CPSES-200601296, Response to RAI, Relief Request A-1 for the Unit 2 Inservice Inspection for Application of an Alternative to the ASME Boiler and Pressure Vessel Code Section XI Examination Requirements for Class 1 and 2 Piping Welds..

Response to RAI, Relief Request A-1 for the Unit 2 Inservice Inspection for Application of an Alternative to the ASME Boiler and Pressure Vessel Code Section XI Examination Requirements for Class 1 and 2 Piping Welds..

ML061990400
Person / Time
Site:	Comanche Peak
Issue date:	06/27/2006
From:	Madden F TXU Generation Co, LP, TXU Power
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CPSES-200601296, TAC MC9503, TXX-06101
Download: ML061990400 (6)

Text

6-4,TXU v', Power TXu Power Mike Blevins Comanche Peak Steam Senior Vice President &

Eiectric Station Chief Nuclear Officer Ref: 10 CFR 50.55a P.O. Box 1002 (EO1)

Glen Rose, TX 76043 Tel: 254 897 5209 Fax: 254 897 6652 mike.blevins@txu.com CPSES-200601296 Log # TXX-06101 June 27, 2006 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)

DOCKET NO. 50-446 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION, RELIEF REQUEST A-1 FOR THE UNIT 2 INSERVICE INSPECTION FOR APPLICATION OF AN ALTERNATIVE TO THE ASME BOILER AND PRESSURE VESSEL CODE SECTION XI EXAMINATION REQUIREMENTS FOR CLASS 1 AND 2 PIPING WELDS (INTERVAL START DATE-AUGUST 3,2004, SECOND INTERVAL)

TAC NUMBER MC9503 REF: TXU Power letter, logged TXX-05204, from Mike Blevins to the NRC dated December 15, 2005 Gentlemen:

By means of the referenced letter, TXU Generation Company LP (TXU Power) previously submitted relief from the ASME Section XI code examination requirements for inservice inspection of Class 1 and 2 piping welds (Categories B-F, B-J, C-F-I, and C-F-2) for Comanche Peak Steam Electric Station (CPSES) Unit 2.

Based upon questions provided by Mr. Mohan Thadani of the NRC in an email dated June 1, 2006, TXU Power hereby provides the following additional information.

Attachment I to this letter contains the NRC questions and TXU Power's response immediately following each question.

A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway - Comanche Peak

• Diablo Canyon - Palo Verde

• 10ý11 South Texas Project

• Wolf Creek

TXX-061 01 Page 2 of 2 This communication contains no new licensing basis commitments concerning CPSES Unit 2.

Sincerely, TXU Generation Company LP By: TXU Generation Management Company LLC, Its General Partner Mike Blevins By: k Z: z

/ Fred W. Madden" Director, Regulatory Affairs JCH Attachment c- B. S. Mallett, Region IV M. C. Thadani, NRR Resident Inspectors, CPSES

Attachment I to TXX-06101 "Page I of 4 TXU POWER COMANCHE PEAK STEAM ELECTRIC STATION RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELIEF REQUEST A-I FOR THE UNIT 2 INSERVICE INSPECTION FOR APPLICATION OF AN ALTERNATIVE TO THE ASME BOILER AND PRESSURE VESSEL CODE SECTION XI EXAMINATION REQUIREMENTS FOR CLASS I AND 2 PIPING WELDS TAC NUMBER MC9503 DOCKET No. 50-446

Attachment I to TXX-06101 Page 2 of 4

1. NRC Ouestion:

What system are segments I -ACC03A and I-ACC03B in, and what was the effect on Table I when the consequence changed from medium to high?

2. NRC Ouestion:

What changes to the number of components selected for inspection were made as a result of he consequence change from medium to high for the segment I -RHR08A? Explain the rationale for any change or the number remaining the same.

TXU Response to I and 2:

The changes referenced in these two questions are subject to a common rationale. I -ACC03A and 1 -ACC03B are not piping segment designators, but rather are consequence identifiers associated with SIS piping segments SIS-017, SIS-018, SIS-019 and SIS-020. 1-RHR08A is not a piping segment designator, but rather a consequence identifier associated with SIS piping segment SIS-066. These segments are not subject to any degradation mechanism, which results in a failure potential rank of Low. In conjunction with the previous consequence rank of Medium, they were Risk Category 6a, Low risk, with no associated inspections. The change in consequence rank to High resulted in a Risk Category 4, Medium Risk. RI-ISI weld selections are made based on the total weld count in a particular Risk Category in a specific system. The addition of these piping segments, in conjunction with the change resulting from the increase in Consequence SI101 from Medium to High, resulted in an increase in the weld count of 142 welds for Risk Category 4 in the SIS system. Since Risk Category 4 requires inspection of 10% of the population, the RI-ISI inspections for SIS Risk Category 4 were increased by 15.

, Attachment I to TXX-06101

'Page 3 of 4

3. NRC Ouestion:

Where does the class boundary for the Auxiliary Feedwater system change from Class 2 to Class 3?

TXU Response to 3:

The ASME Code Class 2/3 breaks occur on the upstream side of the following valves associated with the following pumps, as indicated on CPSES flow diagram M2-0206, Auxiliary Feedwater System, and as listed below:

TDAFW Pump 2-HV-2491A (TDAFW Pump 2-01 discharge to SG 2-01 isolation valve) 2-HV-2492A (TDAFW pump 2-01 discharge to SG 2-02 isolation valve) 2-HV-2493B (TDAFW pump 2-01 discharge to SG 2-03 isolation valve) 2-HV-2494B (TDAFW pump 2-01 discharge to SG 2-04 isolation valve)

MDAFW Pump A 2-HV-2491B (MDAFW pump 2-01 discharge to SG 2-01 isolation valve) 2-HV-2492B (MDAFW pump 2-01 discharge to SG 2-02 isolation valve)

MDAFW Pump B 2-HV-2493A (MDAFW pump 2-02 discharge to SG 2-03 isolation valve) 2-HV-2494A (MDAFW pump 2-02 discharge to SG 2-04 isolation valve)

4. NRC Ouestion:

In the original relief request for application of an alternative to the ASME Boiler and Pressure Vessel Code Section XI examination requirements for class 1 and 2 piping welds, reference was made to the "recent event at the V.C. Summer facility in which through-wall cracking was discovered in a 34-inch main loop hot leg reactor pressure vessel nozzle." TXU Power stated that industry progress would be closely monitored and recommendations would be assessed for applicability.

a. How has this event been considered in the update to the risk-informed inservice inspection (RI-ISI) program?

b. Is Primary Water Stress Corrosion Cracking (PWSCC) now considered as a degradation mechanism for dissimilar metal welds?

c. How will MRP-139 be addressed with respect to the RI-ISI Program?

Attachment 1 to TXX-06101

'Page

• of 4 TXU Response to 4a:

The event at V.C. Summer along with some other industry events led to the Materials Reliability Program developing MRP-139, which identified butt weld locations susceptible to primary water stress corrosion cracking (PWSCC) and developed approaches for inspection, re-inspection, mitigation, and flaw evaluation, and was issued on July 14, 2005. The issue and actions from MRP-139 are captured in the Corrective Action Program at CPSES in SMF-2005-003502. Since the interval for Unit 2 ended on August 2, 2004, the information per MRP-139 is not included in this Relief Request TXU Response to 4b:

During the evaluation/update process for RI-ISI which occurred for the end of the third period and coincided with the end of the first interval for Unit 2, CPSES Report ER-ME-107, Degradation Mechanism Evaluation of Class 1 & Class 2 Piping in Support of ASME Code Case N-578, was revised to remove assumption 7 which stated that " Bi-metallic welds with Inconel buttering are not considered susceptible to the PWSCC degradation mechanism."

This was removed based on the new criteria being addressed in the industry to address PWSCC in bi-metallic welds with Inconel buttering. PWSCC will be considered as a degradation mechanism for dissimilar welds, and as stated previously, will be addressed in the next RI-ISI evaluations/updates for Units I and 2, which are scheduled for 2007.

TXU Response to 4c:

As stated previously, MRP-139 issue and actions to be taken are captured in the Corrective Action Program under SMF-2005-003502 for CPSES Units I and 2. The RI-ISI will address these new degradation mechanisms to their previous RI- ISI rankings for the affected documents and will make the necessary changes to the plant specific documents, which for CPSES are ER-ME-107 and ER-EA-012, Consequence Evaluation of Class 1 & Class 2 Piping in Support of ASME Code Case N-578. These welds and examination requirements will then be captured in the either the ISI or AISI Program Plans.

5. NRC Question:

Note 6 of Table 1 states, "due to a change in ASME Section XI Code criteria, 4 (inch) NPS Class 2 auxiliary feedwater piping was added to the ISI Program, and therefore, the RI-ISI Program, for the first time during the third ISI interval." This relief request, dated December 15, 2005, states the alternative to the code requirements is to be used for the second interval of Unit 2. Please, explain this apparent discrepancy.

TXU Response to 5:

Note 6 of Table I should state that "4-inch AF piping was added to the ISI Program for Unit 2 for the first time during the second ISI interval." A typographical mistake was made.