L-PI-16-090, Response to Request for Additional Information on License Amendment Request to Adopt NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactors

Response to Request for Additional Information on License Amendment Request to Adopt NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactors

ML16350A105
Person / Time
Site:	Prairie Island
Issue date:	12/14/2016
From:	Northard S Northern States Power Company, Minnesota, Xcel Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CAC ME9734, CAC ME9735, L-PI-16-090
Download: ML16350A105 (48)

Text

Energy@ Prairie Island Nuclear Generating Plant 1717 Wakonade Drive East Welch, MN 55089 December 14, 2016 L-PI-16-090 10 CFR 50.90 10 CFR 50.48(c)

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Units 1 and 2 Dockets 50-282 and 50-306 Renewed License Nos. DPR-42 and DPR-60 License Amendment Request to Adopt NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactors - Response to Request for Additional Information (CAC Nos. ME9734 and ME9735)

References:

1. NSPM letter, J.P. Sorensen to NRC Document Control Desk, License Amendment Request to Adopt NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactors, L-PI-12-089, dated September 28, 2014, ADAMS Accession No. ML12278A405.

2. NSPM letter, S. Sharp to NRC Document Control Desk, Supplement to .

License Amendment Request to Adopt NFPA 805 Performance Based Standard for Fire Protection for Light Water Reactors, L-PI-14-045, dated April 30, 2014 (ADAMS Nos. ML14125A106 and ML14125A149).

3. NRC email, T. Beltz to S. Chesnutt, Prairie Island Nuclear Generating Plant, Units 1 and 2 - NFPA 805 Requests for Additional Information and Response Timeline (TAG Nos. ME9734 and ME9735), dated March 30, 2015 (ADAMS Accession No. ML15089A157).

4. NSPM letter, K. Davison to NRC Document Control Desk, License Amendment Request to Adopt NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactors - Response to Request for Additional Information, L-PI-15-041, dated May 28, 2015 (ADAMS No. ML15153A018).

5. NSPM letter, K. Davison to NRC Document Control Desk, License Amendment Request to Adopt NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactors - Response to Request for Additional Information- 90-Day Responses, L-PI-15-052, dated June 19, 2015 (ADAMS No. ML15174A139).

Document Control Desk Page 2

6. NSPM letter, K. Davison to NRC Document Control Desk, License Amendment Request to Adopt NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactors - Response to Final Request for Additional Information (PRA- Second Round), L-PI-15-059, dated October 22, 2015 (ADAMS No. ML15296A259).

7. NRC email, T. Beltz to A. Hazel hoff, Prairie Island Nuclear Generating Plant-Requests for Additional Information (AFPB) re: LAR to Adopt NFPA 805 (TAG Nos. ME9734 and ME9735), dated January 8, 2016 (ADAMS No.

ML16008A109).

8. NSPM letter, K. Davison to NRC Document Control Desk, License Amendment Request to Adopt NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactors - Response to Request for Additional Information, L-PI-16-004, dated January 20, 2016 (ADAMS No.

ML16020A375).

9. NSPM letter, K. Davison to NRC Document Control Desk, License Amendment Request to Adopt NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactors- Response to Request for Additional Information, L-PI 005, dated May 24, 2016 (ADAMS No. ML16152A046).

10. NRC email, R. Kuntz to A. Hazel hoff, Prairie Island Nuclear Generating Plant-Requests for Additional Information re: LAR to Adopt NFPA 805 (CAC Nos.

ME9734 and ME9735), dated July 26, 2016 (ADAMS No. ML16208A540).

11. NSPM letter, K. Davison to NRC Document Control Desk, License Amendment Request to Adopt NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactors- Response to Request for Additional Information, L-PI 067, dated August 17, 2016 (ADAMS No. ML16230A554).

12. NRC email, R. Kuntz to G. Eckholt, Request for Information related to Prairie Island NFPA-805 license amendment (CAC Nos. ME9374 and ME9735), dated November 18, 2016 (ADAMS No. ML16326A353).

In Reference 1, the Northern States Power Company, a Minnesota Corporation (NSPM) doing business as Xcel Energy, requested approval from the Nuclear Regulatory Commission (NRC) to transition the fire protection licensing basis for the Prairie Island Nuclear Generating Plant (PINGP) to 10 CFR 50.48(c), National Fire Protection Association Standard 805 (NFPA 805). Supplemental information was provided in letters dated November 8, 2012 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML12314A144) and December 18, 2012 (ADAMS Accession No. ML12354A464).

In Reference 2, NSPM submitted a revised Fire Probabilistic Risk Assessment (PRA) in a supplement to the subject License Amendment Request (LAR). In Reference 3, the

Document Control Desk Page 3 NRC staff provided requests for additional information (RAis) regarding this request and also provided a timeline and due dates for submitting responses within 60, 90, or 120 days after an on-site Audit that was conducted March 23-25, 2015. NSPM letter dated May 28, 2015 (Reference 4) provided responses to the 60-day RAis and one of the 90-day RAis (Fire Protection Engineering RAI 03). NSPM letter dated June 19, 2015 (Reference 5) provided responses to the remaining 90-day RAis.

NSPM letter dated October 22, 2015 (Reference 6) provided responses to second round RAis and included an Attachment L request, "Approval Request 4 -Wiring Above Suspended Ceilings." In Reference 7, the NRC staff provided RAison this Attachment L request. In Reference 8, NSPM provided responses to these RAis. In Reference 9, NSPM provided responses to RAis. In Reference 10, the NRC staff provided additional RAis. In Reference 11, NSPM provided responses to these RAis. In Reference 12, the NRC staff provided an additional RAI. to this letter provides NSPM's response to the RAI received in Reference

12. Enclosure 2 provides an updated Attachment S, Plant Modifications and Items for Implementation.

This letter is submitted in accordance with 10 CFR 50.90. The additional information provided in this letter does not impact the conclusions of the No Significant Hazards Evaluation or Environmental Considerations Evaluation presented in Reference 2.

In accordance with 10 CFR 50.91, NSPM is notifying the State of Minnesota of this additional information by transmitting a copy of this letter to the designated State Official.

If there are any questions or if additional information is needed, please contact Gene Eckholt at 651-267-1742.

Summary of Commitments This letter contains no new commitments and makes no revisions to any existing commitments.

I declare under penalty of perjury that the foregoing is true and correct.

a;;n DeJ[ber 14,2016.

Scott Northard Site Vice President- Prairie Island Nuclear Generating Plant Northern States Power Company- Minnesota

Document Control Desk Page4 Enclosures (2) cc: Administrator, Region Ill, USNRC NRR Project Manager, PINGP, USNRC Resident Inspector, PINGP, USNRC State of Minnesota

L-Pl-16-090 NSPM Response to Request for Additional Information (RAI)

Regarding the license Amendment Request to Adopt National Fire Protection Association (NFPA) Standard 805 at Prairie Island Nuclear Generating Plant Units 1 and 2 NRC Request Probabilistic Risk Assessment (PRA) Request for Additional Information (RAI) 21 Very Early Warning Fire Detection System Credit Section 2.4.3.3 of National Fire Protection Association (NFPA) Standard 805, "Performance-Based Standard for Fire Protection for Light Water Reactor Electric Generating Plants," 2001 Edition, states that the probabilistic safety analysis (PSA)

(PSA is also referred to as probabilistic risk assessment (PRA)) approach, methods, and data shall be acceptable to the authority having jurisdiction, which is the Nuclear Regulatory Commission (NRC). Section 2.4.4. 1 of NFPA 805 further states that the change in public health risk arising from transition from the current fire protection program to an NFPA 805 based program, and all future plant changes to the program, shall be acceptable to the NRC. Regulatory Guide 1. 174, "An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis," Revision 2, (RG 1.174) provides quantitative guidelines on core damage frequency (CDF), large early release frequency (LERF), and identifies acceptable changes to these frequencies that result from proposed changes to the plant's licensing basis and describes a general framework to determine the acceptability of risk-informed changes. The NRC staff's review of the information in the license amendment request identified additional information that is required to fully characterize the risk estimates.

New guidance on the credit taken for very early warning fire detection system (VEWFDS) is available in NUREG-2180, "Determining the Effectiveness, Limitations, and Operator Response for Very Early Warning Fire Detection Systems in Nuclear Facilities, (Delores-VEWFIRE)" of which the pre-publication final version is available at Agencywide Documents Access and Management System (ADAMS) Accession Nos.

ML 16286AOOO and ML16286A002 (note that the accession numbers may change when the final version is published). The methodology in NUREG-2180 is acceptable to the NRC because it is currently the best available guidance. The guidance provided in frequently asked question (FAQ) 08-0046, "Closure of National Fire Protection Association 805 Frequently Asked Question 08-0046 Incipient Fire Detection Systems" (ADAMS Accession No. ML093220426), has been retired and alternative approaches for staff evaluation are necessary to complete the safety evaluation.

Explain how credit (e.g., approach, methods, data, and assumptions) taken in the fire PRA (FPRA) for the proposed VEWFDS is consistent with the guidance in NUREG-2180 or bounds the risk results (i.e., CDF, LERF, change in CDF, and change in LERF)

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L-Pl-16-090 NSPM that would be obtained had the guidance in NUREG-2180 been applied. If credit taken for VEWFOS in the FPRA is not consistent with or bounded by NUREG-2180, provide:

a. The risk results (i.e., COF, LERF, change in CDF, and change in LERF): (1) without credit for VEWFOS, (2) that would be obtained had the guidance in NUREG-2180 been applied, or that would be obtained had an alternative method been used, along with a description and justification for the alternative method. Development and use of an alternative proposal may extend the time required to complete the review. The new risk results can be generated from a sensitivity study type evaluation insofar as formal incorporation of the new method into the PRA model of record is not required.

b. Explain how the total risk and increases in risk are consistent with the guidelines in RG 1.174.

c. If additional method and model modifications to the PRA are used and discussed in response to item a. above, explain how they will be incorporated into the PRA model of record that will be used to determine whether the as-built modifications meet the RG 1. 174 guidelines and to support the self-approval of post-transition changes.

NSPM Response - PRA RAI 21 .a

a. The Prairie Island Nuclear Generating Plant (PINGP) Fire PRA currently credits incipient detection in Fire Area 18 (i.e., the Relay Room) following the guidance in Supplement 1 of NUREG/CR-6850. As requested in PRA RAI 21, a sensitivity analysis has been conducted to evaluate the risk level changes to Unit 1 and Unit 2 based on the Nuclear Regulatory Commission's .(NRC) revised guidance for crediting incipient detection as documented in the pre-publication final version of NUREG-2180. In addition, the sensitivity analysis incorporates 1) the heat release rate probability distributions for electrical cabinets documented in NUREG-2178 (RACHELLE-FIRE), 2) the latest fire ignition frequencies documented NUREG-2169, and 3) revisions to the hot gas layer (HGL) formation time by incorporating thermal response of the target cable trays away from the zone of influence.

The specific scope of the sensitivity analysis includes:

• The sensitivity analysis only affects Fire Area 18 .. The CDF and LERF values reported as part of PRA RAI 03 in all other Fire Areas remain unchanged.

• The incipient detection system is credited only in Fire Area 18 within the PINGP Fire PRA.

• Heat release rate probability distributions have been updated only in Fire Area 18.

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L-PI-16-090 NSPM

• The generic fire ignition frequencies have been apportioned throughout the fire areas within the scope of the Fire PRA but the numerical changes are only reflected in Fire Area 18.

• Credit for cable thermal response in the HGL analysis has been implemented in Fire Area 18 only.

Incipient Detection Credit:

The Fire PRA supporting the RAI response submitted in May 2016 included credit for an incipient detection failure probability in Fire Area 18 based on guidance documented in Supplement 1 to NUREG/CR-6850. This credit was reflected in the fire scenario quantification process by multiplying the fire ignition frequencies of selected electrical cabinets by an incipient detection failure probability of 0.05. It should be noted that this credit was not included in the first damage state of the scenario progression, which consisted of damaging the ignition source only. In the sensitivity analysis described in this response, the incipient detection failure probability is increased to 0.32. This value is generated using the latest guidance for crediting incipient detection systems documented in NUREG-2180.

Updated Heat Release Rate Distributions:

NUREG-2178 documents the results of joint research efforts to 1) classify electrical enclosures in terms of function, size, contents, and ventilation, and 2) the determination of peak heat release rate (HRR) probability distributions considering these specific electrical enclosure characteristics. HRR values associated with the fire modeling analysis in the PINGP Fire Area 18 hc:we been updated to reflect the recommendations in NUREG-2178. The appropriate distributions are assigned to the corresponding electrical cabinets in Fire Area 18 based on the cabinet volume and configuration. For this sensitivity analysis, only the "default" cabinet combustible load configuration was selected and no credit has been incorporated for low or very low combustible content. In addition, the sensitivity analysis includes no credit for the obstructed plume methodology described in NUREG-2178.

Updated Fire Ignition Frequencies:

The latest fire ignition frequencies documented in NUREG-2169 are also incorporated in the sensitivity analysis. The applicable generic frequencies for Fire Area 18 include: Electrical Cabinets (Bin 15.1 ), Cable Fires Due to Welding and Cutting in the Control/Auxiliary/Reactor Building (Bin 5), Junction Box Fires (Bin 18), Transients in the Control/Auxiliary/Reactor Building (Bin 7), and Transients Due to Welding and Cutting in the Control/Auxiliary Reactor Building (Bin 6). These frequencies are apportioned throughout the physical analysis Page 3 of 9

L-PI-16-090 NSPM units within the scope of the PINGP Fire PRA in order to obtain the applicable values for Fire Area 18.

Cable Thermal Response:

The existing Fire PRA analysis for HGL formation assumes that all Fire PRA credited components or cables will fail when the HGL reaches the damage temperature of 205°C. Using this approach, the HGL damages all Fire PRA credited components in 17 minutes, which is the time the gas temperature reaches 205°C with no credit from cable thermal response (i.e., cable heating).

This damaging HGL formation time is based on the worst ignition source-secondary combustible configuration and was applied to all the corresponding scenarios in Fire Area 18. Specifically, the scenario consists of a propagating fire between three electrical cabinets and twelve cable trays. The CFAST analysis suggests that the damage temperature of 205°C is reached in approximately 17 minutes and that the oxygen concentration in the room reaches one percent in approximately 25 minutes.

In order to credit the thermal response from cables, it is necessary to perform a heat transfer analysis for determining the lag time due to the heat transfer process between the gas temperature surrounding the cables and the internal cable temperature. In this approach, damage is assumed to occur when the internal cable temperature reaches 205°C. Crediting the thermal response from cables is achieved by assuming that the time remaining until damage occurs is calculated based on the data in Appendix H of NUREG/CR-6850. Under this approach, a cable begins at an undamaged state with a value of 0 and accumulates degradation until a damaged state with a value of 1 (i.e. 100%) is reached.

Since the postulated fire scenarios in Fire Area 18 consist of generated temperatures that vary as a function of time, cables accumulate damage within the appropriate intensity levels until the necessary heat exposure for damage is received. As a conceptual example, consider a thermoplastic cable that is immersed for 15 minutes at 210 oc and 9 minutes at 240 °C. Using the Table H-6 in Appendix H of NUREG/CR-6850, the cable will have spent a total of 15 + 9 =

24 minutes over the 205 oc threshold and since the damage time listed for 240 oc is 20 minutes, the cable is assumed to be damaged. In the heat transfer method implemented in this sensitivity analysis, the cable would accumulate 50%

of damage in the first 15 minutes. That is, since the damage time listed in Table H-6 of NUREG/CR-6850 for a 210 oc exposure is 30 min, a target exposure of 15 min accumulates "50%" of the heat necessary for damage. Similarly, since the damage time in Table H-6 of NUREG/CR-6850 for 240 oc is 20 min, a target

=

exposure of 9 minutes produces 9/20 0.45, or 45% of the heat necessary for damage. Consequently, the target would remain undamaged as 0.5 + 0.45 =

0.95 indicating that it has not received enough heat to generate cable damage.

Crediting the thermal response, the failure time for thermoplastic targets can be more than 60 minutes in Fire Area 18 in most of the postulated scenarios. This is Page 4 of 9

L-PI-16-090 NSPM due to the relatively large size of the relay room. The following considerations are included in the interpretation of the CFAST results:

1. CFAST predicts that the oxygen concentration in the HGL will reach very low levels (i.e. approximately one percent) affecting the combustion process for the larger postulated fires. This suggests that a vigorous growing fire propagation through numerous cable trays can't be sustained in the room for a relatively long period of time.

2. For the largest postulated fire, which includes three electrical cabinets and twelve cable trays, credit to the thermal response from cables does not suggest damage as the temperatures in the room peak at 25 minutes, when the fire runs out of oxygen. The approach described above for crediting heat soak indicates that the cables have received approximately 85% of the heat necessary for damage. This was the CFAST analysis selected for all the scenarios in the base PINGP Fire PRA as it resulted in a HGL time of 17 minutes (i.e., 17 minutes for the gas temperature to reach 205 °C).

Additional CFAST cases with increased ventilation openings were evaluated to ensure that the effects of oxygen consumption were not reducing the peak HGL temperatures. This ensured the HGL temperature was not reduced by oxygen depletion in the room and generated conservatively high exposure temperatures for the cable thermal response calculation. This is necessary as CFAST predictions indicate that the specified fire can't be sustained given the oxygen levels, suggesting that the internal cable temperature may not reach the damage temperature threshold.

Since the HGL temperature can be affected by the ventilation conditions, additional ventilation configurations were evaluated to analyze the effect on HGL temperature. The following additional scenarios were evaluated using the same compartment dimensions and configurations,. and the same fuel composition and boundary material properties stated in the base Fire PRA model:

• Scenario 1: Two open doors (current size): The same doors modeled in the original fire scenario, but opened from the beginning of the simulation.

The doors height and width are 2.12 m and 1.82 m respectively. The fire is located in the same position at 1.96 m.

• Scenario 2: Two open doors (floor to ceiling): The doors are modeled with the same area simulated in Scenario 1, but with the height equal to the room height (6.056 m) and the same fire location.*

• Scenario 3- One open door (floor to ceiling): Similar to Scenario 2 but with only one open door (the other door is closed).

• Scenario 4 - One fourth of the door area is opened (floor to ceiling):

Similar to Scenario 3 but the door width is 1/4 of the door in Scenario 3.

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L-PI-16-090 NSPM

• Scenario 5 - Two open doors and the fire located at the floor level. Similar to Scenario 1 but the fire is located at the floor level instead of 1.96 m height.

• Scenario 6 - One open door and the fire located at the floor level. Similar to Scenario 3 but the fire is located at the floor level instead of 1.96 m height.

The results indicate that the higher HGL temperatures are obtained for Scenarios 2 and 3 where the fire is not affected by lack of oxygen (oxygen depletion) in the relay room.

Using the integral method described above, the cable damage time was determined for those scenarios (2 and 3) with the higher HGL temperature. The results showed that cables can be damaged at 1,532 seconds (i.e., 25.5 min).

This value was used in this sensitivity analysis as the HGL time for all scenarios in relay room. This is conservative as a number of scenarios have fewer cable trays involved and it ignores the effects of oxygen depletion in the room. This approach was used previously in the Brunswick Steam Electric Plant NFPA 805 LAR, dated September 25, 2012, with numerous Supplements, and was discussed in the Brunswick Steam Electric Plant NFPA 805 Safety Evaluation dated January 28, 2015 (ADAMS Accession No. ML14310A808), on page 80.

The risk results from the sensitivity study are presented in the response to PRA RAI 21.b, below.

NSPM Response ~ PRA RAI 21.b

b. New scenario frequencies for Fire Area 18 were calculated implementing the updates described above. The fire risk for Fire Area 18 was then evaluated using these revised frequencies as well as the conditional core damage and conditional large early release probabilities already available for these scenarios in the Fire PRA. This is possible because the assigned target sets for each scenario were not changed or updated as part of the sensitivity analysis. Table 1, Table 2, Table 3 and Table 4 summarize the resulting fire risk values.

Table 1: Fire Area 18 Core Damage Frequency Incorporating RACHELLE-FIRE, NUREG-2169, Thermal Response Hot Gas Layer Time, and NUREG-2180 CDF after incorporating RACHELLE-FIRE, NUREG-Unit 2169, Thermal Response, and NUREG-2180 CDF in PRA RAI 03 1.6E-05 1.5E-05 Page 6 of 9

L-PI-16-090 NSPM Table 2: Fire Area 18 Large Early Release Frequency Incorporating RACHELLE-FIRE, NUREG-2169, Thermal Response Hot Gas Layer Time, and NUREG-2180 LERF after incorporating RACHELLE-FIRE, NUREG-Unit 2169, Thermal Response, and NUREG-2180 LERF in PRA RAJ 03

"""~"~'~'~~"~~~~"'~~"'~*~~~~,~.~~**~*****~~~~*~***~~ .... ~~~~**"'

Unit 1 3.2E-07 1.7E-07

~

Unit 2 3.0E-07 1.5E-07 Table 3: Total Core Damage Frequency CDF after incorporating RACHELLE-FIRE, NUREG-Unit 2169, Thermal Response, and NUREG-2180 in CDF in PRA RAJ 03 Fire Area 18 only Unit 1 6.4E-05 5.7E-05 Unit 2 6.5E-05 5.8E-05 Table 4: Total Large Early Release Frequency LERF after incorporating RACHELLE-FIRE, NUREG-Unit 2169, Thermal Response, and NUREG-2180 in Fire LERF in PRA RAJ 03 Area 18 only 8.4E-07

.....................~.

8.2E-07 Table 5 and Table 6 summarize the changes in the delta CDF and delta LERF in Fire Area 18.

Table 5: Fire Area 18 Delta Core Damage Frequency Fire Area 18 LlCDF after Incorporating RACHELLE-Fire Area 18 LlCDF in Unit FIRE, NUREG-2169, Thermal Response, and PRA RAJ 03 NUREG-2180 Unit 1 1.4E-06 1.8E-06 Unit 2 1.2E-06 1.5E-06 Table 6: Fire Area 18 Delta Large Early Release Frequency Fire Area 18 LlLERF after Incorporating RACHELLE-Fire Area 18 LlLERF in Unit FIRE, NUREG-2169, Thermal Response, and PRA RAJ 03 NUREG-2180 4.6E-08 3.3E-08 Table 7 and Table 8 summarize the changes in the total delta CDF and total delta LERF for Unit 1 and Unit 2.

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L-Pl-16-090 NSPM Table 7: Total Delta Core Damage Frequency Total .ilCDF after Incorporating RACHELLE-FIRE, Total .ilCDF in PRA Unit NUREG-2169, Thermal Response, and NUREG-2180 RAI03 in Fire Area 18 only Unit 1 9.3E-06 9.6E-06

'"~" ,,-,, -" __,,___ ,,,,,

'--~-""--"""''

Unit 2 5.7E-06 6.0E-06 Table 8: Total Delta Large Early Release Frequency Total .ilLERF after Incorporating RACHELLE-FIRE, Total .ilLERF in PRA Unit NUREG-2169, Thermal Response, and NUREG-2180 RAI03 in Fire Area 18 only Unit 1 1.8E-07 1.7E-07 Unit 2 1.1E-07 9.6E-08 After incorporating the revised incipient detection failure probability from NUREG-2180, as well as the revised electrical enclosure heat release rates from NUREG-2178, the revised ignition frequencies from NUREG-2169, and the revised time to HGL formation accounting for thermal lag, the total fire risk contribution for Fire Area 18 is lower than that reported in the response to PRA RAI 03 and therefore is within the limits described in Regulatory Guide 1.174. The total CDF, total LERF, total delta CDF and total delta LERF for all Fire Areas remain below the Regulatory Guide 1.174 limits.

The risk reduction reflected in the sensitivity analysis suggests that the updates summarized in this response are necessary to mitigate the impact of the increase in failure probability of the incipient fire detection system as calculated following the guidance in NUREG 2180. In particular, the use of the heat release rate probability distributions from NUREG 2178 and the credit for the thermal response in cables associated with the relay room HGL scenario provided the largest risk reduction. The sensitivity analysis includes the following conservatism:

• The time to HGL formation is the same for all ignition sources, regardless of the heat release rate probability distribution for that source. This approach uses the conservative HGL formation time (i.e.,

the shortest time to formation) and then applies this value to all ignition sources in Fire Area 18. Ignition-source specific calculations of HGL timing would likely yield longer times for ignition sources that are assigned lower peak heat release rate probability distributions.

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L-PI-16-090 NSPM NSPM Response - PRA RAI 21.c

c. The PRA model of record that will be used to determine whether the as-built modifications meet the RG 1.174 guidelines and to support the self-approval of post-transition changes will be revised per a new AttachmentS, Table S-3 item.

Item 70 will be added, as follows:

New Implementation Item- Table S-3, Item 70:

NSPM will update the PINGP Fire PRA model using an NRC approved method for VEWFDS PRA credit. If the update results in a risk increase greater than RG 1.174, NSPM will take action to reduce the risk results. Applicable compensatory measures will remain in place until the calculated risk increase is within RG 1.174 limits.

Item 70 implementation timing will be reflected in the introduction section of Table S-3 as follows:

"Note that Item 20, Item 66 and Item 70 are associated with modifications described in Table S-2 and will be completed 180 days after modifications are complete."

In addition, AttachmentS, Table S-1 and Table S-2 were updated to reflect the completion of modification Item 40.

Enclosure 2 provides an updated AttachmentS, Plant Modifications and Items for Implementation. This update supersedes the Attachment S provided in the RAI response dated May 24, 2016.

The NFPA 805 transition license condition is revised to include item 70, as shown below.

Transition License Condition

3. The licensee shall implement the items listed in AttachmentS, Table S-3, "Implementation Items," of Northern States Power- Minnesota letter L-PI-16-090, dated December 14, 2016, within twelve months after NRC approval, with the exception of Implementation Items 20, 66 and 70 which are associated with modifications and will be completed 180 days after modifications are complete.

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L-PI-16-090 NSPM Enclosure 2 Attachment S - Plant Modifications and Implementation Items, Revision 3 34 Pages Foil ow

Northern States Power~ Minnesota Items S. Modificati ons and Implemen tation Items 33 Pages Attached Attachme ntS, Revision 3, supersede s Attachme ntS, Revision 2, provided in the RAI response dated May 24, 2016 PINGP Page S~1 ~ Revision 3

Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Tables S-1, Plant Modifications Completed, and S-2, Plant Modifications Committed, provided below, include a description of the modifications along with the following information:

" A problem statement,

• Risk ranking of the modification,

• An indication if the modification is currently included in the FPRA,

• Compensatory Measure in place if non-compliant with the Current Licensing Basis, and

• A risk-informed characterization of the modification and compensatory measure.

" The following legend should be used when reviewing the Risk Rank in Tables S-1 and S-2:

o High = Modification would have an appreciable impact on reducing overall fire CDF.

o Medium =Modification would have a measurable impact on reducing overall fire CDF.

o low= Modification would have either an insignificant or no impact on reducing overall fire CDF.

o N/A =Not modeled in the FPRA, therefore a risk ranking is not provided.

NSPM is requesting two full refueling cycles beyond SE issuance to fully implement modifications. This is, in part, due to the outage strategies implemented at PINGP where only one train is removed from service per outage, per unit. Due to the significant modifications required to transition PINGP to NFPA 805, additional time is necessary to fully implement modifications described in Table S-2.

The Proposed Modification statements in Table S-2 provide a conceptual design to address the Problem Statement. The final design and installation to resolve the Problem Statement will be developed and approved in accordance with Xcel Engineering processes, hence implementation details may vary.

PINGP Page S Revision 3

Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-1 Plant Modifications Completed In Comp Risk Informed Item Rank Unit Problem Statement Modification FPRA Measure Characterizati on 9 Low 1,2 Fire Suppression required for Modified fire suppression No N/A The proposed the Fire PRA was not code systems in the following fire modification reduced risk compliant, as required by areas to resolve NFPA by allowing the Fire PRA NFPA 805, for the following Suppression code deviations to credit fire suppression Fire Areas: FA 18,418, 31, & as follows: systems in the listed Fire

32. Areas. Per the 2009 FA 18: Installed an odorizer for ASME PRA Standard, fire the Cardox System. suppression systems must be code compliant if FA 31: Resolved non- they are credited in the compliances with pendant Fire PRA.

sprinkler heads.

FA 32: Resolved non-compliances with pendant sprinkler heads.

FA 41 8: Installed missing Sprinkler #229.

FA418: Installed Heat Activated Detector (HAD) in the enclosure for the 121 Motor Driven Fire Pump.

FA418: Installed a sprinkler head above the Diesel Driven Fire Pump because of a large obstruction.

(Ref: EC 21578)

From Table S-2, item 9 Page S Revision 3 PINGP

Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-1 Plant Modifications Completed In Comp Risk Informed Item Rank Unit Problem Statement Modification FPRA Measure Characterizati on 12 Medium 1,2 A fire in Fire Area 29 could Installed a rated fire barrier Yes N/A This modification reduced damage cables required for between Fire Area 29 and Fire fire risk by providing a operation of Train A Cooling Area 69. rated fire barrier between Water Pumps which supply risk significant cables and cooling water to D1 (Ref: EC 21574) fire initiators.

Emergency Diesel Generator which powers Train A From Table S-2, Item 12 safeguards Bus 15.

A fire in Fire Area 69 could damage cables that supply power to ventilation fans for D2 Emergency Diesel Generator supply to Train B safeguards Bus 16. A fire in Fire Area 69 could also damage cables required for offsite power to Bus 15 and Bus 16.

Fire Area 29 and 69 were

• defined as separate areas in the 1977 Fire Hazards Analysis that was submitted to the NRC and accepted.

There is an open pathway between Fire Area 29 and 69; therefore the Fire PRA Plant Partitioning combined Fire Area 29 and 69 (along with 8, 14, 27, and 70) into Fire Compartment 8GRP. Risk for Fire Compartment 8GRP

• was high when all of these areas were combined.

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Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-1 Plant Modifications Completed In Comp Risk Informed Item Rank Unit Problem Statement Modification FPRA Measure Characterizati on 13 Medium 1 A fire in the control room or Wired additional relay contacts Yes N/A This modification reduced relay room could have from the low speed relay in risk by eliminating the caused hot shorts on cables series with indicating light in possibility that a hot short that could spuriously start D1 the control room so that once on a cable in the Control and close the cooling water D1 speed was greater than and Relay Room could supply valve. This condition 250 RPM, the potential hot isolate cooling water to resulted in unrecoverable short on the indicating light in D1 Emergency Diesel damage to the credited the control room is cleared. Generator Emergency Diesel Generator during a fire induced control (Ref: EC 18746) room evacuation.

From Table S-2, Item 13 16 N/A 1,2 The supply ventilation duct Installed a fire damper in the No N/A Not modeled in the between Fire Areas 32 and supply ventilation duct FPRA, therefore a risk 37 did not have a fire damper between FA 32 and 37. ranking was not provided.

and was not code compliant for the Fire PRA, as required (Ref: EC 21572) by NFPA 805.

From Table S-2, item 16 40 N/A 1, 2 There is a fire protection hose Added a restraint for fire No N/A This modification did not station with insufficient pipe protection hose station WF-9 have an impact on the hangers that did not meet the where the pipe comes through Fire PRA because the requirements of NFPA 14, the floor of the Turbine hose station was still Standpipes and Hose Building. functional.

. Systems.

(Ref: EC 18011)

From Table S-2, Item 40 Page S Revision 3

Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification FPRA Measure Characterizati on 1 High 1 A fire could damage Train Modify equipment in FA 31 to Yes Yes The modifications proposed B 12 Motor Driven Auxiliary ensure that Train "A" by Items 1-4 will reduce Feedwater Pump equipment is available for fire risk by modifying FAs 31 (MDAFWP) and the control safe shutdown. and 32 to ensure that each switches for the 11 Turbine The controls and associated FA has either A-train or B-Driven Auxiliary Feedwater cables for the Unit 1 Train "A" train related equipment Pump (TDAFWP) AFWP discharge valves will be unaffected by a fire. This discharge valves (MV- moved to Fire Area 32 so they will limit the number of fire 32238 & MV-32239). Fire are not damaged by a fire in scenarios that could damage to CS-51 003 could Fire Area 31 . damage both trains of cause spurious closure of equipment.

MV-32238 which would isolate the 11 TDAFWP Compensatory measures in flow to the credited 11 accordance with the Steam Generator. Fire Current Fire Protection damage to control switch Licensing Basis are being CS-51 005 could prevent maintained.

closing MV-32239 which could divert the 11 Compensatory measures TDAFWP flow to the non- will continue to remain in credited 12 Steam effect after the NFPA 805 Generator. The NFPA 805 fire protection program Nuclear Safety becomes effective until this Performance Goal Criteria modification is complete.

is not met for Decay Heat Removal.

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Northern States Power- Minnesota AttachmentS- Modifications and Implementation Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification FPRA Measure Characterization 2 High 2 A fire in FA 31 could Modify equipment in FA 31 to Yes Yes The modifications proposed damage the 22 TDAFWP ensure that Train "A" by Items 1-4 will reduce (Train B) and damage the equipment is available for fire risk by modifying FAs 31 circuits for the Train A 21 safe shutdown. and 32 to ensure that each MDAFWP (MV-32383 & The controls, MCC power FA has either A-train or S-MV-32384). Fire damage supply, and associated cables train related equipment at the Train A Hot for the Unit 2 Train "A" AFWP unaffected by a fire. This Shutdown Panel or MCC discharge and suction valves will limit the number of fire 2A1 could affect MV-32383 will be moved out of Fire Area scenarios that could (21 MDAFWP to 21 SG) or 31 so they are not damaged by damage both trains of MV-32384 (21 MDAFWP to a fire in Fire Area 31. The equipment.

22 SG). A fire at MCC 2A1 cables going to Unit 2 Train "A" could affect MV-32026 (21 AFW discharge valves (MV- Compensatory measures in MDAFWP suction from 32383 and MV-32384) will be accordance with the Cooling Water), MV-32336 modified so that MOV will not Current Fire Protection (21 MDAFWP suction from spuriously close due to a fire in Licensing Basis are being CST), MV-32383 (21 Fire Area 31. maintained.

MDAFWP to 21 SG) and MV-32384 (21 MDAFWP to Compensatory measures 22 SG). The NFPA 805 will continue to remain in Nuclear Safety effect after the NFPA 805 Performance Goal Criteria fire protection program is not met for Decay Heat becomes effective until this Removal. modification is complete.

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Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification FPRA Measure Characterizati on 3 High 1 A fire could damage the 11 Modify equipment in FA 32 to Yes Yes The modifications proposed TDAFWP (Train A) and the ensure that Train "B" by Items 1-4 will reduce control switches for the 12 equipment is available for fire risk by modifying FAs 31 MDAFWP discharge valves safe shutdown. and 32 to ensure that each (MV-32381 & MV-32382). The controls, MCC power FA has either A-train or S-Fire damage at the Train B supply, and associated cables train related equipment Hot Shutdown Panel or for the Unit 1 "B" AFWP unaffected by a fire. This MCC 1A2 could affect MV- discharge and suction valves will limit the number of fire 32381 (12 MDAFWP to 11 will be moved out of Fire Area scenarios that could SG) or MV-32382 (12 32 so they are not damaged by damage both trains of MDAFWP to12 SG). A fire a fire in Fire Area 32. The equipment.

at MCC 1A2 could affect cables going to Unit 1 Train "B" MV-32027 (12 MDAFWP AFW discharge valves (MV- Compensatory measures in suction from Cooling 32381 and MV-32382) will be accordance with the Water), MV-32335 (12 modified so that the MOV will Current Fire Protection MDAFWP suction from not spuriously close due to a Licensing Basis are being CST), MV-32381 (12 fire in Fire Area 32. maintained.

MDAFWP to 11 SG) and MV-32382 (12 MDAFWP to Compensatory measures 12 SG). The NFPA 805 will continue to remain in Nuclear Safety effect after the NFPA 805 Performance Goal Criteria fire protection program is not met for Decay Heat becomes effective until this Removal. modification is complete.

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Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification FPRA Measure Characterizati on 4 High 2 A fire could damage the 21 Modify equipment in FA 32 to Yes Yes The modifications proposed MDAFWP (Train A) and the ensure that Train "B" by Items 1-4 will reduce control switches for the 22 equipment is available for fire risk by modifying FAs 31 TDAFWP discharge valves. safe shutdown. and 32 to ensure that each Fire damage to CS-51605 The controls and associated FA has either A-train or S-could cause spurious cables for the Unit 2 Train "B" train related equipment closure of MV-32247 which AFWP discharge valves will be unaffected by a fire. This would isolate the 22 moved to Fire Area 31 so they will limit the number of fire TDAFWP flow to the are not damaged by a fire in scenarios that could credited 22 Steam Fire Area 32. damage both trains of Generator. Fire damage to equipment.

control switch CS-51603 could prevent closing MV- Compensatory measures in 32246 which could divert accordance with the the 22 TDAFWP flow to the Current Fire Protection non-credited 21 Steam Licensing Basis are being Generator. The NFPA 805 maintained.

Nuclear Safety Performance Goal Criteria Compensatory measures is not met for Decay Heat will continue to remain in Removal. effect after the NFPA 805 fire protection program becomes effective until this modification is complete.

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Northern States Power- Minnesota AttachmentS- Modifications and Implementation Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification Measure Characterization FPRA 5 High 1,2 A fire in FA 18, Relay Install Incipient Detection Yes Yes The proposed modification Room could damage both System in the Relay Room that will reduce risk by installing trains of safe shutdown. will continuously sample the an incipient detection Since the risk of Recovery Relay Room air inside the risk system that will notify Actions taken in procedure significant cabinets to identify operators of fires in their F5 App B, Control Room fires based on the detection of incipient state. This Evacuation (Fire) are high, the presence of small amounts reduces the significance of installing a Very Early of products of combustion and, the fire scenarios that could Warning Fire Detection if detected, will sound an alarm lead to control room System (VEWFDS) or in the MCR. abandonment.

Incipient Detection is needed to reduce risk in Compensatory measures in the relay room. accordance with the Current Fire Protection Licensing Basis are being maintained.

Compensatory measures will continue to remain in effect after the NFPA 805 fire protection program becomes effective until this modification is complete.

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Northern States Power- Minnesota AttachmentS- Modifications and Implementation Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification Measure Characterization FPRA 6 Medium 1, 2 Fire damage to cable 1CX- Reroute the following cables Yes Yes The proposed modification 99 in FA 20 could cause a through FA 58 along the "G" will reduce risk because it loss of the normal power line between 8 and 9 and out of will reroute cables feed from 13 Inverter to FA20: associated with the 120VAC Panel 113. Loss of - 1CX-99 (Instrument Bus Ill opposite train of equipment Panel 113 causes CV- (Blue) Panel113 Normal to another FA. This will 31198 (Charging Line to 11 Power Feed) limit the number of fire Regenerative Heat - 1CW-99 (Instrument Bus II scenarios that could Exchanger CV) to fail open (White) Panel 111 Normal damage both trains of causing diversion of flow Power Feed) equipment.

from RCP seal injection to charging. Loss of Panel Install cable Compensatory measures in 113 causes loss of Control - 1DCA-133 (DC Power supply accordance with the Room indication for to BUS 15 Load Sequencer) Current Fire Protection instrument Loops 1N51 from PNL-11 in FA 33 to BUS- Licensing Basis being (Unit 1 Excore Detection 15 Load Sequencer in FA 81 maintained.

Train A), 1T-450A (Unit 1 that is not routed through Fire RCS Loop A Hot Leg Area 20. Compensatory measures Temperature) and 1T-450B will continue to remain in (Unit 1 RCS Loop A Cold effect after the NFPA 805 Leg Temperature). fire protection program becomes effective until this Modification is needed to modification is complete.

protect 1CX-99 from fire damage in Fire Area 20 to maintain Process Monitoring indication in the control room.

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Norlhern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification FPRA Measure Characterizati on 6 Fire damage to cable 1CW-Cent 99 in FA 20 could cause a loss of the normal power feed from 11 Inverter to Panel 111. Loss of Panel 111 results in the loss of Control Room indication for instrument Loop 1L-487 (11 SG Wide Range Level) displayed on Level Recorder 1LR-470.

Modification is needed to protect 1CW-99 (Instrument Bus II (White)

Panel 111 Normal Power Feed).

Fire damage to cable 1CF-35 in FA 20 could cause a loss of Control Room indication for Loop 1L-433 (Unit 1 Pressurizer Level).

Modification to protect cable 1CW-99 from fire damage in FA 20 will ensure Pressurizer Level Indication LOOP 1L-427 remains available in the control room.

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Northern States Power- Minnesota Attachmen tS- Modificatio ns and Implementa tion Items Table S-2 Plant Modificatio ns Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modificatio n FPRA Measure Characteriz ation 6 A fire in FA 20 could Re-route conductors from 1C-Cont damage cable 1C-419 419 (Breaker 15-3, Bus 15 which could affect the Offsite Source from 1 R ability of BKR 15-3, 1RY Transformer) to cable 15403-B source to Bus 15, to clear which is not routed in Fire Area from the potentially faulted 20.

1RY source to Bus 15.

Local manual action is required to open BKR 15-3 so that Bus 15 can be repowered from the 01 Emergency Diesel Generator.

A fire in FA 32 or 58 could Re-route affected conductors damage cable 1C-333 of cable 1C-333 out of FA 32 affecting the 1RY source to and FA 58 so the 1RY offsite Bus 16, and could damage power supply will be available cable 16408-1, CT11 in FA 32 and FA 58.

source to Bus 16, and cables 1DCB-2 and 1DCB-95 which support the 02 source to Bus 16. A modification to route affected conductors of cable 1C-333 out of fire area 32 and 58 is needed to protect the 1RY source to Bus 16 in fire area 32.

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Northern States Power- Minnesota Attachmen tS- Modificatio ns and Implementa tion Items Table S-2 Plant Modificatio ns Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modificatio n FPRA Measure Characteriz ation 6

Cont A fire in FA 058/073, 695' Modify cable elevation of the Aux 2DCA-1 05 (DC Power Cable Building could damage from 21 Battery 125V DC cable 2DCA-105 which Panel 27 Train A) from fire provides DC control power induced failure in Fire Area to PNL 27 which provides 058/073.

DC control power to Bus 25 to trip 4 KV breakers.

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Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification FPRA Measure Characterizati on 8 Low 1, 2 Fire Detection required for Install New Fire Detectors per Yes Yes The proposed the Fire PRA is not code NFPA 72 (Detection) to modification reduces risk compliant, as required by resolve NFPA 72 code by allowing the Fire PRA NFPA 805, for the following deviations in the following to credit fire detection Fire Areas: FA-18, 418, areas: systems in the listed Fire 58/73, 59/74 Areas. Per the 2009 FA 18: Modify the Ionization ASME PRA Standard, fire Fire Detection system to detection systems must provide two zones of coverage be code compliant if they in the Relay Room and P250 are credited in the Fire Computer Room. Modify the PRA.

C02 fire suppression system to actuate if both Ionization Compensatory measures zones detect a fire in lieu of in accordance with the heat detectors. Current Fire Protection Licensing Basis are being FA 41 8: Relocate detector maintained.

from the exhaust stream of a ventilation duct. Compensatory measures will continue to remain in FA 58/73: Resolve various effect after the NFPA 805 detector code issues based on fire protection program S&L Fire Detector Study, Rev becomes effective until 0, PINGP, Project No: 111973- this modification is 055, 12/20/2008 complete.

FA 59/74:Resolve various detector code issues based on S&L Fire Detector Study., Rev 0, PINGP, Project No: 111973-055, 12/20/2008.

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Northern States Power- Minnesota Attachmen tS- Modificatio ns and Implementa tion Items Table S-2 Plant Modificatio ns Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modificatio n FPRA Measure Characteriz ation 10 High 1,2 A fire could damage DC Modify 4160 volt switchgear Yes Yes The FPRA assumes control cables for 4 KV control circuits so that faults on coordination of credited breakers which could the control cables will not buses.

cause the tripping control prevent the over-current trip power fuses to clear which relay from protecting the cable This modification ensures would prevent the breaker from over-current conditions there are no secondary from tripping on over- that could lead to cable fires.

current. The fire could then damage and secondary fires or damage the 4 KV power loss of bus coordination. Compensatory measures in cable, but since the breaker accordance with the can't trip, the cable would Current Fire Protection be subjected to an over- Licensing Basis are being current condition up to the maintained.

full fault current available to the bus. If the cable is not Compensatory measures sized large enough to carry will continue to remain in this amount of current, the effect after the NFPA 805 cable could be damaged fire protection program and start a fire in other fire becomes effective until this areas where it is routed. modification is complete.

Affected Breakers:

BKR 15-1, BKR 15-4, BKR 15-5, BKR 15-9, BKR 16-1, BKR 16-5, BKR 16-6, BKR 16-7, BKR 16-10, BKR 16-12, BKR 25-7, BKR 25-8, BKR 25-9, BKR 25-10,BKR 25-13, BKR 26-5, BKR 26-9, BKR 26-11 11 DELETED DELETED DELETED 12 COMPLETE COMPLETED COMPLETED COMPLETED COMPLETED COMPLETED 13 Page S Revision 3 PINGP

Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification FPRA Measure Characterizati on 14 Medium 1,2 A fire in FA 13/18 could Modify control circuits for the Yes No This modification will damage cables causing Diesel Driven Cooling Water reduce risk by simplifying multiple spurious Pump to eliminate the current restoration of Cooling operations that could required recovery action of Water to provide cooling to damage D1 Emergency sending an operator to the D1 D1 Emergency Diesel Diesel Generator. If fire Room and Screenhouse. Generator and a backup induced cable damage water supply to the Aux caused multiple spurious Feedwater Pumps.

operations that caused D1 (034-011) to spuriously start with no cooling water (11 MDCLP MTR 13-8, 12 DDCLP 145-392, 21 MDCLP MTR 23-4, 22 DDCLP 245-392) then the EDG could be damaged.

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Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification FPRA Measure Characterizati on 15 Medium 1, 2 Fire-induced damage that Install suction pressure Yes Yes The proposed modification could damage cables protection for all the charging will reduce risk by installing causing multiple spurious pumps to ensure adequate Net suction pressure protection operations resulting in Positive Suction Head (NPSH) that will protect the damage to the charging exists to prevent damage to the charging pumps against pumps. If fire induced charging pumps. fires that involve spurious cable damage caused valve closure and other spurious isolation of failures that impact NPSH letdown to the VCT (CV- for the charging pumps.

31226 and CV-31255) and failure to open the RWST Compensatory measures in supply (MV-32060) and accordance with the failure to trip the charging Current Fire Protection pumps, the 11, 12, 13, 21, Licensing Basis are being 22 and 23 positive maintained.

displacement charging pumps (MTR 111J-1) and Compensatory measures MTR 211J-1 could be will continue to remain in damaged due to lack of Net effect after the NFPA 805 Positive Suction Head fire protection program (NPSH). Need to prevent becomes effective until this unrecoverable damage to modification is complete.

credited charging pump due to fire in FA 13/18 to resolve MSO issue.

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Northern States Power- Minnesota Attachmen tS- Modificatio ns and Implementa tion Items Table S-2 Plant Modificatio ns Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modificatio n FPRA Measure Characteriz ation 18 High 1, 2 A fire in Fire Area 1, 13, 18, Install new RCP seals that Yes Yes The proposed modification 59, and 71 could cause a would not be subject to will reduce risk by installing loss of all Reactor Coolant excessive leakage if all seal a shutdown RCP Seal Pump (RCP) seal cooling cooling is lost. package. The new seal will by damaging RCP seal have the ability to preclude injection from charging and larger seal leakage rates Component Cooling (CC) during loss of seal cooling water to the Thermal scenarios.

Barrier Heat Exchanger (TBHX). Compensatory measures in accordance with the Current Fire Protection Licensing Basis are being maintained.

Compensatory measures will continue to remain in effect after the NFPA 805 fire protection program becomes effective until this modification is complete.

19 DELETED DELETED DELETED 20 Low 1,2 The current Fire PRA Install the appropriate fuses Yes No The Fire PRA assumes Model assumes proper and/or breakers to establish proper coordination of coordination exists for all proper selective coordination these power supplies credited power supplies. for panels 136, 137, and 217 Per Fire PRA credited credited to be coordinated power supplies lack selective coordination.

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Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification FPRA Measure Characterizati on 23 Medium 2 A fire in Bus 27 room (Fire Install fuses to provide Yes Yes The Fire PRA assumes Area 127) could damage coordination so that a fire in the proper coordination of DC control power to Bus 25 Bus 27 room will not affect DC these power supplies or Bus 26. control power to Bus 25 or Bus 26.

24 High 1, 2 A fire in the Bus 15 (Fire Provide fuse/breaker Yes No The proposed modification Area 81) or Bus 16 (Fire coordination for the CT11 will reduce risk by ensuring Area 20) room could supply to Bus 15 and Bus 16 one off-site power source damage the cables and bus so that the CT11 source to the safeguards 4 kV Bus duct that supply off-site remains available to Bus 15 if a remains unaffected by a power (CT11 and 1 R fire damages Bus 16 or to Bus fire in the event of a fire in transformers) to Bus 15 16 if a fire damages Bus 15. the opposite train and Bus 16 due to common safeguards 4 kV Bus room.

power supply. The Provide fuse/breaker redundant diesel generator coordination for the CT12 remains unaffected by a supply to Bus 25 and Bus 26 fire to re-power the so that the CT12 source unaffected 4 kv safeguards remains available to Bus 25 if a bus (Bus 15 or Bus 16), but fire damages Bus 26 or to Bus risk is higher than desired. .26 if a fire damages Bus 25.

Modify associated control Unit 2 is similar to Unit 1. A cables (1 CS-1, 1CS-2, 1CS-3, fire in Fire Area 117, BUS and 1CS-4) so the CT11/CT12 25 or Fire Area 118, BUS source remains available for 26, could damage cables the opposite Bus room.

for both off-site power sources (2RY and CT12 transformer). The redundant Emergency Diesel Generator (D5/D6) remains unaffected by a fire, but the risk is higher than desired.

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Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification FPRA Measure Characterizati on 25 Medium 1 A fire in Fire Area 32 could Re-power MV-32078 from an Yes No This will reduce risk by damage cables required to MCC that is not located in Fire ensuring a fire in FA 32 open MV-32077 and MV- Area 32 to re-gain the ability to does not damage the ability 32078 to provide recirculate water from Sump B. to recirculate water from recirculation from Sump B. Sump B.

26 Medium 2 A fire in Fire Area 31 could Re-power MV-32180 from an Yes No This will reduce risk by damage cables required to MCC that is not located in Fire ensuring a fire in FA 31 open MV-32180 and MV- Area 31 to re-gain the ability to does not damage the ability 32181 to provide recirculate water from Sump B. to recirculate water from recirculation from Sump B. Sump B.

27 High 1, 2 A fire in the Control Room Install switches in the Control Yes No This will reduce risk by (Fire Area 13) or the Relay Room to isolate Pressurizer providing an additional way and Cable Spreading PORV, and Pressurizer to isolate Pressurizer Room (Fire Area 18) could Heaters. PORV, and isolating cause spurious opening of Pressurizer Heaters from valves that could lead to a the control room.

loss of inventory.

28 DELETED DELETED DELETED 29 DELETED DELETED DELETED 30 Medium 2 A fire in Fire Area 31 could Modify risk significant cable Yes No This will reduce risk by damage cables that provide (2DCA-1 0) from risk significant ensuring DC power DC power to vital fire initiators in Fire Areas 31. remains available for auxiliaries which impacts control and instrumentation risk. for fire in FA 31.

31 DELETED DELETED DELETED 32 Medium 2 A fire in Fire Area 32 could Modify cable 1C-2278 from Yes No This will reduce risk by damage cable 1C-2278 failing 21 Motor Driven Cooling ensuring the availability of which could affect control Water Pump in Fire Area 32. the 21 MDCLP for a fire in for BKR-23-4 which powers FA32.

the 21 Motor Driven Cooling Water Pump (21 MDCLP).

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Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification FPRA Measure Characterizati on 33 1 A fire in Fire Area 32 could Modify cable 1DCB-18 from fire Yes No This will reduce risk by Medium damage the cable that damage in Fire Area 32. ensuring the availability of provides DC control power DC power to PNL-16 to to PNL-16 which supports provide vital Instrumentation. instrumentation.

34 Medium 1, 2 A fire in FA 13, 18, 32 or 58 Modify cables to prevent Yes No This will reduce risk by could damage cables and spurious closure from risk making modifications to cause spurious closure of significant fire initiators. reduce the number of fire the Emergency Diesel scenarios that could cause Generator output breaker. fire damage to a 4kV This could cause a lockout safeguards bus.

of the 4kv safeguards Bus which powers one train of safeguards equipment.

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Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification FPRA Measure Characterizati on 35 Medium 1 A fire in Fire Area 32 or 58 Modify cable 1C-332 from fire Yes Yes The proposed modification could damage cables which damage in Fire Area 32 and 58 will reduce risk because it support operation of the to ensure BUS 16 can be will reroute cables 1RY offsite power sources powered from the 1RY associated with the to BUS 15 (BKR-15-3) and transformer. opposite train of equipment BUS 16 (BKR-16-2). to another FA. This will limit the number of fire scenarios that could damage both trains of equipment.

Compensatory measures in accordance with the Current Fire Protection Licensing Basis are being maintained.

Compensatory measures will continue to remain in effect after the NFPA 805 fire protection program becomes effective until this modification is complete.

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Northern States Power- Minnesota Attachmen tS- Modificatio ns and Implementa tion Items Table S-2 Plant Modificatio ns Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modificatio n FPRA Measure Characteriz ation 38 N/A 1, 2 A fire in Fire Areas 31, 32, Install control power fuses for No Yes This modification does not 58/73, 18, or 13 could the control circuits to provide have a significant impact damage control cables for over-current protection for the on the Fire PRA model the11or21 DC DC Emergency Turbine because the 11 and 21 Emergency Turbine Bearing Oil Pumps. Emergency Oil Pumps are Bearing Oil Pump that are not credited. The Fire PRA not adequately fused to model does not directly protect from over-current model common enclosure conditions. The control concerns.

cables could over-heat due to excessive current flow.

Since the cables are routed in multiple fire areas, this is a common enclosure concern.

39 N/A 1, 2 The 121 Motor Driven Fire Modify the Fire Pump alarm in No No This modification does not Pump (MDFP) loss of the control room to include the have an impact on the Fire power alarm is local at the loss of power alarm. PRA because the loss of pump in the screen house power alarm does not and does not currently affect functionality of the alarm to the control room. 121 MDFP. It is an NFPA This does not meet NFPA 805 code compliance 20 requirements. concern.

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Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification FPRA Measure Characterizati on 41 Medium 1, 2 A fire in Fire Area 13 or 18 Re-wire the torque and limit Yes Yes The proposed modification could damage cables that switches so fire induced will allow the valve to be could over-torque motor damage to cables in FA 13 and locally operated to credit operated valves; MV- 18 cannot bypass the torque this recovery action in the 32006, MV-3201 0, MV- and limit switches and PRA.

32021, MV-32022, MV- subsequently over-torque the 32238, and MV-32246 MOV. Compensatory measures in which are credited in the accordance with the current Fire PRAto be locally Fire Protection Licensing operated to perform Basis are being Recovery Actions. maintained.

Compensatory measures will continue to remain in effect after the NFPA 805 fire protection program becomes effective until this modification is complete.

42 N/A 1 Wiring above suspended Bring Fire Area 8 Locker No No This modification will ceilings in Fire Area 8 Room, Unit 1, 715' in the restore compliance with Locker Room, Unit 1, 715' southeast corner into NFPA 805 requirements. It in the southeast corner is compliance with NFPA 805, is not modeled in the Fire not in compliance with the Section 3.3.5.1. PRA for risk significance.

requirements of NFPA 805.

Compensatory measures in accordance with the fire protection licensing basis will be maintained until the modification is complete.

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Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-2 Plant Modifications Committed In Comp Risk Informed Item Rank Unit Problem Statement Proposed Modification FPRA Measure Characterizati on 43 N/A 1, 2 Fire Protection Barriers Upgrade Fire Protection No No This modification will required by NFPA 805 not Barriers required by NFPA 805 restore compliance with in compliance with the to meet the requirements of NFPA 805 requirements. It requirements of NFPA 805. NFPA 805, Section 3.11. is not modeled in the Fire PRA for risk significance.

Compensatory measures in accordance with the fire protection licensing basis will be maintained until the modification is complete.

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Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-3, Implementation Items provided below are those items (procedure changes, process updates, and training to affected plant personnel) months that will be completed prior to implementation of the new NFPA 805 fire protection program. This will occur within the later of twelve (12) that Item 20, Item 66 and Item 70 after NRC approval, or twelve months after a refueling outage if one is in progress at the time of approval. Note are associated with modifications described in Table S-2 and will be completed 180 days after modifications are complete.

Table S-3 Implementatio n Items Item Unit Description LAR Section I Source 1 1, 2 Implement monitoring program required by NFPA 805 Section 2.6 4.6.2, Attachment A Section 3.2.3(3) in accordance with NFPA 805 FAQ 10-0059, including a process that reviews the FPP performance and trends in performance.

2 1, 2 Revise plant procedure 5AWI 3.13.3, "Hot Work," to address the Attachment A Section 3.3.1.3.1 following: Attachment A Section 3.3.1.3.3 Attachment D

-Address the requirements for hot tapping. (NFPA 51 B-1999, Section 3-5)

-Address the requirements for a fire watch where torch-applied roofing hot work operations are in effect. (NFPA 241-1999, Section 5.1.3.2)

-Address the requirement that open flames or combustion-generated smoke shall not be permitted for leak or air flow testing.

-Consider delaying hot work in the vicinity of risk significant components during High Risk Evolutions 3 1, 2 Revise procedure F5 App J, "Fire Drills," to require that fire Attachment A, Section 3.4.3 (C)(3) brigade drills be conducted in various plant areas.

4 1,2 Perform a calculation to demonstrate that the fire water supply is Attachment A Section 3.5.1 capable of delivering the largest design demand with the hydraulically least demanding portion of fire main loop out of service in accordance with NFPA 805 requirements.

5 N/A DELETED N/A 6 1, 2 Revise procedure F5, "Firefighting," Section 7, to include a Section Attachment E 7.5, Control of Spread of Contamination, to address ventilation, floor drains, opening walkways or stairs between areas, and salvage/overha ul activities.

PINGP Page S Revision 3

Northern States Power- Minnesota AttachmentS- Modifications and Implementation Items Table S-3 Implementation Items Item Unit Description LAR Section I Source 7 1, 2 Revise Fire Brigade Training Lesson Plans to address the spread Attachment E of contamination during firefighting activities.

8 1, 2 Revise Fire Brigade Training Lesson Plans to identify the Attachment E responsibilities of each brigade member relative to limiting the spread of cross contamination when fighting fires in radiologically controlled areas.

9 1, 2 Revise Fire Brigade Training Lesson Plans to provide sufficient Attachment E details on the impact of fire fighting activities on the potential spread of contamination, and the methods available for mitigating such cross contamination via ventilation and drainage control.

10 1, 2 Revise procedure F5 App A, "Fire Strategies", to include Attachment E information on potential cross-contamination for each fire area.

11 1, 2 Revise procedure F5, "Firefighting", Section 2.7 to address Attachment E potential access requirements for the Duty RP Tech or Chemist.

12 1, 2 Revise Radiation Protection Continuing Training to address Attachment E control of contamination during firefighting activities.

13 1, 2 Revise procedure F5, App A, "Fire Strategies" to address the Attachment E ability to utilize the Auxiliary Building Special Ventilation, Containment Internal Cleanup Subsystem, Containment Purge, Containment In-Service Purge, and Shield Building Ventilation System for the removal of potentially contaminated smoke in fire areas identified in Attachment E.

14 N/A DELETED N/A 15 1, 2 Provide a container with booms, portable filtered ventilation, and Attachment E other appropriate equipment for the containment of water in the Low Level Rad Waste Enclosure.

16 Provide procedures to utilize a combination of containerization and Attachment E 1' 2 administrative controls to ensure that exposed contaminated waste in the Low Level Rad Waste Enclosure are kept as low as reasonably achievable.

17 1, 2 Revise F5 App F, "Fire Hazards Analysis" to align with the fire Attachment I area descriptions listed in Attachment I.

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Northern States Power- Minnesota AttachmentS- Modifications and Implementation Items Table S-3 Implementation Items Item Unit Description LAR Section I Source 18 N/A DELETED N/A 19 N/A DELETED N/A 20 1, 2 Update the Fire PRA Model, as necessary, after all modifications, 4.8.2 procedure changes, and other risk-relevant items identified in PRA RAI15.a Tables S-1, S-2, and S-3 are complete and as-built. If the revised Fire PRA indicates an increase in risk metrics such that the RG 1.205 acceptance guidelines are not met, changes will be made such that the Fire PRA results will fall within the acceptance guidelines. These changes may include additional analysis, procedure enhancements, plant modifications, or other changes determined necessary to reduce the overall risk metrics to within the acceptance guidelines.

21 N/A DELETED N/A 22 1, 2 Create new Fire Protection Design Basis Document to reflect 4.7.1 content requirements of NFPA 805.

23 N/A DELETED N/A 24 N/A DELETED N/A 25 1, 2 Provide a Change Evaluation Process procedure in accordance 4.7.2 with the requirements of NFPA 805. Ensure the process includes peer reviews to be performed on changes that are PRA upgrades, as defined in the PRA standard.

26 1, 2

• Develop qualification requirements and position-specific training 4.7.3 for personnel involved with the Fire PRA.

27 1, 2 Revise procedure 5AWI 3.13.0, "Fire Protection Program," to add 4.3.2 and Attachment D Non Power Operations (NPO) overview, definitions; road map; and risk reduction requirements for all NPO, and High Risk Evolutions (HRE).

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Northern States Power- Minnesota Attachmen tS- Modificatio ns and Implementa tion Items Table S-3 Implementa tion Items Item Unit Description LAR Section I Source 28 1, 2 Revise GEN-PI-059, "1 OCFR50, App R, Safe Shutdown Database 4.7.2 Data Verification" and other configuration control procedures which govern the various PINGP documents and databases that currently exist (or develop new procedures/ processes) to reflect the new NFPA 805 licensing bases requirements.

Revise system level design basis documents to reflect NFPA 805 4.7.2 29 1' 2 requirements and superseding of the old fire protection licensing basis.

N/A DELETED N/A 30 N/A DELETED N/A 31 N/A DELETED N/A 32 N/A DELETED N/A 33 34 1, 2 Revise Design Calculations ENG-EE-177, 194401-2.3-008, 4.5 and Attachment B 12911.6214-E-01 and ENG-EE-01 3 to support the Fire PRA credited power supply breaker- fuse coordination. Additionally, revise Design Calculation ENG-EE-17 7 per AR 01342798-0 2 to support the Loss of DC Control Power Analysis.

35 1, 2 Revise FP-OP-ROM -01, "Refueling Outage Management" 4.3.2 and Attachment D procedure for inclusion of NPO requirements.

36 N/A DELETED N/A 37 N/A Revise 5AWI 3.13.3, Hot Work to avoid hot work in certain areas N/A during high risk evolutions.

38 1,2 Revise F5 App K, "Fire Protection Systems Functional 4.3.2 and Attachment D Requirements" to contain the compensato ry actions to be implemented should a fire protection system required to be operable during HRE periods be found to be impaired.

39 1,2 Revise EM 3.4.1, "Review of Proposed Changes to the Fire 4.3.2 and Attachment D Protection Program" to contain guidance to ensure that changes to the fire protection program are reviewed for impact to the NPO requirements and risk reduction actions.

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Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-3 Implementatio n Items Item Unit Description LAR Section I Source 40 1,2 Revise SAWI 15.6.1, "Shutdown Safety Assessment" to contain 4.3.2 and Attachment D discussion on HRE, risk due to fire, NFPA 805 and the NPO requirements as part of risk management.

41 N/A DELETED N/A 42 N/A DELETED N/A 43 N/A DELETED N/A 44 N/A DELETED N/A 45 1 Revise 1C1.6, "Shutdown Operations- Unit 1" to contain a 4.3.2 and Attachment D requirement to maintain a continuous action to monitor T-Boil until the HRE can be exited then an HRE Risk Reduction Actions exit check list is provided.

46 2 Revise 2C1.6, "Shutdown Operations- Unit 2" to contain a 4.3.2 and Attachment D requirement to maintain a continuous action to monitor T-Boil until the HRE can be exited then an HRE Risk Reduction Actions exit check list is provided.

47 1 Revise 1C4.1, "RCS Inventory Control Pre-refueling" to contain a 4.3.2 and Attachment D requirement to maintain a continuous action to monitor T-Boil until the HRE can be exited then an HRE Risk Reduction Actions exit check list is provided.

48 2 Revise 2C4.1, "RCS Inventory Control Pre-refueling" to contain a 4.3.2 and Attachment D requirement to maintain a continuous action to monitor T-Boil until the HRE can be exited then an HRE Risk Reduction Actions exit check list is provided.

49 1 Revise 1C4.2, "RCS Inventory Control- Post Refueling" to contain 4.3.2 and Attachment D a requirement to maintain a continuous action to monitor T-Boil until the HRE can be exited then an HRE Risk Reduction Actions exit check list is provided.

50 2 Revise 2C4.2, "RCS Inventory Control- Post Refueling" to contain 4.3.2 and Attachment D a requirement to maintain a continuous action to monitor T-Boil until the HRE can be exited then an HRE Risk Reduction Actions exit check list is provided.

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Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-3 Implementatio n Items Item Unit Description LAR Section I Source 51 1, 2 Revise EM 3.4.3, "Safe Shutdown Circuit Analysis" to incorporate 4.3.2 and Attachment B applicable details of vendor document EPM-DP-EP-00 4, as well SSA RAI 03 as the methodology for analyzing twisted pair instrumentation and controls circuits as referenced in EC 20612, "PINGP Non-Power/NSCA Operations Review for NFPA 805."

52 1, 2 Develop a calculation titled "Nuclear Safety Capability Assessment Attachment B (NSCA) Analysis for Compliance with NFPA 805," to establish a design basis for the NSCA model and supporting analyses.

53 1, 2 Update GEN-PI-055, "1 OCFR50 Appendix R Manual Action 4.2.1.2 and Attachment T Feasibility Study," to reflect PINGP's transition to NFPA 805, SSA RAI 02 & SSA RAI 04. f including addition of new recovery actions, actions to maintain safe and stable conditions, and to document how the criteria, as defined by FAQ 07-0030, are met.

54 N/A DELETED N/A 55 N/A DELETED N/A 56 N/A DELETED N/A 57 1, 2 Revise procedure F5 App B "Control Room Evacuation (Fire)" to Attachment G direct the isolation of containment prior to leaving the control Attachment W room, add an optional attachment cross-tie power from opposite Unit if one Unit is in a Station Blackout, and to incorporate credited Recovery Actions.

58 1, 2 Revise F5 App D, "Impact of Fire Outside Control/Relay Room" as Attachment G and W required to include fire response HFEs in the Fire PRA Model and credited recovery actions from Attachment G.

59 N/A DELETED N/A 60 1, 2 Revise ENG-ME-353, "Mechanical MOV Analysis to Support Attachment B IN 92-18 Response" to incorporate updated vendor information as identified in AR 01422482.

61 1, 2 Verify that site procedures and compensatory measures for Generic RAI 32, Attachment L control of combustibles agree with assumptions in the Fire PRA.

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Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-3 Implementatio n Items Item Unit Description LAR Section I Source 62 1, 2 Perform an Evaluation for PNL 117 and PNL 217 to confirm the Attachment D and G loading capacity to supply more than one Instrument Bus.

63 1, 2 Provide procedural guidance to connect a diesel powered portable 4.2.1.2 generator located outside the power block to power a temporary SSA RAI 04 fan for the Main Control Room to maintain safe and stable conditions. Additionally, procedural guidance shall be provided for the operation, maintenance, storage, and refueling of the portable generator and for training and drills.

64 1,2 Update code compliance reviews to document resolution of FPE RAI-06 identified open items.

65 1,2 Develop procedural guidance to provide portable HEPA filters RR RAI-02 strategically located in the Radiological Controlled Area (RCA) that will be available for use based on radiological conditions as monitored by radiation protection personnel and as communicated to the fire brigade leader during fire events.

66 1,2 The PINGP Fire PRA model shall be reviewed using an NRC Updated PRA RAI-15 approved RCP seal model, as well as any exceptions/clarifications included in the NRC approval, to determine if the internal events and Fire PRA require a re~ision. The Prairie Island internal events and Fire PRA will be updated, if applicable, with the latest RCP seal information. If the updates result in a risk increase greater than RG 1.174, NSPM will take action to reduce the risk results.

Compensatory measures established prior to the RCP seal replacement shall remain in place until the calculated risk increase is within RG 1.174 limits.

67 N/A DELETED N/A 68 1, 2 Revise plant procedures to ensure that future wiring installation Attachment L above suspended ceilings in Power Block Areas will conform to NFPA 805 Section 3.3.5.1.

69 1, 2 Enhance the Internal Penetration Seal Program Attachment A PINGP Page S Revision 3

Northern States Power- Minnesota AttachmentS - Modifications and Implementatio n Items Table S-3 Implementatio n Items Item Unit Description LAR Section I Source 70 1, 2 NSPM will update the PINGP Fire PRA model using an PRA RAI21 NRC approved method for VEWFDS PRA credit. If the update results in a risk increase greater than RG 1.174, NSPM will take action to reduce the risk results. Applicable compensatory measures will remain in place until the calculated risk increase is within RG 1.174 limits.

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