05000423/LER-2005-005, Automatic Reactor Trip of Millstone Unit 3 Due to Low-Low Steam Generator Level
| ML060330266 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 01/18/2006 |
| From: | Price J Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 06-002 LER 05-005-00 | |
| Download: ML060330266 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(iv)(B), System Actuation 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iii) 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)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iv), System Actuation |
| 4232005005R00 - NRC Website | |
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}ODominion Dominion Nuclear Connecticut, Inc.
Millstone Power Station Rope Ferry Road Waterford, CT 06385 JAN I 8 2008 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Serial No.
MPS Lic/WEB Docket No.
License No.06-002 RO 50-423 NPF-49 DOMINION NUCLEAR CONNECTICUT. INC.
MILLSTONE POWER STATION UNIT 3 LICENSEE EVENT REPORT 2005-i005-00. AUTOMATIC REACTOR TRIP OF MILLSTONE UNIT 3 DUE TO LOW-LOW STEAM GENERATOR LEVEL This letter forwards Licensee Event Report (LER) 2005-005-00, documenting an event that occurred at Millstone Power Station Unit 3, on December 1, 2005. This LER is being submitted pursuant to 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in manual or automatic actuation of systems listed in 50.73(a)(2)(iv)(B).
If you have any questions or require additional information, please contact Mr. David W.
Dodson at (860) 447-1791, extension 23,46.
Very truly yours, tin Price Vice President - Millstone I529
Serial No.06-002 LER 2005-005-00, Automatic Reactor Trip of Millstone Unit 3 Due to Low-Low S/G Level Page 2 of 2 Attachments:
1 Commitments made in this letter: None.
cc:
U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 Mr. V. Nerses Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 8C2 Rockville, MD 20852-2738 Mr. S. M. Schneider NlRC Senior Resident Inspector Millstone Power Station
NRC FORM 366 NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 06/30/2007 (6-2004)
, the NRC (See reverse for required number of digits/characters for each block) may not conduct or sponsor, and a person is not required to respond to, the information collection.
FACILITY NAME (1)
DOCKET NUMBER (2)
PAGE (3)
Millstone Power Station - Unit 3 05000423 1 of 2 TITLE (4)
Automatic Reactor Trip of Millstone Unit 3 Due to Low-Low Steam Generator Level EVENT DATE()
LER NUMBER (6)
REPORT DATE (7)
OTHER FACILmES INVOLVED (8)
FACILITY NAME DOCKET NUMBER MO DAY YEAR YEAR SEQUENTIAL REV MO NUMBERINO.
M DAY YEAR
__FACILITY NAME DOCKET NUMBER 12 01 2005 2005-005-00 01 18 2006 OPERATING 1THISREPORT IS SUMITTI:
PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) (11)
MODE (9) 20.2201 (b) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(B) 50.73(a)(2)(ix)(A)
POWER 038
_ 20.2201 (d) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(x)
LEVEL (110) 20.2203(a)(1) 50.31;(c)(1)(i)(A)
X 50.73(a)(2)(iv)(A) 73.71 (a) (4) 20.2203(a)(2)(i) 50.36S(c)(1)(ii)(A)
=
50.73(a)(2)(v)(A) 73.71 (a)(5) 20.2203(a)(2)(ii)
_ 50.36(c)(2) 50.73(a)(2)(v)(B)
OTHER 20.2203(a)(2)(iii) 50.416(a)(3)(ii) 50.73(a)(2)(v)(C)
Specify In Abstract below or 20.2203(a)(2)(iv)
_ 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(D) in NRC Form 366A 20.2203(a)(2)(v) 50.7.3(a)(2)(i)(B) 50.73(a)(2)(vii) 20.2203(a)(2)(vi) 50.73(a)(2)(i)(C) 50.73(a)(2)(viii)(A) 20.2203(a)(3)(1) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(B)
LICENSEE CONTACT FOR THIS LER (12)
NAME TELEPHONE NUMBER (Include Area Code)
David W. Dodson, Supervisor Nuclear Station Licensing 1(860) 447-1791 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)
CAUSE
SYSTEM I COMPONENT MANU-REPORTBLE l
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE I
FACTURER TO EPIX FA CTURER TO EPIX SUPPLEMENTAL REPORT EXPECTED (14)
EXPECTED MONTH DAY YEAR 3 YES (If yes, complete EXPECTED SUBMISSION DATE).
1 NO SUBMISSION 04 28 2006 I
I I______
DATE (15)
ABSTRACT (Limit to 1400 spaces, L.e., approximately 15 single-spac 9d typewritten lines) (16)
At approximately 14:45 on December 1, 2005, with Millstone Unit 3 (MP3) in Mode 1 at an indicated power level of 38%,
an automatic reactor trip occurred on 'C' Steam Generator Low-Low level (S/G Low-Low level). At the time of the reactor trip, a downpower to 30% was in progress to facilitate a containment entry to locate and repair a Reactor Coolant System (RCS) leak. As turbine load and reactor power were reduced, main turbine vibrations increased above allowable limits and the main turbine was manually tripped in accordance with procedure. After the turbine was manually tripped, the reactor automatically tripped on 'C' S/G Low-Low level. All safety systems performed as designed, including auto actuation of the auxiliary feedwater system. The balance of the plant shutdown was uncomplicated.
The direct cause of the reactor trip was a Low-Low level in the 'C' S/G that resulted from the shrink in S/G water level created by the manual turbine trip. The plant is designed to maintain the reactor critical following a turbine trip below 45% power. At the time of the trip, the Reactor Proteclion System S/G Low-Low Level Trip setpoints were being maintained at 27% vice the nominal value of 18% to address Westinghouse identified S/G level inaccuracies associated with the S/G mid-deck plate differential pressure. Operation at the increased set point reduced the margin available to accommodate S/G level transients that occur following a turbine trip at power.
The automatic reactor trip and AFW actuation are reportable in accordance with 1 OCFR50.73(a)(2)(iv).
NRC FORM 366 (6-2004)
(If more space is required, use additional copies of NRC Form 366A) (17)
- 1.
Event Description
At approximately 14:45 on December 1, 2005, with Millstone Unit 3 (MP3) in Mode 1 at an indicated power level of 38%, an automatic reactor trip occurred on 'C' Steam Generator Low-Low level (S/G Low-Low level). At the time of the reactor trip, a power reduction to 30% was in progress to facilitate a containment entry to locate and repair a Reactor Coolant System (RCS) [AB] leak. As turbine [TA] load and reactor power were reduced, main turbine vibrations increased above allowable values and the main turbine was manually tripped in accordance with procedure. After the turbine was manually tripped, the reactor automatically tripped on 'C' S/G Low-Low level. All safety systems performed as designed, including auto actuation of the auxiliary feedwater system. The balance of the plant shutdown was uncomplicated.
The automatic reactor trip is reportable as a reactor protection system [JC] actuation in accordance with 1 OCFR50.73(a)(2)(iv). The actuation of the auxiliary feedwater system [BA] [JD] is also reportable in accordance with 1 OCFR50.73(a)(2)(iv).
- 2.
Cause
The direct cause of the reactor trip was a Low-Low level in the 'C' S/G that resulted from the shrink in S/G water level created by the manual turbine trip. The plant is designed to maintain the reactor critical following a turbine trip below 45% power (P-9 permissive setpoint). At the time of the trip, the Reactor Protection System S/G Low-Low Level Trip setpoints were being maintained at 27% vice the nominal value of 18% to address Westinghouse identified S/G level inaccuracies associated with the S/G mid-deck plate differential pressure. Operation at the increased set point reduced the margin available to accommodate S/G level transients that occur following a turbine trip at power. The event investigation is on-going. A supplemental LER will be submitted.
- 3. Assessment of Safety Conseauences This event was of low safety consequences as the reactor trip was uncomplicated and all safety functions were accomplished per design. A reactor trip on low-low steam generator level protects the reactor from a loss of heat sink.
- 4.
Corrective Action
Corrective actions will be addressed upon completion of the reactor trip event assessment.
- 5.
Previous Occurrences
There have been no occurrences of a reactor trip following a turbine trip below the P-9 permissive setpoint in the previous 3 years.
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].