05000455/LER-2005-001, Unit 2 Automatic Reactor Trip Due to Low Steam Generator Level Resulting from a Software Fault on the Turbine Control Power Runback Feature
| ML060930493 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 12/19/2005 |
| From: | Kuczynski S Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BYRON 2005-0153 LER 05-001-00 | |
| Download: ML060930493 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4552005001R00 - NRC Website | |
text
December 19, 2005 LTR:
BYRON 2005-0153 File:
1.10.0101 United States Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
Licensee Event Report (LEA) 455-2005-001-00, Unit 2 Automatic Reactor Trip Due to Low Steam Generator Level Resulting from a Software Fault on the Turbine Control Power Runback Feature Byron Station, Unit 2 Facility Operating License No. NPF-66 NRC Docket No. SIN 50-455 Enclosed is an LEA concerning the Byron Station Unit 2 automatic reactor trip that occurred on October 19, 2005. This condition is reportable to the NRC in accordance with 10 CFR 50.73 (a)
(2) (iv) (A).
Should you have any questions concerning this matter, please contact Mr. William Grundmann, Regulatory Assurance Manager, at (815) 406-2800.
Respectfully,
- 2. 1~r~
Stephen E. Kuczynski Site Vice President Byron Nuclear Generating Station SEK/JL/rah Attachment LEA 455-2005-001-00
NRC FORM 366 U.S. NUCLEAR REGULA APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 06/30/2007 (6-2004)
LICENSEE EVENT REPORT (LER)
(See reverse for required number of digits/characters for each block)
Estimated burden per response to comp y with this mandatory collection request: 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />. Reported lessons learned are ncorporated into the I cens ng process and fed back to industry. Send comments regarding burden estimate to the Records and FOIA,Privacy Sam ce Branch (1-5 F52), U.S Nuclear Regulatory Commission, Washington DC 20555-0001 or by internet e-mal to infocollects@nrc.gov, and to the Desk Officer, Off ce of Information and Regu atory Affairs, NEOB-10202, 3150-0104), Office of Management and Budget, Washington, DC 20503. Ia means used to impose an informat on collection does not d splay a currently valid 0MB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the informat on collection.
- 1. FACILITY NAME Byron Station, Unit 2
- 2. DOCKET NUMBER
- 13. PAGE 05000455 f
1 of 4
~. TITLE Unit 2 Automatic Reactor Trip Due to Low Steam Generator Level resulting from a Software Fault on the Turbine Control Power Runback Feature
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OThER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL NUMBER
~E0V MONTH DAY YEAR FACILITY NAME DOCKET NUMBER Byron Station, Unit 1 05000454 10 19 2005 2005 001 00 12 19 2005 FACIL TY NAME DOCKET NUMBER N/A N/A
~. OPERATING MODE 1
- 11. THIS REPORT IS SUBMIUED PURSUANTTO THE REQUIREMENTS OF 10 CFR~:(Checkallthat apply) 0 20.2201(b) 0 20.2203(a)(3)~)
0 50.73(a)(2)(i)(C) 0 50.73(a)(2)(vii) o 20,2201(d) 0 20,2203(a)(3)(ii) 0 50.73(a)(2)(ii)(A) 0 50.73(a)(2)(viii)(A) 0 20.2203(a)(1) 0 20.2203(a)(4) 0 50.73(a)(2)(ii)(B) 0 50.73(a)(2)(viii)(B) o 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) 0 20.2203(a)(2)(ii) 0 50.36(c)(1)(ii)(A)
~
50.73(a)(2)(iv)(A) 0 50.73(a)(2)(x) o 20.2203(a)(2)(iii) 0 50.36(c)(2) 0 50.73(a)(2)(v)(A) 0 73.71(a)(4) o 20.2203(a)(2)(iv) 0 50.46(a)(3)(ii) 0 50.73(a)(2)(v)(B) 0 73.71 (a)(5) 0 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A) 0 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 n Abstract below or in (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17)
D. Safety Analysis
There were no safety consequences impacting plant or public safety as a result of this event.
The automatic turbine runback feature is a non-safety related design feature and is not credited in any Updated Final Safety Analysis Report chapter 15 accident and transient analyses.
The reactor trip system functioned as designed and shutdown the reactor without incident.
The 3rd quarter 2005, Unit 2 NRC performance indicator for unplanned scrams per 7000 critical hours is in the green band at a value of zero.
With this reactor trip the indicator will still be well within the green band. A PRA analyses also indicates this event was not risk significant.
E. Corrective Actions
The software fault was repaired on Unit 2. The DEH upgrade was installed on Unit 1 in the Spring 2005 refuel outage with the same software faults.
However, the automatic turbine runback feature was never challenged. The software was also corrected on Unit i.
Procedural guidance will be developed to ensure the Ovation based systems have not been compromised by the introduction of undetected software errors.
This process will be applicable to current and future Ovation based upgrades.
Procedural guidance will be developed within the modification process to ensure that lessons learned from this event will be applied to other digital upgrades.
This event will be presented as a human performance case study to applicable operations personnel.
The vendor has also conducted a root cause evaluation and has and will take appropriate corrective actions within their programs and processes.
These corrective actions will be evaluated by Exelon and considered for implementation.
1 BOA-SEC-i and 2BOA-SEC-1 have been revised to provide correct procedural guidance when a turbine runback does not occur.
F.
Previous Occurrences
There have been no previous occurrences of this nature.