ML081790666
| ML081790666 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 06/27/2008 |
| From: | Gerald Bichof Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 08-0326 | |
| Download: ML081790666 (9) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 10 CFR 50.90 June 27, 2008 U. S. Nuclear Regulatory Commission Serial No. 08-0326 ATTN: Document Control Desk NLOS/ETS R1 Washington, D. C. 20555 Docket No. 50-281 License No. DPR-37 VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNIT 2 PROPOSED LICENSE AMENDMENT REQUEST FIVE-YEAR CONTAINMENT TYPE A TEST EXTENSION REQUEST FOR ADDITIONAL INFORMATION (RAil By letter dated December 17, 2007 (Serial No. 07-0802), Virginia Electric and Power Company (Dominion) requested an amendment, in the form of a change to the Technical Specifications (TS) to Facility Operating License Number DPR-37 for Surry 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 HG 1.163 will allow the next Type A test to be performed no later than October 26, 2015.
In a March 20, 2008 letter, the NRC staff requested additional information regarding containment testing and inspection history, as well as the penetration test and inspection schedule during the five-year extended period. The requested information regarding the containment test and inspections was provided in a letter dated April 24, 2008 (Serial No. 08-0176). In a letter dated May 29, 2008, the NRC requested additional information regarding the risk assessment performed to support the five-year 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 17, 2007 Dominion letter (Serial No. 07-0802).
Serial No. 08-0326 Docket No. 50-281 page 2 of 3 If you have any questions or require additional information, please contact Mr. Thomas Shaub at (804) 273-2763.
Sincerely, Gerald T. Bischof Vice President - Nuc COMMONWEALTH OF VIRGINIA )
)
COUNTY OF HENRICO )
The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Gerald T. 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 t1? ~ay of ~~~~ , 2008.
My Commission Expires: \,L..!~~"--"ELJ-M:l~c...M' / / _ ~ /JI
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Notary Public Commitments made in this letter: None. VICKI L. HULL
Attachment:
- 1. Response to NRC Request for Additional Information -
COINMftW.-
CCMNftIIIlon IiIOIaIY PubIc of . . . .
.,. 1118 Containment Leakage Rate Test Program
Serial No. 08-0326 Docket No. 50-281 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 NRC Senior Resident Inspector Surry Power Station State Health Commissioner Virginia Department of Health James Madison Building - 7th Floor 109 Governor Street Room 730 Richmond, Virginia 23219 Mr. S. P. Lingam NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Rockville, Maryland 20852
Serial No. 08-0326 Docket No. 50-281 ATTACHMENT RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION CONTAINMENT LEAKAGE RATE TEST PROGRAM Virginia Electric and Power Company (Dominion)
Surry Power Station Unit 2
Serial No. 08-0326 Docket No. 50-281 Attachment Page 1 of 5 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION THE CONTAINMENT LEAKAGE RATE TEST PROGRAM
Background
By application dated December 17, 2007 (Agencywide Documents Access and Management System Accession Number ML073511682), Virginia Electric and Power Company (Dominion) proposed a license amendment to change Surry Power Station, Unit NO.2 (Surry 2) Technical Specifications (TS). The proposed change would permit a one-time 5-year exception to the 10-year frequency of the performance based leakage rate testing program for Type A tests, as required by Regulatory Guide (RG) 1.163. To complete our review of the proposed TS changes, the Nuclear Regulatory Commission staff requests that Dominion respond to the following:
NRC Question 1 Identify the Probabilistic Risk Analysis (PRA) version used to support the integrated leak rate testing extension request. Discuss the reasons for the significant change in the core damage frequency (CDF) and the intact containment frequency relative to the PRA version used to support license renewal (i.e., a reduction in CDF from 3.8E-5 to 2.93E-5/year and a reduction in intact containment frequency from 2.2E-5 to 3.17E-6/year.)
Dominion Response The PRA model used for the license renewal for Surry was issued in June 1997 and the associated CDF was 3.8E-05/yr. The reduction in the CDF from 3.8E-05/yr to 2.93E-05/yr is due to two model revisions since the issue of the 1997 model. There were several improvements/revisions between the release of the 1997 model and the 2000 model resulting in the reduction of the CDF. These changes include the following items.
Improved modeling of initiating event frequencies Periodic data update
- Additional credits of dis-allowed maintenance The reduction in the intact containment frequency from 2.2E-05/yr to 3.17E-06/yr was a result of the Level 2 model revision during 2003. The Level 2 model used for the 2007 ILRT submittal was revised in 2003 to update the model to current standards. The changes include a revision of the plant damage state (PDS) rules, assigning new PDS numbers to the Level 1 event trees and adding an additional branch for the non-LERF SGTR event. The changes made to the model resulted in a substantial drop in the intact containment frequency.
Serial No. 08-0326 Docket No. 50-281 Attachment Page 2 of 5 NRC Question 2 Table A-2 of Attachment 2 to your letter dated December 17, 2007, provides the estimated population dose for each Electric Power Research Institute (EPRI) accident class based on the frequency-weighed sum of the doses provided in Table A-I of your letter dated December 17, 2007. However, the population doses reported in Table A-2 for EPRI Classes 2, 7, and 8 are inconsistent with the frequency-weighted sum of the doses from Table A-I. Although the correct dose values were used for Classes 7 and 8 in the main report (e.g., Table 2 of your letter dated December 17, 2007), the incorrect dose value was used for Class 2. Please reconcile the population dose values provided in Tables A-I, A-2, and 2, and update the risk assessment as appropriate.
Dominion Response The 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. With the Class 2 dose revisions, the total baseline, 10 year, and 15 year dose rates remain unchanged. The summary results reflecting the revised dose values for Class 2 are provided in the attached table. The total increase in LERF resulting from a change in the Type A test interval is not impacted by this change.
NRC Question 3 The total large early release frequency (LERF) for Surry Power Station, including the requested change, is stated to be 9.79E-7 per year (page 18 of Attachment 2 of your letter dated December 17, 2007). However, this value does not include the contribution to LERF from external events. As stated in Section 2.2.4 of RG1.174, the risk-acceptance guidelines (in this case, for LERF) are intended for comparison with a full-scope assessment risk assessment, including internal and external events.
Consistent with this guidance, and to the extent supportable by the available risk models for Surry 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 Surry Power Station has external events models for fire and seismic. The baseline CDF for fire and seismic are 1.8E-05/yr and 1.0E-05/yr, respectively. The external events LERF values involving the Type A test interval (consistent with the methodology used for the requested change) are calculated and displayed in the table below.
Serial No. 08-0326 Docket No. 50-281 Attachment Page 3 of 5 Class 3BBase = CDF
- ProbClass-3B Class 3B10 = Class 3BBase * (10 year multiplier)
Class 3B15 = Class 3BBase * (15 year multiplier)
Where: ProbClass-38 = 0.0027 = probability of large pre-existing containment liner leakage.
10 year multiplier = 3.33 = the average time that a leak detectable only by a Type A test would go undetected from 18 months (3 yrs/2) to 60 months (10yrs/2). [60/18 = 3.33]
15 year multiplier = 5.00 = the average time that a leak detectable only by a Type A test would go undetected from 18 months (3 yrs/2) to 90 months (15yrs/2). [90/18 = 5.00]
Internal Events Class 388ase = 2.93E-05
- 0.0027 = 7.91E-08/yr Class 3810 = 7.91E-08
- 3.33 = 2.63E-07/yr Class 3815 = 7.91E-08
- 5.00= 3.96E-07/yr Class 388ase = 1.8E-05
- 0.0027 = 4.86E-08/yr Class 3810 = 4.86E-08
- 3.33 = 1.62E-07/yr Class 3815 =4.86E-08
- 5.00 = 2.43E-07/yr Seismic Class 388ase = 1.0E-05
- 0.0027 = 2.70E-08/yr Class 3810 = 2.70E-08
- 3.33 = 8.99E-08/yr Class 3815 = 2.70E-08
- 5.00 = 1.35E-07/yr
Serial No. 08-0326 Docket No. 50-281 Attachment Page 4 of 5 Internal Event LERF Fire LERF Seismic LERF Total LERF Class 7.91E-08/yr 4.86E-08/yr 2.70E-08/yr 1.55E-07/yr 388ase Class 2.63E-07/yr 1.62E-07/yr 8.99E-08/yr 5.15E-07/yr 3810 Class 3.96E-07/yr 2.43E-07/yr 1.35E-07/yr 7.74E-07/yr 3815 The total ALERF from the baseline to once-per-10 years (10 year metrics) is calculated as follows:
ALERF total = Class 3810 - Class 388ase
=5.15E 1.55E-07
= 3.60E-07/yr The current internal events LERF, including flooding, for Surry Power Station has been calculated to be 6.6E-07/yr. The internal events plus fire and seismic events yield a total LERF of 6.6E-07 + 1.2E-07 + 1.0E-07 = 8.82E-07/yr. This ALERF total increases the baseline LERF to 8.82E-07 + 3.60E-07 = 1.24E-06/yr.
The ALERF total from the baseline to once-per-15 years (15 year metrics) is calculated as follows:
ALERF total = Class 3815 - Class 388ase
= 7.74E 1.55E-07
= 6.19E-07/yr This ALERF total increases the baseline LERF to 8.82E-07 + 6.19E-07 = 1.50E-06/yr.
The guidance in Regulatory Guide 1.174 states that when the calculated increase in LERF is in the range of 1E-07 per reactor year to 1E-06 per reactor year, applications will be considered if the total LERF is less than 1E-05 per reactor year. The total LERF value for the 15 year change for SPS has been calculated to be 1.50E-06/yr. At this level, Regulatory Guide 1.174 defines a LERF increase of less than 1E-06 as a "small change." The risk impact due to the proposed 15-year ILRT meets this criterion. The summary of results reflecting the revised LERF calculations, and all other matters regarding the NRC RAI dated May 28, 2008 is provided in the following table.
Serial No. 08-0326 Docket No. 50-281 Attachment Page 5 of 5 Summary of Results Table 15yr Dose Base Dose Base Dose EPRI Base Freq Base (3/10) 10yr Freq 10yr Dose Rate 10yr 15yr Freq Rate 15yr Person- Rate Class I Rx-yr Freq 1 Rx-yr 1 Rx-yr Person-Rem/yr Metrics I Rx-yr Person- Metrics Rem Person-Rem/yr Rem/yr 1 3.17E-06 2.30E-06 5.98E+02 1.38E-03 2.77E-07 1.66E-04 O.OOE-OO O.OOE+OO 2 6.52E-10 6.52E-10 4.71E+05 3.07E-04 6.52E-10 3.07E-04 6.52E-10 3.07E-04 3A N/A 7.91E-07 5.98E+03 4.73E-03 2.63E-06 1.57E-02 3.96E-06 2.37E-02 3B N/A 7.91E-08 2.09E+04 1.65E-03 2.63E-07 5.50E-03 3.96E-07 8.28E-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 2.36E-05 2.36E-05 1.00E+05 2.36 2.36E-05 2.36 2.36E-05 2.36E+00 8 2.49E-06 2.49E-06 3.61 E+06 8.99 2.49E-06 8.99 2.49E-06 8.99E+00 TOTAL 2.93E-05 2.93E-05 N/A 11.36 2.93E-05 11.37 3.04E-05 11.38 (CDF) (CDF) (CDF) (CDF)
~DR Change 1.36E-02 2.42E-02 from Base ILRT DR
% of total 0.056% 0.186% 0.281%
dose
~% Change in ILRT DR 0.130% .0225%
from Base LERF 8.82E-07 1.24E-06 1.50E-06
~LERF 3.60E-07 6.19E-07 From base CCFP, % 89.5% 90.1% 87.0%
~CCFP, % 0.60% -3.0%
CDF 2.93E-05