Unit one is really old...
So Pilgrim and Nine Mile Point has had recent troubles with shutting MSIVs and scrams. A new component failed.
Then one electromatic failed to close. It is always really bad news when two different components failed at the same time. It indicates a global problem with maintenance and budgets.
Was the electrometric relieve valve leaking...
9/9: Update: Nine Mile 1 nuclear reactor returns to service after 4-day outage
SCRIBA, N.Y. -- Operators returned Nine Mile Point Unit 1 to full power Tuesday after repairing a steam valve that closed unexpectedly during routine testing on Friday, owner Exelon Corp. announced today.
The automatic shutdown Friday occurred during quarterly testing of the main steam isolation valve, according to the U.S. Nuclear Regulatory Commission. The valve would be used in the event of an accident to halt the flow of steam from the reactor to the turbine building, helping to keep radioactivity bottled up in the the containment building that surrounds the reactor.
The valve was supposed to reduce flow to 10 percent and then reopen. Instead, it fully closed, the NRC reported. A shuttle valve within the equipment stuck. The shuttle valve had been replaced five months ago during the plant's refueling and maintenance outage, and is being returned to the vendor for evaluation, the NRC reported.
During the shutdown, one of the plant's six electromatic relief valves did not fully close as it should, NRC officials said. Those valves would be used to depressurize the reactor during a pipe break to allow coolant to be injected into the reactor core.
The NRC's two on-site inspectors reported no problems with operator performance during the shutdown, but they are working with Exelon to resolve the equipment issues that surfaced during the event, NRC officials said.
Nine Mile Point Nuclear Station is located seven miles northeast of Oswego and 50 miles north of Syracuse. The station's two units can produce roughly 1,937 megawatts, enough to power nearly 2 million homes.
UNPLANNED AUTOMATIC SCRAM AND SPECIFIED SYSTEM ACTUATIONS DUE TO MSIV CLOSURE
"On September 4, 2015, at 0916 [EDT], Nine Mile Point Unit 1 experienced an automatic reactor scram following Main Steam Isolation Valve [MSIV] closure and isolation of both main steam lines. The cause of the MSIV closure is not known at this time. All control rods fully inserted. Following the scram, pressure was momentarily controlled through the use of the Emergency Condenser system. At 0950, pressure control was established through the main steam lines to the condenser through Main Steam Isolation Valves (MSIVs) 01-02 and 01-04. MSIV 01-03 would not reopen. All other plant systems responded per design following the scram. The reactor scram is a 4-hour report per 10 CFR 50.72(b)(2)(iv)(B)."
"The following systems automatically actuated after the scram as expected. These system actuations are an 8-hour report per 10 CFR 50.72(b)(3)(iv)(A).
"1. The High Pressure Coolant Injection (HPCI) system. HPCI initiated at 0916 and reset at 0917 when RPV level was restored above the HPCI system low level actuation set point. HPCI initiated and was reset a second time at 0922. HPCI is a flow control mode of the normal feedwater systems, and is not an Emergency Core Cooling System.
"2. The Core Spray system actuated, but did not discharge to the Reactor Coolant system. The Core Spray system was secured at 1033.
"3. The Emergency Condenser (EC) system actuated to control pressure. EC-11 was secured at 0917. EC-12 was secured at 0921 . The maximum shell temperature of EC system was 193 degrees Fahrenheit.
"4. Containment Isolation actuation.
"Nine Mile Point Unit 1 is currently in Hot Shutdown, with reactor water level and pressure maintained within normal bands. Since the scram, there have been no anomalies observed with feedwater system operation. Decay heat is being removed via steam to the main condenser using the turbine bypass valves. The offsite grid is stable with no grid restrictions or warnings in effect."
The Reactor is being supplied by the normal feedwater system and there was indication of a partial lift/reset on one Electrometric Relief Valve (ERV).
The licensee notified the NRC Resident Inspector and the State of New York Public Service Commission.
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