05000483/LER-2001-001

LER-2001-001,

Docket Number
Event date:
Report date:
4832001001R00 - NRC Website

DESCRIPTION OF EVENT:

At 09:28 on 01-12-01, with the Plant operating at full power, an unplanned actuation of the "A" Reactor Trip Breaker (SB52SB102BRTA) occurred during Actuation Logic Testing of "A" Solid State Protection System (SSPS), in accordance with ISF-SB-00A29 (FCTNAL-ANAL; SSPS TRAIN A FCTNAL TEST). The "A" Reactor Trip Breaker Bypass Breaker had previously been closed as part of the testing procedure; therefore the "A" Trip Breaker actuation had no effect on Plant operation.

The initial conditions were established per ISF-SB-00A29 and the testing began. Due to a missed step in the procedure, the INPUT ERROR INHIBIT switch for the "A" train SSPS had not been placed in the INHIBIT position. Placing the switch in the INHIBIT position generates an Intermediate Range Rodstop Block and blocks energizing the source range detector. Immediately prior to this step is a caution statement that explains the function of the switch and a requirement to notify the Reactor Operator prior to placing the switch in INHIBIT.

The Technician read the statement, notified the Reactor Operator as required, and incorrectly initialed the following step as complete, but failed to reposition the switch. The test proceeded without incident until the Technicians began rotating logic "A" test switch. The Technicians did not receive proper indication when it was rotated to position 14. The procedure allows the Technicians to cycle the switch, to clean the contacts.

When the Technicians cycled the switch, the "A" Reactor Trip Breaker opened and the Control Room received annunciator 56B, RCS Supervision, notified Engineering and initiated an immediate review of the events. During the review it was discovered that the INPUT ERROR INHIBIT switch had not been placed in the INHIBIT position, contrary to the procedure. The switch was placed in INHIBIT and the test was completed.

At 12:40, the NRC Operations Center was notified of this event in compliance with 10 CFR 50.72 (b) (2) (ii).

BASIS FOR REPORTABILITY:

This event was determined to be reportable per 10 CFR 50.72 (b) (2) (ii) / 10CFR 50.73 (a) (2) (iv) as an event that resulted in an automatic actuation of an Engineered Safety Feature (ESF).

CONDITION AT TIME OF EVENT:

MODE 1, Power Operations-100%

ROOT CAUSE:

The I&C technician had not placed the INPUT ERROR INHIBIT switch in INHIBIT even though he had signed the step off. The test procedure contained a caution that required action ( notify the Reactor Operator) prior to performing the step ( place switch in INHIBIT ). Grouping both actions together and providing a single sign off contributed to the likelihood of error. This missed procedure step, by the I&C technician, left the INPUT ERROR INHIBIT switch in the NORMAL position. This allowed the test signal to actuate the "A" Reactor Trip Breaker.

CORRECTIVE ACTIONS:

The test procedure (ISF-SB-00A32) for "B" train has been revised to remove the notification from the caution and make it a separate step.

The test procedure (ISF-SB-00A29) for "A" train will be revised prior to the next use, to remove the notification from the caution and make it a separate step.

This event will be included in the Operating Experience for future Actuation Logic Testing of Solid State Protection System (SSPS) work.

SAFETY SIGNIFICANCE:

The risk assessment (10CFR50.65(a)(4)) for performing this testing includes the possibility of a Reactor Trip. This event did not result in a Reactor Trip or plant transient. The missed procedure step did not result in any additional quantifiable risk to the health and safety of the public.

PREVIOUS OCCURRENCES:

A review of the previous three years determined that there have not been any similar events.

FOOTNOTES:

The system and component codes listed below are from IEEE Standard 805-1984 and IEEE Standard 803A-1984, respectively.

System � JD Component BRK