ML041830595
| ML041830595 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 07/01/2004 |
| From: | Alexion T NRC/NRR/DLPM/LPD4 |
| To: | Forbes J Entergy Operations |
| Alexion T W, NRR/DLPM, 415-1326 | |
| References | |
| TAC MC2431 | |
| Download: ML041830595 (12) | |
Text
July 1, 2004 Mr. Jeffrey S. Forbes Site Vice President Arkansas Nuclear One Entergy Operations, Inc.
1448 S. R. 333 Russellville, AR 72801
SUBJECT:
SUMMARY
OF CONFERENCE CALL WITH ENTERGY OPERATIONS, INC.,
REGARDING THE ONCE-THROUGH STEAM GENERATOR INSPECTION RESULTS DURING THE 1R18 2004 REFUELING OUTAGE AT ARKANSAS NUCLEAR ONE, UNIT 1 (TAC NO. MC2431)
Dear Mr. Forbes:
On May 3, 2004, the NRC staff participated in a conference call with Entergy Operations, Inc.,
(EOI) representatives regarding the ongoing once-through steam generator tube inspection activities at Arkansas Nuclear One, Unit 1. A summary of the call is provided as Enclosure 1.
On May 11, 2004, EOI provided a document summarizing much of the information discussed during the conference call, which is provided as Enclosure 2.
The NRC staff appreciates the resources made available to discuss the inspection activities.
This letter completes our review of the conference call.
Sincerely,
/RA/
Thomas W. Alexion, Project Manager, Section 1 Project Directorate IV Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-313
Enclosures:
As stated cc w/encls: See next page
July 1, 2004 Mr. Jeffrey F. Forbes Site Vice President Arkansas Nuclear One Entergy Operations, Inc.
1448 S. R. 333 Russellville, AR 72801
SUBJECT:
SUMMARY
OF CONFERENCE CALL WITH ENTERGY OPERATIONS, INC.,
REGARDING THE ONCE-THROUGH STEAM GENERATOR INSPECTION RESULTS DURING THE 1R18 2004 REFUELING OUTAGE AT ARKANSAS NUCLEAR ONE, UNIT 1 (TAC NO. MC2431)
Dear Mr. Forbes:
On May 3, 2004, the NRC staff participated in a conference call with Entergy Operations, Inc.,
(EOI) representatives regarding the ongoing once-through steam generator tube inspection activities at Arkansas Nuclear One, Unit 1. A summary of the call is provided as Enclosure 1.
On May 11, 2004, EOI provided a document summarizing much of the information discussed during the conference call, which is provided as Enclosure 2.
The NRC staff appreciates the resources made available to discuss the inspection activities.
This letter completes our review of the conference call.
Sincerely,
/RA/
Docket No. 50-313 Thomas W. Alexion, Project Manager, Section 1 Project Directorate IV
Enclosures:
As stated Division of Licensing Project Management Office of Nuclear Reactor Regulation cc w/encls: See next page DISTRIBUTION:
PUBLIC RidsNrrPMTAlexion PDIV-1 Reading RidsNrrLADBaxley RidsOgcRp RidsRgn4MailCenter (AHowell)
RidsAcrsAcnwMail Center JTerrell RidsNrrDlpmLpdiv1 (RGramm) MMurphy RidsNrrLADJohnson
- concurrence does not include Enclosure 2 Accession No.:ML041830595 *conference call summary input from EMCB OFFICE PDIV-1/PM PDIV-1/LA** EMCB/(A)SC PDIV-1/SC NAME TAlexion DBaxley PKlein RGramm DATE 7/1/04 6/30/04 06/23/04* 7/1/04 OFFICIAL RECORD COPY
SUMMARY
OF CONFERENCE CALL WITH ENTERGY OPERATIONS, INC.
ONCE-THROUGH STEAM GENERATOR INSPECTION RESULTS DURING THE 1R18 REFUELING OUTAGE ARKANSAS NUCLEAR ONE, UNIT 1 On May 3, 2004, the NRC staff participated in a conference call with Entergy Operations, Inc.
representatives (the licensee) regarding the on-going steam generator tube inspections at Arkansas Nuclear One, Unit 1 (ANO-1). The issues discussed during the call include those listed in a letter sent to ANO-1 on April 2, 2004 (ML040970514).
ANO-1 has two Babcock and Wilcox once-through steam generators (OTSGs). Each OTSG contains approximately 15,500 Alloy 600 tubes. The tubes are straight and supported by 15 carbon steel tube support plates. The tubes are roll expanded into both the lower (cold-leg) and upper (hot-leg) tubesheet.
On May 11, 2004, the licensee provided a document summarizing much of the information discussed during the conference call. This summary is provided as Enclosure 2. Additional information (including clarifying information) provided during the call is summarized below.
With respect to the scope of inspections discussed in response to Question 3 of the NRCs April 2, 2004, letter, the licensee indicated the following:
- The bobbin coil examination consisted of 100% of all unplugged tubes from the hot-leg tube-end to the cold-leg tube-end.
- The rotating probe examination consisted of the following:
- upper tubesheet roll transitions and the tube ends in 100% of the unplugged, non re-rolled tubes
- 100% of the re-rolled tubes in the upper and lower tubesheet regions
- 20% of the tubes in the sludge pile / dented regions
- 20% of the tube dents in the superheated region (tube area above the 8th/9th tube support plate region) in OTSG-A
- 100% of the tube dents in the superheated region in OTSG-B
- 100% of the sleeve roll transitions in the Inconel 600 sleeves
- 34% of the tube ends and roll transitions in the lower tubesheet
- approximately 2500 special interest areas, identified during bobbin coil examination With respect to the exceptions taken to the industry guidelines discussed in response to Question 4 of the NRCs April 2, 2004, letter, the licensee provided the following additional details:
- The rotating probe examinations performed at the lower tube ends and lower roll transition included approximately 5200 tubes in each OTSG. The OTSG was divided into a donut shape with a radius of 41 inches. Approximately 50% of the tubes in the outer region of the donut were inspected, while 20% of the tubes in the inner region of the donut were inspected. If the lower tube end was inspected, the lower roll transition was also inspected.
ENCLOSURE 1
- During the lower tube end inspections, no flaws were found in the inner region of the donut while 5 indications were found in the outer region. Of these 5 indications, 4 were in OTSG-B and 1 was in OTSG-A. All indications were circumferential and were located outside the pressure boundary.
- During the lower roll transition inspections, 2 volumetric indications were identified in OTSG-A. The circumferential and axial extent of these indications was small. The indications were classified as inner diameter initiated intergranular attack, but the licensee also speculated they could be scratches/gouges from the anchor pins associated with the eddy current manipulator.
With respect to the indications found during the inspection, the licensee indicated that:
- Most circumferential cracks in the upper tube ends would be repaired by re-rolling (the others would be plugged).
- All lower tube end flaws will be plugged.
- Most of the upper roll transition flaws will be repaired by re-rolling.
- Of the approximate 4000 re-rolled tubes in service, 3 in OTSG-A and 6 in OTSG-B required repair at the time of the call.
- Approximately 550 tubes are affected by intergranular attack in the upper tubesheet. Of these tubes, 2 in OTSG-A and 3 in OTSG-B required repair based on the voltage of the indications.
- No indications were found at dents in OTSG-A. In OTSG-B, 7 axial flaws were found at dents.
- No indications of wear required repair.
- Approximately 136 freespan flaws (groove intergranular attack or outside diameter initiated intergranular attack) were detected in OTSG-A and 63 were detected in OTSG-B.
- Two crack-like indications were found at the tube support plates.
- The number of freespan flaws found was greater than predicted; however, the number of freespan flaws found during the last outage may have been anomalously small, which skewed the prediction at that time. If the number of freespan flaws found during the last outage were not considered, the number of freespan flaws detected during the current outage would have been within projections.
- No flaws were detected during the lower tubesheet sludge pile inspections.
The lookback comparisons discussed in response to Question 7 of the NRCs April 2, 2004, letter, are performed by comparing the current data (1R18) to the data obtained in 1R13.
With respect to the licensees condition monitoring assessment, the amount of primary-to-secondary leakage under postulated accidents for the previous operating cycle was calculated to be 0.78 gpm, mostly from tube end cracking indications (which were responsible for 0.5 gpm of the projected leakage). Large-break loss of coolant accident (LBLOCA) projections were 2.57 gpm for the first 2 minutes and 1.49 gpm for the first 30 days.
With respect to the licensees operational assessment, the primary-to-secondary leakage was projected to be 0.680 gpm for the next operating cycle, mostly from the outer periphery tubes.
Extra re-rolling of periphery tubes in the tubesheet is expected to reduce the projected tube leakage from 0.8 gpm to 0.68 gpm.
In the discussion on the likelihood of loose parts, the licensee stated that the feedwater nozzles were designed and constructed in such a way that they serve as strainers during operation, thereby reducing the likelihood of loose parts.
The licensee stated that they were on schedule to replace their OTSGs during the Fall 2005 outage.
(THE FOLLOWING INFORMATION WAS PROVIDED BY ENTERGY)
NRC Conference Call During 1R18 Arkansas Nuclear One (Unit One)
Large Break LOCA Best Estimate Leakage:
LBLOCA leakage for 1R18 is predicted to be 2.57 gpm for the first two minutes and 1.49 gpm average leak rate for 30 days. Current ANO leakage limit is 9 gpm for the first two minutes and 3 gpm average leak rate. During 1R18 there were11 circumferential indications found inboard of the repair roll in the A OTSG and 6 in the B OTSG. Additionally, there were 52 circumferential indications found in the A OTSG located in the original roll or heat affected zone and 9 in the B OTSG.
- 1. Discuss whether any primary to secondary leakage existed in this unit prior to shutdown.
Minimal leakage was detected consistently throughout the cycle. Tritium averaged ~1.6 gpd during Cycle 18.
- 2. Discuss the results of secondary side hydrostatic tests.
There were no secondary side hydrostatic tests performed during 1R18.
- 3. For each steam generator, provide a general description of areas examined, including the expansion criteria utilized and type of probe used in each area.
SG A Area # Tested Probe Expansion Mechanism/Criteria FL Bobbin 14536 bobbin No Impingement, Wear, Axial IGA/ODSCC, Vol IGA Upper Roll 14109 plus point No Circ/Axial ODSCC Transition Circ/Axial PWSCC LTS Sludge 659 plus point No Circ/Axial ODSCC
& Dents Super Heat 128 plus point No (1) Circ/Axial PWSCC Dents I-600 101 plus point No OD IGA/SCC Sleeves Lower Roll 5014 Plus point Yes (2) ID/OD IGA/SCC Transitions Lower Tube 5014 Plus point Yes (2) Circ/Axial PWSCC End (1) expand based on EPRI GL; no cracks found (2) exception to EPTI GL; expand if more indications than predicted ENCLOSURE 2
SG B Area # Tested Probe Expansion Mechanism/Criteria FL Bobbin 15133 bobbin No Impingement, Wear, Axial IGA/ODSCC, Vol IGA Upper Roll 14654 plus point No Circ/Axial ODSCC Transition Circ/Axial PWSCC LTS Sludge 436 plus point No Circ/Axial ODSCC
& Dents Super Heat 65 plus point Yes (1) Circ/Axial PWSCC Dents I-600 69 plus point No OD IGA/SCC Sleeves Lower Roll 5257 Plus point Yes (2) ID/OD IGA/SCC Transitions Lower Tube 5257 Plus point Yes (2) Circ/Axial PWSCC End (1) expand based on EPRI GL; 1 crack found; critical area established (2) exception to EPRI GL; expand if more indications than expected
- 4. Discuss any exceptions taken to the industry guidelines.
Three exceptions were taken to two requirements in Revision 6 of the EPRI PWR SG Examination Guidelines. One exception was to use the bobbin probe for lower tubesheet examinations based on a site qualification when the technique is not Appendix H qualified as required in section 6.2. A 21% sample of the tubes in the kidney region were examined with plus point probes. No indications were found at the LTS dent/sludge pile region.
The other two exceptions are taken are on the inspection expansion requirements in section 3.6 and Table 3-2 for indications found in the lower tube ends and lower roll transitions.
Lower Tube Ends: An initial inspection scope of 34% of the tube ends in each steam generator identified 1 and 4 tube end circumferential cracks in A and B SG respectively.
A scope expansion to 100% was not performed because the cracks in this location cant burst and the original lower tube rolls limit the potential leakage from any crack indications. There was additional leakage calculated for the uninspected population.
Lower Roll Transitions: The lower roll transitions were examined as part of the lower tube end inspection. During the initial 34% sample two small volumetric indications (<
0.5 inches in either direction, <1 volt) classified as inside diameter IGA were found in A SG. Similar to the LTE exception these indications could not burst and leakage tests done on earlier IGA patches in the upper tubesheet demonstrated very little leakage.
The sample inspection was a 34% total of the LRT population.
- 5. Provide a summary of the number of indications identified to date of each degradation mode and SG tube location (e.g. tube support plate, top-of-tubesheet, etc). Also provide information such as voltages, and estimated depths and lengths of the most significant indications.
- ANO-1 1R18 Eddy Current Inspection Results Degradation/Area A OTSG B OTSG CM for Worse Indications Indications Case OTSG Upper Tube End Flaws 1775 1038 2380 Upper Tube End Flaws 48 6 N/A*
(Repairable)
Upper Roll Transition PWSCC 81 91 70 Re-Roll Indications 16 17 42 Upper Tubesheet Crevice 63 1 0 Upper Tubesheet IGA 2 3 0 Sleeves 0 0 49 Indications in Dents 0 8 15 (superheated region and LTS)
TSP Wear 0 0 0 TSP Flaws/Freespan 294 167 86 Lower Tubesheet 0 0 20 Lower Roll Transition PWSCC 0 0 0 Lower Roll Transition IGA 2 0 0 Lower Tube End Flaws 1 4 280*
- Repairable indications in the tube ends are accounted for in the upper tube end flaw totals. The repairable indications account for leakage the same as non-repairable indications located within the tube end.
One indication in a dent in the B OTSG passed in-situ screening criteria. This flaw was 64% average depth. 1.0v MRPC voltage. Many of the confirmed freespan flaws found during 1R18 were low voltage. None of the freespan flaws required in-situ pressure testing.
- 6. Describe repair/plugging plans for the SG tubes that meet the repair/plugging criteria.
Repairs have/will be made using I690 mechanical rolled plugs and re-rolls made in the UTS.
A SG B SG Plugs 234 78 Rerolls 233 110
- 7. Discuss the previous history of SG tube inspection results, including any "look backs" performed, specifically for significant indication or indications where look backs are used in support of dispositioning (e.g., manufacturing burnish marks).
Look backs are performed to disposition MBM indications based on history. For the indication to be classified as a MBM it must have received a rotating probe examination during a previous inspection. If there was a change in the bobbin examination signal the indication was scheduled for a rotating probe examination this outage. All wear indications that have been left in service from previous inspections have received a rotating probe examination. History review is performed on wear indications and if there is a change in the bobbin signature the indications is scheduled for a rotating probe examination this outage.
- 8. Discuss, in general, the new inspection findings (e.g., degradation mode or location of degradation new to this unit).
Two modes of degradation previously found at ANO-1 were found in new locations during this inspection. Two small patches of IDIGA were found in the lower transition rolls and five circ cracks were found in lower tube ends.
- 9. Discuss your use or reliance on inspection probes (eddy current or ultrasonic) other than bobbin and typical rotating probes, if applicable.
No inspection probes other than bobbin and typical rotating probes were used in 1R18.
- 10. Describe in-situ pressure test plans and results, if applicable and available, including tube selection criteria.
In-situ selection is performed in accordance with the EPRI guidelines. Screening is performed and all those flaws that pass the final screening criteria are tested. No bounding is performed. One in-situ test was performed on an axial crack in a freespan dent at the 15 TSP (tube 88-40 B SG) 1.0 v 0.25 in.64.3% PDA. The indication did not leak at 3 DP (4500 psi). The dent itself was 2.9 volts.
- 11. Describe tube pull plans and preliminary results, if applicable and available; include tube selection criteria.
There were no tube pulls during 1R18.
- 12. Discuss the assessment of tube integrity for the previous operating cycle (i.e.,
condition monitoring).
The techniques used were qualified or demonstrated equivalent with the EPRI PWR Steam Generator Examination Guidelines. Several modes of degradation were detected during the exams. Most forms were expected, with the exception small patches of IGA in two lower roll transition. By benchmarking actual inspection results to the projected values, reasonable projections can be made for EOC 19. The structural aspects of the various modes of degradation are either bound by 1R18 in-situ testing or considered not a concern based on location within the tubesheet (e.g., URT, re-roll flaws). Additionally, the HAZ flaws and the upper tubesheet IGA are being addressed through specific Technical Specification requirements. The conclusion of this condition monitoring evaluation is that none of the performance criteria in NEI-97-06 were exceeded and based on the comprehensive exams performed it is concluded that the EOC 18 condition would not exceed the performance criteria.
- 13. Discuss the assessment of tube integrity for next operating cycle (i.e., operational assessment).
The operational assessment will be performed in accordance with the NEI 97-06.
Potential for burst and leakage will be assessed before entering Mode 4 for a 90 day period to allow the development of the full cycle report.
OA .81 gpm in bounding OTSG
- 14. Provide the schedule for steam generator-related activities during the remainder of the current outage.
Eddy current testing complete Insitu testing 05/01/04 (Sat.)
Repair 05/03/04 (Monday)
Close Generator 05/05/04 (Wednesday)
- 15. With regard to loose parts, discuss the following:
- what inspections are performed to detect loose parts,
- a description of any loose parts detected and their location within the SG,
- if the loose parts were removed from the SG,
- indications of tube damage associated with the loose parts, and
- the source or nature of the loose parts, if known.
Eddy current inspections were used to detect the presence of loose parts touching steam generator tubes. No possible loose part (PLP) indications were identified during those examinations. No secondary side examinations were performed.
- 16. Once-Through Steam Generators: If you have Babcock and Wilcox (B&W) welded plugs installed in the SGs, be prepared to discuss the actions taken in response to Framatomes notification of the effect of tubesheet hole dilation on the service life of B&W welded plugs.
CR-ANO-1-2002-00280 During a recent review of calculations associated with OTSG Remote Welded Plugs (RWP) and Manually Welded, Taper Welded Plugs (MWP), Framatome discovered that the plugs are not qualified in accordance with the requirements stated in the equipment specification requirements and associated purchase order. Specifically, the stress reports define the design transient heatup/cooldown cycles were originally evaluated for 240 cycles. The stress reports submitted to Davis Besse for their most recent outage define the heatup/cooldown cycles be limited to less than 33 to maintain a fatigue life of less than one. The latest stress reports were developed with tubesheet dilation included.
RWPs were not installed in the ANO-1 OTSGs prior to 1993 so those plugs have seen less than 15 heatup/cooldown cycles.
The results of the current Framatome re-analysis shows that the MWP is acceptable for 144 heatup/cooldown cycles. None of the MWPs installed at ANO-1 have experienced heatup/cooldown cycles anywhere near 144. The most conservative number published by Framatome is 67 heatup/cooldown cycles for ANO-1 MWPs. ANO personnel have calculated 45 heatup.cooldown cycles (the discrepancy is based on a BWOG report that counted any plant power change other than normal power swings as a cooldown). Even with the most conservative heatup/cooldown cycles (67) ANO-1 is well within the acceptable limit of 144 heatup/cooldown.
- 17. Once-Through Steam Generators: Describe your inspection/plugging plans with respect to the industry-identified severed tube issue (NRC Information Notice (IN) 2002-02 and IN 2002-02, Supplement 1).
Inspections during 1R17 in October 2002 addressed the issues associated with the potential for severed tubes. 31 tubes were plugged and stabilized in the A OTSG and 30 tubes were plugged and stabilized in B OTSG. All tubes identified for plugging in 1R18 are screened for stabilization and the database cannot be closed with any wear indications found at the secondary face of either tubesheet.
Arkansas Nuclear One cc:
Executive Vice President Vice President, Operations Support
& Chief Operating Officer Entergy Operations, Inc.
Entergy Operations, Inc. P. O. Box 31995 P. O. Box 31995 Jackson, MS 39286-1995 Jackson, MS 39286-1995 Wise, Carter, Child & Caraway Director, Division of Radiation P. O. Box 651 Control and Emergency Management Jackson, MS 39205 Arkansas Department of Health 4815 West Markham Street, Slot 30 Little Rock, AR 72205-3867 Winston & Strawn 1400 L Street, N.W.
Washington, DC 20005-3502 Mr. Mike Schoppman Framatome ANP 3815 Old Forest Road Lynchburg, VA 24501 Senior Resident Inspector U.S. Nuclear Regulatory Commission P. O. Box 310 London, AR 72847 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 County Judge of Pope County Pope County Courthouse Russellville, AR 72801 June 2004