05000389/LER-2014-001, Lucie, Unit 2 Regarding Unit Shutdown Due to Leak on Safety Injection Tank Vent Valve Piping
| ML14280A480 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 09/22/2014 |
| From: | Jensen J Florida Power & Light Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-2014-280 LER 14-001-00 | |
| Download: ML14280A480 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 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)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3892014001R00 - NRC Website | |
text
FPL.
September 22, 2014 L-20'4-280 10 CFR 50.73 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Re:
St, Lucie Unit 2 Docket No. 50-389 Reporaeble Event: 2014-001 Date of Event: July 25, 2014 Unit Shutdown Due to Leak on Safety Injection Tank Vent Valve Piping The attached Licensee Event Report 2014-001 is being submitted pursuant to the requirements of 10 CFR 50.73 to provide notification of the subject event.
Respectfully, Joeh ensen(Ar c)
Site Vice President St. Lucie Plant JJ/lrb Attachment Florida Power & Light Company P2-6501 S. Ocean Drive, Jensen Beach, FL 34957
NRC FOI'M 366 U.S. NUCLEAR REGULATORY COMMISSION APPROXT[D BY OMB: NO. 3150-0104 EXPIRE,7: 01131/2017 (0)2014)
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 />.
- , /,
I*Reported lessons learned are incorporated into the licensing process and fed back to industry.
Send comments regarding burden estimate to the FOIA, Pivacy and Information Collections LICENSEE EVENT REPORT LER)
Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by L N internet e-mail to Infocollects.ResourcsOnrc.gov, and to the Desk Officer, Office of Information and (See Page 2 for required number of.
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- 1. FACILITY NAME
- 2. LOCKET NUMBER
- 3. PAGE St. Lucie Unit 2 05000389 1 OF 3
- 4. TITLE Unit Shutdown Due to Leak on Safety Injection Tank Vent v'alve Piping
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE R. OTHER FACILITIES INVOLVED I
SE1UENTIAL REV FACILITY NAME I DOCKET NUMBER NUMBER NO.
ONTH DAY YEAR FACILITY NAME DOCKET NUMBER
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO rHE REQUIREMENTS OF 10 CFR §: (Check all that apply)
D 20.220'.(b)
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20.2203(a)(3)(i) j 50.73(a)(2)(i)(C)
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50.73(a)(2)(vii) 1 20.2201(d) 0 20.2203(a)y3)(ii)
Z 50.73(a)(2)(ii)(A)
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[] 20.2203(a)(1)
[] 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
LI 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i)
LI 50.36(c)(1)(i)(A)
LI 50.73(a)(2)(iii)
LI 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL LI 20.2203(a)(2)(i0)
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50.36(c)(1)(ii)(A)
EL 50.73(a)(2)(iv)(A)
[: 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
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LI 50.73(a)(2)(v)(A)
LI 73.71(a)(4) 1 20.2203(a)(2)(iv)
LI 50.46(a)(3)(ii)
LI 50.73(a)(2)(v)(B)
El 73.71 (a)(5) 100 LI 20.2203(a)(2)(v)
Z 50.73(a)(2)(i)(A)
[L 50.73(a)(2)(v)(C)
Z 50.73(a)(2)(i)(B)
[L1 50.73(a)(2)(v)(D)
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Description of the Event
Background
On March 17, 2014 Unit 2 2B1 safety injection tank (SIT) (EIIS:TK) discharge piping vent valve V3811 (EIIS:VTV) was replaced during the SL2-21 refueling outage. On June 22, 2014, the control room entered the Process Radiation Monitor Abnormal Operating Procedure, due to a rising trend on two containment particulate radiation monitors.
Concurrently, plant data showed that 2B1 SIT was being filled daily beginning June 22, 2014.
The frequent SIT replenishment requirement and radiation monitor trend was indicative of a leak.
Containment entries were made on June 24 and 25, 2014 and on July 23 and 25, 2014 to investigate the suspected leak from the 2B1 SIT piping.
On July 25, 2014 at 1129 EDT, detailed video imaging confirmed the leak was on a one inch pipe (EIIS: PSF) between the safety injection system (EIIS:BQ) SIT and vent valve V381 1. The valve is within the Quality Group A (ASME Class 1 equivalent), Seismic Class I portion of the safety injection line. The applicable Technical Specification Limiting Condition of Operation (LCO) required the SIT to be restored to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or shut down to Mode 3 within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> with continuation to Mode 4 within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
The unit was subsequently shut down to repair the leak. The shutdown was uncomplicated and all plant safety systems functioned as designed. The cracked vent line and valve assembly were replaced and returned to service on July 28, 2014.
Cause of the Event
A root cause evaluation team for the SI pipe break determined that the repair and replacement of vent valve V3811 was not performed as prescribed in the work control documents utilized by plant maintenance. This resulted in a number of adverse factors which ultimately resulted in the failure of the pipe nipple upstream of the vent valve due to outside diameter initiated, high cycle, low stress fatigue.
A contributing cause was that neither Maintenance nor the non-destructive examination (NDE) Inspector verified the dimensions of the field-cut inlet pipe nipple before the vent valve was welded in as required by procedures.
Analysis of the Event
For the purposes of evaluating impact on the effected systems, the flaw was conservatively considered to have fully failed, resulting in a nominal one (1) inch diameter breach in the safety injection header at the location of the flaw. A one (1) inch breach, at this location, would result in a depressurization of the 2B1 SIT and loss of inventory from the tank. As a result, the affected SIT was declared Inoperable. The affected safety injection header is one (1) of the four (4) cold leg injection points for the high pressure safety injection (HPSI) system.
Flow from the two HPSI Pumps combines upstream of the postulated breach and flows into the affected cold leg. Given that the postulated breach was relatively small when compared to the twelve (12) inch diameter safety injection header and the capacity of HPSI system, the HPSI system would have been able to deliver sufficient flow to the reactor core, under accident conditions, to meet its safety-related functions.
Safety Significance
The identified leakage was determined to be less than 1 gpm. This flow rate is insignificant as compared to either the SIT discharge flowrate or the safety injection flow rate during LOCA events. Also, the SIT tank volume lost during a four hour station blackout (SBO) event is insignificant compared to the total volume of the four SIT's. As a result, the safety significance of the minor leakage from this location was minimal. In addition, the branch line for the vent valve contained a tie-back support which would act to restrain the valve and piping in place in the event the through-wall flaw continued to propagate.
Finally, the impact of the leakage on surrounding equipment did not reduce their ability to perform their design functions.
This condition is reportable in accordance with the following requirements: 1) 10 CFR 50.73(a)(2)(ii)(A), 2) 10 CFR 50.73(a)(2)(i)A, and 3) 10 CFR 50.73(a)(2)(i)B.
Corrective Actions
- 1. The "Weld Coordinator" software program will be modified to include hold points in weld travelers for dimension verification. For Class 1, 2 and 3 piping and Pipe Category 4 and 5 (NNS, high pressure), the non-destructive examination inspector will verify piping dimensions.
- 2.
Welding work control procedures will be revised to ensure that the applicable weld travelers incorporate the requirement to use NDE procedure 4.10 "Component, Support & Inspection ASME Section III and ANSI B31.1 Butt and Fillet Welds Visual Examination" and that the procedure is clearly designated as a corrective action to prevent recurrence (CAPR).
- 3.
Maintenance continuing training will be revised to emphasize the findings of the root cause evaluation, the impact to the plant of this event, the importance of using human performance tools when complying with work documents, and the importance of ensuring that condition reports are addressed by the appropriate work document.
Similar Events
The failure of a Unit 2 main steam antenna type vent line MS-11-1 occurred at approximately 2355 on 5/15/11.
The one inch steam line vent MS-i 1-1 appeared to have broken off, creating a steam leak that was non-isolable without closing the main steam isolation valves (MSIVs).
An inspection of the failed vent revealed it did not meet the design dimensions on the installation work order. During subsequent Unit 2 main steam walkdowns another vent line, MS-8-4, was found to have been installed without meeting design dimensions. Two high energy vent lines were not installed in accordance with the approved plant design; one of these lines subsequently failed resulting in a plant shutdown. The root cause was that the installation of the vent line was not performed as prescribed in the work control documents utilized by plant maintenance.