ML13337A488

Request for Additional Information Regarding Relief Request RR-ISI-04-09, Saltwater System Piping Repair

ML13337A488
Person / Time
Site:	Calvert Cliffs
Issue date:	12/04/2013
From:	Nadiyah Morgan Plant Licensing Branch 1
To:	George Gellrich Calvert Cliffs
Morgan N
References
TAC MF3074
Download: ML13337A488 (6)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 December 4, 2013 Mr. George H. Gellrich, Vice President Calvert Cliffs Nuclear Power Plant, LLC Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657-4702

SUBJECT:

CALVERT CLIFFS NUCLEAR POWER PLANT, UNIT NO.2- REQUEST FOR ADDITIONAL INFORMATION REGARDING RELIEF REQUEST RR-ISI-04-09, SALTWATER SYSTEM PIPING REPAIR (TAC NO. MF3074)

Dear Mr. Gellrich:

By letter dated November 14, 2013, Calvert Cliffs Nuclear Power Plant, LLC, the licensee, submitted a request for authorization of a proposed alternative to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section XI, Sub paragraph IX-1 OOO(c)(4) for Calvert Cliffs Nuclear Power Plant, Unit No. 2. Specifically, the licensee proposed the installation of a mechanical clamping device on a leak discovered on a 12-inch, Code Class 3, saltwater system pipe.

The Nuclear Regulatory Commission (NRC) staff is reviewing the submittal and has determined that additional information is needed to complete its review. The specific questions are found in the enclosed request for additional information (RAI). The NRC staff requested a response to the RAI by December 2, 2013.

If you have any questions regarding this issue, please contact me at (301) 415-1016.

Sincerely, 1Jlolc:QJ e.- JAtD~j6ot Nadiyah S. Morgan, Project Manager Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-318

Enclosure:

Request for Additional Information cc w/encl: Distribution via Listserv

REQUEST FOR ADDITIONAL INFORMATION REGARDING RELIEF REQUEST RR-ISI-04-09 ALTERNATIVE REPAIR FOR SALTWATER SYSTEM PIPING CALVERT CLIFFS NUCLEAR POWER PLANT. LLC CALVERT CLIFFS NUCLEAR POWER PLANT. UNIT NO.2 DOCKET NO. 50-318 By letter dated November 14, 2013 (Agencywide Documents Access and Management System Accession No. ML13319B080), Calvert Cliffs Nuclear Power Plant, LLC, the licensee, submitted a request for authorization of a proposed alternative to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)Section XI, Sub paragraph IX-1000(c)(4) for Calvert Cliffs Nuclear Power Plant, Unit No.2 (Calvert Cliffs).

Specifically, the licensee proposed the installation of a mechanical clamping device on a leak discovered on a 12-inch, Code Class 3, saltwater system pipe. In order to complete its review, the Nuclear Regulatory Commission (NRC) staff requests the following information:

1. (a) Confirm that the defect area of the subject pipe is located in the discharge section of the saltwater system piping that provides no safety function, that the piping is above ground where it can be readily inspected, and that the pipe is not insulated or otherwise obstructed so as to increase the difficulty of inspections.

(b) It appears that the degraded area of the pipe may be located within a building in which flooding limits exist. What is the current leak rate from the pipe? What is the flooding limit, if any? Please describe the trend in the leak rate. Provide a flooding analysis demonstrating that in case the clamp fails, the leakage from the subject pipe will not exceed the flooding limits.

(c) Provide a piping and instrumentation diagram showing the subject pipe with respect to the saltwater system. Provide a piping isometric diagram showing the locations of pipe supports that are nearby the defect area. Identify the defect area on these diagrams.

(d) Provide additional drawings and photos of the mechanical clamp showing the assembly and design of the clamp, including the tubing, tubing grooves, sidebar, and sealant grooves on the inside surface of the clamp.

(e) The licensee submitted the relief request pursuant to Title 10 of the Code of Federal Regulations Section 50.55a(a)(3)(ii). Provide more information to justify the hardship of performing the repair/replacement in accordance with the ASME Code.

Enclosure

2. Page 3 of the relief request indicated 3 pin holes on the subject pipe. One pin hole is identified as having a diameter of 0.06-inch. Provide the current size and trending information for each of the holes in the pipe.

3. Page 4 of the relief request states that the clamp design will encompass the projected growth of the flaw with additional margin. Discuss the additional margin and whether the margin is sufficient to provide reasonable assurance that the subject pipe will perform its intended function until the pipe will be repaired/replaced in accordance with the ASME Code during the 2015 refueling outage. Discuss how much rubber liner has been removed from the defect area from the inside surface of the pipe.

4. (a) The NRC staff understands that once the clamp is installed, it is impossible to determine the growth of the defect area and the hole size unless the defect area grows outside the length of the clamp. Nevertheless, discuss any administrative leak rate and defect area in the axial, circumferential, or radial direction that will cause corrective actions to be initiated. Also, discuss the corrective actions.

(b) Discuss the leak rate and/or defect area and the hole size that will require an immediate repair or replacement of the pipe in mid-cycle.

(c) Discuss the critical defect area or hole size that will cause the pipe to fail catastrophically.

5. (a) Discuss the potential for the galvanic corrosion, since the stainless steel clamp will be in contact with the carbon steel pipe.

(b) The austenitic stainless steel from which the clamp is made is subject to pitting from chloride containing waters, such as sea water. Describe why stainless steel is appropriate for this service and/or how pitting of the clamp will be avoided

6. Attachment 2 to the November 14, 2013, letter specifies a regulatory commitment which states that "Verify that the installed mechanical clamping device is removed and replaced by a permanent code repair or component replacement [by] 04/01/2015." However, Section 6 of the relief request states that "The mechanical clamping device will remain in place until the next refueling outage scheduled for February 2015 or until Unit 2 enters a shutdown of sufficient duration prior to the refueling outage." The regulatory commitment is not consistent with the requirement in Section 6 of the relief request because it does not contain the following requirement " ... or until Unit 2 enters a shutdown of sufficient duration prior to the refueling outage." Clarify the discrepancy.

Design

7. (a) Article IX-5000 of Appendix IX to the ASME Code,Section XI, requires that a pressure test be conducted as part of the mechanical clamp installation. Discuss whether a pressure test will be conducted as part of the proposed alternative. If not, provide justification.

(b) Discuss any other deviation from Appendix IX of the ASME Code,Section XI, which will be taken besides the pipe size of 12 inches.

8. Page 4 of the relief request states that in an unlikely event, if the defect area would grow through wall around the circumference, the pipe would still be encapsulated inside the clamp. The licensee's calculation, ILD-CALC-0014, Revision 1, does not appear to analyze the double-ended guillotine pipe break event inside the clamp. Please clarify.

Installation

9. Describe the step-by-step installation procedure in detail, including the pre-installation inspection, surface preparation, and acceptance examination.

10. The relief request states that the defect area is located in an unisolable section of the pipe, meaning that coolant will be flowing inside the pipe while the clamp is being installed.

(a) Discuss whether the pin holes will be plugged before the clamp is installed.

(b) Discuss the possibility of the plug falling into the pipe during the plant operation if the pin holes continuously expand due to corrosion, since the pin holes will still be in contact with corrosive saltwater.

(c) The relief request states that the outside diameter of the pipe will be coated under the clamp to prevent saltwater corrosion of the carbon steel pipe. Given the apparent size of the holes and the resulting large leak rate, discuss what coating will be used and how will it be applied given that it appears that the pipe will be wet at the time of application.

11. (a) The NRC staff notes that sealant will be injected into the annular space between the pipe and the clamp and that the holes in the pipe are of a significant size. Please describe the means by which it will be assured that the sealant completely fills the annulus.

(b) Provide information on the sealant such as, how the sealant is qualified, what industrial Code it satisfies, how many years is sealant qualified for, what is the sealant condition (solid or liquid) after it is injected into the clamp, and would the sealant composition be affected by the pipe or ambient temperature.

(c) Discuss the hole size that the sealant would not be able to stop the leakage.

(d) Given the potential for continued growth of the holes, please describe the potential that the sealant will be exposed to flow and/or flow instabilities and be removed from inside of the clamp.

12. Is the clamp designed to prevent all leakage? Even if the clamp is designed to prevent leakage, is any leakage from the clamp permissible? If so, what is the allowable leak rate?

Inspection

13. Discuss the acceptance examination after the mechanical clamp is installed, as part of the installation procedure and the acceptance criteria (i.e., what clamp condition would be considered as unacceptable for service).

14. Page 5 of the relief request states that provisions have been made in the mechanical clamping device design and location to ensure that both edges of the mechanical clamping device are accessible for ultrasonic testing wall thickness measurement at least every ninety days. Provide the amount of the pipe area at both ends of the clamp that will be ultrasonically examined and discuss why this pipe area is sufficient for the ultrasonic examination.

15. The relief request proposes to monitor leakage weekly. Discuss whether a continuous monitoring system will be implemented or other existing continuous monitoring system that is available at the clamp. If significant leakage occurs between the weekly monitoring, discuss the safety significance of such leakage for a maximum of 7 days without notification.

16. Describe the extent of condition examinations performed. Has piping on this line, a few pipe diameters up and downstream of the defects, been examined? Have other similar valves and the areas immediately downstream been examined? Have other segments of the saltwater system piping been examined?

Analysis

17. From the clamp design drawing, it appears that the tubing in the inside surface of the clamp will touch the outside surface of the pipe. The metal-to-metal contact area affects how the clamp stresses, clamp imposed stresses on the pipe, and clamp fastener loading are calculated. Equation Number 18 in the licensee's calculation, ILD-CALC-0014, Revision 1, alluded to this contact area. Provide a diagram showing the contact area.

18. Article IX-3300(c) of Appendix IX to the ASME Code,Section XI, requires that effects of the stiffness and weight of the clamp shall be considered in the evaluation of the piping system.

It does not appear that the licensee's calculation, ILD-CALC-0014, Revision 1, considered the effects of clamp weight and stiffness on the pipe system. Clarify if the proposed alternative satisfies article IX-3300(c).

December 4, 2013 Mr. George H. Gellrich, Vice President Calvert Cliffs Nuclear Power Plant, LLC Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657-4702

SUBJECT:

CALVERT CLIFFS NUCLEAR POWER PLANT, UNIT NO.2- REQUEST FOR ADDITIONAL INFORMATION REGARDING RELIEF REQUEST RR-ISI-04-09, SALTWATER SYSTEM PIPING REPAIR (TAC NO. MF3074)

Dear Mr. Gellrich:

By letter dated November 14, 2013, Calvert Cliffs Nuclear Power Plant, LLC, the licensee, submitted a request for authorization of a proposed alternative to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section XI, Sub paragraph IX-1 OOO(c)(4) for Calvert Cliffs Nuclear Power Plant, Unit No. 2. Specifically, the licensee proposed the installation of a mechanical clamping device on a leak discovered on a 12-inch, Code Class 3, saltwater system pipe.

The Nuclear Regulatory Commission (NRC) staff is reviewing the submittal and has determined that additional information is needed to complete its review. The specific questions are found in the enclosed request for additional information (RAI). The NRC staff requested a response to the RAI by December 2, 2013.

If you have any questions regarding this issue, please contact me at (301) 415-1016.

Sincerely, Ira/ (MThadani for)

Nadiyah S. Morgan, Project Manager Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-318

Enclosure:

Request for Additional Information cc w/encl: Distribution via Listserv DISTRIBUTION:

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