CNL-17-109, Response to NRC Request for Additional Information for License Amendment Request to Revise Modifications and an Implementation Item Related to NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactor Electric Genera

Response to NRC Request for Additional Information for License Amendment Request to Revise Modifications and an Implementation Item Related to NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactor Electric Generati

ML17261B179
Person / Time
Site:	Browns Ferry
Issue date:	09/18/2017
From:	James Shea Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CNL-17-109, TAC MF1185, TAC MF1186, TAC MF1187
Download: ML17261B179 (42)

Text

In Enclosure 1 of the licensee's letter dated June 7, 2017, the licensee provided its basis for the proposed changes. In Change Request 1, the licensee proposed to revise Table S-2 Plant Modifications 52a and 52b (PM-52a and b) to clarify the modification descriptions.

The licensee proposed to change PM-52a from: "For Drywell wide range pressure instruments P-64-160A and B, provide isolation of associated circuits and make appropriate power supply available such that both division instruments are not lost in the same fire scenario," to "Modify power supplies and associated circuits for drywell pressure indication instruments such that indication is available in the MCR [main control room] for all fire scenarios except those in Fire Area (FA) 16." The licensee proposed to change PM-52b from: "Provide containment pressure indication on the Backup Control Panel," to "Provide isolation from circuits in FA 16 for containment pressure indication on the Backup Control Panel." In Change Request 2, the licensee proposed to delete Plant Modification 84 (PM-84) from Table S-2. Modification 84 reduced the time overcurrent setting (TOC) for breakers 1126, 1132, 1226, and 1232 in the offsite power circuits so that the breakers would trip prior to incurring any thermal damage. Thus, the modificat i on would enable subsequent recovery actions to clear the spurious loads and reclose the off-site power breakers.

Competing design elements were identified during the des i gn process that limit the amount that the TOC settings could be reduced. NFPA 805, Section 4.2.4.2, requires that the "use of fire risk evaluation for the PB [performance

-based] approach shall consist of an integrated assessment of the acceptability of risk, defense-in-depth, and safety margins." In the risk impact discussion for the proposed Change Request 1, the licensee stated that "the final modification is expected to be equal to or better than the modification originally described in Table S-2 of the NFPA 805 LAR with respect to fire risk." In the risk impact discussion for the proposed Change Request 2, the licensee calculated the change in risk and total risk for Units 1, 2, and 3. However, the licensee did not evaluate the change in risk from the compliant NFPA 805 PRA model, and thus did not establi sh that Regulatory Guide (RG) 1.174, "An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis," Revision 2, (ADAMS Accession No. ML100910006), guidelines would have been met if the proposed configurations had been part of the NFPA 805 LAR upon which the NRC staff safety evaluation (SE) was based.

A. Provide the change in core damage frequency (CDF) and large early release frequency (LERF), and total CDF and LERF for Units 1, 2, and 3 with both Change Requests 1 and 2 integrated simultaneously into the PRA results for the transition plant. (1) Calculate the change in risk using the compliant PRA model supporting the NFPA 805 SE, adjusted for Change Requests 1 and 2 as appropriate.

Summarize any changes made to the compliant PRA model due to proposed Change Requests 1 and 2. Alternately, provi de a justification for the choice of another compliant PRA model. (2) Indicate how the risk from these plant changes compares with the

guidelines in RG 1.174, Revision 2. B. Confirm that Option A of the NRC letter to Nuclear Energy Institute (NEI), "Recommended Content for License Amendment Requests that Seek Changes to License Conditions that were Established in Amendments to Adopt National Fire Protection Association Standard 805, but Have Yet to be Fully Implemented," dated March 2, 2016 (ADAMS Accession No. ML16015A416), is still appropriate for this proposed LAR, given the new risk analysis to be performed. If not, provide the necessary information for Option B or C, whichever is appropriate.

In the Defense-in-Depth/Safety Margin Discussion for the proposed change 1, the licensee stated that "the changes to drywell pressure instrumentation made available through PM-52 (a, b, and c) do not affect any defense-in-depth (DID) or Safety Margin." NFPA 805, Section 4.2.4.2, requires that the "use of fire risk evaluation for the PB approach shall consist of an integrated assessment of the acceptability of risk, defense-in-depth, and safety margins." NEI 04-02, "Guidance for Implementing a Risk-Informed, Performance

-Based Fire Protection Program Under 10 CFR 50.48(c)," Revision 2 (ADAMS Accessi on No. ML081130188), Section 5.3.5.3, "Safety Margins," lists two specific criteria that should be addressed when considering the impact of plant changes on safety margins: Codes and standards or their alternatives accepted for use by the NRC are met; and, Safety analysis acceptance criteria in the licensing basis (e.g., FSAR [Final Safety Analysis Report], supporting analyses, etc.) are met, or provides sufficient margin to account for analysis and data uncertainty.

Based on the information provided by the licensee, the NRC is unable to comp lete its rev i ew because the application did not prov i de sufficient information regarding the acceptab ility of DID and safety margins for this proposed change. Provide the following:

A. A discussion regarding DID that includes the basis for why the proposed changes do not impact each echelon of DID. B. A discuss i on of safety margins that includes the basis for why the proposed changes do not impact the safety margin criteria discussed in NEI 04-02.

In the DID/Safety Margin Discussion for the proposed Change Request 2, the licensee stated that "non-implementation of PM-84 does not affect DID Echelons 2 or 3." No basis is cited for its conclusion wi th respect to Eche l on 3, "Provide adequate level of fire protection for systems and structures so that a fire will not prevent essential safety functions from being performed," even though the removal of the PM-84 no longer prevents the failure of the offs i te power supply to inventory makeup and decay heat removal systems for the fire-induced spurious operation cited in the discussion on this modification. NFPA 805, Section 4.2.4.2, requires that the "use of fire risk evaluation for the PB approach shall cons ist of an integrated assessment of the acceptability of risk, defense-in-depth, and safety margins."

Provide a justification that Echelon 3 of DID is still sufficiently robust after removal of modification, PM-84.

Risk-Informed Changes that May Be Made Without Prior NRC Approval

-Sb- Risk-Informed Changes that May Be Made Without Prior NRC Approval

Transition License Conditions O O O

-4b- BFN-UNIT 3 Renewed License No. DPR-68 Amendment No. 273 October 28, 2015 The licensee may use an engineering evaluation to demonstrate that changes to certain NFPA 805, Chapter 3 elements are acceptable because the alternative is "adequate for the hazard." Prior NRC review and approval would not be required for alternatives to four specific sections of NFPA 805, Chapter 3, for which an engineering evaluation demonstrates that the alternative to the Chapter 3 element is adequate for the hazard. A qualified fire protection engineer shall perform the engineering evaluation and conclude that the change has not affected the functionality of the component, system, procedure, or physical arrangement, using a relevant technical requirement or standard. The four specific sections of NFPA 805, Chapter 3, are as follows: *Fire Alarm and Detection Systems (Section 3.8);*Automatic and Manual Water-Based Fire Suppression Systems(Section 3.9);*Gaseous Fire Suppression Systems (Section 3.10); and*Passive Fire Protection Features (Section 3.11).This License Condition does not apply to any demonstration of equivalency under Section 1.7 of NFPA 805. 2.Fire Protection Program Changes that Have No More than Minimal Risk ImpactPrior NRC review and approval are not required for changes to the licensee'sfire protection program that have been demonstrated to have no more than aminimal risk impact. The licensee may use its screening process as approvedin the NRC Safety Evaluation dated October 28, 2015, to determine thatcertain fire protection program changes meet the minimal criterion. Thelicensee shall ensure that fire protection defense-in- depth and safety marginsare maintained when changes are made to the fire protection program.Transition License Conditions 1.Before achieving full compliance with 10 CFR 50.48(c), as specified by(2) below, risk-informed changes to the licensee's fire protection program maynot be made without prior NRC review and approval unless the change hasbeen demonstrated to have no more than a minimal risk impact, as described in(2) above.2.The licensee shall implement the following modifications to its facility, asdescribed in Table S-2, "Plant Modifications," of Tennessee Valley Authorityletter CNL-15-191, dated September 8, 2015, to complete the transition to fullcompliance with 10 CFR 50.48(c) no later than the end of the second refuelingoutage (for each unit) following issuance of the license amendment. Thelicensee shall maintain appropriate compensatory measures in place untilcompletion of these modifications.

-4b- BFN-UNIT 3 Renewed License No. DPR-68 Amendment No. The licensee may use an engineering evaluation to demonstrate that changes to certain NFPA 805, Chapter 3 elements are acceptable because the alternative is "adequate for the hazard." Prior NRC review and approval would not be required for alternatives to four specific sections of NFPA 805, Chapter 3, for which an engineering evaluation demonstrates that the alternative to the Chapter 3 element is adequate for the hazard. A qualified fire protection engineer shall perform the engineering evaluation and conclude that the change has not affected the functionality of the component, system, procedure, or physical arrangement, using a relevant technical requirement or standard. The four specific sections of NFPA 805, Chapter 3, are as follows: *Fire Alarm and Detection Systems (Section 3.8);*Automatic and Manual Water-Based Fire Suppression Systems(Section 3.9);*Gaseous Fire Suppression Systems (Section 3.10); and*Passive Fire Protection Features (Section 3.11).This License Condition does not apply to any demonstration of equivalency under Section 1.7 of NFPA 805. 2.Fire Protection Program Changes that Have No More than Minimal Risk ImpactPrior NRC review and approval are not required for changes to the licensee'sfire protection program that have been demonstrated to have no more than aminimal risk impact. The licensee may use its screening process as approvedin the NRC Safety Evaluation dated October 28, 2015, to determine that certain fire protection program changes meet the minimal criterion. The licensee shall ensure that fire protection defense-in- depth and safety margins are maintained when changes are made to the fire protection program.Transition License Conditions 1.Before achieving full compliance with 10 CFR 50.48(c), as specified by(2) below, risk-informed changes to the licensee's fire protection program maynot be made without prior NRC revi ew and approval unless the change hasbeen demonstrated to have no more than a minimal risk impact, as described in(2) above.

2.The licensee shall implement m odifications to its facility, asdescribed in Table S-2, "Plant Modifi cations,"

of Tennessee Va lley Authorityletter CNL-1-,o complete the transition to fullcompliance with 1 0CFR 50.48(c) no later than the end of the second refuelingoutage (for eachunit)fo llowing issuance of the . Thelicensee sha llmaintain appropriate compensatory measures inplace untilcompletion of thesemodifications.