HNP-12-099, Relief Request I3R-10 Spent Fuel Pool Cooling Piping Inservice Inspection Program - Third Interval

Relief Request I3R-10 Spent Fuel Pool Cooling Piping Inservice Inspection Program - Third Interval

ML12313A442
Person / Time
Site:	Harris
Issue date:	11/08/2012
From:	Corlett D Carolina Power & Light Co, Duke Energy Corp
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
HNP-12-099
Download: ML12313A442 (8)

Text

David H. Corlett Supervisor, Licensing/Regulatory Programs Harris Nuclear Plant 5413 Shearon Harris Rd New Hill NC 27562-9300 919-362-3137 November 8, 2012 10 CFR 50.55a Serial: HNP-12-099 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Shearon Harris Nuclear Power Plant, Unit 1 Docket No. 50-400

Subject:

Relief Request I3R-10 Spent Fuel Pool Cooling Piping Inservice Inspection Program - Third Interval Ladies and Gentlemen:

Pursuant to 10 CFR 50.55a(g)(5)(iii), Carolina Power & Light Company hereby requests NRC approval of the attached relief request for the Shearon Harris Nuclear Power Plant, Unit 1 (HNP)

Inservice Inspection Program, third ten-year interval. HNP is planning to perform a code repair at the first available opportunity. Due to the time needed for design, fabrication, procurement, testing, and planning associated with the use of a mechanical plug to isolate the repair location from the spent fuel pool, it is impractical to complete the code repair during the 30 days considered typically reasonable for the repair activity. At this time, the code repair is anticipated to be performed in February 2013, but conditions beyond the control of HNP could impact that schedule. Approval is requested by January 31, 2013, which is prior to the current schedule for the code repair.

HNP proposes the following regulatory commitment upon NRC approval of the requested relief:

Frequent periodic surface inspections of no more than 30 day intervals shall be used to determine if flaws are growing and to establish the time, tallow, at which the detected flaw will reach the allowable size. The allowable size limit will assume that the length of the flaw is four times the surface length to account for the lack of information associated with volumetric characterization of the flaws.

HNP-12-099 Page 2 Please refer any questions regarding this submittal to me at (919) 362-313 7.

Sincerely,

Enclosure:

ReliefRequest I3R-10 cc: Mr. J.D. Austin, NRC Sr. Resident Inspector, HNP Ms. A. T. Billoch Colon, NRC Project Manager, HNP Mr. V. M. McCree, NRC Regional Administrator, Region II

U.S. Nuclear Regulatory Commission Relief Request I3R-10 Enclosure to HNP-12-099 Page 1 of 6 HNP-12-099 Enclosure Shearon Harris Nuclear Power Plant, Unit 1 Docket No. 50-400 Relief Request I3R-10 In Accordance with 10 CFR 50.55a(g)(5)(iii)

Inservice Inspection Impracticality Spent Fuel Pool Cooling System Inservice Inspection Program - Third Ten-Year Interval

U.S. Nuclear Regulatory Commission Relief Request I3R-10 Enclosure to HNP-12-099 Page 2 of 6

1. ASME Code Component Affected a)

Description:

Interfaces between a 12-inch stainless steel pipe and two elbows, both at the circumferential groove welds on line 3SF12-176SB-1-4.

Component: B Spent Fuel Pool Cooling Return Line To A Spent Fuel Pool Code Class: Class 3 Examination Category: D-B Code Item Number: D2.10 (Pressure Retaining Components)

System: Spent Fuel Pool Cooling Design Pressure: 100 psig Design Temperature: 200° F Size: 12 Inch Nominal Pipe Size Pipe Material: SA-312, TP304 Pipe Thickness: Schedule 40S (0.375 Nominal)

Elbow Material: SA-403, WP 304W Elbow Thickness: Schedule 40S (0.375 Nominal) b) Function:

The Fuel Pool Cooling and Cleanup System is designed to remove residual heat from the spent fuel in the fuel storage pools and to maintain water quality in the fuel storage pools, the transfer canals, and the reactor cavity.

c) Description of the flaws:

(1) A through wall leak was found on the 12-inch stainless steel pipe and elbow circumferential groove weld (weld number 1-SF-4-2-VW-6) interface on B Train Spent Fuel Pool Cooling line 3SF12-176SB-1-4. The leak is on the bottom (6 oclock position) of the weld.

(2) Three through-wall leaks were found on the 12-inch stainless steel pipe and elbow circumferential groove weld (weld number 1-SF-4-2-VW-3) interface on B Train Spent Fuel Pool Cooling line 3SF12-176SB-1-4. The leaks are at 12 oclock, 3 oclock, and 7 oclock positions of the weld.

2. Applicable Code Edition and Addenda

ASME Boiler and Pressure Vessel Code,Section XI, 2001 Edition through the 2003 Addenda.

U.S. Nuclear Regulatory Commission Relief Request I3R-10 Enclosure to HNP-12-099 Page 3 of 6

3. Applicable Code Requirement

ASME Boiler and Pressure Vessel Code, IWB-3522.1, states in part:

The following relevant conditions that may be detected during the conduct of system pressure test shall require corrective action to meet the requirements of IWB-3142 and IWA-5250 prior to continued service:

(a) Leakage from non-insulated components

4. Impracticality of Compliance Evidence of a flaw was detected by the presence of dry boric acid during performance of the ASME Section XI periodic pressure test for the B Train Unit 1 New Fuel Pool Cooling System. Through-wall leakage was confirmed in the stainless steel pipe-to-elbow weld after the weld was cleaned of boric acid and re-inspected. Leakage is being monitored by daily walkdowns which confirm that the leak rate remains negligible.

Three additional leaks were identified during subsequent walkdowns and inspections.

Leakage is being monitored by daily walkdowns which confirm that the leakrates remain negligible for these locations as well.

The portion of the piping that contains the flaws has been removed from service with respect to its design function and will not be returned to service until the code repairs are complete.

The design functions of removing residual heat from the spent fuel in the fuel storage pools and maintaining water quality in the fuel storage pools, the transfer canals, and the reactor cavity is performed using other components. However, the portion of piping that contains the flaws is not isolable from the A Spent Fuel Pool with installed components, as there are no valves between the pool and the flaw locations.

Upon discovery of the flaws, preparations were initiated to perform code repairs.

Performance of the code repair requires isolating the affected portion of piping from the spent fuel pool. A freeze seal was attempted but was insufficient to obtain the necessary isolation boundary. The plan was then revised to utilize a mechanical plug to isolate the flaw locations from the spent fuel pool. The mechanical plug will have to be designed, fabricated, procured, and tested prior to the implementation of the repair work, resulting in a significant delay from the original schedule.

The code of construction for the Spent Fuel Pool Cooling System piping is ASME Boiler and Pressure Vessel Code,Section III, 1971 Edition through Summer 1973 Addenda, Class 3 requirements (Subsection ND). Welds were constructed to provide a suitable surface for the code-required non-destructive examination (NDE). For ASME Class 3 constructed welds, the code required NDE was a surface inspection. The welds were not required to be profiled such that an ultrasonic volumetric inspection capable of characterizing flaws could be performed throughout the entire weld. No pre-service volumetric inspections were required or performed.

U.S. Nuclear Regulatory Commission Relief Request I3R-10 Enclosure to HNP-12-099 Page 4 of 6 Implementation of Code Case N-513 normally uses volumetric inspection for initial characterization of flaws, monitoring of flaw growth, and extent of condition inspections. The use of volumetric inspection is not practical because the surface conditions are not acceptable for a qualified volumetric inspection, preservice inspections were not performed, and surface profiling the welds could propagate or worsen the extent of the flaws. Therefore, volumetric inspections for flaw characterization per Code Case N-513 are not practical and the code case will not be invoked.

There are no specific Technical Specifications or Limited Conditions of Operation associated with the Spent Fuel Pool Cooling System. The Spent Fuel Pool Cooling System is a support system that could impact Technical Specification 3.9.11, Water Level - New and Spent Fuel Pools, with a requirement to restore level within four hours if level is less than 23 feet.

HNP has determined that it is impractical to complete the code repair during the 30 days typically considered reasonable for the repair activity due to the time needed for design, fabrication, procurement, testing, and planning associated with the use of the mechanical plug hardware to isolate the repair location from the spent fuel pool.

5. Burden Caused by Compliance Although the portion of the piping that contains the flaws has been removed from service for its design function, HNP can neither isolate the affected portion of piping from the spent fuel pool nor complete the code repair within 30 days of discovery due to the time needed for design, fabrication, procurement, testing, and planning associated with the use of the mechanical plug to isolate repair location from the spent fuel pool. Technical Specification 3.9.11 has a requirement to restore level within four hours if level is less than 23 feet, which makes it impractical to lower the level in the spent fuel pool to the point where the code repair could be executed without the mechanical plug.

6. Proposed Alternative and Basis for Use a) The flaw geometry shall be characterized by physical measurement. The full pipe circumference at the flaw location shall be inspected to characterize the surface length of flaws in the pipe section. The subsurface length of the flaw will be assumed to be four times the surface length for characterization purposes. The depths of the identified flaws are known to be through-wall.

b) The flaws shall be classified as planar or non-planar. The through-wall aspect supports classification as planar.

c) When multiple flaws, including irregular (compound) shape flaws, are detected, the interaction and combined area loss of flaws in a given pipe section shall be accounted for in the flaw evaluation.

d) A flaw evaluation shall be performed to determine the conditions for flaw acceptance.

The flaw evaluation shall be performed in accordance with Code Case N-513-3, Section 3. Flaw acceptance criteria shall assume that the length of the flaw is four

U.S. Nuclear Regulatory Commission Relief Request I3R-10 Enclosure to HNP-12-099 Page 5 of 6 times the surface length to account for the lack of information associated with subsurface characterization of the flaws.

e) Frequent periodic surface inspections of no more than 30 day intervals shall be used to determine if flaws are growing and to establish the time, tallow, at which the detected flaw will reach the allowable size. The allowable size limit will assume that the length of the flaw is four times the surface length to account for the lack of information associated with volumetric characterization of the flaws.

f) Leakage shall be observed by daily walkdowns to confirm the analysis conditions used in the evaluation remain valid.

g) The code repair is scheduled to be complete prior to the next refueling outage, currently scheduled for fall 2013.

Deferral of the repairs of the Spent Fuel Pool Cooling System weld flaws is acceptable based on the following:

1. Use of physical measurement of surface flaw length in lieu of volumetric inspection is satisfactory based upon the proposal to use four times the surface length of the flaw for flaw characterization, evaluation, and monitoring of flaw growth rate. This provides a conservative alternative to the use of volumetric inspections.

2. The B Spent Fuel Pool Cooling System return line to the A Spent Fuel Pool, 3SF12-176SB-1-4, has been isolated from the remaining portions of the Spent Fuel Pool Cooling System since the original leak discovery and will continue to be isolated from the remaining portions. The conservatively estimated pressure at the flaw locations is 20 psig due to head pressure (approximately 46 feet) from the A Spent Fuel Pool.

3. Ultrasonic thickness examinations were performed in the areas directly adjacent to the flawed welds. The ultrasonic examinations confirmed that there were no wall thinning concerns as all recorded readings were within manufacture tolerances from pipe wall nominal thickness.

4. Best effort ultrasonic examinations were performed to assist in determining the relative size of the indications. For weld 1-SF-4-2-VW-3, through-wall leak locations showed flaw-like characteristics and could be seen from multiple examination angles. For weld 1-SF-4-2-VW-6, no indications were identified that could be attributed to the leak.

5. Accessible large bore welds (12, 14, and 16) on the Spent Fuel Pool Cooling Systems were visually examined. There was no additional evidence of leakage on the inspected portions of piping.

6. The maximum allowable flaw lengths for both circumferential and axial planar flaws have been calculated for the 12 Stainless Steel Spent Fuel Pool Cooling Piping in accordance with the requirements of Code Case N-513-3, Paragraph 3. These calculations have been documented in Engineering Change Evaluation 88099. The

U.S. Nuclear Regulatory Commission Relief Request I3R-10 Enclosure to HNP-12-099 Page 6 of 6 calculated allowable flaw length is significantly greater than four times the surface length including consideration for multiple flaws in the same weld.

7. The current leakrate is negligible.

8. The daily visual examinations are sufficient to monitor the leakage from the flaw locations and to ensure that significant rapid flaw growth does not occur.

The proposed alternatives, (a) through (g) above, provide reasonable assurance of structural integrity. Items (a) through (d) have been completed. Item (e) will be performed monthly.

Item (f) is being performed on a daily basis.

Relief is requested from ASME Boiler and Pressure Vessel Code, IWB-3522.1.

7. Duration of Proposed Alternative The proposed alternatives shall be used until the affected weld repairs can be scheduled and implemented, no later than the next scheduled refueling outage during the fall of 2013 or November 30, 2013, whichever occurs first.

8. Regulatory Commitments HNP commits to the following effective upon NRC approval of this relief request. Any other statements in this document are provided for information purposes and are not considered to be regulatory commitments.

Frequent periodic surface inspections of no more than 30 day intervals shall be used to determine if flaws are growing and to establish the time, tallow, at which the detected flaw will reach the allowable size. The allowable size limit will assume that the length of the flaw is four times the surface length to account for the lack of information associated with volumetric characterization of the flaws. This commitment will be effective upon NRC approval of the relief request and will remain in effect until completion of the code repair.

9. Precedents A similar request for relief was approved for Catawba on July 14, 2011, ADAMS Accession Number ML11187A001.