2CAN121205, Response to the Request for Additional Information Regarding Requests for Relief ANO2-ISI-009, ANO2-ISI-011 and ANO2-ISI-012
| ML12354A202 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 12/17/2012 |
| From: | Pyle S Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 2CAN121205 | |
| Download: ML12354A202 (10) | |
Text
Entergy Entergy Operations, Inc.
1448 S.R. 333 Russellville, AR 72802 Tel 479-858-4704 Stephenie L. Pyle Manager, Licensing Arkansas Nuclear One 2CAN121205 December 17, 2012 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
SUBJECT:
Response to the Request for Additional Information Regarding Requests for Relief ANO2-1SI-009, ANO2-ISI-01 1 and ANO2-lSI-01 2 Arkansas Nuclear One, Unit 2 Docket No. 50-368 License No. NPF-6
REFERENCES:
- 1. Entergy letter to NRC, "Requests for Relief from American Society of Mechanical Engineers (ASME) Section Xl Volumetric and Surface Examination Requirements - Third 10-Year Interval," dated March 26, 2012 (2CAN031203) (ML12086A293)
- 2. NRC email to Entergy, "RAI on Request for Relief No. ANO2-ISI-009, ANO2-ISI-011 and ANO2-ISI-012," dated September 6, 2012 (TAC Nos. ME8271, ME8273 and ME8274)
Dear Sir or Madam:
Entergy Operations, Inc. requested NRC's approval of several Requests for Relief for Arkansas Nuclear One, Unit 2 (ANO-2) via Reference 1 for the third 10-year interval. These requests are associated with the requirements of the ASME, Boiler and Pressure Vessel Code, Section Xl pertaining to 100% coverage by volumetric or surface examinations for the key bracket of the integrally welded attachment (ANO2-1SI-009), the vertical restraint of integrally welded attachment (ANO2-1SI-01 1), and three heat exchanger circumferential welds (ANO2-1SI-01 2) at ANO-2.
In Reference 2, the NRC determined that additional information was needed to complete the review of the subject requests provided in Reference 1. Attached are the requests for additional information and corresponding responses.
This submittal contains no regulatory commitments.
Awl
2CAN 121205 Page 2 of 2 Should you have any questions, please contact me.
Sincerely, SLP/rwc
Attachment:
Request for Additional Information Requests for Relief ANO2-ISI-009, ANO2-ISI-01 1 and ANO2-ISI-012 cc:
Mr. Elmo E. Collins Regional Administrator U. S. Nuclear Regulatory Commission, Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 NRC Senior Resident Inspector Arkansas Nuclear One P. 0. Box 310 London, AR 72847 U. S. Nuclear Regulatory Commission Attn: Mr. Kaly Kalyanam MS 0-8 B1 One White Flint North 11555 Rockville Pike Rockville, MD 20852
Attachment to 2CAN121205 Response to Request for Additional Information Requests for Relief ANO2-ISI-009, ANO2-ISI-011 and ANO2-ISI-012
Attachment to 2CAN121205 Page 1 of 7 REQUEST FOR ADDITIONAL INFORMATION REQUESTS FOR RELIEF ANO2-1SI-009, ANO2-ISI-O11 and ANO2-ISI-012 Relief Request ANO-2-ISI-009 Basis for Relief (As stated):
During surface examination of the vessel integral attachment weld, 100% coverage of the required examination area could not be obtained.
The configuration of the subject component is a metal key bracket with dimensions approximately twenty-two inches by eight inches welded on four sides. The bracket is integrally welded to the steam generate shell. The angle iron insulation support below the bracket is welded in place and restricts access to the lower portion of the weld. Code examination of this type of integral attachment weld requires a surface examination technique, such as a Liquid Dye Penetrate or Magnetic Particle Testing, of the weld crown surface and 1/2
/2inch of base material on either side of the weld toes. However, due to the configuration of this integral attachment and associated welded insulation support, access to the lower weld and surrounding base material for examination purposes is limited.
In order to perform additional or alternative Code examinations, modification and/or replacement of the insulation support would be required. The examination performed on the available surface area of the subject item would detect generic degradation, if it existed, demonstrating an acceptable level of integrity
RAI-1
Table I of the Relief Request ANO2-ISl-009 indicated that due to the limited access to the lower weld and surrounding base material of the vessel integral attachment weld, only 62 percent of coverage could be achieved during surface examination. To ensure that the impracticability determination will not cause safety concern and the surface examination results are indicative of the entire welds, please (1) report prior inspection results, (2) confirm that the entire subject attachment weld is exposed to the same environment (e.g., not a portion of the weld is covered by insulation material), and (3) discuss the stresses on the welds during operation, demonstrating that the stresses in the uninspected lower weld and the surrounding base material are not significantly higher than those in the 62 percent covered area such that the limited inspection results are representative of the entire welds.
Responses (1)
The Arkansas Nuclear One, Unit 2 (ANO-2) steam generators (SGs) were replaced in the fall of 2000. The surface examinations were performed for the first time on component 04-008 in April 2002. No indications were noted from that examination. The first surface examination of the newly installed component 04-009 was in October 2003.
The examination results noted some acceptable rounded indications. These indications
Attachment to 2CAN121205 Page 2 of 7 are indicative of original weld construction (porosity). There is no examination data prior to these examinations.
(2)
The SG key bracket lug attachment welds are covered with insulation during normal power operations. The insulation would provide a barrier from any external environment.
(3)
A review of the stress analysis associated with the bracket and its welds showed that the maximum stress interaction ratio (IR) is 0.32. This stress IR is for Level A and Level B (Normal and Upset) loading conditions. If it is conservatively assumed that only 50% of the area of the bracket and its welds is carrying the all the loads, the resultant maximum IR would be 0.64. This is less than 1.0 and demonstrates there is a significant amount of margin. The bracket and its welds remain code qualified; therefore, the stresses in the limited inspection area represents the stresses in the entire welds.
Relief Request ANO-2-ISI-01 1 Basis for Relief (As stated):
During surface examination of the pipe support integral attachment weld, 100% coverage of the required examination area could not be obtained.
The configuration of the subject component is four 5/8" x 1" x 1" lugs, placed 4 1/16" apart end-to-end in pairs at 00 and 1800 on the vertical pipe. The lugs are integrally welded to the pipe with full penetration welds. The two piece four-inch wide hanger strap is positioned and bolted between the end to end lugs, contacting the upper lugs which support the vertical pipe. Code examination of this type of integral attachment weld requires a surface examination technique, such as Liquid Dye Penetrate or Magnetic Particle Testing, of the weld crown surface and 2 inch of base material on either side of the weld toes. However, due to the configuration of this integral attachment and associated hanger strap, access to the weld ends and surrounding base material for examination purposes is limited.
In order to perform additional or alternative Code examinations, modification and/or replacement of the component would be required. The examination performed on the available surface area of the subject item would detect generic degradation, if it existed, demonstrating an acceptable level of integrity.
RAI-2
This relief request regards the integrally welded attachment and associated pipe support.
A description of the lugs attached to the vertical pipe with a hanger strap in proximity is described in the relief request. Please (1) report prior inspection results, (2) confirm that ASME Code Item B10.20 is the correct designation because B10.20 is related to pumps but the requested is related to piping, (3) provide a sketch to clarify the description of pipe lugs and hanger strap, showing the interference by hanger strap during surface examinations, (4) discuss the stresses on the welds during operation, demonstrating that the stresses in the uninspected weld ends and surrounding base material are not significantly higher than those in the 88 percent covered area such that the limited inspection results are representative of the entire welds.
Attachment to 2CAN 121205 Page 3 of 7 Responses (1)
The previous examinations of component 22-071W was satisfactorily performed in March 1994 with no limitations noted and no relevant indications recorded.
(2)
The ASME Code of record at the time of the subject examination was the 1992 Edition.
The correct ASME Code Item is B10.10 per the ASME Section XI Code, 1992 Edition, examination category B-K-1. The Code Item B130.20 as referred to in the relief request ANO2-ISI-01 1 for Category B-K-1 is inadvertently referencing the ASME Section Xl Code, 2001-2003 Addenda, code category B-K, Item number B10.20, which is the ASME Code of record for the later interval.
Please note the corrected Item number as B10.10 (3)
The hanger drawing 2CCA-22-H7 provides an illustration of the lugs and the hanger straps. See the drawings on pages 6 and 7 of this attachment.
(4)
A review of the stress analysis associated with the lugs and its welds showed that the maximum stress IR is 0.41. It is conservatively assumed that 80% of the lug and its weld is effective. The resultant maximum IR would be approximately 0.51. This is less than 1.0 and demonstrates there is a significant amount of margin. The piping stresses and additional stresses due to lugs remain code qualified; therefore, the stresses in the limited inspection area represents the stresses in the entire welds.
Relief Request ANO-2-ISI-012 Basis for Relief (As stated):
During ultrasonic examination of the Letdown Heat Exchanger Flange-to-Channel Circumferential Weld and the Shutdown Cooling Heat Exchanger Flange-to-Channel Cylinder and Channel Cylinder-to-Tubesheet Welds listed in Table 1 below, 100% coverage of the required examination volumes could not be obtained.
Due to the geometric configuration of the components and the close proximity of other structures which limited scan paths, the use of approved beam angles in the axial and circumferential direction were, not able to achieve greater than 90% code required volume.
See Table 1 below for additional information.
Radiography is not practical on these types of nozzle-to-vessel weld configurations which prevent placement of the film and exposure source. To effectively perform any significant additional Code allowable ultrasonic examinations, modification and/or replacement of the component would be required. The examinations performed on the subject items in addition to the examination of other vessel welds contained in the Inservice Inspection (ISI) program would detect generic degradation, if it existed, demonstrating an acceptable level of integrity.
Attachment to 2CAN121205 Page 4 of 7
RAI-3
This relief request regards the letdown heat exchanger flange-to-channel (45.7 %
coverage), shutdown cooling heat exchanger flange-to-channel (69.5 % coverage), and shutdown cooling heat exchanger channel cylinder-to-tube (81.8 % coverage) sheet circumferential welds. For all three circumferential welds, please discuss the stresses on the welds during operation, demonstrating that the stresses in the uninspected areas are not significantly higher than those in the covered areas such that the limited inspection results are representative of the entire welds. Additionally, both descriptions under "Examination Summary" of Table I for Weld 45-001 and Weld 49-001 indicated that the circumferential coverage of the welds were limited due to the inlet and outlet piping configurations attached to the shell. Yet, the difference in coverage due to the similar interference is big (45.7 % coverage versus 69.5 % coverage). Please provide a discussion.
Responses (1)
Stresses on the welds Shutdown heat exchanger flange-to-channel weld The circumferential weld 49-001 would likely have some variance in the stress profile around the nozzle. This variance results from the bending moments introduced from the inlet/outlet piping. The nozzle induced stress was found to be within the 1971 ASME Section VIII recommendations (current code at time of design).
Other cantilever loads on the weld from the vessel components and content weight and its effect on the stress profile were considered and are negligible.
Since the weld supported section is free, any interaction with the support structure and inlet/outlet piping or other restraints does not significantly contribute to any stress redistribution in the weld other than the local influence of the bending moment stress at the nozzle root.
Shutdown heat exchanger cylinder-to-tubesheet weld The circumferential weld 49-002 would likely have some variance in the stress profile around the nozzle. This variance results from the bending moments introduced from the inlet/outlet piping. The nozzle induced stress was found to be within the 1971 ASME Section VIII recommendations (current code during design).
The cylinder-to-tubesheet weld supports a section of the heat exchanger between the exchanger supports and tube inlet/outlet ports. The reaction of the supports and the inlet/outlet piping produces only negligible influence on the stress distribution in the weld due to additional shear / axial / torsional stresses. The local influence of the inlet/outlet bending moment and associated nozzle root stress may influence the stress distribution near the weld.
Attachment to 2CAN121205 Page 5 of 7 Other cantilever loads on the weld from the vessel components and content weight and its effect on the stress profile were considered and are negligible.
Letdown heat exchan-ger flange-to-channel weld The circumferential weld 45-001 would likely have some variance in the stress profile around the nozzle. This variance results from the bending moments introduced from the inlet/outlet piping.
Other cantilever loads on the weld from the vessel components and content weight and its effect on the stress profile were considered and are negligible.
Since the weld supported section is free, any interaction with the support structure and inlet/outlet piping or other restraints does not significantly contribute to any stress redistribution in the weld other than the local influence of the bending moment stress at the nozzle root.
(2)
Relative to the examination coverage claimed on Components45-001 and 49-001.
Component 49-001 is a carbon steel component with stainless steel cladding. It was examined in January 2004 with the appropriate ferritic steel ultrasonic examination procedure, which allowed for extension of coverage through a carbon steel weld to the opposite side. The combination of being a single-sided examination, weld cap configuration which impeded complete scanning across the weld and the inlet and outlet piping resulted in an examination of approximately 69.5% cumulative code required coverage.
Component 45-001 is a stainless steel component. It was examined in March 2008 with the appropriate austenitic steel ultrasonic examination procedure which does not allow for extension of coverage through a stainless steel weld to the opposite side. Due to the single-side access of a stainless steel component, examination volume coverage was limited from the start to 50%. The inlet and outlet piping obstructions resulted in an approximate limitation of 4.3%, which resulted in an examination of approximately 45.7%
cumulative code required coverage. It is worthy to note that the examination scanning process cross-sectional scan plot indicates ultrasound energy penetrating into the far side of the weld; however, the procedure qualification process does not allow crediting the scan volume for coverage.
Attachment to 2CAN121205 Page 6 of 7 SECTION C-C SECTION B-B LOOKING UP 1 1/16" OIA.
HOLES TYP.
(2) PLCS.--*
11/16" DIA.
HOLES TYP (2) PLCS.
5/8" X 4" CS 3 1/2" 1 2 1/8" TYP.
SECTION D-D DETAIL A
{
FULL
-K-PENETRATION TYP (2) PLACES 45' SECTION E-E PARTIAL PLAN VIEW ITEMS 1.4 & 5 NOT SHOWN FOR CLARITY N
PIPE SUPPORT I DRAWING NO:
2CCA-22-H7 PAGE 3 OF 4 1 REV.-
8 PIESPOT DAIGN:
Attachment to 2CAN 121205 Page 7 of 7 2'-9 1/8" iI
!I l'-9 7/8" 9 3/4" ELEVATION gA-A PIPE SUPPORT I DRAWING NO:
2CC~-22--H7 I PAGE 20F4 IREV:
8 PIPE SUPPORT I DRAWING NO:
2CCA-22-H7 I PAGE 2 OF 4 1 REV:
8