05000395/LER-2003-006
| Virgil C. Summer Nuclear Station | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(IV)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3952003006R00 - NRC Website | |
PLANT IDENTIFICATION
Westinghouse - Pressurized Water Reactor E01TIPMENT IDENTIFICATION Digital Rod Position Indicator Panel
IDENTIFICATION OF EVENT
The event was Identified during performance of Surveillance Test Procedure (STP) 106.002, Rod Position Indication Operational Test. Rod Control bank "C" was being withdrawn (RCS boron concentration had been verified adequate to ensure the effective multiplication factor keff was less than or equal to 0.95). When control bank "C" reached 36 steps, the Digital Rod Position Indicator system (DRPI) panel went to 18 steps for rod M-4. This condition was identified in Condition Event Report (CER) 03-4172.
EVENT DATE
November 21, 2003
REPORT DATE
January 20, 2004
CONDITIONS PRIOR TO EVENT
The plant was in Mode 3, normal operating pressure and temperature, and preparations were being made for a plant start-up.
DESCRIPTION OF EVENT
On November 21, 2003, the V. C. Summer Nuclear Station was performing control rod testing (Mode 3) in preparation for plant start-up, following refueling outage-14. The testing is in accordance with Surveillance Test Procedure (STP) 106.002, Rod Position Indication Operational Test. The Reactor Trip Breakers were closed and Control Rod bank "C" was being withdrawn. When Control Rod bank "C" reached 36 steps, the Digital Rod Position Indication (DRPI) for Rod M-4 went to 18 steps. At 0835, control rod motion was stopped and Abnormal V.C.Summer Nuclear Station Operating Procedure (AOP) 403.5, Stuck or Misaligned Control Rod, was entered after verification that the procedure was applicable in the current plant condition. At 0910, while taking action per the ADP, it was determined that both channels of DRPI were not functioning properly. Per the V. C. Summer Nuclear Station Technical Specifications (TS) Sections 3.1.3.3 and 3.10.5, with both channels of DRPI inoperable, the Reactor Trip Breakers must immediately be opened. This action was satisfied at approximately 0910.
The Emergency Operating Procedure (EOP) for a plant trip was entered. At 0915, the EOP was exited with the plant stable in Mode 3. This event is being reported under 10 CFR 50.73(a)(2)(iv)(A).
ANALYSIS OF EVENT
Plant TS ensures the health and safety of the public is maintained by providing actions to place the plant in a safe configuration, if specific equipment is inoperable for a predetermined amount of time, ranging from less than one hour to many hours. The TS assure the assumptions in the plant's safety analysis are satisfied. This is accomplished by having the correct equipment completely available or taking actions that may include placing the plant in a condition where the equipment is not required. In this particular case, the Control Rod indication is not required when all control rods are fully inserted and the Reactor Trip Breakers are open.
The condition was non-significant from a safety viewpoint. When conditions became abnormal, and once the determination of operability for the DRPI system was made, the TS action was completed in a timely manner. This was determined to be an indication problem and the actual position of the control rods were as required by TS and the testing procedure. The reactor had not been taken critical at this point however, the plant was shut down and boron concentration verified to ensure that additional margin was available to preclude inadvertent criticality. Only one bank of rods was partially out of the core, with the remaining control rods fully inserted as required by TS. When the Reactor Trip Breakers were opened, all control rods went to bottom as required and expected. There were no unexpected reactivity excursions and all equipment operated as expected.
CORRECTIVE ACTIONS
The DRPI system was repaired and tested to assure acceptable performance was obtained prior to closing the Reactor Trip Breakers. Investigation determined that an encoder card for rod M-4 had failed and was providing the incorrect indication. After card replacement, post maintenance testing determined that the condition was resolved, and rod testing recommenced.
PRIOR OCCURRENCES
None
2. DOCKET