ML030550720

Attachment - 05/20/2002 Summary of Conference Call with Pacific Gas & Electric Co. 2002 Steam Generator Inspection Results at Diablo Canyon Unit 1

ML030550720
Person / Time
Site:	Diablo Canyon
Issue date:	04/01/2003
From:	Shukla G NRC/NRR/DLPM/LPD4
To:	NRC/NRR/DLPM/LPD1
Shukla G
Shared Package
ML030910575	List: ML030550720
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Download: ML030550720 (5)

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I Girija Shukla - 1 Rll NRC phone call.doc Page 1 I.i.ia.Shkla......NC.phne cII o.. Pge.

Diablo Canyon Power Plant - 1 R 1 May 20, 2002 Steam Generator Tube Inspection Results Areas of discussion:

1. Primary to secondary leakage prior to shutdown:

A small P/S leak of 1.03 gpd existed prior to shutdown. It was first detected in August 1998.

Leakage during the most recent cycle averaged 1-2 gpd. It is -thought to be in SG 1-4 based on tritium analysis. There is a high probability this leakage is through a plug.

2. Results of secondary side hydro:

No secondary hydro was performed because the small leak rate would make it very difficult to find the leak with a secondary pressure test.

3. For each steam generator, a general description of areas examined; include expansion criteria and specify type of probe used in each area:

See attached table from the Degradation Assessment.

4. For analyzed EC results, describe bobbin indications (those not examined with RPC) and MRPC/Plus Point indications. Include the following information: location, number, degradation mode, disposition, and voltages/depths/lengths of most significant indications:

Discussion.

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

Discussion.

6. Discuss of previous history of SG inspection results, including any "look backs" performed.

Discussion.

7. Discuss in general any new inspection findings, including loose parts indications.

Discussion.

8. Discuss your use or reliance on the X-probe, if applicable.

The x probe was used to inspect 6 tubes in the WEXTEX area. This was for information only. These tubes had been inspected with +Point.

9. Describe in-situ pressure test plans and results; include tube selection criteria, test pressure plans, test configuration:

No in-situ testing was performed.

d irija Shukla - 1R1 1 NRC phone call.doc. Page 2 10.Describe tube pull plans and preliminary results; include tube selection criteria and evaluation plans:

No tubes were pulled.

11.Discuss assessment of tube integrity for previous operating cycle:

All inspection findings met the performance criteria for structural and accident induced leakage. Largest flaws by category will be discussed.

12 .Discuss assessment of tube integrity for next operating cycle:

Based on the size of detected flaws, historical flaw growth rates, and planned cycle length, all tubes will retain adequate margin for structural and leakage integrity over the next cycle.

13 .Provide schedule for steam generator-related activities during remainder of current outage.

Nozzle dams will be removed this afternoon.

14.Discuss what steps have been taken, or will be taken, in response to the lessons learned from the Indian Point Unit 2 tube failure.

Data quality and noise criteria have been established for Row 1 & 2 U bend data. Vertical RMS noise was measured in each tube U bend at both tangents and the apex. Noise measurements were compared with the EPRI ETSS 96 511 data set. Nine tubes were plugged because the U bend data did not meet the noise criteria.

In addition, please be prepared to discuss the following:

a) Discuss the actions that are taken in response to identifying a new degradation mechanism:

The DA would be updated to define inspection scope, techniques, etc for the new degradation in the current inspection. The finding would be entered into PG&E's corrective action program (i.e., an AR would be initiated). The preliminary OA would be modified to address the new degradation. Growth rates and supporting information would be obtained as possible and the 90 day OA would address cycle length with the new degradation mechanism.

b) Discuss the actions taken to ensure that data noise levels are acceptable:

See item 13 above for U bends. Noise criteria have also been implemented for other + Point and bobbin inspection data.

c) Address data quality issues and the need for criteria to address data quality:

See item 14 above for U bends. Data quality criteria have also been implemented for other + Point and bobbin inspection data.

I Girija Shukla - 1R11 NRC phone call.doc Page 3 Table 1 - 1 RI 1 SG Tube Inspection and Expansion Plan Area J Probe Inspection Cntena ECT Inspections J Expansion Cntena Full Length Bobbin 100% 13026 N/A 2 Short Radius U- +Point 100% - Rows 1 and 2 U-bends 692 R1&2 IfSCC found In Row 2, inspect Bends In all SGs 38 R3 20% of Row 3 in affected SG. If 20% - Row 3 U-bends in SG 11 SCC found in Row 3, inspect and SG 13 100% of Row 3 and 20% of Row 4 in affected SG Continue "expansionin this manner until a flaw free 20% sample Is obtained in the next row U-bend 3 WEXTEX TTS +Point

• 100% of HL TTS 13026 If C-3 condition is identified In Region

• Extent is +2* to -8" HL TTS, inspect 20% of CL TTS 0 PTE/NTE anomaly extent in affected SG If indications is +2 to tube end found In CL, follow EPRI Tables 3-1 and 3-2 for further expansion requirements If cracking found in HL tubesheet anomalies, inspect 100% of CL I_ _tubesheet anomalies.

4 Repeat PWSCC at +Point

• 100% 112 N/A dents and TTS 5 >5 volt dents +Point

• SG 1-1: 100% at lHto 1264 IfPWSCC (at any size dent),

4H, 20% at 5H to 7H circumferential indications (at

• SG 1-2 100% at 1H to any size dent), or AONDB (at >5 6H, 20% at 7H volt dent) are detected at a TSP

• SG 1-3 20% at 1H to 7H elevation where 100%

• SG 1-4 100% at 1H to inspections were not required, 3H, 20% at 4H to 7H expand the Plus Point

• For each 20% sample, inspections (in a step-wise inspect at least 50 dents, manner, 100% to affected TSP or else inspect 100% If and 20% at next TSP) up there are less than 50 through the hot leg side of the dents SG and down the cold leg side until a 20% sample is obtained that is free from PWSCC, circumferential cracking, or> 2 inferred volt AONDB 6 >2 and <5 volt dents +Point 0 SG 1-1: 100% at 1H to 1531 If PWSCC (at any size dent),

4H, 20% at 5H circumferential Indications (at 0 SG 1-2 100% at 1H to any size dent), or > 2 inferred 6H, 20% at 7H volt AONDB (at >2 and <5 volt SSG 1-3 20% at 1H dent) are detected at a TSP

• SG 1-4 100%atlHto elevation where 100%

3H, 20% at 4H inspections were not required,

• For each 20% sample, expand the Plus Point inspect at least 50 dents, inspections (in a step-wise or else inspect 100% if manner, 100% to affected TSP there are less than 50 and 20% at next TSP) up dents through the hot leg side of the SG and down the cold leg side until a 20% sample is obtained that is free from PWSCC, circumferential cracking, or > 2 1 inferred volt AONDB

I Girija Shukla - 1R1l NRC phone call.doc PaQe 4 7 Distorted ID support +Point

• 100% of DIS calls by 600 DIS, If a circ indication or >2 inferred plate bobbin signals bobbin assuming Plus volt AONDB is detected in a (DIS) Point dent of x" volts, then Plus Point confirmation of inspections shall be conducted 60 new axial on 100% of dents greater than PWSCC "x - 0 3" volts up to the affected indications TSP, plus 20% of dents greater (similar to than "x- 0 3" volts at the next 1Rl0), with 90% higher TSP. "x" is defined as overcall rate by the lowest dent voltage where a bobbin circ crack or >2 inferred volt AONDB was detected in that SG Note Forany20%

sample, a minimum of 50 "x 0 3" volt dents shall be inspected If the population of "x

- 0 3" volt dents at that TSP elevation is less than 50, then 100% of the "x- 0 3" volt dents at that TSP shall be instnented 1 I I- 4- I 8 Distorted OD +Point

• DOS at < 5 volt dented 132 DOS N/A support plate bobbin intersections 20 SPR signals (DOS) and Z 2 volt DOS voltage-based ARC

• DOS with suspected TSP implementation ligament cracking

• DOS in the wedge region exclusion zone

• DOS at 7th TSP exclusion zone

• DOS that extend outside the TSP crevice

• copper signals

• Mix residuals- all HL intersections > 2 3 SPR volts, and minimum of 5 largest HL SPR per SG (CDS determines SPR voltaae at each TSPI 9 Suspected TSP +Point

• Plus Point inspect 20% of 86 baseline It active degradation is detected Ligament Cracking existing baseline inspections, plus in the 20% sample inspection, (SLC) indications, satisfied by any new SLC then the Plus Point inspection 100% inspection of calls will be expanded to 100 percent baseline indications In SG of the baseline population 11 and 14 Active degradation is defined as

• Plus Point inspect all new service-induced TSP ligament bobbin SLC indications erosion-corrosion and/or Bobbin analysis- cracking

"* CDS of I R1l bobbin data to identify SLC

"* Low frequency bobbin review of TSP at intersections with distorted support signals to identify I SLC 10 Free Span Dings (> +Point

• In each SG, 20% from 79 If PWSCC is found in 20%

2 volts) TSH to 7H sample, then expand inspections in the affected SG by inspecting 100% of >2 volt dings up to affected free span 11 Mechanical Plugs Visual Visual inspection of all existing plugs to venfy they are intact and show no signs of leaking _

12 Cold Leg Thinning +Point 0 New CLT indications 10 N/A

. CLT indications in the wedqe zone I

IGirija Shukla - 1R1 1 NRC phone call.doc Page 5 13 Free Span Bobbin +Point 100% of free span bobbin 12 N/A Indications indications that are new or exhibit growth or change (MBI, FSI, DNI) 14 Loose Parts Bobbin

• Review bobbin data of row 10 N/A

+Point 1&2 and penphery tubes

• +Point of PLP and surrounding tubes

• +Point of loose parts detected by FOSAR 15a Deplugged Tubes Bobbin

• 100% 150 N/A full length 15b Deplugged Tubes +Point

• 100% of HL TTS 150 N/A WEXTEX region _ Extent is +2" to -8" 15c Deplugged Tubes +Point

• Onginal flawed TSP 375 N/A TSP 0 100% of DOS and DIS, regardless of voltage 0 100% of >2 volt hot leg dents a 100% of SLC indications