L-PI-12-102, Supplement to License Amendment Request to Adopt NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactors - Submittal of Lnternal Flooding Peer Review Final Results and Revised Total Plant Risk Values
| ML12314A144 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 11/08/2012 |
| From: | Jeffery Lynch Northern States Power Co, Xcel Energy |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-PI-12-102 | |
| Download: ML12314A144 (6) | |
Text
Xcel Energy@
Prairie Island Nuclear Generating Plant 171 7 Wakonade Drive East Welch. MN 55089 L-PI-12-102 10 CFR 50.90 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 Supplement to License Amendment Request to Adopt NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactors - Submittal of lnternal Flooding Peer Review Final Results and Revised Total Plant Risk Values
Reference:
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, dated September 28, 2012 This letter provides supplemental information for the License Amendment Request (LAR) that was submitted in the referenced letter by Northern States Power Company, a Minnesota Corporation (NSPM), doing business as Xcel Energy. The subject LAR requested approval to adopt the NFPA 805 performance-based standard as the fire protection program licensing basis for the Prairie Island Nuclear Generating Plant (PINGP).
This LAR supplement provides final information regarding the peer review of the lnternal Flooding Probabilistic Risk Assessment (PRA). In addition, revised total plant risk values are provided to correct errors discovered in the lnternal Flooding PRA. As described below, the revised risk values remain below the acceptance criteria of Regulatory Guide 1.174.
lnternal Flooding PRA Peer Review Final Results In the NFPA 805 LAR, NSPM provided Draft information regarding the lnternal Flooding PRA peer review findings and observations, and committed to provide information in final form with dispositions in a supplement to the LAR by November 15, 2012. The attachment is a revision to LAR Table U-2, lnternal Events PRA Peer Review - Facts
Document Control Desk Page 2 and Obsen/ations. This attachment provides information from the final peer review report along with NSPM's disposition of each item. As shown in the revised Table U-2, each Finding is Closed, and each Finding was determined to not have an effect on the PlNGP Fire PRA. Information in the attached revised Table U-2 supersedes the "Draft" information previously submitted in Attachment U to the referenced LAR. In addition, statements in other parts of the LAR that refer to the lnternal Flooding PRA peer review information as "Draft," such as Section 4.5.1.I and Attachment V (Finding PRM-B2-01, pages V-I 1 and V-12), are also superseded.
Revised Total Plant Risk Values This supplement revises the total plant Core Damage Frequency (CDF) and Large Early Release Frequency (LERF) values presented in the referenced LAR, to correct errors discovered in the lnternal Flooding PRA. lnternal Flooding PRA risk values are not specifically identified in the referenced LAR, but they are included in the total plant risk values presented in Attachment W, Fire PRA Insights, under the heading Total CDF and LERF (page W-3). The revised total plant risk values are as follows (note: corrections were made only to the contributions from the lnternal Flooding PRA):
Total plant risk values reported in NFPA 805 LAR:
CDF (/reactor-vr)
LERF (/reactor-yr)
Unit 1 : 8.43 E-5 4.00 E-6 Unit 2:
9.84 E-5 7.15 E-6 Corrected total plant risk values:
CDF LERF Unit 1 : 8.59 E-5 4.02 E-6 Unit 2: 9.93 E-5 7.18 E-6 These values remain below the acceptance criteria in Regulatory Guide 1.I74 of 1 E-4 (CDF) and 1 E-5 (LERF).
The supplemental information provided in this letter does not impact the conclusions of the No Significant Hazards Evaluation or Environmental Considerations Evaluation presented in the referenced submittal.
In accordance with 10 CFR 50.91, NSPM is notifying the State of Minnesota of this LAR supplement 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 -388-1 121 x4137.
Summary of Commitments Submittal of the attached information completes Commitment No. 2 in the referenced letter, and this letter does not result in any new or otherwise changed commitments.
Document Control Desk Page 3 I declare under penalty of perjury that the foregoing is true and correct.
Executed on //fL2 Site vice president, Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc:
Administrator, Region Ill, USNRC NRR Project Manager, PINGP, USNRC Resident Inspector, PINGP, USNRC Minnesota Department of Commerce
ENCLOSURE Revised Table U-2, lnternal Events PRA Peer Review - Facts and Observations Prairie Island Nuclear Generating Plant (PINGP) License Amendment Request
/LAR) to Adopt NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactors This enclosure provides a revised Table U-2 for the PINGP NFPA 805 LAR. This table has been updated to replace "Draft" information provided in the LAR, submitted September 28, 2012, regarding the Internal Flooding PRA Peer Review.
2 Pages Follow
Northern States Power - Minnesota Anachment U - Internal Events PRA Quality PlNGP Page U-78 (Revised)
SR IFPP-B3-01 IFPP-A2-01 IFSN-A10-01 Table Topic Identification of assumptions Credit for sealed penetrations Credit for floor drains U-2 lnternal Status Closed Closed Closed Events PRA Peer Review - Facts and Observations FindinglObservation A parametric uncertainty analysis was performed on the final results. An evaluation of generic sources of model uncertainty from NUREG-1855 was documented. Although some of the plant specific sources of modeling uncertainty are documented in Table 18, not all key assumptions contained in the analysis documents are listed and evaluated for their potential effect on applications.
In defining the flood areas, assumption 6 of the accident sequence notebook states: "Sealed penetrations are assumed to be effective at preventing propagation between areas such that the propagation would result in equipment failure in the adjoining area." On page 169, the table states that for zone 41 9 the sealed penetration fails. This is in conflict with assumption 6.
The assumption states that no credit was taken for drains. However, the accident analyses and initiating event definitions discriminate based on flooding flow rates and area drain flows. As a result, there is a conflict between the documented analyses and Assumption 2 of the flood area definition notebook and the accident sequence analysis.
(Revised)
Disposition This issue deals with assumptions contained within the Flooding PRA Analysis. The lnternal Flooding documentation has been updated to document applicable assumptions and their potential contribution to model uncertainty. The assumptions associated with this Finding are lnternal Flooding related and do not have an effect on the Fire PRA.
This Finding deals with conflicting statements within the Flooding PRA Analysis regarding the propagation of a flood through a penetration. The lnternal Flooding documentation has been updated to clarify the conflicting wording. This Finding does not affect the Fire PRA.
This Finding deals with credit for drains in the Flooding PRA Analysis. The lnternal Flooding documentation has been updated to discuss how flood drains are credited. This Finding does not have an effect on the Fire PRA.
Northern States Power - Minnesota Attachment U - Internal Events PRA Quality PlNGP Page U-I9 (Revised)
Table U-2 Internal Events PRA Peer Review - Facts and Observations (Revised)
SR IFSO A1 -01 IFQU-A6-01 Topic Explanation of potential flooding source Application of internal events H FE's Status Closed Closed FindinglObservation The heating steam pipe is not considered a flooding source but there is no explanation for this.
There is no evidence that all the applicable HFE's from the internal events model were reviewed to see how they were affected by flood scenarios.
Disposition This Finding deals with heating steam piping as a flooding source in the Internal Events Flooding Analysis. The lnternal Flooding documentation has been updated to clarify why the heating steam pipe is not considered a flooding source. This Peer Finding has no effect on the Fire PRA or any of its postulated initiators.
This Finding is related to how internal events HFEs are applicable in the Flooding PRA analysis. To resolve this Finding a review of the HFE's credited in the lnternal Flooding Analysis was performed and documented. No changes to the HRA were required. This Finding does not have an effect on the Fire PRA Analysis. For the Fire PRA, each credited HFE was reviewed and modeled using industry accepted methods (i.e., NUREG 1921).