05000277/LER-2016-001, Regarding Leak in High Pressure Service Water Pipe Results in Condition Prohibited by Technical Specifications

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Regarding Leak in High Pressure Service Water Pipe Results in Condition Prohibited by Technical Specifications
ML16316A114
Person / Time
Site: Peach Bottom Constellation icon.png
Issue date: 11/11/2016
From: Pat Navin
Exelon Generation Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
CCN: 16-102 LER 16-001-00
Download: ML16316A114 (5)


LER-2016-001, Regarding Leak in High Pressure Service Water Pipe Results in Condition Prohibited by Technical Specifications
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded

10 CFR 50.73(a)(2)(viii)(A)

10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition

10 CFR 50.73(a)(2)(ix)(A)

10 CFR 50.73(a)(2)(iv)(A), System Actuation

10 CFR 50.73(a)(2)(x)

10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor

10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat

10 CFR 50.73(a)(2)(v), Loss of Safety Function

10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown

10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications

10 CFR 50.73(a)(2)(vii), Common Cause Inoperability

10 CFR 50.73(a)(2)(i)
2772016001R00 - NRC Website

text

Exelon Generation November 11, 2016 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

Peach Bottom Atomic Power Station (PBAPS) Unit 2 Renewed Facility Operating License No. DPR-44 NRC Docket No. 50-277 Licensee Event Report (LER) 2-16-001 10CFR 50.73 Enclosed is a Licensee Event Report concerning a condition prohibited by Technical Specifications (TS) resulting from a pipe leak in the High Pressure Service Water system. In accordance with NEI 99-04, the regulatory commitment contained in this correspondence is to restore compliance with the regulations. The specific methods that have been planned to restore and maintain compliance are discussed in the LER. If you have any questions or require additional information, please do not hesitate to contact Jim Armstrong, Site Regulatory Assurance Manager, at 717-456-3351.

Sincer;;~

Patrick D. Navin Plant Manager Peach Bottom Atomic Power Station PDN/dnd/IR 2704854 Attachment cc:

US NRC, Administrator, Region I US NRC, Senior Resident Inspector R. R. Janati, Commonwealth of Pennsylvania S. Gray, State of Maryland B. Watkins, PSE&G, Financial Controls and Co-owner Affairs CCN: 16-102

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2018 (06-2016)

Estimaled burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.

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Reported lessons learned are incorporated into the licensing process and fed back to industry.

LICENSEE EVENT REPORT (LER)

Send comments regarding burden estimate to the FOIA, Privacy and Information Collections

- ~.

Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail

~

rfl (See Page 2 for required number of digits/characters for each block}

to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of lnfomnation and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a (See NUREG-1022, R.3 for instruction and guidance for completing this form means used to impose an infomnation collection does not display a currently valid OMB control htli;i://www.nrc.gov/reading-rm/doc-i;;ollections/nuregs/staff/sr1022/r3/)

number, the NRC may not conduct or sponsor, and a person is not required to respond to, the infomnation collection.

3. PAGE Peach Bottom Atomic Power Station Unit 2 05000277 1 OF 4
4. TITLE Leak in High Pressure Service Water Pipe Results in Condition Prohibited by Technical Specifications
5. EVENT DATE
6. LER NUMBER
7. REPORT DATE
8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.

MONTH DAY YEAR Peach Bottom APS Unit 3 05000278 FACILITY NAME DOCKET NUMBER 09 12 16 2016 - 001 0

11 11 16

9. OPERATING MODE
11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)

D 20:2201(b)

D 20.2203(a)(3)(i)

D 50.73(a)(2)(ii)(A)

D 50.73(a)(2)(viii)(A) 1 D

20.2201(d)

D 20.2203(a)(3)(iiJ D

50.73(a)(2)(ii)(B)

D

50. 73(a)(2)(viii)(B)

D 20.2203(a)(1)

D 20.2203(a)(4)

D so.13(a)(2)(iii)

D 50.73(a)(2)(ix)(A)

D 20.2203(a)(2)(i)

D 50.36(c)(1)(i)(A)

D 50.73(a)(2)(iv)(A)

D 50.73(a)(2)(x)

10. POWER LEVEL D

20.2203(a)(2)(ii)

D 50.36(c)(1 )(ii)(A)

D 50.73(a)(2)(v)(A)

D 13.11(a)(4)

D 20.2203(a)(2)(iii)

D so.3a(c)(2)

D 50.73(a)(2)(v)(B)

D 13.11(a)(s)

D 20.2203(a)(2)(iv)

D so.4a(a)(3)(ii)

D 50.73(a)(2)(v)(C)

D 13.77(a)(1) 100%

D 20.2203(a)(2)(v)

D 50.73(a)(2)(i)(A)

D 50.73(a)(2)(v)(D)

D 73.77(a)(2)(i)

D 20.2203(a)(2)(vi)

~ 50.73(a)(2)(i)(B)

D 50.73(a)(2)(vii)

D 73.77(a)(2)(ii)

D 50.73(a)(2)(i)(C)

D OTHER Specify in Abstract below or in SEQUENTIAL NUMBER 001 REV NO.

0 The emergency heat sink per TS 3.7.3.B due to potential for loss of inventory (applies to both Units 2 and 3)

The pipe was replaced and the affected equipment was restored to an operable status on 8/18/16 at 0610 hours0.00706 days <br />0.169 hours <br />0.00101 weeks <br />2.32105e-4 months <br />. The elapsed time from the discovery of the failure to when the equipment was returned to service was approximately 45 hours5.208333e-4 days <br />0.0125 hours <br />7.440476e-5 weeks <br />1.71225e-5 months <br /> and 40 minutes.

Analysis of the Event

Initial evaluation of the flaw could not determine if the pipe would have failed during a seismic event.

More detailed modeling of the pipe from its connection on the 18" diameter HPSW line to the first anchor point on the wall determined that seismic stresses could have caused the crack to propagate and result in a complete fracture of the pipe. This conclusion was reached on 9/12/16 and is considered to be the time at which a reportable event was identified. It is unknown at what time the crack developed into the as-tound condition, however it is likely that it existed for a period of time greater than the TS required completion time for the systems to be restored to an operable status (7 days for each condition). Since the condition existed for a period of time longer than the TS required completion time, the condition resulted in a condition prohibited by TS and is being reported pursuant to 10CFR 50.73(a)(2)(i)(B).

Cause of the Event

To determine the cause of the crack, the section of the pipe and the socket weld were sent to an off-site lab for failure analysis. The cracking initiated at the toe of the weld on the outer diameter of the pipe and propagated in one general direction through the pipe wall. The fracture surface was examined by scanning electron microscopy and had transgranular features which are typical of fatigue. There were no material anomalies at the fracture origins and the weld appeared to be of generally good quality. The analysis concluded that the leak was caused by fatigue cracking caused by cyclic loading conditions, such as vibration.

The pipe was anchored to the wall a short distance from its connection to the 18" diameter HPSW line.

This design did not adequately account for vibration in the HPSW line, which resulted in bending stresses in the 1" pipe at the toe of the fillet weld connection to the half coupling. In addition, a 2: 1 weld was not used with the socket weld. The current standard for fillet welds on small bore piping subject to vibration is to use a weld with a length to depth ratio of 2:1 in order to mitigate stress from vibration. A contributing cause is that the pipe appeared to have been slightly distorted in the downward direction.

Corrective Actions

The pipe was replaced between the 18" HPSW pipe and the first valve. A 2: 1 weld was utilized at the socket to mitigate vibration impacts. The configuration of the 1" pipe is used at a total of 16 locations at the plant for the supply and return lines for radiation monitors for the HPSW system. All were visually inspected to determine if similar flaws existed on the other lines. No flaws were identified. Non-YEAR 2016 SEQUENTIAL NUMBER 001 destructive examinations have been scheduled to obtain additional information on the condition of the piping.

Previous Similar Occurrences REV NO.

0 Since the modification in 1994 that installed the radiation monitors and associated piping, there have been no other documented cases of leakage from this piping. Page _4_ of ___!_