ML20040E942

RO 81-7:on 811104,during Surveillance Instruction 90.12, Safety Injection Actuation Occurred.Caused by Shorted Connector Wire Between Low Pressure Logic Board Pins in Train B Solid State Protection Sys

ML20040E942
Person / Time
Site:	Sequoyah
Issue date:	01/25/1982
From:	Green H TENNESSEE VALLEY AUTHORITY
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
RO-81-7, NUDOCS 8202080114
Download: ML20040E942 (4)

Text

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TENNESSEE VALLEY AUTHORITY CHATTANOOGA, TENNESSEE 374o1 .

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1750 Chestnut Street Tower II January' 25, 1982 .<3 t t'*ig

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Mr. James P. O'Reilly, Director - ;8 U.S. Nuclear Regulatory Commissio

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Region II 101 Marietta Street, Suite 3100 -

Atlanta, Georgia 30303

Dear Mr. O'Reilly:

TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT 2 - DOCKET NO. 50-328 - FACILITY OPERATING LICENSE DPR SPECIAL REPORT 81-7 The enclosed report provides details concerning an emergency core cooling system injection into the reactor coolant system. This report is submitted in accordance with Sequoyah unit 1 Technical Specification 3.5.2.

Very truly yours, TENNESSEE VALLEY AUTHORITY s t 1- . J. Gree.

irector of Nuc car Power Enclosure cc (Enclosure):

Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555 Records Center Institute of Nuclear Power Operations 1820 Water Place Atlanta, Georgia 30339 NRC Inspector, Sequoyah OFEtdANO .a .

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SEQUOYAH NUCLEAR PLANT SPECIAL REPORT 81 UNIT 2 Conditions of Unit 2 Unit 2 Mode 3 547 degrees F, 2235 psig, 0% power Event Description At 0720 CST on November 4, 1981, while performing surveillance instruction (SI) 90.12, a safety injection actuation occurred.

Probable Cause Pressurizer pressure switch 1-PS-68-340D/B (protection set I) was placed in the tripped condition to perform the SI on the low pressurizer pressure bistable. Approximately twenty minutes af ter the pressure switch was placed in the tripped condition, the safety injection actuation occurred.

Subsequent testing showed that when 1-PS-68-340D/B was placed in the

. tripped condition, indication was received that protection set'III pressurizer low pressure bistable (1-PS-68-323D/E) was also tripped. This gave a two out of four logic of low pressurizer pressure which actuated the safety injection. An investigation indicated that the safety injection actuation had originated only from the train B solid state protection system (SSPS).

Troubleshooting the tr in B SSPS revealed a shorted connector wire between.

pressurizer low pressure logic board pins.

Sequoyah Unit 2 Technical Specifications limiting condition for. operation 3.5.2 requires that the current value of the usage factor of safety injection nozzles be included in the Special Report if the value exceeds 0.7. The usage factor for the affected nozzles will not exceed 0.7 if the emergency core cooling system occurrences are less than thirty five cycles and this is the second such event for Unit 2. (Reference IE circular 78-05)

Corrective Actions I

The defective wire to the logic board pins was clipped and reconnected and the SSPS returned to normal. To verify proper operation 1-PS-68-340D/B bistable- 3 l switch was returned to the tripped condition with normal response experienced.

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1750 Chestnut Street Tower II January 25, 1982 Mr. James P. O'Reilly, Director U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region II 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303

Dear Mr. O'Reilly:

TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAT. PLANT UNIT 2 - DOCKET No. 50-328 - FACILITY OPERATING LICENSE DPR SPECIAL REPORT 81-7 The enclosed report provides details concerning an emergency core cooling system injection into the reactor coolant system. This report is submitted in accordance with Sequoyah unit 1 Technical Specification 3.5.2.

Very truly yours, TENNESSEE VALLEY AUTHORITY

'. t F .J.Greef.I ~

irector of Nuc ear Poder Enclosure cc (Enclosure):

Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555 Records Center Institute of Nuclear Power Operations 1820 Water Place Atlanta, Georgia 30339 NRC Inspector, Sequoyah

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SEQUOYAH NUCLEAR PLANT SPECIAL REPORT 81-7 UNIT 2 Conditions of Unit 2 Unit 2 Mode 3 547 degrees F, 2235 psig, 0% power Event Description At 0720 CST on November 4,1981, while performing surveillance instruction (SI) 90.12, a safety injection actuation occurred. l I

Probable Cause Pressurizer pressure evitch 1-PS-68-340D/B (protection set I) was placed in the tripped condition to perform the SI on the low pressurizer pressure bistable. Approximately twenty minutes af ter the. pressure switch was placed in the tripped condition, the safety injection actuation occurred.

Subsequent testing showed that when 1-PS-68-340D/B was placed in the tripped condition, indication was received that protection set,III pressurizer low pressure bistable (1-PS-68-323D/E). was also tripped. This gave'a two out of four logic of low pressurizer pressure which actuated the safety

• injection. An investigation indicated that the safety injection actuation had originated only from the train B solid state protection system (SSPS).

Troubleshooting.the train B SSPS revealed a shorted connector wire between pressurizer low pressure logic board pins, i

Sequoyah Unit 2. Technical Specifications limiting condition for operation 3.5.2

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requires that the current value of the usage factor of safety injection nozzles be included in the Special Report if the value. exceeds.0.7. The usage factor for the affected nozzles will not exceed 0.7 if the emergency core cooling system occurrences are less than thirty f1ve cycles and this is the second such' event for Unit 2. (Reference IE circular 78-05)

Corrective Actions The defective wire to the logic boarc pins was clipped and reconnected and the SSPS returned to normal. To' verify prorar operation 1-PS-68-340D/B bistable.

switch was returned to the tripped condition with normal response experienced.

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