05000237/LER-2002-001
| Dresden Nuclear Power Station Unit 2 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2372002001R00 - NRC Website | |
LICENSEE EVENT REPORT (LER) f33), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, And Budget, Washington, DC 20503. If an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) Dresden Nuclear Power Station Unit 2 05000237 NUMBER NUMBER 2002 � (If more space is required, use additional copies of NRC Form 366A)(17)
A. Plant Conditions Prior to Event:
Unit: 02 � Event Date: 01-18-2002 Reactor Mode: 1 � Mode Name: Run Reactor Coolant System Pressure: 1004 psig
B. Description of Event:
Event Time: 2135 CST Power Level: 95 percent At the time of this event, with conservative decision making, the event was reported under the requirements of 10 CFR 50.72(b)(3)(v), "Any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to: (A) Shut down the reactor and maintain it in a safe shutdown condition; (B) Remove residual heat; (C) Control the release of radioactive material; or (D) Mitigate the consequences of an accident." Upon further evaluation, it was determined that the Isolation Condenser (IC) would have performed its intended safety function. The GE analysis for IC initiation assumes that the IC automatic initiation pressure setpoints are at their worst case settings when determining the time delay relay limitations.
Nuclear Fuel Management evaluated the actual pressure setpoints and determined that the IC would have automatically initiated and provided its safety function for any time delay relay setting below 24.4 seconds.
Therefore, 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.
To support Extended Power Uprate (EPU), GE re-evaluated the Transient Analyses for Dresden station. GE's analysis specified changes to the IC initiation time delay setpoints. The AV for the IC time delay relays changed from EPU requirements.
During the development of the Technical Specification (TS) AV, historical concerns existed regarding the existing IC time delay relays ability to maintain the setpoint over time. Therefore, new relays were procured. Instrument Maintenance Department (IMD) during D2R17 (October 2001) replaced the time delay relays. During post maintenance testing which included field calibration, IMD personnel found and left the relay setpoints high (two at 14 seconds and two at 15 seconds), but within the "As Left" limitations (13 +1- 2 seconds) of the calibration procedure, DIS 1300-01 and calculation, NED-I-EIC-0098.
On December 21, 2001, Technical Specification Amendment 191 was implemented, lowering the IC initiation time delay limit from On January 18, 2002, at 1920 hours0.0222 days <br />0.533 hours <br />0.00317 weeks <br />7.3056e-4 months <br />, IMD personnel performed IC instrumentation calibrations per procedure DIS 1300-01 as required by the TS surveillance requirements (SR) 3.3.5.2.3.
IMD reported that three of the four Isolation Condenser (IC) time delay relays were found outside of TS SR 3.3.5.2.3 AV. The As Found" values for the time delay relays were: 15.6 seconds for relay 2-595-117A; 15.4 seconds for relay 2-595-117B; 15.4 seconds for relay 2-595-117C and 14.8 seconds for relay 2-595-117D. At 2140 hours0.0248 days <br />0.594 hours <br />0.00354 weeks <br />8.1427e-4 months <br />, IMD completed DIS 1300-01 quarterly TS surveillance on the IC time delay relays, returning all of the relay calibrations to within TS requirements.
LICENSEE EVENT REPORT (LER) f33), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, And Budget, Washington, DC 20503. If an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) Dresden Nuclear Power Station Unit 2 05000237 NUMBER NUMBER (If more space is required, use additional copies of NRC Form 366A)(17) At 2213 hours0.0256 days <br />0.615 hours <br />0.00366 weeks <br />8.420465e-4 months <br />, IMD personnel generated a condition report for the time delay relays being out of TS tolerance. At 2347 hours0.0272 days <br />0.652 hours <br />0.00388 weeks <br />8.930335e-4 months <br />, Operations made the Emergency Notification System (ENS) — 8-hour notification to the NRC per 10 CFR 50.72(b)(3)(v)(B), for Isolation Condenser Relays found out of tolerance and informed the NRC Resident.
C. Cause of Event:
The root cause of the event was determined to be an inadequate setpoint calculation. The calculation specified an "As Left" tolerance with upper bound limits equal to the Technical Specification Allowable Value. (NRC Cause Code D). Contributing cause to this event include: The calculation allows the use of a stopwatch for determining the as found time delay relay values, IMD and engineering personnel expressed varying standards and expectations, and corporate and station engineering personnel allowed non-conservative decision making. (NRC Cause Code E)
D. Safety Analysis:
The Isolation Condenser time delay setting is limited to minimize inventory loss during Safety and Relief valve actuations on loss of both feedwater and normal heat sink with HPCI inoperable. The GE analysis assumes that the IC automatic initiation pressure setpoints are at their worst case settings when determining the time delay relay limitations. The IC automatic initiation would have been delayed by 0.4 seconds from the GE assumptions.
Nuclear Fuel Management evaluated the actual pressure setpoints and determined that the IC would have automatically initiated and provided its safety function for any time delay relay setting below 24.4 seconds. Safety function would have been delayed, not lost. Therefore, the safety significance of this event is minimal.
E. Corrective Actions:
Recalibrated all four time delay relays 2-595-117A, B, C, and D to within technical specification and near the setpoint.
Reinforced IMD and engineering personnel on the expectations regarding "As Left" values and the need to generate a CR when the condition is questionable, regardless of procedure or other documentation.
Revise Calculation NED-I-EIC-0098, specifying adequate margins to limits, and issue setpoint change.
(ATI - 91401-12) Revise Calculation NED-I-EIC-0098, specifying the use of chart recorders. (ATI 91401-14) Revise procedure DIS 1300-01 per the revision of NED-I-EIC-0098. (ATI 91401-15)
F. Previous Occurrences:
A review was conducted via a search of previous events of this type. No previous events of this type were found.
G. Component Failure Data:
N/A