05000361/LER-2002-004
| Docket Number | |
| Event date: | 07-03-2002 |
|---|---|
| Report date: | 08-30-2002 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i) |
| 3612002004R00 - NRC Website | |
U.S. NUCLEAR REGULATORY COMMISSION LER NUMBER (6) PAGE (3) FACILITY NANE(1) DOCKET (2) — 004 — I 00 2002 Event Date:
� July 3, 2002 Discovery Date: � July 9, 2002 Reactor Vendor: � Combustion Engineering � Combustion Engineering Power: � 20 percent � 100 percent
BACKGROUND:
Technical Specification (TS) Limiting Condition for Operation (LCO) 3.1.7, Regulating Control Element Assembly (CEA) [EIIS code: JD] Insertion Limits, applicable in Modes 1 and 2, requires in part the Power Dependent Insertion Limit (PDIL) alarm circuit to be operable. TS Surveillance Requirement (SR) 3.1.7.3 verifies the PDIL alarm circuit (alerts operators that limits are being approached or exceeded) is operable at least every 31 days.
TS LCO 3.2.1, Linear Heat Rate (LHR), applicable in Mode 1 when thermal power (RTP) is above 20 percent RTP, requires the LHR to not exceed the limits specified in the Core Operating Limits Report (COLR). TS SR 3.2.1.3 verifies at least every 31 days that the Core Operating Limits Supervisory System (COLSS) margin alarm (alerts operators that limits are being approached) actuates at a thermal poWer TS LCO 3.2.3, Azimuthal Power Tilt (Tq), applicable in Mode 1 when thermal power is above 20 percent RTP, requires the measured Tq to be (CPCs). TS SR 3.2.3.2 verifies at least every 31 days that the COLSS azimuthal tilt alarm (alerts operators when Tq exceeds its operating limit) is actuated at a Tq value CPCs.
TS LCO 3.2.4, Departure From Nucleate Boiling Ratio (DNBR), applicable in Mode 1 when thermal power is above 20 percent RTP, requires when COLSS is in service that DNBR be maintained by one of the following methods:
a. Maintaining COLSS calculated core power limit based on DNBR when either one or both Control Element Assembly Calculators (CEACs) are operable; b. Maintaining COLSS calculated core power limit based on DNBR decreased by 13.0 percent RTP when neither CEAC is operable.
TS SR 3.2.4.3 verifies at least every 31 days that the COLSS margin alarm (alerts operators that limits are being approached) actuates at a thermal power DNBR.
TS SR 3.0.4 prohibits entry into a mode or other specified condition (such as greater than 20 percent RTP) in the Applicability of an LCO unless the TS LCO's SRs have been met.
U.S. NUCLEAR REGULATORY COMMISSION — 004 — I 00 2002 Procedure S023-3-3.41, COLSS/COLSS Backup Computer System (CBCS) Operability and Computer Surveillances, Attachments 1 and 2 are used to perform the COLSS and CBCS Operability surveillances. Attachments 4 and 5 of this procedure are used to perform the alarm surveillances.
DESCRIPTION OF THE EVENT:
On June 29, 2002, while Unit 2 was being returned to power operation following a planned refueling outage, operators (utility, licensed) performed the COLSS/CBCS surveillance tests. Because reactor power was less than 15 percent at the time, only the PDIL alarm functions (required in Modes 1 and 2) were tested, as prescribed by procedure.
On July 2, 2002, while reactor power was between 15 and 20 percent RTP, computer technicians (utility, non-licensed) performed the procedure S023-3-3.41 Attachments 1 and 2 surveillances (COLSS and CBCS, respectively). The technicians did not recognize that Attachments 4 and 5 had been completed for the PDIL alarm portion only, and the procedure did not guide them to a different conclusion (defective procedure).
On July 3, 2002 (event date), at approximately 0100 PDT, operators (utility, licensed) raised reactor power above 20 percent RTP.
On July 9, 2002 (discovery date), at approximately 1500 PDT, while reviewing completed surveillance procedures, SCE discovered the missed COLSS/CBCS alarm surveillances (AR020700480). At approximately 1712 PDT the same day, the missed surveillances were satisfactorily performed which provide reasonable assurance that the COLSS/CBCS alarms had been operable at the time reactor power exceeded 20 percent RTP.
10CFR50.73(a)(2)(i)(B) states that any operation prohibited by the plant's TS is reportable unless the event consisted "solely" of a late surveillance test where the oversight was corrected, and the equipment was found to be capable of performing its specified safety functions. Because the event reported herein also involved entering a mode or condition that required the prior performance of the surveillance, this event is being reported as an operation prohibited by TS SR 3.0.4.
CAUSE OF THE EVENT:
The cause of this event was a defective procedure. Procedure S023-3-3.41, Attachments 4 and 5, directs the user to mark steps omitted when power is less than 15 percent RTP as "N/A". The procedure directs the user to enter the "valid through" date on the Attachments by adding 31 days to the date the work was done. This gave the appearance that the entire surveillance had been completed when in fact only the PDIL portion was completed. Therefore, when the computer technicians performed the attachment 1 & 2 SR's, it appeared that all attachment 4 & 5 were complete & valid. The procedure does not direct the user to check for steps that may have been marked "N/A.
U.S. NUCLEAR REGULATORY COMMISSION DOCKET (2) PAGE (3) 05000-361 FACILITY NAME(1) LER NUMBER A) 2002 — 004 — I D 00
CORRECTIVE ACTIONS:
- Upon discovery on July 9, 2002, the missed surveillances were performed satisfactorily, bringing the plant into full compliance with TS LCOs 3.2.1, 3.2.3 and 3.2.4.
- A Pre-Shift Brief summarizing the event and the apparent cause was read to Operations crews.
- A Priority Reading Assignment, more detailed than the Pre-Shift Brief, was made available to all operating crews.
- Procedure S023-3-3.41 will be revised to reduce the probability of similar events.
SAFETY SIGNIFICANCE
- SCE concludes there was very little to no safety significance to these events because there was no loss of alarm function. Upon discovery, SCE satisfactorily performed the required surveillances, which provided reasonable assurance that COLSS and CBCS alarms were operable when power was raised above 20 percent RTP.
ADDITIONAL INFORMATION:
- SCE is also reporting herein two similar events that occurred on November 17, 2000, for Unit 2 and on February 3, 2001, for Unit 3. SCE concludes that these two separate events resulted from the same cause as the event reported herein. In both events, the subsequent surveillances provide reasonable assurance that COLSS and CBCS alarms were operable at the time 20 percent RTP was exceeded The corrective actions described above, had they been in-place, would have prevented those events.
- In the past three years, there have been no reported events caused by a surveillance procedure that did not properly account for changes in plant conditions.