ML18033B717

Responds to NRC 910403 Ltr Re Violations Noted in Insp Repts 50-259/91-07,50-260/91-07 & 50-296/91-07 on 910222-0313. Corrective Actions:Troubleshooting Action Plan Implemented to Identify & Correct Noise Spiking on Channel B SRM

ML18033B717
Person / Time
Site:	Browns Ferry
Issue date:	05/24/1991
From:	Medford M TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9105310004
Download: ML18033B717 (12)

Text

P'HICl3 1 REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS) tACCESSION NBR:9105310004 DOC.DATE: 91/05/24 NOTARIZED: NO PACIL:50-259 Browns Ferry Nuclear Power Station, Unit 1, Tennessee 50-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee 50-296 Browns Ferry Nuclear Power Station, Unit 3, Tennessee AUTH. NAME MEDFORD,M.O.

RECIP.NAME AUTHOR AFFILIATION Tennessee Valley Authority RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

DOCKET 05000259 05000260 05000296

SUBJECT:

Responds to,NRC 910403 ltr re violations noted in insp repts 296/91-07 on 910222-0313.

-50-.259/91-07,=50-260/91-07 &

Corrective actions:troubleshooting action plan implemented to identify & correcr. noise spiking on channel B SRM.

DISTRIBUTION CODE: IE01D COPIES RECEIVED:LTR / ENCL l SIZE:

TITLE: General (50 Dkt)-Insp Rept/Notice of Violation Response 05000259 r)

NOTES:1 Copy each to: B.Wilson,S. BLACK 1 Copy each to: S.Black,B.WILSON 05000260 ~

1 Copy each to: S. Black,B.WILSON 05000296 ~

REC1PIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL HEBDON,F 1 1 ROSS,T. 1 1 WILLIAMS,J. 1 1 TERNAL: ACRS 2 2 AEOD 1 1 AEOD/DEIIB 1 1 AEOD/TPAB 1 1 DEDRO 1 1 NRR MORISSEAU,D 1 1 NRR SHANKMAN,S 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PEPB9D 1 1 NRR/DRIS/DIR 1 1 NRR/DST/DIR 8E2 1 1 NRR/PMAS/ILRB12 1 1 NUDOCS-ABSTRACT 1 1 1 1 OGC/HDS3 1 1 REG FI E 02 1 1 RGN2 FILE 01 1 1 EXTERNAL: EG&G/BRYCE,J.H. 1 1 NRC PDR 1 1 NSIC 1 1 NOTES: 5 5 TOTAL NUMBER OF COPIES REQUIRED: LTTR 30 ENCL 30

Tennessee Valley Authority, 1 101 Market Street. Chattanooga, Tennessee 37a02 Mark O. Medford Vice President, Nuclear Assurance. Ltcensrng and Fuels MAY R4 'f991 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:

In the Matter of Docket Nos. 50-259 Tennessee Valley Authority 50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN) NRC INSPECTION REPORT 50-259, 260, 296/91-07 REPLY TO NOTICE OF VIOLATION (NOV)

This letter provides TVA's response to the NOV transmitted by B. A. Wilson's letter to Dan A. Nauman, dated April 3, 1991. An extension of the response time to May 24, 1991, was granted by P. S. Kellogg, Section Chief, Inspection Program, TVA Projects on May 17, 1991. The NOV cites TVA with a violation for failure to follow procedures during refueling activities.

TVA agrees that a violation occurred. Pursuant, to 10 CFR 2.201, Enclosure 1 to this letter provides TVA's reply to the NOV. A listing of the commitments made in this letter is provided on Enclosure 2.

If you have any questions regarding this response, please telephone Patrick P. Carier at (205) 729-3570.

Very truly yours, TENNESSEE VALLEY AUTHORITY M. 0. Medford Enclosures cc: See page 2 9105310004 910524 PDR ADOCK 05000259 0

MAY 24 1991'c U.S. Nuclear Regulatory Commission (Enclosures):

Ms. S. C. Black, Deputy Director Project Directorate 11-4 U.S. Nuclear Regulatory Commission One white Flint, North 11555 Rockville Pike, Rockville, Maryland 20852 NRC Resident Inspector Browns Ferry Nuclear Plant Route 12, Box 637 Athens, Alabama 35609-2000 Mr. Thierry M. Ross, Project Manager U.S. Nuclear Regulatory Commission One white Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. B. A. Milson, Project Chief U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NM, Suite 2900 Atlanta, Georgia 30323

Enclosure 1 Tennessee Valley Authority (TVA)

Browns Ferry Nuclear Plant (BFN)

Reply to Hotice of Violation (HOV)

Inspection Report Humber 50-259 260 296/91-07 The NOV cites TVA with a failure to comply with procedural requirements to immediately halt refueling activities on February 21, 1991, as a result of an unexplained increase in fuel loading chamber (FLC) readings during the loading of the first fuel assembly into the core. TVA agrees that a violation occurred. The decision to initiate refueling activities was inconsistent with both the procedural requirements and TVA standards of performance. TVA has set high standards of excellence for quality and safety in plant operations.

This decision is not considered to be in accordance with these high standards of excellence.

VIOLATIOH "During the Nuclear Regulatory Commission (NRC) inspection conducted on February 22 Harch 13, 1991, a violation of HRC requirements was identified.

The violation involved failure to follow procedures for refueling. In accordance with the "General Statement of Policy and Procedure for NRC Enforcement Actions," 10 CFR Part 2, Appendix C (1990), the violation is listed below:

Technical Specification 6.8.1.1 requires that written procedures shall be established, implemented, and maintained covering the applicable procedures in Appendix A of Regulatory Guide 1.33, Revision 2, February 1978. Appendix A of Regulatory Guide 1.33 includes procedures for refueling.

Refueling Operations Procedure, 2-GOI-100-3, implements this requirement for refueling. Procedure step 3.1 under Precautions and Limitations requires that refueling shall be immediately halted upon occurrence of (procedure step 3.1.1) unexplained or abnormal increase in source range monitors (SRHs) or fuel loading chambers (FLCs) readings, or (procedure step 3.1.3), loss of neutron monitoring with less that two SRMs/FLCs operable and responding with one in the fuel handling quadrant and one in an adjacent quadrant.

0 Page 2 of 4 Contrary to the above, neither of the requirements were met in that refueling was not immediately halted when an unexplained increase in FLC B reading occurred on February 21, 1991, prior to and during loading of the first fuel assembly into its designated core location. High and high-high count rate alarms were received prior to fuel handling on February 21, 1991, which resulted in work request C042091. Spiking of the period meter and ramping of the count rate meter occurred while the fuel grapple or refueling bridge were moved prior to and during placement of the first fuel assembly into the core.

This is a Severity Level IV Violation (Supplement 1) applicable to all three units."

TVA's REPLY

l. Admission of Violation TVA agrees that a violation occurred.

2. Reason for the Violation This violation was caused by an inappropriate personnel action.

On the morning of February 21, 1991, Unit 2 was in the refuel mode.

The reactor vessel cavity was filled with water and the fuel pool gates were removed. Final preparations were in progress for the initiation of fuel handling. At 0155 hours0.00179 days <br />0.0431 hours <br />2.562831e-4 weeks <br />5.89775e-5 months <br />, the SRM operability Surveillance Instruction (SI) had been successfully completed for SRM channels A and B. The SRH channel B detector had been replaced with a FLC. FLCs are sensitive neutron detectors that provide additional neutron detection capability while the neutron flux level is low.

This SI requires FLCs and/or neutron sources to be moved within the reactor vessel, and historically, noise spikes have not been an unusual phenomenon during its performance.

At 0250 hours0.00289 days <br />0.0694 hours <br />4.133598e-4 weeks <br />9.5125e-5 months <br />, a noise spike occurred which resulted in a Hi alarm being received at the channel B SRM panel. A work request was initiated and Instrument Maintenance personnel investigated the cause of the spiking. Ho problems were found, however, only visual troubleshooting was performed. Operations personnel investigated plant conditions which could have resulted in spiking (electrical interference from alarms, equipment operation, welding, grinding, etc.), and no such activities were identified. Subsequently, channel B FLC readings stabilized and no additional indications of spiking were observed. The failure to completely troubleshoot the cause of the spiking was contrary to procedural requirements and policy for the conduct of operations at BFN.

Page 3 of 4 Prior to the event, communications between the Refuel Floor Assistant Shift Operations Supervisor (ASOS) and the Shift Operations Supervisor (SOS) were not effective in helping the SOS determine a correlation between refuel bridge movements and the noise spikes. During the period between 0250 hours0.00289 days <br />0.0694 hours <br />4.133598e-4 weeks <br />9.5125e-5 months <br /> and 0550 hours0.00637 days <br />0.153 hours <br />9.093915e-4 weeks <br />2.09275e-4 months <br />, the refuel bridge was not moved because of a blown fuse. This information was not communicated to the SOS. lf the SOS had known that the bridge was not moved during this time, it may have allowed a correlation between bridge motion and noise spikes to have been recognized. Additionally, the characterization of the noise spikes which was communicated to the SOS was incomplete. Operations personnel monitoring the SRM panel did not provide the SOS with information pertaining to the magnitude of the spikes.

The procedural guidance in place at the time prescribed actions to be taken in response to erratic SRM behavior specific to unexpected neutron subcritical multiplication. No guidance was provided for responding to erratic SRM behavior unrelated to subcritical multiplication.

At 0600 hours0.00694 days <br />0.167 hours <br />9.920635e-4 weeks <br />2.283e-4 months <br />, a noise spike caused an additional Hi alarm at the channel B SRM panel. The refueling bridge was over the reactor cavity and the main hoist grapple was being manipulated. Plant conditions were evaluated for circumstances which could have caused the noise spike, and none were identified. The alarm was reset and the channel B SRM readings stabilized to previous levels. Subsequent bridge movements did not result in noise spikes; therefore, a correlation between bridge movements and noise spikes was not established. Again, the troubleshooting performed was incomplete.

At 0704 hours0.00815 days <br />0.196 hours <br />0.00116 weeks <br />2.67872e-4 months <br />, as the first fuel assembly was being lowered into the core, a noise spike occurred on the channel B SRM and a Hi-Hi alarm was received on the SRM panel (no Hi-Hi alarms had been received prior to this time). Fuel movement was halted by the SOS with the fuel assembly located approximately one foot above the top core plate. The SOS determined that the safest course of action was to place the fuel assembly in the reactor vessel. As the fuel bundle was released a second Hi-Hi alarm on the channel B SRM was received, and at 0724 hours0.00838 days <br />0.201 hours <br />0.0012 weeks <br />2.75482e-4 months <br /> the channel was declared inoperable.

TVA concludes that the decision to load fuel was inappropriate and not in accordance with the existing procedural guidance. The principal contributing factors were incomplete follow-up of an abnormal condition and inadequate written and verbal communications. The failure to adequately determine the cause of the earlier noise spiking was due to incomplete troubleshooting. The procedural guidance only addressed actions to be taken in response to unexpected subcritical multiplicat,ion. Ineffective communications between the Refuel Floor ASOS and the SOS also prevented the SOS from making a fully informed decision to initiate fuel loading activities.

Page 4 of 4 Corrective Ste s Taken and Results Achieved A comprehensive troubleshooting action plan was implemented to identify and correct the noise spiking on the channel B SRM. On February 21, 1991, a cable connector and cable shield were found to be disconnected and were repaired. On February 22, 1991, a channel calibration and functional test was performed satisfactorily; however, noise spikes were still present on the channel. Many of these spikes appeared to be coincident with refuel bridge electrical functions.

Further troubleshooting resulted in replacement of the channel preampliEier, adjustment of the ground straps on the refuel bridge, and finally the replacement of the FLC. AEter the FLC was replaced some minimal noise spikes were observed coincident with refuel bridge electrical functions; otherwise the channel was stable. On February 23, 1991, the channel B SRM was declared operable after the completion of surveillance testing, and fuel loading was resumed.

Actions were also taken to improve the procedure guidance for responding to erratic SRM/FLC behavior. The BFN procedures governing refueling operations have been revised to augment the existing guidance with precautions requiring fuel loading to be stopped whenever unexplained detector behavior is observed (independent of a relationship to subcritical multiplication). These procedure changes also require the SOS and reactor engineer to concur that reactivity changes can be adequately monitored prior to the resumption of fuel loading.

This event has been reviewed with four of the licensed operator crews scheduled for duty during and following the approach to crit,icality for Unit 2 restart.

Corrective Ste s Which Will Be Taken This event will be reviewed with Operations personnel. Emphasis will be placed on the need to ensure complete information (e.g. numerical values of changes, plant status) is transmitted during communications, This review will also address TVA's expectations for the conduct of work activities. It will stress the necessity for complete follow-up of abnormal conditions and their resolution prior to commencing/resuming work activities as defined in Plant Manager' Instruction PHI-12.12, Conduct of Operations. This review will be completed by August 30, 1991.

Operator team training lesson plans will be reviewed to ensure emphasis is placed on the importance of communicating complete information and revised as needed. This review and necessary revisions will be completed by August 30, 1991.

Date When Full C lienee Will Be Achieved TVA will be in full compliance by August 30, 1991.

0703k

Enclosure 2 Listing of Commitments The source range monitor spike event will be reviewed with Operations personnel. Emphasis will be placed on the need to ensure complete information (e.g. numerical values of changes, plant status) is transmitted during, communications. This review will also address TVA's expectations for the conduct of work activities. It will stress the necessity for complete follow-up of abnormal conditions and their xesolution prior to commencing/resuming work activities as defined in Plant Manager's Instruction 12.12, Conduct of Operations. This review will be completed by August 30, 1991.

Operator team training lesson plans will be reviewed to ensure emphasis is placed on the importance of communicating complete information and revised as needed. This review and necessax'y revisions will be completed by August 30, 1991.