ML12124A094
| ML12124A094 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 05/14/2012 |
| From: | Daily J License Renewal Projects Branch 1 |
| To: | Rencurrel D South Texas |
| Daily J 301-415-3873 | |
| References | |
| TAC ME4936, TAC ME4937 | |
| Download: ML12124A094 (6) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 May 14, 2012 Mr. D. W. Rencurrel Sr. Vice President, Technical Support and Oversight STP Nuclear Operating Company P.O. Box 289 Wadsworth, TX 77483
SUBJECT:
REQUESTS FOR ADDITIONAL INFORMATION FOR THE REVIEW OF THE SOUTH TEXAS PROJECT, UNITS 1 AND 2, LICENSE RENEWAL APPLICATION - AGING MANAGEMENT, SET 18 (TAC NOS. ME4936 AND ME4937)
Dear Mr. Rencurrel:
By letter dated October 25, 2010, STP Nuclear Operating Company (STPNOC or the applicant) submitted an application pursuant to Title 10 of the Code of Federal Regulations, Part 54, to renew operating licenses NPF-76 and NPF-80 for South Texas Project, Units 1 and 2, for review by the U.S. Nuclear Regulatory Commission (NRC or the staff). The staff is reviewing the information contained in the license renewal application and has identified, in the enclosure, areas where additional information is needed to complete the review.
These requests for additional information were discussed with Arden Aldridge, and a mutually agreeable date for the response is within 14 days from the date of this letter. If you have any questions, please contact me at 301-415-3873 or bye-mail at john.dally@nrc.gov.
Sincerely, J~:. ~,~r~nager Projects Branch 1 Division of License Renewal Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499
Enclosure:
As stated cc w/encl: Listserv
SOUTH TEXAS PROJECT, UNITS 1 AND 2, REQUEST FOR ADDITIONAL INFORMATION AGING MANAGEMENT, SET 18 (TAC NOS. ME4936 AND ME4937)
Instances of Recurrent Reactor Coolant Leakage (019)
RAI 3.2.2.1-1 a
Background:
By letter dated September 22, 2011, the staff issued RAI 3.2.2.1-1 requesting that the applicant state why the stainless steel closure bolting exposed to borated water leakage in LRA Table 3.2.2-4, Safety Injection System, was not managed for cracking. In its response dated November 21, 2011, the applicant stated that the bolting was in an ambient temperature less than 140°F; therefore, stress corrosion cracking is not an applicable aging effect.
NRC Inspection Report No. 05000449/2011005 dated February 13, 2012, describes safety injection (SI) system hot leg check valve 1N122XS10010A, on which a seal cap enclosure had been installed in 1997 due to reactor coolant leakage from the body to bonnet gasket. The enclosure surrounds the valve bolting, preventing direct inspection. The NRC inspection report also cites multiple occasions of leakage from the seal cap enclosure from 1997 to 2011, indicating that the leak from the bolted connection inside the enclosure was ongoing.
Another instance of borated water leakage is described in the "operating experience" program element of LRA Section B2.1.4, "Boric Acid Corrosion," which states that recurring coolant leakage in reactor coolant pump 2C resulted in the replacement of seal housing bolts in 2004 and 2009. The LRA also states that disassembly of this pump was scheduled for Refueling qutage 2RE15 in October 2011 to perform flatness checks of the seal.
Issue:
- 1. Given the multiple instances of reactor coolant leakage from the seal cap enclosure of SI system hot leg check valve 1 N122XSI001 OA, the stainless steel bolting within the enclosure may be submerged in a reactor coolant environment with a temperature greater than 140°F. The staff noted that the environment within the enclosure may not be sufficiently controlled for oxygen and other contaminants to preclude stress corrosion cracking. The LRA does not contain an AMR item to address the submerged environment and the potential for stress corrosion cracking. It is unclear to the staff how bolting within this and other seal cap enclosures will be age managed, since direct inspection is not possible.
- 2. Regarding the recurring borated water leakage from reactor coolant pump 2C, the staff does not have sufficient information to determine if the Boric Acid Corrosion program is effective at preventing recurring leakages.
ENCLOSURE
- 2 Request:
- 1. For all instances where pressure-retaining bolting is surrounded by seal cap enclosures:
- a. Describe the bolting alloy and the leaking water environment (Le., reactor coolant, secondary water).
- b. Add aging management review (AMR) items for the aging management of the bolting for loss of material, loss of preload, and cracking due to stress corrosion cracking, as appropriate, in the submerged environment. Provide technical justification for any cases where cracking due to stress corrosion cracking is not included as an applicable aging effect.
- c. If the aging management approach in item (b) does not include direct inspection of the bolting, provide technical justification for how the aging effects will be effectively managed during the period of extended operation.
- 2. Describe the results and any identified corrective actions from the reactor coolant pump 2C seal flatness checks to demonstrate the effectiveness of the Boric Acid Corrosion program.
Open Cycle Cooling Water System (021)
RAI B2.1.9-4b
Background:
RAI B2.1.9-4 requested the technical basis to demonstrate that loss of material due to worst case erosion in the essential cooling water (ECW) system will be adequately managed without protective coatings. The staff noted that the aging management program (AMP) basis document stated that coatings are not credited to protect metal surfaces. The response to the RAI stated that it was acceptable if coatings erode away between inspections because the piping inspections ensure that the piping is repaired or replaced before it reaches the minimum allowable wall thickness. The response also stated that the "wear rate is calculated from the measurement of wear and the previous inspection results, which is then used with conservatisms to calculate the lifetime of the component."
RAI B2.1.9-4a requested information, for locations where coatings are used in the ECW system, relating to the conservatisms used in the calculations that establish the continued acceptability of components. The response to RAI B2.1.9-4a stated that the piping at the flange connections to the 30-inch ECW throttle valves is coated and is managed for cavitation erosion. The response also stated that the coating is used sacrificially, is considered a short-lived commodity, and is replaced, as needed, during the 5-year preventive maintenance inspection. The response further stated that the program inspects for erosion of the piping and that an engineering evaluation is performed to determine the extent and depth of the erosion and whether the affected areas are acceptable for continued operation during the following 5-year period. The staff noted that the response did not provide the information requested relative to (a) the conservatisms used in the calculations that establish the lifetime of the piping, and (b) demonstrate that the coating is not credited to protect the metal surface.
-3 Issue:
Since the applicant states that it is acceptable for coatings to erode away between inspections, it is not clear to the staff how the acceptability of the component can be calculated because the amount of time that the coating has protected the component appears to be unknown. Because of the presence of a coating, the staff cannot evaluate how an accurate pipe material wear rate was determined. As a result, the staff would expect that the "conservatisms" noted above in the applicant's response would assume the worst case loss of material which could occur between inspections without any coating. The applicant neither defined the conservatisms used to calculate the lifetime of the component nor described how the conservatisms in the calculation were established.
Request:
For locations where coatings are used in the ECW system to sacrificially protect the pipe material, provide information to either (1) or (2) below, depending on the method used in the engineering evaluations which determine the acceptability of piping for continued operation until its next scheduled inspection.
- 1. If the method calculates a wear rate using the previously measured wall thickness value in combination with the currently measured wall thickness value, and the coating was present at any point between the times that the two measurements were taken, then explain precisely how the time period that was used to calculate the wear rate was adjusted to account for the amount of time that the coating protected the underlying material. In addition, quantify the conservatisms in the method that address thickness measurement uncertainties, the effects of flow rate variations, and any non-linear behavior in the phenomena causing the wall loss.
- 2. If the method uses a previously established wear rate which is not based on the difference between the current and prior wall thickness values, provide the details concerning how this previously established wear rate was determined. Include details regarding the conservatisms that address measurement uncertainties, the effects of flow rate variations, and any non-linear behavior in the phenomena causing the pipe material loss.
Letter to D. W. Rencurrel from John W. Daily dated May 14, 2012
SUBJECT:
REQUESTS FOR ADDITIONAL INFORMATION FOR THE REVIEW OF THE SOUTH TEXAS PROJECT, UNITS 1 AND 2, LICENSE RENEWAL APPLICATION - AGING MANAGEMENT, SET 18 (TAC NOS. ME4936 AND ME4937)
DISTRIBUTION:
E-MAIL:
PUBLIC RidsNrrDlr Resource RidsNrrDlrRpb1 Resource RidsNrrDlrRpb2 Resource RidsNrrDlrRerb Resource RidsNrrDlrRpob Resource RidsNrrDraApla Resource RidsOgcMailCenter JDaily TTran DMclntyre,OPA BSingal, DORL WWalker, RIV JDixon, RIV BTharakan, RIV WMaier, RIV VDricks, RIV NOKeefe, RIV AVegel, RIV GPick, RIV
Mr. D. W. Rencurrel Sr. Vice President, Technical Support and Oversight STP Nuclear Operating Company P.O. Box 289 Wadsworth, TX 77483
SUBJECT:
REQUESTS FOR ADDITIONAL INFORMATION FOR THE REVIEW OF THE SOUTH TEXAS PROJECT, UNITS 1 AND 2, LICENSE RENEWAL APPLICATION - AGING MANAGEMENT, SET 18 (TAC NOS. ME4936 AND ME4937)
Dear Mr. Rencurrel:
By letter dated October 25,2010, STP Nuclear Operating Company (STPNOC or the applicant) submitted an application pursuant to Title 10 of the Code of Federal Regulations, Part 54, to renew operating licenses NPF-76 and NPF-80 for South Texas Project, Units 1 and 2, for review by the U.S. Nuclear Regulatory Commission (NRC or the staff). The staff is reviewing the information contained in the license renewal application and has identified, in the enclosure, areas where additional information is needed to complete the review.
These requests for additional information were discussed with Arden Aldridge, and a mutually agreeable date for the response is within 14 days from the date of this letter. If you have any questions, please contact me at 301-415-3873 or bye-mail at john.daily@nrc.gov.
Sincerely, IRAJ John W. Daily, Senior Project Manager Projects Branch 1 Division of License Renewal Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499
Enclosure:
As stated cc w/encl: Listserv DISTRIBUTION:
See next page ADAMS Accession No ML12124A094 OFFICE LA: DLR/RPB1 PM: DLR/RPB1 Be: DLR/RPB1 PM: DLR/RPB1 NAME YEdmonds JDaily DMorey JDaily DATE 05/10/12 05/10/12 051 11 112 05/14/12 OFFICIAL RECORD COpy