ULNRC-04993, Revision of Request for Relief from ASME Section XI Requirements in Order to Temporarily Restore Wall Thickness of ASME Class 2 Carbon Steel Main Feedwater Piping by Weld Overlay Reinforcement

Revision of Request for Relief from ASME Section XI Requirements in Order to Temporarily Restore Wall Thickness of ASME Class 2 Carbon Steel Main Feedwater Piping by Weld Overlay Reinforcement

ML041470046
Person / Time
Site:	Callaway
Issue date:	05/07/2004
From:	Keith Young AmerenUE
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ULNRC-04993
Download: ML041470046 (11)

Text

AmerenUE Cal/away Plant PO Box 620 Fulton, MO 65251 May 7, 2004 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop P1-137 Washington, DC 20555-0001 Ladies and Gentlemen:

ULNRC-04993 10 CFR 50.55a WAmerefUF DOCKET NUMBER 50-483 CALLAWAY PLANT UNION ELECTRIC CO.

REVISION OF REQUEST FOR RELIEF FROM ASME SECTION XI REQUIREMENTS IN ORDER TO TEMPORARILY RESTORE WALL THICKNESS OF ASME CLASS 2 CARBON STEEL MAIN FEEDWATER PIPING BY WELD OVERLAY REINFORCEMENT Pursuant to 10CFR50.55a(a)(3)(i), and by letter ULNRC-04875 dated July 22, 2003, as revised by letter ULNRC-04942 dated January 22, 2004, Union Electric Company (AmerenUE) submitted for NRC approval a request for relief from requirements in Section XI of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) to permit temporary weld overlay reinforcement of potentially affected ASME Class 2 carbon steel piping sections associated with the main feedwater system at Callaway. In its "ULNRC-04875, Request for Relief from ASME Section XI Requirements in Order to Restore Wall Thickness of ASME Class 2 Carbon Steel Main [[system" contains a listed "[" character as part of the property label and has therefore been classified as invalid. Piping by Weld Overlay Reinforcement|July 22, 2003 letter]], AmerenUE requested NRC approval of the requested relief by March 1, 2004, i.e., in advance of the forthcoming refueling outage (RF-13). In accordance with that request, NRC approval was obtained prior to the onset of RF-13 which is now underway at Callaway. The requested relief was granted by NRC letter dated April 7, 2004, which included a safety evaluation prepared by the NRC's Office of Nuclear Reactor Regulation.

As described in AmerenUE's letter(s) and as acknowledged in the NRC's April 7 letter, the intended scope of the relief request was limited to particular areas in the feedwater system piping where, due to wall thinning monitored under Callaway's Flow-Accelerated Corrosion (FAC) program, projected pipe wall thicknesses may be less than desired, as determined by inspections that were anticipated to be done during RF-13 and which have now been completed. It was explained in the "ULNRC-04875, Request for Relief from ASME Section XI Requirements in Order to Restore Wall Thickness of ASME Class 2 Carbon Steel Main [[system" contains a listed "[" character as part of the property label and has therefore been classified as invalid. Piping by Weld Overlay Reinforcement|July 22, 2003 letter]] that since the potentially affected pipe sections are to be replaced during Callaway's 14th refueling outage (RF-14, scheduled for Fall 2005) due to planned ACO a subsidiary ofAmeren Corporation

ULNRC-04993 May 7, 2004 Page 2 replacement of the steam generators in that refueling outage, application of any needed weld overlays in RF-13 would restore pipe wall thicknesses to ensure more than adequate margin for the period of plant operation between RF-13 and RF-14.

This would preclude the possibility of having to replace the affected piping sections twice in consecutive outages (i.e., once in RF-13 and then again in RF-14). The service life of the weld overlay(s) permitted by the relief request was thus requested (and approved) to be one operating cycle.

It may now be reported that with the recent completion of the feedwater piping inspections during the current refueling outage (RF-13), none of the pipe sections identified in AmerenUE's approved relief request has been identified as requiring weld overlay. That is, the inspections confirmed that the existing pipe wall thicknesses and pipe wall thinning rates are such that adequate margin to design minimum wall thickness exists for all of the identified pipe sections until replacement in RF-14. However, the inspections did reveal greater-than-expected pipe wall thinning in one pipe section not identified in AmerenUE's relief request, and it has been determined that this particular pipe section should receive weld overlay reinforcement.

As noted previously, all of the pipe sections identified in AmerenUE's approved relief request are associated with the main feedwater system at Callaway.

The pipe section identified for weld overlay is at a 900 elbow upstream from the 450 elbow identified as one of the pipe sections in the relief request. Pipe wall thinning was confirmed in an upstream area of the 900 elbow. This pipe section was not previously identified as one particularly susceptible to pipe wall thinning, and so it was not included in the list of affected pipe sections in AmerenUE's relief request.

Nevertheless, the section was still subject to inspection under the FAC program, and results from that inspection have confirmed the need for overlay reinforcement based on the approach that was to be taken for the other identified pipe sections. It is important to note the justification for weld overlay reinforcement that was provided for the identified pipe sections in the approved relief request applies to this pipe section as well. That is, weld overlay reinforcement will restore the wall thickness of the piping to a value greater than design minimum wall thickness with adequate margin, taking into account the determined wear rate, for a service life of one operating cycle. Overlay reinforcement of this pipe section will thus ensure a sufficient level of safety and provide adequate structural integrity for one operating cycle.

Based on the above, AmerenUE is submitting for NRC review and approval a revision of the subject weld-overlay relief request to incorporate the additional, identified pipe section. The revised relief request is attached. Revision bars have been applied to indicate the changes made to the relief request.

ULNRC-04993 May 7, 2004 Page 3 AmerenUE intends to apply the weld overlay to the newly identified pipe section during the current/ongoing refueling outage. Therefore, AmerenUE respectfully requests NRC approval of the revised relief request as soon as possible.

It should be noted that, with regard to plant restart from the current outage, entry into plant heat-up conditions is currently projected to occur during the weekend of May 22. NRC approval is therefore requested on or by Friday, May 21, in anticipation of plant heat-up.

Please contact me at 573-676-8659 or Dave Shafer at 314-554-3104 for any questions you may regarding the revised relief request.

Sincerely, Keith D. Yo g Manager, Regulatory Affairs TBE/jdg Enclosure

ULNRC-04993 May 7, 2004 Page 4 cc:

U.S. Nuclear Regulatory Commission (Original and 1 copy)

Attn: Document Control Desk Mail Stop P1-137 Washington, DC 20555-0001 Mr. Bruce S. Mallett Regional Administrator U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-4005 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. Jack N. Donohew (2 copies)

Licensing Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 7E1 Washington, DC 20555-2738 Missouri Public Service Commission Governor Office Building 200 Madison Street PO Box 360 Jefferson City, MO 65102-0360

ULNRC-04993 Attachmcnt Pagc I of 7 Request to Restore Wall Thickness of ASME Class 2 Carbon Steel Main Feedwater Piping by Weld Overlay Reinforcement

Background

As an alternative to piping replacement in accordance with ASME Section Xl IWC-4000, and pursuant to the provisions of 10CFR 50.55a(a)(3)(i), Callaway Plant requests permission to restore the wall thickness of high energy ASME Class 2 feedwater piping by weld overlay.

Requested service life of the weld overlay reinforcement is one operating cycle from Refuel 13 to Refuel 14. Piping reinforced by weld overlay will be cut out and replaced during installation of new steam generators in Refuel 14.

The 1989 Edition with no Addenda of ASME Section Xl currently governs repair/replacement activities at the Callaway Nuclear Plant. Callaway Plant is currently in the second 10-year inservice inspection interval, which began on August 1, 1995. The 1974 Edition with Summer 1975 Addenda of ASME Section III is the Construction Code for the main feedwater piping system.

Areas Identified that May Require Weld Overlay Reinforcement The Callaway Flow Accelerated Corrosion (FAC) program is used to monitor and evaluate the remaining life of ASME Class 2 feedwater piping at the Callaway plant. Evaluation and ultrasonic wall thickness examinations have revealed a small number of locations where repair and/or piping replacement will be necessary in the future. Table 1 lists feedwater piping areas where repair by overlay reinforcement is requested. The piping/part description, Callaway location identifier, nominal pipe size, pipe schedule, and base material type are listed for each location.

Table 2 provides wall thickness data for these locations. The design minimum wall thickness, measured wall thickness, projected wall thickness, and expected margin are provided for each location. The maximum projected axial length requiring overlay reinforcement (L dimension in Figure 1) is expected to be 8 inches or less.

Justification for Weld Overlay Reinforcement Projections based on calculated wear rates and ultrasonic examination data obtained during Refuel 11 and Refuel 12 indicate weld overlay reinforcement may be necessary to maintain the required structural integrity until Refuel 14 when new steam generators will be installed. Piping reinforced by weld overlay will be cut out and replaced during installation of the new steam generators.

The piping areas that may require weld overlay reinforcement are relatively small localized areas.

Adjacent areas have been inspected and verified to have wall thickness that meets design requirements. Weld overlay reinforcement will restore wall thickness of the piping to a value greater than or equal to design minimum wall thickness with adequate margin, considering predicted wear rates, to provide a service life of one operating cycle. In addition, the weld overlay material is not predicted to become exposed to feedwater during the cycle. The weld overlay will have a uniform width and extend 360 degrees circumferentially around the piping. The proposed overlay reinforcement will ensure a sufficient level of safety and provide adequate structural integrity for one operating cycle.

The weld overlay reinforcement alternative will result in a significant reduction in personnel radiation exposure during refueling outage maintenance work. In addition, by avoiding replacement of the piping during Refuel 13 and again in Refuel 14, outage duration and costs are reduced by decreasing the overall scope of work.

ULNRC-04993 Attachmcnt Pagc 2 of 7 Requirements for Restoration of Internal Wall Thinning by Weld Overlay Weld overlay reinforcement on the outside surface of the piping shall be installed in accordance with the following requirements and rules:

1. General Requirements 1.1. The weld overlay(s) installed to restore wall thickness shall be performed in accordance with the Callaway Repair/Replacement Program '.

1.2. The wall thickness restoration shall meet all requirements of the Callaway Repair/Replacement Program except as permitted in this relief request.

2. Initial Evaluation 2.1. The piping base material where the weld overlay is to be installed shall be evaluated to establish the existing average wall thickness and the extent and configuration of degradation to be reinforced by the weld overlay.

2.2. Areas of piping, parts, or components, adjacent to the identified overlay area shall be examined to verify that the entire defect area will be encompassed as necessary by the weld overlay and to validate any design assumptions relative to the structural integrity of the piping.

3. Weld Overlay Design 3.1. The thickness of the weld overlay reinforcement shall not exceed 1/4 inch. See thickness dimension Win Figure 1.

3.2. Evaluation of areas that require restoration by weld overlay shall consider the design life of the piping, future internal wall thinning in the weld overlay area, and shall be based on the design thickness as prescribed by ASME Section III 2.

3.3. The weld overlay shall have a uniform width and extend 360 degrees circumferentially around the piping.

3.4. Unless otherwise established by design analysis, the weld overlay shall extend axially a distance of at least s in each direction beyond the area that requires restoration, where s is defined as:

R = average outer radius of the component tnom = nominal wall thickness of the component 3.5. Edges of the weld overlay shall be tapered to the existing piping surface to a maximum angle of 45°. See angle a shown in Figure 1.

3.6. Final configuration of the weld overlay reinforcement shall permit nondestructive examination as required in 5.1 and 5.2.

3.7. Except for the tapered edges, the weld overlay reinforcement shall have a uniform thickness.

3.8. Tensile strength of the weld filler metal used for the overlay shall be at least that specified for the piping base material.

The Callaway RepairlReplacement Program is In accordance with the 1989 Edition of ASME Section Xi.

2 ASME Section III, 1974 with Summer 1975 Addenda is the Construction Code for the feedwater system.

ULNRC-04993 Attachment Page 3 of 7 3.9. Design shall be in accordance with ASME Section III 3 and shall consider the weld overlay as an integral portion of the piping upon which it is applied (not as a weld).

3.10. The allowable stress values of the base metal shall apply to the design of the deposited weld metal.

3.11. The following factors shall be considered in design of the weld overlay reinforcement:

3.11.1. The effects on the piping system of radial and longitudinal shrinkage caused by application of the overlay; 3.11.2. The effects on flexibility, stress concentration, and section properties of the added section thickness; 3.11.3. Stress concentrations resulting from existing and predicted piping internal surface configuration; 3.11.4. The effects of different coefficients of thermal expansion between the weld overlay filler metal and the base metal.

3.12. The effect of the weld overlay shall be reconciled with the original flexibility analysis required by ASME Section Ill 3. Unless a lower stress intensification factor (SIF or i) is established, an SIF(i) of 2.1 shall be applied for overlays on straight pipe and adjacent welds; a stress multiplier of 1.7 shall be applied to the SIF(i) for standard elbows; and an SIF(i) of 2.1 shall be applied for tees and branch connections when the toe of the overlay is not less than 2.5VRt,,0 from any branch reinforcement.

4. Installation 4.1. The entire surface area to which the weld overlay is to be installed shall be examined using either the liquid penetrant (PT) or magnetic particle (MT) test method. Acceptance criteria shall be in accordance with NC-2500/5300 3 for the specific product form that was examined (e.g., base material or weld metal).

4.2. The weld overlay reinforcement shall be installed in accordance with the Callaway Repair/Replacement Program.

4.3. The overlay weld metal shall be installed using a groove weld procedure qualified in accordance with ASME Section IX and Section III 4.4. The surface of the final overlay reinforcement shall be prepared by machining or grinding as necessary to permit performance of surface and wall thickness examination.

5. Examination 5.1. The completed weld overlay reinforcement shall be examined using liquid penetrant (PT) or magnetic particle (MT) test method. The acceptance criteria shall be in accordance with ASME Section III, NC-5300 3.

5.2. The weld overlay reinforcement and the base material below the reinforcement shall be examined by ultrasonic examination to verify acceptable wall thickness.

6. Documentation Use of this relief request shall be documented as specified in the Callaway Repair/Replacement Program.

ASME Section 1I1, 1974 with Summer 1975 Addenda

ULNRC-04993 Attachment Pagc 4 of 7 Table 1: Feedwater Piping Areas That May Require Weld Overlay Reinforcement Area Description FAC ID No. 1 &2 NPS3 Sch.

Mat.

Downstream area of A SIG 14" by 16" expander AE04-DE7E 16 80 CS Downstream area of C SIG 14" by 16" expander AEO5-B5E 16 80 CS Downstream area of D S/G 14" by 16" expander AE05-CD7E 16 80 CS Upstream area of 450 elbow upstream of AEV01 22 AE05-E645 14 80 CS Upstream area of 900 elbow downstream of AEV0123 AE05-AB590 14 80 CS Midspan area of A SIG 5D bend AE04-E890 14 80 CS Midspan area of B S/G 5D bend AE04-C4590 14 80 CS Midspan area of C S/G 5D bend AE05-B590 14 80 CS Midspan area of D SIG 5D bend AE05-D890 14 80 CS Upstream area of 900 elbow upstream of AEV0122 AEO5-E690 14 80 CS Notes:

1. Listed FAC ID Numbers are those currently identified in the Callaway FAC Program.

2.

Figures 2 and 3 show location of areas by FAC ID No.

3.

NPS is pipe size of area for weld overlay reinforcement.

Table 2: Feedwater Piping Wall Thickness Data' Design 2 Wear Rate RF11 3 RF12 3 RF13 4 RF14 4 FAC ID No.

Location M in (mils/yr) measured measured projected margin projected margin AEO4-DE7E Upstream 0.489 8.203 0.549 0.514 0.502 0.013 0.490 0.001 AEo4-DE7E Downstream 0.680 7.590 0.687 0.687 0.676

-0.004 0.665

-0.015 AEO4-E890 General 0.614 11.122 0.700 0.676 0.659 0.045 0.642 0.028 AEO4-C4590 General 0.643 8.347 0.671 0.684 0.671 0.028 0.658 0.015 AE05-B5E Upstream 0.489 9.421 0.544 0.519 0.505 0.016 0.491 0.002 AE05-B5E Downstream 0.559 8.513 0.649 0.644 0.631 0.072 0.618 0.059 AE05-B590 General 0.643 12.603 0.650 0.663 0.644 0.001 0.625 0.018 AE05-AB590 General 0.489 12.522 0.535 0.510 0.491 0.002 0.472

-0.017 AE05-CD7E Upstream 0.489 8.185 0.609 0.603 0.591 0.102 0.579 0.090 AEO5-CD7E Downstream 0.680 7.434 0.693 0.685 0.674

-0.006 0.663 0.017 AEo5-D890 General 0.614 10.950 0.655 0.649 0.633 0.019 0.617 0.003 AEo5-E645 General 0.489 9.776 0.535 0.516 0.501 0.012 0.486 4.003 AEo5-E690 General 0.403 44.000 5 0.577 no data 0.4596 0.056 0.393

.0.010 Notes:

1.

Wall thickness values are in inches.

2.

General design minimum wall was determined by analysis at each location. Structural integrity was verified by additional detailed analysis at specific locations where the measured wall thickness encroached on general design minimum wag thickness.

3.

Anomalous UT readings are attributed to changes in inspection personnel and test equipment and are considered within acceptable tolerances. These variances do not adversely impact the model for calculating projected wear.

4. Projected wall thickness is based on average wear rates determined by the Callaway FAC program.

Wall thickness margin is the difference between the projected thickness and the design minimum.

5.

This wear rate is based on the difference of minimum measured wag thickness from Refuel 11 and Refuel 13 divided by the operating time. This results in a highly conservative wear rate estimate.

6.

Measured wall thickness taken during Refuel 13.

ULNRC-04993 Attachment Pagc 5 of 7 Ft 9-X X

lingt of branch Xmin

-reinforcenient L =Axial lidits qfarea requiring restoration Figure 1: Schematic of Overlay Configuration and Branch Reinforcement.

l.04 NO4 lSIElCN l0 0ATEUCASLF PUW 0l44 AtDI cSTO OL.

0.4c44-U 4014 CTOS F=OY

-AC OTE 2.00.

-004704T)

OT -

UE CUAC 05ES OUST 0. U COOROITJO407 MT A0444TOA 144440N 0

1 5251 -B4 0V22 DETAIL 4

100_

"R

'oc 7t.e 0

&4R4 TG ok402 NOTE:00OT OO -00 SKt< 1 la4UOD 40-fL N

E.

CO 4 AO DE.OLO Wt0400 0TING00U550 EDI0IS)UTJU A mOLOT,ONTU 04 04USTIEO4)L4T

,4m100, 000440004h 5S5SPOOLER NOI 0 041 5oT TO TZ UTTOISHE 00 25244teroM. 004504)C004.0,0440 e.4 2Qe04.

24QTTTNTT TR-T-T XSTNTT2405A0T2N.OSL r TOTO 54244 c4 A)L02COW~

CT2CEN'SNT4TSRT

&T2EOT PONQTRTIOT)4 10.0.20.10,

?,4211

0) )).

E

.04.4 ST0 b5OW 400T25021)

E^A914 40 OE 14 444 CAL40 TOTS TO) 0~l 00400014T IS OCT

/00 2200SS 4 T,.t45N).)T0.BIOT4T422S OTUTLT~

0024 0)" _.

0 4.

I.

Areas identified for potential weld overlay reinforcement are flagged DETAIL' kc-,

REACTOR AUXILIARY BUILDING B UILDING

)4.TFSTj 20 I2)A 14 ~ ~

t s

1211 22.124 40 $4 (0-0 I N S N U N

E R 424t DETAIL 4

(PLAI ~

ULNRC-04993 Attachmenl Page 6 of 7 5

I I

I

-I 1

f, R

7 I

It q

I I

l I

I -

I (0) 903V2Z-V VALVE INFORMATION TABLE SD lN vET.

IiM ACToR AUXILIARY uR UILDING JOLDNE

.1 4

T0.0 riL C.

f.n NOTES t4 4<.-E^

ZCL 10

-N l:.I K-1rIna:~o*svzl WF 0iffC.MI 41 ASA_*.

n~t

= M

,-a.-.4 DETAIL (

soon s-conc.,.Sr DETAIL

-n.0,0 CLIS614004.

1 O W.)

(UN l9 0!1 2* *.0s I/ PLAN

\\/

-4+

ASo WzSAQCA bvI P110r 2 d

A

• monlol m

mcon-it N

/)a?

Areas identifie for potential weldN OVALV CLASS0 r.1 0.35 LOWOT I 0 DETAIL4 jCTEL Pag 7

f A

PIING S

SAI SOME

.MJOII

\\

.~AS-BUILT l

'Figure 3: Drawing M-23AE05 Main Feedwaterl l1-04SD5 lM-23AEOS(0 1

I5..

Et1 H

C F

E D

B 8

7 16 S

4 4

l