ML14050A127
| ML14050A127 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 02/14/2014 |
| From: | Robinson K Calvert Cliffs, Constellation Energy Nuclear Group, EDF Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC MF3413, TAC MF3414 | |
| Download: ML14050A127 (11) | |
Text
Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, Maryland 20657 CENG.
a joint venture of O
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CALVERT CLIFFS NUCLEAR POWER PLANT February 14, 2014 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
SUBJECT:
REFERENCES:
Document Control Desk Calvert Cliffs Nuclear Power Plant Unit Nos. 1 & 2; Docket Nos. 50-317 & 50-318 Response to Request for Additional Information, Re: Calvert Cliffs Proposed Alternative RR-ISI-04-08, Revision I (a)
Letter from K. F. Robinson (CCNPP) to Document Control Desk (NRC),
dated January 29, 2014, Revised Proposed Alternative for Mitigation of Buried Saltwater Piping Degradation (RR-ISI-04-08, Revision 1)
(b)
Letter from N. S. Morgan (NRC) to G. H. Gellrich (CCNPP), dated February 11, 2014, Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 and 2 -
Request for Additional Information Regarding Relief Request RR-ISI-04-08, Revision 1, Mitigation of Buried Saltwater System Piping Degradation (TAC Nos. MF3413 and MF3414)
In Reference (a), Calvert Cliffs Nuclear Power Plant, LLC submitted for the Nuclear Regulatory Commission's approval a revised proposed alternative (RR-ISI-04-08, Revision 1) for mitigation of buried Saltwater System piping degradation.
In Reference (b), the Nuclear Regulatory Commission issued a request for additional information.
Attachment (1) contains our response to the request for additional information.
This letter contains one regulatory commitment as listed in Attachment (2). This commitment replaces the commitments listed in Reference (a). The reason for this change is discussed in our response to Request for Additional Information No. 4.
Document Control Desk February 14, 2014 Page 2 Should you have questions regarding this matter, please contact Mr. Douglas E. Lauver at (410) 495-5219.
Very truly yours,
- - Kenneth F. Robinson Manager - Engineering Services KFR/KLG/bjd
Attachment:
(1)
Request for Additional Information Regarding Relief Request RR-ISI-04-08, Revision 1 (2)
N. S. Morgan W. M. Dean, NRC Resident Inspector, NRC S. Gray, DNR
ATTACHMENT (1)
REQUEST FOR ADDITIONAL INFORMATION REGARDING RELIEF REQUEST RR-ISI-04-08, REVISION 1 Calvert Cliffs Nuclear Power Plant, LLC February 14, 2014
ATTACHMENT (1)
REQUEST FOR ADDITIONAL INFORMATION REGARDING RELIEF REQUEST RR-ISI-04-08, REVISION 1 By letter dated January 29, 2014 (Agency wide Documents Access and Management System (ADAMS)
Accession No. ML14034A173), Calvert Cliffs Nuclear Power Plant, LLC (Calvert Cliffs), 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, IWA-4000 for Calvert Cliffs Nuclear Power Plant, Unit Nos. I and 2.
Specifically, the licensee proposed the installation of a sleeve assembly primarily consisting of a pressure retaining backing plate, an internal rubber gasket and four retaining bands, as a repair system for defects in the buried saltwater system piping.
In order to complete its review, the Nuclear Regulatory Commission (NRC) staff requests the following information:
NRC RAI No. 1:
Page 4 of the RR-ISI-04-08, Rev. I contains text which states.
Prior to installation of the sleeve, the cement lining for the entire length of the sleeve assembly will be removed and repaired with an approved sealant. To prevent galvanic corrosion, the outer surface of the backing plate will be wrapped with a 1/8" thick rubber gasket so that the stainless steel backing plate does not come in direct contact with ductile cast iron piping.
Page 4 of the RR-ISI-04-08, Rev. 1 also contains Figure 2. Figure 2 appears to be either in conflict with or an over simplification of the above text. Based primarily on the above text, the NRC staff believes that the process of installing the repair will include the following steps:
a) Identification and characterization of the location to be repaired b)
Removal of the all the mortar lining from the pipe for a length equal to the length of the rubber seal c)
Application of sealing material (sealant) in the location from which the mortar has been removed d) Insertion of the 1/8-inch rubber gasket on top of the sealant to ensure that the backing plate will not contact the ductile iron pipe e)
Insertion of the Al6XN backing plate fi Insertion of the rubber gasket g) Insertion of the AI6XN bands Please correct text and diagrams in RR-ISI-04-08, Rev. 1, and/or the NRC staff's understanding of the repair process as appropriate.
Calvert Cliffs concurs with the steps described above. Figure 2 on page 4 of RR-ISI-04-08, Revision 1, shows only the main components of the repair system [Ethylene Propylene Diene Monomer (EPDM) gasket, backing plate, and the retaining bands]. It does not show the sealant coating on the pipe inner surface nor the rubber gasket which is placed on top of the sealant. Figure 2 is meant for illustration purposes only and therefore, shows only the main components of the repair system.
1
ATTACHMENT (1)
REQUEST FOR ADDITIONAL INFORMATION REGARDING RELIEF REQUEST RR-ISI-04-08, REVISION 1 NRC RAI No. 2:
In the last paragraph on Page 4 of RR-ISI-04-08, Rev. 1 you stated that an approved sealant will be used to repair the cement lining at the defect area prior to installing the rubber seal.
a)
Reference the industry standards (e.g., American Society for Testing and Materials [ASTA4]
sections) to which the sealant was qualified, discuss the qualifying conditions (the temperature and pressure under which the sealant is qualified), and the qualified service life of the sealant.
b)
Will the sealant be hard or remain pliable when it is applied to the excavated area of the inside surface of the pipe?
c)
How thick or deep will the sealant be when it is applied?
d)
Will the backing plate have good contact with the sealant? If not, have the stress calculations, which permit this repair to be used for pipe degradations up to 3 inches in diameter, considered this lack of contact between the backing plate and the sealant?
Per RR-ISI-04-08, Revision 1, the 1/4" cement coating on the inside surface will be removed and repaired by applying an approved sealant to the bare ductile cast iron substrate to protect ductile cast iron surfaces before the application of the rubber gasket, backing plate, EPDM gasket, and retaining bands. The currently approved materials that would be used in this application are a paste grade, used for filling and contouring back to the original surface contour of the ductile cast iron pipe, and a coating designed to go over the rebuilt areas and provide erosion and corrosion resistance to the metal surfaces. These materials have been used in many applications in the Saltwater System and were first approved at Calvert Cliffs in 1992. These materials will be applied to provide a smooth, continuous surface, which will allow good contact to the rubber gasket, which in turn will be in good contact with the backing plate.
a)
Below are the ASTM tests performed by the manufacturer (per the material's specification sheets),
on the materials that will be used for sealing the metal surface once the cement coating is removed.
" Paste material which will be used for filling and returning to the original contour of the metallic substrate:
o Compressive Strength: ASTM D695 (13000 psi) o Flexural Strength: ASTM D790 (10000 psi) o Tensile Shear Adhesion:
ASTM D1002 (mild steel 2700 psi, Brass 2200 psi, copper 2200 psi, Stainless Steel 3000 psi) o Hardness: ASTM D785 (Rockwell R104) o Heat distortion: ASTM D648 (264 psi fiber stress, 136 F) o Corrosion Resistance:
ASTM B 117-73 (no sign of corrosion after 5000 hours0.0579 days <br />1.389 hours <br />0.00827 weeks <br />0.0019 months <br /> salt spray cabinet) o Dielectric Strength: ASTM D149 (32 volts/mil) o Dielectric Constant: ASTM D 150 (3.29 at 1000 Hz) o Dissipation Factor: ASTM D150 (<0.0005 at 1000 Hz) o Volume Resistivity: ASTM D257 (1.03
- 10A15 ohm-cm) o Surface Resistivity: ASTM D257 (5.76
- 10A13 ohm)
" Surface coating applied over the metallic substrate and any repairs/contouring o Compressive Strength: ASTM D695 (13000 psi) o Flexural Strength: ASTM D790 (10000 psi) o Tensile Shear Adhesion:
ASTM D1002 (mild steel 2900 psi, Brass 2200 psi, copper 2200 psi, Stainless Steel 3000 psi) 2
ATTACHMENT (1)
REQUEST FOR ADDITIONAL INFORMATION REGARDING RELIEF REQUEST RR-ISI-04-08, REVISION 1 o Hardness: ASTM D785 (Rockwell R100) o Heat distortion: ASTM D648 (264 psi fiber stress, 117 F when cured at 20 C, 208 F when cured at 100 C) o Corrosion Resistance: ASTM BI 17-73 (no sign of corrosion after 5000 hours0.0579 days <br />1.389 hours <br />0.00827 weeks <br />0.0019 months <br /> salt spray cabinet) o Dielectric Strength: ASTM D149 (32 volts/mil) o Dielectric Constant: ASTM DI50 (3.29 at 1000 Hz) o Dissipation Factor: ASTM D150 (<0.0005 at 1000 Hz) o Volume Resistivity: ASTM D257 (1.03
- 10^15 ohm-cm) o Surface Resistivity: ASTM D257 (5.76
- 10^13 ohm)
The material was qualified for the Saltwater System design conditions. These materials were not qualified for a specific service life, however as noted above they have been used for over 20 years in the Saltwater System and subsequent inspections of the material have revealed no significant degradation.
b)
The sealant will dry to a smooth hard surface.
c)
The paste grade material is troweled into place and contoured to the original surface of the ductile cast iron substrate.
The coating is applied by brushing on the surface to a film thickness of 10-15 mils. The final result will be a smooth, hard continuous surface.
d)
The backing plate will not be in direct contact with the sealant as a rubber gasket will be installed between the backing plate and the sealant. An EPDM gasket is then placed over the backing plate followed by the installation of four retaining bands. The application of a high pressure expansion force on the retaining bands will ensure good contact of the sleeve assembly against the sealant is accomplished.
NRC RAI No. 3:
On page 6 of RR-ISI-04-08, Rev. 1, you stated that the proposed repair will not apply to through-wall degradation. Discuss the minimum wall thickness of the pipe base metal and at the bell-spigot joint beyond which the proposed seal repair would not be applicable.
On page 6 of RR-ISI-04-08, Revision 1, it states that the repair system will be applied in cases where degradation has resulted in saltwater piping wall thickness falling below minimum design wall thickness values due to corrosion on the inner diameter of the piping. It also states that the repair system will not apply to through wall degradation. Therefore, as long as there is no through wall degradation, this repair will apply to all pipe wall thinnings due to corrosion on the inner diameter.
NRC RAI No. 4: to RR-ISI-04-08, Rev. 1 specifies two regulatory commitments to inspect one installed seal after two operating cycles for Unit No. 1 and 2, respectively. The NRC stafffinds that these commitments are an essential aspect of whether or not the proposed alternative should be authorized The NRC's Office of the General Counsel has indicated to the NRC staff that regulatory commitments on the part of licensees may not be used in NRC safety evaluations as a basis for meeting the criteria contained in Title 10 of the Code of Federal Regulations Section 50.555a(a)(3). The Office of the General Counsel has indicated that when regulatory commitments must be relied upon in authorizing an alternative to the ASME Code, the safety evaluation written should clearly state that the commitment is a condition of the authorized alternative. Once the regulatory commitment has been deemed to be a condition of the 3
ATTACHMENT (1)
REQUEST FOR ADDITIONAL INFORMATION REGARDING RELIEF REQUEST RR-ISI-04-08, REVISION 1 alternative, the commitment becomes a condition of the NRC's authorization. Please confirm that Calvert Cliffs understands that the regulatory commitments provided as part of this request will become conditions of the authorized alternative.
In the text of RR-ISI-04-08, Revision 1, Calvert Cliffs stated that "Calvert Cliffs will disassemble the first installed repair system and inspect the degraded area after two operating cycles." Calvert Cliffs indicated that any additional repair system (sleeve assembly) installed will be visually inspected every other refueling outage.
Because this proposed alternative will only be implemented should we discover applicable degraded conditions during future inspections, the intent of the two commitments listed in RR-ISI-04-08, Revision 1, was to ensure we tracked the disassembly of the first installed sleeve assembly regardless of whether it was installed on Unit 1 or Unit 2. It was not meant to signify that we would disassemble the first installed sleeve assembly on each unit however, in hindsight, the listing of two commitments was confusing.
Consistent with the text in RR-ISI-04-08, Revision 1, the commitment listed in Attachment (2) will provide adequate assurance that the initially installed sleeve assembly (regardless of which unit it is installed in) will undergo a disassembly/inspection following the second cycle after it is installed.
Calvert Cliffs understands the regulatory commitment listed in Attachment (2) will become a condition of the authorized alternative. This regulatory commitment (condition of the authorized alternative) will be tracked within Calvert Cliffs' action item tracking system.
NRC RAI No. 5:
In the NRC staff's previous review of this proposed alternative, it considered only sections of straight pipe and not joints between those sections. As a result, the NRC staff did not consider the potential for axial, angular, or rotational motion between opposite ends of the repair.
a)
Given the potential for these motions, due to changes in the soil around the pipe caused by changes in temperature, moisture, or seismic activity, especially in light of the fact that the sealant material is applied over exactly the length of the repair gasket, please discuss the potential for cracks to develop in the sealant which allow water ingress into the joint.
b)
Please discuss the potential for and results of a seismic event of sufficient magnitude to cause sliding between pipe segments along the bell and spigot joint, which appears to be constrained only by gasket friction, addressing whether the motion may exceed the ability of the repair to expand or contract.
c)
Would such an event result in the rubber gasket washing downstream and plugging safety related equipment?
a)
Prior to installation of the sleeve, the cement lining for the entire length of the sleeve assembly will be removed and the sealant will be applied to the entire bare metal surface. However, if the repair sleeve is installed over a joint, the sealant will not be applied to the small gap that exists between the bell and spigot as the sealant is not intended to be a seal across a joint between two pipes.
Currently the cement liner also does not go over the gap.
If the sealant were to be applied on the gap between the bell and spigot at the joint, a relative movement could crack it. Since the sealant will not be applied on the gap at the pipe joint, there is no concern of cracking of the sealant. As discussed below in section b, the relative movement of 4
ATTACHMENT (1)
REQUEST FOR ADDITIONAL INFORMATION REGARDING RELIEF REQUEST RR-ISI-04-08, REVISION 1 the pipe at the joint due to a seismic event is expected to be very small. We also do not anticipate for the soil to shift due to changes in temperature and moisture. Therefore excessive flexing of the pipe to cause the sealant to crack is highly unlikely. The sealant has a lower modulus of elasticity than the pipe, and as such, it will flex with the pipe without cracking.
The sealant is applied to protect the pipe from corrosion should saltwater leak past the EPDM gasket. The EPDM gasket is designed to prevent saltwater ingress under the sleeve. The EPDM gasket is held in place firmly by retaining bands located at each end and is designed to provide a leak tight seal.
Therefore, leakage past the EPDM gasket is not expected and therefore, the likelihood of corrosion is very remote even if the sealant cracks.
b)
The pipe joint consists of a bell and spigot configuration with fittings that connect to compress the joint gasket. Bolting between the gland and the bell provides a leak tight joint and also develops a friction fit to inhibit differential axial or rotational pipe movement.
The subject pipe is located under the North Service Building and Turbine Building at Calvert Cliffs. Under the North Service Building, the piping is run to the west of the Intake Structure, through compacted soil fill, placed above the Circulating Water System piping. This construction contains the saltwater piping to where it is not adversely affected by seismic ground motions.
Under the Turbine Building, the saltwater piping and its surrounding compacted fill is contained below the Turbine Building floor slab, but above and within the base of the four walls of the Turbine Building. The piping has been in place for over 40 years. Therefore, during a seismic event the saltwater piping and its surrounding soil is expected to move together with no or, at worst, minimal relative axial or angular movements. There are concrete thrust barriers installed at each elbow where a straight pipe changes directions. These concrete thrust barriers further prevent any relative movement of the pipe in the axial direction. Therefore, the sleeve assembly repair is not likely to be impacted by a seismic event.
c)
The likelihood of the EPDM gasket to be washed away is very remote. There are four retaining bands in each assembly to keep the gasket in place.
The calculation indicates one band will provide sufficient force to maintain the gasket in position. The potential impact of loose parts of the sleeve assembly was discussed in our response to Request for Additional Information No. 18 of Reference 1.
NRC RAI No. 6:
The NRC staff notes that post-installation pressure testing was not included in RR-ISI-04-08, Rev. 1. In its May 13, 2013, letter, in response to the NRC request for additional information RAI-19, the licensee provided the requirements for the post-installation pressure testing for RR-ISI-04-08 (ADAMS Accession No. ML13141A270). Discuss whether the post-installation pressure testing for RR-ISI-04-08, Rev. I will be performed the same as for RR-ISI-04-08.
The post-installation pressure testing for RR-ISI-04-08, Revision 1 remains exactly the same as was described in Calvert Cliffs response (Reference 1) to the NRC's RAI-19.
5
ATTACHMENT (1)
REQUEST FOR ADDITIONAL INFORMATION REGARDING RELIEF REQUEST RR-ISI-04-08, REVISION 1 NRC RAI No. 7:
The NRC staff notes that the duration for the proposed alternative was not included in RR-ISI-04-08, Rev. 1.
In its November 13, 2013, letter, the NRC authorized RR-ISI-04-08 for the fourth inservice inspection interval which ends on June 30, 2019for both units (ADAMS Accession No. ML13297A293).
Discuss whether the duration for RR-ISI-04-08, Rev. 1 is also applicable for the fourth inservice inspection interval which ends on June 30, 2019ifor both units.
The duration for the proposed alternative did not change as a result of RR-ISI-04-08, Revision 1. Once approved, the proposed alternative duration would be for the remainder of Calvert Cliffs Fourth Ten Year Inservice Inspection Interval.
Reference
- 1.
Letter from J. J. Stanley (CCNPP) to Document Control (NRC), dated May 17, 2013, Response to Request for Additional Information, Re: Calvert Cliffs Relief Request RR-ISI-04-08 (TAC Nos. MF0568 and MF0569) 6
ATTACHMENT (2)
REGULATORY COMMITMENT Calvert Cliffs Nuclear Power Plant, LLC February 14, 2014
ATTACHMENT (2)
REGULATORY COMMITMENT The table below lists the action committed to in this submittal. Any other statements in this submittal are provided for information purposes and are not considered to be regulatory commitments.
Regulatory Commitment Date Disassemble/inspect the first installed sleeve assembly (approved in During refueling outage RR-ISI-04-08, Revision 1), after two operating cycles, following two operating cycles after installation of sleeve assembly I