ML13085A246
| ML13085A246 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 04/22/2013 |
| From: | NRC/NRR/DRA/APLA |
| To: | NRC/NRR/DRA/APLA |
| Snodderly M | |
| References | |
| Download: ML13085A246 (50) | |
Text
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings PP-B2-1 Attachment 2 of the Plant Boundary Documentation has been enhanced to (From peer review:
Definition and Partitioning Report indicates credit demonstrate acceptability of fire coatings Met at CC-II/III given for an Appendix R partitioning feature between credited for fire barriers. For this particular Suggestion)
AA2/AA16. The boundary consists of steel plates example, Engineering Equivalency Evaluation coated with 2-inch Pyrocrete and a technical 11.39, which gives reasonable assurance that RAI not needed.
evaluation was performed to evaluate deviations to the boundary is acceptable, has been the 3-hour rating of the fireproofing material. Since referenced in the CNP Plant Boundary Staff sees that the acceptability of the use of fire coatings are typically not rated for direct flame Definition and Partitioning Report. Pyrocrete Fireproofing on steel walls, ceiling, impingement, Pyrocrete could not be installed on and structural steel components of the Unit 1 some portions, and small through- barrier openings and 2 Auxiliary Feedwater Pump Enclosures exist, it is not clear from the documentation that this is addressed in Engineering Equivalency boundary meets this requirement. Evaluation 11.39. Small portions of the structural steel that are not fully protected Basis for Significance: Documentation enhancement and minor gaps that exist in the 3-hr rated roll-up door and blow-out panel will not lead to spread of fire or impair the ability of the plant to reach a safe and stable condition.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
PP-B2-2 In page 25 of Plant Boundary Definition and The CNP Plant Boundary Definition and (From peer review:
Partitioning Report Rev.1, (R1900-004-001), Partitioning Report has been updated to Met at CC-II/III boundary identification AA2/AA2C has eight reference Engineering Equivalency Evaluation Suggestion) undampered ventilation penetrations between fire 11.56.
zones 110 and 114, & between 111 and 115. But this RAI not needed.
is not supported by a technical evaluation.
Subsequent to the identification of this issue, the Staff that the Plant Boundary Definition and plant personnel generated a technical evaluation to Partitioning Report (R1900-0041-001) was address this issue. Therefore, this F&O now is a updated to reference Engineering documentation issue. The technical evaluation needs Equivalency Evaluation 11.56 (see page 35 to be referred to in the plant partitioning report. of Attachment 2). Engineering Equivalency Evaluation 11.56 documents the acceptability Basis for Significance: Documentation issue only, of eight has eight undampered ventilation does not impact results. penetrations between fire zones 110 and 21-Oct-11 1
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings 114, & between 111 and 115.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
PP-B3-2 (From V-2 Table) Updates made to the Fire PRA since the peer (From peer review:
review incorporated spatial separation Met at CC-I (There is no F&O associated with this SR. However, (specifically for the YD compartment) and Not an F&O)
Table B-6 of the fire PRA WOG Peer Review SR justification for such. This SR is now Assessment Table states reads that: the plant considered to meet Cat II/III. RAI not needed.
portioning analysis at CNP does not credit spatial separation as a portioning element in defining Staff found that the Pant Boundary Definition physical analysis units in Pant Boundary Definition and Partitioning Report Rev. 1, (R1900-004-and Partitioning Report Rev. 1, (R1900-004-001). 001) did credit spatial separation in the case of buildings excluded and Yard partitioning (see page 6 and 7). However, Section 4.3 still contains the statement that plant partitioning at CNP does not credit spatial separation.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
PP-B5-1 Capability Category I of PP-B5 precludes A review of credited active fire barrier elements (From peer review:
crediting active fire barrier elements outside of those (fire dampers, held-open fire doors, water Met at CC-I included in the regulatory fire protection program. curtains) was expanded beyond the Suggestion)
The CNP PRA meets this requirement. Category II/III requirements of specific design codes, by of PP-B5 requires explicit bases and criteria when identifying hazards at CNP that affect these RAI submitted as RAI 34(i) crediting active fire barrier elements. No explicit basis elements, such as high energy arcing faults or criterion has been developed for normally open (HEAFs), as well as hydrogen and transformer During the audit it was explained that further fire doors with fusible links, beyond meeting the explosions. These hazards were evaluated to assessment of active fire barriers was specific design codes required by the fire protection determine thei impact on active fire barrier expanded to include high hazard events (i.e.,
program. elements in order to demonstrate compliance HEAFs, transformer explosions, and with Category II/III criteria. The methodology hydrogen explosions) and is documented in Basis for Significance: Specific recommendations to and results of the review are documented in the Plant Boundary Definition and 21-Oct-11 2
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings meet CC-II/III the CNP Plant Boundary Definition and Partitioning Report (R1900-0041-001), we Partitioning Report. ask an RAI to describe how the multi-compartment analysis was revised as a result.
In the response to RAI 34(i) the licensee cited the provided a description of assessment of active fire barriers was expanded to include consideration of high hazard events (i.e., HEAFs, transformer explosions, and hydrogen explosions) and is documented in the Plant Boundary Definition and Partitioning Report (R1900-0041-001).
Staff sees that Section 4.5 (on pages 9 and
- 10) discusses crediting active fire barriers.
All active fire barriers (i.e., fire dampers, held-open fire doors, water curtains) are identified in Attachment 2 of the Plant Boundary Definition and Partitioning Report .
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
PP-B7-1 Walkdown notes collected for confirming A reference to the confirmatory walkdown (From peer review:
conditions and characteristics of credited partitioning notes has been added to the CNP Plant Met at CC-I-III elements are not referenced in the CNP Plant Boundary Definition and Partitioning Report. Suggestion)
Boundary Definition and Partitioning Report.
RAI not needed.
Basis for Significance: Documentation enhancement Staff sees that a description of confirmatory walkdowns was added as Section 4.7 of the Plant Boundary Definition and Partitioning Report (R1900-0041-001). The walkdowns were performed in accordance with EPM procedure, EPM-DP-FP-002 (Performance of 21-Oct-11 3
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings Field Walkdowns) and are documented under EPM File Access Number 200100120-012.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
PP-C2-1 Exclusion of buildings within the licensee- The CNP Plant Boundary Definition and (From peer review:
controlled area from the global analysis boundary is Partitioning Report has been updated to Met at CC-I-III documented and appears to be reasonable; include more detailed bases for excluded Suggestion) however, more detailed documentation is buildings. In addition, drawings have be added recommended. to enhance graphical illustration of excluded RAI not needed.
locations.
Basis for Significance: Documentation issue Staff sees that the Plant Boundary Definition and Partitioning Report (R1900-0041-001) contains a discussion and detailed listing of excluded locations. Attachment 3 provide s the plant partition boundary drawings.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
ES-A1-1 SR ES-A1 has specific definitions of which The description provided in the CNP Fire PRA (From peer review:
fire initiating events need to be included, defined in Component Selection report (calculation PRA- Met at CC-I-II terms of initiators that cause automatic scrams, FIRE-17663-002-LAR), Section 3.4.1, has Suggestion) manual scrams per procedure, or LCO shutdowns been updated to show how the internal events under certain conditions. The Fire PRA Component PRA initiating event analysis meets the RAI not needed.
Selection report (PRA-FIRE-17663-0002) simply requirements of the combined PRA Standard references the internal events PRA initiating events SR ES-A1 (Chapter 4, Fire). Staff sees that the DC Cook Fire PRA analysis, without saying how (or even if) the criteria Component Selection report (PRA-FIRE-used there to identify internal initiators are consistent 17663-002-LAR) was updated to show how with Fire PRA SR ES-A1. internal events initiators were considered in equipment selection. Tables 3.4.1-1 through Basis for Significance: If the internal events PRA 3.4.1-5 indicates explicitly how internal event initiating events analysis satisfies the requirements initiators were dispositioned in the Fire PRA 21-Oct-11 4
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings for HL-IE-A, then it should be consistent with Fire including which events were not included.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
ES-B1-1 Internal events systems were excluded from The sensitivity studies performed at the start of (From peer review:
inclusion in the FPRA model based on sensitivity the fire PRA were performed again just prior to Met at CC-II results generated from a scoping fire PRA (17663- submittal of this LAR using the new full scope Suggestion) 002 calculation, Table 3.4.2-1). This sensitivity has fire PRA. These sensitivity studies are not yet been repeated with the full scope fire PRA. documented in the Uncertainty/Sensitivity RAI not needed.
calculation (PRA- FIRE-17663-015-LAR) and Basis for Significance: Confirmation of conclusions were performed to confirm conclusions The sensitivity studies performed again just produced from initial scoping sensitivity produced from the scoping fire PRA. prior to submittal of the LAR using the full scope fire PRA and is documented in DC Cook Fire PRA Uncertainty and Sensitivity Analysis (PRA- FIRE-17663-015-LAR).
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
ES-B2-1 MSO scenarios were generally well defined, The three specific issues noted in the fire PRA (From peer review:
but there were three issues identified: 1. Loss of the peer review Finding were addressed with fault Met at CC-II running charging pump on spurious closure of one of tree changes, and are documented in the Fire- Finding) two VCT outlet valves is identified as a fire-induced Induced Risk Model calculation (PRA-FIRE-spurious failure for loss of RCP seal injection. 17663 LAR). Additionally, two general RAI not needed.
However, the failed status of the pump is not issues associated with this Finding were transferred to the HHI fault tree if the scenario results addressed. The first was to review the Fire During the audit the licensee stated that the in RCP Seal LOCA. 2. Failure to trip the RCPs is PRA modeling to ensure that equipment three issues specially noted in the peer modeled for impact on RCP seal leakage following failures leading to consequential events such review Finding were addressed with fault tree loss of RCP seal cooling. However, it does not as Loss of RCP Seal Cooling and Loss of changes, and are documented in the DC appear that spurious re-start of the RCPs was Offsite Power were properly reflected in the Cook Fire-Induced Risk Model report (PRA-considered. 3. Spurious closure of both the charging fault trees of the CNP fire-induced risk model. FIRE-17663 LAR). Staff found MSO pump discharge valve (QRV-251) and the miniflow The second general issue was to review the consideration of spurious closing of the valve on the running pump (QMO-225 or QMO-226) current industry guidance from NEI regarding charging pump discharge valve, QRV-251, could result in pump failure. This is identified as PWR identification of MSO scenarios, specifically to and mini- recirculation valves, QMO-225 and 21-Oct-11 5
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings generic scenario 51 in NEI 00-01, Rev. 2, Appendix ensure that subtle variations between 226, on pages 142, 144, 249 and 250.
G, but does not seem to have been addressed in the scenarios have been covered in the CNP fire Evidence of the other two changes could not Cook MSO Expert Panel. PRA. The CNP MSO Expert Panel report be identified from this report as it does not (calculation PRA- FIRE-17663-002-LAR), has provide the fault tree logic. The licensee also Basis for Significance: The identified issues are not been updated to reflect this review. points out that fire modeling was reviewed to expected to significantly affect the results because of be sure it was appropriately reflected in the the availability of four pumps to fulfill the HHI function fault trees and industry guidance on MSO and the expectation that the cables associated with was reviewed. Review of industry guidance spurious re-start of the RCPs are also associated of MSOs is evidenced in Attachment B of the with failure to trip. However, this is identified as a DC Cook MSO Expert Panel report (PRA-finding because it could not be determined if FIRE-17663-002b-LAR).
additional cases of the same issues exist that could Even though staff could not find evidence of be more significant. all updates asserted, given the low significance of the issues and the allowance that there may still be minor inconsistencies across supporting documents we found no need for additional information.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
ES-D1-1 While documentation in Calculation 17663- The updated CNP fire PRA Component (From peer review:
002 was sufficient to support peer review, the Selection report (calculation PRAFIRE- 17663- Met at CC-I-III following minor issues were identified: 1. Treatment 002-LAR) was reviewed to ensure it reflects Suggestion) of interlocks and power supplies is not specifically changes that were made during updates to mentioned in 17663-002. For MOVs and pumps, related fire PRA tasks such as development of RAI not needed.
these appear to have been treated as within the the Plant Response Model (calculation primary component boundary and picked up in the PRAFIRE- 17663-005-LAR), the multiple Staff sees that DC Cook PRA Component cable selection. 2. Tables C-1 and C-2 list the spurious operation expert panel, and detailed Selection report (PRAFIRE- 17663-002-LAR) applicable WinNUPRA basic event name is entered HRA (calculation PRAFIRE- 17663-012-LAR). was updated to include treatment of power as "see 1- RCP-ALL" or "see 2-RCP-ALL." The fault Additionally, a description of the treatment of supplies and explains treatment of interlocks tree models incorporate discrete basic events for interlocks and power supplies considered (see Section 4.0). The license asserts that each RCP breaker (e.g., 1ABCB----- 1B9FAF, within the boundary of the primary component the PRA Component Selection report was 1AACB-----1C2FAF). 3. Tables C-1 and C-2 do not was added to The updated CNP fire PRA reviewed to make sure it contained changes contain disposition remarks for 1-XSO-315, 1- XSO- Component Selection report (calculation PRA- resulting from updates to other fire PRA 21-Oct-11 6
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings 325, 2-XSO-315, and 2- XSO-325. These FIRE-17663-002-LAR). updates. However, in checking for update of dispositions were found in the UNIT-1-2-SSEL+PRA issue #3 of the peer review comment (we COMPS.xls file provided during the review. 4. The were told during the Nov. 2011 audit that correlation between HEPs identified in Table 3.4.5-1 disposition remarks for 1-XSO-315 and X-and the instrumentation listed in Table 3.4.5-2 could XSO-325 had been added), we could not find be improved. As currently formatted, it is hard to that this update had occurred. None-the-determine which instruments were added to support less, given the insignificance of this issue each HEP. 5. The process described in 17663-002 and the allowance that there may still be for identification of components to address multiple minor inconsistencies across supporting spurious operation concerns does not match the documents staff found no need for additional expert panel process used. There is also no information.
reference to the Multiple Spurious Operations Expert Panel Final Report. Given the additional information the NRC staff finds this deficiency has been Basis for Significance: These issues do not affect the appropriately resolved by the licensee.
analysis results.
CS-A2-1 New MSO scenarios produced from an The update to the MSO Expert panel has been (From peer review:
update of the MSO Expert Panel have not yet been incorporated in the detailed circuit analysis task Met at CC-II incorporated into the cable selection analysis. effort/evaluation. The evaluation addresses Finding) multiple cable failure mode to support the new Basis for Significance: Potentially significant impact MSO scenario, and also addresses multiple RAI not needed.
to the FPRA risk profile. concurrent cable failures. (But related RAI against FSS-A2- 1 was written to address multiple cable failure issue)
During the audit the license stated that results of an update of the MSO Expert Panel were incorporated into the cable selection analysis. Staff sees that DC Cook PRA Component Selection report (PRAFIRE-17663-002-LAR) dated August 29, 2011 explains on page 9 how the results of the Expert Panel were incorporated and references the DC Cook MSO Expert Panel report (PRA- FIRE-17663-002b-LAR) dated 21-Oct-11 7
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings August 20, 2011 Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
CS-A9-1 No specific discussion is provided in the Fire PRA Cable Selection and routing tasks are (From peer review:
Fire PRA Cable Selection/Cable Routing report about performed using guidelines from NEI 00-01, Met at CC-I-III how proper polarity hot shorts on ungrounded DC NUREG 6850 and a procedure developed to Suggestion) circuits are considered by the model. provide specific guidelines in performing these tasks, the procedure developed discusses how RAI not needed.
Basis for Significance: Documentation enhancement proper polarity hot shorts on ungrounded DC circuits are considered in the model. Additional The licensee points out that guidance to the guidelines in these references, the documents, NEI-00-01 and NUREG-6850, detailed circuit analysis evaluation also provide guidance on proper polarity for discusses the proper polarity on ungrounded ungrounded shorts. Staff sees also that DC circuits. guidance on proper polarity for ungrounded shorts is provided in Detailed Circuit Analysis (TE R1900-0049-0001) on page 7.
Given the additional information, the NRC staff finds the disposition to the F&O to be acceptable.
CS-B1-1 Any additional circuits and cables Technical Evaluation 12.5 identifies power (From peer review:
associated with the identified potential associated supplies that could have potential associated Not Met at CC-I-III circuits issues have not been identified. circuit issues (common power supply and Finding) common enclosure). These power supplied are Basis for Significance: FPRA plant response model being addressed under new technical does not address associated circuits issues evaluation to show that they will not have RAI submitted as SSD RAI-15(a) and 15(b) potential associated circuits issues.
Technical Evaluation 12.5 (not published 21-Oct-11 8
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings until September 26, 2011) is specifically devoted to associated circuit issues by common power supply and common enclosure. It identifies deficiencies in protection DC power supply cables, associated with 4KV switchgear and concludes (in Attachments 4 and 5) that secondary fires cannot be precluded. Also, Technical Evaluation AEPDCC-11-001 addresses the coordination of certain panels not addressed in Technical Evaluation 12.5.
A follow up report, Secondary Fire Evaluation (Technical Evaluation 12.5.1), addresses the secondary fire issue for 125 DC circuits and concludes that the location of postulated secondary fires will not affect post fire safe shutdown.
However, it is not clear that Technical Evaluation AEPDCC-11-001 addresses the secondary fire issues for several 250 DC circuits identified in Attachment 4 of Technical Evaluation 12.5, pages 65 through 68.
The responses provided to RAI-15(a) in a letter dated April 27th 2012 stated, based on review, that despite failures that could lead to secondary fires that fires in credited NSCA equipment or cables would not occur. The response provided to RAI-15b in a letter dated August 9th 2012. Determined that fuses for a number of 250 V DC circuits should be replaced with fuse of a lower current rating to provide assurance that 21-Oct-11 9
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings secondary fires would not occur in these circuits and has implemented compensatory measures that will remain in place until these fuses are replaced and has also committed to perform applicable modifications if a potential for secondary fires in other types of circuits is identified (see SE Section 2.8, Table 2.8-1: Modification S-2.3). Based on the licensees commitment to resolve the secondary fire concerns with modifications the NRC staff finds that not specifically meeting SR CS-B1 is acceptable for this application. Once the modifications are in place, the finding will be resolved.
CS-C1-1 The Fire PRA Cable Selection/Location Technical Evaluation R1900-0043-0001 -"Fire (From peer review:
provides a table of location data on a cable-by-cable PRA Cable Selection and Routing" has been Met at CC-I-III basis. To facilitate the understanding of fire impacts updated to show the cable compartment Suggestion) on a compartment basis, consider adding a table of location(s) for cables.
compartment-by-compartment cable locations. RAI not needed.
Basis for Significance: Documentation enhancement Staff sees that Table 1 in Fire PRA Cable Selection and Routing (Technical Evaluation R1900-0043-0001) shows all Fire Zones all the cable routing for a given cable.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
CS-C3-1 Section 4.0, Uncertainty, of R1900-004-003 There were no instances where the engineer(s) (From peer review:
R0 Fire PRA Cable Selection/Location identifies routing a cable were not able to determine any Met at CC-I-III issues on the routing of trays and conduits due to fire zone for the cables raceways, i.e. there Suggestion) drawing legibility issues. In some cases previous were no instances where the engineers used drawing revisions were available to review and an engineering judgment in the entire cable RAI not needed.
provided insight, if not positive identification. For the route. In cases where the engineer preparing remaining cases, the engineer assigned to t routing the cable route or the engineer reviewing the The licensee clarified during the audit and in 21-Oct-11 10
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings task applied their judgment assigning a fire zone route applied judgment it was discussed with the F&O disposition that the fire zones location to the cable. This engineering judgment was CNP design personnel to verify the required cables were routed through were in all cases based on the last known raceway or conduit location fire zone information. verified with design personnel.
positively identified on a layout drawing.
Based on this explanation, the NRC staff Basis for Significance: The discussion in Section 4.0, finds the disposition to the F&O to be Uncertainty, implies that the routing of some acceptable.
population of trays and conduits could not be verified; however, discussion with those responsible for determination of the routings expressed a high level of confidence in the accuracy of the routings determined.
CS-C4-1 Circuits/cable related to associate circuits Technical Evaluation 12.5 identifies power (From peer review:
concerns have not been included in the Associated supplies that could have potential associated Met at CC-I-III , although Table V-1 Table Circuits by Common Power Supply and by Common circuit issues (common power supply and shows this as Open Enclosure, Rev. 0 reports. Also, no reference is common enclosure). These power supplied are Suggestion) provided to this report from the Fire PRA Cable being addressed under new technical Selection/Location document. evaluation to show that they will not have RAI not needed.
potential associated circuits issues.
Basis for Significance: Documentation enhancement Staff sees that Technical Evaluation 12.5 (not published until September 26, 2011) is specifically devoted to associated circuit issues by common power supply and common enclosure. It identifies deficiencies in protection DC power supply cables, associated with 4KV switchgear and concludes (in Attachments 4 and 5) that secondary fires cannot be precluded. Also, Technical Evaluation AEPDCC-11-001 addresses the coordination of certain panels not addressed in Technical Evaluation 12.5.
A follow up report, Secondary Fire Evaluation (Technical Evaluation 12.5.1), addresses the secondary fire issue but concludes that the location of postulated secondary fires will not 21-Oct-11 11
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings affect post fire safe shutdown.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
CS-A11-1 Section 4.0, Uncertainty, of R1900-004- There were no instances where the engineer(s) (From peer review:
003 R0 Fire PRA Cable Selection/Location identifies routing a cable were not able to determine any Met at CC-I-III issues on the routing of trays and conduits due to fire zone for the cables raceways, i.e. there Suggestion) drawing legibility issues. In some cases, previous were no instances where the engineers used drawing revisions were available to review and an engineering judgment in the entire cable RAI not needed.
provided insight, if not positive identification. For the route. In cases where the engineer preparing remaining cases, the engineer assigned to the the cable route or the engineer reviewing the During the audit the licensee clarified that the routing task applied his judgment in assigning a fire route applied judgment it was discussed with fire zones cables were routed through were zone location to the cable. This engineering CNP design personnel to verify the required in all cases verified with design personnel.
judgment was based on the last known raceway or fire zone information.
conduit location positively identified on a layout Based on this explanation, the NRC staff drawing. finds the disposition to the F&O to be acceptable.
Basis for Significance: The discussion in Section 4.0, Uncertainty, implies that the routing of some population of trays and conduits could not be verified; however, discussion with those responsible for determination of the routings expressed a high level of confidence in the accuracy of the routings determined.
PRM-B2-1 Specific open F&Os from the 2001 peer The internal events PRA has developed and (From peer review:
review were identified that are judged to potentially documented resolutions for the C-level F&Os Not Met at CC-I-III impact the FPRA plant response model: 1) that could adversely affect the development of Finding)
Observation TH-5 (Sub-Element TH-4) -CEQ fans the Fire PRA plant response model. Resolution are excluded from the hydrogen control evaluation of SY-17 addresses all credited cross-ties. This RAI submitted as RAI-34(a) for LERF estimation with no clear basis. 2) review has been documented in calculation file Observation SY-17 (Sub-element SY-17) -Cross-tie PRA-FIRE-17663-005-LAR. LAR Table U-1 shows several Level-C F&O for AFW from Unit 2 does not consider the need for to still be open, including TH-4 and SY-17, AFW at Unit 2 (e.g., prior or concurrent trip of the (with proposed resolutions). RAI-34(a) asks opposite unit), and 3) No apparent documented basis to describe how the resolutions of open 21-Oct-11 12
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings for sufficient bottles air supply inventory for PORV F&Os from the 2001 internal events peer operation for the 24-hour mission time. review were incorporated into the fire PRA.
Include in the response specifically how the Basis for Significance: Potential impact to the FPRA three cited open F&Os in PRM-B2-1, judged risk profile to have significant potential impact to the FPRA risk profile, were addressed.
The response submitted for RAI-34(a) in a letter dated August 9th 2012 specifically provides dispositions for these open F&Os.
In one case the PRA model was modified in response. In the other two cases adequate justification for not changing the model was provided.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
PRM-B9-1 A review of calculation 17663-0005 The fire-induced risk model was reviewed. (From peer review:
Appendix B1, Table B-1 revealed that some items Calculation PRA-FIRE-17663-005-LAR was Met at CC-I-III noted as included in fault tree modifications were not, updated to ensure that the changes identified Finding) in fact, incorporated. These include: 1. For valves 1- were correctly incorporated into the FPRA and IMO-262 and 263, it is stated in the "How component adequate justifications were developed for any RAI not needed.
is included in FPRA" column that basic events fire-induced impacts that were not modeled.
1FAMV--IMO262CSF and 1FAMV--IMO263CSF Also, the FPRA development team reviewed During audit the licensee confirmed that the were added to the 1HPI fault tree. The MSO Expert the FPRA to ensure that MSO Expert Panel fire induced risk model and the DC Cook Fire Panel Report noted that "Spurious opening/ or was properly modeled and the modeling is PRA Fire-Induced Risk Model report (PRA-closing of minimum flow recirc lines for AFW, SI, consistent with that in the internal events PRA. FIRE-17663-005-LAR) were reviewed to CHP, RHR is modeled in fire PRA as in the internal ensure all updates were appropriately and events PRA, with the same success criteria." consistently incorporated. Staff checked Spurious closure of these valves was modeled in the Appendix B, page 121 and can see that 1-internal events PRA because control power is IMO-262 and 1-IMO-262 are shown as in the removed from the valves by a switch in the control fire PRA WinPRA model. With regard to room. However, it is possible that a fire- induced disposition of MSOs: we found that the circuit failure could result in a hot short bypassing disposition of each MSO is provided (added) 21-Oct-11 13
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings this switch. Spurious closure of these valves in in the Section 6.3 evaluation tables as the combination with spurious start of the associated SI Status of MSO Evaluation in PRA Task 2 pump could result in pump failure if RCS pressure is entry.
high. 2. For 1-TCSE, it is stated in the "How component is included in FPRA" column says "added Given the additional information the NRC CFF failure to 1T11A and 1T11D where appropriate." staff finds this deficiency has been However, these events were not added to the appropriately resolved by the licensee.
applicable fault trees. The justification for not including the cooling fan failures was that the fans have an alternate power supply from the supported transformer. Therefore, the cooling is considered within the transformer boundary.
Basis for Significance: Omission of failure modes identified in the equipment selection and MSO expert panel without adequate justification may impact the results. Although the identified items are not expected to significantly impact the results, there may be additional items not identified by the review team that could be significant.
PRM-C1-1 Several documentation issues were The fire PRA development team corrected the (From peer review:
identified in Calculation 17663-0005: 1. In Table B-1 identified documentation issues and reviewed Met at CC-I-III the basic event IDs associated with component 12- Tables B-1 and B-2 to ensure that the Suggestion)
CRV-51 is given as 1D0AV-12CRV51OSF. It modeling notes reflect the current fire PRA appears that the correct ID should be 0D0AV- resolution. The fire PRA plant response model RAI not needed.
12CRV51OSF. 2. In Table B-1, the remarks for is documented in calculation file PRA-FIRE-component 1- QCM-250 note that "per RCB event no 17663-005-LAR. Staff checked the typographical errors and longer considered to fail TBC." The review team was documentation deficiencies in the DC Cook told that this disposition has been formally Fire PRA Fire-Induced Risk Model report documented. The remarks should be updated to (PRA-FIRE-17663-005-LAR) and they provide this more formal reference. 3. In Table B-2 appear to be corrected as indicated in the the basic event associated with component 12-CRV- disposition. For example the basic event 51 is given as 2A0CB----21BDCSF. It appears that name associated with 12-CRV-51 has been the correct ID should be 0D0AV-12CRV51OSF. 4. corrected to OD0AV-12CRV51OSF in Appendix A Tables 4-2, 4-4, and 4-8 lists the mission Table B-1 and Table B-2, and the remarks 21-Oct-11 14
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings time for Bleed and Feed as 0.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. It appears that associated with 1-QCM-250 in Table B-1 had the systems to support Bleed and Feed are modeled been improved. Also, the list of Small LOCA for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and that this is the correct mission time. contributors presented in Sections 4.2.3 of If 0.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> is considered the correct mission time, Appendix A was been updated to include the basis needs to be provided. 5. The list of items RCP seal LOCA and is now consistent with included in the small LOCA initiator in Appendix A Section 4.2.1. On the other hand the mission Section 4.2.1 includes "RCP seal LOCA caused by time of 0.5 for Feed and Bleed presented in failure of RCP cooling without reactor trip." This is not Appendix A, Tables 4.2, 4.4, and 4.8 has not listed in Section 4.2.3 in the top event description for been changed or justified (that we could Small LOCA. 6. The description of top event SBO in find). However, given that the peer reviewer Appendix A Section 4.1.4 discusses the fact that states that the modeling related with the availability of the turbine-driven auxiliary feedwater seven cited issues appears to be correct, pump impacts the time to perform manual cross- ties. staff judges the significance of not However, it is not clear from the wording that the addressing all seven documentation issues turbine-driven AFW pump and cross-ties are as not important enough to pursue with an modeled within the SBO fault tree. 7. Calculation RAI.
17663-0005 Appendix A Section 4.1.4 says in the description of top event RCP-1 that the Given the additional information the NRC "Westinghouse seal LOCA model identifies three staff finds this deficiency has been distinct seal LOCA sizes, 21 gpm/pump, 182 appropriately resolved by the licensee.
gpm/pump, and 480 gpm/pump." WCAP-16141 actually identifies four seal leakage rates of 21 gpm/pump, 76 gpm/pump, 182 gpm/pump, and 480 gpm/pump. It appears that the probability of the 76 gpm/pump leakage rate (.01) has been combined with the 21 gpm/pump leakage probability. Since there is no difference in the mitigation requirements for all leakage rates between 21 gpm/pump and 182 gpm/pump, this is considered to be only a documentation issue.
Basis for Significance: The modeling for all of the identified items appears to be correct. Therefore, these issues are not expected to affect the results.
21-Oct-11 15
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings PRM-B11-1 No comprehensive review has been A comprehensive review was conducted to (From peer review:
made of all sequence-specific internal events HEPs identify sequence-specific internal events Met at CC-I-III to see whether these variations need to be reflected human failure events and has been Suggestion) in the FPRA model. documented in calculation file PRA- FIRE-17663-012-LAR (HRA). RAI not needed.
Basis for Significance: No significant impact to risk profile is anticipated. This is judged to be primarily a A comprehensive review of internal events documentation issue. human failure events that should be included in the Fire PRA appears to be part of the process to identify and incorporate human errors into the Fire PRA and is described in DC Cook Fire PRA Human Reliability Analysis report (PRA-FIRE-17663-0012-LAR). Section 3.4 of that report specifically identifies human error events from the internal events PRA were used as input to the Fire PRA HRA process. Staff notes the late completion date of 17663-0012-LAR:
October 31, 2011.
Given the additional information, the NRC staff finds the disposition to the F&O to be acceptable.
FSS-A2-1 The assessed capability category for this The treatment of fire induced spurious (From peer review:
item is "Not Met". The methodology that is described equipment operations was upgraded to Not Met at CC-I-III indicates that all cables whose fireinduced failure address the potential cases where multiple Finding) could adversely affect a credited component are concurrent cable failures could occur and identified. This is true for both functional failure cause undesired equipment operations. RAI submitted as RAI 34(b) concerns as well as spurious actuation (operation) concerns. The issue arises due to the process that is This F&O was written as being closely used whereby the spurious threats are propagated associated to SR CS-A2 which requires that into the Fire PRA. The process as implemented fire-induced spurious operations from TWO results in spurious events being evaluated based on cables be considered. During the trip the a single cable failure. Instances where the concurrent licensee explained that after the peer review failure of more than one cable is required are not comment an effort was undertaken to 21-Oct-11 16
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings currently addressed in the Fire PRA. This includes explicitly consider and document the impact instances where the set of cables co-exist in the from TWO cables. The licensee showed same raceway. The treatment of this SR is closely how extra columns had been added to Table related to CS-A02. In order to meet FSS-A2, the 3-7 of PRA-FIRE-17663-010. Staff asks an propagation of the failure combinations must be RAI to Describe how the treatment of fire-consistent. The treatment needs to include in the induced spurious equipment operations was grouping of riskrelevant targets the cables supporting upgraded in any identified circuits where hot shorts impacting up response to FSS-A2-1 to address potential to and including two cables (including both intracable multiple concurrent cable failures and cause and intercable hot shorts) could lead to spurious undesired equipment operations. [And also operation of selected equipment. ask to] Specifically address in the response how two cables that if affected and could Basis for Significance: A review of the information cause spurious operations were considered.
provided in Table 3-6 of FIRE-PRA-17663-0010 coupled with discussions with the utility team In the response to RAI 34(b) in a letter dated concluded that the determination of whether a August 9th 2012, the licensee describes the spurious event occurs relies on the entry in columns upgrade performed in response to the F&O.
for those events. Unfortunately, there are other The licensee explained that first each cable instances where the concurrent failure of multiple was evaluated one at a time to determine if it cables is required to cause the upset state. These could spuriously actuate, then cables were instances are identified via a discussion in another examined in pairs to determine if a pair could column in the table. Consequently, these discussions spuriously actuate. As a result of the F&O were not considered in the development of the the licensee reviewed their assessment and damage set and therefore, the damage set effectively improved the documentation. A column was is limited to only those spurious events that result added to the cable analysis table in the from a single cable failure. Higher order cable Detailed Circuit Failure Analysis report failures are implicitly treated as not being credible. (R1900-049-0001) title Spurious Multiple Examples include 1-CMO-419, 1-CMO-429, 1- ICM- Concurrent Failures to further clarify whether 305, and 1-ICM-306. It is anticipated that additional a cable was multiple concurrent failure cases may arise as a result of the update of the contributors. Example entries are provided related report to incorporate changes as noted in in the response.
other F&Os (MSO Expert Panel).
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
21-Oct-11 17
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings FSS-A2-2 PRA-FIRE-17663-0011a, CNP Fire PRA The correlation between two documents "PRA- (From peer review:
detailed Fire Quantification of Individual Areas. The FIRE-17663-0011a, CNP Fire PRA detailed Not Met at CC-I-III report identifies those scenarios where burnup was Fire Quantification of Individual Areas" and Suggestion) acceptable and, where not acceptable, and it "Task 4.11, Detailed Fire Models" was provides a correlation to the Detailed Fire Models established for the few discrepancies and RAI not needed.
conducted as part of Task 4.11. As a sample, Fire review conducted for other detailed fire models Modeling Report AA3, (R1900-003-AA3), was to ensure that this is an anomaly. During the audit the licensee explained that reviewed to verify the correlation. There was a good the current version of the DC Cook Fire PRA correlation between the two, except for an instance Detailed Fire Quantification of Individual where Fire Zones were listed as acceptable with full Areas PRA-FIRE-17663-0011a,) carries all room burnup and with detailed scenarios conducted. Fire Area scenarios forward to quantification even if they were very small contributors to Basis for Significance: This appears to be a minor the CDF. Therefore, inconsistency between issue since the CCDP and CDF values were identical PRA-FIRE-17663-0011a, and Fire Modeling between the burnup and fire modeling scenarios. Report AA3, (R1900-003-AA3) no longer existed. Staff notes that, in fact, no quantification screening was performed at all.
Staff confirmed that scenario CDFs for all Fire Areas, including AA3, are presented in table 3-3 of PRA-FIRE-17663-0011a (see pages 22 thru 27 for AA3).
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
21-Oct-11 18
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings FSS-A6-1 Fire Scenarios for the Unit 2 MCR are not The Unit 2 MCR fire quantification was (From peer review:
complete. completed using the methodology used for Unit Met at CC-I/II
- 1. This is described in calculation PRA-FIRE- Finding Basis for Significance: Methodology is established. 17663-0010b-LAR.
However, specific risk for Unit 2 MCR is not RAI not needed.
identified.
The MCR fire quantification approach and CDF and LERF results are presented in the DC Cook Fire PRA Main Control Analyses report (Unit 1 and Unit 2] (PRA-FIRE-17663-001b-LAR). For example CDF and LERF for Unit 2 is presented in Tables 28 and 19.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
FSS-A6-2 The Fire PRA treatment of the Main The MCR analysis was revised, and the two (From peer review:
Control Room basically divides the analysis into a cases identified during the peer review were Met at CC-I/II limited number of cases. In general, there are two evaluated. The results were incorporated into Suggestion) specific considerations that do not appear to have calculation file PRA- FIRE-17663-011b-LAR.
been specifically included or addressed. One RAI submitted as RAI-29 involves a postulated fire in the panel section that contains the Main Control Room ventilation system In response to RAI 29.01, the quantification controls. The analysis of this panel section does not of main control room scenarios was address the consequential failure of the ventilation expanded to include modeling of human system. The treatment applies a node probability of error probabilities to respond to scenario-0.10 for the random failure of the system. The other specific equipment damage. The HEPs for consideration that does not appear to have been all ex-control room actions were re-evaluated addressed is whether the postulated progression of using the most recent feasibility analysis the fire event at a particular panel section would performed as an input. The operator actions result in an event progression that could not be were evaluated using the detailed human mitigated using features and controls available via reliability analysis quantification, per Section OHP-4025-001. The current treatment assumes that 5.3 of NUREG-1921. The results of the re-a screening HEP of 0.10 can be applied to all evaluation showed an increase in delta risk abandonment cases. The potential that a fire at a greater than the acceptance guidelines of 21-Oct-11 19
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings panel could put the plant into a configuration that RG 1.205. The licensee will include the would require functions and controls not available via modification to the reactor coolant pump OHP-4025 should be evaluated using an HEP of 1.0. seals as a committed modification in Table S-2 of the LAR to reduce the delta risk to Basis for Significance: A cursory review of the MCR within the RG 1.205 guidelines. Based on results indicates that incorporation of the issues the licensees response to RAI 29.01 the noted herein would not results in a significant impact staff and the crediting of the reactor coolant to the quantification totals for the MCR. pump seal modification, the NRC staff finds the disposition of this F&O to be acceptable.
FSS-C2-1 In order to meet CII/III, CHARACTERIZE The Detailed Fire Modeling Procedure, EPM- (From peer review:
ignition source intensity using a realistic time- DP-FP-001, has been updated to reflect the Met at CC-I/II dependent fire growth profile (i.e., a time-dependent correct duration used to reach peak HRR for Suggestion) heat release rate) for significant contributors as transient fires. Transient fires were extended to appropriate to the ignition source. There is an 60 minutes per FAQ-0052. The duration of RAI not needed.
inconsistency in the time to reach peak HRR for unconfined oil fires, while conservative, did not transient fires (6 minutes per the procedure vs. 8 result in any oil fire scenario becoming a A spot check during the audit revealed that a minutes per the modeling reports). There is also significant risk contributor, and therefore, no in a number of cases the duration used to insufficient justification for the duration of both changes were made. reach peak HRR for transient fires was transient and unconfined oil spill fires. extended to 60 minutes per FAQ 0052 as asserted by the licensee (e.g., DC Cook Fire Basis for Significance: There is an inconsistency in Risk Evaluation - Fire Area AA50, page 41, the identification of duration to reach peak HRR for Attachment 6), confirming the F&O transient fires in EPM-DP-FP-001 R1 (6 minutes) and disposition.
the detailed fire modeling reports (8 minutes). Eight minute duration is consistent with FAQ 08-0052. The Given the additional information the NRC 40-minute transient fire duration for transient fires in staff finds this deficiency has been the detailed modeling reports has not been justified appropriately resolved by the licensee.
relative to the up to 60-minute duration in FAQ 08-0052. The duration of unconfined oil spill fires (20 minutes) in the detailed fire modeling reports is very conservative when compared against typical durations from NUREG 1805 spreadsheet applications.
FSS-C3 (From V-2 Table) Updates made to the Fire PRA in response to (From peer review:
F&O FSS-C2-01 have incorporated appropriate Met at CC-I 21-Oct-11 20
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings (There is no F&O associated with this SR. However, justification for heat release rate profile stages Not an F&O)
Table B-6 of the fire PRA WOG Peer Review SR and the SR is now considered to meet Cat II/III.
Assessment Table reads that: While a more RAI not needed.
realistic treatment of fire growth behavior is used with fire decay times identified, there is a lack of Staff found this issue to be similar to this justification for the times used. CC-I was identified F&O against FSS-C2. A spot check during since sufficient deficiencies were found with the the audit revealed that a in a number of times used (40 minutes for transients when cases the duration used to reach peak HRR FAQ-0052 indicated durations of up to 60 minutes, for transient fires was extended to 60 and a 20-minute fire duration for an unconfined oil minutes per FAQ 0052 as asserted by the fire where such fires would have a duration of not licensee (e.g., DC Cook Fire Risk Evaluation more than one minute) that the key.) - Fire Area AA50, page 41, Attachment 6),
confirming the F&O disposition.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
FSS-C5-1 Damage thresholds are based on The Fire PRA has been updated and revised to (From peer review:
thermoset cable thresholds. It is known that include impact of thermoplastic cable Met at CC-I/II thermoplastic cables are installed, and the impact is installations and to address solid- state Finding) being reviewed. Also, solid state components are components.
documented in the detailed fire modeling reports at RAI not needed.
the higher thermoset damage thresholds.
Cable damage was completely reevaluated Basis for Significance: Use of a higher damage in Technical Evaluation 11.64, Rev 0, Cable threshold can result in misidentification of failures. Material Impact Review, dated Nov. 2010.
However, the issues are understood and being This effort re-identified the cables types and pursued. In the case of solid-state components, quantity of thermoplastic cable and address NUREG 1805 spreadsheets (FTDs) have been run to solid state components. During the trip the determine if damage does occur at the lower licensee explained that the original analysis thresholds. was performed in 2009 before the Sandia results showing greater damage for thermoplastic cable.
Staff checked a number of fire modeling 21-Oct-11 21
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings reports (e.g., CNP, Detailed Fire Modeling Report - Fire Compartment: AA50, R1900-0411-AA50) and can see this re-evaluation referenced in Section 5.5.2, and see cable classifications with respect to thermoset and thermoplastic cables listed in Attachment 5.
In a related RAI we ask why temperatures for thermoset are used when thermoplastic is identified in Attachment 5 for Fire Area AA57A.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
FSS-C8-1 FSS-C08 requires confirmation that Technical Evaluation 11.57 has been updated (From peer review:
credited wraps are not subject to mechanical to provide objective evidence that credited Not Met at CC-I-III damage or direct flame impingement from high wraps are not subject to damage from high Finding) hazard sources (unless qualified or tested under hazard sources.
these conditions). RAI submitted as RAI-34(c)
Basis for Significance: The detailed fire modeling During the trip the licensee explained that report for AA36/42 indicates that two credited Technical Evaluation 11.57 had been redone raceway wraps are not expected to be subject to to provide objective evidence that credited mechanical damage or flame impingement from high wraps are not subject to damage from high hazards sources, inclusive of HEAF. Walkdown data hazard sources including HEAFs. However, has not been located to confirm lack of damage or only the original Technical Evaluation 11.57, impact. Should such damage or impact occur, the dated Dec 20019, could be located on the cables protected within the raceways could be Viewer or produced during the trip. Staff subject to the environment of postulated fire asked an RAI to describe how the Technical scenarios in the location. Evaluation was updated and to specifically explain how HEAFs were considered.
In response to RAI 34(c) in a letter dated August 9th 2012, the license explains that Technical Evaluation 11.57 was updated to 21-Oct-11 22
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings include objective evidence from walkdowns that credited wraps are not subject to mechanical or heat related damage from hazard sources. This included determining whether a catastrophic transformer or hydrogen explosions could physically impact the fire wrap.
B Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
FSS-D4-1 Detailed fire modeling inputs for cable The Fire PRA has been updated and revised to (From peer review:
trays which have tray covers credit a 20-minute delay remove credit for cable tray covers in locations Met at CC-I-III for damage and ignition. During walkdowns small where cable tray bottoms have small open Finding) holes were noted in some trays bottoms which had holes.
been credited with the 20-minute delay. The impact RAI not needed.
of the tray bottom design with these holes should be evaluated and documented. During the audit the license explained that the credit for the tray bottom covers with Basis for Significance: Delays in ignition and damage holes in them had been removed in the few times could be overestimated. cases where they existed as cited Fire Area AA43 as an example. Staff checked the CNP Detailed Fire Modeling Report - Fire Compartment AA43 (R1900-007-AA43) and found this exception for a handful of cases but in other cases (presumably with no holes in the cover the 20 minute credit is taken).
See pages 9, 10, and 16 concerning riser 2EM-C217.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
FSS-D7-1 CNP fire detection and suppression Cat 1 is acceptable for the application. CNP (From peer review:
analysis has been completed using the approach and considers the estimates of unavailability used Met at CC-I 21-Oct-11 23
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings guidance of NUREG/CR-6850 Appendix P. Plant- in the analysis to be appropriate. Suggestion) specific values for "unavailability" have been estimated and an evaluation for outlier behavior RAI submitted as RAI-34(d).
based on plant information from maintenance activities is being conducted and tracked via a project During the audit the licensee argued that the open item. This evaluation needs to be completed individual RAW values for these and documented to achieve a CC II rating. unavailabilities to be unimportant (i.e. no higher than 1.32). It is not clear what the Basis for Significance: Meets Category I aggregate unavailability might be. Staff asked an RAI to provide rationale for why outlier behavior based on plant information being conducted and tracked through an open project item was not used and why using generic unavailability is acceptable.
The response to RAI 34(d) in a letter dated August 9th 2012, the licensee explained that the evaluation of plant-specific outlier behavior had been completed and that the evaluation shows that the actual unavailable time for fire detection and suppression systems is greater than the generic unavailability value used in the CNP Fire PRA. The licensee provided a sensitivity analysis in Section 3.4.7 using the actual unavailability times indicating the correct values do not significantly impact the risk results in the LAR. Based on staff finds that the PRA is technically adequate with regard to SR FSS-D7 to support the fire risk evaluations and other risk calculations required for the NFPA 805 application. The self-approval acceptance guidelines are much smaller than the transition acceptance guidelines and the NRC Staff concludes that 21-Oct-11 24
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings the correct plant specific fire protection system unavailabilities should be incorporated into the licensee PRA before the quantitative results may be used to support future self-approval. The licensee included updating the PRA to use the plant specific values as implementation item S-3.19 FSS-D8-1 The detailed fire modeling reports, in A discussion of fire protection system (From peer review:
which detection and suppression is credited, should effectiveness has been incorporated into all fire Met at CC-I-III be updated to include a specific section addressing modeling reports. Suggestion) system effectiveness. Currently some data is included in Section 5.2, some is in Attachment 1 and RAI not needed.
some is in Attachment 9. NFPA Code evaluations are complete but not specifically referenced. Staff checked a few detailed fire modeling reports and found a section (Section 5.8.1.1, Basis for Significance: Enhancements Detection Effectiveness Evaluation under Section 5.8.1 Detection Analysis that specifically addresses this concern.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
FSS-E3-1 A sentence in Section 3.3.4.2 of Scientech Section 3.3.4.2 of Scientech report PRA-FIRE- (From peer review:
report PRA-FIRE-17663-0015 stops mid-sentence: 17663-0015-LAR was updated to state the Met at CC-I "Results of sensitivity studies will be documented in" location of the results of the sensitivity studies. Suggestion)
Basis for Significance: This editorial error should be RAI not needed fixed.
More than the Suggestion (i.e., related to the typo) the more important issue here is why the SR is met only at CC-I. Page B-39 of the Fire Peer Review Report (LTR-RAM-II-10-041) indicates that the detailed fire modeling reports present only a qualitative 21-Oct-11 25
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings discussion of uncertainty. In RAI 31 the NRC Staff requested that the licensee perform a statistical propagation of parametric uncertainty and assess the impact on the risk results presented in the LAR. Finding UNC-A1-1 on SR UNC-A1 noted that the licensee had not performed a propagation of parametric uncertainty through the PRA model. In response to the RAI (Reference
- 10) the licensee provided a sensitivity analysis in which PRA model parameters having distributions were statistically propagated in the CNP Fire PRA model. The sensitivity analysis results show that propagating the parametric uncertainties through the PRA model could potentially significantly impact the results of decisions because of the little margin available before the proposed CNP RI/PB FPP potentially exceeds the risk acceptance guidelines for Region II (small change) in RG 1.174. See Section 3.4.7 of this SE for the NRC staffs evaluation of this sensitivity study.
Consequently, the NRC staff finds that the PRA is technically adequate with regard to SR UNC-A1, and associated SR QU-E3, to support the fire risk evaluations and other risk calculations required for the NFPA 805 application, and the licensee has demonstrated the capability to a perform the propagation of parametric uncertainty through the PRA model as needed to support future self-approval.
21-Oct-11 26
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings FSS-G1-1 Table 3 of Scientech calculation file The Multi-Compartment Analysis for Areas (From peer review:
17663-011c, Multi-Compartment Analysis, identifies AA2 to AA25 with CDF 1.30e-7 was addressed Met at CC-I-III adjacent areas that did not screen at Steps 1, 2 or 3 in the subsequent stages of the Screening, Suggestion) at a CDF of 1E-7 or less. The non screened areas with the final results provided in a table on are supposed to go onto the next stage. Area AA2 to page 36 of 56. RAI not needed.
AA25 has an identified CDF of 1.30E-7 in Table 3, which exceed 1.0E-7. However, these are not Staff found Scenario AA2-to-AA25 to be addressed in the subsequent stage. Dispositioned in Table 6 on page 29 of DC Cook Multi-Compartment Analysis (PRA-Basis for Significance: The significance of this FIRE-17663-0011cLAR).
multicompartment is low given that Table 3 identifies the CDF of this MCA as 1.30E-7. All other MCAs in Given the additional information the NRC Table 3 did progress to the next stage. This appears staff finds this deficiency has been to be a single instance of incomplete documentation appropriately resolved by the licensee.
of the results of the next stage.
FSS-G2-1 DEFINE screening criteria for For any zone where "whole room burnout" was (From peer review:
multicompartment fire scenarios that provide employed rather than "detailed fire modeling" a Met at CC-I-III reasonable assurance that the contribution of the discussion of the fire barriers was provided to Suggestion) screened physical analysis unit combinations are of justify that a fire can be expected to be low risk significance. The screening criterion, when contained within the single fire zone. RAI not needed.
based on a fire zone to fire zone analysis, is predicated on the results within each zone, and not Staff found discussions of barriers in Table 6 necessarily fire spread between zones, especially and in cases of whole zone burnout. In DC when barriers between zones are credited. Cook Multi-Compartment Analysis (PRA-FIRE-17663-0011cLAR)
Basis for Significance: When a fire scenario was limited to a zone-basis, the approach was to field- Given the additional information the NRC verify the ability of the barriers to contain the fire. staff finds this deficiency has been Appendix A fire barriers, which have been appropriately resolved by the licensee.
incorporated into the fire protection program as Appendix R barriers, form the zone boundaries. The approach is not clearly documented.
21-Oct-11 27
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings FSS-G5 (From V-2 Table) The quantification of scenarios in the multi- (From peer review:
compartment analysis has been reviewed and Met at CC-I (There is no F&O associated with this SR. However, revised to take credit for active fire barriers, Not an F&O)
Table B-6 of the fire PRA WOG Peer Review SR consistent with the changes made in SR PP-B5 Assessment Table: There is no evaluation of above. This documented in calculation file RAI submitted as RAI34(i) normally open fire doors with fusable links. A MCA PRA-FIRE-17663-0011c.
was performed on AA2 to AA25, which are separated There is no finding or suggestion for FSS-G5 by a fusible link held open fire. Refer to FSS-PP-B5 but because PP-B5 was considered CC-I, relative to the evaluation of fusible link held open fire FSS-G5 also assigned to CC-I.
doors in compartment boundaries. Plant Boundary Definition and Partitioning Report Rev. 1, (R1900- During the audit it was explained that further 004-001), Section 4.3, reads: the plant portioning assessment of active fire barriers was analysis at CNP does not credit spatial separation as expanded to include high hazard events (i.e.,
a portioning element in defining physical analysis HEAFs, transformer explosions, and units.) hydrogen explosions) and is documented in the Plant Boundary Definition and Partitioning Report (R1900-0041-001), we ask an RAI to describe how the multi-compartment analysis was revised as a result.
In the response to RAI 34(i) in a letter dated August 9th 2012, the licensee cited the provided a description of assessment of active fire barriers was expanded to include consideration of high hazard events (i.e.,
HEAFs, transformer explosions, and hydrogen explosions) and is documented in the Plant Boundary Definition and Partitioning Report (R1900-0041-001). Staff sees that Section 4.5 (on pages 9 and 10) discusses crediting active fire barriers. All active fire barriers (i.e., fire dampers, held-open fire doors, water curtains) are identified in Attachment 2 of the Plant Boundary 21-Oct-11 28
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings Definition and Partitioning Report.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
FSS-G6-1 In order to meet CII/III, it is necessary to All the Table 5 MCAs were quantified for the (From peer review:
quantify the risk contribution of any selected risk contribution of any selected Met at CC-I multicompartment fire scenarios consistent with FQ multicompartment fire scenarios consistent Suggestion) requirements. with FQ requirements.
RAI not needed.
Basis for Significance: The SR is met. The F&O only provides guidance for meeting CC-II/III. During the audit the licensee explained and staff sees that DC Cook Multi-Compartment Analysis (PRA-FIRE-17663-0011c-LAR) page 48 explains that the MCA was quantified but that the total sum of all MCA scenarios was 4.7E-8/yr which is 0.2% of the total CDF and therefore its contribution was not carried forward into quantification of the total fire CDF.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
FSS-H5 (From V-2 Table) Results Documentation. The fire PRA results (From peer review:
documentation has been updated to reflect Met at CC-I (There is no F&O associated with this SR. However, recent model changes and also to provide Not an F&O)
Table B-6 of the fire PRA WOG Peer Review SR additional information regarding the Assessment Table reads: No documentation of quantification process, to better support Fire RAI submitted as RAI 31 parametric uncertainty analysis. The SR is judged to PRA applications, updates, upgrades and be met at CC-I.) future peer reviews. Staff found that the DC Cook Fire PRA Uncertainty and Sensitivity Analysis (PRA-Parametric Data Uncertainty. Because of the FIRE-17663-015) provides a detailed wide range in modeling choices, such as the t- description of which elements of the Fire squared growth model provided for in PRA that parametric uncertainty was 21-Oct-11 29
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings NUREG/CR-6850, modeling uncertainties drive propagated and accompanying rationale and the fire PRA results insights. The development why in some cases only a qualitative of the parametric data uncertainty treatment was performed. However, Staff characterization provides information that does notes that a statistical propagation of not provide meaningful insights into the parametric uncertainty was not completed decision-making process. Thus, the parametric and so a number of F&Os related to the data uncertainty is not applicable to the NFPA- performance of uncertainty analysis on 805 LAR submittal. The parametric data different elements of the PRA are open.
uncertainty will be accomplished in a future Staff asks an RAI to provide an estimate of update to the fire PRA. In the fire PRA, the the difference between the mean and the endpoints of the fire damage state trees point estimate and the impact this may have represent mean values for each of the fire on risk acceptance.
scenarios. The uncertainty distributions for these fire damage states include the In RAI 31, the NRC Staff requested that the parametric data uncertainty associated with the licensee perform a statistical propagation of ignition frequencies as well as the other branch parametric uncertainty and assess the points on the fire damage state tree. The impact on the risk results presented in the results of this development will be provided in LAR. Finding UNC-A1-1 on SR UNC-A1 an update to calculation PRAFIRE- 17663-015- noted that the licensee had not performed a LAR. propagation of parametric uncertainty through the PRA model. In response to the RAI (Reference 10) the licensee provided a sensitivity analysis in which PRA model parameters having distributions were statistically propagated in the CNP Fire PRA model. The sensitivity analysis results show that propagating the parametric uncertainties through the PRA model could potentially significantly impact the results of decisions because of the little margin available before the proposed CNP RI/PB FPP potentially exceeds the risk acceptance guidelines for Region II (small change) in RG 1.174. See Section 3.4.7 of this SE for the NRC staffs evaluation of this sensitivity study.
21-Oct-11 30
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings Consequently, the NRC staff finds that the PRA is technically adequate with regard to SR UNC-A1, and associated SR QU-E3, to support the fire risk evaluations and other risk calculations required for the NFPA 805 application, and the licensee has demonstrated the capability to a perform the propagation of parametric uncertainty through the PRA model as needed to support future self-approval.
IGN-A7-1 Observation: Calculation 17663-0006 in The bases for 0.1 storage and 0.05 (From peer review:
section 3.4.7.2 assigns a storage weighting factor of maintenance weighting factors were added as Met at CC-I-III 0.1 for plant areas where no storage locations are to they relate to CNP operating experience to Finding) be applied and a maintenance weighting factor of section 3.4.7.2 of calculation file PRAFIRE-0.05 for plant areas where hot work will be prohibited 17663-006-LAR. RAI submitted as RAI 34(e) at power. It is recognized that establishing enhanced administrative controls will reduce the likelihood for The licensee used a special weighting factor the storage of transient materials or hot work in these for apportioning fire frequency for transient areas. However, the specific bases for the reductions fire that deviates from the guidance in used are not documented in a manor that related to NUREG-6850. An RAI was asked to perform CNP specific plant experience. a sensitivity analysis on this deviation.
Basis for Significance: Impacts robustness of the In RAI 34(e), the NRC Staff requested that update process. Bases should be known so this the licensee provide sensitivity analyses in assumption can be included in some type of which the maintenance, occupancy, and monitoring program to ensure changes to plant storage influence factors were each assigned operating experience specific to hot work and values consistent with the guidelines in NRC-transient combustible controls are evaluated. endorsed FAQ 12-0064. In response to RAIs 34e the licensee provided sensitivity analyses in which the maintenance, occupancy, and storage influence factors were each assigned values consistent with the guidelines in NRC-endorsed FAQ 12-0064. See Section 3.4.7 of this SE for the NRC staffs evaluation of these sensitivity 21-Oct-11 31
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings studies. The results of these sensitivity studies by the licensee demonstrate that the risk calculations do not change significantly for this LAR. However, the NRC staff does not find the licensees proposed method to be acceptable because it provided excessive flexibility to distribute transient fire frequency among different plant locations with no technical justification for modifying the acceptable method. In response to RAI 61, the licensee provided an integrated analysis which provided the risk results after changing this, and several other unacceptable proposed methods, to acceptable methods.
Accordingly, the NRC staff concludes that the licensee has demonstrated that the CNP Fire PRA is technically adequate with regard to SR IGN-A7 to support the fire risk evaluations and other risk calculations required for the NFPA 805 application.
However, because the method employed in apportioning transient fire frequency is not acceptable to the NRC, the NRC staff concludes that the NRC-endorsed method in FAQ 12-0064 should be incorporated into the PRA before the quantitative results can be used to support self-approval. The licensee included modify storage and hot work procedures and reflecting these modifications in the PRA in implementation items S-3.3, S-3.4. and 5-3.19 IGN-A7-2 For plant areas where hot work is to be Plant area specific maintenance factors were (From peer review:
prohibited during power operations, a maintenance assigned for bins 7, 25, and 37 as described in Met at CC-I-III weighting factor of 0.05 was assigned. Administrative calculation file PRA-FIRE-17663-006-LAR. Finding) controls would reduce the probability of the transient 21-Oct-11 32
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings hot-work-related bins. However, the reduction has The licensee used a special weighting factor also been applied to Bins 7, 25, and 37 which are for apportioning fire frequency for transient maintenance related transients. Therefore the fire that deviates from the guidance in reduction would not apply. NUREG-6850. An RAI was asked to perform a sensitivity analysis on this deviation.
Basis for Significance: Transient-related ignition frequencies are too low for the affected plant areas.
The response to RAI 34(e) provides a sensitivity study that shows the comparison between three variations of assigning transient fire weighting factors. However, none of the variations match the guidance in draft FAQ 0012-0064.
In response to follow-up RAI 34.01, the licensee provided a sensitivity analysis in which the maintenance, occupancy, and storage influence factors were each assigned consistent with the guidelines in NRC-endorsed FAQ 12-0064. The results of the analysis showed the total CDF and LERF for both CNP Units 1 and 2 remain well below 1E-4/year for CDF and 1E-5/year for LERF.
In addition, the delta CDF and delta LERF for both CNP Units 1 and 2 remain below the risk acceptance guidelines of 1E-5/year for CDF and 1E-6/year for LERF for Region II (small change) in RG 1.174, which is acceptable to the NRC staff.
IGN-A7-3 Fire Influence weighting factor of "0" is Weighting factors were assigned following the (From peer review:
assigned to outside compartments Unit 1 Yard, Unit guidance of Table 3-5 of PRA-FIRE-17663- Met at CC-I-III 2 Yard, and 146 while assessing that transient fires 006-LAR for affected compartments and spatial Finding) will not impact risk important equipment or circuits. separation to subdivide the yard was applied.
However, the basis for this treatment is not explicitly The licensee used a special weighting factor provided in the calculation. Transient fires are for apportioning fire frequency for transient 21-Oct-11 33
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings possible in these outside areas and are not fire that deviates from the guidance in precluded by design. NUREG-6850. An RAI was asked to perform a sensitivity analysis on this deviation.
Basis for Significance: The transient fire risk in the affected compartments may be underestimated.
The response to RAI 34e provides a sensitivity study that shows the comparison between three variations of assigning transient fire weighting factors. However, none of the variations match the guidance in draft FAQ 0012-0064.
In response to follow-up RAI 34.01, the licensee provided a sensitivity analysis in which the maintenance, occupancy, and storage influence factors were each assigned consistent with the guidelines in NRC-endorsed FAQ 12-0064. The results of the analysis showed the total CDF and LERF for both CNP Units 1 and 2 remain well below 1E-4/year for CDF and 1E-5/year for LERF.
In addition, the delta CDF and delta LERF for both CNP Units 1 and 2 remain below the risk acceptance guidelines of 1E-5/year for CDF and 1E-6/year for LERF for Region II (small change) in RG 1.174, which is acceptable to the NRC staff.
IGN-A7-4 Bins 13, 17, and 29 were excluded from The bases for exclusion to the bin descriptions (From peer review:
consideration at CNP. The bases for exclusion has been added, and described in calculation Met at CC-I-III should be added to the bin descriptions in 17663-006 PRA-FIRE-17663-006-LAR. Suggestion)
Section 3.4.6.
RAI not needed.
Basis for Significance: No impact to risk results.
Staff sees that the basis for excluding Bins 13, 17, and 29 was added to Table 5-1 of DC 21-Oct-11 34
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings Cook Fire Ignition Frequency Calculation (PRA-FIRE-17663-006-LAR).
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
IGN-A7-5 Bin 19 was excluded from consideration at Hydrogen systems in fire zones 110 and 111 (From peer review:
CNP. During a plant walkdown of zones 110 and were evaluated and their treatment Met at CC-I-III 111, H2 in 15% concentration cylinders with piping documented in calculation PRA-FIRE-17663- Finding) attached to a plant system was observed. These 006-LAR.
should be addressed in bin 19 or the bases for RAI not needed.
exclusion should be added to the bin description in 17663-006 Section 3.4.6. Staff sees that Bin 19 was included in DC Cook Fire Ignition Frequency Calculation Basis for Significance: Low level risk impact (PRA-FIRE-17663-006-LAR) by attributing 50% of the bin frequency to Room 110 and 50% to Room 111.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
IGN-B1-1 The following issues were noted in Editorial issues as needed were corrected in (From peer review:
Calculation 17663-0006 document: 1) FAQ Table 2-1 calculation PRA-FIRE-17663-006-LAR. Met at CC-I-III does not reflect current status and should be updated Suggestion) to reflect all FAQ's are approved. 2) The spread sheets for Attachments A and B were not attached. RAI not needed.
- 3) Page 18 discussion of weighting factors states the low category is used for no hot work locations when Staff sees editorial suggestions incorporated a plant-specific 0.05 value was actually used. This is into DC Cook Fire Ignition Frequency inconsistent with the page 16 discussion. 4) Calculation (PRA-FIRE-17663-006-LAR)
Numerous locations in the calculation contained an report.
error message relating to a reference; example: pg
- 11. 5) Bin 10 discussion "They are" should be "They Given the additional information the NRC are", 6) Section 3.4.7.2 under transients "hto" should staff finds this deficiency has been appropriately resolved by the licensee.
21-Oct-11 35
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings be "hot",
Basis for Significance: Does not impact risk results.
IGN-B1-2 Calculation 10766-0006 contains Calculation for embedded assumptions was (From peer review:
numerous assumptions such as the 5 located at the reviewed and added to Section 3.2 in Met at CC-I-III end of Attachment B spreadsheet that are not calculation PRA-FIRE-17663-006-LAR. Suggestion) included as assumptions in Section 3.2. If these are not located in the "assumptions" section, they could RAI not needed.
be missed in the consideration of uncertainty analysis. Staff sees that the cited embedded assumptions were added to section 3.4.7.2 Basis for Significance: No direct risk impact and referred to in Section 3.2. of into DC Cook Fire Ignition Frequency Calculation (PRA-FIRE-17663-006-LAR) report.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
CF-A1-1 The appropriate industry-wide conditional All of the circuit failure likelihood probabilities in (From peer review:
failure probabilities for fire-induced circuit failures the CNP fire PRA were reviewed and, if Not Met at CC-I-III have not been selected for the specific circuit appropriate, updated based on data located in Finding) configurations under consideration. NUREG/CR-6850 Appendix K. Additionally, valves with double-break design were re- RAI submitted as RAI 34(f)
Basis for Significance: Potentially significant impact analyzed to develop best-estimate circuit to CNP FPRA risk profile failure likelihood probabilities accounting for This F&O as it is presented in WOG FPRA this plant-specific feature. The updated circuit Peer Review (LTR-RAM-II-10-041) provides failure probabilities are documented in eleven specific suggestions for correcting calculation PRA-FIRE-176663-010-LAR. circuit failure probabilities. Staff asks the license in an RAI to address these eleven suggestions.
In response to RAI 34(f) in a letter dated August 9th 2012, the licensee provides 21-Oct-11 36
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings explicit explanation of how the recommendation was followed. It most case the recommendation was followed as written.
In two cases (#5 and #7) the recommendations were shown not to apply.
In one case (#9) a more conservative value was used and in another case explanation for not following the recommendation was provided. Staff found all explanations to be reasonable.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
CF-A2-1 Observation: Parametric uncertainties of Appropriate error factors were applied to the (From peer review:
applied hot short probabilities have not been hot short probabilities and were incorporated Not Met at CC-I-III incorporated into the model. into the PRA model. The circuit failure Finding) probability error factors are documented in Basis for Significance: Technical adequacy of the calculation PRA-FIRE-176663-010-LAR. RAI not needed (but related to RAI asked PRA on uncertainty).
Staff found that the DC Cook Fire PRA Uncertainty and Sensitivity Analysis (PRA-FIRE-17763-0015-LAR) provides discussion of the quantitative treatment of circuit failure uncertainty and that in fact parametric data uncertainty for circuit failure was propagated using error factors (see page 7, 9, 10, and
- 22. Based on F&Os from other PRA elements related to uncertainty we ask a general RAI on propagation of parametric data uncertainty because for some elements of the PRA this was not performed quantitatively.
21-Oct-11 37
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings Given the additional information and the fact that the more important underlying issue (i.e.,
completing the parametric propagation of uncertainty) is addressed in RAI 31, the NRC staff finds the disposition to this F&O to be acceptable.
HRA-A1-1 The assessed capability category for this A confirmation of the pathways has been (From peer review:
item is "Met". The methodology that is described performed and is documented in PRA- FIRE- Met at CC-I-III indicates that all credited HFEs are addressed for 17663-012-LAR. Suggestion) fire-related effects. The treatment includes consideration of cognitive and execution impacts. RAI not needed.
The treatment also includes consideration of the location of credited x-MCR actions and the location Staff notes that in DC Cook Fire PRA Human of the postulated fire events. A potential issue arises Reliability Analyses (FIRE-17663-012-LAR) in that it is unclear whether or how the pathway for that operator interviews and dependency that action was addresses and resolved to have not analysis is specifically addressed (See staff been adversely affected. evaluation of F&O FQ-C1-1).
Basis for Significance: The occurrence of a large fire Given the additional information the NRC event could have consequential impacts related to staff finds this deficiency has been fire brigade actions, smoke removal efforts, or other appropriately resolved by the licensee.
considerations could impact operator access to the location for the action.
HRA-A2-1 This SR was assessed as Met. The SR Additional documentation has been provided to (From peer review:
involves the treatment of fire- specific safe shutdown more clearly describe and justify the stated Met at CC-I-III actions in the Fire PRA. The treatment as described treatment of the MCR Abandonment Suggestion) in FIREPRA-17663-0012 selectively applies the procedures. This has been added to actions associated with 01/02-OHP-4025-001. calculation PRA- FIRE-17663-012-LAR. RAI submitted as RAI 29 However, this procedure is specific to Main Control Room Abandonment. The documentation includes a Staff notes that Section 3.5.4 of DC Cook note in the operator interview discussion in Appendix Fire PRA Human Reliability Analyses (FIRE-B indicating that 'operators can refer to procedure for 17663-012-LAR) specifically describes use of additional guidance'. However, there is no other 0.1 for MCR abandonment and provides reference, basis or justification provided. For criteria for its use. Staff asks the license in example, it is unclear whether the 'credit' provided by an RAI to explain why this is an appropriate 21-Oct-11 38
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings the treatment is consistent with operator training, value.
whether the operator are trained in this specific usage of the procedure, or whether that usage is In response to RAI 29.01, the quantification consistent with procedure itself. A concern was noted of main control room scenarios was in that a review of 02-OHP-4025-001 found that the expanded to include modeling of human usage and credit of this procedure is inconsistent error probabilities to respond to scenario-with the state purpose, entry conditions, and caution specific equipment damage. The HEPs for provided before Step 1 of the procedure. all ex-control room actions were re-evaluated using the most recent feasibility analysis Basis for Significance: The analysis documentation performed as an input. The operator actions and treatment are internally consistent in the credit were evaluated using the detailed human assigned to the referenced procedure. Separate reliability analysis quantification, per Section discussions and procedure reviews found that the 5.3 of NUREG-1921. The results of the re-treatment was consistent with the structure of the evaluation showed an increase in delta risk plant procedures but much of this discussion and greater than the acceptance guidelines of evidence is not referenced or discussed in the RG 1.205. The licensee will include the documentation. Because the treatment was valid, modification to the reactor coolant pump this SR was judged to have been met, but that seals as a committed modification in Table additional documentation should be provided to more S-2 of the LAR to reduce the delta risk to clearly describe and justify the stated treatment. within the RG 1.205 guidelines. Based on References to training material, guidelines, or other the licensees response to RAI 29.01 the materials should be used and referenced as staff and the crediting of the reactor coolant applicable. As it currently exists, a notable amount of pump seal modification, the NRC staff finds discussion was necessary to examine this attribute. the disposition of this F&O to be acceptable.
For example, OHI-4023, 4.6.9.f provides clarification of the phrase 'refer to'. 1-OHP-4023-ECA-0.0, step 12 provides a clear 'refer to' to 1- OHP-4025-LS-3 which provides evidence that CNP does in fact treat elements of OHP-4025 as individual recovery actions.
21-Oct-11 39
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings HRA-A3-1 This SR was assessed as Met and it The documentation has been enhanced to add (From peer review:
involves the potential for fire-induced failures references to, and discussion of, OHI-4000, Met at CC-II associated with instruments and alarms that could Section 3. This procedure provides a concise Suggestion) mislead operators such that they would perform an and objective statement as to the expected undesired action. The documents that were reviewed response of the plant operators to alarms. This RAI not needed.
concluded that no undesired actions would occur. has been added to calculation file PRA-FIRE-That conclusion is based in part on a statement that 17663-012- LAR. Staff notes discussion in DC Cook Fire PRA verification of the status is required before or after Human Reliability Analyses (FIRE-17663-the action. A number of instances were identified 012-LAR) related to annunciators in Section wherein the action involves the tripping of a 3.5.1, and related to staffing n Attachment A.
potentially critical pump (RHR, CCW, ESW, etc.).
The information provided calls for the operator to trip Given the additional information the NRC the pump. No further discussion is provided to justify staff finds this deficiency has been or credit a restart of the pump. As presented, it would appropriately resolved by the licensee.
appear that these tripping threats should have been included in the Fire PRA. Further discussions and reviews found that plant procedure OHI-4000, Section 3 includes explicit Expectations that the confirmation of the alarm condition is to occur before execution of the specific alarm response actions. The information provided in this procedure provides a much stronger basis and justification for the applied treatment and should be added to the documentation.
Basis for Significance: The applied treatment and evaluated response of the plant operators to possible fire induced spurious alarms currently relies on interview notes. The plant procedure structure actually includes a much stronger justification and basis for the applied treatment and references to that procedure should be added to the documentation.
HRA-C1-1 This SR was assessed as Met because The cues associated with each human failure (From peer review:
only a single issue was noted. The documentation event included in the Fire PRA model was Met at CC-II provided in FIRE-PRA-17663-0012 included a reviewed and confirmed, especially for those Finding) 21-Oct-11 40
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings number of instances where the treatment was human failure events where the cognitive divided into two separate elements -one to contribution was modeled in a separate basic RAI not needed.
specifically address the cognitive element and event. The cues modeled in the fire PRA have another to address the execution. An example was been documented in calculation file PRA- Staff notes that the cited example (i.e., 1D-1D- OPENHOORHE. This action involves only the FIRE-17663-012-LAR. OPENHOORHE) occurs in only one fire execution of 'opening the door' for the motor driven area. During PRA audit the licensee AFW pump room. The cognitive element was explained that they assumed that the addressed via ESW-20MINCOGHE. The indicated recognition in a fire event (fore for the cited cues for this cognitive element involved only the HFE event) was considered to twice as status of the ESW pumps (trip, flow, pressure). A unlikely as in an internal events event.
review of the implementation of this action found that 1D--- OPENDOORHE is credited for recovery for all Based on this explanation, the NRC staff failure modes of the cooler itself-not just loss of the finds the disposition to this F&O to be cooling water dependency. In this instance, the acceptable.
scope of cues is inconsistent with credited recovery.
Basis for Significance: The treatment of 1D---
OPENDOORHE is such that credit was provided in the Fire PRA even for cases where no valid cue is provided to the operator. The cues are based solely on the availability of ESW to the cooler itself. A random or fire induced failure of the cooler itself would not be detected and hence the credited recovery would not be valid.
FQ-A3-1 The quantification does not account for all The fire PRA model has been modified to (From peer review:
scenario-specific quantification factors. properly account for scenario-specific factors. Met at CC-I-III This includes the following changes: 1) Impacts Finding)
Basis for Significance: Potential impact to FPRA risk to HEPs based on equipment unavailability due profile. to fire. For example, for fire zone 144, when RAI not needed.
the steam supply valves for the TD AFW pump spuriously close, but an HFE for the AFW Staff notes that the licensee appears to have cross-tie assumes the TD AFW pump is modified the model per the F&O comment available for four hours. 2) Dual unit trip (e.g., the HEP for Zone 144 is removed).
considerations have been added to account for During the trip we were asked to note Table dependency of mitigating systems needed for 4 which shows Fire Areas/Zones where local 21-Oct-11 41
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings opposite unit (e.g. AFW or charging crosstie if actions are not credited.
both units are tripped).
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
FQ-A4-1 The "state-of-knowledge" correlation All applicable data was correlated. The (From peer review:
between fire-specific event probabilities (e.g., initiating event basic events for "small pump Met at CC-I-III suppression system unavailability, fire ignition fire" have a common match in the WinNUPRA Suggestion) frequencies, hot short conditional probabilities, etc.) prm file and "pre-action sprinkler suppression" has not yet been applied. systems have a common math in the RAI not needed.
WinNUPRA prm file.
Basis for Significance: The "state-of-knowledge" During the audit it was clarified that state-of-correlation has not been fully addressed, but no knowledge correlations (SOKC) was significant impact on parametric uncertainty performed for like components (i.e., with the evaluation is expected. same type code). The F&O pertains to lack of SOKC for suppression system unavailability, fire ignition frequencies, hot short conditional probabilities, etc.
Given that a sensitivity study based on calculated mean values was performed in response to RAI 31 and the explanation here, the NRC staff finds the disposition to this F&O to be acceptable.
21-Oct-11 42
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings FQ-B1-1 Quantification truncation limits were Iterative calculations have been performed to (From peer review:
selected based on an iterative evaluation with a ensure appropriate truncation limits. Met at CC-I-III preliminary fire model. This iterative evaluation is Convergence can considered sufficient when Suggestion) recommended to be repeated for the full scope fire successive reductions in truncation value of PRA. one decade result in decreasing changes in RAI not needed.
CDF or LERF, and the final change is less than Basis for Significance: Current truncation limits 5%. Staff sees that Section 5.7 of the DC Cook appear to be appropriate. No likely impact to risk Fire PRA Integrated Fire Risk Analysis report profile. specifically describes the truncation convergence method used (see FIRE-17663-014-LAR).
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
FQ-B1-2 Observation: WinNUPRA utilizes the rare The documentation of modeling uncertainties (From peer review:
event approximation, which is not recommended includes a note that the FPRA utilizes the rare Met at CC-I-III when basic event probabilities are above 0.1. event approximation, which introduces some Suggestion) conservatism into the results, and that for Basis for Significance: WinNUPRA is an industry- some applications this may be a consideration RAI not needed.
accepted code (particularly for cutsets in which several basic event probabilities are above 0.1). Staff acknowledges that WinNUPRAs use of the rare event approximation is somewhat conservative for cutsets with basic events with probabilities greater than 0.1. However, such approximation is state-of-art and winNUNPRA is an industry accepted code.
Based on this explanation, the NRC staff finds the disposition to the F&O to be acceptable.
FQ-C1-1 The peer review team observed that the A confirmatory analysis has been performed to (From peer review:
final confirmatory step to ensure that all significant ensure all significant HEP combinations with Met at CC-I-III HEP combinations with potential dependencies have potential dependency have been identified. Finding)
The global CDF and LERF equations (the 21-Oct-11 43
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings not been identified. "global" equations combined together the RAI not needed.
cutsets from all significant FPRA sequences or Basis for Significance: Potentially significant impact all FPRA sequences) have been quantified During the audit the licensee confirmed that on the FPRA risk profile with HEP values set to values that are this final step had been performed and that sufficiently high so that the cutsets are not only a handful of combinations needed truncated. The additional HFE combinations modification and refers to an updated report.
that were identified were then evaluated and The FPRA peer review report (LTR-RAM modified as appropriate to address the degree 10-041) dated July 2010 states on page B-61 of dependency between the HFEs in the cutset The HEP dependency evaluation has been or sequence. performed for the FPRA as documented in Attachment D of the DC Cook Fire PRA Human Reliability Analysis. Identified HEP dependencies have been characterized and are modeled directly in the fault tree (rather than by cutset post-processing) which is judged to be a strength.
Given the additional information, the NRC staff finds the disposition of the F&O to be acceptable.
FQ-D1-1 Documentation of results for significant and A review of significant and non-significant (From peer review:
non-significant sequences (cutset review) has not LERF results was conducted. The results Met at CC-I-III been performed for LERF. Review of importance section of the fire PRA has been updated to Finding) values has not been performed for reasonableness. provide importance values for LERF. This has F&Os generated for other FQ SRs should be applied been provided in calculation PRA-FIRE-17663- RAI not needed.
to the LERF model, as well as the CDF model. 011-LAR.
The staff reviewed DC Cook Fire PRA Basis for Significance: Potential impact to Integrated Fire Risk Analysis report (see quantitative results FIRE-17663-014-LAR) specifically provides LERF importance values in Tables 5-7, 5-9, 5-11, and 5-13. These results were found to be reasonable.
Given the additional information the NRC staff finds this deficiency has been 21-Oct-11 44
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings appropriately resolved by the licensee.
FQ-E1-1 It is not apparent that any of the items listed The results section of the fire PRA has been (From peer review:
in QU-D and LE-F, as clarified in the SR, were updated to provide the data in the supporting Met at CC-I-III considered for the fire quantification -for example, requirements from the internal events portion Finding review of significant and non significant cutsets, of the combined PRA standard (Chapter 2) identification of key contributors to CDF and LERF, associated with high level requirements QU-D RAI not needed.
and review of importance of components and basis and LE-F for LERF. This has been provided in events. calculation PRA-FIRE-17663-011-LAR. It was pointed out during the audit and staff sees that DC Cook Fire PRA Integrated Fire Basis for Significance: This SR requires that CDF Risk Analysis report (see FIRE-17663-014-and LERF internal events' quantification SRs be LAR) specifically provides LERF top addressed for fire. This portion of the work was not contributors in Tables 5-17 and 5-19, and completed at the time of the peer review. importance values in Tables 5-7, 5-9, 5-11, and 5-13. These results are reviewed for reasonableness.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
FQ-F1-1 The documentation of the fire quantification Tables typically included for internal events (From peer review:
provides the CDF and LERF results, but not to the quantification have been added to the report. Met at CC-I-III extent that internal events quantification would be The tables have been added to calculation Finding) done, e.g., tables of most significant fires, ignition PRA-FIRE-17663-011-LAR.
sources, cutset reviews, etc. RAI not needed.
Basis for Significance: The typical types of It was pointed out during the audit and staff quantification tables identified above are needed to sees that DC Cook Fire PRA Integrated Fire facilitate reviews and applications. Risk Analysis report (see FIRE-17663-014-LAR) specifically provides normal results tables in Tables 5-1 through 5-19.
Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
21-Oct-11 45
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings SF-A3-1 Discussions with utility indicate that there Report PRA-FIRE-17663-013-LAR has been (From peer review:
are existing strategies to cope with a complete loss updated to include information on coping Met at CC-I-III of onsite fire suppression systems, e.g., city water strategies. Finding) and pumper truck capability.
RAI not needed.
Basis for Significance: This SR has been met; however, the additional existing strategies discussed Staff notes a paragraph on first responders with the utility to cope with a complete loss of onsite on page 11 of DC Cook Fire PRA Seismic-fire suppression systems needs to be included in the Fire Interactions (PAR-FIRE-17663-00) that documentation. Note that since SF is allowed to be was not previously included.
handled qualitatively, an issue here would have no impact on any quantitative result. Given the additional information the NRC staff finds this deficiency has been appropriately resolved by the licensee.
SF-A4-1 Scientech report PRA- FIRE-17663-0013 Report PRA-FIRE-17663-013-LAR has been (From peer review:
does not reference a "seismic response procedure" updated to include the additional information Met at CC-I-III that was used to fulfill this SR. The plant's seismic on the plants seismic response procedure. Suggestion) response procedure was requested and provided by the utility (1- OHP-4022-001-007, Rev. 10, RAI not needed.
"Earthquake"). This procedure was reviewed in accordance with this SR. The procedure did not Staff sees where DC Cook Fire PRA mention the possibility of a seismically-induced fire or Seismic-Fire Interactions report (PAR-FIRE-spurious operation of fire suppression systems that 17663-00) had been updated to include could compromise postearthquake plant response; general discussion on ARPs, ONPs, EOPs, however, additional discussions with utility indicate and SAMGs that are germane to coping with that there are other existing procedures for coping large-scale events, such as seismically-with large-scale events, such as seismically-induced induced fires.
fires, e.g., emergency plan, fire pre-plans for beyond design basis events. The later of these provides Given the additional information the NRC actions to cope with a complete loss of onsite fire staff finds this deficiency has been suppression. appropriately resolved by the licensee.
Basis for Significance: This SR has been met; however, the additional existing procedures discussed with the utility to cope with large-scale 21-Oct-11 46
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings events needs to be included in the documentation.
Note that since SF is allowed to be handled qualitatively, an issue here would have no impact on any quantitative result.
SF-A5-1 Scientech report PRA- FIRE-17663-0013 Report PRA-FIRE-17663-013-LAR has been (From peer review:
does not reference "fire brigade training procedures" updated to provide the additional information. Met at CC-I-III that were used to fulfill this SR. The plant's fire Suggestion) brigade training procedures were requested and the FP training program description was provided by the RAI not needed.
utility (TPD-600-FP). This document was reviewed in accordance with this SR. There is no training Staff sees that training and fire brigade discussed in the procedures regarding the training is generally described however, ability/inability to fight a fire after an earthquake notes that TPD-600-FP is not discussed in (either in terms of responding to fire alarms and fires, the DC Cook Fire PRA Seismic-Fire storage and placement of equipment, and access Interactions report (PAR-FIRE-17663-00).
routes); however, additional discussions with the utility indicate that there is extensive training on large Given the additional information the NRC scale events such as those included in the fire staff finds this deficiency has been preplans for beyond design basis events-Training appropriately resolved by the licensee.
activities that involve offsite fire response personnel, equipment, and water sources.
Basis for Significance: This SR has been met; however, the additional existing fire-related training discussed with the utility to cope with large-scale events needs to be included in the documentation.
Note that since SF is allowed to be handled qualitatively, an issue here would have no impact on any quantitative result.
SF-B1-1 The documentation of the seismic/fire Report PRA-FIRE-17663-013-LAR has been (From peer review:
interaction analysis relies exclusively on the work updated to validate the assumptions and fix the Not Met at CC-I-III done for the IPEEE. Several unvalidated typographical errors. Finding) assumptions are made in Scientech report 17633-0012 that are intended to justify that the work done RAI submitted as 34(g) 21-Oct-11 47
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings for the IPEEE remains valid today. These unvalidated assumptions are: 1) All fire suppression Staff could not determine that the validation features have been installed in accordance with a of these assumptions had been added to the Standard and all installed equipment is maintained in DC Cook Fire PRA Human Reliability accordance with a Standard, 2) CNP as no cast iron Analyses report (PRA-FIRE-17663-013-fire mains, and 3) No significant changes to the plant LAR). Neither could the licensee point them fire protection features have been made that would out during the trip.
render the IPEEE assessment invalid. These assumptions are made without any validation. In response to RAI 34(g) in a letter dated Therefore, the adequacy of reliance on the IPEEE August 9th 2012, the licensee explicitly seismic/fire (SF) interaction analysis is in question. addressed the three assumptions cited in the The IPEEE assessment of seismic/fire interaction F&O. For the first two assumptions the (circa 1992) was reviewed. It appears that the issue license identifies the engineering documents of having (or not having) cast iron fire mains was that demonstrate compliance to the raised at that time and appears to have never been appropriate standards. In the third the resolved (at least in the documentation provided to licensee lists the fire protection features me). The IPEEE discusses future walkdowns to be credited in the IPEEE and confirms that the performed to address this question, but later Fire Hazards Analysis identifies the same fire walkdowns were silent on this issue. The plant protection features currently credited.
contends that no cast iron fire mains are used, but no Given the additional information the NRC documentation has been provided to verify this. staff finds this deficiency has been Scientech report PRA-FIRE 17663-0013 is appropriately resolved by the licensee.
misnumbered in the body of the report (it is numbered 17663-0012).
Basis for Significance: The validity of the seismic/fire interaction report is dependent on three unvalidated assumptions. Note that since SF is allowed to be handled qualitatively, an issue here would have no impact on any quantitative result.
UNC-A1-1 Calculation 17663-0015, Fire PRA I&M performed parametric uncertainty analysis (From peer review:
Uncertainty and Sensitivity Analyses, does a good of the CDF and LERF results for the risk- Not Met at CC-I-III job of characterizing the potential sources of significant fire zones/areas, and documented Finding) uncertainty in the Fire PRA model. However, this update in calculation file PRA-FIRE-17663-propagation of parametric uncertainty for the fire RAI Submitted as RAI 31 21-Oct-11 48
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings CDF and LERF to address component failure 015-LAR.
probabilities, fire ignition frequencies, detector Staff found that the DC Cook Fire PRA response, and auto suppression availability has not Uncertainty and Sensitivity Analysis (PRA-been performed. The Standard expects that the FIRE-17663-015) provides a detailed parametric uncertainty will be propagated through the description of which elements of the Fire baseline PRA model independent of any planned PRA that parametric uncertainty was risk- informed applications. propagated and accompanying rationale and why in some cases only a qualitative Basis for Significance: This is a required element for treatment was performed. However, we note meeting the supporting requirement. that a statistical propagation of parametric uncertainty was not complet3ed and so a number of F&Os related to the performance of uncertainty analysis on different elements of the PRA are open. Staff asks an RAI to provide an estimate of the difference between the mean and the point estimate and the impact this may have on risk acceptance.
In RAI 31, the NRC Staff requested that the licensee perform a statistical propagation of parametric uncertainty and assess the impact on the risk results presented in the LAR. Finding UNC-A1-1 on SR UNC-A1 noted that the licensee had not performed a propagation of parametric uncertainty through the PRA model. In response to the RAI (Reference 10) the licensee provided a sensitivity analysis in which PRA model parameters having distributions were statistically propagated in the CNP Fire PRA model. The sensitivity analysis results show that propagating the parametric uncertainties through the PRA model could potentially significantly impact the results of decisions 21-Oct-11 49
Record of Review D.C. Cook LAR Attachment V - Tables V-1 and V-2 Fire PRA Peer Review - Facts and Observations (F&Os)
\Facts and Observations (F&Os) Licensee Disposition NRC Staff Findings because of the little margin available before the proposed CNP RI/PB FPP potentially exceeds the risk acceptance guidelines for Region II (small change) in RG 1.174. See Section 3.4.7 of this SE for the NRC staffs evaluation of this sensitivity study.
Consequently, the NRC staff finds that the PRA is technically adequate with regard to SR UNC-A1, and associated SR QU-E3, to support the fire risk evaluations and other risk calculations required for the NFPA 805 application, and the licensee has demonstrated the capability to a perform the propagation of parametric uncertainty through the PRA model as needed to support future self-approval.
MU-B3-1 PRA Model Update Procedure 12- EHP- Sections 3.1.1, 3.1.2, and 3.3.1 of the CNP (From peer review:
9010-PRA-001 Section 3.3 describes the process PRA Model Update procedure were revised to Not Met at CC-I-III used for periodic PRA updates and Section 3.4 ensure that updates are performed to Suggestion) describes cases where an interim update may be Capability Category II of the PRA Standard, appropriate. However, there is no explicit direction to: and that the PRA Supervisor will identify RAI not needed.
- 1) Perform updates in a manner that maintains whether a model change is an update or an consistency with the supporting requirements of the upgrade requiring follow-on peer review. During the audit the license presented the ASME/ANS PRA Standard, and 2) Determine if PRA Model Update Procedure 12-EHP-changes to the model incorporated during a periodic 9010-PRA-001 showing that the PRA or interim update meet the definition of a PRA supervisor will determine whether a model upgrade requiring a peer review. change is significant enough to require a follow-on peer review. See item Section Basis for Significance: Discussion with AEP 3.1.1 item (e).
personnel revealed that the actual practice meets the requirement even though the procedure does not Given the additional information the NRC explicitly require it. staff finds this deficiency has been appropriately resolved by the licensee.
21-Oct-11 50