ML091600307

Units, 1 & 2 - Response to Request for Additional Information Concerning Relief Request ISI-04-04

ML091600307
Person / Time
Site:	Calvert Cliffs
Issue date:	06/09/2009
From:	Calvert Cliffs, Constellation Energy Group
To:	Office of Nuclear Reactor Regulation
Shared Package
ML091600309	List: ML091600302 ML091600307
References
Download: ML091600307 (3)

Text

ATTACHMENT (1)

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION ON RELIEF REQUEST ISI-04-04 Calvert Cliffs Nuclear Power Plant, Inc.

June 9, 2009

ATTACHMENT (1)

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION ON RELIEF REQUEST ISI-04-04 NRC RAI 1:

Section 3.3.1 of your submittal dated December 29, 2008, addresses Additional Examinations. The submittal states in part that, The process for ordinary flaws is to perform the evaluation using ASME Code,Section XI.

Please explain the term ordinary flaws and/or confirm that all flaw evaluations are performed using ASME Code,Section XI.

CCNPP Response:

Ordinary flaws refers to the normal process of evaluating flaws and all flaw evaluations are performed using American Society of Mechanical Engineers (ASME) Code,Section XI.

NRC RAI 2:

Table IWB-2500-1 of American Society of Mechanical Engineers,Section XI, 2001 Edition with 2004 Addenda requires volumetric and/or surface examination of all Category B-F or B-J Pressure Retaining Dissimilar Metal Welds greater than nominal pipe size (NPS) 1. Based on recent findings of primary water stress-corrosion cracking in Alloy 82/182 dissimilar metal welds, the staff would like more information on your inspection plans for these welds in the 4th Interval ISI Plan for Calvert Cliffs Nuclear Power Plant (CCNPP).

Please describe the inspection plan of Alloy 82/182 dissimilar metal welds greater than NPS 1 in the 4th Interval ISI Plan for CCNPP (e.g., are they included in the RI-ISI program, how many are selected for examination, what examination method(s) are being employed, what is the frequency of examination, disposition of limited coverage (<90%) examinations, etc.).

CCNPP Response:

All Category B-F or B-J Alloy 82/182 dissimilar metal welds greater than NPS 1 included in CCNPP Section XI program were included in CCNPP ASME Code Case N-578 Risk Informed-Inservice Inspection (RI-ISI) program for the current interval, and are also included in the proposed CCNPP ASME Code Case N-716 risk-informed/safety-based inservice inspection (RIS_B) program for the fourth interval. The total population of these welds is 27 for each CCNPP unit. Per the criteria of Code Case N-716, seven of these welds (per unit) were determined to be susceptible to primary water stress corrosion cracking (PWSCC), and six of these welds (per unit) were selected for examination under the RIS_B program.

Per Code Case N-716 (Table 1, Item No. 1.15, Elements Subject to Primary Water Stress Corrosion Cracking (PWSCC)), selected butt welds are subject to volumetric examination. Per Note 3 of this Table, the exam includes essentially 100% of the examination location. When the required examination volume or area cannot be examined due to interference by another component or part geometry, limited examinations shall be evaluated for acceptability. Areas with acceptable limited examinations (coverage less than 90%), and their bases, shall be documented and submitted for relief per the requirements of 10 CFR 50.55a.

A plant augmented inspection program has been implemented at CCNPP to meet all the requirements of Materials Reliability Program (MRP)-139, Revision 1, for all butt welds greater than NPS 1. Materials Reliability Program-139, Revision 1, provides requirements for the inspection and management of PWSCC-susceptible welds that are in addition to the requirements of Code Case N-716. Additionally, 1

ATTACHMENT (1)

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION ON RELIEF REQUEST ISI-04-04 MRP-139, Revision 1, specifies requirements for welds with limited examinations (coverage less than 90%) such as the consideration of augmented non-destructive examination methods with technical bases, performing a degradation assessment for any volume that remains unexamined due to the limitation and to consider mitigation. Further, per MRP-139, Revision 1, some welds may be required to be examined multiple times during the interval in addition to the examination required by Code Case N-716. The RIS_B program has not and will not be used to eliminate any required MRP-139 examinations or requirements.

NRC RAI 3:

On page 10, the licensee provides guidance in Section 3.3.2 Program Relief Requests. For program relief requests, the licensee refers to the process outlined in Title 10 of the Code of Federal Regulations 50.55a that will be used. Please discuss how the effect on risk of the incomplete examination coverage will be assessed.

CCNPP Response:

Per footnote 3 of Table 1 of Code Case N-716, when the required examination volume or area cannot be examined due to interference by another component or part geometry, limited examinations shall be evaluated for acceptability. Acceptance of limited examinations or volumes shall not invalidate the results of the change-in-risk evaluation (paragraph 5 of Code Case N-716). The change in risk evaluation of Code Case N-716 is consistent with previous risk-informed ISI applications (e.g., EPRI TR-112657) and meets Regulatory Guide 1.174 change in risk acceptance criteria. Areas with acceptable limited examinations, and their bases, shall be documented.

Consistent with previously approved RI-ISI submittals [e.g., Waterford 3 Safety Evaluation (Reference 1)], Constellation will continue to calculate coverage and use additional examinations and techniques in the same manner it has for traditional Section XI examinations. Experience has shown this process to be weld-specific (e.g., joint configuration). As such the effect on risk, if any, will not be known until that time. Relief requests, if needed, will be submitted per the guidance of 10 CFR 50.55a(g)(5)(iv).

REFERENCE

1. Letter from Mr. T. G. Hiltz (NRC) to Vice President, Operations (Entergy Operations) dated April 28, 2008, Waterford Steam Electric Station, Unit 3 - Request for Alternative W3-ISI-005, Request to use ASME Code Case N-716 2