05000335/LER-2005-006, Equipment Failure Led to Inadvertent Mode Change During Cooldown

Equipment Failure Led to Inadvertent Mode Change During Cooldown

ML053570224
Person / Time
Site:	Saint Lucie
Issue date:	12/15/2005
From:	Jefferson W Florida Power & Light Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2005-246 LER 05-006-00
Download: ML053570224 (4)

LER-2005-006, Equipment Failure Led to Inadvertent Mode Change During Cooldown

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)(vii)(B), Common Cause Inoperability 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
3352005006R00 - NRC Website

text

FPL Florida Power & Light Company, 6501 S. Ocean Drive, Jensen Beach, FL 34957 December 15, 2005 L-2005-246 10 CFR § 50.73 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Re:

St. Lucie Unit I Docket No. 50-335 Reportable Event: 2005-006-00 Date of Event: October 17, 2005 Equipment Failure Led to Inadvertent Mode Change During Cooldown The attached Licensee Event Report 2005-006 is being submitted pursuant to the requirements of 10 CFR § 50.73 to provide notification of the subject event.

Vice President St. Lucie Nuclear Plant WJ/KWF Attachment an FPL Group company

AtI(6-2004)

U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION Equipment Failure Led to Inadvertent Mode Change During Cooldown

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED MSEQUENTIAL REVISION iMONTH DAY YEA ALI I T NAt UWWT INUMULK MOTHDY YAR*

YEAR NUMBER

- NUMBER YE~Jjj AR ll AUILI I T NAtt I NUMtaCK 10 17 2005 2005

- 006 00 112 15 2005

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANTTOTHE REQUIREMENTS OF 10 CFR §: (Check all thatapply) 4 o

20.2201(b) 0 20.2203(a)(3)(i) 0 50.73(a)(2)(i)(C) 0 50.73(a)(2)(vii) o 20.2201(d) 0 20.2203(a)(3)(ii) 0 50.73(a)(2)(ii)(A) 0 50.73(a)(2)(viii)(A) o 20.2203(a)(1) 0 20.2203(a)(4) 0 50.73(a)(2)(ii)(B) 0 50.73(a)(2)(vii)(B) o 20.2203(a)(2)(i) 0 50.36(c)(1)(i)(A) 0 50.73(a)(2)(iii) 0 50.73(a)(2)(ix)(A)

10. POWER LEVEL 0

20.2203(a)(2)(ii) 0 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A) 0 50.73(a)(2)(x) o 20.2203(a)(2)(iii) 0 50.36(c)(2) 0 50.73(a)(2)(v)(A) 0 73.71 (a)(4) o 20.2203(a)(2)(iv) 0 50.46(a)(3)(ii) 0 50.73(a)(2)(v)(B) 0 73.71 (a)(5) o 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(C) 0 OTHER Sped~yI Abstract below or In 0

20.2203(a)(2)(vi) 1 50.73(a)(2)(i)(B) 0 50.73(a)(2)(v)(D) 1Z. U;LNbt: WUNIAt;LI I-UK IHlb LLK NAME I tLtl~MUl NUMOtK {IfGUO8 Aea LOOG)

Kenneth W. Frehafer, Licensing Engineer (772) 467 -

7748 1.. GUMFLt it: UNI LINE I-UK tAL;H L;UM'UNNI a-AILUKL IkbL.Kll)

IN hub KhEIUKI

CAUSE

SYSTEM COMPONENT MANUFACTURER REPORTABLE ONENT REPORTABLE D

SB HCV W255 NO

14. bUFLPMt:N tIAL Ktt'UKI ItA'tltILJ I

15. EXPECTED UAW r-Am YES_

SUBMISSION (If yes, complete EXPECTED SUBMISSION DATE).

X NO l

DATE l

l ABS TRACT (Limit to 1400 spaces, ie., approximately 15 single-spaced typewritten lines)

On October 17,

2005, St. Lucie Unit 1 was offline and cooling down for a scheduled refueling outage.

The atmospheric dump valves were used for the cooldown. While in Mode 4 conditions, a malfunction of the IA steam generator atmospheric steam dump valve caused an unplanned heatup and subsequent inadvertent change to Mode 3 conditions.

Local manual control of the valve was taken and the plant cooldown recommenced.

The event investigation concluded that the valve actuator diaphragm failed and caused the valve to close.

Inadequate work instructions led to the conditions that caused the diaphragm failure.

Corrective actions included rework of the valve actuator and revising the model work order.

This event had no impact on the health and safety of the public.

The Mode change occurred without the required number of operable boration injection flowpaths.

However, there was no effect on the boration injection flowpath from the refueling water tank, the allowed outage time for only one boration injection flowpath was not exceeded, and the boric acid makeup tanks remained available if needed.

NRC FORM 36A (e620U4)U.S. NUCLEAR REGULATORY COMMISSION (6-2004)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION

1. FACILITY NAME

2. NUMBER

6. LER NUMBER

3. PAGE YEAR SEQUENTIAL REVISION St. Lucie Unit 1 05000335 Page 2 of 3 2005 006 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

=

=

Description of the Event On October 17, 2005, St. Lucie Unit 1 was offline and cooling down for the scheduled SLI-20 refueling outage. At 2047 hours0.0237 days <br />0.569 hours <br />0.00338 weeks <br />7.788835e-4 months <br /> the previous day, with Unit 1 in Mode 3 conditions, the unit entered the action statement for Technical Specification 3.1.2.2 as planned during the plant cooldown.

This Technical Specification requires at least two operable boron injection flowpaths in Modes 1 though 4 using the boric acid makeup (BAM) tanks or the refueling water tank (RWT).

However, the BAM tanks contents were expended, as planned, when used to increase the boron concentration of the reactor coolant system (RCS) to refueling concentration, leaving only one boron injection flowpath via the RWT. At 2104 hours0.0244 days <br />0.584 hours <br />0.00348 weeks <br />8.00572e-4 months <br /> the previous day, the cooldown method was swapped from the steam bypass system to the atmospheric dump valves (ADVs).

As the cooldown continued, Unit 1 entered Mode 4 at 0140 hours0.00162 days <br />0.0389 hours <br />2.314815e-4 weeks <br />5.327e-5 months <br />.

At 0245 hours0.00284 days <br />0.0681 hours <br />4.050926e-4 weeks <br />9.32225e-5 months <br />, Unit 1 inadvertently re-entered Mode 3 due to a malfunction that closed HCV-08-2A [EIIS:SB:HCV], the 1A steam generator ADV, that resulted in an unplanned heatup of the RCS.

At 0250 hours0.00289 days <br />0.0694 hours <br />4.133598e-4 weeks <br />9.5125e-5 months <br />, operators were dispatched to take local control of the ADV.

Mode 4 conditions were reentered at 0700 hours0.0081 days <br />0.194 hours <br />0.00116 weeks <br />2.6635e-4 months <br />.

Cause of the Event

The inadvertent Mode change was caused by a malfunction of the 1A steam generator ADV that caused the unplanned heatup of the RCS.

HCV-08-2A is an air operated valve (AOV).

During the in-situ investigation, a significant amount of air was observed/heard leaking from the top cap of the actuator casing when air was supplied to the actuator.

Since the actuator is reverse acting, air is supplied to the underside of the actuator/diaphragm.

Therefore, leakage out of the top of the actuator casing indicates a breach in the pressure boundary at the diaphragm/diaphragm plate.

Disassembly of the valve actuator confirmed that the diaphragm had failed.

There were no signs of diaphragm degradation or damage that would have caused the failure.

The diaphragm failure mode was determined to be overload because the diaphragm failed between two bolt holes, at a cross-section of minimum area.

The investigation concluded that inadequate overhaul work instructions (e.g., unspecified torque values and grease application) led to the conditions that allowed the diaphragm overload failure.

The overhaul model work order was revised to provide better work instructions. Additionally, to ensure proper assembly, the Unit 1 sister valve HCV-08-2B was overhauled during the outage.

Analysis of the Event

In Modes 1, 2, 3, and 4, Technical Specification 3.1.2.2 requires at least two of the following three boron injection flow paths be operable:

a. One flow path from the BAM tanks with via a BAM pump through a charging pump to the RCS.

b. One flow path from the BAM tanks via a gravity feed valve through a charging pump to the RCS.

c. The flow path from the RWT via a charging pump to the RCS.

Mode 3 was entered without the Technical Specification 3.1.2.2 limiting condition for operation (LCO) being met.

Technical Specification 3.0.4 states that an entry into an operational Mode shall not be made when conditions of the LCO are not met and the e

I-U.S. NUCLEAR REGULATORY COMMISSION (6-2004)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION

1. FACILITY NAME

2. DOCKET

6. LER NUMBER

3. PAGE YEAR l SEQUENTIAL l REVISION St. Lucie Unit 1 05000335 Page 3 of 3 2005 -006

- 00 l

TEXT (If more space is required, use additional copies of NRC Form 366A) (17) action requires a shutdown.

With less than the required boron flowpaths available, the action leads to a unit shutdown if two boron flowpaths can not be restored.

Although the action statement requirements were in effect in Mode 4 and did not change with the inadvertent Mode 3 entry, this condition resulted in a non-compliance with Technical Specification 3.0.4.

Therefore, the facility was operated in a condition prohibited by the Technical Specifications and the reporting requirements of 10 CFR 50.73(a)(2)(i)(B) were met.

Analysis of Safety Significance The only safety function for the ADVs is to maintain pressure boundary integrity of the secondary system pressure boundary upstream of the main steam isolation valves.

The ADV actuator failure did not impact the ability of the ADV to perform its pressure boundary safety function.

Other functions include the ability to relieve steam to provide decay and sensible heat removal during RCS cooldowns when the steam bypass system (to the condenser) is not available.

The ADV actuator failure did not adversely affect the ability for local manual control of the ADV.

Personnel were dispatched to locally open the ADV in accordance with procedures and the cooldown was re-established.

During this event, the BAM tank contents were used to increase RCS boron concentration as part of the planned cooldown. Although the BAM tanks were not operable in accordance with the Technical Specification, the tank remained available and their contents could be replenished if needed. The boron injection flowpath via the RWT was not compromised by this event, so it remained operable throughout the evolution.

Additionally, the allowed outage time for less than two boron injection flowpaths was not exceeded during this event.

Additionally, this failure mode is not applicable to the St. Lucie Unit 2 ADV actuators because the actuators are motor operated, not air operated.

Therefore, this event had no impact on the health and safety of the public.

Corrective Actions

1. The actuator for HCV-08-2A was overhauled and a new diaphragm installed under work order 35024947-01.

HCV-08-2B was overhauled under work order 35027570-01.

2. The model work order for overhauling HCV-08-2A and HCV-08-2B was revised to provide bolting sequences and torques for reassembly as well as specifying that grease should not be applied to the diaphragm or diaphragm plate at assembly.

Other Information

Similar Events

None Failed Equipment Component:

Atmospheric Dump Valve for Steam Generator 1A Manufacturer: WKM Model Number: 70-19-3DRTS valve, 70-13-IR size 280 actuator