05000390/LER-2004-002, Regarding Manual Reactor Trip Due to Dropped Rods
| ML043280364 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 11/18/2004 |
| From: | Lagergren W Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 04-002-00 | |
| Download: ML043280364 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 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)(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) |
| 3902004002R00 - NRC Website | |
text
Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381-2000 William R. Lagergren, Jr.
Site Vice President, Watts Bar Nuclear Plant NOV 1 8 2004 U.S. Nuclear Regulatory Commission ATTN:
Document Control Desk Washington, D. C. 20555 Gentlemen:
In the Matter of
)
Docket No.50-390 Tennessee Valley Authority
)
WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 -
DOCKET NO.
50-390 -
FACILITY OPERATING LICENSE NPF LICENSEE EVENT REPORT (LER) 50-390/2004-002 This submittal provides Licensee Event Report 390/2004-002.
This LER addresses an event that occurred on September 19, 2004, which resulted in an actuation of engineered safety features, which included the Reactor Protection and Auxiliary Feedwater Systems.
This event is being reported under 10 CFR 50.73 (a)(2)(iv)(A).
There are no Regulatory commitments identified in this submittal.
If you have any questions about this LER, please contact P. L.
Pace at (423) 365-1824.
Sincerel W. R. Lagerg nR"
'eCycd pOW,
U.S. Nuclear Regulatory Commission Page 2 NOV 1 8 2004 Enclosure cc (Enclosure):
INPO Records Center Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, Georgia 30339-5957 NRC Resident Inspector Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, Tennessee 37381 Mr. Chandu P. Patel, Project Manager U.S. Nuclear Regulatory Commission MS 08H12 One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738 U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVEDBYOMB: NO.3150-0104 EXPIRES: 06130r2007 (6-2004)
, the NRC (See reverse for required number of may not conduct or sponsor, and a person Is not required to respond to, the diqits/characters for each block) information collection.
- 3. PAGE Watts Bar Nuclear Plant, Unit 1 05000 - 390 1 OF 5
- 4. TITLE Manual Reactor Trip Due to Dropped Rods
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME 0
5 000 NUMER NO 05000 i
FACILITY NAME DOCKET NUMBER 09 19 2004 2004
. 002 00 11 18 2004 05000
- 9. OPERATING MODE 11.THIS REPORT IS SUBMITTED PURSUANTTO THE REQUIREMENTS OF 10 CFR§: (Check all th!at apply)
O 20.2201(b) 0 20.2203(a)(3)(i) 0 50.73(a)(2)(i)(C) 5 50.73(a)(2)(vii)
Mode 1 5 20.2201(d) a 20.2203(a)(3)(ii)
D 50.73(a)(2)(ii)(A) 5 50.73(a)(2)(viii)(A) o 20.2203(a)(1) 5 20.2203(a)(4) 5 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) o 20.2203(a)(2)(i) 5 50.36(c)(1)(i)(A)
D 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL 5 20.2203(a)(2)(ii) a 50.36(c)(1)(ii)(A)
[
50.73(a)(2)(iv)(A) 5 50.73(a)(2)(x)
O 20.2203(a)(2)(iii) 5 50.36(c)(2) a 50.73(a)(2)(v)(A)
C 73.71(a)(4) o 20.2203(a)(2)(iv) 0 50.46(a)(3)(ii) 5 50.73(a)(2)(v)(B) 57371(a)(5) 100%
5 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A) 5 50.73(a)(2)(v)(C) 5 OTHER O 20.2203(a)(2)(vi) 50.73(a)(2)(l)(B) 5 50.73(a)(2)(v)(D)
Specify In Abstract below or In (If more space is required, use additional copies of NRC Form 3664)
I. PLANT CONDITION(S)
On September 19, 2004, at approximately 0452 Eastern Daylight Savings Time (EDT) hours, Unit 1 was In Mode 1, steady state operation at 100 percent power. The Reactor Coolant System (RCS) (Energy Industry Identification System (EIIS)
Code AB) pressure was approximately 2235 psig and RCS Tavg was approximately 588 degrees F.
II. DESCRIPTION OF EVENT
A. Event On September 19,2004, at approximately 0452 hours0.00523 days <br />0.126 hours <br />7.473545e-4 weeks <br />1.71986e-4 months <br />, Unit 1 was In Mode 1, steady state operation at 100 percent power when the operators received simultaneously Control Rod Urgent Failure, Rod Position Indication (RPI) Trouble, and rods at bottom alarms. Four control rods (EIIS Code BA), F14, 86, K2, PIO, in control bank B group 2, fell to bottom of core and Initiated the rods at bottom alarm. This event resulted In a rapid power drop to about 67 percent which then stabilized at approximately 85 percent.
During this transient, operators took manual control of the main feedwater regulating valves (EIIS Code V). Operators responded to the rods at bottom Indications by manually tripping the reactor at approximately 0456 EDT. Systems functioned as expected In automatic with the exception of the loop number 1 Reactor Coolant Pump (EIIS Code AB/P) which failed to transfer to its respective start bus (EIIS Code BU) on generator (EIIS Code GEN) lockout. The remaining control rods Inserted properly in response to the reactor trip. The Auxiliary Feedwater (AFW) System (EIIS Code BA) actuated In response to the trip, as expected.
B. Inoperable Structures, Components, or Systems that Contributed to the Event There were no inoperable structures, components, or systems that contributed to this event.
C. Dates and Approximate Times of Major Occurrences
Date Time Event 09/19/04 09119/04 09/19/04 09/19104 04:52:44 04:52:45 04:52:46 04:52:47 09/19/04 04:52:48 09119/04 04:52:52 09/19/04 04:52:53 09/19/04 04:52:54 09/19/04 04:52:55 Unit 1 Reactor at full power - all conditions normal Main Control Room (MCR) received a 'Control Rod Urgent Failure" alarm.
MCR received a 'Control RPI Trouble' alarm.
Four Control Rods Dropped In Control Bank Group B Group 2. MCR receives a ORods at Bottom alarm.
Computer Enhanced Rod Position Indication (CERPI) (EIIS Code AANZI) Panel in MCR shows K2 Control Rod as Invalid - B6 and P10 Indicated as valid CERPI Panel In MCR shows K2, B6, and P10 control rods as Invalid CERPI panel In MCR shows K2, B6, F14, and P10 control rods as Invalid.
CERPI Panel In MCR shows 66 and P10 control rods as Invalid CERPI Panel in MCR shows K2, B6, F14, and P10 Control rods as valid.
(Ifmore space is required, use additional copies of NRC Fon, 364A)
C. Dates and Approximate Times of Major Occurrences
(Continued)
Date Time Event 09/19/04 04:56 MCR crew alarm response 09/19/04 04:56 Unit 1 Reactor was manually tripped
D. Other Systems or Secondary Functions Affected
The four dropped rods prompted sudden reactor downpower which caused a secondary side transient.
E. Method of Discovery
This condition caused a number of alarms in the main control room.
F. Operator Actions
Operations responded to the plant transient in accordance with appropriate plant procedures. Based on these actions, the unit was placed in a stable condition in Mode 3. However, there was an area of crew performance that did not meet management expectations. This Issue was identified as the 3 minutes and 34 seconds time span between the dropping of the Bank 2 rods and crew initiation of the reactor trip. This condition has been placed into TVA's corrective action program.
G. Safety System Responses:
Upon manual trip of the reactor, the Auxiliary Feedwater System started as expected. See Section IV for further details and analysis of this event.
Ill. CAUSE OF THE EVENT A. Immediate Cause:
The Immediate cause for this event was the dropping of the four control rods into the reactor core. This event promptly caused a reactor downpower which stabilized at approximately 85 percent and caused a secondary side transient.
B. Root Cause:
The root cause of the reactor trip was a malfunction of a rod control power cabinet circuit. TVA performed a Kepner Tregoe (KT) analysis of this dropped rod event and determined that the cause could have been the failure of one of three cards (Regulator Card-most probable, Phase Control Card-probable, and a Firing Board Card-least probable) which provide power and control functions for Rod Control Bank B, Group 2 that contained the four rods that dropped. All three cards were shipped to Westinghouse to perform post-mortem' testing to determine the exact cause. The Westinghouse test report revealed that a transistor (Q7) had failed on the Phase Control Card. The report also stated that this transistor failure would have caused the dropped group that was seen in this event.
C. Contributing Factors There were no contributing factors for this event that were Identified.
(If more space is required, use additional copies of (If more space Is required, use additional copies of NRC Form 366A)
VI). ADDITIONAL INFORMATION A. Failed Components:
The Westinghouse test report revealed that transistor, Q7, had failed on the Phase Control Card in the Rod Control System.
B. Previous LERs on Similar Events:
A review of previous WBN LERs reveals that there have been no other events associated with dropped rods.
C. Additional Information
None.
D. Safety System Functional Failure Consideration:
This event Is not considered a safety system functional failure In accordance with NEI 99-02 in that the principal plant safety systems operated as designed. Therefore, the functional capability of the overall system was not jeopardized.
E. Loss Of Normal Heat Removal Consideration:
This event Is not considered a scram with loss of normal heat removal.
VII. COMMITMENTS
None.