ML18039A591

Provides Summary of Major Activities Performed at BFN During Scheduled Unit 3 Cycle 8 Refueling Outage

ML18039A591
Person / Time
Site:	Browns Ferry
Issue date:	10/23/1998
From:	Abney T TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9811040111
Download: ML18039A591 (16)

Text

REGULAT Y INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9811040111 DOC.DATE: 98/10/23 NOTARIZED: NO FACIL".50-296 Browns Ferry Nuclear Power Station, Unit 3, Tennessee DOCKET 05000296 I

AUTH.NBAE, ~ , AUTHOR AFFILIATION Tennessee Valley Authority

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ABNEY,T,E'.,

RECIP.NAME RECIPIENT AFFILIATION Records. Management Branch (Document Control Desk)

SUBJECT:

Provides summary of major activities performed at BFN during scheduled Uni.'t 3 Cycle 8 refueling outage.

DISTRIBUTION CODE: D030D TITLE: TVA Facilities COPIES RECEIVED:LTR

- Routine Correspondence i ENCL 0 SIZE: A T

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-3 PD2-3-PD DEAGAZIO,A INTERNAL: ACRS OGC/HDS3 RES/DE/SSEB/SES EXTERNAL: NOAC NRC PDR D

NOTE TO ALL'RIDS" RECIPIENTS:

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

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Tennessee Valley Authority. Post Office Box 2000, Decatur, Alabama 35609 October 23, 1998 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:

In the Matter of Docket No. 50-296 Tennessee Valley Authority BROWNS FERRY NUCLEAR PLANT (BFN) UNIT 3 CYCLE 8 REFUELING OUTAGE

SUMMARY

This letter provides a summary of the major activities performed at BFN during the scheduled Unit 3 Cycle 8 refueling outage. On September 20, 1998, Unit 3 was shutdown i g to complete Cycle 8 power operation and start Cycle 8 refueling outage. Initial criticality for Cycle 9 operation was achieved on October 14, 1998, at 1809 hours0.0209 days <br />0.503 hours <br />0.00299 weeks <br />6.883245e-4 months <br />. Unit 3 was connected to the grid on October 15, 1998, at 1507 hours0.0174 days <br />0.419 hours <br />0.00249 weeks <br />5.734135e-4 months <br /> and is currently scheduled to achieve 100 percent uprated power, 3458 MNt, on October 29, 1998, following extensive post f)f2grC, outage, power ascension testing.

During the refueling outage, TVA performed numerous major modifications and maintenance activities to support continued safe and reliable operation of Unit 3.

98ii040iii PDR 981023 ADQCK 05000296 p PDR

Ol U. S. Nuclear Regulatory Commission

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Page~2 October 23, 1998 The following modifications were made to enhance nuclear safety:

~ Replaced the lower portion of the Core Spray loop 2 piping internal to the reactor vessel which had experienced intergranular stress corrosion cracking (IGSCC) with material not susceptible to IGSCC. This eliminated the need to examine this weld during subsequent refueling outages.

~ Installed over pressure protection for the isolated portion of the drywell floor and equipment drain sump discharge piping inside primary containment. This eliminated the potential for over pressurizing this section of piping during a design basis accident.

~ Replaced the low pressure ECCS suction strainers in the torus with larger high capacity stacked disk strainers.

These will provide approximately 60 times the flow area of the previous strainers. This ensures adequate strainer capacity i's maintained during a design basis accident (DBA) .

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

~ Installed advanced digital Power Range Neutron Monitoring (PRNM) system upgrade utilizing the General Electric Nuclear Measurement, Analysis, and Control (NUMAC) equipment with the Option III trip function in the indicate only mode. This installation supports TVA's long-term solution to core stability.

~ Replaced High Pressure Coolant Injection (HPCI) system steam admission valve, which was susceptible to thermal binding, with a double-disc gate valve that is not susceptible to thermal binding.

~ Replaced the Unit 3 Reactor Core Isolation Cooling containment isolation valves with a design which is not

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U. S. Nuclear Regulatory Commission

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Page~3 October 23, 1998 susceptible to thermal binding. The double-disk design will also improve in local leak rate test performance.

Additionally, the valve stem design reduces motor operated valve testing setup time, thus enhancing AU&K.

~ Installed redundant pressure transmitters and switches to electrically control the opening of the 13 Main Steam relief valves. This modification provides backup to the mechanical relief function of the valves.

~ Evaluated the Main Steam system piping beyond the Main Steam isolation valves for seismic ruggedness. As a result, modifications were performed which included adding/modifying pipe supports, rerouting of drain piping, and modifying turbine building grating. These modifications ensure integrity of the Main Steam system piping to the main condenser following a design basis seismic event.

The following modifications were made to enhance ALARA:

~ Constructed a permanent hatch in the drywell floor steel grating. This will facilitate removal and replacement of the main steam relief valves during refueling outages.

~ Installed a debris filter on main condenser waterbox 3A1 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 and reducing accumulated radiation dose..

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 qf a digital speed control system on the reactor water recirculation motor generator set. The

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U. S. Nuclear Regulatory Commission Page 4 October 23, 1998 system utilizes a proportional-integral control system to control the reactor water recirculation 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 83 percent steam flow, and a 55 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.

~ Modifications to the Reactor Water Cleanup system to improve reliability included:

Installed flow limiting orifices in the discharge piping.

This will prevent pump run-out and subsequent trip during pump starts, Revised the low flow pump trip time delay setpoint from seven (7) seconds to thirty (30) seconds.

Replaced the wedge gate design containment isolation valves 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 support the scram reduction program:

Established an alternate power supply source to various circuits in the Off-Gas system. A power sensing relay was installed that upon loss of power will automatically transfer affected circuits to an alternate power supply.

Removed Off-Gas system high temperature and high pressure isolation signals. High temperature or pressure is now an alarm function only.

41 U. S. Nuclear Regulatory Commission Page G October 23, 1998 Approximately 620 corrective maintenance and 800 preventative maintenance work activities were completed during the outage.

These included:

~ motor operated valve testing (26 MOVATS)

~ fuel sipping

~ replacement of 292 fuel assemblies including removal of leaking assemblies

~ replacement the 13 main steam relief valves with valves reset 30 psi higher to accommodate power uprate conditions

~ replacement of 8 control rod blades Major inspection activities included:

~ reactor pressure vessel internals

~ inservice inspection of approximately 211 primary welds, including, 80 IGSCC welds

~ Flow Accelerated Corrosion, 165 grids examined

~ approximately 31 snubber and spring can inspections

~ stop/control/containment isolation valves

~ bypass 'and relief valves

~ high pressure turbine Open programmatic deficiencies were resolved during the outage. These included closing of two temporary alterations, six operator work arounds, thirty-four control room deficiencies, and five disabled alarms. Also, two temporary leak repairs were replaced with permanent repairs, seventeen oil leaks were repaired, and six radwaste catch devices were removed. This enabled BFN to restart Unit 3 with no open programmatic deficiencies.

41 U. S. Nuclear Regulatory Commission Page~6 October 23, 1998 During the outage, TVA successfully utilized the recently installed Alternate Decay Heat Removal system to aid in cooling of the Unit 3 spent fuel pool and reactor cavity.

As previously noted, BFN Unit 3 was returned to service with an uprated power output of 3458 MWt. This represents an increase in thermal power of 165 MWt over the original licensed output for Unit 3. 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. Implementation of this amendment on Unit 3 will result in an increase in electrical output of approximately 55 MWe.

The Unit 3 Cycle 8 refueling outage was completed in approximately 25 days without sustaining a loss-time accident.

The, scope of the activities completed during the outage were such that BFN Unit 3 can be operated safely and reliably during Cycle 9 operation.

There are no commitments contained in this letter. If you have any questions, please contact me at (256) 729-2636.

S'ere T.E. Abney Manager of and Indus L's g ry Aff irs cc: See pag 7

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U. S. Nuclear Regulatory Commission Page~7 October 23, 1998 cc: Mr. Harold O. Christensen, 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 Mr. Albert W. De Agazio, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. L. Raghavan, Project Manager U. S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852

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