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This 60-day telephone notification is bein … This 60-day telephone notification is being submitted in accordance with paragraphs 10 CFR 50.73(a)(1) and 50.73(a)(2)(iv)(A) to report two related invalid actuations of the Containment Vent Isolation System at Watts Bar Nuclear Plant Unit 1 (WBN-1).</br>On April 14, 2015 at 2101 EDT, a sample pump failed on the WBN-1 Train B containment purge exhaust radiation monitor (1-RM-90-131), prompting control room operators to enter Conditions A and B of Technical Specification (TS) Limiting Condition for Operation (LCO) 3.3.6, Containment Vent Isolation Instrumentation and Condition A of LCO 3.6.3, Containment Isolation Valves. </br>On April 15, 2015 at 1207 EDT, 1-RM-90-131 radiation readings increased sharply (spiked), initiating an invalid Containment Vent Isolation (CVI) actuation. The spike occurred following troubleshooting and repairs to 1-RM-90-131 when maintenance technicians agitated the motor starter enclosure in an attempt to free a stuck auxiliary contact that controls local indication. As a result of the CVI actuation, flow to lower containment radiation monitor (1-RM-90-106) was isolated, prompting control room operators to enter Condition B of LCO 3.4.15, RCS Leakage Detection Instrumentation. At 1634 EDT, control room operators exited the TS 3.4.15 condition when 1-RM-90-106 was returned to service.</br>On April 17, 2015 at 1327 EDT, control room operators exited LCO 3.3.6 Conditions A and B and LCO 3.6.3 Condition A when sample pump repairs were completed on 1-RM-90-131. </br>On April 19, 2015 at 1550 EDT, 1-RM-90-131 radiation readings spiked and initiated a CVI, prompting control room operators to enter TS LCO 3.4.15 Condition B and LCO 3.3.6 Condition A, until flow was restored to 1-RM-90-106 at 1636 EDT and 1-RM-90-131 was returned to service on April 26, 2015 at 1229 EDT. </br>Each CVI was documented in accordance with the corrective action program, and TVA completed an equipment apparent cause evaluation (CR 1015781) that revealed the cause of the two CVI actuations was the result of a faulted Start/Stop control unit. TVA replaced the faulted control unit.</br>In both instances, the CVI actuations resulted from invalid signals and were limited to a single piece of Train B equipment. There was no loss of safety function and there were no actual safety consequences during the events.</br>The NRC Resident Inspector has been informed. NRC Resident Inspector has been informed.
16:07:00, 15 April 2015 +
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14:52:00, 12 June 2015 +
16:07:00, 15 April 2015 +
This 60-day telephone notification is bein … This 60-day telephone notification is being submitted in accordance with paragraphs 10 CFR 50.73(a)(1) and 50.73(a)(2)(iv)(A) to report two related invalid actuations of the Containment Vent Isolation System at Watts Bar Nuclear Plant Unit 1 (WBN-1).</br>On April 14, 2015 at 2101 EDT, a sample pump failed on the WBN-1 Train B containment purge exhaust radiation monitor (1-RM-90-131), prompting control room operators to enter Conditions A and B of Technical Specification (TS) Limiting Condition for Operation (LCO) 3.3.6, Containment Vent Isolation Instrumentation and Condition A of LCO 3.6.3, Containment Isolation Valves. </br>On April 15, 2015 at 1207 EDT, 1-RM-90-131 radiation readings increased sharply (spiked), initiating an invalid Containment Vent Isolation (CVI) actuation. The spike occurred following troubleshooting and repairs to 1-RM-90-131 when maintenance technicians agitated the motor starter enclosure in an attempt to free a stuck auxiliary contact that controls local indication. As a result of the CVI actuation, flow to lower containment radiation monitor (1-RM-90-106) was isolated, prompting control room operators to enter Condition B of LCO 3.4.15, RCS Leakage Detection Instrumentation. At 1634 EDT, control room operators exited the TS 3.4.15 condition when 1-RM-90-106 was returned to service.</br>On April 17, 2015 at 1327 EDT, control room operators exited LCO 3.3.6 Conditions A and B and LCO 3.6.3 Condition A when sample pump repairs were completed on 1-RM-90-131. </br>On April 19, 2015 at 1550 EDT, 1-RM-90-131 radiation readings spiked and initiated a CVI, prompting control room operators to enter TS LCO 3.4.15 Condition B and LCO 3.3.6 Condition A, until flow was restored to 1-RM-90-106 at 1636 EDT and 1-RM-90-131 was returned to service on April 26, 2015 at 1229 EDT. </br>Each CVI was documented in accordance with the corrective action program, and TVA completed an equipment apparent cause evaluation (CR 1015781) that revealed the cause of the two CVI actuations was the result of a faulted Start/Stop control unit. TVA replaced the faulted control unit.</br>In both instances, the CVI actuations resulted from invalid signals and were limited to a single piece of Train B equipment. There was no loss of safety function and there were no actual safety consequences during the events.</br>The NRC Resident Inspector has been informed. NRC Resident Inspector has been informed.
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