ML19323D888

TVA Pre-submittal Presentation Slides - Exigent Amendment

ML19323D888
Person / Time
Site:	Sequoyah
Issue date:	11/15/2019
From:	Tennessee Valley Authority
To:	Office of Nuclear Reactor Regulation
Buckberg P, NRR/DORL/LPL2-2, 415-1383
Shared Package
ML19323D956	List: ML19318E949 ML19318E996 ML19319C831 ML19323D756 ML19323D888
References
EPID L-2019-LLA-0239
Download: ML19323D888 (15)

Text

Sequoyah Nuclear Plant Unit 1 TS 4.2.2 Control Rod Assemblies Exigent LAR Pre-Submittal Conference Call November 15, 2019

Objectives

• Provide a description of the SQN Unit 1 H-08 Control Rod issue

• Provide overview of planned implementation actions

• Provide overview of expected License Amendment Request (LAR) content

• Discuss planned submittal date and need date

• Answer NRC questions l 2

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Background===

• Sequoyah Units 1 & 2 are Westinghouse 4-loop 3455MWt ice condenser plant designs

- Framatome HTP 17x17 fuel

- 193 Fuel assemblies, 53 control rods

• Unit 1 is currently shut down for the U1R23 refueling outage l 3

Background - H-08

• On August 27, 2019 SQN Unit 1 center control rod (core location H-8) dropped into the core while the reactor was at 100% power causing an automatic scram of the unit.

• Troubleshooting completed at the time investigated the electronic control system and no deficiencies were identified.

- The site initiated a root cause analysis which was indeterminate pending additional inspections during the fall refueling outage.

• The reactor was returned to 100% power and a second set of grippers was used to assist the normal grippers in holding the H-8 rod in position. There were no issues for the remainder of the cycle.

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Background - H-08 Troubleshooting

• During the refueling outage, remote inspections of the inside of the control rod drive mechanism were performed using robotic cameras and action was taken to replace the H-08 jack shaft.

• The inspections performed identified excessive wear on the faces of the stationary grippers along with wear marks along the interior walls of the control rod drive mechanism.

• Throughout the process, the OEM has been reviewing inspection data as well as third party reviews.

• During pre-startup testing the H-8 rod dropped into the reactor multiple times at various positions both above and below the normal operating position. The degradation in operating characteristics of the H-8 control rod was not anticipated.

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Background - Control Rod Configuration

• Total of 53 Rod Control Cluster Assemblies (RCCA)

• RCCAs are grouped into Banks:

- Four Shutdown Banks

- Four Control banks

• Rod H-08 is part of Control Bank D and located in the center of the core l 6

Background - H-08 Repairs

• Replacement of the Control Rod Drive Mechanism (CRDM) grippers is a long lead activity with first-of-a-kind elements (custom tooling, processes, crew qual. on mockups, etc.)

• Temporary modifications to utilize the H-08 movable gripper to hold the rod withdrawn were investigated but were not viable.

• Design change package being prepared for physical removal of the H-08 rod for the upcoming cycle.

l 7

Plant Changes Required

• Remove RCCA and associated drive shaft at core location H-08

• Install control rod guide tube flow restrictor on the upper internals

• Remove H-08 inputs to Rod Position Indication (RPI) system

• Remove power fuses for H-08 CRDM from the Rod Control system

• Revise Reload Safety Evaluation to include impact of control rod removal on nuclear design and safety analyses

• Revise affected procedures and design documents l 8

Planned LAR Content

• Evaluated Rod H-08 removal impacts on:

- Shutdown Margin

- Boron Concentration and Boron Worth

- Moderator Temperature Coefficient

• UFSAR Chapter 15 parameters were analyzed using the NRC-approved methods described in TS 5.6.3 and showed that limits assumed in safety analysis remain bounded.

• The Reload Safety Evaluation for the removal of H-08 validated all cycle-specific Reload Design Safety Analysis Review Checklist limits.

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Overview of Proposed Change

• Requesting proposed amendment to allow Unit 1 to operate with 52 full-length control rod assemblies for one cycle

• No methodology changes

• Proposed change to TS 4.2.2 (change bar on right):

l 10

Planned LAR Content

• Current COLR limits remain unchanged.

• No new operator actions are expected.

• No impact on the functionality, structural integrity, or thermal hydraulic configuration of the reactor vessel upper internals

- Flow restrictor installed in place of the control rod drive shaft l 11

Precedence LAR

• South Texas Project - Emergency LAR to Revise TS 5.3.2 to Allow Operation with 56 Full-Length Rod Assemblies for Unit 1 Cycle 20 (LAR -12/3/15, SE 12/11/15)

• Duke (McGuire) - Exigent LAR to Revise TS 4.2.2 Control Rod Assemblies (LAR - 9/7/18, Withdrawn 9/28/18)

- LAR was to remove Rod H-08 from the core.

- LAR was submitted as a contingency if a repair to a thermal sleeve could not be performed. Repairs were successful l 12

Differences between SQN 1 and Precedence SQN Exigent LAR McGuire STP Not a contingency Contingency Not a contingency TS 4.2.2 note in TS 4.2.2 footnote TS 4.2.2. footnote accordance with ITS format Framatome analysis In-house analysis Westinghouse analysis No thimble plug Thimble plug Thimble plug Control bank RCCA Control bank RCCA Shutdown bank RCCA l 13

Proposed Schedule for Submittal and Requested Approval

• Sequoyah plans to submit the exigent LAR on November 16

• Plant is currently progressing to Mode 6 to perform initial field work

• Plant is remaining in Mode 6 pending approval and implementation of the design change

• Request NRC review 7 days after submittal l 14

Closing and Questions l 15