NL-17-1769, Proposed ISI Alternative FNP-ISI-ALT-22 Implementation of Code Case N-786-1

Proposed ISI Alternative FNP-ISI-ALT-22 Implementation of Code Case N-786-1

ML17299A685
Person / Time
Site:	Farley
Issue date:	10/24/2017
From:	Hutto J Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-17-1769
Download: ML17299A685 (8)

Text

~ Southern Nuclear 40 Inverness Center Parkway Post Office Box 1295 Birmingham, AL 35242 OCT 2 4 2017 205 992 5000 tel 205 992 7601 fax Docket Nos.: 50-348 NL-17-1769

. 50-364 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Joseph M. Farley Nuclear Plant Units 1&2 Proposed ISi Alternative FNP-ISl-ALT-22 Implementation of Code Case N-786-1 Ladies and Gentlemen:

Pursuant to 10 CFR 50.55a(z)(2), Hardship without a Compensating Increase in Quality and Safety, Southern Nuclear Operating Company (SNC) hereby requests Nuclear Regulatory Commission (NRC) approval of Alternative FNP-ISl-ALT-22 for the use of American Society of Mechanical Engineers (ASME) Code Case N-786-1, for Farley Nuclear Plant (FNP) Units 1 and 2.

Alternative FNP-ISl-ALT-22, Code Case N-786-1 permits installation of technically sound, long term repairs in the form of full-structural Type B reinforcing sleeves for piping systems.

To support work planning and preparation, SNC requests that the NRC approve the proposed alternative by November 1, 2017.

This letter contains no NRC commitments. If you have any questions, please contact Ken McElroy at 205.992.7369.

Respectfully submitted,

~

J. J. Hutto Regulatory Affairs Director JJH/kgl/cg

Enclosure:

Proposed Alternative FNP-ISl-ALT-22 cc: Regional Administrator, Region II NRR Project Manager - Farley Nuclear Plant Senior Resident Inspector - Farley Nuclear Plant RTYPE: CFA04.054

Joseph M. Farley Nuclear Plant Unit 1 and 2 Proposed ISi Alternative FNP-ISl-ALT-22 Implementation of Code Case N-786-1 Enclosure Proposed Alternative FNP-ISl-ALT-22

Enclosure to NL-17-1769 Proposed Alternative FNP-ISl-ALT-22 10 CFR 50.55a Request No. FNP-ISl-ALT-22 Implementation of Code Case N-786-1 Farley Nuclear Plant Units 1&2 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(2)

Hardship without a Compensating Increase in Qualify and Safety

1. ASME Code Component(s) Affected This ISi alternative applies to all ASME Class 2 and 3 carbon steel piping systems at Farley Nuclear Plant, Units 1 and 2 (FNP), with less than or equal to 200°F (93°C) and less than or equal to 275 psig (1.9 MPa) for maximum operating conditions.

2. Requested Approval Date Approval is requested by November 1, 2017.

3. Applicable Code Edition and Addenda

The code of record for the Farley Nuclear Plant (FNP), Units 1 and 2, fourth ten-year lnservice Inspection (ISi) interval (12/1/2007- scheduled to end 11/30/2017) is ASME Section XI, 2001 Edition through the 2003 Addenda (ASME Section XI) (Reference 1).

4. Applicable Code Requirements The Editions/Addenda of ASME Section XI for which the alternative is requested is the 2001 Edition through the 2003 Addenda. Subsection IWA-4000 of this Edition and Addenda provide requirements for welding, brazing, metal removal, and installation of repair/replacement activities.

5. Reason for Request

IWA-4000 requires replacement or internal weld repair of wall thinning conditions resulting from degradation to be in accordance with the Owner's' Requirements and the original or later Construction Code. However, the repair and replacement provisions of IWA-4000 cannot always be utilized when degradation or leakage is identified. Other approved alternative repair or evaluation methods are not always practicable because of reduced wall thickness and/or moisture issues.

One reason for this request is to permit installation of technically sound repairs to provide adequate time for evaluation, design, material procurement, planning, and scheduling of an appropriate permanent repair or replacement of the defective piping, considering the impact on system availability, maintenance rule applicability, and availability of the replacement materials. This would be addressed with either a Type A or partial-structural Type B reinforcing sleeve for one operating cycle.

The other reason is to permit installation of long-term repairs in the form of full-structural Type B reinforcing sleeves for locally degraded portions of piping systems. The design, construction, and inservice monitoring of such sleeves provide a technically sound

• equivalent replacement for the segment of piping that is encompassed, comparable to or exceeding the level of quality and safety associated with a permanent ASME Code repair or replacement E-1

Enclosure to NL-17-1769 Proposed Alternative FNP-ISl-ALT-22 In either case, without this repair option, compliance with the specified requirements of IWA-4000 could in some cases necessitate taking a system out of service, resulting in extended Technical Specification actions and higher risks associated with loss of safety, system availability. In other cases, plant shutdown would be necessary, resulting in higher risks associated with an unnecessary plant transient and loss of safety system availability as compared to maintaining the plant online.

All other ASME Code Section XI requirements for which relief is not specifically requested will remain applicable, including third-party review by the Authorized Nuclear lnservice Inspector.

6. Proposed Alternative and Basis for Use Pr.oposed Alternative Pursuant to 10 CFR 50.55a(z)(2), FNP proposes to implement the requirements of Code Case N-786-1 for repair of degradation in Class 2 and 3 carbon steel piping systems with less than or equal to 200°F (93°C) and less than or equal to 275 psig (1.9 MPa) for maximum operating conditions, resu.lting from mechanisms such as localized erosion, corrosion, cavitation, or pitting, but excluding conditions involving any form of cracking.

These types of defects are typically identified by small leaks in the piping system or by pre-emptive, non-Code required ultrasonic thickness measurements performed to monitor for degradation mechanisms.

Basis for Use The alternative repair technique described in Code Case N-786-1 involves the application of either Type A or Type B full encirclement sleeve halves welded together with full penetration longitudinal seam welds to reinforce the structural integrity in the degraded area. In the case of Type B reinforcing sleeves, the ends are also welded to the piping in order to restore or maintain pressure integrity. This repair technique will be used when it is determined that the repair method is suitable for the particular defect or degradation being resolved without flaw removal.

The Code Case requires that the cause of the degradation be determined, and that the extent and rate of degradation in the piping be evaluated to ensure there are no other unacceptable locations within the surrounding area that could affect the integrity of the repaired piping. Any areas showing signs of degradation will be included in the Owner's plan for thickness monitoring of full-structural Type B reinforcing sleeves. The area of evaluation will be dependent on the degradation mechanism present, but will extend at least 0.75"RTnom ("R" and "Tnam" are the radius and nominal thickness of the pipe, respectively) beyond the edge of any 'sleeve attachment weld, as required by the Code Case. If the cause of the degradation is not determined, the maximum permitted service life of any reinforcing sleeve will be the time until the next refueling outage.

"Full-structural Type B" *means the sleeve and attachment welds alone maintain full capability to withstand structural (mechanical) and pressure loading for which the piping is presently designed without need for additional support or reinforcement, and without reliance on any of the piping that is encased by the sleeve. Type A and partial-structural Type B sleeves rely on the encased underlying piping to provide some structural (mechanical) and/or pressure retaining integrity.

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Enclosure to NL-17-1769 Proposed Alternative FNP-ISl-ALT-22 Type B reinforcing sleeves may be applied to leaking systems by installing a gasket or sealant between the sleeve and the pipe as permitted by the Code Case, and then clamping the reinforcing sleeve halves to the piping prior to welding. If welding of any type of sleeve occurs on a wet surface, the maximum permitted life of the sleeve will be the time until the next refueling outage.

A baseline thickness examination will be performed for completed full-structural Type B reinforcing sleeves, attachment welds, and surrounding areas, followed by similar thickness monitoring at a minimum of ever'J refueling outage after installation. Full-

. structural Type B sleeves shall be removed prior to infringing upon design minimum wall thickness.

Type A and partial-structural Type B reinforcing sleeves completely encompass the degraded areas, are designed to accommodate predicted maximum degradation, and must be removed no later than the next refueling outage. The Code Case requires that these temporary sleeves be visually monitored for evidence of leakage at least monthly.

If the areas containing the sleeves are not accessible for direct observation, monitoring

• shall be accomplished by visual assessment of surrounding areas or ground surface areas above reinforcing sleeves on buried piping, or by monitoring of leakage collection systems, .if available.

• FNP implementation of Code Case N-786-1 will include the following additional restrictions and clarifications:

1) When gasket material is used in accordance with paragraph 4(b) of the Code Case (water backed applications), SNC will also require removal of any residual moisture by heating prior to welding.

2) Regarding paragraph 8(c) and 8(c)(1) of the Code Case, FNP will implement the thickness monitoring inspections of full-structural Type B sleeves at every refueling outage, and will schedule more frequent thickness monitoring, when appropriate based on degradation rates that are calculated using the reductions in thicknesses observed between scheduled thickness monitoring inspections.

3) Sections 1, 3, 5, and 6 of the Code Case specify that materials, design, installation, and examination of reinforcement sleeves shall be performed in accordance with the Construction Code or ASME Section Ill applicable to FNP. As allowed by IWA-4200 and IWA-4411, later Editions and Addenda of the Construction Code or ASME Section Ill may be used provided any required reconciliations are performed. However, only Editions/Addenda of ASME Section Ill that have been approved by the NRG in 10 CFR 50.55a will be used.

4) FNP performs repair/replacement activities in accordance with a Repair/Replacement Program based on the 2001 Edition I 2003 Addenda of ASME Section XI for the current Inspection Interval. Therefore, this Edition/Addenda of ASME Section XI will be used by Farley Nuclear Plant whenever the Code Case refers to IWA-4000.

5) If a buried piping system carrying radioactive fluid is repaired using this alternative, FNP will monitor for radioactive fluid leakage in accordance with the standard plant monitoring practices for all buried piping containing radioactive fluids. FNP is committed to implementation of Nuclear Energy Institute (NEI) 07-07, "Industry Ground Water Protection Initiative - Final Guidance Document," dated August 2007, in addition to monitoring in accordance with ASME Code Case N-786-1.

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Enclosure to NL-17-1769 Proposed Alternative FNP-ISl-ALT-22 Code Case N-786-1 includes requirements for incorporating actual measured or estimated corrosion rates in the design of all reinforcing sleeves. For all sleeves, the initial degradation rate selected for design shall be equal to or greater than two (2) times the maximum rate observed at the location of the repair. If the degradation rate for *that location is unknown, an initial degradation rate of four (4) times the estimated maximum degradation rate for that or a similar system at the same plant site for the same degradation mechanism shall be. applied. If both the degradation rate for that location and the cause of the degradation are not *c_onclusively determined, an initial degradation rate of four (4) times the maximum degradation rate observed for all degradation mechanisms for that system or a similar system at the same plant site shall be applied.

In addition, the Code Case imposes compensatory measures to account for any uncertainties in the corrosion rates used, thus providing reasonable assurance that structural integrity and leakage integrity will be maintained. These measures include limiting the design life of Type A and partial-structural Type B sleeves to a maximum of one refueling cycle, and requiring on-going monitoring of full-structural Type B sleeves as follows:

• For full-structural Type B reinforcing sleeves including their partial penetration attachment welds and surrounding areas, the Code Case requires that a baseline thickness examination be performed followed by similar thickness monitoring inspections at a minimum of every refueling outage for the life of the repair. More frequent thickness monitoring examinations will be scheduled if maximum degradation rates observed during these inspections indicate that the design thickness required by the Construction Code or ASME Section Ill will be infringed upon prior to the next scheduled monitoring activity.

• Type A and partial-structural Type B reinforcing sleeves completely encompass the degraded areas, are designed to accommodate maximum predicted degradation, and must be removed no later than the next refueling outage. The Code Case requires that they be visually observed at least once per month to monitor for evidence of leakage. If the areas containing these types of sleeves are not accessible for direct observation, then monitoring will be accomplished by visual assessment of surrounding areas, or ground surface areas above such sleeves on buried piping, or by monitoring of leakage collection systems, if available.

When used on buried piping, the area of full-structural Type B reinforcing sleeves must be physically accessible for the required examinations (both visual and ultrasonic) which could necessitate installation of removable barriers at the repair location in lieu of backfilling the pipe at that location. For Type A and partial-structural Type B reinforcing sleeves installed on buried piping, the monitoring will be based on visual assessment as discussed above.

Code Case N-786-1 restricts application of reinforcing sleeves to pipe and welded fittings, prohibiting their application on pumps, valves, expansion joints. vessels, heat exchangers, tubing, flanges, flanged joints, socket welded or threaded joints, or branch connection welds. In addition, the Code Case only permits branch connections to be installed on Type B reinforcing sleeves when required for filling or venting purposes during installation or leakage testing of the sleeve, and restricts such connections to Nominal Pipe Size (NPS) 1" or smaller in size.

Code Case N-786-1 was approved by ASME Board on Nuclear Codes and Standards in January, 2015. However, it has not been incorporated into Regulatory Guide 1.147, E-4

Enclosure to NL-17-1769 Proposed Alternative FNP-ISl-ALT-22 "lnservice Inspection Code Case Acceptability, ASME Section XI, Division 1," and, thus, is not available for application at nuclear power plants without specific NRG approval.

7. Duration of Proposed Alternative Use of the proposed alternative is requested for the duration of the ISi intervals identified in Section 3.

Code Case N-786-1, paragraphs 3.1 (a) and 3.1 (b)(2) require that Type A and partial-structural Type B reinforcing sleeves, including those installed during refueling outages or any time during an operating cycle, shall not remain in service beyond the next refueling outage, when a permanent repair or replacement must be performed. FNP will comply with this requirement with the following clarifications:

• Reinforcing sleeves installed before the end of the 10-year ISi interval will be removed during the next refueling outage after installation, even if that refueling outage occurs after the end of the 10-year ISi Interval. In this case, absent detrimental defects or degradation, duration of the proposed alternative would be until the first refueling outage after the end date of the ISi Interval for FNP. *

• Some piping systems are required to be functional and cannot be repaired during refueling outages. The repair of this piping can only be performed when the plant is operating. For this unique case, Type A and partial-structural Type B reinforcing sleeves will be removed prior to the next refueling outage unless specific regulatory relief is obtained. It should be noted that the removal of the reinforcing sleeve might extend beyond the end date of the ISi Interval but would be removed prior to the next refueling outage.

Full-structural Type B reinforcing sleeves may remain in-service for the design life of the repair as specified in Code Case N-786-1, paragraph 3.1(b)(1). *FNP commits to continued inservice thickness monitoring and evaluation as required for any full-structural Type B sleeve remaining installed.

8. Precedents

1) Exelon Generation Company, LLC, Safety Evaluation for Use of Code Case N-786, July 31, 2014; Adams Accession No. ML141758593.

2) Entergy Operations Inc. and Entergy Nuclear Operations, Inc. (Entergy), Safety Evaluation for Use of Code Case N-786-1, June 6, 2016, Adams Accession No. ML16096A269.

Several plants have received approval for fuither ASME Code Case N-786 or N-786-1.

9. References

1) American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI, Rules for lnservice Inspection of Nuclear Power Plant Components, 2001 Edition, through 2003 Addenda, the American Society of Mechanical Engineers, New York.

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Enclosure to NL-17-1769 Proposed Alternative FNP-ISl-ALT-22

2) ASME Code Case N-786-1, "Alternative Requirements for Sleeve Reinforcement of Class 1 and 3 Moderate-Energy Carbon Steel Piping Section XI, Division 1," Dated:

December 31, 2014.

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