Event Notification Report for December 16, 2001

BOTH HIGH FLOW INSTRUMENTATION FOR REACTOR WATER CLEANUP (RWCU) FOUND INOPERABLE.

During performance of routine surveillance testing on the PBAPS Unit 3 RWCU system high flow isolation instrumentation, it was discovered that both channels of isolation instrumentation were simultaneously inoperable. Both affected instruments were returned to operable status by 1828 hours on 12/16/01.

The RWCU system is designed to automatically isolate upon detection of a high flow condition. This isolation detection system utilizes two channels of differential pressure instrumentation for high flow detection. An isolation of the RWCU system can be accomplished by actuation of either channel of the logic. A single channel trip would result in either an inboard or outboard isolation. A failure of both channels would result in a failure of the system to isolate as required.

On 12/16/01 at 1111 hours, surveillance testing of the "A" channel high flow instrument (DPIS 3-12-124A) determined that this instrument failed to trip due to entrapped air in the sensing line. DPIS 3-12-124A was vented, retested, and returned to operable status at 1536 on 12/16/01.

At 1645 hours, surveillance testing of the "B" channel RWCU high flow instrument (DPIS 3-12-124B) determined that this instrument failed to trip due to entrapped air in the sensing line. DPIS 3-12-124B was vented, retested, and returned to operable status at 1828 on 12/16/01.

At 1645 on 12/16/01, it was determined that both channels of Unit 3 RWCU system high flow isolation instrumentation were simultaneously inoperable since the system had been placed in service during refueling outage 3R13. Unit 3 entered Mode 2 on 10/08/01 at 2221 hours, requiring the Primary Containment Isolation (PCIS) function to be operable.

Based on the above, this event is reportable under 10 CFR 50.72(b)(3)(v)(C).

The systems affected were the RWCU system isolation logic instruments, DPIS 3-12-124A and DPIS 3-12-124B. These instruments actuate on high system flow of 125%. No plant effects or transient occurred as a result of this event. The RWCU system isolation capability, on high system flow, was inoperable. This isolation capability is required whenever the RWCU system is in service with the reactor in Modes 1, 2, or 3.

DPISs 3-12-124A and 3-12-124B were filled, vented, tested satisfactorily, and returned to operable status.

A station investigation to determine the cause of the air entrapment is in progress.

The NRC resident inspector was notified of this event by the licensee.

* * * RETRACTION 1413 2/5/2002 FROM KOVALCHICK TAKEN BY STRANSKY * * *

"This notification is a retraction of Event Number (EN) 38576 which reported a loss of safety function of thc RWCU primary containment isolation valves due to entrapped air in the instrument sensing lines for the high flow isolation for both isolation valves.

"On December 16, 2001, the Reactor Water Cleanup (RWCU) system high flow isolation instrumentation routine surveillance was performed. During the routine surveillance, it was discovered that both high flow isolation instruments tripped outside their Technical Specification Allowable Value due to entrapped air in the system. resulting in both instruments being declared inoperable.

"An engineering evaluation determined that the test failure was caused by the testing methodology and concluded that both instruments were operable and the safety function was not impacted. Specifically, the evaluation determined that the entrapped air existed in the test lines only, which are isolated during normal plant operations.

"Therefore, because the safety function of the RWCU automatic isolation on high flow was maintained, this issue is not reportable under 10 CFR 50.72(b)(3)(v)(C).

"The NRC resident has been notified."

Notified R1DO (Doerflein).

INVALID PRIMARY AND SECONDARY CONTAINMENT ISOLATION DUE TO A SPURIOUS UPSCALE SPIKE OF REACTOR BUILDING VENTILATION RADIATION MONITOR B (60-Day Report)

The following text is a portion of a facsimile received from the licensee:

"Event Description"

"At 0018 hours on December 16, 2001, with the plant operating at 100 percent of rated thermal power, Reactor Building (Secondary Containment) Ventilation Exhaust Radiation Monitor B spiked upscale and immediately returned to normal."

"The radiation monitor upscale spike (trip) resulted in automatic closure of outboard isolation valves and therefore isolation of the following systems or functions:
* Primary Containment Drywell and Suppression Chamber pressure sensing for alarm and indication functions only,
* Primary Containment Continuous Atmosphere Monitoring (CAM) for particulate and gaseous radioactivity monitoring, and
* Primary Containment Hydrogen and Oxygen Analyzer B."

"The trip signal also resulted in automatic isolation of the Reactor Building (Secondary Containment) Ventilation system and starting of Standby Gas Treatment subsystem B to maintain the reactor building atmosphere at a slightly negative pressure."

"System performance was in accordance with the design. Examination of operating records indicated that the redundant radiation monitor, other monitoring systems, and the plant computer system did not detect any abnormal radioactivity. Shift operating and radiation protection personnel investigated and did not detect any abnormal radiological conditions. Examination of the radiation monitor did not reveal any indication of abnormal operation, and it was concluded that the trip signal had been a spurious invalid signal."

"Shift operating personnel completed restoration of the affected systems to normal at 0104 hours, 46 minutes after the event start."

"Actions Taken"

"1. Verified system response was in accordance with the design.
2. Investigated radiological conditions and determined they were normal.
3. Restored the affected systems to normal."

The licensee notified the NRC resident inspector.