ML080780256

Response to Request for Additional Information Regarding Proposed License Amendment Request One-Time Five-Year Extension to Type a Test Interval

ML080780256
Person / Time
Site:	North Anna
Issue date:	03/14/2008
From:	Gerald Bichof Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
08-0092
Download: ML080780256 (8)

Text

10 CFR 50.90 VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 March 14, 2008 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 Serial No.

NL.&OS/ETS Docket No.

License No.

08-0092 RO 50-339 NPF-7 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

NORTH ANNA POWER STATION UNIT 2 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATIOt~ REGARDING PROPOSED LICENSE AMENDMENT REQUEST ONE-TIME FIVE-YEAR EXTENSION TO TYPE A TEST INTERVAL In a December 5, 2007 letter (Serial No. 07-0769), Dominion requested an amendment, in the form of a change to the Technical Specifications to Facility Operating License Number NPF-7 for North Anna Power Station Unit 2.

The proposed change will permit a one-time five-year exception to the ten (10) year frequency of the performance-based leakage rate testing program for Type A tests as required by Regulatory Guide (RG) 1.163.

This one-time exception to the requirement of RG 1.163 will allow the next Type A test to be performed no later than October 9, 2014.

In a February 1, 2008 e-mail, the NRC requested additional information regarding the risk analysis performed to support the five-year interval extension.

The attachment to this letter provides the information requested by the NRC staff.

The information provided in this letter does not affect the conclusion of the significant hazards consideration discussion provided in the December 5, 2007 Dominion letter (Serial No. 07-0769).

Serial No. 08-0092 Docket No. 50-339 Request for Additional Information One-Time Five-Year Extension to Type A Test Interval Page 2 of 3 Should you have any questions or require additional information, please contact Mr. Thomas Shaub at (804) 273-2763.

Very truly yours, L~?!-6 Vice President - Nuclear Engineering Attachment

1. Response to Request for Additional Information Commitments made in this letter: None.

COMMONWEALTH OF VIRGINIA COUNTY OF HENRICO The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Gerald 1. Bischof, who is Vice President - Nuclear Engineering, of Virginia Electric and Power Company. He has affirmed before me that he 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 his knowledge and belief.

Acknowledged before me this /t"'"

day of Yl1.Mch

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CommoIlW-'" of YIfgfnIQ My CommIIIIOn.... Aug S1. 2001

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Notary Public

Serial No. 08-0092 Docket No. 50-339 Request for Additional Information One-Time Five-Year Extension to Type A Test Interval Page 3 of 3 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 Mr. R. A. Jervey 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. 08-0092 Docket No. 50-339 Response to Request for Additional Information One-Time Five-Year Extension to Type A Test Interval Attachment RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING PROPOSED LICENSE AMENDMENT REQUEST ONE-TIME FIVE-YEAR EXTENSION TO TYPE A TEST INTERVAL North Anna Power Station Unit 2 Virginia Electric and Power Company (Dominion)

Serial No. 08-0092 Docket No. 50-339 Response to Request for Additional Information One-Time Five-Year Extension to Type A Test Interval REQUEST FOR ADDITIONAL INFORMATION REGARDING PROPOSED LICENSE AMENDMENT REQUEST ONE-TIME FIVE-YEAR EXTENSION TO TYPE A TEST INTERVAL Request for Additional Information Regarding ILRT Interval Extension for North Anna Power Station Unit 2 NRC Question 1 Table 3 of Attachment 2 (December 5, 2007 letter) provides the estimated population dose for each accident class as well as the total population dose summed over all accident classes.

The total population dose in Table 3 (37.31 person-rem per year) is substantially higher than the value reported in the Severe Accident Mitiqation Alternative (SAMA) analysis submitted in support of North Anna license renewal (25.4 person-rem per year). The difference appears to be due to a higher population dose value for Class 2 events in Table 3 (1.85E+06 person-rem per event) relative to the frequency-weighted sum of the population dose values for Class 2 events in Table A-1 (1.18E+04 person-rem per event).

Use of the higher dose values leads to an under-estimate of the percent increase in the population dose resulting from the ILRT interval extension.

Please reconcile the population dose values with those in the SAMA analysis, and provide a reassessment of the impact of the ILRT interval extension on population dose based on appropriate population dose values.

Dominion Response Your observation is correct.

Thus, the Class 2 dose has been frequency-weighted and the revised dose values have been propagated through the baseline, 10 year, and 15 year metrics. The total baseline, 10 year, and 15 year dose rates are 25.46,25.47, and 25.48 person-rem per year, respectively.

The summary results reflecting the revised dose values are provided in the following table. The total increase in LEIRF resulting from a change in the Type A test interval from once-per-ten years to once-per-fifteen years was not impacted by this change.

Page 1 of 4

NAPS PROBABILISTIC RISK ASSESSMENT NOTEBOOK Part V, Volume L.I.3, REVISION 2 Risk Analysis Calculation of 5 year integrated Leak Rate Test Extension for Unit 2 Serial No. 08-0092 Docket No. 50-339 RAI - One-Time Five-Year Extension to Type A Test Interval P.27 I

Updated Summary of Results*

EPRI Base Freq Base (3110)

Base Dose Base Dose Rate 10yr Freq/

lOyr Dose Rate 10yr 15yr Freq 15yr Dose Rate 15yr Class

/ Rx-yr FreQ / Rx-vr Person-Rem Person-Rem / yr Rx-yr Person-Rem / yr Metrics

/ Rx-yr Person-Rem/vr Metrics I

1.76E-05 1.66E-05 4.24E+02 7.04E-03 lo4lE-05 5.98E-03 1.24E-05 5.26E-03 2

6045E-06 6045E-06 1.I8E+04 7.61E-02 6045E-06 7.61E-02 6045E-06 7.61E-02 3A N/A 9045E-07 4.24E+03 4.0IE-03 3.15E-06 1.34E-02 4.73E-06 2.0IE-02 3B N/A 9045E-08 1.48E+04 lo40E-03 3.15E-07 4.66E-03 4.73E-07 7.00E-03 4

N/A N/A N/A N/A N/A N/A N/A N/A 5

N/A N/A N/A N/A N/A N/A N/A N/A 6

N/A N/A N/A N/A N/A N/A N/A N/A 7

4.99E-06 4.99E-06 5.68E+04 0.28 4.99E-06 0.28 4.99E-06 0.28 8

5.89E-06 5.89E-06 4.26E+06 25.09 5.89E-06 25.09 5.89E-06 25.09 TOTAL 3.50E-05 3.50E-05 N/A 25.46 3.50E-05 25.47 3.50E-05 25.48 (CDF)

(CDF)

(CDF)

(CDF) i1DRChange 1.15E-02 1.99E-02 from Base ILRTDR 0.021 0.071 0.106

% oftotal dose i1%Change 0.050 0.085 in ILRT DR from Base LERF 8.20E-07 1.04E-06 1.20E-06

~LERF 2.21E-07 3.79E-07 From base CCFP, %

49.9 50.7 51.1 i1CCFP, %

0.80 1.2 CDF 3.50E-05

• Reflects use offrequency weighted Class 2 doses Page 2 of 4

Serial No. 08-0092 Docket No. 50-339 Response to Request for Additional Information One-Time Five-Year Extension to Type A Test Interval NRC Question 2 The total large early release frequency (LERF) for North Anna Power Station, including the requested change, is stated to be 1.04E-6 per year (page 20 of Attachment 2 to the December 5, 2007 request.).

However, this value does not include the contribution to LERF from external events.

As stated in Section 2.2.4 of Regulatory Guide 1.174, the risk-acceptance guidelines (in this case, for LERF) are intended for comparison with a full-scope risk assessment, including internal and external events.

Consistent with this guidance, and to the extent supportable by the available risk models for North Anna Power Station, provide an estimate of the total LERF when external events and the impact of the requested change are included within the assessment.

Dominion Response As previously discussed, an updated external events PRA model is not available for North Anna Power Station (NAPS).

The Individual Plant Examination of External Events (IPEEE) includes an analysis of fire initiating events.

No seismic PRA analysis is available for North Anna since the seismic margins method was used for the IPEEE.

The IPEEE evaluated core damage frequency (CDF), but did not evaluate large early release frequency (LERF).

The CDF from fire initiating events was calculated to be 4.10E-06/yr in the IPEEE.

The IPEEE concluded that containment leakage is not impacted by fire.

Because the EPRI methodology for the Type A test extension request assigns a fraction of the CDF to LERF due to containment failure, a similar calculation can be done with the fire CDF to estimate the fire LERF. The fire LERF is estimated by using the internal events ratios of the Class 3B frequencies for the Baseline, 10 year, and 15 year test interval to the CDF.

Based on the ratio of Class 3B frequency to thl9 CDF, the fire LERFs are as follows:

1 dl F"

~.*

t F "I Ttl LERF D t

C tal oa ue 0

on mmen at ure nc u mg Ire' Internal Events Ratio Internal Events Fire LERF Total LERF Due to (Class 38 / 3.50E-05)

LERF Due to (4.10E-06

• Internal Class 38 Events Class 38 Events Ratio)

(Internal and Fire Events Events)

Baseline 0.0027 9.45E-08/yr 1.11E-08/yr 1.06E-07/yr 10 year 0.0090 3.15E-07/yr 3.69E-08/yr 3.52E-07/yr 15 year 0.0135 4.73E-07/yr 5.54E-08/yr 5.28E-07/yr

• • Note: All LERF values are based on the Class 38 values Page 3 of 4

Serial No. 08-0092 Docket No. 50-339 Request for Additional Information One-Time Five-Year Extension to Type A Test Interval The total L1LERF from once-per-10 years to once-per-15 years (5 year metrics) is calculated to be the difference between the total LERF values in the table above.

L1LERF = 15 year - 10 year 6LERF =5.28E 3.52E-07 =1.76E-07/yr The current total baseline internal events and fire LERF for NAPS is estimated to be 8.31E-07/yr [i.e., 8.20E-07(baseline LERF) + 1.11E-08 =8.31E-07/yr].

The impact of summing estimates of fire LERF with the internal event LERF is consistent with a "small change" per RG 1.174.

Page 4 of 4