ML082050360

Proposed License Amendment Request, Response to Request for Additional Information One-Time Risk-Informed Extension to the Completion Time for Edf Fuel Oil Storage Tank Recoating

ML082050360
Person / Time
Site:	North Anna
Issue date:	07/22/2008
From:	Hartz L Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
08-0388
Download: ML082050360 (9)

Text

10 CFR 50.90 VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 July 22" 2008 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 Serial No.

08-0388 NL&OS/ETS RO Docket Nos. 50-338/339 License Nos. NPF-4/7 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

NORTH ANNA POWER STATION UNITS 1 AND 2 PROPOSED LICENSE AMENDMENT REQUEST REQUEST FOR ADDITIONAL INFORMATION ONE-TIME RISK-INFORMED EXTENSION TO THE COMPLETION TIME FOR EDG FUEL OIL STORAGE TANK RECOATING In a December 17, 2007 letter (Serial No. 07-0803), Dominion requested amendments, in the form of changes to the Technical Specifications to Facility Operating License Numbers NPF-4 and NPF-7 for North Anna Power Station Units 1 and 2. The proposed change will permit a one-time extended 14-day completion time for each of the two underground diesel fuel oil storage tanks to permit removal of the current coating and recoating of the tanks in preparation for use of ultra-low sulfur diesel (ULSD) fuel oil. In a June 24, 2008 letter the NRC requested additional information to complete the review of the proposed Technical Specification.

The information provided in this letter does not affect the conclusion of the significant hazards consideration discussion provided in the December 17, 2007 Dominion letter (Serial No. 07-0803).

Should you have any questions or require additional information, please contact Mr. Thomas Shaub at (804) 273-2763.

Very truly yours,

[~ff4tz:

Leslie N. Hartz Vice President -

uclear Support Services COMMONWEALTH OF VIRGINIA COUNTY OF HENRICO VICKI L. HULL Notary PuIIIc commonwealth of ""WInIO 1-"2 My Commlllion EXP~ May 11. 201.

The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Leslie N. Hartz, who is Vice President - Nuclear Support Service, of Virginia Electric and Power Company.

She has affirmed before me that she is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of her knowledge and belief.

Ild ~

Acknowledged before me this ;L-day of

, 2008.

My Commiesion Expiras: 5/3/ L(o.

~if~

I 7

(,i. '/5,

'kb Notary Public

Serial No. 08-0388 Docket Nos. 50-338/339 RAI-EDG FO Storage Tank Completion Time Extension Page 2 of 2 Commitments made in this letter:

Dominion commits to re-review the PRA model configuration control database prior to the implementation of the proposed Completion Time extension to reconfirm that the above evaluation remains valid.

Attachment Response to Request for Additional Information -

Extended Completion Time for EDG Fuel Oil Storage Tank Recoating cc:

U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30303 Mr. J. E. Reasor, Jr.

Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd.

Suite 300 Glen Allen, Virginia 23060 State Health Commissioner Virginia Department of Health James Madison Building - i h floor 109 Governor Street Suite 730 Richmond, Virginia 23219 NRC Senior Resident Inspector North Anna Power Station Mr. S. P. Lingam NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 0-8 G9A 11555 Rockville Pike Rockville, Maryland 20852

Serial No. 08-0388 Docket Nos. 50-338/339 Response to RAI for EDG FO Extended CT Attachment Request for Additional Information Extended Completion Time For EDG Fuel Oil Storage Tank Recoating North Anna Power Station Units 1 and 2 Virginia Electric and Power Company (Dominion)

Serial No. 08-0388 Docket Nos. 50-338/339

Background

In a December 17, 2007 letter (Serial No. 07-0803), Dominion requested amendments, in the form of changes to the Technical Specifications to Facility Operating License Numbers NPF-4 and NPF-7 for North Anna Power Station Units 1 and 2. The proposed change will permit a one-time extended 14-day Completion Time (CT) for each of the two underground diesel fuel oil storage tanks to permit removal of the current coating and recoating of the tanks in preparation for use of ultra-low sulfur diesel (ULSD) fuel oil. In a June 24, 2008 letter the NRC requested additional information to complete the review of the proposed Technical Specification.

NRC Question 1 The licensee's submittal identified that significant findings and observations (F&Os) from the 2001 peer review have either been resolved or found to have no impact on the proposed Technical Specification change. The licensee is requested to identify and provide its disposition of the unresolved significant F&Os with regard to this specific application.

Dominion response The open F&Os from the 2001 peer review were reviewed to identify which of the items have the potential to impact the risk insights for the proposed Technical Specification change.

There are no open

'~" level items.

None of the open "B" level F&Os were identified to impact the proposed Technical Specification change on the basis that the open F&Os do not affect accident sequences where the underground tanks are credited (Loss of Offsite Power events which are not recovered within the first few hours).

Table 0-2 below provides additional information on each open Level "B" F&O.

NRC Question 2 The licensee is requested to confirm that there are no outstanding (i.e., not incorporated into the baseline PRA model) plant modifications, procedure changes, or other outstanding deficiencies for the current PRA model such that it reasonably reflects the as-built as-operated plant.

Further, since this temporary change is not date-limited, provide a commitment to review the PRA results prior to implementation of the TS change to reconfirm this item.

Dominion response Dominion PRA model configuration control process requires plant changes (plant modifications, procedure changes etc.) to be collected and reviewed and those which could potentially affect the PRA model to be entered into the PRA model configuration control database.

Additionally, an estimate of the expected impact of the proposed model/documentation modifications on the relevant model is made and the implementations of the proposed change into the model are prioritized.

Page 1

Serial No. 08-0388 Docket Nos. 50-338/339 The proposed model changes in the PRA model configuration control database were reviewed to identify any proposed change that may impact the risk insights for the proposed UGFOST CT extension. These changes are categorized as follows:

Administrative Documentation There were no Administrative or documentation changes related to the UGFOST.

Model logic No changes or corrections to model logic were found related to the UGFOST.

There are several open items requesting improved modeling but these will typically lower the estimated plant vulnerability to a loss of UGFOST event and will not adversely impact the proposed TS change.

Plant/model components No model/plant component changes were found related to the UGFOST.

Investigation/Evaluation There were no questions to investigate or evaluate for the UGFOST. There are several open items requesting improved modeling but these will typically lower the estimated plant vulnerability and will not adversely impact the proposed TS change.

The consequential LOOP is under evaluation for modeling. However, given the significant margin in the figures of merit (CDF and LERF) for the proposed CT compared with the regulatory criteria for the low risk-significance threshold, as well as the conservative non-modeling of the fuel oil tank cross tie valve, it is judged that the potential inclusion of the consequential LOOP will not change the pertinent risk insights.

SelfAssessments Self Assessments did not identify any concerns or enhancements relevant to the UGFOST.

Operating Experience reviews There were no changes identified from OE review for the UGFOST.

There is an outstanding item to updating the LOOP frequency but the anticipated impact is small.

The LOOP frequency already includes the northeast U.S. blackout during August 2003.

Improvements/Enhancements No improvements or enhancements were identified.

Dominion commits to re-review the PRA model configuration control database prior to the implementation of the proposed CT extension to reconfirm that the above evaluation remains valid.

Page 2

Serial No. 08-0388 Docket Nos. 50-338/339 NRC Question 3 The licensee's submittal did not discuss model truncation applicable to its analysis.

The licensee is requested to identify and justify the truncation level used for this application.

Dominion response The North Anna average maintenance model truncation is set to 5 E-12 and yields a CDF of 5.4E-6/year.

The unavailability of a single UGFOST results in a CDF increase of less than 6E-7/yr, more than five orders of magnitude above truncation.

This margin is sufficiently high to ensure that the standard truncation is adequate.

Additionally, it is judged that the model results are stable at the above mentioned truncation value.

NRC Question 4 Section 5 of Attachment 2 of the licensee's submittal (December 17, 2007) identifies sensitivity calculations performed which purportedly support the risk analysis conclusions, however, the specifics of these calculations are not discussed. The licensee is requested to identify and discuss the results of the sensitivity calculations performed.

Dominion response These sensitivity calculations have been redone to support the risk analysis using the present North Anna model.

When integrated over the time of the proposed CT, the change in Core Damage Probability is still below the RG 1.174 and RG 1.177 limits. The table below presents the results.

Table D-1 Sensitivity Calculations Results Case CDF Chanae in CDF from base Base (eva. maintenance) 5.365 E-06/vr Base (avg. maintenance) with 1-EG-TK-2A 5.909 E-06/yr 5.44E-7/yr failed TK-2A unavailable and failure probability of TK-5.968 E-06/yr 6.03E-7/yr 2B increased to 95% upper limit TK-2A unavailable and failure probability of TK-6.103 E-06/yr 7.38E-7/yr 2B increased by a factor of 10 Page 3

Serial No. 08-0388 Docket Nos. 50-338/339 The open F&Os were evaluated against the proposed CT for the Underground Fuel Oil Storage Tank.

The results are summarized in the table below.

The UGFOST change is potentially applicable during any Loss of Offsite Power event that lasts longer than the time required to empty the day tanks for the Emergency Diesel Generators.

The FIOs were reviewed for potential impact on longer-duration LOOP mitigation.

F~~T/O~~~OI RA TEe........

NIsi.

Observation Summary Applicability OBSERVATION 10: AS-Several observations were identified These findings do not negatively 08

/

Element AS I regarding the event tree for AlWS at impact the accident sequences Sub-element 9 greater than 40% power.

where UGFOSTs are credited.

(Related Sub-elements:

TH-6, ST-4)

OBSERVATION 10: OE-IPE Appendix E, Internal Flooding, page These findings do not negatively 01

/

Element DE I E-17 establishes 511,000 gallons (44" impact the accident sequences Sub-element 3 above the Auxiliary Building basement where UGFOSTs are credited.

(Related Sub-elements:

floor elevation) as the minimum volume OE-10) [Also see related of water that could be allowed on this F&O OE-02]

elevation before any flood damage to equipment is sustained, assuming that the level equalizes across the whole floor.

OBSERVA TlON 10: OE -

Unit 2 cross-ties from Charging and These findings do not negatively 04

/

Element DE I Component Cooling Water were not impact the accident sequences Sub-element 10 considered in the flooding analysis, where UGFOSTs are credited.

(Related Sub-elements:

Appendix E of the IPE.

SY-5, SY-10, MU-4)

OBSERVATION 10: ST-The North Anna ISLOCA frequency is These findings do not negatively 01

/

Element ST I based on the evaluation performed in impact the accident sequences Sub-element 9 NUREG-1150 for Surry.

where UGFOSTs are credited.

OBSERVATION 10: ST-The AlWS analysis documentation does These findings do not negatively 02

/

ElementST I not clearly relate the analysis performed impact the accident sequences Sub-element 13 Also to the corresponding requirements of the where UGFOSTs are credited.

see F&O ST-01 and AS-generic analysis referred to.

08.

Page 4

Serial No. 08-0388 Docket Nos. 50-338/339 TableD"2 FACT/OBSERVAT1ONREGARDINGPRA TEe Observation Summary Applicability OBSERVATION 10: QU -

The limitations associated with PRA This is a documentation F&O. As 02/ Element QU I Sub-results should be clearly stated in the part of the analysis in support of element 7 (Related PRA Model Quantification calculation the proposed AOT extension, the Sub-elements: QU-34, notes (i.e., SM-1274, Revision 0), so that modeling limitations were MU-10)

ALSO SEE their relative importance to specific considered. These modeling F&O QU-09.

applications can be determined for each limitations did not have a negative application.

impact on the proposed UGFOST AOT extension. For example, one modeling limitation, non-modeling of the crosstie valves between UGFOSTs, was identified to have a positive impact (i.e., would decrease the delta risk).

OBSERVATION 10: L2 -

The North Anna early containment failure These findings do not negatively 02

/

Element L2 I conditional probability is based on the impact the accident sequences Sub-element 8 1992 IPE analysis which is based on where UGFOSTs are credited.

(Related Sub-elements:

NUREG-1150 assessments. This is L2-10) conservative in light of current knowledge of containment response and accident phenomenology.

OBSERVATION 10: L2 -

The North Anna early containment failure These findings do not negatively 03

/

Element L2 I conditional probability assessment does impact the accident sequences Sub-element 9 not include consideration of operator where UGFOSTs are credited.

(Related Sub-elements:

actions that may influence LERF but do L2-12, L2-25, MU-4) not impact the CDF. That is, only operator actions that impact the CDF are currently modeled in the PRA.

OBSERVATION 10: L2-There is no basis in the documentation The LERF model has been 04

/

Element L2 I for the LERF definition. The assignment revised and its documentation Sub-element 22 (Related of Source Term Categories to LERF is drafted. All review comments Sub-elements: L2-1 )

documented in SM-1090 (this is for with technical significance have Surry, but it was used as a surrogate for been resolved. LOOP events do North Anna), but the basis for the not involve containment bypass assignment is missing.

and are therefore not LERF limiting; thus no impact upon the proposed TS change is expected.

Page 5

Observation OBSERVA TION ID: L2 -

06

/

Element L2 I Sub-element 26 (Related Sub-elements: L2-28 )

OBSERVA TlON ID: L2 -

09

/

Element L2 I Sub-element 22 OBSERVA TION ID: L2 -

10

/

Element L2 I Sub-element 22 (Related Sub-elements:

ST-9)

Summary The most recent LERF model for North Anna could not be located. The LERF model for Surry (SM-1090) was made available by Dominion with the guidance that the North Anna model is identical to Surry.

All SGTR events and all Interfacing system LOCA events without pool scrubbing go to the LERF category. The LERF is dominated by SGTR events.

The reviewers noted that the interfacing system LOCA analysis uses a two inch pipe size as a screening criterion for bypass sequences, and believe that this is too high.

Page 6 Serial No. 08-0388 Docket Nos. 50-338/339 Applicability The LERF model has been revised and its documentation drafted. All review comments with technical significance have been resolved. LOOP events do not involve containment bypass and are therefore not LERF limiting; thus no impact upon the proposed TS change is expected.

These findings do not negatively impact the accident sequences where UGFOSTs are credited.

These findings do not negatively impact the accident sequences where UGFOSTs are credited.