals now provide an alarm function only.

~ Modifications to the RWCU system to improve reliability included replacing the wedge gate design containment isolation valves in the'RWCU system with a double-disc gate design. The double-disk design is not susceptible to thermal binding. Also, to facilitate Appendix J testing, permanent test connections were installed.

Implemented the following modifications to enhance the 500 Kv offsite power source and support the scram reduction program:

Replaced'he 500Kv Bus Potential Transformer (PT). The existing PTs are approaching their end of design life and could be subject to failure.

Installed surge arresters on the seven 500 Kv lines to limit incoming surges caused by lightning strikes, thereby preventing insulation breakdown of the associated switchyard circuit breakers.

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U. S. 'Nuclear Regulatory Commission Page 5 June 1, 1999 Replaced the Unit 2 Main Generator common trip relay and installed a redundant relay in parallel. The existing relay was obsolete and the redundant parallel relay will increase the system reliability.

Replaced low operating threshold auxiliary trip relays in the switchyard circuit breaker trip circuits, which are subject to spurious operation.

Modified the sudden pressure relay one out of one trip logic on the Unit 2 Main Bank and. Unit Station Service Transformers with a two out of two logic. The redundant parallel relay operation will increase system reliability and prevent spurious operation.

Approximately 1265 corrective maintenance and 850 preventative maintenance work activities were completed during the outage.

These included:

~ motor operated valve testing (29 MOVATS) on 27, valves

~ replaced approximately 25 4Kv circuit 'breakers

~ replaced 300 fuel assemblies

~ replaced the 13 main steam relief valves with valves, reset

.30 psi higher to accommodate power uprate conditions

~ replaced 17 control rod blades

~ replaced 28 control rod drive assemblies with the newer BWR Type 6 design to improve reliability

~ replaced' local power range monitors detectors Major inspection activities included:

~ reactor pressure vessel internals

~ inservice inspection of approximately 305 primary. welds, including 35 XGSCC welds

~ Flow Accelerated Corrosion, 250 grids examined

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~ approximately 67 snubber and spring can inspections

~ inservice inspection of 4 stop/control/combined intermediate valves

~ inservice inspection of 6 bypass and relief valves

~ inspected the high pressure turbine

~ inspected the main generator Several open programmatic deficiencies were resolved during

,the outage. These included closing of eight temporary alterations, six operator work arounds, 77 control room deficiencies, and 12 disabled alarms. Also, eight leak repairs were replaced with permanent repairs, four oil leaks were repaired, and fourteen catch devices were removed. This

.enabled BFN to restart Unit 2 wi;th no open programmatic deficiencies.

During the outage, TVA successfully utilized the recently installed Alternate Decay Heat Removal system to ai.'d in cooling of the Unit 2 spent fuel pool and reactor cavity.

As previously noted, BFN Unit 2 was returned to service with an uprated power output of 3458 MWt. On September 8, 1998, TVA received amendments to the Units 2 and 3 licenses allowing implementation of a 5 percent increase in thermal reactor power. This represents an increase in thermal power of 165 MWt over the original licensed output for Unit 2.

Implementation of this amendment on Unit 2 will result in an increase in electrical output of approximately 55 MWe.

The Unit 2 Cycle 10 refueling 'outage was completed in approximately 28 days. The scope of the activities completed during the outage were such that BFN Unit 2 can be operated safely and reliably for 24 months during Cycle 11 operation.

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U. S. Nuclear Regulatory Commission Page 7 June 1, 1999 There are no commitments contained 'in this letter. If you at (256) 729-2636.

have .any questions, please contact me Si cerel T. E. Abne Manager Licensi g and ndustry Aff irs cc: 'Mr. Al W. De Agazio, Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. Paul E. Frederickson, Branch Chief U.S. Nuclear Regulatory Commission Region II 61 Forsyth Street, S. W.

Suite 23T85 Atlanta, Georgia 30303 NRC Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road Athens, Alabama 35611

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