RS-22-032, Relief Request I4R-13 Relief from Code Examinations for 1B33-F060A and 1B33-F060B Repairs
| ML22061A000 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 03/02/2022 |
| From: | Lueshen K Constellation Energy Generation |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RS-22-032 | |
| Download: ML22061A000 (14) | |
Text
4300 Winfield Road Warrenville, IL 60555 630 657 2000 Office RS-22-032 10 CFR 50.55a March 2, 2022 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 LaSalle County Station, Unit 1 Renewed Facility Operating License No. NPF-11 NRC Docket No. 50-373
Subject:
Relief Request I4R-13 Relief from Code Examinations for 1B33-F060A and 1B33-F060B Repairs In accordance with 10 CFR 50.55a, "Codes and standards," paragraph (z)(2), Constellation Energy Generation, LLC (CEG) requests NRC approval of the attached relief request associated with the fourth Inservice Inspection (ISI) interval for LaSalle County Station (LSCS),
Unit 1.
The fourth interval of the LSCS Unit 1 ISI Program is based on the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code),Section XI, 2007 Edition through 2008 Addenda. The fourth ISI interval at LSCS began on October 1, 2017 and is currently scheduled to end September 30, 2027.
The attached relief request, I4R-13, is associated with repair of the LSCS Unit 1 Reactor Recirculation flow control valves, 1B33-F060A and 1B33-F060B, which is currently in progress.
Specifically, I4R-13 requests authorization of alternative examination requirements for the repair of the valves in accordance with ASME Section XI, paragraph IWA-4000. Additionally, I4R-13 requests relief from the radiography examination requirements required by NB-2539 for the 1B33-F060A and 1B33-F060B.
CEG requests authorization of the proposed alternative and relief from radiography requirements by March 7, 2022.
There are no regulatory commitments contained within this letter. Should you have any questions concerning this letter, please contact Mr. Jason Taken at (630) 657-3660.
March 2, 2022 U.S. Nuclear Regulatory Commission Page 2 Respectfully, Lueshen, Digitally signed by Lueshen, Kevin Kevin Date: 2022.03.02 01:43:02 -06'00' Kevin Lueshen Sr. Manager - Licensing Constellation Energy Generation, LLC Attachments:
- 1. Relief Request I4R-13 Associated with Alternative Examination Requirements for Repairs of Reactor Recirculation Flow Control Valves
- 2. Associated Figures cc: NRC Regional Administrator, Region III NRC Senior Resident Inspector - LaSalle County Station NRC Project Manager, NRR - LaSalle County Station Illinois Emergency Management Agency - Division of Nuclear Safety
ATTACHMENT 1 Relief Request I4R-13 Associated with Alternative Examination Requirements for Repair of Reactor Recirculation Flow Control Valves 1B33-F060A and 1B33-F060B
ATTACHMENT 1 10 CFR 50.55a Relief Request I4R-13 Alternative Examination Requirements for Repair of Reactor Recirculation Flow Control Valves in Accordance with 10 CFR 50.55a(z)(2)
--Hardship or Unusual Difficulty Without Compensating Increase in Level of Quality or Safety--
- 1. ASME Code Component(s) Affected LaSalle County Station (LSCS), Unit 1 valve 1B33-F060A ("A" Reactor Recirculation System Flow Control Valve).
LaSalle County Station (LSCS), Unit 1 valve 1B33-F060B ("B" Reactor Recirculation System Flow Control Valve).
1B33-F060A and 1B33-F060B valves are ASME Section XI, Class 1 (Section III 1971 Edition, Summer 1972 Addenda) components, and the valve bodies are ASME SA-351 Grade CF8M material.
The design temperature of the valves is 575°F and the design pressure of the valves is 1675 psig. The design pressure of the attached system is 1650 psig. The maximum valve operating temperature is 550°F with a maximum operating pressure of 1260 psig.
2. Applicable Code Edition and Addenda
The Code of Construction is ASME Section III 1971 Edition, Summer 1972 Addenda.
For LaSalle County Station Unit 1, the Inservice Inspection Code of Record and Interval Dates are:
Interval Section XI Interval Start Interval End Edition/Addenda Date Date Fourth 2007 Edition, through October 1, September 30, 2008 Addenda 2017 2027
3. Applicable Code Requirement
ASME Section XI IWA-4411, "Welding, Brazing, Fabrication, and Installation," states in part:
Welding brazing, fabrication, and installation shall be performed in accordance with the Owners Requirementsand in accordance with the Construction Code of the item.
ASME Section III NB-2570, "Examination and Repair of Statically and Centrifugally Cast Products," contains NB-2571, "Required Examinations," which states in part:
Cast pressure-retaining materials shall be examined by radiographic methods, except cast ferritic steels shall be examined by either radiographic or ultrasonic methods or a combination of both methodsIn addition, all cast products shall be examined on all external surfaces and all accessible internal surfaces by either magnetic particle or liquid penetrant methods. Machined surfaces, except threaded surfaces, of a cast Page 1 of 8
ATTACHMENT 1 10 CFR 50.55a Relief Request I4R-13 Alternative Examination Requirements for Repair of Reactor Recirculation Flow Control Valves in Accordance with 10 CFR 50.55a(z)(2)
--Hardship or Unusual Difficulty Without Compensating Increase in Level of Quality or Safety--
product shall be examined by either liquid penetrant or magnetic particle methods after machining.
ASME Section III NB-2573, "Radiographic Examination," contains NB-2573.1, "Extent, Methods, and Acceptance Standards," which provides the requirements and associated references for conducting radiographic examination.
ASME Section III NB-2578, "Elimination of Defects," states:
Elimination of defects shall be in accordance with NB-2538.
ASME Section III NB-2579, "Repair by Welding," states in part:
Repair by welding shall be in accordance with NB-2539.
ASME Section III NB-2538, "Elimination of Surface Defects," subparagraph (a)(3) states in part:
After defect elimination, the area is reexamined bythe liquid penetrant method in accordance with NB-2546 to assure that the defect has been removed or the indication reduced to an acceptable size.
ASME Section III NB-2539, "Repair by Welding," contains NB-2539.4, "Examination of Repair Welds," which states in part:
Each repair weld shall be examined bythe liquid penetrant method in accordance with the requirements of NB-2546. In addition, repair cavities, the depth of which exceeds the lesser of 3/8 in. or 10 percent of the section thickness, shall be radiographed after repair in accordance with NB-5110 and to the acceptance standards of NB-5320.
ASME Section III NB-2546, "Liquid Penetrant Examination," provides the requirements for conducting liquid penetrant examinations along with the Acceptance Standards.
ASME Section III NB-5110, "Procedures, Qualifications and Evaluation," and ASME Section III NB-5320, "Radiographic Acceptance Standards," provide the general requirements and associated acceptance standards for radiographic examination, respectively.
ASME Section III NB-5250, "Fillet and Socket Welds," states:
Fillet and socket welds shall be examined by either the magnetic particle or liquid penetrant method.
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ATTACHMENT 1 10 CFR 50.55a Relief Request I4R-13 Alternative Examination Requirements for Repair of Reactor Recirculation Flow Control Valves in Accordance with 10 CFR 50.55a(z)(2)
--Hardship or Unusual Difficulty Without Compensating Increase in Level of Quality or Safety--
4. Reason for Request
In accordance with 10 CFR 50.55a(z)(2), relief is requested on the basis that compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Background
In an effort to identify the source of the debris found in LSCS Unit 2 Reactor Pressure Vessel Jet Pumps during the previous refueling outage (L2R17) in February 2019, detailed inspections of the Reactor Recirculation (RR) system flow control valves were scheduled and performed during refueling outage (L2R18). Extent of condition inspections were also scheduled and performed during the current Unit 1 refueling outage (L1R19) in February 2022. Upon disassembly of the 1B33-F060A and 1B33-F060B valves, excessive wear to each valve's internals and lower body was discovered. In order to restore the valves to an acceptable condition to allow the valve internals to fit into the valve body, activities in accordance with ASME Section III and ASME Section XI requirements will be employed.
Valve Details Drawings of the 1B33-F060A and 1B33-F060B valves are provided in Attachment 2. Figure I4R-13-1 is the drawing of the entire valve assembly, including the actuator for 1B33-F060A and 1B33-F060B. Figure I4R-13-2 is a close-up drawing of the area of the 1B33-F060A and 1B33-F060B valve bodies. Figure I4R-13-2 is highlighted in orange for the lower guide plug, blue for the guide plug anti-rotation segment, and yellow as the estimated area of wear in the valve body where material is missing due to the lower guide plug impact on the valve body. The as-found wear areas on both valves were in similar locations.
1B33-F060A LSCS completed direct thickness measurements for the valve body of 1B33-F060A using 3-dimensional (3D) laser scanning technology. The 3D scan revealed the as-found wear and all other areas of the valve to be above the minimum design wall thickness by at least 0.065 inches. The as-found areas of wear for the 1B33-F060A valve require machining and welding to restore valve body to dimensions and tolerances that support internal components.
As part of the repair, additional weld material will be applied and machined (above minimum wall thickness) to support valve body configuration to interface with the modified lower plug guide. To ensure wear does not challenge the minimum wall thickness due to the internal design change, wear rate calculations have been performed based on the utilization of the 316 stainless steel Stellite-overlayed lower plug guide. These calculations indicate the wear rate to be 0.00015 inches per operating cycle. This supports the determination that Page 3 of 8
ATTACHMENT 1 10 CFR 50.55a Relief Request I4R-13 Alternative Examination Requirements for Repair of Reactor Recirculation Flow Control Valves in Accordance with 10 CFR 50.55a(z)(2)
--Hardship or Unusual Difficulty Without Compensating Increase in Level of Quality or Safety--
welding/machining to approximately 0.157 inches above minimum wall in the area of wear to be of sufficient thickness to support end of life operation with the new design.
1B33-F060B LSCS completed direct thickness measurements for the valve body of 1B33-F060B using 3-dimensional (3D) laser scanning technology. The 3D scan revealed the as-found wear and all other areas of the valve to be above the minimum design wall thickness by at least 0.400 inches. The as-found areas of wear for the 1B33-F060B valve require machining to restore valve body to dimensions and tolerances that support internal components. The current condition of 1B33-F060B does not necessitate welding. However, in the event that the repair plan requires welding, the welding would be conducted consistent with ASME code requirements and the examination requirements outlined in this request.
To ensure wear does not challenge the minimum wall thickness due to the internal design change, wear rate calculations have been performed based on the utilization of the 316 stainless steel Stellite-overlayed lower plug guide. These calculations indicate the wear rate to be 0.00015 inches per operating cycle. This supports the determination that welding/machining to greater than 0.200 inches above minimum wall in the area of wear to be of sufficient thickness to support end of life operation with the new design.
Repair Plan and Valve Restoration The current valve body measurements for the 1B33-F060A and 1B33-F060B valves indicate that repairs need to be performed on the valve bodies. As a result, these valves need to be restored in accordance with NB-2538.
NB-2538 requires a liquid penetrant (PT) examination to be performed following removal of the defect. NB-2539 requires that repair cavities the depth of which exceeds the lesser of 3/8 in. or 10 percent of the section thickness, shall be radiographed. After removal of the defect, weld buildup using the machine Gas Tungsten Arc Welding process will be performed in accordance with NB-2539 to increase margin to minimum wall thickness.
Following weld build up and in accordance with NB-2539, a PT examination must be performed of the weld surface and a radiographic examination must be performed of the weld repairs as indicated above.
CEG confirms that micrometer measurements will be taken of the depth and internal bores of the machined areas to validate proper dimensions. The measurement tools have precision of 0.001 inches. These measurements will verify the valve body configuration to allow for reassembly and functionality, as well as assuring material thickness above the minimum wall thickness and design requirements.
CEG does not plan to monitor minimum wall thickness over time. Due to valve internal geometry, direct monitoring of minimum wall thickness through a method such as ultrasonic Page 4 of 8
ATTACHMENT 1 10 CFR 50.55a Relief Request I4R-13 Alternative Examination Requirements for Repair of Reactor Recirculation Flow Control Valves in Accordance with 10 CFR 50.55a(z)(2)
--Hardship or Unusual Difficulty Without Compensating Increase in Level of Quality or Safety--
testing is not possible. Additionally, wear rate calculations support valve operation through end of plant life without encroaching on minimum wall thickness.
Modified Lower Guide Plug Installation To enhance design and performance of the 1B33-F060A and 1B33-F060B, LSCS is installing modified lower plug guides (similar to the lower plug guides installed on LSCS Unit 2 during L2R18). The modified lower plug guide design includes an anti-rotation segment similar to the original design. Exelon Industrial Services (EIS) manufactured the anti-rotation segment. The material of the anti-rotation device is specified as 304L stainless steel material. The anti-rotation segment will be fillet welded or partial penetration welded along its entire outer curved edge on the top face with an appropriately qualified and suitable material for the design of the weld joint. The fillet weld will be performed using the stainless metal inert gas (MIG) welding technique.
ASME Section III paragraphs NB-5245, NB-5250, and NB-5260 require a PT examination to be performed following completion of a partial penetration welds, fillet welds, and structural attachment welds made to pressure retaining materials, respectively. An EVT-1 examination of this weld will be performed in lieu of any required PT examination. The modified lower plug guide design incorporates several features to reduce internal wear on the valve body that may result in reduction of wall thickness. The anti-rotation device is welded in place to restrict undesirable movement between the modified lower plug guide and the valve body.
This weld design is superior to the original configuration. Additionally, the modified design incorporates tight fit-up tolerances which limit relative motion between valve internals.
Finally, the modified lower plug guide material and valve body are both made of stainless steel which results in less adverse impact and potential wear on the valve body.
Radiological Hardship During the L1R19 refueling outage, significant radiological dose rates are being experienced both internally to the valves and in the external area surrounding the valves. Therefore, LSCS is employing several approaches to limit the personnel exposure during the valve repair activities (e.g., automatic welding is being used).
The internal dose rate at the bottom of valve 1B33-F060A is 2.1 R/hour, and the internal dose rate at the bottom of valve 1B33-F060B is 1.7 R/hour. The total combined exposure impact for performing surface examinations (PT) associated with both valve repairs is estimated at 3.406 person-Rem. This is based on stay time estimates for examiners to perform PT and radiographic examinations under the conditions described below. As a result of the significant dose rates, LSCS has evaluated alternatives to the required nondestructive examinations (NDE).
By comparison, performing the PT examination scope using the proposed alternative of EVT-1 approach discussed in Section 5, "Proposed Alternative and Basis of Use," would result in an estimated EVT-1 examination dose of 1.080 person-Rem, which represents an Page 5 of 8
ATTACHMENT 1 10 CFR 50.55a Relief Request I4R-13 Alternative Examination Requirements for Repair of Reactor Recirculation Flow Control Valves in Accordance with 10 CFR 50.55a(z)(2)
--Hardship or Unusual Difficulty Without Compensating Increase in Level of Quality or Safety--
approximate radiological dose savings of 2.326 person-Rem. This substantial radiological dose reduction is due to the EVT-1 examination not requiring the NDE technicians to be inside the valve bodies when compared to the PT examinations. Additionally, not performing the radiographic examination provides an additional radiological dose savings of approximately 0.906 person-Rem. Therefore, the total radiological dose savings associated with this relief request is approximately 3.232 person-Rem.
Physical Limitations Hardship The area of repair inside valves 1B33-F060A and 1B33-F060B is at the bottom of each valve which is approximately 42 inches from the main flange on the top of the valve body.
Additionally, the valve throat opening is 18 inches in diameter. To perform PT examinations, NDE technicians have limited remote options available to support performing the PT surface examinations. Technicians must clean the examination surface prior to applying the dye penetrant. Although penetrant dye may be applied using a brush with an attachment piece to limit entering the valve body, the technician must enter the valve body to adequately remove excessive dye penetrant and to apply and remove developer.
To perform radiographic examinations, NDE technicians are challenged due to valve access restrictions to position the film inside the valve. With the current dose rates inside the valve between 1.7 to 2.1 R/hour, the ability to produce a quality radiographic examination film required by the ASME Code will be impacted due to exposure of the same type of gamma radiation. Placing the source for radiography from inside of the valve body and the film on the outside of the valve, presents an issue of being able to properly distance the radiography source to satisfy the ASME Code required geometric calculation. Lastly, the size and weight of the container for the Cobalt-60 source is 2'x3'x3' and nearly 800 pounds, which represents a physical challenge.
The significant radiological dose and physical limitations associated with the PT and radiographic examinations of 1B33-F060A and 1B33-F060B in accordance with the ASME Code would be contrary to the as low as reasonably achievable (ALARA) radiological controls program.
5. Proposed Alternative and Basis for Use
In lieu of the surface examination requirements of ASME Section III 1971 Edition, Summer 1972 Addenda and/or ASME Section XI 2007 Edition with 2008 Addenda associated with repair activities on valves 1B33-F060A and 1B33-F060B, CEG proposes to substitute the PT examinations with EVT-1.
The proposed alternative of enhanced VT-1 visual examination (EVT-1) will be performed as part of the repair activities. Following machining activities, an EVT-1 will be performed to ensure surface quality on both the 1B33-F060A and 1B33-F060B.
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ATTACHMENT 1 10 CFR 50.55a Relief Request I4R-13 Alternative Examination Requirements for Repair of Reactor Recirculation Flow Control Valves in Accordance with 10 CFR 50.55a(z)(2)
--Hardship or Unusual Difficulty Without Compensating Increase in Level of Quality or Safety--
For the anti-rotation device weld, an enhanced visual examination (EVT-1) will be performed on the first pass and on the final weld in lieu of a liquid penetrant (PT) examination of the final weld.
Machining and welding activities as necessary will then be performed to increase margin to minimum wall thickness and restore dimensions and tolerances that support internal components.
The enhanced visual examination of the machined surfaces will be performed using methods and personnel qualified to the standards of ASME Section XI VT-1 visual examination requirements. The EVT-1 will be conducted using remote visual equipment such as a video probe or camera equipment. The acceptance criteria used to evaluate any possible flaws found during the EVT-1 examinations will be consistent with NB-2546.3, "Acceptance Standards," from ASME Section III 1971 Edition, Summer 1972 Addenda.
CEG has performed a resolution demonstration, which is the process of demonstrating the ability of the remote visual examination equipment, equipment setup, inspection area environment, and inspection technique to resolve the appropriate 0.044-inch characters.
CEG has evaluated the resolution and examination capabilities of the EVT-1 and PT examination methods. A comparison between the two techniques demonstrates that the EVT-1 will provide the ability to detect a post-machining or post-welding flaw as the PT method with no loss of examination capability. Specifically:
Liquid Penetrant (and Magnetic Particle) acceptance criteria is required to identify an indication with dimensions greater than 1/16 inch (0.0625 inches).
Visual Examination, EVT-1 examination capabilities are demonstrated before and after the examination to dimensions down to 0.044-inch characters.
EVT-1 is a proven and accepted visual examination method and technique as described in Electric Power Research Institute (EPRI) Technical Report (TR) 3002007793, "Remote Visual Testing Round-Robin Study," published December 2, 2016, and NRC NUREG/CR 7246, PNNL-27003, "Reliability Assessment of Remote Visual Examination," published August 2018.
EPRI TR 3002007793 documented an approach that has been used throughout the nuclear industry for remote visual examination of various types of flaws, simulated cracks, electrical discharge machining (EDM) notches and actual cracks for its demonstration. In addition, EVT-1 examinations are routinely used for In Vessel Inspections (IVVI) under the boiling water reactors (BWR) Vessel and Internals Project (VIP) at BWR.
The NRC has approved EVT-1 as an acceptable alternative to PT examination previously as described in Section 7 below.
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ATTACHMENT 1 10 CFR 50.55a Relief Request I4R-13 Alternative Examination Requirements for Repair of Reactor Recirculation Flow Control Valves in Accordance with 10 CFR 50.55a(z)(2)
--Hardship or Unusual Difficulty Without Compensating Increase in Level of Quality or Safety--
Accordingly, CEG requests relief to perform EVT-1 examination in lieu PT examination requirements as outlined above and relief to not perform radiography examinations following planned repairs of the 1B33-F060A and 1B33-F060B valves.
6. Duration of Proposed Alternative
Use of this proposed alternative is applicable only to L1R19 repair activities associated with 1B33-F060A and 1B33-F060B valves.
7. Precedents
LaSalle County Station, Units 1 and 2 - Supplemental Information regarding Relief Request I4R-12 Relief from Code Examinations for 2B33-F060A and 2B33-F060B Repairs, Revision 2, dated March 26, 2021 (ADAMS Accession No. ML21067A000)
Braidwood Station, Units 1 and 2 - Relief from the Requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (EPID L-2018-LLR-0033), dated January 17, 2019 (ADAMS Accession No. ML18347B419).
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ATTACHMENT 2 Associated Figures
Figure I4R-13-1
Figure I4R-13-2