05000335/LER-2017-001, Regarding Reactor Coolant Pressure Boundary Leak on the 1B2 Reactor Coolant Pump Lower Seal Heat Exchanger
| ML17093A948 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 04/03/2017 |
| From: | Deboer D Florida Power & Light Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-2017-057 LER 17-001-00 | |
| Download: ML17093A948 (4) | |
| 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)(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)(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) |
| LER closed by | |
| IR 05000335/2017002 (2 August 2017) | |
| 3352017001R00 - NRC Website | |
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U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Re:
St. Lucie Unit 1 Docket No. 50-335 Reportable Event: 2017-001-00 Date of Event: January 31, 2017 APR 0 3 2017 Reactor Coolant Pressure Boundary Leak on the 1B2 Reactor Coolant Pump Lower Seal Heat Exchanger L-2017-057 10 CFR 50.73 The Licensee Event Report 2017-001-0 is being submitted pursuant to the requirements of 10 CFR 50.73 to provide notification of the subject event.
Respectfully, Daniel DeBoer Site Director St. Lucie Plant DD/ KWF Attachment cc:
USNRC Regional Administrator; Region II USNRC Senior Resident Inspector, St. Lucie Nuclear Plant Florida Power & Light Company 6501 S. Ocean Drive, Jensen Beach, FL 34957
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (06-2016)
LICENSEE EVENT REPORT (LER)
(See Page 2 for required number of digits/characters for each block)
APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2018 Estimated 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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- 1. FACILITY NAME St. Lucie Unit 1
- 2. DOCKET NUMBER 05000335
- 3. PAGE 1 Of 3
- 4. TITLE Reactor Coolant Pressure Boundary Leak on the 1B2 Reactor Coolant Pump Lower Seal Heat Exchanger
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL NUMBER REV NO.
MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 05000 1
31 2017 2017 001 0
04 03 2017 FACILITY NAME DOCKET NUMBER 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 3 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x)
- 10. POWER LEVEL 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(v)(A) 73.71(a)(4) 0 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C) 73.77(a)(1) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(D) 73.77(a)(2)(i) 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(vii) 73.77(a)(2)(ii) 50.73(a)(2)(i)(C)
OTHER Specify in Abstract below or in Page 3 of 3
Safety Significance
This condition was determined to be of very low safety significance for the following reasons:
The maximum Unidentified RCS leak rate of 0.17 gpm was well within the capacity of the three charging [EIIS:CB] pumps (44 gpm each) [EIIS:P] which make up water volume to the RCS. RCS leak balances are normally calculated at once per day. Real time RCS leakage indications are detected through containment particulate radiation monitoring and cavity sump detection and may drive more frequent leakage calculations.
The indication of RCS leakage approximately one week after pump start indicates that fatigue crack initiation and propagation through the inner tubing (0.125-inch min wall) occurred quite rapidly after pump start. Crack propagation appears to have slowed or arrested quickly as the total flaw length had only reached 15% of the inner tubes outer circumference approximately three months later. Such fatigue crack behavior is consistent with the postulated reduction in fatigue strength due to the presence of a residual stress. As the crack propagated, the residual stress was relieved and the positive mean stress reduced or eliminated. The applied cyclic loads associated with pump operation were insufficient to support continued crack propagation across the entire tubing cross section. The Unidentified RCS leak rate plateau during this period of time validates this observation. A Finite Element Analysis calculation was performed to confirm that the observed through wall crack would not propagate and leakage would remain within the capacity of the charging pumps.
Therefore, this event had no impact on the health and safety of the public.
Corrective Actions
- 1. The 1B2 RCP lower seal heat exchanger leak was repaired during the maintenance outage.
- 2. All remaining St. Lucie Unit 1 and 2 RCP lower seal heat exchangers were inspected and no other flaws were identified.
Failed Components Identified Flowserve supplied RCP lower seal heat exchanger
Additional Information
The weld repair required relief from ASME Code requirements, and those details are documented in FPL letter L-2017-017 dated Feb 2, 2017, titled In-service Inspection Plan Fourth Ten-Year Interval Unit 1 Relief Request No. 14, Revision 0, ADAMS accession number ML17033A151.