PNO-III-96-026, on 960409,Unit 1 Reactor Shut Down Automatically When Maint Activities in Switchyard Resulted in Partial Loss of Offsite Power.On 960410 Second Unusual Event Declared Due to Heatup Rate in Excess of TS

PNO-III-96-026:on 960409,Unit 1 Reactor Shut Down Automatically When Maint Activities in Switchyard Resulted in Partial Loss of Offsite Power.On 960410 Second Unusual Event Declared Due to Heatup Rate in Excess of TS

ML20197H938
Person / Time
Site:	Clinton
Issue date:	04/11/1996
From:	Beverly Clayton, Roton J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
References
PNO-III-96-026, PNO-III-96-26, NUDOCS 9801020037
Download: ML20197H938 (1)

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fQfa sflm Cpf tpr 14hp PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-Ill 96-026

This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially -

received without verifict. tion or evaluation, and is basically all that is known by Region ill staff (Lisle, lilinois) on this date.-

Facility - Licensee Emergency Classification Illinois Power Co. - X Notification of Unusual Event Clinton 1 Alert Clinton, Illinois _ Site Area Emergency Dockets: 50-401 _

General Emergency Not App!icable

Subject:

REACTOR TRIP LEADS TO TWO UNUSUAL EVENTS On April 9,1996, at 1:30 p.m. (CDT), Unit i reactor shut down automatically when maintenance activities in the switchyard resulted in a patal loss of offsite power. Initial control rod position indications immediately available to the operators were inconclusive. The oparators initiated a manual shutdv ,1 and an attemate rod insertion. Control rods were confirmed to be fully mserted by using attemate rod position

_ instrumentation.

An Unusual Event was declared under the licensee's emergency plan due to the hitia! appearance of control rods not inserting upon the initial shutdown signal. Later a computer printout ofrthe event verified that the

, control rods fully inserted on the automatic shutdown signal as designed. ,

The Unusual Event was terminated at 8:05 p.m. (CDT) following

'twification of proper control rod response and full restoration of offsite power.

Foll ing recovery activities after the shutdown, a second Unusual Event was declared under the licensee's emergency plan at 3:00 a.m. (CDT) on April 10,1996, due to indicaton of a heatup rate in excess of Technical Specifications. The reactor vessel bottom head drain temperature increased greater than 100 degrees Fahrenheit per hour. The licenseo was tracking temperature at five minute inteivals and between 10:10 p.m. and 11:10 p.m, (CDT) there was a five minute period which exceeded the requirement.

The licensee terminated the Unusual Event at 1945 CDT based on an [

. engineering evaluation which determined that this event was within the analyzed design basis of the plant. The 'B' recirculation pump has been placed in service to prevent thermal stratification. The licensee N/m 3

6 p' nhticipates the Unit being shutdown for approximately threr days.

The State of Illinois will be notified. The licensee has issued a news announcement about the reactor shutdown. Iriformation in this preliminary notification has been reviewed with licensee management.

The licensee notified the NRC Operretions Center at 2:13 (CDT) on April 9, 1996, and at 3:44 a.m. (CDT) on April 10,1996. This information is current as of 9:50 am. on April 11,1996.

Contact:

J.R. ROTON B. CLAYTON (708)829-9602 (708)829-9602 4

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PDR -I&E PNO-III-96-026 PDR