NRC-11-0048, Response to Request for Additional Information Regarding Relief Request RR-A39 for Use of the BWRVIP Guidelines in Lieu of Specific ASME Code Requirements
| ML112991389 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 10/26/2011 |
| From: | Plona J Detroit Edison, DTE Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NRC-11-0048, TAC ME6765 | |
| Download: ML112991389 (13) | |
Text
Joseph H. Plona Site Vice President (400 N. Dixie Highway, Newport, MI 48166 Tel: 734.586.5910 Fax: 734.586.4172 10 CFR 50.55a October 26, 2011 NRC-11-0048 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington D C 20555-0001
References:
- 1) Fermi 2 NRC Docket No. 50-341 NRC License No. NPF-43
- 2) Detroit Edison's Letter to NRC, "Request for Relief- Use of the Boiling Water Reactor Vessel and Internals Project (BWRVIP)
Guidelines in Lieu of Specific ASME Code Requirements,"
NRC-11-0039, dated July 28, 2011
[ADAMS Accession No. ML112101480, TAC No. ME6765]
Subject:
Response to Request for Additional Information Regarding Relief Request RR-A39 for Use of the BWRVIP Guidelines in Lieu of Specific ASME Code Requirements In Reference 2, Detroit Edison submitted a proposed relief request (RR-A39) to use the Boiling Water Reactor Vessel Internals Project (BWRVIP) Guidelines in Lieu of ASME Code Requirements for in-service inspection of the reactor vessel internal components at Fermi 2.
In an e-mail from Mr. Mahesh Chawla to Mr. Alan Hassoun dated September 12, 2011, the NRC requested additional information for Relief Request RR-A39. This was discussed in a telephone conversation between NRC staff and Detroit Edison personnel on September 22, 2011. The additional information requested by the NRC staff is enclosed.
There are no new commitments included in this document.
USNRC NRC-11-0048 Page 2 Should you have any questions or require additional information, please contact Mr.
Rodney W. Johnson of my staff at (734) 586-5076.
Sincerely, Enclosure cc: NRC Project Manager NRC Resident Office Reactor Projects Chief, Branch 4, Region III Regional Administrator, Region III Supervisor, Electric Operators, Michigan Public Service Commission
Enclosure to NRC-11-0048 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Response to Request for Additional Information Regarding Relief Request RR-A39 for Use of the BWRVIP Guidelines in Lieu of Specific ASME Code Requirements
Enclosure to NRC-11-0048 Page 1 The following is Detroit Edison's response to each NRC request for additional information (RAI) for Relief Request RR-A39 (Use of Boiling Water Reactor Vessel Internals Project (BWRVIP)
Guidelines in Lieu of ASME Code Requirements):
RAI #1.
In a letter dated October 1, 2003, Entergy Nuclear Operations Inc. (Entergy), the licensee of Vermont Yankee Nuclear Power Station (VYNPS), submitted a similar relief request in which the licensee proposed to implement the BWRVIP guidelines in lieu of ASME Section XI requirements for the VYNPS's RVI components. In a supplemental letter dated January 22, 2004, (ADAMS-Accession Number ML040690734), Entergy submitted details of the inspections for the RVI components that are consistent with the BWRVIP inspection guidelines. The staff, in its safety evaluation (SE) dated September 19, 2005, approved VYNPS's relief request.
The staff requests that the licensee provide inspection requirements and inspection frequencies applicable for the third ISI interval for Fermi, Unit 2 similar to those addressed in VYNPS's supplemental letter (ADAMS-Accession Number ML040690734).
Response
Table 1 in Enclosure 1 to Reference 2 provides a comparison of the ASME Code Category Item Number, Scope, Examination requirements, and frequency to the associated BWRVIP requirements that are currently implemented at Fermi 2. Enclosure 2 to Reference 2 provides detailed examples of such comparison. The history of Reactor Vessel Internal Component inspections is also provided in Enclosure 3 to Reference 2. As discussed in the teleconference with NRC staff on September 22, 2011, the information provided in Reference 2 was based on similar relief request submittals that have been approved by NRC and is sufficient to address this RAI.
RAI #2.
The staff requests that the licensee make a commitment that it will implement the requirements specified in the BWRVIP-94 report, Program Implementation Guidelines, for Fermi, Unit 2. Specifically, the BWRVIP-94 report states that where guidance in existing BWRVIP documents has been supplemented or revised by subsequent correspondence approved by the BWRVIP Executive Committee, the most current approved guidance will be implemented. A similar commitment was made by Entergy for VYNPS in its relief request dated October 1, 2003 (ADAMS-Accession Number ML032810440).
Enclosure to NRC-11-0048 Page 2
Response
In 1997, the BWRVIP submitted letter numbers97-461 and 97-870 to NRC regarding BWR Utility Commitments to the BWRVIP. These letters describe United States Boiling Water Reactors commitment to follow BWRVIP guidelines for Reactor Vessel Internals (RVI) inspections. Based on the commitment described in these letters, the RVI inspection program at Fermi 2 has been developed and implemented to satisfy the requirements of BWRVIP-94.
The following paragraph describes Detroit Edison's implementation program of BWRVIP guidelines at Fermi 2:
It is recognized that the BWRVIP executive committee periodically revises the BWRVIP guidelines to include enhancements in inspection techniques and flaw evaluation methodologies. Where the revised version of a BWRVIP inspection guideline continues to also meet the requirements of the version of the BWRVIP inspection guideline that forms the safety basis for the NRC-authorized proposed alternative to the requirements of 10 CFR 50.55a, it may be implemented. Otherwise, the revised guidelines will only be implemented after NRC approval of the revised BWRVIP guidelines or a plant-specific request for relief has been approved.
RAI #3.
The staff requests that the licensee identify whether there are any furnace-sensitized stainless steel vessel attachment welds associated with the RVI components in Fermi, Unit 2. It is requested that the licensee provide an explanation regarding the type of inspection program and any additional augmented inspection program that are implemented for any existing furnace-sensitized stainless steel attachment welds in Fermi, Unit 2
Response
There are furnace-sensitized stainless steel vessel attachment welds associated with the RVI components at Fermi 2. The Guide Rod Brackets, Steam Dryer Support Lugs, Core Spray Piping Brackets, Feedwater Brackets, Surveillance Brackets, and Jet Pump Brackets were fabricated from SA-351-CF8M, with the welds material and inlay material being INCO-182.
The Shroud Support Gusset material is SB-168 with INCO-182 inlay weld metal.
The inspection strategy for Internal Attachments is found in Section 3 of BWRVIP-48-A.
Inspection requirements for the Internal Attachments are provided separately for those attachments that are considered to be safety-related. Those safety-related locations are the Core Spray Piping Brackets in BWRVIP-18-A, the Jet Pump Riser Braces in BWRVIP-41, and the Shroud Support Welds in BWRVIP-38. In addition, guidelines are provided in BWRVIP-48-A for other non safety-related bracket attachment welds which utilized weld material that are also susceptible to Intergrannular Stress Corrosion Cracking (IGSCC), such as Alloy 182, E308/309 or E308L/309L. No indications of cracking have been identified in any of the previous inspections performed, and there are no additional augmented inspections to be performed on interior attachment welds beyond those specified above.
Enclosure to NRC-11-0048 Page 3 It is recognized that there are also ASME Section XI inspection requirements for internal attachments within (VT-1) and beyond the beltline (VT-3) region of the vessel to be performed at least once each interval. However, in most cases an EVT-1 examination is required by the BWRVIP guideline which exceeds ASME Section XI requirements. The only reduction in inspections would be in the inspection frequency for the Jet Pump Riser Brace Welds and Shroud Support Gussets where a sampling program is utilized. (25% every 6 yrs for Jet Pump Riser Braces and at least 8 shroud support gussets every 6 years per BWRVIP-41 and BWRVIP-38 guidelines respectively).
RAI #4.
The staff requests that the licensee include the following BWRVIP reports in Section 5.0 of the submittal dated July 28, 2011.
BWRVIP-138,"BWRVIP Updated Jet Pump Beam Inspection and Flaw Evaluation".
BWRVIP-139, "BWR Vessel Internals Project, Steam Dryer Inspection and Flaw Evaluation Guidelines."
BWRVIP-183, "BWR Vessel Internals Project, Top Guide Grid Beam Inspection and Flaw Evaluation Guidelines."
Response
As discussed during the conference call between Detroit Edison representatives and the NRC staff on September 22, 2011, these three documents were not included in the original submittal for the following reasons:
- BWRVIP-138 provides requirements for inspection of Jet Pump Beams and was not included because there are no specific visual inspection requirements for the beams, since the beams are not Code components. Additionally, the inspection requirements for beams are included in the BWRVIP-41 report.
- BWRVIP-139 for the Steam Dryer was not included because the Steam Dryer is a non-safety-related / non Code component and is not subject to ASME Section XI requirements.
- BWRVIP-183 for the Top Guide Grid Beams was submitted by the BWRVIP to the NRC for review and approval. This report was not included because it has not yet been approved by NRC.
It should be noted that the inspections required by these three guideline reports were incorporated and are being implemented at Fermi 2 as part of the RVI Inspection Program.
Enclosure to NRC-11-0048 Page 4 With respect to the top guide grid beams, Detroit Edison has implemented inspections consistent with the guidance in BWRVIP-183 at Fermi 2, and as such is performing inspections of 10 percent of the top guide grid beams every 12 years with at least 5 percent to be inspected within the first 6 year inspection period which ends with the sixteenth refueling outage (RF16) scheduled in the Fall of year 2013. The visual inspection method utilized is the enhanced visual examination (EVT-1) method. As detailed in Enclosure 3 to Reference 2, no cracking has been detected as a result of the inspections to date. Should a future ultrasonic examination (UT) qualified technique be developed and demonstrated, it may be utilized in lieu of the EVT-1 method.
RAI #5.
The staff requests that the licensee confirm whether NUREG-0619, "BWR Feedwater Nozzle and Control Rod Drive Return Line Nozzle Cracking" will be used for the inspection of feedwater sparger tee welds and feedwater sparger piping brackets. If not, provide alternative methods for inspecting these components.
Response
There are no specific BWRVIP inspection guidelines for these components; however, Detroit Edison has and continues to implement the inspections on the Feedwater Nozzle and Control Rod Drive Return Line Nozzle at Fermi 2 as required by NUREG-0619 and has also implemented the Alternate BWR Feedwater Nozzle Inspection Program per GE-NE-523-A71-0594-A, Revision 1. Ultrasonic inspections of the Control Rod Drive Return Line Nozzle, Feedwater Nozzle and Nozzle inner-radius sections are performed at the established frequency. Visual inspections of the Feedwater Nozzles, spargers, and end brackets and pins are also performed. Ultrasonic inspections are currently performed per ASME Section XI and PDI requirements.
A VT-3 inspection of the sparger and sparger holes is performed at least once every fourth (4 th) refueling outage. The inspection verifies that degradation of the nozzle has not occurred and that the sparger nozzle holes, end brackets and pins are not worn, and that welds in the sparger arms and tees are not cracked. The spargers are not considered safety-related in BWRVIP-06, and no ASME Section XI inspections are required other than the ASME Code VT-3 inspections of the bracket attachment welds.
RAI #6.
In Table 1 of Enclosure 1 of the submittal dated July 28, 2011, the licensee did not provide inspection criteria for the shroud support leg weld (H12) which requires inspection per the requirements specified in the staffs SE for the BWRVIP-38 report, "BWR Vessel Internal Project, BWR Shroud Support Inspection and Flaw Evaluation Guidelines". However, the
Enclosure to NRC-11-0048 Page 5 staffs final SE for the BWRVIP-38 report (ML #003735498) indicates that when inspection tooling and methodologies are developed that allow the welds in the lower plenum to be accessible, the guidelines will state that the licensee will inspect these welds with the appropriate NDE methods in order to establish a baseline for these welds. Consistent with these requirements, the staff, therefore, requests that the licensee revise Table 1 of Enclosure 1 of the submittal dated July 28, 2011, to include a commitment that the shroud support leg weld H12 will be inspected when the inspection tooling and methodologies permit such an inspection.
Response
The Fermi 2 reactor vessel does not have the shroud support leg weld (H12) configuration; however, the Fermi 2 reactor vessel has 22 gussets that help support the shroud from the top of the shroud support plate. A portion of the H8 and H9 gusset welds are inspected every 6 years along with a sampling of the shroud support gusset welds in accordance with the requirements of BWRVIP-38.
RAI #7.
The staff requests that the licensee shall include a reference to BWRVIP-25, "BWR Core Plate Inspection and Flaw Evaluation Guidelines," in the row designated as ASME item B 13.10 in Table 1 of Enclosure 1 of the submittal dated July 28, 2011.
Response
The Core plate, while an ASME Code component, is not normally accessible for inspection without the removal of fuel and other vessel components. While some general VT-3 examinations have been performed in this area, the BWRVIP-25 required inspection on Core Plate Bolts is not currently performed. A Deviation Disposition has been filed for these components and a notification letter has been submitted to NRC (see Reference No. 11 in Detroit Edison's July 28, 2011 submittal). This is similar to the position of other BWRs of the same design that does not include core plate wedges.
Detroit Edison concurs with the inclusion of a reference to BWRVIP-25 under ASME Item No. B 13.10 in Table 1 of Enclosure 1 to Reference 2. A revised Table 1 is included at the end of this Enclosure.
Additional details on the core plate are provided in the response to RAI #8 below.
Enclosure to NRC-11-0048 Page 6 RAI #8.
On pages 11 and 12 of Enclosure 3 of the submittal dated July 28, 2011, the licensee stated that per the BWRVIP analyses performed in 2003 and 2006, no inspections were performed on core plate rim bolts since refueling outage (RF08). With regard to this issue, the staff requests that the licensee provide a brief summary of the justification that was used for not performing the inspections and explain how the deviation was dispositioned for these bolts as required by BWRVIP Letter 2010-243.
Response
NEI 03-08, Guideline for the Management of Material Issues, and BWRVIP-94, Revision 1, required the preparation of a Deviation Disposition for any deviation from the BWRVIP guidance. Detroit Edison prepared a Deviation Disposition for the Core Plate Bolting for Fermi 2 (available on BWRVIP website) similar to other BWRs. A notification letter was also submitted to NRC (see Reference No. 11 in Detroit Edison's July 28, 2011 submittal).
BWRVIP guidance requires that 50 percent of the core plate rim hold-down bolts of BWR 2-5 plants without core plate wedges be examined by enhanced visual inspection (EVT-1) from below the core plate or by ultrasonic testing (UT) from above the core plate once the technique has been developed. However, it was later determined by the BWRVIP that the bolts cannot be ultrasonically inspected, due to configuration issues, resulting from the welded keeper plate.
Additionally, it was concluded by the BWRVIP that meaningful EVT-1 examinations cannot be performed. Accordingly, a Deviation Disposition for deviation from the BWRVIP guidance was developed as required by BWRVIP-94, Revision 1 and NEI 03-08, Guideline for the Management of Material Issues.
The Deviation Disposition includes an analysis that concluded that the bolting has a relatively low susceptibility to cracking and a very high flaw tolerance. The postulated flaws would not grow to a size that significantly reduces the bolt preload over the life of the plant. Even if significant cracking did occur in the bolting, redundant structural components will prevent adverse displacement of the core plate. Furthermore, even with the extremely conservative assumptions of failures of both the bolting and the redundant hardware, the Standby Liquid Control system could be used to bring the reactor to a safe shutdown.
It should be recognized that the BWRVIP is currently working on developing revised guidance for the Core Plate bolt inspection, and plans to submit the revised guidance for NRC review and approval. The BWRVIP schedule calls for providing approved revised guidance by December 31, 2015.
Enclosure to NRC-11-0048 Page 7 RAI #9.
According to Section 2.0 of BWRVIP-76, "BWR Core Shroud Inspection and Flaw Evaluation Guidelines," core shroud welds shall be inspected every 6 years when the enhanced visual test (EVT-1) method is used for one-sided weld inspections, and shall be inspected every 10 years when the subject welds are examined with the ultrasonic test (UT) method. The inspection frequency for the core shroud welds (H1 through H7) as indicated in Table 1 of Enclosure 1 of the submittal dated July 28, 2011, is not consistent with the aforementioned requirement. Therefore, the staff requests that the licensee revise the inspection frequency requirement for the subject welds in Table 1 of Enclosure 1 of the July 28, 2011 submittal. Inspection criteria for H8 and H9 welds should be specified in Table 1 of Enclosure 1 of the submittal dated July 28, 2011.
Response
The inspection frequency for the core shroud welds (H1 through H7) as indicated in Table 1 of Enclosure 1 to Reference 2, is consistent with the BWRVIP-76 requirements. There have been numerous BWRVIP letters regarding this subject. Fermi 2 is a Category B plant as defined in BWRVIP-76, and has performed ultrasonic inspections of the required Core Shroud welds in 1998 and again in 2007. The inspections performed in 1998 were from both sides of the H4 weld and one side of the H3, H5, and H7 welds. The inspections performed in 2007 were performed from both sides of these four welds consistent with the latest version of BWRVIP-76. While no evidence of cracking was identified during any of these inspections, a plant specific analysis is required by BWRVIP-76 due to the fluence exceeding the specified threshold in BWRVIP-76. Detroit Edison plans to perform this plant specific analysis to justify re-inspection of the Core Shroud welds during the refueling outage in 2016. This inspection is currently targeted for 2013.
Inspection criteria for the shroud support including gusset welds are included in Table 1 of Enclosure 1 to Reference 2 under ASME item B13.40; however, the H8 and H9 designations were not. Detroit Edison concurs with the inclusion of the H8 and H9 welds in the Table. A revised Table 1 is included at the end of this Enclosure. Additional details regarding these components were provided in Enclosure 2 to Reference 2. The examinations required per BWRVIP-38 include the shroud support welds and gussets. Detroit Edison has performed the required inspections of a percentage of the H8 and H9 welds at Fermi 2, along with a sampling of the Shroud Support Gussets every 6 years.
RAI #10.
Identify the welds that were made with Alloy182 weld electrode in Fermi, Unit 2 RVI components. Since Alloy 182 welds are prone to intergranular stress corrosion cracking, the licensee is requested to provide the history of inspections and the results of these inspections of these welds, and subsequent examination criteria if cracking was found in these welds.
Enclosure to NRC-11-0048 Page 8
Response
Enclosure 3 to Reference 2 provides the inspection history for all internal components and welds of the Fermi 2 RVI. As discussed during the conference call between Detroit Edison and NRC on 9/22/2011, a large number of welds on the internal components are made with Alloyl82 weld electrodes. While most of the internal components are fabricated from stainless steel, many welds are made with a combination of Alloy 82 or 182, depending on the location in the vessel.
As discussed in the response to RAI #3 above, the integral attachments are welded with Alloy 182 along with selected welds on the Jet Pump Diffuser/Adapter, Access Hole Covers (AHC), and H7 Shroud Weld. While these welds may be slightly more prone to intergranular stress corrosion cracking, the bulk of the visual inspections were performed following each applicable BWRVIP guideline with an EVT-1 technique capable of detecting Intergrannular Stress Corrosion Cracking (IGSCC). Additionally, Ultrasonic inspections were performed on the H7 Shroud weld and the Jet Pump Diffuser/Adapter welds. No separate distinction is made in any BWRVIP inspection guideline requiring additional inspections or frequency changes based on the weld material and no additional augmented inspections are performed.
The only identified indication of cracking associated with Alloy 182 welds is the cracking identified on the zero degree AHC. The indications were first identified in RF12 (Fall 2007), and were subsequently reexamined in RF13 (Spring 2009) and RF14 (Fall 2010).
This condition appears to be stable, since no changes in crack appearance were detected in the subsequent inspections. The next scheduled inspection for the AHC is during RF16 (Fall 2013) following ASME Section XI re-inspection guidance. Pending NRC approval of this relief request (RR-A39), re-inspections could be modified and the frequency extended based on the existing flaw analysis.
Enclosure to NRC-11-0048 Page 9 TABLE 1 Comparison of ASME Examination Category B-N-1 and B-N-2 Requirements With BWRVIP Guidance Requirements (')
ASME Item ASME Exam ASME Applicable Applicable BWRVIP Exam BWRVIP No. Table Component Scope ASME Exam Frequency BWRVIP S cope BWRVIP Frequency IWB-2500-1 ___Document B13.10 Reactor Vessel Interior Accessible Areas VT-3 Each period BWRVIP-18, 25 Overview examinations of components during BWRVIP (Non-specific) 26, 38, 41, 47, examinations are performed to satisfy Code VT-3 inspection 48, 76 requirements.
B13.20 Interior Attachments Within Accessible Welds VT-1 Each 10-year BWRVIP-48 Riser Brace EVT-1 100% in first 12 Beltline - Riser Braces Interval Table 3-2 Attachment years, 25% during each subsequent 6 years Lower Surveillance Specimen BWRVIP-48, Bracket VT-1 Each 10-year Interval Holder Brackets Table 3-2 Attachment B13.30 Interior Attachments Beyond Accessible Welds VT-3 Each 10-year BWRVIP-48 Bracket VT-3 Each 10-year Interval Beltline - Steam Dryer Hold- Interval Table 3-2 Attachment down Brackets Guide Rod Brackets BWRVIP-48, Bracket VT-3 Each 10-year Interval Table 3-2 Attachment Steam Dryer Support BWRVIP-48, Bracket EVT-1 Each 10-year Interval Brackets Table 3-2 Attachment Feedwater Sparger Brackets BWRVIP-48, Bracket EVT-1 Each 10-year Interval Table 3-2 Attachment Core Spray Piping Brackets BWRVIP-48, Bracket EVT-1 Every 4 Refueling Table 3-2 Attachment Cycles Upper Surveillance Specimen BWRVIP-48, Bracket VT-3 Each 10-year Interval Holder Brackets Table 3-2 Attachment Shroud Support (Weld H9) BWRVIP-38, Weld H9 EVT-1 or UT Maximum of 6 years including gussets 3.1.3.2, Including for EVT-1, Maximum Figures 3-2 and gussets of 10 years for UT 3-5
Enclosure to NRC-11-0048 Page 10 ASME ASME Item ASME Exam ASME Applicable Applicable BWRVIP Exam .. ...
BWRVIP No. Table Component Scope ASME Exam F BWRVIP cope BWRVIP Frequency IWB-2500-1 Document .
B13.40 Integrally Welded Core Accessible VT-3 Each 10- BWRVIP-38, Shroud Support EVT-1 or UT Based on as-found Support Structure Surfaces year Interval 3.1.3.2, welds H8 and conditions, to a Figures 3-2, 3-5 H9 maximum 6 years for including one side EVT-1, 10 gussets years for UT where accessible Shroud Horizontal welds BWRVIP-76, Welds H1- H7 UT or EVT-1 Based on as-found 2.2 as applicable conditions, to a maximum of 10 years for UT when inspected from both sides of the welds Shroud Vertical welds BWRVIP-76, Vertical Welds EVT-1 or UT Maximum 10 years 2.3 as applicable for UT based on inspection of horizontal welds NOTE:
- 1) This Table provides only an overview of the requirements. For more details, refer to ASME Section XI, Table IWB-2500-1, and the appropriate BWRVIP document.