05000483/LER-2007-002, Regarding Manual Reactor Trip at Reduced Power Due to Inadequate Feedwater Control
| ML071350252 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 05/08/2007 |
| From: | Diya F AmerenUE, Union Electric Co |
| To: | Document Control Desk, Plant Licensing Branch III-2 |
| References | |
| ULNRC05412 LER 07-002-00 | |
| Download: ML071350252 (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)(i)(B), Prohibited by Technical Specifications |
| 4832007002R00 - NRC Website | |
text
I-AmerenUE Cal/away Plant PO Box 620 Fulton, MO 65251 May 8, 2007 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop P1-137 Washington, DC 20555-0001 ULNRC05412 SAmereilUF Ladies and Gentlemen:
DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 UNION ELECTRIC CO.
FACILITY OPERATING LICENSE NPF-30 LICENSEE EVENT REPORT 2007-002 Manual Reactor Trip at Reduced Power due to Inadequate Feedwater Control The enclosed licensee event report is submitted in accordance with 10CFR50.73(a)(2)(iv)(A) to report a manual reactor trip and auxiliary feedwater actuation.
This letter does not contain new commitments.
Sincerely, Fadi M. Diya Director Plant Operations FMD/CSP/slk Enclosure j---E2ý2-a subsidiary efAmeren Corporation
ULNRC05412 May 8, 2007 Page 2 Mr. Bruce S. Mallett Regional Administrator U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-4005 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. Jack N. Donohew (2 copies)
Licensing Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop O-7D1 Washington, DC 20555-2738 Missouri Public Service Commission Governor Office Building 200 Madison Street PO Box 360 Jefferson City, MO 65102-0360 Records Center Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, GA 30339
ULNRC05412 May 8, 2007 Page 3 bcc:
C. D. Naslund A. C. Heflin C. R. Younie D. T. Fitzgerald G. A. Hughes D. E. Shafer S. L. Gallagher (100)
L. M. Belsky (NSRB)
K. A. Mills P. M. Bell msp(nrc.2ov ded@nrc.gov LEREventse~inpo.org babrook(rwcnoc.com A160.0761 Certrec Corporation 4200 South Hulen, Suite 422 Fort Worth, TX 76109 (Certrec receives ALL attachments as long as they are non-safeguards and public disclosed).
Send the following without attachments:
Ms. Diane M. Hooper Supervisor, Licensing WCNOC P.O. Box 411 Burlington, KS 66839 Mr. Scott Bauer Regulatory Affairs Palo Verde NGS P.O. Box 52034, Mail Station 7636 Phoenix, AZ 85072-2034 Mr. Dennis Buschbaum TXU Power Comanche Peak SES P.O. Box 1002 Glen Rose, TX 76043 Mr. Stan Ketelsen Manager, Regulatory Services Pacific Gas & Electric Mail Stop 104/5/536 P.O. Box 56 Avila Beach, CA 93424
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 06/30/2007 (6-2004)
, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Callaway Plant Unit 1 05000483 1 OF 4
- 4. TITLE Manual Reactor Trip at Reduced Power Due to Inadequate Feedwater Control
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENIA FE ACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR I
____NUMBER NO.
FACILITY NAME DOCKET NUMBER 03 09 2007 2007
- - 002 -
00 05 08 2007
- 19. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) o1 20.2201(b)
[I 20.2203(a)(3)(i)
[0 50.73(a)(2)(i)(C)
[I 50.73(a)(2)(vii) 1[
20.2201(d)
[I 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)
[3 50.73(a)(2)(ii)(B)
[0 50.73(a)(2)(viii)(B) oI 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
[] 20.2203(a)(2)(ii)
[
50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A)
[0 50.73(a)(2)(x) 0 20.2203(a)(2)(iii) 0 50.36(c)(2) 03 50.73(a)(2)(v)(A) 03 73.71 (a)(4)
[I 20.2203(a)(2)(iv) 0 50.46(a)(3)(ii)
[3 50.73(a)(2)(v)(B)
[0 73.71 (a)(5) 30%
[3 20.2203(a)(2)(v) 03 50.73(a)(2)(i)(A)
[I 50.73(a)(2)(v)(C)
[0 OTHER [o 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B) 0 50.73(a)(2)(v)(D)
Specify in Abstract below or in SUMMARY OF THE EVENT, INCLUDING DATES AND APPROXIMATE TIMES On March 9, 2007, while operating at 100 percent power, Callaway Plant experienced a main condenser tube leak. At 0824, high sodium levels were indicated in the main steam condenser, requiring power reduction to less than five percent power until all Action Levels for condenser sodium were exited. The on-shift Operations crew began reducing power to enter MODE 3 in accordance with procedural guidance. During the transition from the Main Feedwater Regulation Valves (MFRV) to the Main Feedwater Regulation Bypass Valves (MFRBV), problems were experienced controlling water level in the "C" steam generator (S/G). At 1043, with both the MFRV and MFRBV indicating closed and the "C" S/G level still increasing, the reactor was manually tripped.
The "C" MFRBV was isolated for scheduled maintenance when the event started. Upon completion of the work, the valve was retested and returned to service at 0928 while the rapid power reduction was in progress.
The Balance of Plant (BOP) Operator reported the "C" MFRBV did not respond correctly during the transition from the MFRV to the MFRBV on the "C" steam generator. Indications were no change in feedwater flow was noted for corresponding change in valve demand in either open and closed directions. Feedwater flow changed to a value greater than expected causing steam generator level to rise outside the normal operating band. Feedwater flow to the "C" steam generator indicated about 1.3E6 lbs/hr and level in the "C" S/G continued to increase, while both the "C" MFRV and MFRBV indicated closed. The BOP Operator reported the condition and at 10:43 the Control Room Supervisor directed the Reactor Operator to trip the reactor due to loss of level control for "C" steam generator.
(At this point it should be noted that the actual problem was a failed I/P positioner on MFRV (If more space is required, use additional copies of (if more space is required, use additional copies of NRC Form 366A) (17)
The "C" MFRV, AEFCV0530, was able to perform its nuclear safety function to close on a Feedwater Isolation Signal (FWIS) during this event because this safeguards signal bypasses the valve positioner.
From a review of plant data after the reactor trip, the MFRV fully closed when the FWIS was generated.
This event was evaluated with the Callaway PRA model. The evaluation determined that the conditional core damage probability (CCDP) of the event was less than 1E-6; therefore, this event was of very low risk significance. Use of the PRA model to evaluate the event provides for a comprehensive, quantitative assessment of the potential safety consequences and implications of the event, including the consideration of alternative conditions beyond those analyzed in the FSAR.
III. CAUSE(S) OF THE EVENT AND CORRECTIVE ACTION(S)
During the downpower, at approximately 30% power, the positioner to AEFCV0530, "C" SG MFRV, failed such that the valve would not change position on demand. The programmed failure response is 'Fail as is'.
This is supported by the fact that the feedwater flow could not be reduced below 1.3E6 lbs/hr. An as-found AOV Diagnostic test was performed that determined the positioner had failed. The positioner could be made to intermittently operate by lightly tapping on it. The positioner was sent to an independent laboratory for analysis. The root cause of the event was attributed to a defective or damaged feedback shaft gear tooth in the positioner. The gear tooth damage was most likely due to a manufacturing defect or a problem during the initial factory assembly of the positioner.
The positioner has been replaced with a like kind positioner. The functionality and operability of the MFRV were verified through the performance of diagnostic and surveillance testing prior to returning the unit to service. An extent of condition review has been completed with no additional deficiencies identified.
The cause of the digital rod position indication problem for control rod Kl0 was a bent pin on a cable connector. The bent pin was straightened. Post maintenance testing was completed satisfactorily.
IV. PREVIOUS SIMILAR EVENTS
A reactor trip due to a MFRV positioner failure is not a recurrence for Callaway.
V. ADDITIONAL INFORMATION
The system and component codes listed below are from the IEEE Standard 805-1984 and IEEE Standard 803A-1984 respectively.
AEFCV0530, Steam Generator C Main Feedwater Regulating Valve, IEEE System: SJ, Feedwater Component: FCV, Valve, Control, Flow Positioner on AEFCV00530, System: SJ, Feedwater, Component: CPOS, positioner Manufacturer:
ABB, Model: TZID-C Digital Rod Position Indication, System: AA, Control Rod Drive Component: CON, connector