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At 0331 CDT on 6/9/10, the Unit 2 reactor … At 0331 CDT on 6/9/10, the Unit 2 reactor automatically scrammed due to closure of the Main Steam Isolation Valves (MSIVs). Operating Instruction 2-OI-99 section 8.1, Reactor Protection System (RPS) Bus B Transfer from Motor Generator to Alternate, was in progress for planned maintenance. The MSIVs closed during the RPS power transfer. The cause of the closure of the MSIVs is under investigation.</br>All systems responded as expected to the reactor scram. Safety Relief Valves (SRVs) opened automatically as designed to limit the pressure transient. No Emergency Core Cooling System (ECCS) or Reactor Core Isolation Cooling system (RCIC) reactor water level initiation set points were reached and all expected containment isolation and initiation signals were received. Reactor pressure control was established by manually operating one SRV then maintained using the Main Steam Line Drain Valves. RCIC and the High Pressure Coolant Injection system (HPCI) were manually initiated to control reactor water level. The scram was reset, MSIVs were opened, and the Main Condenser was established as a heat sink. Reactor water level control was established with the Reactor Feedwater System and RCIC and HPCI were returned to standby readiness.</br>At 0408 CDT on 6/9/10, a full scram signal was received when 2F Intermediate Range Monitor (IRM) spiked momentarily followed by a spike on 2C IRM. The reactor was stable and operating in Mode 3, Hot Shutdown. No ECCS or RCIC initiation set points were reached. No additional containment isolation signals or initiation set points were received. The cause of the 2C and 2F IRM spikes is under investigation.</br>The scram event from critical is reportable within 4 hours per 10CFR 50.72(b)(2)(iv)(B), 'any event or condition that results in actuation of the reactor protection system (RPS) when the reactor is critical except when the actuation results from and is part of a pre-planned sequence during testing or reactor operation.' It is also reportable within 8 hours per 10CFR 50.72(b)(3)(iv)(A) and requires an LER within 60 days per 10CFR 50.73(a)(2)(iv)(A). The scram received at 0408 CST is reportable within 8 hours 10CFR 50.72(b)(3)(iv)(A), 'any event or condition that results in valid actuation of any of the systems listed in paragraph (b)(3)(iv)(B), except when the actuation results from and is part of a pre-planned sequence during testing or reactor operation,' and requires an LER within 60 days per 10CFR 50.73(a)(2)(iv)(A). </br>The NRC Resident Inspector was notified.</br>All rods fully inserted as a result of the first reactor scram. The plant is currently in a normal, post-trip electrical line-up. All SRVs did reseat. There was no impact to the other two units.</br> * * * UPDATE FROM BILL BAKER TO PETE SNYDER ON 6/10/10 AT 1749 EDT * * * </br>Additional review of available data and inspection results revealed that Safety Relief Valves (SRVs) did not lift automatically during the scram. The only operations of SRVs were performed manually to control reactor pressure until the Main Steam Isolation Valves (MSIVs) were reopened. All other details described in the original event notification remain as stated.</br>The licensee notified the NRC Resident Inspector.</br>Notified R2DO (Nease).Resident Inspector.
Notified R2DO (Nease).
08:31:00, 9 June 2010 +
45,990 +
07:58:00, 9 June 2010 +
08:31:00, 9 June 2010 +
At 0331 CDT on 6/9/10, the Unit 2 reactor … At 0331 CDT on 6/9/10, the Unit 2 reactor automatically scrammed due to closure of the Main Steam Isolation Valves (MSIVs). Operating Instruction 2-OI-99 section 8.1, Reactor Protection System (RPS) Bus B Transfer from Motor Generator to Alternate, was in progress for planned maintenance. The MSIVs closed during the RPS power transfer. The cause of the closure of the MSIVs is under investigation.</br>All systems responded as expected to the reactor scram. Safety Relief Valves (SRVs) opened automatically as designed to limit the pressure transient. No Emergency Core Cooling System (ECCS) or Reactor Core Isolation Cooling system (RCIC) reactor water level initiation set points were reached and all expected containment isolation and initiation signals were received. Reactor pressure control was established by manually operating one SRV then maintained using the Main Steam Line Drain Valves. RCIC and the High Pressure Coolant Injection system (HPCI) were manually initiated to control reactor water level. The scram was reset, MSIVs were opened, and the Main Condenser was established as a heat sink. Reactor water level control was established with the Reactor Feedwater System and RCIC and HPCI were returned to standby readiness.</br>At 0408 CDT on 6/9/10, a full scram signal was received when 2F Intermediate Range Monitor (IRM) spiked momentarily followed by a spike on 2C IRM. The reactor was stable and operating in Mode 3, Hot Shutdown. No ECCS or RCIC initiation set points were reached. No additional containment isolation signals or initiation set points were received. The cause of the 2C and 2F IRM spikes is under investigation.</br>The scram event from critical is reportable within 4 hours per 10CFR 50.72(b)(2)(iv)(B), 'any event or condition that results in actuation of the reactor protection system (RPS) when the reactor is critical except when the actuation results from and is part of a pre-planned sequence during testing or reactor operation.' It is also reportable within 8 hours per 10CFR 50.72(b)(3)(iv)(A) and requires an LER within 60 days per 10CFR 50.73(a)(2)(iv)(A). The scram received at 0408 CST is reportable within 8 hours 10CFR 50.72(b)(3)(iv)(A), 'any event or condition that results in valid actuation of any of the systems listed in paragraph (b)(3)(iv)(B), except when the actuation results from and is part of a pre-planned sequence during testing or reactor operation,' and requires an LER within 60 days per 10CFR 50.73(a)(2)(iv)(A). </br>The NRC Resident Inspector was notified.</br>All rods fully inserted as a result of the first reactor scram. The plant is currently in a normal, post-trip electrical line-up. All SRVs did reseat. There was no impact to the other two units.</br> * * * UPDATE FROM BILL BAKER TO PETE SNYDER ON 6/10/10 AT 1749 EDT * * * </br>Additional review of available data and inspection results revealed that Safety Relief Valves (SRVs) did not lift automatically during the scram. The only operations of SRVs were performed manually to control reactor pressure until the Main Steam Isolation Valves (MSIVs) were reopened. All other details described in the original event notification remain as stated.</br>The licensee notified the NRC Resident Inspector.</br>Notified R2DO (Nease).Resident Inspector.
Notified R2DO (Nease).
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