05000387/LER-2016-019, Regarding Pressure Boundary Leakage from an Inadequate Weld Repair in Small Bore Pump Seal Vent Piping

Regarding Pressure Boundary Leakage from an Inadequate Weld Repair in Small Bore Pump Seal Vent Piping

ML16216A374
Person / Time
Site:	Susquehanna
Issue date:	08/03/2016
From:	Franke J Susquehanna, Talen Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
PLA-7505 LER 16-019-00
Download: ML16216A374 (5)

LER-2016-019, Regarding Pressure Boundary Leakage from an Inadequate Weld Repair in Small Bore Pump Seal Vent Piping

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 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)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 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) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i)
LER closed by
IR 05000387/2016004 (10 February 2017)
3872016019R00 - NRC Website

text

AUG 0 3 2016 Jon A. Franke Susquehanna Nuclear, LLC Site Vice President 769 Salem Boulevard Berwick, PA 18603 Tel. 570.542.2904 Fax 570.542.1504 Jon.Franke@TalenEnergy.com U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 SUSQUEHANNA STEAM ELECTRIC STATION LICENSEE EVENT REPORT 50-387/2016-019-00 UNIT 1 LICENSE NO. NPF-14 PLA-7505 TALEN ~

ENERGY 10 CFR 50.73 Docket No. 50-387 Attached is Licensee Event Repmi (LER) 50-387/2016-019-00. The LER reports a condition concerning Reactor Coolant Pressure Boundary leakage. This condition was determined to be reportable in accordance with 10 CFR 50.73(a)(2)(ii)(A), 10 CFR 50.73(a)(2)(i)(A), and 10 CFR 50.73(a)(2)(i)(B), as a condition resulting in a principal safety barrier degradation, plant shutdown required by Technical Specifications, and as a condition prohibited by Technical Specifications.

There were no actual consequences to the health and safety of the public as a result of this event.

This letter contains no new regulatory commitments.

Attachment: LER 50-387/2016-019-00 Copy:

NRC Region I Mr. J. E. Greives, NRC Sr. Resident Inspector Ms. T. E. Hood, NRC Project Manager Mr. M. Shields, PA DEP/BRP

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 1013112018 (11-2015)

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

~*PAGE Susquehanna Steam Electric Station Unit 1 05000387 1 of 4

4. TITLE Pressure Boundary Leakage from an Inadequate Weld Repair in Small Bore Pump Seal Vent Piping

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED YEAR l SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.

MONTH DAY YEAR 05000 FACILITY NAME DOCKET NUMBER 06 06 2016 2016

- 019

- 00 6~ 03 2016 05000

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)

I:8J 50.73(a)(2)(ii)(A)

D 50.73(a)(2)(viii)(A) 2 D 2D.2201(d}

D 20.2203(a)(3)(ii)

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 50.73(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) 0 50.36(c)(1 )(ii)(A)

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

D 73.71(a)(4) 009 D 20.2203(a)(2)(iii)

D 50.36(c)(2)

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

D 73.71(a)(5)

D 20.2203(a)(2)(iv)

D 50.46(a)(3)(ii)

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

D 73.77(a)(1)

D 20.2203(a)(2)(v)

I:8J 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)

I:8J 50.73(a)(2)(i}(B}

D 50.73(a)(2)(vii)

D 73.77(a)(2}(ii) 0 50.73(a)(2)(i)(C) 0 OTHER Specify in Abstract below or in

CAUSE OF EVENT

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

2. DOCKET NUMBER

3. LER NUMBER YEAR I

SEQUENTIAL I

REV NUMBER NO.

05000387 2016

- 019

- 00 The cause of the Reactor Coolant Pressure Boundary leakage at the Reactor Recirculation Pump B Lower Seal Vent Line was determined to be a result of a crack in the pipe-to-union weld on the pump side of the connection. Based on investigation and laboratory testing, the crack was determined to have initiated and propagated as a result of an undetectable lack of fusion at the weld root along with an unrecognized cyclic or vibratory loading. Additionally, during the previous repairs on the pipe-to-union weld location, cold-working grinding was performed, inducing a compressive stress which contributed to crack initiation.

ANALYSIS/SAFETY SIGNIFICANCE

Technical Specification Limiting Condition for Operation (LCO) 3.4.4, RCS Operational Leakage, requires zero pressure boundary leakage and less than or equal to 5 gallons per minute (GPM) unidentified drywell leakage when operating in Modes 1, 2 and 3. At the time of discovery of the Reactor Coolant Pressure Boundary leak on the Lower Seal Vent Line, Unit 1 was in Mode 2. As such, the associated condition for Technical Specification (TS) 3.4.4 was not met, requiring operator actions to initiate a plant shutdown.

The 5 GPM Technical Specification limit for unidentified leakage is a small fraction of the calculated flow from a critical crack in the primary system piping. Crack behavior from experimental programs show that leakage rates of hundreds of gallons per minute will precede crack instability. As such, the Technical Specification limit allows time for corrective action to be taken before the Reactor Coolant Pressure Boundary could be significantly compromised. Prior to commencing the down-power to investigate the increasing trend in unidentified drywell leakage, the actual leakage was approximately 0.53 GPM. There was no evidence available to plant operators at the time to substantiate that leakage was from the Reactor Coolant Pressure Boundary. Based on the visual inspection and the size of the crack on the Lower Seal Vent Line, the leakage from this location was likely the primary contributor to the unidentified drywell leakage. Given the actual unidentified drywell leakage prior to shutdown, relative to the TS limit of 5 GPM, there was no actual consequence to public health or safety.

CORRECTIVE ACTIONS

Completed corrective actions include replacement of the pump seal cooler assembly, eliminating the union weld connection and preventing reoccurrence of this type of failure by use of a one-piece forged pipe-to-union fitting. Additionally, the Lower Seal Vent Line configuration was modified to be more flexible in order to alleviate pipe stresses from vibration. Lastly, a procedure change will be completed to provide guidance on preventing potential cold-working through grinding on small-bore piping.

NRC FORM 366 (11-2015)

Page 4 of 4 (11-2015)

U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2018

1. FACILITY NAME LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET Susquehanna Steam Electric Station, Unit 1 COMPONENT INFORMATION Pump Manufacturer: FLOWSERVE (Formerly BW/IP)

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

2. DOCKET NUMBER

3. LER NUMBER YEAR I

SEQUENTIAL I

REV NUMBER NO.

05000387 2016

- 019

- 00 Vent Line:

%-inch pipe to 1-inch socket connection Vent Line Material:

ASME Class II SA312

PREVIOUS SIMILAR EVENTS

LER 50-387/2015-009-00, PLA-7419, "Pressure Boundary Leakage from an Inadequate Weld Repair in Small Bore Pump Seal Vent Piping." January 11, 2016.

LER 50-388/2015-004-00, PLA-7337, "Degraded Condition Due to Reactor Coolant Pressure Boundary Leakage Caused by Vibration and Stiff Pipe Connection." June 10, 2015.

LER 50-387/2014-011-00, PLA-7286, "Degraded Condition Due to Reactor Coolant Pressure Boundary Leakage Caused by an Inadequate Weld." February 11, 2015.

NRC FORM 366 (11-2015)