ML14035A230
| ML14035A230 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 01/30/2014 |
| From: | Heacock D Dominion, Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 13-683 | |
| Download: ML14035A230 (8) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 January 30, 2014 U.S. Nuclear Regulatory Commission Serial No.13-683 Attention: Document Control Desk NL&OS/WDC RO Washington, DC 20555 Docket Nos. 50-338/339 License Nos. NPF-4/7 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)
NORTH ANNA POWER STATION UNITS I AND 2 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING NTTF RECOMMENDATION 2.3 FLOODING WALKDOWN REVIEW OF AVAILABLE PHYSICAL MARGIN ASSESSMENT On March 12, 2012, the Nuclear Regulatory Commission (NRC) issued "Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident" to all power reactor licensees and holders of construction permits in active or deferred status (hereafter called the 50.54(f) letter). Enclosure 4 of the 50.54(f) letter contains specific requested information associated with Near-Term Task Force (NTTF) Recommendation 2.3 for Flooding Walkdowns. In a letter dated November 27, 2012, Dominion submitted the walkdown report in response to the 50.54(f) letter.
In a letter dated December 23, 2013, the NRC transmitted a request for additional information (RAI) related to the flooding walkdown report and the determination of available physical margin (APM) for applicable flood protection features. The attachment to this letter provides Dominion's response to the NRC's RAI for North Anna Power Station.
If you have any questions regarding this information, please contact Mr. Thomas Shaub at (804) 273-2763.
Sincerely, David Heacock President and Chief Nuclear Officer Dominion Nuclear COMMONWEALTH OF VIRGINIA COUNTY OF HENRICO The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by David A.
Heacock, who is President and Chief Nuclear Officer Dominion Nuclear 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.
nwAND A 1D. CAF Acknowledged before me this .-0 day of 2 M 2014. 1 Notary Public I Commonwealth of Virginia My Commission Expires: Com mi sspeg. # 7520495 3 MMy Commission Expires January 31,#2075,4 Notary Public I1Dv
Serial No.13-683 Docket Nos. 50-338/339 Page 2 of 2 Commitments made in this letter: No new regulatory commitments
Attachment:
Response to Request for Additional Information Regarding Flooding Walkdowns cc: U.S. Nuclear Regulatory Commission, Region II Regional Administrator Marquis One Tower 245 Peachtree Center Ave. NE Suite 1200 Atlanta, Georgia 30303-1257 Dr. V. Sreenivas Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08 G-9A 11555 Rockville Pike Rockville, MD 20852-2738 K. R. Cotton Gross Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08 G-9A 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector North Anna Power Station J. E. Reasor, Jr.
Old Dominion Electric Cooperative Innsbrook Corporate Center, Suite 300 4201 Dominion Blvd.
Glen Allen, Virginia 23060
Serial No.13-683 Docket Nos. 50-338/339 ATTACHMENT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING FLOODING WALKDOWNS VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)
NORTH ANNA POWER STATION UNITS 1 AND 2
Serial No.13-683 Docket Nos. 50-338/339 Attachment, Page 1 of 5 NRC REQUEST FOR ADDITIONAL INFORMATION:
Flooding Walkdowns On March 12, 2012, the U.S. Nuclear Regulatory Commission (NRC) staff issued a letter (Agencywide Documents Access and Management System (ADAMS) Accession No. ML12053A340) requesting additionalinformation per Title 10 of the Code of Federal Regulations, Section 50.54(f (hereafter called the 50.54(f letter). The 50.54(f letter requested that licensees conduct flooding hazard walkdowns to identify and address plant-specific degraded, nonconforming, or unanalyzed conditions through the corrective action program (CAP). All licensees stated by letter that the flooding walkdowns would be performed in accordance with Nuclear Energy Institute (NEI) 12-07, "Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features," May 2012 (ADAMS Accession No. ML12172A038). Following the NRC staff's initial review of the reports documenting the results of the licensees' walkdowns, regulatory site audits were conducted at a sample of plants. Based on the walkdown report reviews and site audits, the staff identified additional information necessary to allow the staff to complete its assessments.
Determinationand documentation of available physical margin (APM)
Background:
The NRC staff observed that several licensees did not consistently determine and/or document available physical margin (APM) in a manner that met the expected interpretation of NEI 12-07 during audits associated with review of the NTTF Recommendation 2.3 report submittals. APM is defined in section 3.13 of NEI 12-07 and the process for obtaining and evaluating APM values is described in section 5.8 of NEI 12-07. Consistent with NEI 12-07, a numerical value for APM should be determined and documented for every applicable flood protection feature (e.g., wall, penetration, berm, door, etc.). This would normally be a numerical value reflecting the difference between the licensing basis flood height at the location of the feature and the point at which the function of the flood protection feature is compromised (e.g., the top of a barrieror the height of the first unsealed penetration in a barrier)such that the resulting flood can affect a structures, systems, and components important to safety.
Next, in accordance with Section 5.8 of NEI 12-07, if the APM appears to be small and the consequences of flooding appear to be significant, the licensee should enter the condition into the CAP and appropriate action be taken. While NEI 12-07 does not require that a specific numerical threshold value for "small"APM be defined for each site, doing so establishes a consistent basis for determining what instances need to be entered into the CAP. If a numerical APM value cannot be determined for any flood protection feature, the licensee should perform an assessment of the ability of the barrierto withstand the licensing basis flood plus the contribution of the additionalwater corresponding to the pre-established small-margin threshold value. If the barriercan withstand this flood, the APM for the feature is "not small" and further evaluation in accordance with Section 5.8 of NEI 12-07 is not required. It is further noted that
Serial No.13-683 Docket Nos. 50-338/339 Attachment, Page 2 of 5 conclusions regarding "large" values of APM should be based on engineering evaluations or existing design documents.
Licensees should ensure that the process for APM determination and evaluation used during theirflooding walkdowns is consistent with the guidance in NEI 12-07. The intent of this RAI is not to repeat the flooding walkdowns or perform an extensive revision of the walkdown record forms and other paperwork. Instead the purpose is to verify or modify the process used to determine APM such that every site is aware of the margin at each of its flood protection features and take appropriateinterim actions when the APM is small and the consequences are significant. Instances where numerical values for APM were not determined, or where the basis for the APM was found to be questionable, should be rectified by either the documentation of a specific value or an explanation of why a nun-numerical value is appropriate.
Request:
RAI 1
Pleaseprovide confirmation that the process for evaluatingAPM was reviewed.
Dominion Response Dominion has completed a review of the flooding design basis walkdown APM process for North Anna Power Station. As evidenced by the responses below, Dominion acknowledges that the guidance in NEI 12-07 (References 2 and 3) for determining APM needed further clarification to ensure consistent application for all flood protection features. Subsequent industry guidance in FAQ-030 (Reference 5) and the information in the NRC's RAI letter (Reference 6) were used to supplement the initial NEI 12-07 process and have been applied in a review of the results of the flooding walkdowns for North Anna Power Station. The current status is described further in the RAI responses.
RAI 2
Please provide confirmation that the APM process is now or was always consistent with the guidance in NEI 12-07 and discussed in this RAI.
Dominion Response Dominion followed the guidance provided in NEI 12-07 for the original walkdown effort, including a numerical definition for a small margin. However, a specific APM had not been assigned to the seals associated with flood protection features because a design pressure rating for the seals had not been identified. These items have now been addressed in accordance with FAQ-030 and the NRC's RAI letter and entered into the corrective action process (the CAP reference is CR538067), as appropriate, for further
Serial No.13-683 Docket Nos. 50-338/339 Attachment, Page 3 of 5 evaluation. The process used for the APM review is now consistent with the guidance provided in FAQ-030 and NEI 12-07.
RAI 3
If changes are necessary, a general description of any process changes to establish this consistency.
Dominion Response As noted above, changes were necessary to ensure consistent application of the guidance for establishing the APM for each flood protection feature. The process changes to establish this consistency are generally described as: 1) a review of each of the walkdown packages for the APM for each feature during a probable maximum flood (PMF) event, and 2) a corrective action to update the information for the APM for each feature during a local intense precipitation (LIP) event. The CAP reference number is CR538061.
The PMF APM values for flood protection features were generally consistent with the NEI 12-07 guidance, with the exception of seals as described in the response below.
The LIP APM information was found to be deficient because the height of flood water applicable to each flood protection feature was not available. Without defined area flood heights for a CLB LIP event, NEI 12-07, Paragraph 3.13.3, states that the APM for the particular flood hazard mechanism should be recorded as unknown and the protection height should also be recorded. Condition Report CR538061 was entered into the CAP to supplement the walkdown results for the LIP event to be consistent with the guidance in this paragraph of NEI 12-07. Also, the LIP APM values for flood protection features using a seal will be supplemented as described in the response below.
RAI 4
As a result of the audits and subsequent interactions with industry during public meetings, NRC staff recognized that evaluation of APM for seals (e.g., flood doors, penetrations, flood gates, etc.) was challenging for some licensees. Generally, licensees were expected to use eitherApproach A or Approach B (describedbelow) to determine the APM for seals:
a) If seal pressure ratings were known, the seal ratings were used to determine APM (similarto example 2 in Section 3.13 of NEI 12-07). A numerical value for APM was documented. No further action was performed if the APM value was greaterthan the pre-establishedsmall-margin threshold value. If the APM value was small, an assessment of "significantconsequences" was performed and the
Serial No.13-683 Docket Nos. 50-338/339 Attachment, Page 4 of 5 guidance in NEI 12-07 Section 5.8 was followed.
b) If the seal pressure rating was not known, the APM for seals in a flood barrieris assumed to be greater than the pre-establishedsmall-margin threshold value if the following conditions were met: (1) the APM for the barrier in which the seal is located is greater than the small-margin threshold value and there is evidence that the seals were designed/procured,installed, and controlled as flooding seals in accordance with the flooding licensing basis. Note that in order to determine that the seal has been controlled as a flooding seal, it was only necessary to determine that the seal configuration has been governed by the plant's design control process since installation. In this case, the APM for the seal could have been documented as "notsmall".
As part of the RAI response, state if eitherApproach A or Approach B was used as part of the initial walkdowns or as part of actions taken in response to this RAI. No additionalactions are necessaryif eitherApproach A or B was used.
If neitherApproach A or B was used to determine the APM values for seals (eitheras part of the walkdowns or as part of actions taken in response to this RAI), then perform the following two actions:
" Enter the condition into the CAP (note: it is acceptable to utilize a single CAP entry to capture this issue for multiple seals). CAP disposition of "undetermined" APM values for seals should consider the guidance provided in NEI 12-07, Section 5.8. The CAP disposition should confirm all seals can perform their intended safety function against floods up to the current licensing basis flood height. Disposition may occur as part of the Integrated Assessment. If an Integrated Assessment is not performed, determine whether there are significant consequences associated with exceeding the capacity of the seals and take interim action(s), if necessary, via the CAP processes. These actions do not need to be complete prior to the RAI response.
" Report the APM as "undetermined"and provide the CAP reference in the RAI response.
Dominion Response Dominion reviewed the walkdown package results for APM values related to seals as part of the actions taken in response to this NRC RAI letter. Approach A was not used.
For seven walkdown packages including flood protection seals, Approach B was used.
For the remaining seals, the condition was entered into the CAP with a single CAP entry addressing multiple seals. The APM for each of these seals was classified as "undetermined" in a supplement to the walkdown records. The CAP reference is CR538067.
Serial No.13-683 Docket Nos. 50-338/339 Attachment, Page 5 of 5
REFERENCES:
- 1. Letter dated March 12, 2012, from E.J. Leeds (NRC) to all power reactor licensees and holders of construction permits in active or deferred status, "Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f)
Regarding Recommendations 2.1, 2.3, and 9.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident"
- 2. Letter dated May 31, 2012, from D. L. Skeen (NRC) to Nuclear Energy Institute, "Endorsement of Nuclear Energy Institute (NEI) 12-07, "Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features"
- 3. Email letter dated June 11, 2012, from Jim Riley (NEI) to all Fukushima Points of Contact, "Guidance for Flooding Design Basis Walkdowns - Fukushima Short Term Activities," with NEI 12-07, Revision 0-A, as attachment
- 4. Letter, Serial No. 12-207G, dated November 27, 2012, from David A. Heacock (Virginia Electric and Power Company) to NRC, "North Anna Power Station Units 1 and 2 Report in Response to March 12, 2012 Information Request Regarding Flooding Aspects of Recommendation 2.3"
- 5. Letter dated October 31, 2013, from James H. Riley (NEI) to all Fukushima Points of Contact, "Available Physical Margin Determination," with FAQ-030 and FAQ-006 as attachments
- 6. Letter dated December 23, 2013, from R. J. Pascarelli (NRC) to David A. Heacock (Virginia Electric and Power Company, North Anna Power Station Units 1 and 2),
"Request for Additional Information Associated with Near-Term Task Force Recommendation 2.3, Flooding Walkdowns