05000454/LER-2009-001, Drain Procedure for ECCS Suction Line Creates an Unanalyzed Condition Due to Inadequate Configuration Requirements
| ML093570453 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 12/23/2009 |
| From: | Enright D Exelon Corp, Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BYRON 2009-0138 LER 09-001-00 | |
| Download: ML093570453 (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 |
| 4542009001R00 - NRC Website | |
text
10 CFR 50.73 December 23, 2009 LTR:
BYRON 2009-0138 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Byron Station, Units 1 and 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455
Subject:
Licensee Event Report 2009-001-00, "Drain Procedure for ECCS Suction Line Creates Unanalyzed Condition Due to Inadequate Configuration Requirements" The enclosed Licensee Event Report (LER) is being submitted in accordance with 10 CFR 50.73, "Licensee event report system," paragraph (a)(2)(ii)(B) as an unanalyzed condition. This condition involved inadequate controls in a safety system drain procedure that could have potentially created a leakage path outside of containment. The potential safety significance of this condition is being assessed and will be documented in a supplement to this LEA.
There are no regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact Mr. David Gudger, Regulatory Assurance Manager, at (815) 406-2800.
Respectfully, Daniel J. Enright Site Vice President Byron Station
Enclosure:
LER Number 2009-001-00
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150*0104 EXPIRES: 08/31/2010 (9-2007)
, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the informAtion r:oIlAr:tlon
- 13. PAGE Byron Station, Unit 1 05000454 1 of 4
- 4. TITLE Drain Procedure for ECCS Suction Line Creates an Unanalyzed Condition Due to Inadequate Configuration Requirements
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR ISEQUENTIALIREV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.
MONTH DAY YEAR Byron Station, Unit 2 05000455 FACILITY NAME DOCKET NUMBER 10 28 2009 2009 001 00 12 23 2009
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 1 o 20.2201 (b) o 20.2203(a)(3)(i) o 50.73(a)(2)(i)(C) o 50.73(a)(2)(vii) o 20.2201 (d) o 20.2203(a)(3)(ii) o 50.73(a)(2)(ii)(A) o 50.73(a)(2)(viii)(A) o 20.2203(a)(1) o 20.2203(a)(4) 181 50.73(a)(2)(ii)(B) o 50.73(a)(2)(viii)(B) o 20.2203(a)(2)(i) o 50.36(c)(1 )(i)(A) o 50.73(a)(2)(iii) o 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL o 20.2203(a)(2)(ii) o 50.36(c)(1)(ii)(A) o 50.73(a)(2)(iv)(A) o 50.73(a)(2)(x) o 20.2203(a)(2)(iii) o 50.36(c)(2) o 50.73(a)(2)(v)(A) o 73.71(a)(4) 100%
o 20.2203(a)(2)(iv) o 50.46(a)(3)(ii) o 50.73(a)(2)(v)(B) o 73.71(a)(5) o 20.2203(a)(2)(v) o 50.73(a)(2)(i)(A) o 50.73(a)(2)(v)(C) o OTHER o 20.2203(a)(2)(vi) o 50.73(a)(2)(i)(B) o 50.73(a)(2)(v)(D)
Specify in Abstract below or In 2009 001 00 Further discussions ensued with other Operators concerning the issue raised which culminated in the Shift Manager, at approximately 0400, directing the 1SI8811 B valve to be de-energized closed. However, by this time the draining was completed and the vent and drain valves re-c1osed. The RO initiated an Issue Report (IR) to place his concern into the Corrective Action Program (CAP) to address future RH suction line drain evolutions. At 1524 the same day, the 1SI8811 B 1ST stroke tests and other work activities on the RH pump motor were also completed.
Based on initial response to the IR written, Operations Management de-energized the 1SI8811 B during the re-fill evolution. At 2241 the Unit 1 B RH system suction piping fill was completed and the Unit 1 Train B RH returned to operable status.
Review of the Operations IR concluded that having the RH vent and drain valves open while the SI8811 valve is capable of automatic opening is an unanalyzed condition. This condition potentially has more than minor safety significance during the time this condition existed for approximately 3.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.
Use of procedures BOP RH-4 and BOP RH-3 was suspended pending a root cause evaluation and appropriate
corrective actions
The investigation revealed there were five other occurrences in which the RH suction vent and drain valves were open while the SI8811 valve was capable of automatically operating during Operating Modes 1 through 4. These occurrences were:
Unit 1 RH Train B April 6, 2005 Unit 1 RH Train A April 19, 2005 Unit 2 RH Train B October 15, 2005 Unit 2 RH Train A October 16, 2005 Unit 2 RH Train B December 7, 2006 The exact duration of these previous conditions could not be determined, but is estimated to be similar to the current event. Other RH work windows occurred that required draining of the RH suction line, however due to the nature of the maintenance activities, the SI8811 valve was de-energized closed as part of the work control process.
This condition is being reported in accordance with 10 CFR 50.73 (a)(2)(ii)(B) for being in an unanalyzed condition that significantly degraded plant safety. Other 10 CFR 50.73 reporting requirements may apply after the safety significance evaluation is completed. These will be included, as appropriate, in a supplement to this report.
C. Cause of the Event
The cause of this condition was an inadequate procedure in that when executed in Operating Modes 1 through 4, the BOP RH*4 did not provide necessary requirements to ensure a flow path from Containment into the Auxiliary Building environment did not exist if an automatic SI8811 opening signal coincident with a LOCA occurred during the draining evolution.
The lack of procedural controls in this procedure existed since original startup of the units. The cause of the inadequacy could not be determined.
Several contributing causes were also identified; these include:
The Work Control Process does not have an effective means to ensure rigorous technical human performance techniques are applied to the implementation of improvement initiatives.
2009 001 00 The Improved Technical Specifications and Bases implementation in February 1999 did not contain sufficient detail on this unique penetration configuration and its closed system outside of Containment as a barrier.
Licensed Operators received less than adequate training on the importance of maintaining a closed system intact as an isolation barrier.
D. Safety Significance
There were no actual safety consequences to this condition. At no time, in Modes 1 through 4, was a SI8811 valve in an open condition with the RH suction line breached.
If a LOCA were to have occurred requiring the initiation of the ECCS during the short timeframe the RH vent and drain valves were open, then the SI8811 valve would have opened upon a RWST low level signal and radioactive sump water would have had a leakage path outside of Containment and into the Auxiliary Building.
The significance of this condition is being assessed and will be updated in a supplement to this report.
E. Corrective Actions
Procedures BOP RH-4 and BOP RH-3 will be revised to ensure the SI8811 valve is de-energized closed in Modes 1 through 4 while the RH vent and drain valves are open.
An extent of condition assessment was conducted for other containment penetrations with an isolation valve that receive an automatic open signal to mitigate a DBA. No further issues were identified. In addition, an extent of cause review will be done to assess the adequacy of other activities moved from a refueling outage condition to on-line condition.
Appropriate Work Control processes will be assessed to determine the adequacy of technical rigor being applied to improvement initiatives of this nature.
Training will be provided to Licensed Operators and Engineers concerning lessons learned from this event. In addition, the Licensed Operator Training program will be assessed to determine adequacy of training in terms of this penetration configuration and the application of TS requirements for procedure revisions that change the mode of performance of an activity.
The TS Bases has been enhanced regarding the configuration of the Containment Penetration containing the SI8811 valves.
F.
Previous Occurrences
Other than the previous occurrences mentioned in Section B, there have been no similar events identified at Byron Station in previous three years.PRINTED ON RECYCLED PAPER