L-2002-044, Resubmittal of Code Relief Requests Nos. 30 & 31, Relief Request No. 30 Revised to Remove Reference to ASME Section IX, Paragraph QW-424

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Resubmittal of Code Relief Requests Nos. 30 & 31, Relief Request No. 30 Revised to Remove Reference to ASME Section IX, Paragraph QW-424
ML020700270
Person / Time
Site: Turkey Point  NextEra Energy icon.png
Issue date: 03/01/2002
From: Mcelwain J
Florida Power & Light Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2002-044
Download: ML020700270 (36)
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Text

0 =Pl.

A 0 1 2002 L-2002-044 10 CFR 50.55a U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Re: Turkey Point Units 3 and 4 Docket Nos. 50-250 and 251 ASME Section Xl Relief Request Nos. 30-31, Associated With Reactor Vessel Closure Head Repair Florida Power & Light Company (FPL) submitted Relief Requests 30 and 31 via letter L-2002-023, dated February 4, 2002. This letter supercedes L-2002-023 in its entirety. Relief Request #30 has been revised to remove reference to ASME Section IX, Paragraph QW-424.

FPL requests approval of Relief Request 30 pursuant to 10 CFR 50.55a (a)(3), and approval of Relief Request 31 pursuant to 10 CFR 50.55a (g)(5)(iii). For Relief Request 30, FPL has determined that, pursuant to 10 CFR 50.55a (a)(3)(i), the proposed alternatives would provide an acceptable level of quality and safety. For Relief Request 31, FPL has determined that, pursuant to 10 CFR 50.55a (g)(5)(iii), it would be impractical to characterize the flaws by non-destructive examination (NDE) and it would be impractical to show that the flaws do not extend into the ferritic base material.

Relief Requests 30 and 31 are needed to support potential corrective actions resulting from the NRC Bulletin 2001-01 inspections scheduled to be performed during the Turkey Point Unit 4 spring 2002 refueling outage. We request approval of these reliefs as soon as practical to support the upcoming outage scheduled to begin on March 23, 2002.

Additionally, we are advising that Relief Request 28, submitted via FPL letter L-2001-214 on September 24, 2001, and approved by the NRC on October 5, 2001, will not be implemented.

Instead, the attached Relief Request 30 will be used if needed. FPL also submitted Relief Request 29 via letter L-2001-214, and provided supplemental information in letter L-2001-223 dated October 7, 2001. Relief Request 29 is hereby withdrawn.

Please contact John Manso at (305) 246-6622, if there are any questions about this submittal.

Very truly yours,

, ohn P. McEllwain Vice President Turkey Point Plant CLM Attachments NRC Regulatory Issue Summary 2001-05 waived the requirements that multiple copies of documents be submitted to the NRC.

an FPL Group company

L-2002-044 10 CFR 50.55a U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Re: Turkey Point Units 3 and 4 Docket Nos. 50-250 and 251 ASME Section XI Relief Request Nos. 30-31, Associated With Reactor Vessel Closure Head Repair Florida Power & Light Company (FPL) submitted Relief Requests 30 and 31 via letter L-2002-023, dated February 4, 2002. This letter supercedes L-2002-023 in its entirety. Relief Request #30 has been revised to remove reference to ASME Section IX, Paragraph QW-424.

FPL requests approval of Relief Request 30 pursuant to 10 CFR 50.55a (a)(3), and approval of Relief Request 31 pursuant to 10 CFR 50.55a (g)(5)(iii). For Relief Request 30, FPL has determined that, pursuant to 10 CFR 50.55a (a)(3)(i), the proposed alternatives would provide an acceptable level of quality and safety. For Relief Request 31, FPL has determined that, pursuant to 10 CFR 50.55a (g)(5)(iii), it would be impractical to characterize the flaws by non-destructive examination (NDE) and it would be impractical to show that the flaws do not extend into the ferritic base material.

Relief Requests 30 and 31 are needed to support potential corrective actions resulting from the NRC Bulletin 2001-01 inspections scheduled to be performed during the Turkey Point Unit 4 spring 2002 refueling outage. We request approval of these reliefs as soon as practical to support the upcoming outage scheduled to begin on March 23, 2002.

Additionally, we are advising that Relief Request 28, submitted via FPL letter L-2001-214 on September 24, 2001, and approved by the NRC on October 5, 2001, will not be implemented.

Instead, the attached Relief Request 30 will be used if needed. FPL also submitted Relief Request 29 via letter L-2001-214, and provided supplemental information in letter L-2001-223 dated October 7, 2001. Relief Request 29 is hereby withdrawn.

Please contact John Manso at (305) 246-6622, if there are any questions about this submittal.

Very truly yours,

?hP.McElwain Vice President Turkey Point Plant CLM Attachments NRC Regulatory Issue Summary 2001-05 waived the requirements that multiple copies of documents be submitted to the NRC.

L-2002-044 Attachment 1 Page 1 of 26 TURKEY POINT UNIT 3 AND UNIT 4 RELIEF REQUEST NO. 30 "REPAIR OF REACTOR VESSEL CLOSURE HEAD PENETRATION WELDS" COMPONENT IDENTIFICATION:

Turkey Point (PTN) Unit 3 and Unit 4 Reactor Vessel Closure Head CRDM Nozzle Penetrations, Class 1 FPL Drawing No. 5610-M-400-57 Rev. 1 CODE REQUIREMENT:

ASME Section XI, paragraph IWA-4120, stipulates the following: "Repairs shall be performed in accordance with the Owner's Design Specification and the original Construction Code of the component or system. Later Editions and Addenda of the Construction Code or of Section III, either in their entirety or portions thereof, and Code Cases may be used."

II1. RELIEF REQUESTED:

Pursuant to 10 CFR 50.55a (a)(3)(i), relief is requested to utilize alternative welding requirements than contained in the Construction Code of Record. The alternative requirements provide an acceptable level of quality and safety.

The Construction Code of record for the Turkey Point Unit 3 and Unit 4 reactor pressure vessel closure (RPV) head is the 1965 Edition of the ASME Boiler and Pressure Vessel Code, Section II1.

For the contemplated repairs to the RPV head Control Rod Drive Mechanism (CRDM) nozzle penetrations, the Construction Code requires repairs to be post weld heat treated (PWHT) in accordance with the Code requirements. The PWHT requirements set forth therein would be extremely impractical to attain on a RPV head in containment without distortion of the head. In addition, the existing penetration to head welds were not qualified with PWHT and cannot be so qualified at this time.

The proposed repairs will be conducted in accordance with the 1989 Edition, no Addenda, of Section III Subsection NB, and alternative requirements discussed below.

L-2002-044 Attachment 1 Page 2 of 26 FPL is proposing to sever the weld joining a leaking CRDM nozzle penetration to the head and make a new weld, in accordance with the requirements of ASME Section III, at a slightly removed location, to rejoin the CRDM nozzle penetration to the head. The welding will be performed with a remotely operated weld tool, utilizing the machine Gas Tungsten-Arc Welding (GTAW) process and the ambient temperature temper bead method with 50 degree F minimum preheat temperature and no post weld heat treatment.

Relief is specifically requested from the following Code requirements:

  • NB-4622.1 and NB-4622.5 require post weld heat treatment. However, FPL proposes to use a temper bead welding technique using ambient preheat and no post weld heat treatment.

e NB-5245 requires a progressive surface examination (PT or MT) at the lesser of 1/2 the maximum weld thickness or 1/2-inch, as well as a surface examination on the finished weld. FPL proposes a liquid penetrant examination only on the final weld surface and ultrasonic examination no sooner than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the weld has cooled to ambient temperature.

  • NB-61 11 requires a hydrostatic test. FPL proposes a system leakage test.

IV. WELD REPAIR METHOD:

FPL plans to replace the CRDM nozzle penetration weld by welding the CRDM nozzle (P-No. 43 base metal) to the RPV head (P-No.3 base metal) with filler metal (F-No. 43), at a slightly higher location, in accordance with the following:

e General Requirements:

The maximum area of an individual weld based on the finished surface will be less than 100 square inches, and the depth of the weld will not be greater than one-half of the ferritic base metal thickness.

If a defect penetrates into the ferritic base metal, repair of the base metal, using a nonferritic weld filler metal, may be performed provided the depth of repair in the base metal does not exceed 3/8 inch.

Prior to welding, the area to be welded and a band around the area of a least 11/2 times the component thickness (or 5 inches, whichever is less) will be at least 50 degrees F.

L-2002-044 Attachment 1 Page 3 of 26 Welding materials will meet the requirements of the design specification, construction code and Code Cases specified in the repair program. Welding materials will be controlled so that they are identified as acceptable until consumed.

Peening will not be used; however, the weldment final surface will be abrasive water jet conditioned to impart a compressive stress layer to produce resistance to PWSCC.

  • Welding Qualifications:

The welding procedures and the welding operators shall be qualified in accordance with ASME Section IX and the requirements of the following paragraphs.

  • Procedure Qualification:

The base metals for the welding procedure qualification will be of the same P Number and Group Number as the metals to be welded. The metals shall be post weld heat treated to at least the time and temperature that was applied to the metals being welded.

The root width and included angle of the cavity in the test assembly will be no greater than the minimum specified for the proposed new weld.

The maximum interpass temperature for the first three layers of the test assembly will be 150 degrees F.

The test assembly cavity depth will be at least one-half the depth of the weld to be installed during the repair activity and at least 1 inch. The test assembly thickness will be at least twice the test assembly cavity depth. The test assembly will be large enough to permit removal of the required test specimens. The test assembly dimensions surrounding the cavity will be at least the test assembly thickness and at least 6 inches. The qualification test plate will be prepared in accordance with Figure 1.

Ferritic base metal for the procedure qualification test will meet the impact test requirements at or below the lowest service temperature.

Charpy V-notch tests of the ferritic heat-affected zone (HAZ) will be performed at the same temperature as the base metal test above. The number, location, and orientation of test specimens will be as follows:

The specimens will be removed from a location as near as practical to a depth of

L-2002-044 Attachment 1 Page 4 of 26 one-half the thickness of the deposited weld metal. The test coupons for HAZ impact specimens will be taken transverse to the axis of the weld and etched to define the HAZ. The notch of the Charpy V-notch specimens will be cut approximately normal to the metal surface in such a manner as to include as much HAZ as possible in the resulting fracture. When the metal thickness permits, the axis of a specimen will be inclined to allow the root of the notch to be aligned parallel to the fusion line.

If the test metal is in the form of a plate or a forging, the axis of the weld will be oriented parallel to the principal direction of rolling or forging.

The Charpy V-notch test will be performed in accordance with SA-370.

Specimens will be in accordance with SA-370, Figure 11, Type A. The test will consist of a set of three full-sized 10 mm x 10 mm specimens. The lateral expansion, percent shear, absorbed energy, test temperature, orientation and location of all test specimens will be reported in the Procedure Qualification Record.

The average values of the three HAZ impact tests will be equal to or greater than the average values of the three unaffected base metal tests.

e Performance Qualification:

Welding operators will be qualified in accordance with ASME Section IX.

  • Welding Procedure Requirements:

The weld metal will be deposited by machine GTAW process.

The dissimilar metal weld shall be made using F-No. 43 weld metal (QW-432) for P-No. 43 to P-No. 3 weld joints.

The area to be welded will be buttered with a deposit of at least three layers to achieve at least 1/8 inch overlay thickness as shown in Figure 2, steps 1 through 3. The heat input for each layer will be controlled to within +/-10% of that used in the procedure qualification test. Particular care will be taken in placement of the weld beads on the ferritic metal to ensure that the HAZ (ferritic base metal) is tempered. Subsequent layers will be deposited with a heat input not exceeding that used for layers beyond the third layer in the procedure qualification.

The maximum interpass temperature for field applications will be 350 degrees F regardless of the interpass temperature during qualification. The new weld is inaccessible for mounting thermocouples near the weld; therefore, recording instruments will not be used to monitor interpass temperature.

L-2002-044 Attachment 1 Page 5 of 26

  • Examination:

Prior to welding, a liquid penetrant surface examination will be performed on the area to be welded; coverage is shown in Figure 5.

The final weld surface and a surrounding band will be examined using liquid penetrant (PT) and ultrasonic (UT) methods when the completed weld has been at ambient temperature for at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

PT coverage is shown in Figure 6.

UT will be performed scanning from the ID surface of the weld, excluding the transition taper portion at the bottom of the weld, and adjacent portion of the CRDM nozzle bore. The UT is qualified to detect flaws in the weld and base metal interface in the weld region, to the maximum practical extent. The examination extent is consistent with the Construction Code requirements. UT coverage is shown in Figures 8 through 12.

NDE personnel will be qualified in accordance with NB-5500 Liquid penetrant examination acceptance criteria will be in accordance with NB 5350. Ultrasonic examination acceptance criteria will be in accordance with NB 5330.

  • Documentation:

The repair will be documented on Form NIS-2.

V. JUSTIFICATION FOR USE OF ALTERNATIVE:

This proposed alternative temper bead welding process provides an equivalent acceptable level of quality and safety to the welding process requiring post weld heat treatment described in ASME,Section III Subsection NB 1989 Edition, no Addenda. The repair process, technical justification, and occupational exposure savings are described below:

Repair Process:

Visual inspections for leakage/boric acid deposits of CRDM nozzle penetrations will be conducted during the Spring 2002 Refueling Outage for Unit 4.

CRDM nozzles that are determined to have through-wall leakage, will be repaired/modified. The CRDM nozzle repair configuration is illustrated in Figures 3 and 4. The new weld is designed and sized as a coaxial cylinder nozzle weld,

L-2002-044 Attachment 1 Page 6 of 26 see Figure 4. The new weld attachment length to the closure head base metal is greater than 1.25 x the CRDM nozzle wall thickness. Also the new weld attachment length from the upper edge of the weld prep bevel on the CRDM nozzle to the bottom toe of the weld is greater than 1.25 x the CRDM nozzle wall thickness. Furthermore the new weld extends across the full wall thickness of the CRDM nozzle.

Remotely controlled machine processes, to the extent practical, are planned for all examination, metal removal and welding.

Nondestructive examinations utilizing ultrasonic methods are planned for the base metal of the CRDM nozzles determined to have through-wall leakage.

The lower portion of the thermal sleeves will be removed by remotely operated methods to the extent practical.

Using a remote tool from below the RPV head, each of the leaking CRDM nozzles will first receive a roll expansion into the RPV head base metal to insure that the nozzle will not move during the welding operations.

A semi-automated machining tool operating underneath the RPV head will remove the entire lower portion of the CRDM nozzle to a location above the existing J-groove partial penetration weld. The machine tool will also form the CRDM nozzle weld preparation. The operation will sever the existing J-groove partial penetration weld from the subject CRDM nozzles.

The machined surface will be cleaned prior to liquid penetrant examination (PT).

The repair will establish a new pressure boundary weld between the shortened CRDM nozzle and the inside bore of the RPV head. Welding will be performed with a remotely operated machine GTAW weld head using the temper bead process. Minimum preheat temperature will be 50 degrees F and the welding filler metal will be ERNiCrFe-7 (Alloy 52).

Preheat temperature will be monitored using contact pyrometers and/or thermocouple(s) on accessible portions of the closure head external surface(s).

The closure head preheat temperature will be essentially the same as the reactor building ambient temperature which exceeds 50 degrees F; therefore RPV head preheat temperature monitoring in the weld region is unnecessary.

The final weld face, not including the taper transition, will be machined and/or ground.

The final weld will be liquid penetrant and ultrasonically examined prior to

L-2002-044 Attachment 1 Page 7 of 26 subsequent abrasive water-jet conditioning.

The final inside diameter surface of the CRDM nozzle near the new weld and the new weld will then be conditioned by abrasive water-jet machining to produce a final surface that is in compression to produce optimum resistance to primary water stress corrosion cracking. The replacement lower portion of the thermal sleeve will be re-installed.

A system leakage test will be performed.

Technical Justification:

  • Relief from NB-4622.1 and NB-4622.5 Quality temper bead welds, without preheat and postheat, can be made based on welding procedure qualification test data derived from machine GTAW ambient temperature temper bead welding process. The proposed alternative welding technique has been demonstrated as an acceptable method for performing welds without preheat and post heat. The ambient temperature temper bead technique has been approved by the NRC as having an acceptable level of quality and safety and was successfully used at several sites (Duane Arnold, Nine Mile Point, Fitzpatrick, Crystal River, and Three Mile Island Unit 1).

Results of procedure qualification work undertaken to date indicate that the process produces sound and tough welds. For instance, typical tensile test results have been ductile breaks in the weld metal.

As shown below, the Framatome Procedure Qualification Record (FRA-ANP PQR 7164) using P-No. 3, Group No. 3 base metal exhibited improved Charpy V-notch properties in the HAZ from both absorbed energy and lateral expansion perspectives as compared to the unaffected base metal.

L-2002-044 Attachment 1 Page 8 of 26 PQR 7164 Unaffected Base HAZ Metal 50°F absorbed energy (ft-lbs) 69, 55, 77 109, 98, 141 50°F lateral expansion (mils) 50, 39, 51 59, 50, 56 50OF shear fracture (%) 30, 25, 30 40, 40, 65.

80°F absorbed energy (ft-lbs) 78, 83, 89 189, 165,127 80°F lateral expansion (mils) 55, 55, 63 75, 69, 60 80°F shear fracture (%) 35, 35, 55 100, 90, 80 The absorbed energy, lateral expansion, and percent shear were significantly greater for the HAZ than the unaffected base metal at both test temperatures. It is clear from these results that the GTAW temper bead process has the capability of producing acceptable welds.

The use of a GTAW temper bead welding technique to avoid the need for postweld heat treatment is based on research that has been performed by EPRI and other organizations. (Reference EPRI Report GC-1 11050, "Ambient Temperature Preheat for Machine GTAW Temper bead Applications," dated November 1998.) The research demonstrates that carefully controlled heat input and bead placement allow subsequent welding passes to relieve stress and temper the heat affected zones of the base metal and preceding weld passes.

Data presented in Tables 4-1 and 4-2 of the report show the results of procedure qualifications performed with 300 degrees F preheats and 500 degrees F post heats, as well as with no preheat and post-heat. From that data, it is clear that equivalent toughness is achieved in base metal and heat affected zones in both cases. The temper bead process has been shown effective by research, by successful procedure qualifications, and by many successful repairs performed since the technique was developed. Many acceptable Procedure Qualifications Records (PQR's) and Welding Procedure Specifications (WPS's) presently exist and have been used to perform numerous successful repairs. These repairs have included all of the Construction Book Sections of the ASME Code, as well as the National Board Inspection Code (NBIC). The use of the automatic or machine GTAW process utilized for temper bead welding allows more precise control of heat input, bead placement, and bead size and contour than the manual shielded metal arc welding (SMAW) process required by NB-4622. The very precise control over these factors afforded by the alternative provides more effective tempering and eliminates the need to grind or machine the first layer of the repair.

L-2002-044 Attachment 1 Page 9 of 26 The NB-4622.11 temper bead procedure requires a 350 degrees F preheat and a postweld soak at 450-550 degrees F for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> for P-No. 3 metals. Typically, these kinds of restrictions are used to mitigate the effects of the solution of atomic hydrogen in ferritic metals prone to hydrogen embrittlement cracking.

The susceptibility of ferritic steels is directly related to their ability to transform to martensite without appropriate heat treatment. The P-No. 3 base metal of the reactor vessel head is able to produce martensite from the heating and cooling cycles associated with welding. However, the proposed alternative mitigates this propensity without the use of elevated preheat and postweld hydrogen bake out.

The NB-4622.11 temper bead procedure requires the use of the SMAW welding process with covered electrodes. Even the low hydrogen electrodes, which are required by NB-4622, may be a source of hydrogen unless very stringent electrode baking and storage procedures are followed. The only shielding of the molten weld puddle and surrounding metal from moisture in the atmosphere (a source of hydrogen) is the evolution of gases from the flux and the slag that forms from the flux and covers the molten weld metal. As a consequence of the possibility for contamination of the weld with hydrogen, NB-4622 temper bead procedures require preheat and postweld hydrogen bake-out. However, the proposed alternative temper bead procedure utilizes a welding process that is inherently free of hydrogen. The GTAW process relies on bare welding electrodes with no flux to trap moisture. An inert gas blanket positively shields the weld and surrounding metal from the atmosphere and moisture it may contain. To further reduce the likelihood of any hydrogen evolution or absorption, the alternative procedure requires particular care to ensure the weld region is free of all sources of hydrogen. The GTAW process will be shielded with welding grade argon that typically produces porosity free welds. A typical argon flow rate would be about 15 to 50 CFH and would be adjusted to assure adequate shielding of the weld without creating a venturi affect that might draw oxygen or water vapor from the ambient atmosphere into the weld. Additionally, the F-No. 43 (ERNiCrFe-7) filler metal to be used for the repairs is not subject to hydrogen embrittlement cracking.

In lieu of using thermocouples for interpass temperature measurements, calculations show that the maximum interpass temperature will never be exceeded based on a maximum allowable low welding heat input, weld bead placement, travel speed, and conservative preheat temperature assumptions.

The calculation supports the conclusion that using the maximum heat input through the third layer of the weld, the interpass temperature returns to near ambient temperature. Heat input beyond the third layer will not have a metallurgical effect on the low alloy steel HAZ.

L-2002-044 Attachment 1 Page 10 of 26 The calculation is based on a typical inter-bead time interval of five minutes. The five minute inter-bead interval is based on the time required: 1) to explore the previous weld deposit with the two remote cameras housed in the weld head,

2) to shift the starting location of the next weld bead circumferentially away from the end of the previous weld-bead, and 3) to shift the starting location of the next bead axially to insure a 50% weld bead overlap required to properly execute the temper bead technique.

A welding mockup on the full size Midland RPV head, which is similar to the Turkey Point RPV head, was used to demonstrate the welding technique described herein. During the mockup, thermocouples were placed to monitor the temperature of the head during welding. Thermocouples were placed on the outside surface of the RPV head within a 5-inch band surrounding the CRDM nozzle. Three other thermocouples were placed on the RPV head inside surface. One of the three thermocouples was placed 1-1/2 inches from the CRDM nozzle penetration, on the lower hillside. The other inside surface thermocouples were placed at the edge of the 5-inch band surrounding the CRDM nozzle, one on the lower hillside, the second on the upper hillside. During the mockup, all thermocouples fluctuated less than 15 degrees F throughout the 18-hour welding cycle. Based on past experience, it is believed that the temperature fluctuation was due more to the resistance heating temperature variations than the low heat input from the welding process. For the Midland RPV head mockup application 300 degrees F minimum preheat temperature was used. Therefore for ambient temperature conditions used for the weld proposed herein, the 350 degrees F maximum interpass temperature will certainly not be exceeded.

The automated weld method described above leaves a band of ferritic low alloy steel exposed to the primary coolant. The effect of corrosion on the exposed area, both reduction in RPV head thickness and primary coolant Iron (Fe) release rates, has been evaluated by Framatome-ANP (FRA-ANP). The results of this evaluation concluded that the total corrosion would be insignificant when compared to the thickness of the RPV closure head. It was also concluded that the total estimated Fe release (if all CRDM nozzles were replaced) would be significantly less than the total Fe release from all other sources.

L-2002-044 Attachment 1 Page 11 of 26

  • Relief from NB-5245 The areas to be examined are shown in Figure 7. The UT transducers and delivery tooling are capable of scanning from cylindrical surfaces with inside diameters near 2.75 inches. The UT equipment is not capable of scanning from the face of the taper. UT will scan approximately 70% of the weld surface.

Approximately 83% of the RPV head ferritic steel HAZ will be covered by the UT.

The transducers to be used are shown in Table 1. The UT coverage volumes are shown in Figures 8 through 12 for the various scans. Additionally, the final modification configuration and surrounding ferritic steel area affected by the welding is inaccessible or extremely difficult to obtain the necessary access and scans.

UT will be performed in lieu of RT due to the proposed new weld configuration.

Meaningful RT cannot be performed as can be seen in the applicable figures.

The weld configuration and geometry of the penetration in the RPV head provide an obstruction for the x-ray path and interpretation would be very difficult. UT will be substituted for the RT and qualified to evaluate defects in the proposed new weld and at the base metal interface. This examination method is considered adequate and superior to RT for this geometry. The new structural weld is sized like a coaxial cylinder partial penetration weld.Section III construction rules require progressive PT of partial penetration welds. The Section III original requirements for progressive PT were in lieu of volumetric examination.

Volumetric examination is not practical for a conventional partial penetration weld configuration. However, in this case, the weld is suitable for UT, except for the taper transition only, where a final surface PT will also be performed.

The effectiveness of the UT techniques to characterize the weld defects has been qualified by demonstration on a mockup of the temper bead weld involving the same metals used for proposed new weld. Notches were machined into the mockup at depths of 0.10", 0.15", and 0.25" in order to quantify the ability to characterize the depth of penetration into the nozzle. The depth characterization is done using tip diffraction UT techniques that have the ability to measure the depth of a reflector relative to the nozzle bore. Each of the notches in the mockup could be measured using the 45-degree transducer. During the examination longitudinal wave angle beams of 45 degrees and 70 degrees are used. These beams are directed along the nozzle axis looking up and down.

The downward looking beams are effective at detecting defects near the root of the weld because of the impedance change at the triple point. The 45-degree transducer is effective at depth characterization by measuring the time interval to the tip of the reflector relative to the transducer contact surface. The 70-degree longitudinal wave provides additional qualitative data to support information obtained with the 45-degree transducer. Together, these transducers provide good characterization of possible defects. These techniques are routinely used for examination of austenitic welds in the nuclear industry for flaw detection and sizing.

L-2002-044 Attachment 1 Page 12 of 26 In addition to the 45 and 70-degree beam angles described above, the weld is also examined in the circumferential direction using 45-degree longitudinal waves in both the clockwise and counterclockwise directions to look for transverse fabrication flaws. A 0-degree transducer is also used to look radially outward to examine the weld and adjacent metal for laminar type flaws and evidence of under bead cracking.

The final weld surface and a band around the weld area will be examined using PT as shown in Figure 6.

The purpose for the examination of the band is to assure all flaws associated with the weld area have been removed or addressed. The final modification configuration and surrounding ferritic steel area affected by the welding is inaccessible or extremely difficult to obtain the necessary access. The final examination of the new weld and immediate surrounding area within the band will be sufficient to verify that defects have not been induced in the low alloy RPV head metal due to the welding process. The PT examination extent is consistent with the Construction Code requirements.

  • Relief from NB-6111 ASME III NB-61 11 requires hydrostatic pressure testing of all pressure retaining components, appurtenances and completed systems. In lieu of hydrostatic testing of the repair a system leakage test will be performed.

Code hydrostatic testing subjects the piping system to a small increase in pressure over the nominal operating pressure and is not intended to present a significant challenge to pressure boundary integrity. It is used primarily as a means to enhance leakage detection during the examination of components under pressure, rather than as a measure to determine the structural integrity of components.

Industry experience has demonstrated that leaks are not being discovered as a result of hydrostatic test pressures propagating a pre-existing flaw through wall.

Most leaks are being found when the system is at normal operating pressure.

Hydrostatic tests are time consuming, require extensive operator support, and usually mean radiation exposure to personnel. Often additional equipment must be brought in to test a localized repair, which may involve additional exposure and expense. In many cases a system hydrostatic test must be conducted over large parts of the system. In this case the entire reactor coolant system would have to be subjected to the hydrostatic test.

Hydrostatic tests place a burden on the systems, increase radiation exposure and costs, require significant setup time, and add marginal value to the repair

L-2002-044 Attachment 1 Page 13 of 26 quality. These tests result in hardships without a compensating increase in the level of quality and safety. Performing the tests in accordance with the proposed alternative will provide reasonable assurance that flaws will be discovered.

FPL concludes that quality temper bead welds can be performed with 50 degree F minimum preheat and no post heat treatment based on FRA-ANP prior welding procedure qualification test data using machine GTAW ambient temperature temper bead welding. The qualifications of the ambient temperature temper bead welding process demonstrate that the proposed alternative provides an acceptable level of quality and safety.

Additional Information Regarding Occupational Exposure:

Recent experience gained from the performance of manual welds at other plants CRDM/CRDM nozzles indicated that more remote automated repair methods were needed to reduce radiation dose to personnel and still provide acceptable levels of quality and safety. Since FPL recognizes the importance of ALARA principles, this remote welding method has been developed for the possibility of leaking nozzles at Turkey Point Unit 3 or Unit 4.

This approach for repair of leaking CRDM nozzles will significantly reduce radiation dose to personnel while still maintaining acceptable levels of quality and safety. The total radiation dose (assuming one nozzle for estimation purposes) for the proposed remote repair method is projected to be approximately 7.5 REM. In contrast, using manual methods for Turkey Point Unit 3 or Unit 4 would result in a total radiation dose of approximately 32 REM.

VI. Implementation Schedule:

This relief is scheduled to be implemented if required during the Spring 2002 refueling outage planned for Unit 4. This relief will also be implemented if required at any future refueling outage in which the RPV head nozzle penetrations are inspected for through-wall leakage on either Unit 3 or Unit 4.

L-2002-044 Attachment 1 Page 14 of 26 Table 1:

PTN3 and PTN4 CRDM Proposed Weld UT Search Unit Transducer Characteristics Angle/Mode Freq. Size Focal Beam Depth Direction 00 L-wave 2.25 MHz .15" x .30" 0.45" N/A 450 L-wave 2.25 MHz .30"x .20" 0.45" Axial 700 L-wave 2.25 MHz .72" x .21" 0.69" Axial 450 L-wave 2.25 MHz .30" x.20" 0.45" Circ.

(effective)

L-2002-044 Attachment 1 Page 15 of 26 Discard I I Transverse Side Bend I I Reduced Section Tensile I I Transverse Side Bend

,* HAZ Charpy A V-Notch Transverse Side Bend Reduced Section Tensile Transverse Side Bend Discard SFusionO ne not We imetal i Heat Affected ..

Zone (HAZ)

GENERAL NOTE: Base metal Charpy impact specimens are not shown. This figure illustrates a similar-metal weld.

Figure 1

L-2002-044 Attachment 1 Page 16 of 26 Step 1: Deposit layer one with first layer weld parameters used in qualification.

Step 2: Deposit layer two with second layer weld parameters used in qualification. NOTE:

Particular care shall be taken in application of the second layer at the weld toe to ensure that the weld metal and HAZ of the base metal are tempered.

Step 3: Deposit layer three with third layer weld parameters used in qualification. NOTE:

Particular care shall be taken in application of the third layer at the weld toe to ensure that the weld metal and HAZ of the base metal are tempered.

Step 4: Subsequent layers to be deposited as qualified, with heat input less than or equal to that qualified in the test assembly. NOTE:

Particular care shall be taken in application of the fill layers to preserve the temper of the weld metal and HAZ GENERAL NOTE: The illustration above is for similar-metal welding using a ferritic filler material.

For dissimilar-metal welding, only the ferritic base metal is required to be welded using steps I through 3 of the temperbead welding technique.

AUTOMATIC OR MACHINE (GTAW) TEMPERBEAD WELDING Figure 2

L-2002-044 Attachment 1 Page 17 of 26 S- 0.625"

__I 1.50" MIN.

Figure 3 CRDM Machining

L-2002-044 Attachment 1 600 1-167 ALLOY Page 18 of 26 SA-302 GRB E(NS-fMe-7 P (UINSN06052) F_ 1/" MAX TRIPLE POINT 1.35" MIN AS-WELDED SURFACE FOR PT Figure 4 New CRDM Pressure Boundary Weld

L-2002-044 Attachment 1 Page 19 of 26 CRDM Nozzle Head 0.5" J-Groove Weld Figure 5 CRDM Temper-Bead Weld Repair, PT Coverage Prior to Welding

L-2002-044 Attachment 1 Page 20 of 26 CRDM Nozzle 0.5" Weld J-Groove Weld Machined Bore Figure 6 CRDM Temper-Bead Weld Repair, PT Coverage After Welding

L-2002-044 Attachment 1 Page 21 of 26 CRDM Nozzle.

HAZ in Nozzle 0.5"

- HAZ in Head Weld 0.25" Figure 7 CRDM Temper-Bead Weld Repair Areas to be Examined

L-2002-044 Attachment 1 Page 22 of 26 CRDM Nozzle Head Figure 8 CRDM Temper-Bead Weld Repair, UT 0 degree and 45L Beam Coverage Looking Clockwise and Counter-clockwise

L-2002-044 Attachment 1 Page 23 of 26 45L Beam Coverage Looking Down Figure 9 CRDM Temper-Bead Weld Repair, 45L UT Beam Coverage Looking Down

L-2002-044 Attachment 1 Page 24 of 26 CRDM Nozzle 45L Beam Coverage Looking Up Figure 10 CRDM Temper-Bead Weld Repair, 45L UT Beam Coverage Looking Up

L-2002-044 Attachment 1 Page 25 of 26 CRDM Nozzle 70L Beam Coverage Looking Down Figure 11 CRDM Temper-Bead Weld Repair, 70L UT Beam Coverage Looking Down

L-2002-044 Attachment 1 Page 26 of 26 CRDM Nozzle 70L Beam Coverage Looking Up Figure 12 CRDM Temper-Bead Weld Repair, 70L UT Beam Coverage Looking Up

L-2002-044 Attachment 2 Page 1 of 8 TURKEY POINT UNIT 3 AND UNIT 4 RELIEF REQUEST NO. 31 "CHARACTERIZATION OF REMAINING FLAWS"

1. COMPONENT IDENTIFICATION:

Turkey Point (PTN) Unit 3 and Unit 4 Reactor Vessel Closure Head CRDM Nozzle Penetrations, Class 1 FPL Drawing No. 561 0-M-400-57 Rev. 1

11. CODE REQUIREMENT:

ASME Sect. XI, 1989 Edition, no Addendum, IWA-3100 (a) Evaluation shall be made of flaws detected during an inservice examination as required by IWB 3000 for Class 1 pressure retaining components.

Ill. RELIEF REQUESTED:

Pursuant to 10 CFR 50.55a (g)(5)(iii), relief is requested from ASME XI which requires flaw characterization. It will be impractical to characterize the subject flaws by NDE and it will be impractical to show the flaws do not extend into the ferritic head base metal.

Relief is specifically requested from the following sections of the Code:

9 IWA-3300(b) and IWB-3420; in lieu of flaw characterization, ASME Section XI calculations will be performed to show the flaws are acceptable

  • IWB-2420(b) and IWB-2420(c); reexamination for the next three inspection periods; since initial inspection is impractical, subsequent inspections are also impractical.

IV. JUSTIFICATION FOR RELIEF:

The exterior surface of the reactor pressure vessel closure (RPV) head will be examined for evidence of leakage at the junction of the head penetrations and the head surface. Penetrations with evidence of leakage will be investigated and penetrations with verified leakage will be repaired as detailed herein. The repair method will not remove any indications found at the original weld joining the penetration to the head interior or the associated buttering. Due to the geometry of the weld area it is impractical to characterize such indications.

L-2002-044 Attachment 2 Page 2 of 8 The original CRDM nozzle to RPV head weld configuration is extremely difficult to UT due to the compound curvature and fillet radius as can be seen in Figure

1. These conditions preclude ultrasonic coupling and control of the sound beam in order to perform flaw sizing with reasonable confidence in the measured flaw dimension. Therefore it is impractical, and presently, the technology does not exist, to characterize flaw geometries that may exist therein. Not only is the configuration not conducive to UT but the dissimilar metal interface between the Ni-Cr-Fe weld and the low alloy steel closure head increases the UT difficulty.

Furthermore, due to limited accessibility from the RPV head outer surface and the proximity of adjacent nozzle penetrations, it is impractical to scan from this surface on the closure head base metal to detect flaws in the vicinity of the original weld. As a clarification, this inability to characterize the flaw will continue in the foreseeable future and subsequent examinations will also be impractical.

FPL has therefore assumed, for analysis purposes, that a flaw(s) may exist in this weld that extends from the weld surface to the weld to RPV head base metal interface. Based on extensive industry experience and Framatome ANP direct experience, there are no known cases where flaws initiating in an Alloy 82/182 weld have propagated into the ferritic base metal.

The worst-case assumption on flaw size is based on maximum crack growth by primary water stress corrosion cracking (PWSCC). Although a crack propagating through the J-groove weld by PWSCC would eventually grow to the low alloy steel RPV head, continued growth by PWSCC into the low alloy steel is not expected to occur. Stress corrosion cracking (SCC) of carbon and low alloy steels is not a problem under BWR or PWR conditions. SCC of steels containing up to 5% chromium is most frequently observed in caustic and nitrate solutions and in media containing hydrogen sulfide. Based on this information, SCC is not expected to be a concern for low alloy steel exposed to primary water. Instead, an interdendritic crack propagating from the J-groove weld area is expected to blunt and cease propagation. This has been shown to be the case for interdendritic SCC of stainless steel cladding cracks in charging pumps, and by recent events with PWSCC of Alloy 600 weld metals at Oconee 1 and VC Summer.

The surface examinations performed associated with flaw removal during recent repairs at Oconee 1 and 3 on RPV head CRDM nozzle penetrations, Catawba 2 steam generator channel head drain connection penetration, ANO-1 hot leg level tap penetrations, and the VC Summer Hot Leg pipe to primary outlet nozzle repair all support the assumption that the flaws would blunt at the interface of the N-iCr-Fe weld to ferritic base metal.

It will be shown to be acceptable to leave the postulated cracks in the original Ni Cr-Fe housing nozzle penetration J-prep buttering, or in the original Ni-Cr-Fe CRDM housing to RPV head attachment weld. The evaluations performed in

L-2002-044 Attachment 2 Page 3 of 8 support of this relief provide an equivalent acceptable level of quality and safety without performing flaw characterization as required in ASME,Section XI 1989, IWA-3300 (b) and IWB-3420.

ASME Section XI stress calculations will be performed to show the flaws are acceptable for a number of years. The only driving mechanism is fatigue crack growth. The evaluation will assume a radial (with respect to the penetration centerline) crack exists with a length equal to the partial penetration weld preparation depth.

An analysis of the new pressure boundary welds will be performed using a 3 dimensional model of a CRDM nozzle located at the most severe hillside orientation. The software program ANSYS (general purpose finite element program that is used industry-wide) will be used for this analysis. Per FRA-ANP internal procedures, the ANSYS computer code is independently verified as executing properly, by the solution of verification problems using ANSYS and then comparison of the results to independently determined values.

The analytical model will include the RPV head, CRDM nozzle, proposed new weld, and remnant portions of the original Ni-Cr-Fe welds. The model is analyzed for thermal transient conditions as contained in the Turkey Point Unit 3 and Unit 4 design specifications. The resulting maximum thermal gradients will be applied to the model along with the coincident internal pressure values. The ANSYS program will then calculate the stresses throughout the model (including the new welds). The stresses will be post-processed by ANSYS routines to categorize stresses consistent with the criteria of the ASME Code.

The calculated stress values are compared to the ASME Code,Section III, NB 3000 criteria for:

Design Conditions Normal, Operating, and Upset Conditions Emergency Conditions Faulted Conditions Testing Conditions A very conservative Stress Concentration Factor of 4.0 will be assumed for the new pressure boundary weld.

A primary stress analysis for design conditions will be performed. A maximum Primary General Membrane Stress Intensity (Pm) will be calculated and shown to be less than the maximum allowed by the ASME Code = 23.3 ksi. This value represents the maximum stress intensity for the alloy 600 nozzle remnant and the remaining original alloy 600 weld metal. The nozzle and weld metal have the minimum margin for primary stress criteria of any portion of the model (including repair weld, CRDM nozzle, original welds or low-alloy steel RPV head).

L-2002-044 Attachment 2 Page 4 of 8 The maximum cumulative fatigue usage factor will be calculated, and allowable years of future plant operation will be based on the maximum allowed ASME Code usage factor criterion of 1.0.

Additionally, a fracture mechanics evaluation will be performed to determine if degraded J-groove weld metal could be left in the vessel, with no examination to size any flaws that might remain following the repair. Since the hoop stresses in the J-groove weld are generally about two times the axial stress at the same location, the preferential direction for cracking is axial, or radial relative to the nozzle. It will be postulated that a radial crack in the Alloy 182 weld metal would propagate due to PWSCC, through the weld and butter, to the interface with the low alloy steel RPV head. It is fully expected that such a crack would then blunt and arrest at the butter-to-head interface. Ductile crack growth through the Alloy 182 metal would tend to relieve the residual stresses in the weld as the crack grew to its final size and blunted. Although residual stresses in the RPV head metal are low, it will be assumed that a small flaw could initiate in the low alloy steel metal and grow by fatigue. It will be postulated that a small flaw in the RPV head would combine with a large stress corrosion crack in the weld to form a radial corner flaw that would propagate into the low alloy steel RPV head by fatigue crack growth, under cyclic loading conditions associated with heatup and cooldown and other applicable transients.

Residual stresses will not be included in the flaw evaluations since it was demonstrated by analysis that these stresses are compressive in the low alloy steel base metal. Any residual stresses that remained in the area of the weld following the boring operation would be relieved by such a deep crack, and therefore need not be considered.

Flaw evaluations will be performed for a postulated radial corner crack on the RPV head penetration, where stresses are the highest and the radial distance from the inside corner to the low alloy steel base metal (crack depth) is the greatest. Hoop stresses will be used since they are perpendicular to the plane of the crack. Fatigue crack growth, calculated for the remaining operational life, should be small, and the final flaw size will be shown to meet the fracture toughness requirements of the ASME Code using an upper shelf value of 200 ksi /in for ferritic metals.

L-2002-044 Attachment 2 Page 5 of 8 The CRDM nozzle repair configuration is illustrated in Figures 1 and 2. The repair process is described below:

REPAIR PROCESS:

a) Visual inspections for leakage / boric acid deposits of CRDM nozzle penetrations on the exterior surface of the RPV head will be conducted when required during refueling outages.

b) CRDM nozzles that are determined to have through-wall leakage will be repaired. Remote machine processes are planned, to the extent practical.

c) Nondestructive examinations using ultrasonic methods are planned for the base metal of the nozzles determined to have through-wall leakage. The lower portion of the thermal sleeves will be removed by remotely operated methods to the extent practical.

d) Using a remote tool from below the RPV head, each of the leaking nozzles will first receive a roll expansion into the RPV head base metal to insure that the nozzle will not move during the repair operations.

e) A semi-automated machining tool operating underneath the RPV head will remove the entire lower portion of the CRDM nozzle to a location above the existing J-groove partial penetration weld. The machine tool will also form the CRDM nozzle weld preparation. The operation will sever the existing J groove partial penetration weld from the CRDM nozzles.

f) The machined surface will be cleaned, and then subjected to liquid penetrant examination (PT).

g) The repair will establish a new pressure boundary weld between the shortened nozzle and the inside bore of the RPV head. Welding will be performed with a remotely operated machine GTAW weld head using the temper bead process. Minimum preheat temperature will be 50 degrees F and the welding filler metal will be ERNiCrFe-7 (Alloy 52).

h) The final weld face, not including the taper transition, will be machined and/or ground.

i) The final weld will be liquid penetrant and ultrasonically examined prior to the subsequent abrasive water jet conditioning.

j) The final inside diameter surface of the CRDM nozzle near the new weld and the new weld will then be conditioned by abrasive water-jet conditioning to create a final surface that is in compression, to produce optimum resistance to primary water stress corrosion cracking. The replacement lower portion of the thermal sleeve will be re-installed.

k) A system leakage test will be performed.

L-2002-044 Attachment 2 Page 6 of 8 Based on extensive industry experience and Framatome ANP direct experience, there are no known cases where flaws initiating in an Alloy 82/182 weld have propagated into the ferritic base metal. The surface examinations performed associated with flaw removal during recent repairs at Oconee 1 and 3 on RPV head CRDM penetrations, Catawba 2 steam generator channel head drain connection penetration, ANO-1 hot leg level tap penetrations and the VC Summer Hot Leg pipe to primary outlet nozzle repair (reference MRP-44: Part I:

Alloy 82/182 Pipe Butt Welds, EPRI, 2001, TP-1 001491) all support the assumption that the flaws would blunt at the interface of the Ni-Cr-Fe weld to ferritic base metal. Additionally, the Small Diameter Alloy 600/690 Nozzle Repair Replacement Program (CE NPSD-1 198-P) provides data that shows PWSCC does not occur in ferritic pressure vessel steel. Based on industry experience and operation stress levels, there is no evidence that service related cracks would propagate through the Alloy 82/182 interface and into the ferritic metal.

Based on the discussion above, it can bee seen that it is impractical to characterize flaws in the J-groove weld by NDE and that it is impractical to show the flaws do not extend into the ferritic head base metal. Nevertheless, the evaluations discussed above provide an acceptable level of quality and safety without performing flaw characterization and repetitive reexamination as required in ASME Section XI 1989, IWA-3300 (b), IWB-3420, IWB-2420(b) and IWB 2420(c).

V. Implementation Schedule:

This relief is scheduled to be implemented if required during the Spring 2002 refueling outage planned for Unit 4. This relief will also be implemented if required at any future refueling outage in which the RPV head nozzle penetrations are inspected for through-wall leakage on either Unit 3 or Unit 4.

L-2002-044 Attachment 2 Page 7 of 8 H-- (.625)

L-2002-044 Attachment 2 Page 8 of 8 SA-302 GRB ERNICrFe-7 (UNS N06052) IMAX TRIPLE POINT 1.35 MIN POINT/

AS-WELDED SURFACE STSTEEL CLADDING SHALL BE SUITABLE FOR PT Figure 2 New CRDM Pressure Boundary Weld

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