ML15232A010

Diablo Canyon Power Plant - Risk-Informed Technical Specification Completion Times (TSTF-505) License Amendment Request: August 4, 2015

ML15232A010
Person / Time
Site:	Diablo Canyon
Issue date:	08/04/2015
From:	Baradaran R, Harris B, Schrader K, Shepard M Pacific Gas & Electric Co
To:	Plant Licensing Branch IV
Lingam S
References
Download: ML15232A010 (38)

Text

DIABLO CANYON POWER PLANT Risk-Informed Technical Specification p Completion p Times (TSTF-505) License Amendment Request August 4, 2015 Ken Schrader Principal Engineer, Regulatory Services Pacific Gas & Electric Co.

kjse@pge.com Rasool Baradaran Supervisor, PRA Pacific Gas & Electric Co.

rubd@pge.com Matt Shepard Engineer, PRA Pacific Gas & Electric Co.

m6S7@pge.com Brenda Harris Manager, Nuclear Projects Pacific Gas & Electric Co.

spb8@pge.com 2

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Agenda Status of PRA Model Fire Impact on Risk-informed Completion Time (RICT) Calculations NFPA-805 Modifications St t off LAR C Status Commitments it t Draft License Condition Language I&C Questions Discussion and Staff Feedback 2

LARs PG&E submitted TSTF TSTF-505 505 LAR on November 25, 2013 NFPA 805 LAR submitted June 26 NFPA-805 26, 2013 3

Status of PRA model Current model consists of Internal Events Events, Internal Flooding, Seismic, and Fire Open peer review findings committed to be resolved at the time of TSTF-505 LAR submittal are now addressed and resolved in current PRA model Open peer review items (14 total) were identified in commitment 10 in Enc. 4 of TSTF-505 LAR 4

Fire impact on RICT calculations NFPA-805 fire model credits several future plant changes to address fire risk Modification to Address Loss of RCP Seal Cooling Planned modification to address is installation of Westinghouse Safe Shutdown Reactor Coolant Pump (RCP) seals [fall 2015 (Unit 1), spring 2016 (Unit 2) outages]

Electrical Raceway Fire Barrier System (ERFBS)

(fall 2015, spring 2016 outages) 5

Fire impact on RICT calculations NFPA 805 fire model credits several future NFPA-805 plant changes to reduce fire risk Hot Shutdown Panel modifications (spring 2016 and spring 2017 outages)

Incipient Fire Detection added within cable spreading and Solid State Protections System (SSPS) rooms (spring 2017 and spring 2018 outages) 6

Measures to Address Fire Risk Interim compensatory actions to manage fire risk prior to modifications are being p g actively y implemented p

consistent with NFPA-805 LAR commitments In addition, the following fire compensatory measures will ill b be ttaken k iin th the iinterim t i d during i use off a RICT RICT:

For the ERBFS modifications Welding and cutting will be prohibited in fire-areas fire areas pre-pre identified for each RICT For Hot Shutdown Panel modifications A continuous ti fire fi watch t h will ill b be stationed t ti d iin th the cable bl spreading rooms Operators will be briefed every shift on the manual actions that are required i d ffor remote t shutdown h td 7

Measures to Address Fire Risk In addition, the following fire compensatory measures will be taken in the interim during use of a RICT:

For Incipient Fire Detection modifications A continuous fire watch will be stationed in the cable spreading and SSPS rooms and cabinets with incipient detection credited in the PRA model used to calculate the RICT will be routinely monitored with portable incipient detectors 8

Incipient Detection Compensatory Measures PRA modeling used for the RICT program during a RICT prior to installation of modifications:

For F HotH t Shutdown Sh td P Panel l modifications difi ti PRA model will credit for the hot shutdown panel with manual actions for remote shutdown For Incipient Fire Detection modifications PRA model will only credit incipient detection for a subset of cable spreading room and SSPS room risk-significant risk significant cabinets that are routinely monitored with portable incipient detectors RICT calculations are performed crediting NFPA-805 modifications where compensatory measures are in place (consistent with configuration risk management practices ti endorsed d dbby RG 1 1.160) 160) 9

Status of TSTF-505 LAR Commitments Regulatory Commitments (10) identified in Enclosure 4 of TSTF-505 LAR Status of each commitment is summarized below Commitment 1 - Plant p procedures for changes g affecting equipment within the scope of the Configuration Risk Management Program Complete - Design Change procedure requires changes that can impact plant PRA to be evaluated by PRA group 10

Status of TSTF-505 LAR Commitments Commitment 2 - PRA model logic for pressurizer heaters Complete - PRA model (that will be used for RICT Program) updated to include logic that fails secondary heat removal when all 4 pressurizer heater banks are not functional Commitment 3 - Inclusion of shared systems/equipment syste s/equ p e t bet between ee u units ts in p procedures ocedu es for risk managed actions (RMAs)

Complete - The RICT Program procedures developed identify shared systems/equipment for RMAs 11

Status of TSTF-505 LAR Commitments Commitment 4 - PRA model for containment sump recirculation time for small LOCAs Complete - PRA model (that will be used for RICT Program) updated to include logic for increased human error failure probability for aligning cold leg recirculation when the containment fan coolers fail and containment spray is successful Commitment 5 - ECCS charging pump recovery factor when p pumpp is unavailable Complete - PRA model (that will be used for RICT Program) updated to include logic such that ECCS pump recovery factor f t isi 1.0 1 0 when h pump unavailableil bl 12

Status of TSTF-505 LAR Commitments Commitment 6 - Mission time for DGs and fuel oil transfer pumps when 230 kV offsite power source is unavailable Complete - PRA model (that will be used for RICT Program) updated to include 24-hour mission time to DGs and fuel oil transfer pumps when 230 kV offsite power source is unavailable Commitment 7 - Assume inoperability of auxiliary saltwater (ASW) train if vacuum breakers inoperable Complete - The RICT Program procedures developed require to assume inoperability of the ASW train if one or more vacuum breakers inoperable 13

Status of TSTF-505 LAR Commitments Commitment 8 - Continuous Fire watch for Cable Spreading and SSPS rooms when RICT i iin effect is ff t until til H Hott Sh Shutdown td P Panell and d Incipient Detection modifications implemented Will be proposed as license condition with additional compensatory measures described previously Commitment 9 - Prohibition of welding and cutting activities in select fire areas when RICT is in effect until ERBFS and Circuit Re-routing (Unit 2) modifications implemented Circuit Re-routing (Unit 2) modification is being replaced with same ERBFS modification as Unit 1 Will be proposed as license condition 14

Status of TSTF-505 LAR Commitments Commitment 10 - Open peer review findings and observations (14 total)

Complete - Open peer review findings and observations have been addressed and resolved in the current PRA model which will serve as the Configuration Risk Management Program (CRMP) used for RICT Program 15

Status of TSTF-505 LAR Commitments Commitment Summary 8 of 10 Regulatory Commitments are complete 2 Regulatory Commitments related to compensatory measures until NFPA-805 modifications are in place are open and will be included in proposed license conditions Risk managed TS will only be used with the approval Risk-managed of a PG&E officer an only following an appropriate readiness review to ensure all commitments are met.

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Draft License Condition (x) TSTF-505, Revision 1 Pacific P ifi Gas G and d Electric El t i shall h ll iimplement l t and d

maintain in effect all provisions of the approved Technical Specification Task Force TSTF-505, Revision 1, "Provide Risk-Informed Extended Completion Times- RITSTF Initiative 4b", as specified in the license amendment request dated November 25, 2013, supplemented by letters dated xxx, and as approved in the safety evaluation dated xxx.

xxx 17

Draft License Condition (x)(a) Transition License Conditions

1. If core damage frequency exceeds 1x10-4 / yr or large early release frequency exceeds 1x10-55 / yr, yr the licensee shall implement the Electrical Raceway Fire Barrier System (Units 1 and 2), Hot Shutdown Panel (Units 1 and 2), and Incipient Detection (Units 1 and

2) modifications described in Table S-2 of Attachment S of Enclosure 1 of Pacific Gas and Electric letter dated June 26, 2013, to complete the transition to full compliance with 10 CFR 50.48(c) prior to startup from the twentieth refueling outage for each Unit Unit. The licensee shall maintain appropriate compensatory measures in place until completion of these modifications.

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Draft License Condition (x)(a) Transition License Conditions

2. Prior to the Electrical Racewayy Fire Barrier System y

(Units 1 and 2) modifications being implemented, any time a Risk-Informed Completion Time is in effect, welding and cutting activities will be prohibited in the following fire areas :

• Unit 1, Fire Areas 3-BB. Elevation 115

• Unit 2, Fire Area 5-B-4 19

Draft License Condition (x)(a) Transition License Conditions

3. Prior to the Hot Shutdown Panel modifications being implemented, any time a Risk-Informed Completion Time is in effect, a continuous fire watch will be established in the Cable Spreading rooms.

rooms 20

Draft License Condition (x)(a) Transition License Conditions

4. Prior to the Incipient p Detection Panel modifications being implemented, any time a Risk-Informed Completion Time is in effect, a continuous fire watch will be established in the Cable Spreading and Solid State Protection rooms and cabinets with incipient detection credited in the PRA model used to calculate the h RICT will ill b be routinely i l monitored i d with i h portable bl incipient detectors.

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I&C Questions - Loss of Specified Safety Function Based on 7/16/15 call on draft follow-up I&C questions dated 7/9/15 and the 7/23 TSTF meeting meeting, the statements were made by NRC:

Determination of loss of specified p safety y function in the TSTF-505 TS Section 5.5 is not obvious when protection and control systems share components Determination of loss loss of specified safety function function needs to include consideration of a random failure in the control portion of the system (while in the TS Action)

RICT is not allowed in condition where there is a total loss of safety function function 22

I&C Questions - Loss of Specified Safety Function The basis for the position was stated to be the requirements i t off the th following f ll i iinstrumentation t t ti design requirements Institute of Electrical and Electronics Engineers (IEEE) 279-1971 Clause 4.7, Control and Protections System Interaction, Clause 4.7.3, Single Random Failure, IEEE 603 603-1991, 1991 Various Clauses GDC 21, 22, and 24.

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I&C Questions - Loss of Specified Safety Function PG&E believes the instrument design requirements are met by Design of an instrumentation system with built in redundancy d d and d di diversity it TS 3.3.1 and 3.3.2 LCO requirements for minimum number of instrument channels required to be operable, for the protection functions that include equipment that is used for both protection and control purposes TS Bases reference IEEE 279-1971 24

I&C Questions - Loss of Specified Safety Function PG&E believes the instrument design requirements are met by For parameters used for input to the Solid State P t ti System Protection S t andd a controlt l function, f ti TS Require four channels with a two-out-of-four logic to provide the required p q reliability y and redundancy, y, or Require three channels with a two-out-of-three logic and a Digital Feedwater Control System (DFWCS) with a median/signal select (MSS) feature that prevents control/protection interaction even though there are only three inputs, and 25

I&C Questions - Loss of Specified Safety Function PG&E believes the instrument design requirements are met for Diablo Canyon by For parameters used for input to the Solid State P t ti System Protection S t andd a control t l function, f ti TS For the backup Pressurizer Water Level - High Function requires q three channels with a two-out-of-three logic g Pressurizer Water Level - High Function is a backup function to other primary functions required by TS 3.3.1 Each instrument circuit can withstand both an input failure to the control system, which may then require the protection function actuation, and a single failure in the other channels, channels as stated in TS 3 3.3.1/3.3.2 3 1/3 3 2 Bases 26

I&C Questions - Loss of Specified Safety Function The following FSAR events credit a TS 3.3.1 RTS function as a primary function and Pressurizer Water Level - High Function as a backup function Uncontrolled Rod Withdrawal at Power, primary f

function ti -Power-Range P R Hi h Fl (High High-Flux (Hi h SSetting) tti )

Uncontrolled Boron Dilution At Power, primary function -

Power-Range g High-Flux g ((High g Setting)g)

Loss of External Electrical Load and/or Turbine Trip, primary function - Pressurizer Pressure - High Loss of Normal Feedwater FlowFlow, primary function - SG Low-Low Level RT and AFW Actuation Loss of Non-Emergency AC Power to the Station Auxiliaries, primary function f - turbine trip 27

I&C Questions - Loss of Specified Safety Function The need to assume a random failure in the control portion of the system, while in the TS Action, is not consistent with past NRC statements contained in Generic Letter 80 80-30 30 that states The specified time to take action, usually called the equipment out-of-service time, is a temporary relaxation of the single failure criterion which, criterion, which consistent with overall system reliability considerations, provides a limited time to fix equipment or otherwise make it OPERABLE. If equipment can be returned to OPERABLE status within the specified timetime, plant shutdown is not required.

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I&C Questions - Loss of Specified Safety Function The need to assume a random failure in the control portion of the system, while in the TS Action, is not consistent with past NRC statements contained in I

Inspection ti Manual M l Chapter Ch t 0326 S Section ti C.01 C 01 Relationship between the General Design Criteria (GDC) and the Technical Specifications that states The TSs typically allows a facility to continue to operate for a specified time with only one train of a two-train safety system operable. In that case, the GDC are met because the system design provides the necessary redundancy. The TSs permit the operation of the system with only a single train based on an evaluation of the protection provided by the unique system lineup f the for h specified ifi d period.

i d 29

I&C Questions - Loss of Specified Safety Function The requirement to assume an additional random failure in the control portion of the system, system while in the TS Action, is inconsistent with a Risk-informed approach for determination of TS Required Action Completion Times approved as part of TSTF-505.

Additional failure is not assumed for any other TSTF-505 TS Actions for equipment that has control systems (e.g., DGs)

This introduces an unnecessary complexity and human performance burden in RICT Program implementation to licensed Senior Reactor Operators (since this would not be required for any other TS Actions) 30

I&C Questions - RICT not Allowed for Total L off Safety Loss S f Function F i PRA Functional for RTS/ESFAS TSTF-505 and NEI 06-09 process allows differentiation between PRA functional and non PRA functional status for inoperable SSCs TSTF-505 TS Section 5.5 RICT Program specifically allows RICT to be used when there is a loss of safety function for emergent conditions if one or more of the trains are considered PRA functional as defined in Section 22.3.1 3 1 of NEI 06-09 06 09 Basis - Basic function as modeled in PRA will be performed 31

I&C Questions - RICT not Allowed for Total L off Safety Loss S f Function F i PRA Functional for RTS/ESFAS Applied to each functional unit in TS Tables 3.3.1-1 and 3.3.2-1 When is TS Action for two or more channels inoperable, the reactor trip or ESFAS actuation signal for each TS function must be able to be generated using remaining OPERABLE and/or PRA Functional channels, including channels h l iin tripped i d position:

ii For x of y logic (eg., 2 of 4), at least x channels must be OPERABLE or PRA Functional If one instrument channel input is in tripped position, then x-1 channels must be OPERABLE or PRA Functional 32

I&C Questions - RICT not Allowed for Total L off Safety Loss S f Function F i PRA Functional for RTS/ESFAS For individual instrument channels declared inoperable:

In most cases the inoperable instrument channel will also not be PRA-functional Examples: Instrument physically breaks, instrument cannot be calibrated, instrument reading outside expected range Examples where channel is PRA-functional are slightly non-conservative setpoint, response time slightly exceeding TS limit limit, channel in trip (previously provided in PG&E Letter dated 5/28/15) 33

I&C Questions - RICT not Allowed for Total L off Safety Loss S f Function F i PRA Functional for RTS/ESFAS NEI 06-09 06 09 requires a documented basis for PRA functionality decisions If PRA functionality cannot be documented, instrument must be assumed to not be PRA functional Licensed operators can make PRA functionality decisions within one hour to use a RICT Operators already make equipment functionality decisions on daily basis as part of tracking availability to meet the Maintenance Rule and the Mitigating Systems Performance I di Indicator Operators already need to make decisions related to equipment status within 15 minutes to make Emergency Pl classifications Plan l ifi ti 34

I&C Questions PG&E believes the follow-up draft I&C questions received 7/9/15 are not needed for a TSTF-505 application and should not be issued PG&E requests NRC TS Branch confirm if the term loss of specified safet safety ffunction nction in the TS Section 5 5.5 5

contained in TSTF-505 needs to include consideration of a random failure in the control portion of the system (while in the TS Action)

PG&E desires TSTF-505 LAR be approved in November 2015 as currently scheduled 35

I&C Questions If failure an additional instrument failure needs to be assumed,, PG&E p plans to address staff p position throughg an additional TS Section 5.5.20.f change New TS 5.5.20 f. concepts:

Applies A li tto RTS/ESFAS functions f ti for f which hi h iinstrumentation t t ti iis also l

used for control functions Proposed to require one additional OPERABLE or PRA F

Functional ti l iinstrument t t channel h l iin TS 55.5.20 5 20 Ensures single instrument channel failure while RICT is in effect does not result in loss of TS function Maintains TS function to mitigate control system transient initiated by additional instrument channel failure Alternative provided to place control system in manual control 36

I&C Questions Draft TS change to address control and protection issue 5.5.20 f. For the following Technical Specification Conditions and associated RTS and ESFAS functions for which the instrumentation provides one or more control functions, either: 1) sufficient channels for actuation of the associated RTS or ESFAS function shall be OPERABLE and/or "PRA functional" assuming g one additional single failure of an OPERABLE or "PRA Functional" channel occurs, or 2) the plant equipment which is controlled by the associated instrumentation is placed in manual control:

TS 3.3.1 Condition F for Table 3.3.1-1 3.3.1 1 Function 2a; TS 3.3.1 Condition H for Table 3.3.1-1 Functions 2b, 3, 6, 7, 8b, and 14a; TS 3.3.1 Condition Q for Table 3.3.1-1 Functions 8a and 9; TS 3.3.2 Condition G for Table 3.3.2-1 Functions 1d, 1e(1), 4d(1), and 6d(1);

and TS 3.3.2 Condition R for Table 3.3.2-1 Function 5b.

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Staff Feedback Staff Feedback 38 38