05000331/LER-2002-003
| Docket Number | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown |
| Initial Reporting | |
| 3312002003R00 - NRC Website | |
FACILITY NAME (1) Duane Arnold Energy Center DOCKET NUMBER (2)
I. Description of Event:
On August 19, 2002 with the plant at 94 percent power, Reactor Core Isolation Cooling (RCIC) Technical Specification (TS) LCO 3.5.3 Condition A, RCIC System inoperable, was entered for planned maintenance. TS LCO 3.5.3 Condition A was entered at 1228 and was scheduled for about 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. Planned maintenance was completed on August 21, 2002 at 0356. Surveillance Test Procedure (STP) 3.5.3-02, RCIC System Operability Test, failed on August 21, 2002 due to oil flooding at the RCIC turbine governor end bearing. Troubleshooting activities and review of past industry operating experience began.
On August 30, 2002 the plant was shutdown to perform repairs on the drywell cooling system On August 31, 2002 at 2338, TS LCO 3.5.3 Condition A was exited because RCIC was no longer required to be operable with reactor pressure below 150 psig (exited the mode of applicability).
At 1059 on September 1, 2002, with drywell cooler repairs complete, the plant commenced startup. The cause of RCIC oil problems was believed to have been resolved following a successful two hour RCIC run. However, while testing RCIC at approximately 150 psig reactor pressure during plant startup, oil flooding recurred. At 1835 on September 1, 2002, RCIC was declared inoperable and the DAEC reentered the TS LCO 3.5.3 Condition A. RCIC oil system pressure was adjusted and testing performed. Following successful completion of STP 3.5.3-03, Low Pressure RCIC System Flow Rate Test, RCIC was declared operable and TS LCO 3.5.3 Condition A was exited at 0319 on September 2, 2002. Activities to increase reactor power resumed. At 1327 on September 2, 2002 RCIC post-startup operability testing at reactor pressure greater than 940 psig was begun, however, the testing was unsuccessful.
On September 2, 2002 at 1500, TS LCO 3.5.3 Condition B, was entered following failure of STP 3.5.3-06, RCIC System Post-Startup Operability Test performed at reactor pressure greater than 940 psig, due to governor end bearing flooding. Plant shutdown was initiated on September 2, 2002 at 2100 in accordance with TS 3.5.3 Condition B.
On September 3, 2002 a more systematic approach to troubleshooting and repair of the RCIC oil system commenced. Oil "system-modifications were riia-dd—cTn—Sdpte-mber-5 and 6;20027-Following -successful uncoupled RCIC runs on September 7, 2002, RCIC was declared operable and the plant commenced start up.
STP 3.5.3-03, Low Pressure RCIC System Flow Rate Test, was completed satisfactorily at 1553 on September 8, 2002. STP 3.5.3-06, RCIC System Post-Startup Operability Test, was completed satisfactorily at 0235 on September 9, 2002. TS LCO 3.5.3 Condition B was exited on September 9, 2002 at 0316.
II. Cause of Event:
The introduction and entrainment of air in the RCIC oil system was the cause of the repeated RCIC test failures.
Root Causes include:
1. Industry operating experience was not used effectively. RCIC oil system design and maintenance improvements dating as far back as 1977 had, in many cases, not been implemented.
— — U.S. NUCLEAR REGULATORY COMMISSION FACILITY NAME (1) PAGE (3) LER NUMBER (6) DOCKET NUMBER (2) II. Cause of Event continued:
2. Organizational response to the repeated RCIC test failures was inadequate because no formal process existed for troubleshooting and responding to events other than forced outages and trips.
3. Training of System Engineers does not adequately familiarize them with industry operating experience when they are assigned new systems.
_111. Assessment of Safety Consequences: -- The RCIC system provides makeup water to the reactor vessel following a reactor vessel isolation to ensure adequate core cooling. The RCIC system provides core cooling during reactor shutdown by pumping makeup water into the reactor vessel in case of a loss of flow from the feedwater system and is activated in time to preclude conditions that lead to inadequate core cooling.
leakage. Drywell leakage was a well water leak on a cooler, unrelated to RCIC concerns. This plant shutdown had no impact on the RCIC maintenance v‘ork.
There were no actual safety consequences associated with this event. The High Pressure Coolant Injection (HPCI) system was operable during this event. Potential safety consequences were minimal.
There was no impact on public health and safety.
There were other structures, systems and components inoperable at the start of this event, however, none contributed to the significance of the event. Variations in plant operating modes would not have resulted in increased consequences.
IV. Corrective Actions:
A. Conipleted:
The installation of Engineered Maintenance Action (EMA) 60432 eliminated the RCIC oil system flooding. This EMA rerouted the PSV 2475 discharge line to the equalizing header, enlarged the oil drain line and improved the oil system venting.
B The following Correction Action documents (ARs) have been initiated to address the root causes identified:
Root Cause 1:
- Develop an effective process for distribution, screening and use of system related operational experience (AR 32940, assigned to System Engineering, due 11/15/02).
FACILITY NAME (1) Duane Arnold Energy Center DOCKET NUMBER (2) LER NUMBER (6 IV. Corrective Actions continued:
- Incorporate the Terry Turbine User Group maintenance guidance for RCIC and HPCI turbines into DAEC procedures (AR 32281, assigned to System Engineering, due 9/3/03)
- Incorporate industry operating experience into RCIC turbine oil system maintenance procedures (AR32244, assigned to Procedures, completed 10/25/02).
- Revise the RCIC turbine oil system maintenance procedures concerning venting air after maintenance (AR 32502, assigned to Procedures, due 12/17/02).
- Inadequate RCIC oil system site glass level indications have been corrected (AR 32317, assigned to System Engineenng,-completed 9/2/02) Root Cause 2:
- Develop a process (i.e., staffing, procedures, communications, etc.)for responding to plant events (AR 32680, assigned to Work Management, due 1/7/03).
- Additionally, actions are in place to implement a systematic troubleshooting procedure (AR 32248, assigned to System Engineering, due 11/15/02).
Root Cause 3.
- Develop a plan to improve the training and qualification, and system familiarization process for System Engineers (AR 32941, assigned to System Engineering, due 11/15/02).
V. Additional Information:
Previous Similar Occurrences:
DAEC experienced RCIC oil system leakage on two previous occasions. In 1993, oil misting occurred when the RCIC turbine was operated at greater than rated speed. The 1993 oil misting was dissimilar to this event in that it was attributed to the higher turbine speed.
In 1995, oil whipping and flooding at the governor end bearing occurred and was attributed to an incorrect oil level. Oil level was corrected and no further oil whipping or flooding occurred. The 1995 oil flooding was dissimilar to this event in that there was no air entrained in the oil system.
EIIS System and Component Codes:
Reactor Core Isolation Cooling (RCIC): BN Drywell Cooling: VB High Pressure Coolant Injection (HPCI): BJ This event is being submitted pursuant to 10CFR50.73(a)(2)(i)(A). Event notification39164.