ML16106A323

Browns Ferry, Units 1, 2, and 3 - Response to NRC Request for Additional Information Related to License Amendment Request for Adding New Specifications to Technical Specification 3.3.8.3 (BFN-TS-486) - Letter 1

ML16106A323
Person / Time
Site:	Browns Ferry
Issue date:	04/15/2016
From:	Shea J W Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CNL-16-066, TAC MF6738, TAC MF6739, TAC MF6740
Download: ML16106A323 (11)

Text

1101 Market Street, Chattanooga, Tennessee 37402

CNL-16-066

April 15, 2016

10 CFR 50.90

ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Units 1, 2, and 3 Renewed Facility Operating License Nos. DPR-33, DPR-52, and DPR-68 NRC Docket Nos. 50-259, 50-260, and 50-296

Subject:

Response to NRC Request for Additional Information Related to License Amendment Request for Adding New Specifications to Technical Specification 3.3.8.3 (BFN-TS-486) (CAC Nos. MF6738, MF6739, and MF6740) - Letter 1

References:

1. Letter from TVA to NRC, CNL-15-073, "Application to Modify the Browns Ferry Nuclear Plant, Units 1, and 2 Technical Specifications by Adding New Specification TS 3.3.8.3, 'Emergency Core Cooling System Preferred Pump Logic, Common Accident Signal (CAS) Logic, and Unit Priority Re-Trip Logic,' and Unit 3 TS by adding New Specification TS 3.3.8.3, 'Common Accident Signal (CAS) Logic, and Unit Priority Re-Trip Logic,' (BFN-TS-486)," dated September 16, 2015 (ML15260B125)

2. Letter from NRC to TVA, "Browns Ferry Nuclear Plant, Units 1, 2, and 3 - Request for Additional Information Related to License Amendment Request for Adding New Specifications to Technical Specification 3.3.8.3 (CAC Nos. MF6738, MF6739, and MF6740)," dated March 21, 2016 (ML16074A126)

By letter dated September 16, 2015 (Reference 1), Tennessee Valley Authority (TVA) submitted a license amendment request (LAR) for Browns Ferry Nuclear Plant (BFN), Units 1, 2, and 3, to revise the BFN, Units 1 and 2, Technical Specifications (TS) by adding a new specification governing the safety func tions for the Emergency Core Cooling System (ECCS) Preferred Pump Logic, Common Accident Signal Logic, and the Unit Priority Re-Trip Logic. In addition, the LAR relocated the BFN, Unit 3 requirements for Common Accident Signal Logic and Unit Priority Re-trip Logic to a new specification governing the safety functions for the Common Accident Signal Logic, and the Unit Priority Re-Trip Logic for consistency with the changes to the BFN, Units 1 and 2 TS.

CNL-16-066 Enclosure 1, Page 1 of 6 ENCLOSURE 1 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT UNITS 1, 2, AND 3 TVA Responses to NRC Request for Additional Information: Set 1 Probabilistic Risk Assessment (PRA) Licensing Branch (APLA) RAI 1

The LAR does not appear to clearly indicate the proposed risk-informed TS changes.

Please summarize which TS Limiting Conditions of Operation (LCOs) and Conditions or Surveillance Requirements, are being proposed as risk-informed TS changes and have been evaluated using PRA for this LAR.

TVA Response The Completion Time of proposed Browns Ferry Nuclear Plant (BFN), Units 1 and 2 Technical Specification (TS) 3.3.8.3, Condition A for one or more inoperable divisions of Emergency Core Cooling System (ECCS) Preferred Pump Logic (PPL) is the only change being proposed as a risk-informed change. The following information is provided to clarify the proposed changes contained in Enclosure, Section 4.3 Technical Analysis of the TVA License Amendment Request (LAR) dated September 16, 2015.

Browns Ferry Nuclear Plant, Units 1 and 2 ECCS PPL The ECCS PPL receives input signals from TS Table 3.3.5.1-1, Core Spray (CS)

Functions 1a, 1b, and 1c and Low Pressure Coolant Injection (LPCI) Functions 2a, 2b, and 2c.

In the event one or more required channels specified in TS Table 3.3.5.1-1 is found to be inoperable, current TS 3.3.5.1, Condition A requires immediately entering the Condition referenced in Table 3.3.5.1-1 for the affected channel(s). The two Conditions specified by TS Table 3.3.5.1-1 associated with CS Functions 1a, 1b, and 1c and LPCI Functions 2a, 2b, and 2c are Conditions B and C.

TS Table 3.3.5.1-1 references Condition B for CS Functions 1.a and 1.b, and LPCI Functions 2.a and 2.b during operation in Modes 1, 2, and 3, and CS Functions 1.a and 1.c and LPCI Functions 2.a and 2.c during operation in Modes 4 and 5 when the associated subsystem(s) are required to be operable. TS Table 3.3.5.1-1 references Condition C for CS Function 1.c and LPCI Function 2.c during operation in Modes 1, 2, and 3.

TS 3.3.5.1, Condition B requires placing the channel in trip within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> in Modes 4 and 5, when the associated subsystem(s) are required to be operable. In addition, TS 3.3.5.1, Condition B requires declaring the supported ECCS feature(s) inoperable when the redundant feature ECCS initiation capability is inoperable within one hour from discovery of loss of initiation capability for features in both divisions.

CNL-16-066 Enclosure 1, Page 2 of 6 TS 3.3.5.1, Condition C requires restoring the channel to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. In addition, TS 3.3.5.1, Condition C requires declaring the supported ECCS feature(s) inoperable when the redundant feature ECCS initiation capability is inoperable within one hour from discovery of loss of initiation capability for features in both divisions.

In the event the Required Action and associated Completion Time of TS 3.3.5.1, Conditions B and C are not met, TS 3.3.5.1, Condition H requires immediately declaring the associated support ECCS feature(s) inoperable. Therefore, Required Action of TS 3.3.5.1, Condition H requires entry into the appropriate Conditions of TS 3.5.1, during operation in Modes 1, 2, and 3, or TS 3.5.2, during operation in

Modes 4 and 5.

With one low pressure ECCS injection/spray subsystem inoperable during operation in Modes 1, 2, and 3, TS 3.5.1, Condition A requires restoring the affected ECCS injection/spray subsystem to operable status within seven days. With two or more low pressure ECCS injection/spray subsystem inoperable during operation in

Modes 1, 2, and 3, TS 3.5.1, Condition H requires immediate entry into Limiting Condition for Operation (LCO) 3.0.3.

With one required low pressure ECCS injection/spray subsystem inoperable during operation in Modes 4 and 5, except with the spent fuel storage pool gates removed

and water level 22 feet over the top of the reactor pressure vessel flange, TS 3.5.2, Condition A requires restoring the required ECCS injection/spray subsystem to operable status within four hours.

With two required ECCS injection/spray subsystems inoperable during operation in Modes 4 and 5, except with the spent fuel storage pool gates removed and water

level 22 feet over the top of the reactor pressure vessel flange, TS 3.5.2, Condition C requires that action be initiated immediately to suspend operations that could result in draining the reactor vessel and restoring one ECCS injection/spray subsystem to operable status within four hours.

The proposed TS 3.3.8.3, Condition A allows one or more required ECCS PPL divisions to be inoperable for seven days before restoration to operable status. This is a less restrictive requirement than currently specified by TS 3.3.5.3, Conditions B and C. Therefore, the proposed TS 3.3.8.3, Condition A Completion Time is considered risk-informed.

During operation in Modes 1, 2, and 3, proposed TS 3.3.8.3, Condition D requires placing the unit in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in Mode 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />, if the Required Action and associated Completion Time of TS 3.3.8.3, Condition A are not met. This is a more restrictive requirement than currently required by TS 3.3.5.3, Condition H. Therefore this change is not risk-informed.

During operation in Modes 4 and 5 with the opposite unit in Modes 1, 2, or 3, proposed TS 3.3.8.3, Condition E requires immediately declaring the associated ECCS components inoperable, if the Required Action and associated Completion Time of TS 3.3.8.3, Condition A are not met. TVA letter dated September 16, 2015, Enclosure, Section 4.3 provides the justification for why the requirement for the opposite unit to be in Modes 1, 2, or 3 is added to the Condition. This change is not

risk-informed.

CNL-16-066 Enclosure 1, Page 3 of 6 The proposed SR 3.3.8.3.1 is consistent with the existing Logic System Functional Test required currently specified by SR 3.3.5.1.6. The six-hour allowance in the proposed SR 3.3.8.3.1, Note 1 is also consistent with the current Note 2 allowance of the TS 3.3.5.1 Surveillance Requirements table. The allowance to not require actuation of breakers in the opposite unit provided in the proposed SR 3.3.8.3.1, Note 2 is necessary to preclude unnecessary challenges to an operating unit.

Actuation of the associated breakers on the opposite unit will be performed by the opposite unit's Logic System Functional Test. Therefore, the changes incorporating SR 3.3.8.3.1, the six-hour allowance, and the allowance to not require actuation of breakers in the opposite unit are not risk-informed changes.

BFN Units 1, 2, and 3 Common Accident Signal (CAS) and Unit Priority Re-Trip Logics The proposed changes relocating the requirements for CAS from the current Units 1, 2, and 3, TS 3.8.1 to the proposed Units 1, 2, and 3, TS 3.3.8.3 are administrative in that no technical changes are made to the LCO, Mode of Applicability, Conditions, Required Actions and Completion Times. Therefore, the relocation of the CAS requirements is not a risk-informed change.

The proposed changes providing explicit requirements for the Unit Priority Re-Trip Logic are not risk informed. The proposed changes are administrative in that the Unit Priority Re-Trip Logic is currently described in the TS 3.8.1 Bases Background discussion in the discussion of the CAS Signal Logic. The proposed change proposes the same Conditions, Required Actions, and Completion Times for the Unit Priority Re-Trip Logic as those currently specified in TS 3.8.1 for the CAS Logic.

The proposed SR 3.3.8.3.1 is consistent with the existing Logic System Functional Test required currently specified by SR 3.3.5.1.6. The six-hour allowance in the proposed SR 3.3.8.3.1 is also consistent with the current Note 2 allowance of the TS 3.3.5.1 Surveillance Requirements table. Therefore, the change incorporating SR 3.3.8.3.1 and the six-hour allowance is not a risk-informed change.

In summary, the only change that is considered to be risk-informed is the Completion Time of proposed BFN, Units 1 and 2 Technical Specification (TS) 3.3.8.3, Condition A for one or more inoperable divisions of ECCS PPL. This proposed Completion Time has been

evaluated using PRA for this LAR.

APLA RAI 2 Explain the equipment impact of the PPL unavailabilities allowed by the proposed TS change and how it is modeled in the internal events PRA. Include an explanation of same unit and opposite unit equipment impacts. Indicate whether the PRA evaluates single and multiple unit risk for the PPL unavailabilities and is included in the PRA results.

TVA Response A single event is used to model unavailability of PPL and this basic event is used for both BFN Units 1 and 2. The ECCS PPL unavailability basic event is included under the PPL logic for Low Pressure Injection (LPI), i.e., Unit 1 Residual Heat Removal (RHR) pumps 1A and 1C, and Unit 1 CS pumps 1A and 1C, or Unit 2 RHR pumps 1B and 1D, and Unit 2 CS

pumps 2B and 2D. Similarly, a single event is used for ECCS PPL failure on demand (i.e., the conservative approach taken did not include divisional ECCS PPL relays, or unavailability events). In addition, a spurious ECCS PPL event is included in the model. The logic is set up such that the pumps assigned divisionally for ECCS PPL (i.e., Unit 1 CNL-16-066 Enclosure 1, Page 4 of 6 RHR pumps 1A and 1C and Unit 1 CS pumps 1A and 1C, or Unit 2 RHR pumps 2B and 2D and Unit 2 CS pumps 2B and 2D) are assumed to be failed if ECCS PPL is unavailable and simultaneous loss of coolant accident (LOCA) signals occur in both units. The remaining RHR or CS pumps in a unit (not ECCS PPL) are assumed to fail if simultaneous signals occur. The logic is applicable in fast acting scenarios (e.g., Large LOCA, Medium LOCA, Small LOCA without high pressure injection (HPI), Break Outside Containment). The PRA Model does not include "bus separation" given ECCS PPL failure. However, in the remaining scenarios, the board and loads can be realigned because core damage would take over 36 minutes (i.e., without any injection), or many hours if steam driven HPI systems are available. The impact of single and multiple unit initiators is evaluated for Unit 1 and Unit 2. The following table lists the pumps of interest in the PRA ECCS PPL logic, and impact of ECCS PPL logic on Unit 1 and Unit 2.

Pump Shutdown Board (SDBD) Unit 1 Unit 2 Notes RHR 1A 4kV SDBD A PPL RHR 1C 4kV SDBD B PPL RHR 1B 4kV SDBD C Not PPL PRA assumes failure of this pump if simultaneous LOCA signals occur RHR 1D 4kV SDBD D Not PPL PRA assumes failure of this pump if simultaneous LOCA signals occur CS 1A 4kV SDBD A PPL CS 1C 4kV SDBD B PPL CS 1B 4kV SDBD C Not PPL PRA assumes failure of this pump if simultaneous LOCA signals occur CS 1D 4kV SDBD D Not PPL PRA assumes failure of this pump if simultaneous LOCA signals occur RHR 2A 4kV SDBD A Not PPL PRA assumes failure of this pump if simultaneous LOCA signals occur RHR 2C 4kV SDBD B Not PPL PRA assumes failure of this pump if simultaneous LOCA signals occur RHR 2B 4kV SDBD C PPL RHR 2D 4kV SDBD D PPL CS 2A 4kV SDBD A Not PPL PRA assumes failure of this pump if simultaneous LOCA signals occur CS 2C 4kV SDBD B Not PPL PRA assumes failure of this pump if simultaneous LOCA signals occur CS 2B 4kV SDBD C PPL CS 2D 4kV SDBD D PPL APLA RAI 3 Explain whether PPL unavailabilities could result in no low pressure injection (as well as no high pressure injection) following a LOCA (to include feedwater and steamline break). If so, explain the plant's defense-in-depth for the LOCA scenario.

TVA Response HPI systems are not affected by ECCS PPL, but may not be available if the reactor pressure vessel depressurizes quickly because the HPI systems use steam driven pumps. Initiator impact is modeled under the HPI system logic t hat would automatically fail HPI. The PRA ECCS PPL logic model is included under RHR or CS logic as described in the TVA response to APLA-RAI-2. ECCS PPL unavailability could result in failure of Low Pressure Injection (CS and RHR) during a fast acting LOCA scenario if a coincident spurious or actual accident signal occurs in the other unit. For instance, if ECCS PPL is unavailable and a CNL-16-066 Enclosure 1, Page 5 of 6 LOCA occurs in a unit combined with a simultaneous LOCA signal (real or spurious) in the opposite unit, then the PRA models assume all RHR and CS pumps are not available to mitigate core damage in these fast acting scenarios. These scenarios are assumed to result in core damage because no additional systems are credited (e.g., sequence LLOCA-005).

APLA RAI 8 Prior to the proposed TS change, there was no explicit LCO for UPRTL [Unit Priority Re-Trip Logic]. The LAR states that the LCO for UPRTL is implicitly required by the TS 3.8.1 Condition D, which applied to the CAS. In the proposed TS change for Unit 1 and Unit 2, LCO 3.3.8.3, Condition B applies to CAS and LCO 3.3.8.3, Condition C applies to UPRTL.

For Unit 3, LCO 3.3.8.3, Condition A applies to CAS and LCO 3.3.8.3, Condition B applies to UPRTL. These TS LCO Conditions for the UPRTL have a 7 day completion time and are new proposed changes. If these UPRTL TS LC Os are proposed as risk-informed changes, then include the associated risk for Units 1, 2, and 3 in the results reported in the LAR as part of APLA-RAI-14.

TVA Response The proposed changes providing explicit requirements for the Unit Priority Re-Trip Logic are not risk informed. The proposed changes are considered administrative in that the Unit Priority Re-Trip Logic is currently described in the TS 3.8.1 Bases Background discussion in the discussion of the CAS Signal Logic. The proposed change proposes the same Conditions, Required Actions, and Completion Times for the Unit Priority Re-Trip Logic as those currently specified in TS 3.8.1 for the CAS Logic.

APLA RAI 9 Note 1 to the proposed SR 3.3.8.3.1 states that, "when a division is placed in an inoperable status solely for performance of a surveillance, entry into associated Conditions and Required Actions may be delayed for up to six hours provided the associated redundant division is OPERABLE." The proposed TS Bases state that the "PRA demonstrated that the 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> testing allowance does not significantly reduce the probability that the ECCS Preferred Pump, CAS and Unit Priority Re-trip Logics will initiate when necessary." If the LAR is justifying the 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> testing allowance time as a risk-informed TS change, then provide the PRA justification for the 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> testing allowance for the ECCS PPL, CAS, and UPRTL. Provide the LAR risk results impact as part of APLA-RAI-14.

TVA Response The six-hour allowance in the proposed SR 3.3.8.3.1 is not a risk-informed change. As stated in the current TS 3.3.5.1 Bases, the allowance is based on the reliability analysis (i.e., NEDC-30936-P-A, "BWR Owners' Group Technical Specification Improvement Analyses for ECCS Actuation Instrumentation, Part 2," December 1988) assumption of the average time required to perform channel surveillance. That analysis demonstrated that the six-hour testing allowance does not significantly reduce the probability that the ECCS will initiate

when necessary. The six-hour allowance was incorporated into the PRA when the ECCS PPL was first modeled. However, the six-hour allowance is not changed by the License Amendment Request. The Logic System Functional Test for ECCS PPL, CAS Logic and Unit Priority Re-Trip Logic is currently required by TS 3.3.5.1, SR 3.3.5.1.6. The current Surveillance Requirements Table of TS 3.3.5.1 is modified by Note 2, which states, "When a channel is placed in an inoperable status solely for performance of required Surveillances, entry into associated Conditions and Required Actions may be delayed as follows: (a) for up to six hours for Functions 3.c and 3.f; and (b) for up to six hours for CNL-16-066 Enclosure 1, Page 6 of 6 Functions other than 3.c and 3.f provided the associated Function or the redundant Function maintains ECCS initiation capability." ECCS PPL receives input signals from TS Table 3.3.5.1-1, CS Functions 1a, 1b, and 1c and LPCI Functions 2a, 2b, and 2c. CAS Logic receives input from TS Table 3.3.5.1-1, CS Functions 1a, 1b, and 1c. Unit Priority Re-Trip Logic receives input from TS Table 3.3.5.1-1, LPCI Functions 2a, 2b, and 2c. Therefore, the six-hour allowance currently applies to the ECCS PPL, CAS Logic and Unit Priority Re-Trip Logic and is not a change from the current requirements.

CNL-16-066 Enclosure 2, Page 1 of 3 ENCLOSURE 2 Tennessee Valley Authority Browns Ferry Nuclear Plant, Units 1, 2, and 3 Summary of BFN Request for Additional Information Response Dates

CNL-16-066 Enclosure 2, Page 2 of 3 Request for Additional Information (RAI)

Question Number Due Date (NRC Letter dated March 21, 2016)

Revised Due Dates Actual Date of Response Electrical Engineering Branch (EEEB) EEEB RAI 1 April 15, 2016 May 11, 2016 Future Letter EEEB RAI 2 April 15, 2016 May 11, 2016 Future Letter EEEB RAI 3 April 15, 2016 May 11, 2016 Future Letter EEEB RAI 4 April 15, 2016 May 11, 2016 Future Letter Instrumentation and Controls Branch (EICB) EICB RAI 1 April 15, 2016 May 11, 2016 Future Letter EICB RAI 2 April 15, 2016 May 11, 2016 Future Letter EICB RAI 3 April 15, 2016 June 16, 2016 Future Letter Probabilistic Risk Assessment Branch (PRA) Licensing Branch (APLA)

APLA-RAI-1 April 15, 2016 No change CNL-16-066, April 15, 2016 APLA-RAI-2 April 15, 2016 No change CNL-16-066, April 15, 2016 APLA-RAI-3 April 15, 2016 No change CNL-16-066, April 15, 2016 APLA-RAI-4 May 25, 2016 May 11, 2016 Future Letter APLA-RAI-5 May 25, 2016 June 16, 2016 Future Letter APLA-RAI-6i April 15, 2016 May 11, 2016 Future Letter APLA-RAI-6ii April 15, 2016 May 11, 2016 Future Letter APLA-RAI-6iii April 15, 2016 May 11, 2016 Future Letter APLA-RAI-6iv May 25, 2016 June 16, 2016 Future Letter APLA-RAI-7 April 15, 2016 May 11, 2016 Future Letter APLA-RAI-8 April 15, 2016 No change CNL-16-066, April 15, 2016 CNL-16-066 Enclosure 2, Page 3 of 3 Request for Additional Information (RAI)

Question Number Due Date (NRC Letter dated March 21, 2016)

Revised Due Dates Actual Date of Response APLA-RAI-9 April 15, 2016 No change CNL-16-066, April 15, 2016 APLA-RAI-10 April 29, 2016 No change Future Letter APLA-RAI-11 April 29, 2016 No change Future Letter APLA-RAI-12 May 25, 2016 No change Future Letter APLA-RAI-13a May 25, 2016 June 16, 2016 Future Letter APLA-RAI-13b May 25, 2016 No change Future Letter APLA-RAI-13b May 25, 2016 No change Future Letter APLA-RAI-14 May 25, 2016 June 16, 2016 Future Letter APLA-RAI-15 May 25, 2016 No change Future Letter APLA-RAI-16 April 29, 2016 No change Future Letter Summary April 15, 2016: APLA RAI 1, 2, 3, 8, 9 April 29, 2016: APLA RAI 10, 11, 16 May 11, 2016: APLA RAI 4, 6i, 6ii, 6iii, 7; EEEB RAI 1, 2, 3, 4; EICB RAI 1, 2 May 25, 2016: APLA RAI 12, 13b, 13c, 15 June 16, 2016: APLA RAI 5, 6iv,13a, 14; EICB RAI 3