ML16217A161

Browns Ferry, Units 1, 2, and 3 - Response to Request for Additional Information Regarding Proposed Technical Specifications (TS) Change TS-505 License Amendments - Extended Power Uprate (EPU) - Supplement 29

ML16217A161
Person / Time
Site:	Browns Ferry
Issue date:	08/03/2016
From:	Shea J W Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CAC MF6741, CAC MF6742, CAC MF6743, CNL-16-129
Download: ML16217A161 (152)

Text

In RAI No. APLA-RAI 09, dated April 14, 2016, the NRG staff requested the licensee to explain how several human error probabilities (HEPs) were quantified for both the extended power uprate (EPU) and CL TP in order to confirm the reasonableness of these calculations and to understand why the increase in some HEPs are much larger than others. In response to APLA-RAI 09 dated April 27, 2016, the licensee discussed the quantification of these HEPs for both the EPU and CLTP. The response stated for human failure event (HFE) HFFAOASD_RCIC that "the dependency levels are higher [a medium dependency was assigned for the CL TP case and a high dependency was assigned for the EPU case] for the abandonment action due to the longer execution time and stress levels." It is not clear why the HEP for HFFAOASD_RCIC is increased by only a factor of 1.15 at the CL TP level to the EPU level, while HEP for HFEs HFA_0002RPV_LVL and HFA_OHCllNIT30 are increased by much larger factors (i.e., a factor of 2.76 and 2.04, respectively). The staff observed that the execution analysis in the Electric Power Research Institute (EPRI) human reliability analysis (HRA) calculation sheet for HFFAOASD_RCIC includes 9 procedure steps, with recovery considered only in procedure step 1. Procedure steps 2 through 9, which are considered "high" stress, did not credit recovery because of an assumption made for the HEP of each step (i.e., "it is better to use item Ref. 8a [that is a HEP value of 2.?E-04] even though it is for normal stress and then not credit a recovery step"). Not crediting recovery in procedure steps 2 through 9 for HFFAOASD_RCIC causes the HEPs associated with these steps to be the same between the CL TP and EPU. This results in a smaller increase in total HEP for HFFAOASD_RCIC, between the CLTP and EPU cases, than that had recovery been credited, potentially leading to underestimating the change in risk. When recovery is credited in each procedure step, the EPU HEP for HFFAOASD_RCIC could be 3 times larger (not 1.15 times larger as currently indicated by Attachment 44 of the EPU LAR) than that for the CL TP case. This issue may also apply to other HFEs considered in the EPU risk evaluation, such as those HFEs identified in Part 1 below. The staff requests the licensee to address the following: a. Provide the detailed HRA calculation sheets (e.g., as generated by the EPRI HRA calculator) for the following HFEs for both the CL TP and EPU cases:

• HFA_0003PMP START ("Operator fails to restart RFW [reactor feedwater] after Level 8 trip")

• HFA_0071 L8RESTART ("Operator fails to restart RCIC [reactor core isolation cooling] after Level 8 trip")

• HFA_0073L8RESTART ("Operator fails to restart HPCI [high pressure coolant injection] after Level 8 trip")

• HFFA_ 1 SHV0760540_35 ("Local action - close 1-SHV-076-0540 (2- and 3- for Units 2 and 3) within 35 minutes")

• HFFA0268480CRSTIE ("Failure to transfer deenergized 480V board to alternate supply (fire)")

• HFFAOASD_RCIC ("Operator fails to start RCIC") b. For each internal events and fire HFE considered in the EPU risk evaluation (i.e., HFEs in Tables 4-4 and 4-9 of Attachment 44 of the EPU LAR) that have a different dependency level between the CL TP and EPU cases, confirm that recovery is appropriately represented in the HFE's cognitive analysis and execution analysis such that the total HEP is realistically estimated for the CL TP and EPU cases. If it is not, then update the associated HEPs for the CL TP and EPU cases to appropriately address recovery, and provide the updated HEPs along with an explanation of how they were changed (provide sufficient detail and numerical values to understand the basis for the updated HEPs).

c. If changes were made to the HEPs in Part b of this RAI, then provide: 1. Updated risk results in Sections 5.1 ("Internal Event Results"), 5.2 ("Fire Risk Results"), and 5.6 ("Total Risk") in Attachment 44 of the EPU LAR, as applicable. If Regulatory Guide (RG) 1.17 4 risk acceptance guidelines are exceeded, then please provide a detailed justification to support the conclusion that no "special circumst.ances" are created by the proposed EPU, include a discussion of which metrics are exceeded and the conservatisms in the analysis and the risk significance of these conservatisms.

2. Updated risk results in Table 8-1 ("Summary Risk Results for the Combined Sensitivity Study") of the response to APLA-RAI 08, dated April 27, 2016. If RG 1.17 4 risk acceptance guidelines are exceeded, then provide a detailed justification to support the conclusion that no "special circumstances" are created by the proposed EPU, include a discussion of which metrics are exceeded and the conservatisms in the analysis and the risk significance of these conservatisms.

HFA_0003PMP_START-CLTP, OPERATOR FAILS TO RESTART RFW AFTER LEVEL 8 TRIP

Notes/Assumptions: Notes/Assumptions: Workload would be expected to be relatively high due to attempts to restore some source of HPI. Action primarily triggered based on monitoring RPV level, which is indicated by a variety of displays and meters.

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Notes/Assumptions: Since a transition among three procedures might be required, and the unit supervisor would be following multiple paths through the EOIs, this is treated as a case of multiple procedures. Placekeeping aids are used in the form of a bracket in which the unit supervisor initials the steps as they are reached.Notes/Assumptions:

Notes/Assumptions: Logic is straightforward, and this is a well-practiced scenario.Notes/Assumptions: There is no reason to expect other than verbatim compliance with this instruction.

HFA_0003PMP_START-EPU, OPERATOR FAILS TO RESTART RFW AFTER LEVEL 8 TRIP

Notes/Assumptions:

Notes/Assumptions: Workload would be expected to be relatively high due to attempts to restore some source of HPI. Action primarily triggered based on monitoring RPV level, which is indicated by a variety of displays and meters.Notes/Assumptions:

Notes/Assumptions: Notes/Assumptions: Since a transition among three procedures might be required, and the unit supervisor would be following multiple paths through the EOIs, this is treated as a case of multiple procedures. Placekeeping aids are used in the form of a bracket in which the unit supervisor initials the steps as they are reached.

Notes/Assumptions: Notes/Assumptions: Logic is straightforward, and this is a well-practiced scenario.

Notes/Assumptions: There is no reason to expect other than verbatim compliance with this instruction.

HFA_0071L8RESTART-CLTP, Operator fails to restart RCIC after Level 8 trip

Notes/Assumptions:

Notes/Assumptions: Workload would be expected to be relatively high due to attempts to restore some source of HPI. Action primarily triggered based on monitoring RPV level, which is indicated by a variety of displays and meters.Notes/Assumptions:

Notes/Assumptions: Notes/Assumptions: Since a transition among three procedures might be required, and the unit supervisor would be following multiple paths through the EOIs, this is treated as a case of multiple procedures. Placekeeping aids are used in the form of a bracket in which the unit supervisor initials the steps as they are reached.

Notes/Assumptions: Notes/Assumptions: Logic is straightforward, and this is a well-practiced scenario.

Notes/Assumptions: There is no reason to expect other than verbatim compliance with this instruction.

HFA_0071L8RESTART-EPU, Operator fails to restart RCIC after Level 8 trip

Notes/Assumptions:

Notes/Assumptions: Workload would be expected to be relatively high due to attempts to restore some source of HPI. Action primarily triggered based on monitoring RPV level, which is indicated by a variety of displays and meters.Notes/Assumptions:

Notes/Assumptions: Notes/Assumptions: Since a transition among three procedures might be required, and the unit supervisor would be following multiple paths through the EOIs, this is treated as a case of multiple procedures. Placekeeping aids are used in the form of a bracket in which the unit supervisor initials the steps as they are reached.

Notes/Assumptions: Notes/Assumptions: Logic is straightforward, and this is a well-practiced scenario.

Notes/Assumptions: There is no reason to expect other than verbatim compliance with this instruction.

HFA_0073L8RESTART-CLTP, Operator fails to restart HPCI after Level 8 trip

Notes/Assumptions:

Notes/Assumptions: Workload would be expected to be relatively high due to attempts to restore some source of HPI. Action primarily triggered based on monitoring RPV level, which is indicated by a variety of displays and meters.Notes/Assumptions:

Notes/Assumptions: Notes/Assumptions: Since a transition among three procedures might be required, and the unit supervisor would be following multiple paths through the EOIs, this is treated as a case of multiple procedures. Placekeeping aids are used in the form of a bracket in which the unit supervisor initials the steps as they are reached.

Notes/Assumptions: Notes/Assumptions: Logic is straightforward, and this is a well-practiced scenario.

Notes/Assumptions: There is no reason to expect other than verbatim compliance with this instruction.

HFA_0073L8RESTART-EPU, Operator fails to restart HPCI after Level 8 trip

Notes/Assumptions:

Notes/Assumptions: Workload would be expected to be relatively high due to attempts to restore some source of HPI. Action primarily triggered based on monitoring RPV level, which is indicated by a variety of displays and meters.Notes/Assumptions:

Notes/Assumptions: Notes/Assumptions: Since a transition among three procedures might be required, and the unit supervisor would be following multiple paths through the EOIs, this is treated as a case of multiple procedures. Placekeeping aids are used in the form of a bracket in which the unit supervisor initials the steps as they are reached.

Notes/Assumptions: Notes/Assumptions: Logic is straightforward, and this is a well-practiced scenario.

Notes/Assumptions: There is no reason to expect other than verbatim compliance with this instruction.

HFFA_1SHV0760540_35-CLTP, Local action - close 1-SHV-076-0540 (2- and 3- for Units 2 and 3) within 35 minutes

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HFFA_1SHV0760540_35-EPU, Local action - close 1-SHV-076-0540 (2- and 3- for Units 2 and 3) within 35 minutes

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HFFA0268480CRSTIE-CLTP, FAILURE TO TRANSFER DEENERGIZED 480V BOARD TO ALTERNATE SUPPLY (FIRE)

Notes/Assumptions: Notes/Assumptions: Workload would be expected to be relatively high, but response should be triggered by alarm, and does not require monitoring over time.

Notes/Assumptions: Notes/Assumptions:

Notes/Assumptions: As the operators are in the fire procedures and the ARP's, multiple procedures always apply to fire scenarios. The step in the ARP is not graphically distinct, but there is a checkbox as a placekeeping aid.Notes/Assumptions:

Notes/Assumptions: Logic is straightforward, and should lead to a clear decision to restore power.Notes/Assumptions: There is no reason to expect other than verbatim compliance with this instruction.

HFFA0268480CRSTIE-EPU, FAILURE TO TRANSFER DEENERGIZED 480V BOARD TO ALTERNATE SUPPLY (FIRE)

Notes/Assumptions: Notes/Assumptions: Workload would be expected to be relatively high, but response should be triggered by alarm, and does not require monitoring over time.

Notes/Assumptions: Notes/Assumptions:

Notes/Assumptions: As the operators are in the fire procedures and the ARP's, multiple procedures always apply to fire scenarios. The step in the ARP is not graphically distinct, but there is a checkbox as a placekeeping aid.Notes/Assumptions:

Notes/Assumptions: Logic is straightforward, and should lead to a clear decision to restore power.Notes/Assumptions: There is no reason to expect other than verbatim compliance with this instruction.

HFFA0ASD_RCIC-CLTP , OPERATOR FAILS TO START RCIC

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HFFA0ASD_RCIC-EPU, OPERATOR FAILS TO START RCIC

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