05000249/LER-2008-001
| Dresden Nuclear Power Station | |
| Event date: | 08-17-2008 |
|---|---|
| Report date: | 10-16-2008 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| Initial Reporting | |
| ENS 44420 | 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown |
| 2492008001R00 - NRC Website | |
Dresden Nuclear Power Station (DNPS) Unit 3 is a General Electric Company Boiling Water Reactor with a licensed maximum power level of 2957 megawatts thermal. The Energy Industry Identification System codes used in the text are identified as [XX].
A. Plant Conditions Prior to Event:
Unit: 03� Event Date: 8-17-2008 �Reactor Mode: 1� Mode Name: Power Operation Power Level: 100 percent Reactor Coolant System Pressure: 1000 psig
B. Description of Event:
On August 16, 2008, at approximately 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> (CDT), with Unit 3 at approximately 100 percent power, DNPS Operations personnel attempted to pump the Unit 3 drywell floor drain sump [BD], which is used to partially satisfy Surveillance Requirement (SR) 3.4.4.1. The pumps started as expected, however, the drywell floor drain sump monitoring system [IJ] flow integrator indicated no flow. During a second attempt, Operations personnel observed that the positions of the isolation valves were indicated as being in their proper indicated position. The pump breakers were inspected locally and pump motor amps were checked with no abnormalities observed. Since the drywell floor drain sump could not be pumped, the water volume in the drywell floor drain sump could not be measured resulting in the plant not able to satisfactorily complete SR 3.4.4.1. The sumps had been successfully pumped previously at 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on August 16, 2008.
Troubleshooting was performed to identify the possible malfunction. Based on the troubleshooting, it appeared that a blockage of flow existed in the line to containment isolation valve 3-2001-105 [V] or the valve failed closed. DNPS determined that the repairs to the system could not be made with Unit 3 online. Unit 3 initiated a plant shutdown on August 17, 2008 at approximately 0902 hours0.0104 days <br />0.251 hours <br />0.00149 weeks <br />3.43211e-4 months <br /> (CDT) as the plant was not able to meet Technical Specification (TS) 3.4.4, "RCS Operational Leakage.
On August 17, 2008 at approximately 1211 hours0.014 days <br />0.336 hours <br />0.002 weeks <br />4.607855e-4 months <br /> (CDT), an Emergency Notification System call was made for the TS 3.4.4 required plant shutdown. The event was assigned ENS event number 44420.
The Unit 3 shutdown was halted at approximately 30 percent power.
DNPS verbally requested a Notice of Enforcement Discretion (NOED) on August 17, 2008 at approximately 1030 hours0.0119 days <br />0.286 hours <br />0.0017 weeks <br />3.91915e-4 months <br /> (CDT). Specifically, the NOED requested a seven-day extension to the TS Completion Times for TS 3.4.4 and TS 3.4.5, "RCS Leakage Detection Instrumentation," to place the unit in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Mode 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. This extension was requested to provide sufficient time to reconfigure the drywell floor drain sump monitoring system such that the drywell equipment drain sump monitoring system could be used to quantify unidentified drywell leakage. In addition, the seven-day extension provided sufficient time for DNPS to request, and the NRC to process an emergency TS amendment. The NRC granted the NOED on August 17, 2008 at approximately 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br /> (CDT).
The written NOED request, "Request for Enforcement Discretion for Technical Specifications (TS) 3.4.4, 'RCS Operational Leakage' and TS 3.4.5, 'RCS Leakage Detection Instrumentation" was � submitted to the NRC on August 19, 2008, consistent with the guidelines provided in Regulatory Issue Summary 2005-01, "Changes to Notice of Enforcement Discretion (NOED) Process and Staff Guidance," and NRC Inspection Manual Part 9900, "Operations — Notices of Enforcement Discretion.
An emergency TS amendment request, "Request for Emergency License Amendment Regarding Drywell Floor Drain Sump Monitoring System," was submitted on August 18, 2008. The submittal requested the use of the Unit 3 drywell equipment drain sump monitoring system to satisfy the TS 3.4.5 requirements applicable to the Unit 3 drywell floor drain sump monitoring system until the drywell floor drain sump monitoring system is repaired during an outage of sufficient duration, but no later than the startup from D3R20. The NRC issued the amendment on August 22, 2008, within the allowed time period specified in the NOED.
This event is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B), "Any operation or condition which was prohibited by the plant's Technical Specifications." The unidentified drywell leakage could not be measured for a period of time that exceeded the TS 3.4.4 Allowed Completion Time and drywell floor drain sump monitoring system was inoperable for a period of time that exceeded TS 3.4.5 Allowed Completion Time. DNPS, as a result of the emergency TS amendment, is currently in compliance with its TS.
C.C Cause of Event:
The cause of the event is indeterminate until the drywell floor drain sump monitoring system can be examined during an outage of sufficient duration, but no later than the startup from D3R20.
The equipment in the flow path of the drywell floor drain sump monitoring system are (1) the drywell floor drain sump pumps [3A-2001-451 and 3B-2001-451], (2) the drywell floor drain sump pump discharge check valves [3-2001-101A and 3-2001-101B], (3) the drywell floor drain sump pump discharge manual isolation valves [3-2001-102A and 3-2001-102A] and (4) the drywell floor drain sump pumps AOV containment isolation valves [3-2001-105 and 3-2001-106]. The two pumps with their associated check and manual valves are in parallel and only one pump needs to function to pump down the sump. The two AOV's are in series and both must operate to pump down the sump.
Since both sump pumps operate independently and were run without successful flow, the likelihood of the cause being a failure of both of the pumps or pump associated valves at the same time is very low. Therefore, the location of the proposed flow blockage is down stream of where the two pump discharge lines tie together. The currently proposed Apparent Cause is a blockage of flow in the three-inch (3") line down stream of where the two pumps tie in together. This blockage may be attributed to some foreign material or either of the drywell floor drain sump pumps AOV containment isolation valves [3-2001-105 and 3-2001-106] separating at the process diaphragm to valve stem connection. In either case, the most likely location for this blockage is at the aforementioned valves, since the weir type design of the diaphragm valves can act as a dam for foreign material.
_ NRC FORM 366A (9-2007) PRINTED ON RECYCLED PAPER
D. Safety Analysis:
The safety significance of the event is minimal. During this event, DNPS continued to operate within the requirements of the TS and the NRC granted NOED, which temporarily extended the Completion Times of TS 3.4.4 and TS 3.4.5. Additionally, the NRC granted an amendment to allow the use of the Unit 3 drywell equipment drain sump monitoring system to satisfy the TS 3.4.5 requirements applicable to the Unit 3 drywell floor drain sump monitoring system until the drywell floor drain sump monitoring system is repaired during an outage of sufficient duration, but no later than the startup from D3R20. Therefore, the consequences of this event had minimal impact on the health and safety of the public and reactor safety.
E. Corrective Actions:
DNPS verbally requested a NOED on August 17, 2008 at approximately 1030 hours0.0119 days <br />0.286 hours <br />0.0017 weeks <br />3.91915e-4 months <br /> (CDT). The NRC granted the NOED on August 17, 2008 at approximately 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br /> (CDT).
The written NOED request was submitted to the NRC on August 19, 2008, consistent with the guidelines provided in Regulatory Issue Summary 2005-01 and NRC Inspection Manual Part 9900.
An emergency license amendment request was submitted on August 18, 2008. The NRC issued the amendment on August 22, 2008, within the allowed time specified in the NOED.
The drywell floor drain sump monitoring system was reconfigured such that the drywell equipment drain sump monitoring system could be used to quantify unidentified drywell leakage.
The Unit 3 drywell floor drain sump monitoring system will be repaired during an outage of sufficient duration, but no later than the startup from D3R20.
F. Previous Occurrences:
A review of DNPS Licensee Event Reports (LERs) for the last three years did not identified any LERs associated with the drywell floor drain sump monitoring system.
G. Component Failure Data:
N/A �