ML100540605

RAI, Relief Request RR-ENG-2-52

ML100540605
Person / Time
Site:	South Texas
Issue date:	08/25/2009
From:	Thadani M Plant Licensing Branch IV
To:	Harrison A South Texas
Thadani, M C, NRR/DORL/LP4, 415-1476
Shared Package
ML100540530	List: ML100540561 ML100540605
References
TAC ME0899
Download: ML100540605 (2)

Text

REQUEST FOR ADDITIONAL INFORMATION RELIEF REQUEST RR-ENG-2-52 SOUTH TEXAS PROJECT NUCLEAR OPERATING COMPANY SOUTH TEXAS PROJECT UNIT2 DOCKET NO. 50-499 By letter dated March 12, 2009, South Texas Project Nuclear Operating Company, (the licensee) submitted a relief request for South Texas Project, Unit 2 (ADAMS Accession Number ML090830517). The licensee requested authorization to defer a code repair of a flaw identified in Unit 2 Essential Cooling Water (ECW) piping in lieu of the repair requirements of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, 1989 Edition, IWA-5250. To complete its review, the NRC staff requests the following additional information:

1. Discuss the time required to repair the subject degraded flange at return throttle valve 2-EW-1004 in the ECW system. The total repair time should include time to obtain parts, stage necessary materials, repair crew preparation, and time to complete the actual repair.

2. (a) Provide the flaw size that would cause a leak rate such that the ECW system could not provide sufficient make-up to fulfill the intended function of the ECW system. (b) Demonstrate that the detected flaw at the flange will not grow to the aforementioned flaw size prior to the scheduled repair in March 2010. (c) Provide the flaw analysis that was used to asses the through wall flaw in the degraded flange. (d) Discuss whether the flaw is in the circumferential or axial direction. (e) Provide the nominal diameter and pipe wall thickness of the degraded pipe/flange. (f) Discuss whether the detected flaw in the subject flange can be characterized as wall thinning or as a planar flaw.

3. In its Commitment as shown in Attachment 2 to the March 12, 2009 letter, the licensee stated that Perform monthly walkdowns of dealloying location to detect changes in size of the discolored area or leakage until a code repair is performed. Structural Integrity and the monitoring frequency will be re-evaluated if significant changes in the condition of the dealloyed area are found during this monitoring (a) The proposed monthly walkdown is contrary to the recommended frequency in NRC Generic Letter 90-05 which recommends that weekly walkdowns be performed to determine any degradation of structural integrity of the affected component. In light of GL 90-05 recommended weekly walkdowns, justify the monthly walkdown inspection.

Also, demonstrate that the proposed augmented inspection schedule will provide reasonable assurance that the operator has sufficient time to take corrective actions prior to the flaw in the flange growing uncontrollably to challenging operability of the affected ECW train.

(b) The ASME Code,Section XI, Code Case N-513-2, Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping Section XI, Division 1, paragraph (f) requires that for through wall leaking flaws, leakage shall be observed by daily walkdowns to confirm the analysis conditions used in the evaluation remain valid.

Discuss whether a daily walkdown will be performed if the subject flaw starts to leak. If a daily walkdown is not planned for a leaking flaw, discuss the examination frequency that will be used and justify the validity of the proposed examination frequency.

4. In its Commitment in Attachment 2 to the March 12, 2009 letter, the licensee stated that Rework of the defect will be deferred until adequate time is available for the repair, but no later than the next Unit 2 refueling outage, 2RE14 This statement is inadequate because it is vague and non-descriptive. (a) Clarify the meaning of Rework of the defect. (b) Identify the affected component in the Commitment. (c) Confirm that the degraded flange which is located downstream of Essential Cooling Water return throttle valve 2-EW-1004 from Essential Chiller 22B will be repaired in accordance with the ASME Code,Section XI, IWA-5250(a)(3), no later than May 5, 2010.

5. In Section 4 of Attachment 1 to the March 12, 2009 letter, the licensee stated that the flaw was identified on December 2, 2008. (a) Discuss the changes to the flaw since the discovery in terms of flaw dimensions and leakage, if any. (b) Discuss whether examinations were performed on all other ECW trains to identify similar flaws. Provide the results of the sample examinations. If sample examinations were not performed, provide the justification.

6. In Section 5 of Attachment 1 to the March 12, 2009 letter, the licensee used impracticality defined in Generic Letter 90-05 as the basis for the relief request. Generic Letter 90-05 defines impracticality as that the pipe cannot be isolated to complete a code repair within the time period permitted by the limiting condition for operation in the technical specification and a plant shutdown may be necessary to complete the code repair. (a) Discuss why the subject pipe cannot be isolated to complete a code repair. (b) It seems that it is not impractical to shut down the plant to repair the degraded flange. Shut down of the plant may result in hardship, but not impracticality. Explain why it is impractical to shut down the plant to repair the degraded flange.

7. In Section 6.2.2 (page 3) of Attachment 1 to the March 12, 2009, letter, the licensee stated that The condition of the ECW piping and the leakage is monitored by operator/personnel rounds. Sump level alarms are available to warm operators if unanticipated, sudden leakage were to develop (a) Discuss how often is the personnel rounds and whether the purpose of the personnel rounds is specifically geared toward examining flaws in the ECW piping. (b)

Describe the sensitivity of the sump level alarms (i.e., how low of a leak rate would the alarm annunciate) and at what leak rate will the operator take corrective actions.

8. In Section 6.2.2 (page 4) of Attachment 1 to the March 12, 2009, letter, the licensee stated that the VT-2 examinations at six-month intervals have proven to be an effective means of identifying flaws in ECW components. Given the existence of a through wall flaw in the subject flange, the staff believes that an examination frequency of every six month is inadequate and ineffective because by the time the VT-2 examination was performed the flaw had already initiated and grown through wall. Based on the operating experience of dealloying at the plant, the licensee needs to shorten the six-month examination interval for future ECW inspections or justify the adequacy of the six-month frequency for the VT-2 examination.

9. Enclosure 1, Section 3, of GL 90-05 specifies that the integrity of the temporary non-code repair of code class 3 piping should be assessed at least every 3 months by either ultrasonic testing (UT) or radiographic testing (RT). Discuss why these inspection methods were not specified in the proposed relief request.

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