W3F1-2011-0013, Request for Alternative W3-ISI-018, Inspection of Reactor Pressure Vessel Head Control Element Drive Mechanism Nozzles During the Third Ten-Year Inservice Inspection Interval
| ML110480484 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 02/16/2011 |
| From: | Steelman W Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| W3-ISI-018, W3F1-2011-0013 | |
| Download: ML110480484 (12) | |
Text
Entergy Operations, Inc.
17265 River Road Killona, LA 70057-3093 Tel 504-739-6685 Fax 504-739-6698 wsteelm@entergy.com William J. Steelman Licensing Manager Waterford 3 W3F1 -2011-0013 February 16, 2011 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
SUBJECT:
Request for Alternative W3-1SI-01 8, Inspection of Reactor Pressure Vessel Head Control Element Drive Mechanism Nozzles during the Third Ten-Year Inservice Inspection Interval Waterford Steam Electric Station, Unit 3 Docket No. 50-382 License No. NPF-38
REFERENCES:
- 1. Entergy Letter to the NRC dated October 19, 2009, "Request for Alternative W3-1SI-01 6, Inspection of Reactor Pressure Vessel Head Control Element Drve Mechanism Nozzles during Third Ten-Year Inservice Inspection Interval" (W3F1-2009-0058) [ADAMS Accession No. ML092940243]
- 2. Entergy Letter to the NRC dated November 2, 2009, "Response to NRC Request for Additional Information for Alternative W3-ISI-01 6, Inspection of Reactor Pressure Vessel Head Control Element Drive Mechanism Nozzles during Third Ten-Year Inservice Inspection Interval" (W33F1-2009-0062) [ADAMS Accession No.ML093080128]
- 3. NRC Letter to Entergy dated July 23, 2010, Waterford Steam Electric Station, Unit 3 - "Request For Alternative W3-1SI-016, Inspection of Reactor Pressure Vessel Head Control Element Drive Mechanism Nozzles during Third 10-Year Inservice Inspection Interval" (TAC No.
ME241 1) [ADAMS Accession No. ML101470453]
Dear Sir or Madam:
Pursuant to 10 CFR 50.55a(a)(3)(ii), Entergy Operations, Inc (Entergy) requests an alternative to the inspection requirements of American Society of Mechanical Engineers (ASME) Code Case N-729-1, as conditioned by 10 CFR 50.55a(g)(6)(ii)(D), for Waterford 3 Steam Electric Station, Unit 3 (Waterford 3) for the spring 2011 (RF17) refueling outage.
Effective October 10, 2008, the Nuclear Regulatory Commission (NRC) amended 10 CFR 50.55a to include ASME Code Case N-729-1, "Alternative Examination Requirements for Pressurized Water Reactor (PWR) Reactor Vessel Upper Heads With Nozzles Having Pressure-Retaining Partial-Penetration Welds,Section XI, Division 1," with conditions. Once
W3F1-2011-0013 Page 2 a licensee implements the code case, the First Revised NRC Order EA-03-009 (the Order) is no longer applicable and shall be deemed to be withdrawn.
In References 1 and 2 above, Entergy requested relief from Code Case N-729-1, as conditioned by 10 CFR 50.55a(g)(6)(ii)(D) for Waterford 3 during the fall 2009 refueling outage 16 (RF16). Specifically, the bottom of the Waterford 3 control element drive mechanism (CEDM) nozzles contains a threaded area that cannot be effectively examined to the extent required. In Reference 3, the NRC granted ASME Code relief based on the conclusion that performance of inspection below the J-groove weld requirements would result in hardship without a compensating increase in the level of quality and safety.
Entergy was scheduled to replace the original steam generators and reactor pressure vessel (RPV) head during the spring 2011 refueling outage (RF17). However, due to a discovered manufacturing condition, the replacement steam generators will not be available for installation during RF17. Replacement of the RPV head must utilize a construction opening in containment which will necessitate its replacement to be concurrent with the replacement steam generators now scheduled for the fall of 2012 (RF18). As a result of this deferral, the installed Waterford 3 RPV head will require further examination in accordance with Code Case N-729-1 as conditioned by 10 CFR 50.55a(g)(6)(ii)(D) during the upcoming spring 2011 refueling outage. However, Entergy is requesting an ASME Code alternative to these examination requirements.
The performance demonstration initiative (PDI) qualification performed by Electric Power Research Institute (EPRI) added limitations to the CEDM examinations. In particular, the qualification process imposed a limitation on use of circumferentially oriented Time of Flight Diffraction (TOFD) ultrasonic transducers for detection of circumferential flaws.
During the fall of 2009 (RF16), Entergy performed RPV head CEDM examinations in accordance with Code Alternative W3-ISI-016. The Waterford 3 RPV CEDM nozzle examinations did not reveal any primary water stress corrosion cracking (PWSCC) degradation. These inspection results are consistent with historical examinations which have also not identified PWSCC degradation. The volumetric examinations were completed to the extent of UT examination tooling capability to 1.544 inches (blind zone) above the bottom of the nozzle.
In Table 1 of Reference 2, Entergy provided freespan lengths of the CEDM nozzles below the J-groove weld based on volumetric data measurements taken in 2005 (RF1 3). The geometry of the nozzle, the scan length to measurable extent of the nozzle end, and UT TOFD design, examination software, and delivery system since 2005 are essentially the same and do not alter the freespan length measurement results. Therefore, the CEDM nozzle freespan lengths and coverage achieved in RF16 will be consistent with that provided in Table 1 whereby further freespan measurement is not necessary. Entergy will obtain the required coverage for the CEDM nozzle volumetric examinations during the upcoming spring 2011 refueling outage (RF1 7). Comparing Table 1 with the analytically required freespan lengths from Reference 2 as provided below, the proposed alternative provides a combination of UT examinations to the extent possible, to ensure that a postulated flaw in the lower portion of the nozzle that cannot be volumetrically (UT) examined will not propagate into the toe of the J-groove weld within one operating cycle.
W3F1-2011-0013 Page 3 Nozzle Group Assumed Available Minimum Propagation (Head Angle Degrees) Propagation Length (inch) Length (inch) 0 1.029 0.265 7.8 1.002 0.250 29.1 0.637 0.160 49.7 0.420 0.160 Pursuant to 10 CFR 50.55a(a)(3)(ii), Entergy requests approval of the proposed alternative to the requirements of Code Case N-729-1 as conditioned by 10 CFR 50.55a(g)(6)(ii)(D) for the upcoming spring 2011 Waterford 3 refueling outage. The request is provided in Attachment 1 to this letter. It should be noted that the request is the same as that requested in References 1 and 2.
Entergy requests approval of the attached Alternative W3-ISI-01 8 by April 6, 2011, in order to support timely completion of the Waterford 3 RPV head examinations during the spring 2011 refueling outage.
This relief request includes one new commitment as provided in Attachment 2.
If you have any questions or require additional information, please contact me at 504-739-6685.
Sincerely, WJS/SAB Attachments:
- 1. Request for Alternative W3-ISI-018, Inspection of RPV Head Control Element Drive Mechanism Nozzles during the Third Ten-Year Inservice Inspection Interval
- 2. List of Regulatory Commitments
W3F1-2011-0013 Page 4 cc: Mr. Elmo E. Collins, Jr.
Regional Administrator U. S. Nuclear Regulatory Commission Region IV 612 E. Lamar Blvd., Suite 400 Arlington, TX 76011-8064 NRC Senior Resident Inspector Waterford Steam Electric Station, Unit 3 P.O. Box 822 Killona, LA 70066-0751 U.S. Nuclear Regulatory Commission Attn: Mr. N. Kalyanam MS 0-07 D1 Washington, DC 20555-0001
Attachment I to W3F1-2011-0013 Request for Alternative W3-ISI-01 8, Inspection of RPV Head Control Element Drive Mechanism Nozzles During the Third Ten-Year Inservice Inspection Interval to W3F1 -2011-0013 Page 1 of 5 Entergy Operations, Inc.
Waterford Steam Electric Station, Unit 3 Request for Alternative W3-ISI-018, Inspection of RPV Head Control Element Drive Mechanism Nozzles During the Third Ten-Year Inservice Inspection Interval I. ASME CODE COMPONENT AFFECTED Waterford Steam Electric Station, Unit 3 (Waterford 3) has one hundred-two (102) ASME Class 1 reactor pressure vessel (RPV) head penetration nozzles comprised of ninety-one (91) Control Element Drive Mechanism (CEDM) nozzles, ten (10) In-Core Instrument (ICI) nozzles, and one (1) vent line nozzle. This request pertains to the CEDM nozzles only.
Component Numbers: Ninety one (91) RPV head CEDM Nozzles [02-T-01 through 02-T-91 ]
Code
References:
(1) ASME Section Xl 2001 Edition through 2003 Addenda (2) ASME Code Case N-729-1, as conditioned by 10 CFR 50.55a(g)(6)(ii)(D)
Examination Category: Code Case N-729-1 in lieu of Table IWB-2500-1 Exam Category B-P Item Number: B4.20
Description:
Proposed Alternative to Table 1 of ASME Code Case N-729-1 as conditioned by 10 CFR 50.55a(g)(6)(ii)(D)
Unit/Inspection Waterford 3 / Third (3 rd) 10-year inspection interval Interval Applicability: May 31, 2008 thru July 2017 II. APPLICABLE CODE REQUIREMENT The Code of Federal Regulations (Rule) 10 CFR 50.55a(g)(6)(ii)(D)(3) requires:
Instead of the specified 'examinationmethod' requirements for volumetric and surface examinationsin Note 6 of Table 1 of Code Case N-729-1, the licensee shall perform volumetric and/orsurface examination of essentially 100 percent of the required volume or equivalent surfaces of the nozzle tube, as identified by Figure 2 of ASME Code Case N-729- 1. A demonstratedvolumetric or surface leak path assessment through all J-groove welds shall be performed. If a surface examination is being substituted for a volumetric examination on a portion of a penetration nozzle that is below the toe of the J-groove weld [Point E on Figure 2 of ASME Code Case N-729-1], the surface examination shall be of the inside and outside wetted surface of the penetration nozzle not examined volumetrically.
Code Case N-729-1 (Reference 1) requires that components shall be examined as specified in Table 1 of the code case.
to W3F1 -2011-0013 Page 2 of 5 III. REASON FOR REQUEST Pursuant to 10 CFR 50.55a(a)(3)(ii), Entergy Operations, Inc. (Entergy) requests an alternative to the requirements of Code Case N-729-1 as conditioned by 10 CFR 50.55a(g)(6)(ii)(D) for the spring 2011 refueling outage 17 (RF1 7). Entergy plans to inspect the RPV head CEDM penetration nozzles at Waterford 3 using the ultrasonic testing (UT) method to the extent possible. Under the First Revised NRC Order EA 009 (Reference 4) and associated relaxation request, a UT inspection from the inside diameter (ID)of the CEDM nozzles at Waterford 3 has been previously performed from 2 inches above the root of the J-groove weld down to a point approximately 1.544 inches above the bottom of the nozzle (See Figure 4 in Reference 2). This 1.544 inch "blind zone" is due to limitations resulting from CEDM nozzle configuration (1.344 inches) and inspection probe design (0.200 inches). These limitations are discussed below. The hardships associated with these limitations are discussed in Reference 2.
Nozzle Configquration Limitation - Guide cones are attached to the bottoms of the Waterford 3 CEDM nozzles via threaded connections. Specifically, the guide cone screws into the end of the CEDM nozzle with a welded set screw and two tack welds at the cone-nozzle interface to secure the guide cone to the nozzle. The length of the threaded connection region is 1.25 inches. Additionally, a 450 chamfer exists immediately above the threaded connection region. The length of the chamfer region is 0.094 inches.
Due to the threaded connection and chamfer region at the bottom of each CEDM nozzle, a meaningful UT examination in that area cannot be performed. Specifically, the chamfer region geometry causes sporadic signals while, once the guide cone is reached, sound cannot pass into the CEDM nozzle base material because of the gap that exists between the guide cone and the nozzle at the threaded connection. Therefore, UT of the bottom 1.344 inches (1.25 + 0.094) of the CEDM nozzles is not possible.
Inspection Probe Design Limitation - The inspection probe to be used to inspect the Waterford 3 CEDM nozzles typically consists of multiple individual transducers. Various probe configurations may be utilized to perform the inspections.
The inspection probe is designed so that the ultrasonic transducers are slightly recessed into the transducer holder. This recess must be filled with water to provide an acoustic coupling between the transducer and the nozzle wall. Because of this design, the complete diameter of the transducer must fully contact the inspection surface before ultrasonic information can be collected. Because UT probes have a diameter of 0.250 inch, these transducers, in theory, are able to collect meaningful UT data down to a point approximately 0.125 inch (1/2 diameter) above the chamfer. However, when the lower edge of the transducer recess drops below the chamfer, the water between the transducer and the nozzle cannot be maintained, and the acoustic coupling is lost. Based on prior UT inspection experience and a review of UT data from previous inspections, meaningful data down to a point 0.200 inches above the chamfer can be collected.
to W3F1 -2011-0013 Page 3 of 5 IV. PROPOSED ALTERNATIVE AND BASIS FOR USE Proposed Alternative UT Examination - The ID of each CEDM nozzle (i.e., nozzle base material) will be volumetrically examined from the applicable point above the root of the J-groove weld (per Code Case N-729-1, 1.5 inches for nozzles with an incidence angle less than or equal to 300, and 1.0 inch for nozzles with an incidence angle greater than 300); down to 1.544 inches above the bottom of the nozzle.
The data acquisition techniques used are similar, but improved over those used in previous examination activities under the Order. The UT examination procedures, equipment, and personnel being applied have been qualified by EPRI in accordance with 10 CFR 50.55a(g)(6)(ii)(D). In addition, a demonstrated UT leak path assessment will be performed for all of the CEDM nozzle penetrations. Entergy will also perform a bare metal visual (BMV) inspection of the RPV head surface in accordance with Code Case N-729-1 during the spring 2011 refueling outage.
Analysis - The acceptability of the proposed alternative is established by an engineering evaluation that includes a finite element stress analysis and fracture mechanics evaluations. The intent of the engineering evaluation is to determine whether sufficient crack propagation length exists between the tip of a postulated crack and the toe of the J-groove weld to facilitate one cycle of crack growth without the crack reaching the weld.
Augmented Inspections - Based on the analytical results discussed in Reference 2 and as described in the response to NRC Question 5 of Reference 3, no augmented examinations are necessary for Waterford 3.
Basis for Use The background and basis for the proposed alternative is provided in References 2 and 3, with regard to the requirements of the Order.- There are some differences between the requirements of the Order and the requirements of Code Case N-729-1 as conditioned by 10 CFR 50.55a.
Differences in the Required Examination Volume The examination volume required by the Order specified ultrasonic testing of the RPV head penetration nozzle (i.e., nozzle base material) from 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 2 inches below the lowest point at the toe of the J-groove weld on a horizontal plane perpendicular to the nozzle axis (or the bottom of the nozzle if less than 2 inches); OR from 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 1.0 inch below the lowest point at the toe of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) and including all RPV head penetration nozzle surfaces below the J-groove weld that have an operating stress level (including all residual and normal operating stresses) of 20 ksi tension and greater.
to W3F1-20111-0013 Page 4 of 5 The examination volume required by Code Case N-729-1 specifies volumetric or surface testing of the RPV head penetration nozzle (i.e., nozzle base material) from 1.5 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 1.5 inches below the lowest point at the toe of the J-groove weld on a horizontal plane perpendicular to the nozzle axis (or the bottom of the nozzle if less than 1.5 inches) for nozzles with an incidence angle less than or equal to 300; and from 1.0 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 1.0 inches below the lowest point at the toe of the J-groove weld on a horizontal plane perpendicular to the nozzle axis (or the bottom of the nozzle if less than 1.0 inches) for nozzles with an incidence angle greater than 300.
Differences in the specified examination frequency between the Order and Code Case N-729-1 are not relevant because this relief request is a one time request due to the Waterford 3 reactor closure head being replaced in the next refueling outage in the fall of 2012.
The proposed alternative provides a combination of UT examinations to the extent possible, to ensure that a postulated flaw in the lower portion of the nozzle that cannot be volumetrically (UT) examined will not propagate into the weld during one cycle of operation. The basis for the proposed alternative does not require that the specified UT examination volume be met; therefore, the basis for the proposed alternative remains valid with regard to the differences between the examination volumes specified in the Order and in Code Case N-729-1.
10 CFR 50.55a(a)(3) states:
"Proposedalternativesto the requirementsof paragraphs(c), (d), (e), (f), (g) and (h) of this section or portions thereof may be used when authorized by the Directorof the Office of Nuclear Reactor Regulation. The applicantshall demonstrate that:
(i) The proposedalternatives would provide an acceptable level of quality and safety, or (ii) Compliance with the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety."
Entergy believes the proposed alternative provides an acceptable level of quality and safety by utilizing a combination of examination and supplemental analysis to ensure the pressure boundary integrity of the Waterford-3 CEDM nozzles for one operating cycle.
Other possible examination options, such as manual surface examinations, would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. This request is the same as the request for relaxation documented in Reference 2 and approved by the NRC in Reference 5.
V. DURATION OF PROPOSED ALTERNATIVE The proposed alternative will apply to the existing RPV head for the spring 2011 (RF1 7)
Waterford 3 refueling outage CEDM examinations. Entergy is scheduled to replace the Waterford 3 RPV head during the fall 2012 refueling outage.
to W3F1-2011-0013 Page 5 of 5 VI. PRECEDENT This same alternative was requested by Entergy on October 19, 2009 (Reference 6) and approved by NRC Safety Evaluation dated July 23, 2010 (Reference 7) for Waterford 3's Alternative W3-1S1-016.
VII. REFERENCES
- 1. ASME Code Case N-729-1, "Alternative Examination Requirements for PWR Reactor Vessel Upper Heads With Nozzles Having Pressure-Retaining Partial-Penetration Welds,Section XI, Division 1", Approved March 28, 2006.
- 2. Entergy Letter to the NRC dated April 15, 2004, 'Waterford 3 Relaxation Request #4 to NRC Order EA-03-009 for the Control Element Drive Mechanism Nozzles" (CNRO-2004-0020) (ML041120367).
- 3. Entergy Letter to the NRC dated August 13, 2004, Response to NRC Request for Additional Information Pertaining to Waterford 3 Relaxation Request #4 to NRC Order EA-03-009 for the Control Element Drive Mechanism Nozzles (CNRO-2004-0039)
[ML042320558].
- 4. First Revised NRC Order (EA-03-009) Establishing Interim Inspection Requirements for Reactor Pressure Vessel Heads at Pressurized Water Reactors, issued on February 20, 2004 [ML040220181].
- 5. NRC Letter to Entergy dated March 22, 2005, Waterford Steam Electric Station, Unit 3 (Waterford 3) - "Relaxation Request from U.S. Nuclear Regulatory Commission (NRC)
First Revised Order EA-03-009 for Control Element Drive Mechanism (CEDM)
Nozzles" (TAC No. MC2643) [ML050820683].
- 6. Entergy Letter to the NRC dated October 19, 2009, "Request for Alternative W3-1SI-016, Inspection of Reactor Pressure Vessel Head Control Element Drive Mechanism Nozzles during Third Ten-Year Inservice Inspection Interval" (TAC NO. ME241 1)
[ML092940243].
- 7. NRC letter to Entergy dated July 23, 2010, Waterford Steam Electric Station, Unit 3 -
"Request for Alternative W3-1SI-016, Inspection of Reactor Pressure Vessel Head Control Element Drive Mechanism Nozzles during Third Ten-Year Inservice Inspection Interval" (ML101470453) to W3F1-2011-0013 List of Regulatory Commitments to W3F1-2011-0013 Page 1 of 1 List of Regulatory Commitments The following table identifies those actions committed to by Entergy in this document. Any other statements in this submittal are provided for information purposes and are not considered to be regulatory commitments.
TYPE SCHEDULED COMPLETION DATE COMMITMENT (Check one)
(If Required)
ONE-TIME CONTINUING ACTION COMPLIANCE The alternative examination proposed by X Spring 2011 W3-ISI-0 18 will be performed for the Refueling Outage Waterford 3 CEDM nozzle examinations.