ML031740415

Enclosure 2 - BVPS 1R15 - NRC Outage Phone Call

ML031740415
Person / Time
Site:	Beaver Valley
Issue date:	06/20/2003
From:	Colburn T NRC/NRR/DLPM/LPD1
To:	Pearce L FirstEnergy Nuclear Operating Co
References
TAC MB7271
Download: ML031740415 (8)

Text

BVPS R15 NRC Outage Phonecall

1. Discuss whether any primary to secondary leakage existed in this unit prior to shutdown. Include values of any calculated leakage and trends relative to previous outages.

Maximum leakage of 0.05 gpd in SGB was reported during the cycle. The value remained relatively constant, with fluctuation between 0.03 and 0.05 gpd. During cycle 13 primary to secondary leakage of a maximum of 0.3 gpd in SG B had been reported.

After a mid-cycle trip, the leakage was not reported.

2. Discuss the results of secondary side pressure tests.

None were perfonned.

3. For each SG examined, provide a general description of areas examined, including the expansion criteria utilized and type of probe used in each area.

Also, please be prepared to discuss your inspection of the tubesheet area.

See attached Table All hot leg tubes were tested from 6" above to nominally 8" below the top of hot leg tubesheet. Prior to the outage, a reanalysis of lR14 bobbin data was performed to determine the bottom of WEXTEX transition. These values were used to ensure that all tubes were tested to a minimum distance to ensure structural integrity based on the W*

analysis provided in WCAP-14797 Rev 1.

4. Discuss any exceptions taken to the industry guidelines.

• Bobbin coil is being used for detection of significant axial PWSCC flaws within tubesheet region. Bobbin coil has no EPRI qualification for detection of axial degradation within this area.

• BVPS does intend to supply the CM/OA if a C-3 condition is reported as NRC has indicated it does not wish to receive all of the industry's assessments.

FENOC will supply the CM/OA if a C-3 condition is observed and CMtOA is requested by NRC

• Not all Alloy 690 roll plugs will be inspected within a 60 EFPM window. There have been no industry events involving degradation of Alloy 690 roll plugs.

BVPS has performed a 20% RPC sample of Alloy 690 roll plugs for the past 3 outages. Alloy 690 roll plugs were not sampled at the R15 outage.

ENCLOSURE 2

5. Provide a summary of the number of indications identified to date of each degradation mode and SG tube location. Also, provide information such as voltages, and estimated depths and length of the most significant indications.

TTS and historic sludge pile region:

SGA: 3 axial PWSCC, 16 axial ODSCC, 6 circ ODSCC, 1 volumetric (wear)

SGB: 5 axial PWSCC, 23 axial ODSCC, 2 circ ODSCC SGC: 10 axial PWSCC, 6 axial ODSCC Total: 18 axial PWSCC, 45 axial ODSCC, 8 circ ODSCC At R14, 13 axial PWSCC, 78 axial ODSCC, and 3 circ ODSCC tubes were reported.

The large number of axial OSCC reports at R14 is attributed to increased detection capabilities resultant from chemical cleaning.

Axial PWSCC: 1.89 volts maximum, longest length 0.34", deepest depth from phase 93%, deepest depth from amplitude 72%.

Axial ODSCC: 0.31 volts maximnum, longest length 0.95", deepest depth from phase 99%, deepest depth from amplitude 57%

Circ ODSCC: 0.24 volts, longest length 121° arc, deepest depth from phase 97%,

deepest depth from amplitude 74%

U-bend Region:

SGA: I circ PWSCC Rowl, I axial PWSCC >Row 2 (R42 C28)

SGB: 1 axial PWSCC >Row 2 (R13 CIO)

SGC: 2 axial PWSCC >Row 2 (R17 C22, R13 C61)

Largest amplitude: 2.52 volts circ, 1.2 volts axial, longest length 490 circ, 2.9" axial (reported flaw length believed to be affected by coincident scratch), deepest depth circ 60% phase, 83% amplitude, deepest depth axial 80% phase, 59% amplitude.

TSP ODSCC:

Very similar to IR14 distributions. Max DSI voltage reported was 4.59 volts in SGA.

Max DSI voltage reported in SGB was 2.26 volt, SGC max DSI voltage was 2.5 volts.

Total number of indications >2V is 11 in SGA, 6 in SGB, 5 in SGC. The maximum reported DSI amplitude at IR14 was 5.3 volts in SGC.

Freespan:

No ODSCC reported other than 1 ding crack. (see question #8)

One tube reported with a volumetric, believed to be a possible lap indication from original tube drawing.

AVB: One repairable indication reported at 40%TW CLT: Three repairable indications, 42%, 43%, and 51%

6. Describe repair/plugging plans for the SG tubes that meet the repair/plugging criteria.

All crack-like and volumetric (foreign object wear) indications located in the freespan and tubesheet regions are repaired by plugging. Any PWSCC indication located at TSP intersections are repaired by plugging (none found). TSP ODSCC indications are repaired per GL 95-05. AVB wear and cold leg thinning indications are repaired according to the technical specification 40% depth criteria.

7. Discuss the previous history of SG tube inspection results, including any look backs performed; specifically for significant indications where look backs are used in support of dispositioning (e.g., MBMs).

Most hot leg top of tubesheet indications contain precursor signals. Bobbin signals identified in the freespan region were reviewed against the RI 1 (1995) bobbin data to ensure that if slow growing ODSCC mechanisms are present that a change in the signal would be identified.

8. Discuss in general, new inspection findings.

One ding ODSCC indication was reported in SGB at O1H +3.2". The ding amplitude was 6.39 volts, thus the bobbin screening technique could not be applied. This indication was found during the 20% >5V ding program. Expansion to 100% of all dings >5V in SGB was performed.

Three tubes have been reported with signals suggestive of axial PWSCC in large radius U-bends. Two appear to be associated with dents at AVB locations. The third is slightly above the hot leg tangent point. Additional inspection techniques are being considered.

One tube was reported with two small signals suggestive of circumferential ODSCC at the 07H support. These signals are very similar to signals observed just above the top of tubesheet in 1R15 and IR14 that were judged to be possible anomalies due to SG assembly. These tubes were repaired by plugging. Additional inspection techniques are being considered to help to detennine the validity of these indications.

Axial ODSCC was reported at a dented intersection on the hot leg (2.91 volts).

Estimated ODSCC depth is 46%TW. Expansion to 100% of all dents > 2 volts was performed. Two additional indications was reported in 3.1 and 2.5 volt dents. Estimated ODSCC depth is 60% and 51%TW, respectively.

Parent tube anomalies were reported within the tube original hardroll region of 28 sleeved tubes. The area of the tube where the anomalies are reported is adjacent to the

sleeve hardroll region. These sleeved tubes will be plugged. It is suspected the cause of the anomaly is due to a heat affected zone or possible permeability variation since all tubes had TIG relaxed plugs prior to sleeving.

The blowdown pipe support bracket was found to be separated from the weld that secures the bracket to the tubesheet. Visual examination indicates that the bracket experienced limited bonding with the weld. Dynamic analysis indicates that the free end of the blowdown pipe will not contain adjacent active tubes and will remain structurally intact for remainder of SG service period.

9. If SGs contain Alloy 600 thermally treated tubing.......

Alloy 600 thermally treated tubing is not used in the BVPS Unit 1 SGs.

10. Discuss use or reliance on inspection probes other than bobbin and typical rotating probes.

None are used as part of the base eddy current program. The Ghent3/4 probe is being considered to help to validate some of the flaw reports.

11. Describe in situ pressure test plans and results, including selection criteria.

Selection criteria follows the EPRI in situ guideline recommendations. All indications requiring testing are tested. In addition, all new degradation mechanisms with the exception of the reported axial ODSCC at a dented TSP intersection will be pressure tested.

12. Describe tube pull plans.

None scheduled.

13. Discuss the assessment of tube integrity for the previous operating cycle (i.e.,

condition monitoring).

The EPRI tube integrity guideline and in situ pressure test guidelines were used. All indications at R14 were shown to provide margin against the performance criteria.

Benchmarking of previous results indicate that the predicted limiting flaws for R15 are conservative compared to the observed flaw-like indications.

14. Discuss the assessment of tube integrity for the next operating cycle.

The EPRI tube integrity guidelines will be used for evaluation of tube integrity at EOC

16. No indications have been reported at RI5 that suggest that structural or leakage integrity would be challenged at EOC 16.

Additional Questions:

1. Collapsed sleeves, how was weld and roll integrity verified? Has potential for sleeve collapse been considered in T/H evaluations.

Four sleeves were found to be collapsed at IR14. Visual examination indicated that sleeve had experienced a localized dimpling that progresses no further than the sleeve axis. A structural evaluation was performed that concluded that based on tube to sleeve internal pressures sufficient to cause collapse, combined with sleeve strain effects, would not cause the weld to be stressed past yield, nor would axial loads exceed the hardroll joint breakaway load.

One additional sleeve was found to be collapsed at IRI5.

This phenomenon has been previously reported in the industry. It has been associated with typically the first ISI after sleeve installation. The BVPS results are consistent with industry experience. Current tube plugging analysis supports 30% plugged. Historical information, as well as BVPS R14 and R15 data suggest that no further collapsed sleeves will be identified at R16.

2. Clarify how mixed residuals are dispositioned.

The BVPS mixed residual reporting level is 1.5 volts, which is substantially more conservative compared to other 7/8" OD plants. The 100 largest mixed residual signals that could mask a flaw are RPC tested, along with all mixed residual signals with a phase angle of <50°. All mixed residuals that have been confirmed to contain axial ODSCC have been able to have a mix channel DSI amplitude extracted using the 200 kHz bobbin channel. As a DSI signal can be extracted, nixed residuals that are confirmed to contain axial ODSCC are changed to a DSI code and included in the GL 95-05 analysis. To date, 86 SPRs have been confirmed to contain axial ODSCC. Over 400 SPRs have been +Pt tested. Using the +Pt volts vs DSI voltage correlation, <10 SPRs contain > 1 volt flaw signals.

3. Differentiate between a DSI and a PSI.

DSI is a distorted support plate signal that could represent axial ODSCC at a TSP intersection. PSI is a possible support indication that could represent a flow hole misdrilling that results in either a locally thinned tube hole ligament or partially missing ligament. RPC is used to estimate the amount of "missing" ligament arc length. If missing material is found by RPC, the PSI is changed to CSI. The RPC value is compared against a threshold limit determined by analysis that considers the amount of material that is required to be removed to permit the tube to escape from the tube hole.

All PSI/CSI indications are excluded from ARC application.

4. Clarify cold leg top of tubesheet indications from lR14.

All cold leg top of tubesheet indications were associated with loose part wear or wear due to sludge lance rail interaction. The sludge lance equipment used at R13 and R14 was not used at R15. No cold leg indications have been reported at R15.

Table 2-2 Detection Inspection/Exp nsion Plan: Beaver Valley Unit 1, R15 Inspection Degradation Location Probe Type Detection Inspection/Expansion Plan Mechanism Inspection Sample Plan Expansion Plan Active Degradation Mechanisms Axial ODSCC Non-Dented TSP Bobbin 100% full length bobbin (except Row I and 2 None Intersections U-bend regions)

Non-Dented TSP Plus Point 100% bobbin indications >2 volts, 100 largest 100 additional mixed residuals > 1.5 Intersections mixed residuals > 1.5 volts per SG volts if DSI > I volt reported in MRI (confinrnation only) >1.5 but < 2 volts per SG Axial ODSCC Hot leg sludge pile Bobbin 100% full length bobbin None and freespan Plus Point 100% HL TTS 6" above TTS to 8" below 20% cold leg TTS from +6 to -8" at TTS nominal either R15 or lR16 if C-3 Axial PWSCC Row land 2 U-bends Plus Point 100% Row land 2 U-bends, 20% Row 3 U- 100% Row 3 in SGs with Row 3 bends indications Axial and Circ. HL TTS expansion Plus Point 100% HL TTS 6" above TTS to 8" below 20% cold leg TTS from +6 to -8" at ODSCC transition TTS nominal either IR15 or IR16 if C-3 Axial PWSCC Hot Leg TTS Plus Point 100% HL TTS from 6" above to 8" below 20% cold leg TTS from +6 to -8" at expansion transition TTS nominal either IRI5 or IR16 if C-3 and within tubesheet Thinning Cold Leg TSP Bobbin 100% full lengti bobbin all SGs None intersections I Resolution for Classification of Indications Freespan Freespan Bobbin 100% full length, all SGs Historical review; RPC if no history Differential or changed Potential MBMs All Bobbin 100% full length, all SGs Historical review; RPC if no history or changed Relevant Degradation Mechanisms Axial ODSCC Freespan Bobbin 100% full length bobbin all SGs lNone Axial PWSCC Dented TSP Plus Point 20% dented hot leg intersections and freespan 100% dented hot leg intersections and intersections, freespan dings > 2 volts between TTS and 03H freespan dings > 2 volts between TTS dings and 03H Axial ODSCC Dented TSP Plus Point 100% intersections > 5 volt None Intersections > 5 volt

Table 2-2 Detection nspection/Exp nsion Plan: Beaver Valley Unit 1, R15 Inspection Degradation Location Probe Type Detection Inspection/Expansion Plan Mechanism Inspection Sample Plan Elxpansion Plan Circumferential CL TTS expansion Plus Point 20% cold leg ITS from 6" above to 8" below 100% in SGA, 20% SGs B and C ODSCC transition TTS nominal in SGA concentrated within historic sludge pile region Axial PWSCC Within Tubesheet Bobbin 100% full length bobbin all SGs None (below transition)

Pitting Cold leg TTS Bobbin 100% full length bobbin all SGs None Plus Point 20% cold leg TTS from 6" above to 8" below fTS in Per Table 3-3 of EPRI Rev. 5 ISI SGA guidelines Tube Wear AVB intersections Bobbin 100% full length bobbin all SGs None Tube Wear (loose TIS periphery, tube Bobbin 100% full length bobbin +FOSAR None parts) lane Plus Point 100% hot leg TTS from 6" above to 8" below None unless FOSAR identifies ITS objects on CL Axial ODSCC Freespan dings Bobbin 100% full length, all SGs None Plus Point 20% FS dings > 5volts, flaw confirmation of 100% freespan dings > 5 volts in SGs bobbin indications with indications Oblique PWSCC U-bend of Rows 3 to Plus Point 100% U-bends Rows 3 thru 46 None 10 Potential Degradation Mechanisms Axial ODSCC Expanded CL TSP 3-coil Plus Point 100% expanded intersections in SG A None (expanded tubes found in SG A intersections only)

General SCC or Sleeves Bobbin 0.640" 100% all sleeves None wastage Circ. PWSCC Parent tube of LWS Plus Point 100% all LWS joints None ijoints and Laser Welds Undefined Parent tube in sleeve Plus Point 20% LWS roll expansion joints 100% LWS roll expansion joints if I roll region (1) I _I _ indications detected