ML20248L739
| ML20248L739 | |
| Person / Time | |
|---|---|
| Issue date: | 06/08/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20248L735 | List: |
| References | |
| NUDOCS 9806110330 | |
| Download: ML20248L739 (10) | |
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U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION DIVISION OF ENGINEERING SAFETY EVALUATION OF EPRI TOPICAL REPORT TR-105696 "BWR VESSEL AND INTERNALS PROJECT. REACTOR PRESSURE VESSEL AND INTERNALS EXAMINATION GUIDELINES (BWRVIP-03)"
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! INTRODUCTION 1.1 Backgrour.d By letters dated April 21,1995, and November 22,1994, (References 1 and 2) the Boiling Water Reactor Vessel and intemals Project (BWRVIP) submitted the reports, "BWR Core Shroud Inspection and Evaluation Guidelines, Revision 1," and the "BWRVIP Core Shroud NDE Uncertainty and Procedure Standard," respectively, for staff review. The NRC staff, with technical assistance from Brookhaven National Laboratory (BNL), assessed these reports in its safety evaluation (SE), dated June 16,1995 (Reference 3). The BWRVIP then submitted the EPRI proprietary report, "BWR Vessel and Intemals Project, Reactor Pressure Vessel and Intemals Examinations Guidelines (BWRVlP-03)," by letter dated November 10,1995 (Reference 4). The BWRVIP-03 report supersedes Reference 2 and references Reference 1. It contains sections not in the original document, including Section 5, " Shroud Support," and Section 6A, " Standards for Visual Inspection of Core Spray Piping, Spargers, and Associated Components."
The BWRVIP-03 report is structured to eventually address the examination of all components under the charter of the BWRVIP. The BWRVIP plans to update the BWRVIP-03 report twice a year to incorporate the results of ongoing NDE demonstrations and the inspection of the remaining internal components. The BWRVIP intended, in submitting the BWRVIP-03 report, to provide proven, documented NDE techniques and inspection standards to effectively examine j
susceptible BWR internal components to ensure their structural integrity.
1.2 Purpose The staff reviewed the BWRVIP-03 report to determine whether its guidance would provide adequate NDE techniques and inspection standards to effectively examine susceptible BWR internal components to ensure their structural integrity.
1 1.3 Organization of this Report The BWRVIP-03 report is proprietary, therefore, this SE is written so as not to repeat information contained in the report. The staff does not discuss in any detail the provisions of the guidelines I
j nor the parts of the guidelines it finds acceptable.
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9006110330 90060s PDR TOPRP EXIEPRI C
1 This SE contains a brief summary of the general contents of the report in Section 2.0 and the detailed evaluation in Section 3.0. In Section 3.0 the staff evaluates relevant parts of the BWRVIP-03 report and associated documentation to determine if items documented in the staff's June 16,1995, SE have been satisfactorily addressed. It then compares the 3WRVIP-03 report to Referer.ces 1 and 2. The staff's aim was to determine whether new material had been added that had r,ot been previously evaluated or differed from the information upon which the June 16,1995, SE was based. Finally, the staff evaluated the adequacy of the guidance contained in th, new sections to the BWRVIP-03 report. The staff's conclusions and issues that the staff requests the BWRVIP resolve are summarized in Secticn 4.0.
2.0
SUMMARY
OF TOPICAL REPORT This report includes guidelines for using BWRVIP mockups, protocol for demonstrating nondestructive examination (NDE) techniques on mockups, and guidelines for determining uncertainties in NDE technique and inspection tool positioning.
For components addressed to date, this report contains (1) data on fabricating mockups, (2)
NDE uncertainty measurements and evaluation factors, and (3) procedure standards for ultrasonic (UT), eddy current (ET), and visual examinations (VT).
The BWRVIP-03 report addresses the topics below in the following order; o
General Procedures: Demonstration of inspection tooling and NDE techniques on realistic mockups; guidance to provide objective, uniform demonstrations, Components Specific Information: Outline of the organization of new information to be o
submitted as it is developed.
Shroud Inspections: Applicable mockups; demonstrations for UT, VT, and ET o
techniques; standards for UT, VT and ET examinations of shroud welds.
o Shroud Supports: Inspections, demonstrations, mockups.
o Core Spray Piping, Spargers, and Associated Components: Standards for visual inspection.
3.0 STAFF EVALUATION 3.1 Evaluation of the BWRVIP-03 report and associated documentation to determine if staff concerns documented in the SE dated June 16,1995, have been satisfactorily addressed.
The nine items that were the subject of the June 16,1995, SE are provided in the attachment to this SE. The BWRVIP, in its letters of May 17, and June 6,1996, (References 5 and 7) addressed these items. The items, responses, and the staffs disposition, are given below:
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!tems 1. 3 concerned the need for guidance for reinspecting core shrouds and for the timely submittal of the guidance for staff review. These items were addressed by the Electric Power Research Institute (EPRI) Topical Report TR-105747, "BWR Vessel and Intemals Project, Guidelines for Reinspection of BWR Core Shrouds (BWRVIP-07)." The report was submitted by letter dated February 2,1996, (Reference 6), and subsequently clarified by letters to the staff dated May 17, July 17, and October 21,1996, and January 8,1997, (References 7, 8, 9, and 10, respectively). The staff issued its SE of this document on September 15,1997, (Reference 11). The SE found the guidance generally acceptable but identified several open items, which the BWRVIP addressed in its November 26,1997, response to the staff's SE. The staffis currently revising it BWRVIP-07 SE based on this additional information. Based on the actions taken to address this issue in BWRVIP-07, this item is adequately addressed.
Item 2 concemed expediting the qualification of the inspection methods using mockups of H-7 welds with and without backing rings. The BWRVIP responded that demonstrations were performed. The staff reviewed the details contained in Section 5 of the BWRVIP-03 report and concluded that inspections of the subject configuration have been adequately qualified. This item is adequately addressed, item 4 specified that licensees provide justification and guidelines when taking credit for fillet welds in shroud designs in limit load or linear elastic fracture mechanics 1
evaluations of BWR core shrouds. It aiso specified the content of the justification j
and guidelines. The BWRVIP agreed that credit for core shroud fillet welds would not be taken until furtherjustification and guidelines are provided to the NRC staff. This response adequately addresses this item.
Item 5 concemed the procedures to evaluate a given delivery system or NDE technique for use. The staff, in item 5, specified establishing udditional guidelines to clarify actions and steps necessary in order to qualify NDE inspection technologies.
The BWRVIP responded that it evaluated NDE techniques by performing or witnessing demonstrations of the techniques on full-size mockups of the affected components. The purpose of the demonstrations was to measure the uncertainty of defect sizing that results from inaccuracies inherent in the NDE techniques and equipment. To standardize the approach for determining NDE uncertainty, the BWRVIP wrote Sections 2.3 and 2.4 of the BWRVIP-03 report. The staff finds the BWRVIP activities adequately addressed this item, item 6 concemed expediting the completion and evaluation of full size mockups for assessing the performance of NDE techniques for core shroud evaluations. The BWRVIP responded that two mockups of ring segment welds have been fabricated (BWRVIP-G and BWRVIP-H) and were being evaluated by NDE. A report for these evaluations was planned for summer of 1996, in the next scheduled update of the BWRVIP-03 report. Since the evaluated BWRVIP-03 report is dated October 1995, and provides no information about these two mocxups, this item will be addressed in a subsequent revision to this SE.
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1 Item 7 concerned resolving the lack of confidence in UT measurements on the far side of a weld in a timely manner. The BWRVIP stated that it evaluated the capability of several UT probes for detecting and sizing flaws on the far side of the weld and summarized the results. It addressed the limitations of any demonstrated UT method in the descriptions of demonstrations in the BWRVIP-03 report. The staff finds the BWRVIP activities adequately addressed this item and the referenced sections of the report acceptable.
Item 8 concerned the qualification of ET as an acceptable method for examining core shrouds. The staff, in item 8, requested a schedule for ET qualification milestones. The BWRVIP incorporated the information about the ET technique into the BWRVIP-03 report as Section 4.6, supplemented with details of three vendors' demonstrations. The staff reviewed the subject information and finds that the BWRVIP activities adequately addressed this item.
I ltem 9 concerned the use of VT as the primary examination method for core shrouds.
The staff requested that the BWRVIP establish further criteria to account for VT sizir:g (measurement) uncertainties. Those criteria were to include the establishment of a minimurn accept 3ble VT adjustment value to be added to the VT determined flaw indications (flaw lengths). The BWRVIP responded that the VT adjustment value had been determined and documented in the BWRVIP-03 report as Section 4.5 and that this value should be determined using a demonstration oerformed according to Section 2.3. The staff finds the BWRVIP activities aidequately addressed this item and the referenced sections of the report acceptable.
3.2 Evaluation of the BWRVIP-03 report with respect to new material and differences from original documents-The staff compared the BWRVIP-03 report to the original documents in References 1 and 2. Its aim was to determine whether new material had been added that had not been previously evaluated or differed from the information upon which the staff's June 16,1995, SE was based.
1 The staff issued a request for information dated March 12,1997, (Reference 12), to which the BWRVIP responded in its letter of June 30,1997, (Reference 13). Having evaluated the l
BWRVIP's response, the staff has identified several items that resulted from its review of Section 48, " Standards for Visual Examination of BWR Core Shroud Welds," that need resolution.
These are also cited under Section 3.3 of this SE since they also apply to Section 6A,
" Standards for Visual inspection of Core Spray Piping, Spargers, and Associated Components."
item 3.2-1 Paragraph 4.1 specifies that personnel evaluating inspection data be certified in the VT-1 method (as required by the American Society of Mechanical Engineers
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(ASME) Code,Section XI) only. The staff believes that this certification is not l-sufficient to show the competence of the personnel evaluating inspection data from enhanced visual testing (EVT-1) and the visualinspection of core spray I
components (CS-VT-1). EVT-1 and CS-VT-1 are more demanding examinations; i.e., they are performed underwater, in radiation environments, and require more specialized equipment. The personnel must also be able to resolve finer targets, 4
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%- to 1-mil, underwater, versus the 1/32-inch, in air, required by VT-1. Therefore, the staff concludes that the personnel need to be certified in (1) EVT-1 and (2)
CS-VT-1 also.
Item 3.2-2 Paragraph 4.3 addresses personnel training. The staff questioned the amount of facility specific training for performing the inspections recommended by the BWRVIP. The BWRVIP responded that it has no recommendation for site-specific training. This answer is inadequate. There needs to be some minimum amount of site-specific training required of even the most easily inspected plants since each plant is unique and has certain characteristics that could affect the validity of an inspection.
Item 3.2-3 Subsection 8 of Section 4B concems the documentation of results. The staff questioned whether the amount of training time in the use of equipment used for visual inspection and in aspects of inspection specific to a given site was specified and documented. The BWRVIP responded that training time and other details of personnel qualification and certification are not considered a necessary part of the documentation of an examination. This answeris inadequate for the following reasons:
Visual inspection is relied upon as a primary method of inspection of internals.
The qualification of personnel performing visualinspections is important as discussed in Open item 3.2-1.
To the staff's knowledge, this information would not be documented elsewhere.
Documentation of results is normally required as part of a safety-related component examination.
This information would be important for possible future evaluations.
3.3 Evaluation of Section 6A, " Standards for Visual inspection of Core Spray Piping, Spargers, and Associated Components."
The staff evaluated the safety adequacy of the guidance contained in the supplement to the BWRVIP-03 report, Section 6A, " Standards for Visual Inspection of Core Spray Piping, Spargers, and Associated Components." In its review, the staff issued a request for information dated March 12,1997, (Reference 12) to which the BWRVIP responded in its letter of June 30, L
1997, (Reference 13). Upon reviewing the responses the staff had identified several items that need further resolution:
Item 3.3-1 Paragraph 4.1 specifies the certification of personnel evaluating inspection data.
See discussion under item 3.2-1.
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Item 3.3-2 Paragraph 4.3 addresses personnel training. See discussion under item 3.2-2.
Item 3.3-3 Subsection 9 concems the documentation of results. See discussion under item 3.2-3.
Item 3.3-4 Upon cross-referencing the recommendations of Reference 14 to the BWRVIP-03 report, the staff finds that the scope of Section 6A is limited to EVT-1. The scope needs to cover standards for all the types of visual examinations specified in Reference 14. These include CS-VT-1, VT-1 and VT-3. (In contrast, the staff l
found no such limitation of scope in Section 48.)
ltem 3.3-5 Unlike Subsection 6 of Section 4B, Subsection 6 of Section 6A does not require that the effectiveness of cleaning be demonstrated. The effectiveness of surface cleaning needs to be demonstrated for all visual examinations, not just for those affecting the core shroud.
3.4 Evaluation of Section 5," Shroud Support" Concerning the guidance presented, this section appears to be incomplete. Mockups were made forjust 3 of the shroud support welds, demonstrations were applicable to only one of those welds, and those demonstrations were for UT only. Qualification of UT and VT inspection methods for specific shroud support weld configurations remain to be completed. This item will be addressed in the stafs review of BWRVIP-38, " Shroud Support and Flaw Evaluation Guidelines," dated September 15,1997.
4.0 CONCLUSION
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The staff has reviewed the BWRVIP-03 report and finds that the guidance of the BWRVIP-03 report is acceptable for inspection of the subject safety-related RPV internal components except where the stars conclusions differ from the proposed guidance, as discussed above. This finding is based on information submitted both originally and in response to the staff's RAI that clarified the guidance in the BWRVIP-03 report. The staff has concluded that licensee implementation of the guidelines in BWRVIP-03, with modifications to address the stafs.
conclusions above, will provide an acceptable level of quality for examination of the safety-related components addressed in the BWRVIP-03 document. The staff requests that the BWRVIP review and resolve the issues raised in the enclosed SE, and incorporate the stafs conclusions into a revised BWRVIP-03 report. Please inform the staff in writing as to this resolution. These items are tabulated below for clarity. Item 6 is from the stars SE of June 16, 1995, (Reference 3).
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4 Table 1: List of items item 6 Evaluation of mockups for ring segment welds item 3.2-1; Item 3.3-1 Certification of personnel evaluating inspection data item 3.2-2; Item 3 3-2 Site specific training for personnel item 3.2-3; Item 3.3-3 Documentation of training time for personnel item 3.3-4 Scope of standards for visual inspections item 3.3-5 Demonstration of effectiveness of cleaning
5.0 REFERENCES
1.
BWRVIP letter to NRC dated April 21,1995, submitting the "BWR Core Shroud inspection and Evaluation Guidelines. Revision 1."
2.
BWRVIP letter to NRC dated November 22,1994, submitting the "BWR-VIP Core Shroud NDE Uncertainty and Procedure Standard."
3.
NRC letter to the BWRVIP dated June 16,1995, providing safety evaluation titled,
" Evaluation of BWR Core Shroud Inspection and Evaluation Guidelines, GENE 523-113-0894, Revision 1, dated March 1995, and BWRVIP Core Shroud NDE Uncertainty and Procedure Standard, dated November 22,1994".
4.
BWRVIP-03, "BWR Vessel and Intemals Project, Reactor Pressure Vessel and Intemals Examinations Guidelines" (Transmitted to the NRC November 10,1995) 5.
BWRVIP letter to NRC dated June 6,1996, " Additional Response to NRC Staff Concems and Unresolved items."
6.
BWRVIP letter to NRC dated February 2,1996, " Electric Power Research Institute (EPRI) EPRI Topical Report TR-105747, BWR Vessel and Intemals Project, Guidelines for Reinspection of BWR Core Shrouds (BWRVIP-07)."
7.
BWRVIP letter to NRC dated May 17,1996, titled "BWRVIP Response to NRC Staff j
Concems and Unrosolved items."
8.
BWRVIP letter to NRC dated July 17,1996, titled " Clarifications to Core Shroud Reinspection Guidelines."
9.
BWRVIP letter to NRC dated October 21,1996, titled "BWRVIP Response to Request for t
Additional Information Regarding Proprietary Topical Report EPRI TR-105747."
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4 10.
BWRVIP letter to NRC dated January 8,1997 titled " Modification to BWRVIP Response to NRC Request for Additional Information on BWRVIP-07."
11.
NRC letter to the BWRVIP dated September 15,1997, providing the staff's Safety Evaluation of EPRI Topical Report TR-105747 "BWR Vessel and Intemals Project, Guidelines for Reinspection of BWR Core Shrouds (BWRVIP-07)."
12.
NRC letter to the BWRVIP dated March 12,1997, " Proprietary Request for Additional Information - Review of BWR Vessel and Intemals Project Reports, BWR Vessel and I
intemals ' Project, Reactor Pressure Vessel and Intemals Examination Guidelines."
13.
BWRVIP letter to NRC dated June 30,1997, titled "BWRVIP Response to NRC Request for Additional Information on BWRVIP-03."
14.
BWRVIP letter to NRC dated July 26,1996, transmitting "BWR Vessel and Intemals Project, BWR Core Spray intemals inspection and Flaw Evaluation Guidelines (BWRVIP-18)," EPRI Report TR-106740, July 1996.
Attachment:
List of Concems and Unresolved items
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6 LIST OF STAFF CONCERNS AND UNRESOLVED ITEMS IN THE STAFF'S SAFETY EVALUATION DATED JUNE 16.1995 ON REFERENCES 1 AND 2 Item 1.
In regard to the BWRVIP's " Guidance for Reinspection of Core Shrouds," the staff urges the BWRVIP to determine if this document can be submitted at an earlier date, in order to support upcoming reinspection.
Item 2.
Qualification of the inspection methods utilizing mockups of H-7 welds with and without backing rings needs to be expedited by the BWRVIP.
Item 3.
- The BWRVIP needs to develop inspection guidelines which address the inspection of core shroud welds that are considered to be criticalin terms of assuring the structuralintegrity of core shroud repair assemblies. These guidelines needs to be submitted for NRC review prior to the first reinspection of a repaired BWR core shroud.
Item 4.
In regard to performing limit load or linear elastic fracture mechanics evaluations of BWR core shrouds, the staff has not yet given credit for fillet welds in the shroud designs. Furtherjustification and guidelines must be provided should licensees seek credit for core shroud fillet welds. The content of the justification and guidelines needs to include supporting finite element modeling and needs to address the capabilities and limitations (e.g. threshold of detection) of the inspection method used for these fillet weld inspections. The justification and guidelines needs to also address flaw evaluation methods and criteria should cracking be detected in the fillet welds. Where appropriate qualified field or test data on shroud fillet weld crack growth rates is lacking, a bounding growth rate of 5 x 10 5 inches /hr needs to be assumed.
Item 5.
The Staff finds the NDE uncertainty values for inspection delivery systems that haven't been evaluated by the BWRVIP to be reasonable based upon the -
inspection experience to date and experience with IGSCC. It is unclear, however, from the submittal what procedures are available to evaluate or certify a given delivery system /NDE tschnique for use. Additional guidelines needs to be established to clarify what sort of' actions and steps are necessary in order to qualify NDE inspection technologies for use, item 6.
The staff agrees that full size mockups for assessing the performance of NDE techniques will enhance core shroud evaluations. The staff requests that a schedule for completion and evaluation of these mock-ups be provided.
Item 7.
The staff agrees that the UT sizing and detection methods employed by the BWRVIP appear to be conservative. The staff is in agreement that UT creeping wave detection and sizing capabilities are reasonably accurate down to 0.02 inch crack depths. However, the lack of confidence in the far side UT measurements needs to be evaluated in a timely manner.
Attachment 1
Item 8.
The staff has reviewed the ET standard of the "BWR-VIP Core Shroud NDE Uncertainty and Procedure Standard," and does not have any unresolved issues in regard to its content at this time. However at this time ET has not been qualified as an acceptablc method for performing examinations of core shrouds.
It appears that the schedule for qualification of ET techniques for intemals is covered by the scopes of BWRVIP inspection Milestones Numbers 2-8
[ Reference 7]. If not, the staff requests that a schedule be provided for ET qualification milestones. Should ET inspections be performed on core shrouds or other BWR internals in the field prior to qualification of the technique by the BWRVIP, the staff requests that the details of the technique, and appropriate field data and experience be included in future submittals to the staff.
Item 9.
The current BWRVIP position in regard to performing examinations of BWR core shrouds is that UT testing is the preferred method of inspection. Should VT be chosen as the primary examination method, the staff requests that the BWRVIP establish further criteria to account for VT sizing (measurement) uncertainties.
These criteria neeos to include establishment of a minimum acceptable VT adjustment value that needs to be added to the VT determined flaw indications (flaw lengths).
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