ML16342C121

Refers to 990602 Meeting with Util in Arlington,Tx Re Planned Electrical Configuration for Refueling Outage 2R9 During Midloop Operation.List of Attendees & Handouts Used by Util Encl

ML16342C121
Person / Time
Site:	Diablo Canyon
Issue date:	06/03/1999
From:	Laura Smith NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:	Rueger G PACIFIC GAS & ELECTRIC CO.
References
NUDOCS 9906080066
Download: ML16342C121 (66)

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UNITED STATES NUCLEAR REGULATORY COMMISSION REGION Iv 611'YAN PLAZA DRIVE, SUITE 400 ARLINGTON,TEXAS 76011-8064 JUN -3 I999 Gregory M. Rueger, Senior Vice President and General Manager Nuclear Power Generation Bus. Unit Pacific Gas and Electric Company Nuclear Power Generation, B32 77 Beale Street, 32nd Floor P.O. Box 770000 San Francisco, California 94177

SUBJECT:

PUBLIC MEETING OF JUNE 2, 1999, CONCERNING DIABLOCANYON

Dear Mr. Rueger:

This refers to the meeting conducted on June 2, 1999, at the Region IVoffice in Arlington, Texas, that discussed the planned electrical configuration for Refueling Outage 2R9 during midloop operation.

We appreciated the meeting and the opportunity to better understand your outage plans.

Meeting attendees are listed in Enclosure 1 to this letter. Handouts used by Pacific Gas and Electric are included as Enclosure 2.

In accordance with 10 CFR 2.790 of the NRC's "Rules of Practice," a copy of this letter willbe placed in the NRC's Public Document Room.

Should you have any questions concerning this matter, we willbe pleased to discuss them with you.

Sincerely, inda J. Smith, Chic Project Branch E Division of Reactor Projects Docket Nos.:

50-275 50-323 License Nos.: DPR-80 DPR-82

Enclosures:

1. Attendance List

2. Licensee Presentation 9906080066 99'0603 PDR ADQCK 05000275 P

PDR

Pacific Gas and Electric Company cc w/enclosures:

Dr. Richard Ferguson Energy Chair Sierra Club California 1100 lith Street, Suite 311 Sacramento, California 95814 Ms. Nancy Culver San Luis Obispo Mothers for Peace P.O. Box 164 Pismo Beach, California 93448 Chairman San Luis Obispo County Board of Supervisors Room 370 County Government Center San Luis Obispo, California 93408 Mr. Truman Burns>Mr. Robert Kinosian California Public Utilities Commission 505 Van Ness, Rm. 4102 San Francisco, California 94102 Robert R. Wellington, Esq.

Legal Counsel Diablo Canyon Independent Safety Committee 857 Cass Street, Suite D Monterey, California 93940 Mr. Steve Hsu Radiologic Health Branch State Department of Health. Services P.O. Box 942732 Sacramento, California 94234 Christopher J. Warner, Esq.

Pacific Gas and Electric Company P.O. Box 7442 San FrancisCo, California 94120 David H. Oatley, Vice President Diablo Canyon Operations and Plant Manager Diablo Canyon Nuclear Power Plant P.O. Box 3 Avila Beach, California 93424

4I

Pacific Gas and Electric Company Managing Editor Telegram-Tribune 1321 Johnson Avenue P.O. Box 112 San Luis Obispo, California 93406

Pacific Gas and Electric Company JUN -3 l999 bcc to DCD (IE45) bcc distrib. by RIV:

Regional Administrator DRP Director DRS Director Branch Chief (DRP/E)

Senior Project Inspector (DRP/E)

Branch Chief (DRP/TSS)

Resident Inspector DRS-PSB MIS System RIV File DOCUMENT NAME:.R:3 DC'tDC6-2MS.DRP To receive co ot document, Indicate In box: "C" = Co without enclosures E" = Co with enclosures "N" = No co RIV'PE:DRP/E JFMelfi;df 6/2 /99 C:DRP/E LJSmith 6/8 /99 OFFICIAL RECORD COPY

Pacific Gas and Electric Company JUN 3 I999 bcc to DCD (IE45) bcc distrib. by RIV:

Regional Administrator DRP Director DRS Director Branch Chief (DRP/E)

Senior Project Inspector (DRP/E)

Branch Chief (DRP/TSS)

Resident Inspector DRS-PSB MIS System RIV File DOCUMENT NAME: R'5 DC>DC6-2MS.DRP To receive co of document, indicate In boxt "C" = Co without enclosures "E" ~ Co with enclosures N = No co RIV:PE:DRP/E JFMelfi;df 6/Z /99 C:DRP/E LJSmith 6/5 /99 OFFICIALRECORD COPY

ENCLOSURE 1

ATTENDEES AT NRC/LICENSEE MEETING JUNE 2, 1999 NRC Steve Bloom, Project Manager, Office of Nuclear Reactor Regulation Linda Smith, Chief, Project Branch E, Division of Reactor Projects (DRP)

BillJones, Senior Reactor Analyst, Division of Reactor Safety (DRS)

David Proulx, Senior Resident Inspector, Project Branch E, DRP Larry Ricketson, Senior Radiation Specialist, DRS Pacific Gas & Electric Com an Bill Garrett, Director, Operations Mike Norem, Director, Unit 2 Outage Gene Newman, Shift Foreman, Operations Ken Bych, Supervisor, Probalistic Risk Assessment Pat Nugent, Licensing Supervisor, Regulatory Services

, Jim Becker, Manager, Operations Services

ENCLOSURE 2 LICENSEE PRESENTATION

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DIABLOCANYONPOWER PLANT 2R9 MID-LOOP June 2, 1999

Overview

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Background and schedule for 2R9 - Mike Norem

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Contingency plans Gene Newman First mid-loop Second mid-loop

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Risk assessment Ken Bych

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Overall conclusions - Mike Norem

. Background & Schedule

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First mid-loop scheduled considering major outage activities RCS clean-up Replacement of main bank transformers S/U transformer maintenance Replacement of CCP 2-2

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Second mid-loop occurrence based on outage schedule

First Mid-Loop

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Scheduled for 5.5 days after shutdown - scheduled to last for approximately 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />

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Time to boil is 13.6 minutes

~ Time to core uncovery is 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> 49 minutes

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Plant conditions One source of offsite power (S/U power) operable All ECCS pumps (except ASWP 2-2 and CCP 2-2) available.

2 DGs operable, 1 DG available (all testing for operability completed), and vital bus cross-tie capability available

Second Mid-Loop

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Scheduled for 21.5 days after shutdown scheduled to last for 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />

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Time to boil is 70 minutes

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Time to core uncovery is 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />

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Plant conditions One source of offsite power (aux power) operable All ECCS pumps available, all DGs operable, and vital bus cross-tie capability available

Preparation and Contingency Plans Overview

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Mid-loop preparation activities Communication Training

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Contingency plans RCS inventory and cooling RCS cooling /ultimate heat sink RCS make-up Electrical power Vessel water level monitoring Limitations on Unit 1 Entry and back-out criteria

I Mid-Loop Preparation Activities

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Schedule will be reviewed prior to outage and reduced inventory conditions to assure no conflicts exist

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Additional effort will be taken to inform plant staff of mid-loop activities Mid--loop communication plan will be developed Mid-loop coordinator will manage operations outside of control room

Mid-Loop Preparation Activities (continued)

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Training on mid-loop operations will be conducted prior to outage All crews will be trained Willinclude simulator scenarios with expected plant conditions and additional equipment fai ures to test contingency plans

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RCS Cooling / Ultimate Heat Sink ASMf

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One Unit 2 ASWP available during first mid-loop; both ASWPs available during second mid-loop

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Remote and manual ASW unit cross-tie valve control will be available during both mid-loops No maintenance allowed on either Unit 1 ASWPs A ladder will be staged at cross-tie in case manual operation is required

RCS Cooling / Ultimate Heat Sink Other

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All CCWPs will be available to support RHR/CFCUs

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At least 2 CFCUs available

RCS Make-Up

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Multiple flow paths will be available including RWST to RHR pumps RWST to GGPs RWST to SIPs Blender to normal make-up flowpath

Electrical Power

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DGs 2-1 and 2-3 operable and DG 2-2 available (all testing for operability completed) during first mid-loop Access to 4kVl480V rooms restricted Conduct hourly walkdown of vital bus and DG rooms No planned maintenance allowed on vital busses or DGs

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Aux power out of service due to Main Bank Transformer replacement (during first mid-loop)

Electrical Power (continued)

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S/U power will be operable (during first mid-loop)

No planned work will be allowed that could affect 230kV system at plant or in switchyard Access to switchyard will be limited Reliability of 230kV system will be verified with system operations S/U power system will be walked down prior to and once per shift during reduced inventory Barricade will be installed around S/U Transformer 2-2 to prevent interaction with Main Bank Transformer movement

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Limitations on Unit 1

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Prohibit work that could cause trip of Unit 1 No SSPS testing No Eagle 21 testing No turbine testing

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Prohibit planned work on 230kV or 500kV systems Prohibit planned work at plant, switchyard and transmission system

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No planned maintenance on instrument or service air will be allowed

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Entry and Back-Out Criteria

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Operations and Outage Management willconsider expeditiously restoring RCS level, ifone of the following conditions occurs:

Equipment prerequisites are no longer met Loss of SlU power, and DG or battery, or ifthe reliability of the 500kV system (as it relates to Unit 1) and 230kV grid is questionable from external factors Loss of an RHRP Loss of the available Unit 2 ASWP, a Unit 1 ASWP, or ASW cross-tie capability Both Unit 2 ASWPs will be available for the second mid-loop

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Eri try and Back-Out Criteria (continued)

Inability to control RCS temperature or level Loss of vital 4kV or 480V bus Weather and other external factors

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Contingency Planning Conclusions

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Scheduling of first mid-loop optimizes availability of critical equipment (DGs/ASW/RHR) while minimizing outage impact

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Loss of critical equipment has been considered and alternative/recovery actions pre-planned

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Risk of losing critical equipment minimized by controlling maintenance activities 20

Industry Shutdown Risk Insights

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Risk from shutdown is less than at power risk, but the same order of magnitude

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First mid-loop is the highest risk configuration at shutdown and typically contributes 20'lo of the total shutdown risk at PWRs Many plants strictly limit activities in their switchyards during mid-loop to assure offsite power willnot be interrupted

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ORAMInsights - DCPP

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Risk varies by orders of magnitude during an outage The first mid-loop is the highest risk configuration Short, planned duration of 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />

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99'/o of the risk at mid-loop is from loss of inventory, loss of RHRP, and loss of a bus to the running RHRP The most effective way to reduce risk further is to concentrate efforts that would minimize the probability of the three leading contributors

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Loss of off-site power contributes 0.1%

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PRA Simplified Calculation

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The risk was calculated using the frequency of a loss of decay heat removal event

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Core damage was the figure of merit. This was taken as core uncovery

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The calculation assumed that core uncovery during first mid-loop takes 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> from the initiating event.

This is a bounding calculation

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The electrical power configurations at both mid-loops were determined to be risk insignificant 23

Electrical Power Risk Results for a 20 Hour Mid-Loop

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2 Offsite power sources and 2 EDGs =

(Actual 1R9 configuration)

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230kV and 2 EDGs =

(Originally considered 2R9) 1.62E 7 4.73E '

230kV and 3 EDGs =

1.42E

'Currently planned 2R9)

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These failure rates are based on Bayesian update using both industry and actual DCPP data.

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Conclusions

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In the industry and at Diablo Canyon, the risk at mid-loop is dominated by the loss of decay heat removal, loss of inventory, and loss of a bus

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Both mid-loops have defense in depth provided for powering of required ESF equipment

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The contribution from the electrical power configuration to the risk at mid-loop is risk insignificant

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PGB E has implemented preventative actions in accordance with the intent of NUMARC 91-06 to minimize the risk increase at mid-loop from all risk sources (internal and external) 25

Overall Conclusions

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Mid-loops are well planned and optimize equipment availability and schedule

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Contingency plans have been developed and consider critical equipment and actions

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Risk of losing critical equipment minimized by limiting maintenance activities

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Probabilistic risk of the electrical configuration at mid-loop is considered risk insignificant 26