05000390/LER-2008-003, Automatic Start of Auxiliary Feedwater Unavailable During Startup Entry Into Modes 2 and 1
| ML082810058 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 10/06/2008 |
| From: | Skaggs M Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 08-003-00 | |
| Download: ML082810058 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v), Loss of Safety Function 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 |
| 3902008003R00 - NRC Website | |
text
October 6, 2008 10 CFR 50.73 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 - LICENSEE EVENT REPORT 390/2008-003, REVISION 0 - AUTOMATIC START OF AUXILIARY FEEDWATER UNAVAILABLE DURING STARTUP ENTRY INTO MODES 2 AND 1 This submittal provides LER 390/2008-003. This LER documents operations or conditions during startup of the plant that were prohibited by the plants Technical Specifications. The report regarding this condition is provided in accordance with 10 CFR 50.73(a)(2)(i)(B) and 10 CFR 50.73(a)(2)(v)(D).
There are no regulatory commitments in this letter. If you have any questions concerning this matter, please call Mike Brandon at (423) 365-1824.
Sincerely, Original signed by Greg Boerschig for M. D. Skaggs Site Vice President Watts Bar Nuclear Plant Enclosure cc: See Page 2
U.S. Nuclear Regulatory Commission Page 2 October 6, 2008 Enclosure cc (Enclosure):
NRC Resident Inspector Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, Tennessee 37381 ATTN: John G. Lamb, Project Manager U.S. Nuclear Regulatory Commission Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation MS O8H4 Washington, DC 20555-0001 U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303 Institute of Nuclear Power Operations 700 Galleria Parkway, NW Atlanta, Georgia 30339-5957
E-1 ENCLOSURE LER 2008-003 AUTOMATIC START OF AUXILIARY FEEDWATER UNAVAILABLE DURING STARTUP ENTRY INTO MODES 2 AND 1
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
(See reverse for required number of digits/characters for each block)
APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 1. FACILITY NAME Watts Bar Nuclear Plant
- 2. DOCKET NUMBER 05000390
- 3. PAGE 1 OF 4
- 4. TITLE Automatic Start of Auxiliary Feedwater Unavailable During Startup Entry into Modes 2 and 1
- 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 N/A DOCKET NUMBER N/A 08 07 2008 2008 -
03 0
10 06 2008 FACILITY NAME N/A DOCKET NUMBER N/A
- 9. OPERATING MODE 2
- 10. POWER LEVEL 0%
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(A) 73.71(a)(4) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C)
OTHER 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)
Specify in Abstract below or in II.
DESCRIPTION OF EVENT (continued):
D.
Other Systems or Secondary Functions Affected
None E.
Method of Discovery
NRC identified the violation in inspection report 05000390-08-03.
F.
Operator Actions
Operators manually monitored plant status and placed the Auxiliary Feedwater System autostart back into service once turbine driven Main Feedwater Pumps were put into operation.
G.
Safety System Responses All safety systems responded as designed.
III.
CAUSE OF EVENT
Plant-specific design was apparently not considered in adoption of Improved Standard Technical Specifications. Plant design was to use the standby main feedwater pump for startup. It was noted in a 2006 noncited violation that use of the standby main feedwater pump violated TS 3.3.2, Function 6.e. Resolution of that finding was to do a 3.0.4.b risk evaluation when starting with the standby pump. NRC inspectors noted that, according to TVA procedure, the risk evaluation was not intended to be used on a routine basis, so TVA decided to start up using the auxiliary feedwater pumps. It was considered preferable to use the motor-driven pumps without the steam-driven AFW pump (Terry Turbine), so one channel of the autostart instrumentation had to indicate that a MFW pump was running. In fact, the channel accurately reflected the measured parameter, that there was control oil pressure, but the MFW pump was not running. This configuration would ensure that as soon as the MFW pump was started, the AFW autostart circuitry would be functional. TVA interpreted that the instrument channel was functional because it transmitted the signal that oil pressure was up. The NRC violation clarified that the channel should not be considered operable when the pump was not running IV.
ANALYSIS OF THE EVENT
This event was a literal noncompliance with the WBN TS, but had only very minor safety significance. TVA had configured the autostart circuitry so that the AFW autostart would be available as soon as the MFW pump was pumping forward. Prior to that point, AFW was provided to the steam generators. However, only the two motor-driven AFW pumps were being used. The actual autostart signal would start all three AFW pumps.
With the autostart signal unavailable, and less than all the equipment that would be started by that signal, TVA was not in compliance with the WBN TS requirement.
The autostart of AFW on trip of all MFW pumps is an anticipatory function. The actual safety function relied upon in the WBN accident analysis is the AFW start on Low-Low Steam Generator Level, which was unaffected by this event.
V.
ASSESSMENT OF SAFETY CONSEQUENCES
As noted in the NRC inspection report, the finding was determined to be of very low safety significance because the finding did not represent an actual loss of safety function of a single train for greater than its TS allowed outage time since other initiation signals were available to automatically start the auxiliary feedwater pumps if needed. Additionally, the system was configured so that AFW autostart on trip of all MFW pumps would be available as soon as the MFW pump was pumping forward, which satisfies the intended function.
VI.
CORRECTIVE ACTIONS
A.
Immediate Corrective Actions
As an interim measure, since NRC identified this noncompliance, TVA has modified its startup process to enter Mode 2 with both channels indicating that the MFW pumps are tripped and with all three AFW pumps running to feed the Steam Generators. TVA then starts one of the MFW pumps and resets the instrument channel, which will support entry into Mode 1, to a level at which the second feedwater pump can be started.
B.
Corrective Actions to Prevent Recurrence TVA has submitted a License Amendment Request, TS-08-07, to change applicability of this requirement so that it will only apply once the MFW pump is pumping forward. This will permit operation as described in the noncited violation.
VII.
ADDITIONAL INFORMATION
A.
Failed Components None.
B.
Previous LERs on Similar Events LER 2006-008 documented a similar event in which the instrument channels were bypassed in order to start the plant with the standby MFW Pump. That event was identified in NRC Inspection Report 2006-004.
C.
Additional Information
None.
D.
Safety System Functional Failure There was no safety system functional failure.
E.
Loss of Normal Heat Removal Consideration There was no loss of normal heat removal capability.
VIII.
COMMITMENTS
There are no regulatory commitments in this submittal.