05000498/LER-2006-003, Re Control Room Envelope HVAC Makeup Fan 11B Failure to Start
| ML063250325 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 11/09/2006 |
| From: | Halpin E South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NOC-AE-06002082 LER-06-003-00 | |
| Download: ML063250325 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 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 |
| 4982006003R00 - NRC Website | |
text
Nuclear Operating Company South Texas Protect Electric GeneratinS Station P.O Box 289 Wadsworth. Texas 77483 November 9, 2006 NOC-AE-06002082 I OCFR50.73 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 South Texas Project Unit 1 Docket No. STN 50-498 Licensee Event Report 1-06-003 Control Room Envelope HVAC Makeup Fan 11 B Failure to Start Pursuant to 10 CFR 50.73(a)(2)(i)(B), the South Texas Project (STP) submits the attached Unit I Licensee Event Report 1-06-003 as a result of failure of Control Room Envelope (CRE) HVAC Makeup Fan 11 B to start when actuated from the Control Room pushbutton.
This event did not have an adverse effect on the health and safety of the public.
There are no commitments contained in this Licensee Event Report. Corrective actions will be processed in accordance with the STP Corrective Action Program.
If there are any questions on this submittal, please contact either James R. Morris at (361) 972-8652 or me at (361) 972-7849.
E. D. alpin E.D Site Vice President/
Plant General Manager jrm
Attachment:
LER 1-06-003, Control Room Envelope HVAC Makeup Fan 1 B Failure to Start LER 1-06-003 (06002082) (CRE Makeup Fan 1 B).2.doc STI: 32085264
NOC-AE-06002082 Page 2 of 2 cc:
(paper copy)
(electronic copy)
Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 Richard A. Ratliff Bureau of Radiation Control Texas Department of State Health Services 1100 West 49th Street Austin, TX 78756-3189 Senior Resident Inspector U. S. Nuclear Regulatory Commission P.O. Box 289, Mail Code: MN116 Wadsworth, TX 77483 C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704 A. H. Gutterman, Esquire Morgan, Lewis & Bockius LLP Mohan C. Thadani U. S. Nuclear Regulatory Commission Steve Winn Christine Jacobs Eddy Daniels NRG South Texas LP C. Kirksey City of Austin Jon C. Wood Cox Smith Matthews J. J. Nesrsta R. K. Temple E. Alarcon City Public Service
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 06/30/2007 (6-2004)
, the NRC may sfor each block)inot conduct or sponsor, and a person is not required to respond to, the digits/characters frecbl k)information collection.
7PG
- 3. PAGE South Texas, Unit 1 05000498 1 OF 6
- 4. TITLE Control Room Envelope HVAC Makeup Fan 11 B Failure to Start'
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED I
FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO.
MONTH DAY YEAR 05000 I
I I
FACILITY NAME DOCKET NUMBER 09 11 2006 2006 - 003 -
00 11 09 2006 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
[o 20.2201(b)
El 20.2203(a)(3)(i)
[l 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii)
[1 20.2201(d)
El 20.2203(a)(3)(ii)
[I 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
El 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
[I 50.73(a)(2)(viii)(B)
El 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
[I 50.73(a)(2)(iii)
[I 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL [0 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
[I 50.73(a)(2)(iv)(A)
[I 50.73(a)(2)(x)
[I 20.2203(a)(2)(iii)
[I 50.36(c)(2)
El 50.73(a)(2)(v)(A)
[1 73.71(a)(4)
El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71(a)(5) 095 [E
20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
[I 50.73(a)(2)(v)(C)
[I OTHER [I 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B)
[E 50.73(a)(2)(v)(D)
Specify in Abstract below or in SUMMARY OF THE EVENT On 9/11/2006, at 1210 hours0.014 days <br />0.336 hours <br />0.002 weeks <br />4.60405e-4 months <br />, with Unit 1 in coast down operations, CRE Make-up Fan 11B was manually actuated from the Control Room in support of maintenance activities and failed to start.
The failure was due to the magnetic circuit breaker (short circuit trip protection) for Fan 11 B tripping on instantaneous (starting) over current. As a result, CRE HVAC Train B was declared inoperable.
Following the event, a walkdown of the Fan 11 B motor determined the locked rotor code letter specified in the nameplate data to be "J," indicating a higher than normal locked rotor current motor. Energy efficient and high torque motors have inherently higher locked rotor currents than more common older motors with the same full load ampere ratings and, therefore, require a higher instantaneous trip setting for the magnetic breaker. Based on the revision of STP Design Criteria 4E51 0EQ1 005, Class 1 E AC Power Distribution that was in effect when the design change package was prepared, the instantaneous trip setting of the magnetic breaker was incorrectly selected based on code letter "G" motors. "G" motors have lower locked rotor current requirements than "J" motors. As a result, the magnetic breaker setting was set too low causing a vulnerability to spurious tripping.
During emergency conditions (Safety Injection (SI) or Safety Injection with a Loss of Offsite Power (LOOP)), lower voltages on the bus feeding the fan could have sufficiently decreased the starting current required to allow a successful Fan 11 B motor start. However, a high radiation signal could require the motor to start without an SI signal. For a high radiation start, the bus voltages could be high and the motor windings could be at ambient temperature and this condition could also trip the breaker. Therefore, as evident by the Fan 11 B breaker trip, the
(If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17)
IV. CORRECTIVE ACTIONS
- 1.
The locked rotor current setting was adjusted for the 11 B CRE Makeup Fan breaker, and the 11 B Fan was declared operable on 09/12/2006 at 0240 hours0.00278 days <br />0.0667 hours <br />3.968254e-4 weeks <br />9.132e-5 months <br />.
- 2.
Walkdowns were performed on all Unit 1 and Unit 2 safety related 480 Volt motors affected by the MCC Upgrade Modification to verify the correct magnetic trip settings for the breakers. No other motors were found with incorrect magnetic breaker settings.
- 3.
The Electrical Setpoint Index guidance will be revised to apply the adjusted magnetic breaker setting criteria.
- 4.
The Electrical Setpoint Index (Notes) will be revised to specify a single magnetic breaker setting for safety related SSCs.
- 5.
Although no additional motors were found with incorrect magnetic breaker settings, optimization of Unit 1 and 2 motor breaker settings will be performed based on walkdown information.
- 6.
Case study training on this event will be provided to design and maintenance engineers.
- 7.
The design change procedure will be revised to include guidance on addressing potential operability and reportability issues when correcting conditions that support SSC operability (corrective design changes).
V.
PREVIOUS SIMILAR EVENTS
No similar reportable events due to incorrect magnetic circuit breaker settings have occurred at STP within the past three years.
VI.
ADDITIONAL INFORMATION
None