05000331/LER-2003-002
| Duane Arnold Energy Center | |
| Event date: | |
|---|---|
| Report date: | |
| 3312003002R00 - NRC Website | |
I. Description of Event:
On February 11, 2003, with the plant in MODE 4 (Cold Shutdown), the on-shift Operating crew was preparing to flush the Control Rod Drive (CRD) System as part of the plant recovery efforts from a reactor coolant chemistry excursion event on January 31, 2003 (LER 05000331/2003-001-00). The CRD flushing process involved individually cycling each Control Rod from the fully inserted to fully withdrawn and back to the fully inserted position three times. All 89 CRDs were planned to be cycled.
The CRD movement was being controlled by Surveillance Test Procedure (STP) 3.10.4-01, "Single Control Rod Withdrawal (Cold Shutdown) and STP NS550004, "CRD Friction Testing.
No structures, systems, or components were inoperable at this time that contributed to this event.
At 0906 hours0.0105 days <br />0.252 hours <br />0.0015 weeks <br />3.44733e-4 months <br />, Special Operations Technical Specification (TS) 3.10.4, "Single Control Rod Withdrawal - Cold Shutdown" was entered to begin the CRD cycling. TS 3.10.4 invokes TS 3.9.2, "Refuel Position One-Rod-Out Interlock" as a sub-tiered requirement (b.1) in the Limiting Condition for Operation (LCO). Surveillance Requirement (SR) 3.10.4.1 requires that the SRs for TS 3.9.2 (among others) be met.
SR 3.9.2.1 requires a verification every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> that the Reactor Mode Switch be locked in the Refuel position. The TS Bases for SR 3.9.2.1 defines "locking" to include removing the key from the Mode Switch.
At 0924 hours0.0107 days <br />0.257 hours <br />0.00153 weeks <br />3.51582e-4 months <br />, the Mode Switch was placed in the Refuel position and Control Rod cycling commenced at 0945 hours0.0109 days <br />0.263 hours <br />0.00156 weeks <br />3.595725e-4 months <br /> and continued until 1726 hours0.02 days <br />0.479 hours <br />0.00285 weeks <br />6.56743e-4 months <br />. During this interval, 23 Control Rods were cycled.
At 1834 hours0.0212 days <br />0.509 hours <br />0.00303 weeks <br />6.97837e-4 months <br />, a scheduled Control Room shift change was made. In the process of preparing to resume CRD flushing (approx. 2041 hours0.0236 days <br />0.567 hours <br />0.00337 weeks <br />7.766005e-4 months <br />), the new Control Room crew noted that while the Mode Switch was in the Refuel position, with the key turned to the locked position; the key was still in the Mode Switch. The crew recognized that this was not in conformance with the TS Bases for SR 3.9.2.1 and that the previous crew had potentially violated TS during the earlier CRD cycling. A corrective action report was written (Action Request CAP025551) to document the issue. Subsequent evaluation (Action Request CE000307) determined that the failure to remove the key during the CRD cycling was in violation of SR 3.9.2.1, and, in turn TS 3.10.4.
Control Rod cycling was re-commenced at 0021 hours2.430556e-4 days <br />0.00583 hours <br />3.472222e-5 weeks <br />7.9905e-6 months <br /> on February 12, with the key properly removed from the Mode Switch, and subsequently completed without further incidents.
II. Cause of Event:
An Apparent Cause evaluation was performed under Action Request (ACE001061), which concluded that the event was caused by a combination of factors.
The primary cause was inadequate procedures, which did not specifically direct removal of the key from the Mode-Switch aspart of the process of locking the switch in the Refuel position; specifically STP 3.10.4-01, which was being used to control this evolution, contains the step to "LOCK the MODE SWITCH in the REFUEL position." However, no additional information regarding removal of the key was included.
A secondary cause was a lack of familiarity with the TS Bases for SR 3.9.2.1, which contains the requirement to remove the key, by the initial Control Room crew. The relieving crew was aware of the requirement and recognized the potential problem when the key was discovered in the Mode Switch.
III. Assessment of Safety Consequences:
There was no safety significance to this event, as the Mode Switch remained locked in the Refuel position during all Control Rod movements. This event was a failure to properly execute an administrative control to remove the key from the switch as discussed in the Bases to SR 3.9.2.1.
IV. Corrective Actions:
As part of closure of Action Request (PCR026758), an electronic search of the plant procedureS' was conducted to identify instances of the requirement to lock the Mode Switch in the Refuel position. Procedure Work Requests (PWR) were initiated to revise the identified procedures to add a specific requirement to remove the key from the Mode Switch.
All identified procedure changes have been completed (STP 3.0.0-03/PWR 20750; STP 3.9.1-01/PWR 20751; STP 3.10.4-01/PWR 20752; STP 3.10.3-03/PWR 20799; 01856.1/PWR 20800; STP 3.10.3-02/PWR 20801).
An Operations Department "Hot Item" was written to inform the Operations staff of this incident. Hot Items are read by the Control Room crew as part of assuming their shift.
V. Additional Information:
Previous Similar Occurrences:
Since implementation of the conversion to Improved Standard TS in 1998, which involved an extensive review of all STPs, no other incidents of inadequate surveillancitegt—protedures-leading to non-compliance with TS requirements were found. In 1999, there was an incident (Ref. LER 05000331/99-002) in which it was determined that the TS SR was incorrectly written, leading to a performance problem with the as-written STP. A Notice of Enforcement Discretion was granted by the NRC and the SR was corrected by an exigent TS amendment. The corrective actions taken as a result of that event would not have precluded this current problem.
EIIS System and Component Codes:
Control Rod Drive: AA Reactor Mode Switch: JC/JD