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{{#Wiki_filter:1 NRR-PMDAPEm Resource From: Lingam, Siva Sent: Wednesday, February 04, 2015 9:38 AM To: mjrm@pge.com Cc: Oesterle, Eric; Klein, Alex; Hamzehee, Hossein; Miller, Barry; Fields, Leslie
{{#Wiki_filter:NRR-PMDAPEm Resource From:                       Lingam, Siva Sent:                       Wednesday, February 04, 2015 9:38 AM To:                         mjrm@pge.com Cc:                         Oesterle, Eric; Klein, Alex; Hamzehee, Hossein; Miller, Barry; Fields, Leslie


==Subject:==
==Subject:==
Diablo Canyon, Units 1 and 2 - Requests for Additi onal Information (RAIs) for Fire Protection (NFPA-805) License Amendment Reques t (LAR) (TAC Nos. MF2333 and MF2334)Please note the following official RAIs for the subject LAR, and provide your responses by February 27, 2015 (as agreed mutually on January 21, 2015 conference call):
Diablo Canyon, Units 1 and 2 - Requests for Additional Information (RAIs) for Fire Protection (NFPA-805) License Amendment Request (LAR) (TAC Nos. MF2333 and MF2334)
Probabilistic Risk Assessment (PRA) RAI 01.f.01 (PRA Models of Reactor Coolant Pump Shutdown Seals) The response to PRA RAI 01.f (in a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635))
Please note the following official RAIs for the subject LAR, and provide your responses by February 27, 2015 (as agreed mutually on January 21, 2015 conference call):
states that given the unacceptable operating experience with the Westinghouse reactor coolant pump (RCP) Shutdown Seals (SDS), Pacific Gas and Electric Company (PG&E, the licensee) has decided to install redesigned Westinghouse RCP Generation Ill SDS (GEN Ill) instead and explains that:
Probabilistic Risk Assessment (PRA) RAI 01.f.01 (PRA Models of Reactor Coolant Pump Shutdown Seals)
 
The response to PRA RAI 01.f (in a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635))
"Modeling of the RCP GEN Ill SDS applicable to the FPRA model as well as other hazard PRA models will be based on guidance in PWROG-14001-P, Revision 1, 'PRA Model for the Generation Ill Westinghouse Shutdown Seal.' PWROG-14001-P, Revision 1 has been submitted to NRC (Reference PWROG OG-14-211 dated July 3, 2014) but has not yet been approved. The post-transition FPRA model will be verified to reflect the as-approved version of PWROG-14001-P before it is used as a basis in self-approval of post transition changes. This report provides the basis for the GEN Ill SDS credit in the PRA model in the response to PRA RAI 3."
states that given the unacceptable operating experience with the Westinghouse reactor coolant pump (RCP)
The U.S. Nuclear Regulatory Commission (NRC) is accepting models of SDS failure based on the best available information at the time of transition when accompanied by assurance that accepted models will be used when available. Provide a Table S-3 implementation item stating that PG&E will use NRC accepted SDS failure models as these become available to confirm, as a minimum, that the transition change-in-risk estimates will not exceed the Regulatory Guide (RG) 1.205 acceptance guidelines. The implementation item should also clarify that self-approved changes that rely on the SDS failure model will not be undertaken before acceptable models have been developed.  
Shutdown Seals (SDS), Pacific Gas and Electric Company (PG&E, the licensee) has decided to install redesigned Westinghouse RCP Generation Ill SDS (GEN Ill) instead and explains that:
 
Modeling of the RCP GEN Ill SDS applicable to the FPRA model as well as other hazard PRA models will be based on guidance in PWROG-14001-P, Revision 1, PRA Model for the Generation Ill Westinghouse Shutdown Seal. PWROG-14001-P, Revision 1 has been submitted to NRC (Reference PWROG OG       211 dated July 3, 2014) but has not yet been approved. The post-transition FPRA model will be verified to reflect the as-approved version of PWROG-14001-P before it is used as a basis in self-approval of post transition changes. This report provides the basis for the GEN Ill SDS credit in the PRA model in the response to PRA RAI 3.
PRA RAI 01.g.01 (Electrical Distribution Panel Fire Scenarios)  
The U.S. Nuclear Regulatory Commission (NRC) is accepting models of SDS failure based on the best available information at the time of transition when accompanied by assurance that accepted models will be used when available. Provide a Table S-3 implementation item stating that PG&E will use NRC accepted SDS failure models as these become available to confirm, as a minimum, that the transition change-in-risk estimates will not exceed the Regulatory Guide (RG) 1.205 acceptance guidelines. The implementation item should also clarify that self-approved changes that rely on the SDS failure model will not be undertaken before acceptable models have been developed.
 
PRA RAI 01.g.01 (Electrical Distribution Panel Fire Scenarios)
The response to PRA RAI 01.g (in a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635)) states that guidance in Section 6.5.6 of NUREG/CR-6850, "EPRI/NRC-RES Fire PRA Methodology for Nuclear Power Facilities: Summary and Overview," September 2005 (ADAMS Accession No. ML052580075), and Section 8.2 of NUREG/CR-6850, Supplement 1 (specifically FAQ 08-0042, "Fire Propagation from Electrical Cabinets") was used to screen "[w]ell-sealed electrical cabinets that have robustly secured doors (and/or access panels) and that house only circuits below 440 V."  However, the response also states: "[n]o cabinets that are PRA components were screened," and that "a fire scenario [was] still created if the cabinet was a PRA component or had terminating PRA cables."  Therefore, it appears that even though well sealed and secured electrical cabinets below 440 V that are PRA components or have terminating PRA cables could have been screened, they were, nonetheless, included in the Fire PRA as sources for non-propagating fire scenarios. It is not clear whether this departure in applying NUREG/CR-6850 guidance constitutes conservative or non-conservative treatment. If these unscreened cabinets were included in the fire ignition Bin 15 count, then they would have the effect of reducing the per-cabinet fire frequency (i.e., diluting the count). Clarify whether your approach of including well sealed and secured cabinets that are PRA components or have terminating PRA cables conservatively or non-conservatively estimates the risk results (i.e., core damage frequency (CDF), large early release frequency (LERF), CDF, and LERF). If the risk results are underestimated, then replace this approach with an acceptable approach in the integrated analysis provided in response to PRA RAI 03.
The response to PRA RAI 01.g (in a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635))
2 PRA RAI 05.01 (Reduced Transient Heat Release Rate)
states that guidance in Section 6.5.6 of NUREG/CR-6850, "EPRI/NRC-RES Fire PRA Methodology for Nuclear Power Facilities: Summary and Overview," September 2005 (ADAMS Accession No. ML052580075), and Section 8.2 of NUREG/CR-6850, Supplement 1 (specifically FAQ 08-0042, Fire Propagation from Electrical Cabinets) was used to screen [w]ell-sealed electrical cabinets that have robustly secured doors (and/or access panels) and that house only circuits below 440 V. However, the response also states: [n]o cabinets that are PRA components were screened, and that a fire scenario [was] still created if the cabinet was a PRA component or had terminating PRA cables. Therefore, it appears that even though well sealed and secured electrical cabinets below 440 V that are PRA components or have terminating PRA cables could have been screened, they were, nonetheless, included in the Fire PRA as sources for non-propagating fire scenarios. It is not clear whether this departure in applying NUREG/CR-6850 guidance constitutes conservative or non-conservative treatment. If these unscreened cabinets were included in the fire ignition Bin 15 count, then they would have the effect of reducing the per-cabinet fire frequency (i.e., diluting the count). Clarify whether your approach of including well sealed and secured cabinets that are PRA components or have terminating PRA cables conservatively or non-conservatively estimates the risk results (i.e., core damage frequency (CDF),
 
large early release frequency (LERF), CDF, and LERF). If the risk results are underestimated, then replace this approach with an acceptable approach in the integrated analysis provided in response to PRA RAI 03.
The response to PRA RAI 05 (in a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635)) does not identify current or updated controls for Fire Co mpartment 6-A-3 that will preclude or limit combustible quantities of transient material that could generate heat release rates (HRRs) above the reduced HRRs assumed in the fire modeling. The response explains there are no pumps or oil in this fire compartment, but acknowledges that there is normal access to Fire Compartment 6-A-3. It is not clear what limits quantities of transient combustibles in this area, which may or may not be similar to materials for which testing results are presented in Table G-7 of NUREG/CR-6850. Describe the controls that justify limiting the 98% HRR modeled for this fire compartment to 142 kW.   
1
 
PRA RAI 11.01 (Apportioning the Generic Junction Box Fire Frequency to Each PAU)
 
The response to PRA RAI 11 (in a letter dated October 29, 2014 (ADAMS Accession No. ML14302A805)) states that the method used for apportioning the generic junction box fire frequency to each physical analysis unit (PAU) is consistent with the method described in Section 3.2 of FAQ 13-0006, "Modeling Junction Box Scenarios in a Fire PRA," and derives that the junction box frequency for a PAU is related to the cable load of a PAU to the total plant cable load. The derivation relies upon FAQ 13-0006, in particular, the response explains per FAQ 13-0006 that "the number of junction boxes in a specific PAU can be assumed to be proportional to the ratio of the number of junction boxes to conduits in a representative, comparable PAU and the cable loading associated with the location. The proportionality constant can be developed by determining the count in a relatively simple PAU (e.g., a PAU where the junction boxes could be counted during a walkdown) and applying the value consistently throughout the plant."  It appears that a proportionality constant (PC) was derived for application to all PAUs. However, the response does not identify from which PAU the PC was derived and why the PC from that PAU can be considered to be representative for the rest of the plant. Please identify from which PAU the PC was derived and why the PC from that PAU can be considered to be representative for the rest of the plant. If you are unable to justify your selected PC, then apply acceptable methods to determine the risk from junction box fires, and update the response to PRA RAI 03.


PRA RAI 05.01 (Reduced Transient Heat Release Rate)
The response to PRA RAI 05 (in a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635))
does not identify current or updated controls for Fire Compartment 6-A-3 that will preclude or limit combustible quantities of transient material that could generate heat release rates (HRRs) above the reduced HRRs assumed in the fire modeling. The response explains there are no pumps or oil in this fire compartment, but acknowledges that there is normal access to Fire Compartment 6-A-3. It is not clear what limits quantities of transient combustibles in this area, which may or may not be similar to materials for which testing results are presented in Table G-7 of NUREG/CR-6850. Describe the controls that justify limiting the 98% HRR modeled for this fire compartment to 142 kW.
PRA RAI 11.01 (Apportioning the Generic Junction Box Fire Frequency to Each PAU)
The response to PRA RAI 11 (in a letter dated October 29, 2014 (ADAMS Accession No. ML14302A805))
states that the method used for apportioning the generic junction box fire frequency to each physical analysis unit (PAU) is consistent with the method described in Section 3.2 of FAQ 13-0006, Modeling Junction Box Scenarios in a Fire PRA, and derives that the junction box frequency for a PAU is related to the cable load of a PAU to the total plant cable load. The derivation relies upon FAQ 13-0006, in particular, the response explains per FAQ 13-0006 that "the number of junction boxes in a specific PAU can be assumed to be proportional to the ratio of the number of junction boxes to conduits in a representative, comparable PAU and the cable loading associated with the location. The proportionality constant can be developed by determining the count in a relatively simple PAU (e.g., a PAU where the junction boxes could be counted during a walkdown) and applying the value consistently throughout the plant." It appears that a proportionality constant (PC) was derived for application to all PAUs. However, the response does not identify from which PAU the PC was derived and why the PC from that PAU can be considered to be representative for the rest of the plant.
Please identify from which PAU the PC was derived and why the PC from that PAU can be considered to be representative for the rest of the plant. If you are unable to justify your selected PC, then apply acceptable methods to determine the risk from junction box fires, and update the response to PRA RAI 03.
PRA RAI 15.01 (Large Risk Reduction Credit)
PRA RAI 15.01 (Large Risk Reduction Credit)
NRC staff notes that based on the response to PRA RAI 15 (in a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635)) the most dominant scenario for the compliant plant model for both units (by a wide margin) is the whole-room burn-up scenario for t he Cable Spreading Room (CSR), representing most of the risk reduction credit realized in the "risk offset" values presented in Tables W-4 and W-5 of the license amendment request. Whole-room burn-up modeling implies that this fire area was conservatively modeled. If this fire area was conservatively modeled, then it appears that this scenario contributes to overestimation of the compliant plant risk and therefore underestimation of the change-in-risk estimates.  
NRC staff notes that based on the response to PRA RAI 15 (in a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635)) the most dominant scenario for the compliant plant model for both units (by a wide margin) is the whole-room burn-up scenario for the Cable Spreading Room (CSR), representing most of the risk reduction credit realized in the risk offset values presented in Tables W-4 and W-5 of the license amendment request. Whole-room burn-up modeling implies that this fire area was conservatively modeled. If this fire area was conservatively modeled, then it appears that this scenario contributes to overestimation of the compliant plant risk and therefore underestimation of the change-in-risk estimates.
 
In light of potential conservatism in the compliant plant modeling, demonstrate that the net change-in-risk (i.e.,
In light of potential conservatism in the compliant plant modeling, demonstrate that the net change-in-risk (i.e., total risk decrease associated with non-VFDR [variance from deterministic requirements] risk reduction modifications and total risk increase associated with unresolved VFDRs) associated with the integrated analysis presented in response to PRA RAI 03 meet RG 1.174 CDF and LERF risk guidelines.
total risk decrease associated with non-VFDR [variance from deterministic requirements] risk reduction modifications and total risk increase associated with unresolved VFDRs) associated with the integrated analysis presented in response to PRA RAI 03 meet RG 1.174 CDF and LERF risk guidelines.
Fire Modeling (FM) RAI 01.c.01  
Fire Modeling (FM) RAI 01.c.01 In a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635), the licensee responded to FM RAI 01.c and stated that a mass-weighted average heat release rate per unit area (HRRPUA) was used in the fire propagation calculations for trays with a mixture of thermoplastic and thermoset cables, as recommended in NUREG/CR-7010, Cable Heat Release, Ignition, and Spread in Tray Installations During Fire (CHRISTIFIRE).
The response indicates that the same approach (mass-weighted average) was used to determine the flame spread rate for trays with mixed cables. However, NUREG/CR-7010 recommends that for trays with mixed cables the flame spread rate for the predominant material be applied (see page 153).
2


In a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635), the licensee responded to FM RAI 01.c and stated that a mass-weighted average heat release rate per unit area (HRRPUA) was used in the fire propagation calculations for trays with a mixture of thermoplastic and thermoset cables, as recommended in NUREG/CR-7010, "Cable Heat Release, Ignition, and Spread in Tray Installations During Fire (CHRISTIFIRE)."
Provide technical justification for using a mass-weighted flame spread rate for trays with more than 50%
The response indicates that the same approach (mass-weighted average) was used to determine the flame spread rate for trays with mixed cables. However, NUREG/CR-7010 recommends that for trays with mixed cables the flame spread rate for the predominant material be applied (see page 153).
3  Provide technical justification for using a mass-weighted flame spread rate for trays with more than 50%
thermoplastic cable.
thermoplastic cable.
FM RAI 01.g.01 In a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635), the licensee responded to FM RAI 01.g and described the procedure that was used to model high energy arcing fault (HEAF)-initiated fires.
FM RAI 01.g.01 In a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635), the licensee responded to FM RAI 01.g and described the procedure that was used to model high energy arcing fault (HEAF)-initiated fires.
The response provides details regarding the HRR of HEAF fires, duration and growth, damage conditions, etc. However, the propagation of HEAF-initiated fires in secondary combustibles, such as cable trays is not discussed.  
The response provides details regarding the HRR of HEAF fires, duration and growth, damage conditions, etc.
 
However, the propagation of HEAF-initiated fires in secondary combustibles, such as cable trays is not discussed.
Explain how HEAF-initiated fire propagation in secondary combustibles was modeled.
Explain how HEAF-initiated fire propagation in secondary combustibles was modeled.
FM RAI 02.b.01  
FM RAI 02.b.01 In a letter dated October 29, 2014 (ADAMS Accession No. ML14302A804), the licensee responded to FM RAI 02.b stating that cable tray covers were assumed not to impact cable damage thresholds, but were credited with delaying damage and ignition in accordance with NUREG/CR-6850, Appendix Q.2.2. Furthermore, the response stated that bottom covers with small and infrequent gaps or holes may have been credited to delay ignition.
 
(i) Appendix Q.2.2 of NUREG/CR-6850 notes that cable tray fire barrier tests performed by Sandia National Laboratories showed that barriers seem to substantially delay cable damage for qualified cable, but not for nonqualified cable. Explain how the barriers were credited for trays with a mixture of qualified and nonqualified cables.
In a letter dated October 29, 2014 (ADAMS Accession No. ML14302A804), the licensee responded to FM RAI 02.b stating that cable tray covers were assumed not to impact cable damage thresholds, but were credited with delaying damage and ignition in accordance with NUREG/CR-6850, Appendix Q.2.2. Furthermore, the response stated that bottom covers with small and infrequent gaps or holes may have been credited to delay ignition.
(ii) Provide details on the length of the assumed ignition delay for covered trays with small and infrequent gaps or holes and the technical basis.
 
(i)   Appendix Q.2.2 of NUREG/CR-6850 notes that cable tray fire barrier tests performed by Sandia National Laboratories showed that barriers seem to substantially delay cable damage for qualified cable, but not for nonqualified cable. Explain how the barriers were credited for trays with a mixture of qualified and nonqualified cables.  
 
(ii) Provide details on the length of the assumed ignition delay for covered trays with small and infrequent gaps or holes and the technical basis.
Siva P. Lingam U.S. Nuclear Regulatory Commission Project Manager (NRR/DORL/LPL4-1)
Siva P. Lingam U.S. Nuclear Regulatory Commission Project Manager (NRR/DORL/LPL4-1)
Cooper Nuclear Station Diablo Canyon Nuclear Power Plant Location: O8-D5; Mail Stop: O8-B3 Telephone: 301-415-1564; Fax: 301-415-1222 E-mail address: siva.lingam@nrc.gov
Cooper Nuclear Station Diablo Canyon Nuclear Power Plant Location: O8-D5; Mail Stop: O8-B3 Telephone: 301-415-1564; Fax: 301-415-1222 E-mail address: siva.lingam@nrc.gov 3


Hearing Identifier: NRR_PMDA Email Number: 1851   Mail Envelope Properties   (Siva.Lingam@nrc.gov20150204093700)
Hearing Identifier:       NRR_PMDA Email Number:             1851 Mail Envelope Properties       (Siva.Lingam@nrc.gov20150204093700)


==Subject:==
==Subject:==
Diablo Canyon, Units 1 and 2 - Requests for Additional Information (RAIs) for Fire Protection (NFPA-805) License Amendment Request (LAR) (TAC Nos. MF2333 and MF2334) Sent Date:   2/4/2015 9:37:38 AM Received Date: 2/4/2015 9:37:00 AM From:   Lingam, Siva Created By:   Siva.Lingam@nrc.gov Recipients:     "Oesterle, Eric" <Eric.Oesterle@nrc.gov> Tracking Status: None "Klein, Alex" <Alex.Klein@nrc.gov> Tracking Status: None "Hamzehee, Hossein" <Hossein.Hamzehee@nrc.gov>
Diablo Canyon, Units 1 and 2 - Requests for Additional Information (RAIs) for Fire Protection (NFPA-805) License Amendment Request (LAR) (TAC Nos. MF2333 and MF2334)
Tracking Status: None "Miller, Barry" <Barry.Miller@nrc.gov> Tracking Status: None "Fields, Leslie" <Leslie.Fields@nrc.gov> Tracking Status: None "mjrm@pge.com" <mjrm@pge.com>
Sent Date:               2/4/2015 9:37:38 AM Received Date:           2/4/2015 9:37:00 AM From:                     Lingam, Siva Created By:               Siva.Lingam@nrc.gov Recipients:
Tracking Status: None Post Office:     Files     Size     Date & Time MESSAGE   10374     2/4/2015 9:37:00 AM
"Oesterle, Eric" <Eric.Oesterle@nrc.gov>
 
Tracking Status: None "Klein, Alex" <Alex.Klein@nrc.gov>
Options Priority:     Standard   Return Notification:   No   Reply Requested:   No   Sensitivity:     Normal Expiration Date:     Recipients Received:}}
Tracking Status: None "Hamzehee, Hossein" <Hossein.Hamzehee@nrc.gov>
Tracking Status: None "Miller, Barry" <Barry.Miller@nrc.gov>
Tracking Status: None "Fields, Leslie" <Leslie.Fields@nrc.gov>
Tracking Status: None "mjrm@pge.com" <mjrm@pge.com>
Tracking Status: None Post Office:
Files                             Size                     Date & Time MESSAGE                           10374                   2/4/2015 9:37:00 AM Options Priority:                         Standard Return Notification:             No Reply Requested:                 No Sensitivity:                     Normal Expiration Date:
Recipients Received:}}

Revision as of 17:13, 31 October 2019

Requests for Additional Information (Rais) for Fire Protection (NFPA-805) License Amendment Request (LAR) (TAC Nos. MF2333 and MF2334)
ML15035A162
Person / Time
Site: Diablo Canyon  Pacific Gas & Electric icon.png
Issue date: 02/04/2015
From: Siva Lingam
Plant Licensing Branch IV
To: Richardson M
Pacific Gas & Electric Co
References
TAC MF2333, TAC MF2334
Download: ML15035A162 (4)
v • d • e


Text

NRR-PMDAPEm Resource From: Lingam, Siva Sent: Wednesday, February 04, 2015 9:38 AM To: mjrm@pge.com Cc: Oesterle, Eric; Klein, Alex; Hamzehee, Hossein; Miller, Barry; Fields, Leslie

Subject:

Diablo Canyon, Units 1 and 2 - Requests for Additional Information (RAIs) for Fire Protection (NFPA-805) License Amendment Request (LAR) (TAC Nos. MF2333 and MF2334)

Please note the following official RAIs for the subject LAR, and provide your responses by February 27, 2015 (as agreed mutually on January 21, 2015 conference call):

Probabilistic Risk Assessment (PRA) RAI 01.f.01 (PRA Models of Reactor Coolant Pump Shutdown Seals)

The response to PRA RAI 01.f (in a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635))

states that given the unacceptable operating experience with the Westinghouse reactor coolant pump (RCP)

Shutdown Seals (SDS), Pacific Gas and Electric Company (PG&E, the licensee) has decided to install redesigned Westinghouse RCP Generation Ill SDS (GEN Ill) instead and explains that:

Modeling of the RCP GEN Ill SDS applicable to the FPRA model as well as other hazard PRA models will be based on guidance in PWROG-14001-P, Revision 1, PRA Model for the Generation Ill Westinghouse Shutdown Seal. PWROG-14001-P, Revision 1 has been submitted to NRC (Reference PWROG OG 211 dated July 3, 2014) but has not yet been approved. The post-transition FPRA model will be verified to reflect the as-approved version of PWROG-14001-P before it is used as a basis in self-approval of post transition changes. This report provides the basis for the GEN Ill SDS credit in the PRA model in the response to PRA RAI 3.

The U.S. Nuclear Regulatory Commission (NRC) is accepting models of SDS failure based on the best available information at the time of transition when accompanied by assurance that accepted models will be used when available. Provide a Table S-3 implementation item stating that PG&E will use NRC accepted SDS failure models as these become available to confirm, as a minimum, that the transition change-in-risk estimates will not exceed the Regulatory Guide (RG) 1.205 acceptance guidelines. The implementation item should also clarify that self-approved changes that rely on the SDS failure model will not be undertaken before acceptable models have been developed.

PRA RAI 01.g.01 (Electrical Distribution Panel Fire Scenarios)

The response to PRA RAI 01.g (in a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635))

states that guidance in Section 6.5.6 of NUREG/CR-6850, "EPRI/NRC-RES Fire PRA Methodology for Nuclear Power Facilities: Summary and Overview," September 2005 (ADAMS Accession No. ML052580075), and Section 8.2 of NUREG/CR-6850, Supplement 1 (specifically FAQ 08-0042, Fire Propagation from Electrical Cabinets) was used to screen [w]ell-sealed electrical cabinets that have robustly secured doors (and/or access panels) and that house only circuits below 440 V. However, the response also states: [n]o cabinets that are PRA components were screened, and that a fire scenario [was] still created if the cabinet was a PRA component or had terminating PRA cables. Therefore, it appears that even though well sealed and secured electrical cabinets below 440 V that are PRA components or have terminating PRA cables could have been screened, they were, nonetheless, included in the Fire PRA as sources for non-propagating fire scenarios. It is not clear whether this departure in applying NUREG/CR-6850 guidance constitutes conservative or non-conservative treatment. If these unscreened cabinets were included in the fire ignition Bin 15 count, then they would have the effect of reducing the per-cabinet fire frequency (i.e., diluting the count). Clarify whether your approach of including well sealed and secured cabinets that are PRA components or have terminating PRA cables conservatively or non-conservatively estimates the risk results (i.e., core damage frequency (CDF),

large early release frequency (LERF), CDF, and LERF). If the risk results are underestimated, then replace this approach with an acceptable approach in the integrated analysis provided in response to PRA RAI 03.

1

PRA RAI 05.01 (Reduced Transient Heat Release Rate)

The response to PRA RAI 05 (in a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635))

does not identify current or updated controls for Fire Compartment 6-A-3 that will preclude or limit combustible quantities of transient material that could generate heat release rates (HRRs) above the reduced HRRs assumed in the fire modeling. The response explains there are no pumps or oil in this fire compartment, but acknowledges that there is normal access to Fire Compartment 6-A-3. It is not clear what limits quantities of transient combustibles in this area, which may or may not be similar to materials for which testing results are presented in Table G-7 of NUREG/CR-6850. Describe the controls that justify limiting the 98% HRR modeled for this fire compartment to 142 kW.

PRA RAI 11.01 (Apportioning the Generic Junction Box Fire Frequency to Each PAU)

The response to PRA RAI 11 (in a letter dated October 29, 2014 (ADAMS Accession No. ML14302A805))

states that the method used for apportioning the generic junction box fire frequency to each physical analysis unit (PAU) is consistent with the method described in Section 3.2 of FAQ 13-0006, Modeling Junction Box Scenarios in a Fire PRA, and derives that the junction box frequency for a PAU is related to the cable load of a PAU to the total plant cable load. The derivation relies upon FAQ 13-0006, in particular, the response explains per FAQ 13-0006 that "the number of junction boxes in a specific PAU can be assumed to be proportional to the ratio of the number of junction boxes to conduits in a representative, comparable PAU and the cable loading associated with the location. The proportionality constant can be developed by determining the count in a relatively simple PAU (e.g., a PAU where the junction boxes could be counted during a walkdown) and applying the value consistently throughout the plant." It appears that a proportionality constant (PC) was derived for application to all PAUs. However, the response does not identify from which PAU the PC was derived and why the PC from that PAU can be considered to be representative for the rest of the plant.

Please identify from which PAU the PC was derived and why the PC from that PAU can be considered to be representative for the rest of the plant. If you are unable to justify your selected PC, then apply acceptable methods to determine the risk from junction box fires, and update the response to PRA RAI 03.

PRA RAI 15.01 (Large Risk Reduction Credit)

NRC staff notes that based on the response to PRA RAI 15 (in a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635)) the most dominant scenario for the compliant plant model for both units (by a wide margin) is the whole-room burn-up scenario for the Cable Spreading Room (CSR), representing most of the risk reduction credit realized in the risk offset values presented in Tables W-4 and W-5 of the license amendment request. Whole-room burn-up modeling implies that this fire area was conservatively modeled. If this fire area was conservatively modeled, then it appears that this scenario contributes to overestimation of the compliant plant risk and therefore underestimation of the change-in-risk estimates.

In light of potential conservatism in the compliant plant modeling, demonstrate that the net change-in-risk (i.e.,

total risk decrease associated with non-VFDR [variance from deterministic requirements] risk reduction modifications and total risk increase associated with unresolved VFDRs) associated with the integrated analysis presented in response to PRA RAI 03 meet RG 1.174 CDF and LERF risk guidelines.

Fire Modeling (FM) RAI 01.c.01 In a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635), the licensee responded to FM RAI 01.c and stated that a mass-weighted average heat release rate per unit area (HRRPUA) was used in the fire propagation calculations for trays with a mixture of thermoplastic and thermoset cables, as recommended in NUREG/CR-7010, Cable Heat Release, Ignition, and Spread in Tray Installations During Fire (CHRISTIFIRE).

The response indicates that the same approach (mass-weighted average) was used to determine the flame spread rate for trays with mixed cables. However, NUREG/CR-7010 recommends that for trays with mixed cables the flame spread rate for the predominant material be applied (see page 153).

2

Provide technical justification for using a mass-weighted flame spread rate for trays with more than 50%

thermoplastic cable.

FM RAI 01.g.01 In a letter dated November 26, 2014 (ADAMS Accession No. ML14330A635), the licensee responded to FM RAI 01.g and described the procedure that was used to model high energy arcing fault (HEAF)-initiated fires.

The response provides details regarding the HRR of HEAF fires, duration and growth, damage conditions, etc.

However, the propagation of HEAF-initiated fires in secondary combustibles, such as cable trays is not discussed.

Explain how HEAF-initiated fire propagation in secondary combustibles was modeled.

FM RAI 02.b.01 In a letter dated October 29, 2014 (ADAMS Accession No. ML14302A804), the licensee responded to FM RAI 02.b stating that cable tray covers were assumed not to impact cable damage thresholds, but were credited with delaying damage and ignition in accordance with NUREG/CR-6850, Appendix Q.2.2. Furthermore, the response stated that bottom covers with small and infrequent gaps or holes may have been credited to delay ignition.

(i) Appendix Q.2.2 of NUREG/CR-6850 notes that cable tray fire barrier tests performed by Sandia National Laboratories showed that barriers seem to substantially delay cable damage for qualified cable, but not for nonqualified cable. Explain how the barriers were credited for trays with a mixture of qualified and nonqualified cables.

(ii) Provide details on the length of the assumed ignition delay for covered trays with small and infrequent gaps or holes and the technical basis.

Siva P. Lingam U.S. Nuclear Regulatory Commission Project Manager (NRR/DORL/LPL4-1)

Cooper Nuclear Station Diablo Canyon Nuclear Power Plant Location: O8-D5; Mail Stop: O8-B3 Telephone: 301-415-1564; Fax: 301-415-1222 E-mail address: siva.lingam@nrc.gov 3

Hearing Identifier: NRR_PMDA Email Number: 1851 Mail Envelope Properties (Siva.Lingam@nrc.gov20150204093700)

Subject:

Diablo Canyon, Units 1 and 2 - Requests for Additional Information (RAIs) for Fire Protection (NFPA-805) License Amendment Request (LAR) (TAC Nos. MF2333 and MF2334)

Sent Date: 2/4/2015 9:37:38 AM Received Date: 2/4/2015 9:37:00 AM From: Lingam, Siva Created By: Siva.Lingam@nrc.gov Recipients:

"Oesterle, Eric" <Eric.Oesterle@nrc.gov>

Tracking Status: None "Klein, Alex" <Alex.Klein@nrc.gov>

Tracking Status: None "Hamzehee, Hossein" <Hossein.Hamzehee@nrc.gov>

Tracking Status: None "Miller, Barry" <Barry.Miller@nrc.gov>

Tracking Status: None "Fields, Leslie" <Leslie.Fields@nrc.gov>

Tracking Status: None "mjrm@pge.com" <mjrm@pge.com>

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Files Size Date & Time MESSAGE 10374 2/4/2015 9:37:00 AM Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

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