Emergency declared at U.S. nuclear plant after lightning strike — “Venting of Unit 1 primary containment” — ‘Normal’ radiation levels reported — NRC mobilizes response center

LaSalle News Tribune:  Exelon Generation’s La Salle County Generating Station declared an Unusual Event at 3:11 p.m. today, after both units automatically shut down when power from the switchyard into the site was interrupted during a severe thunderstorm. [...] Technical experts are working to restore power to the switchyard. [...] LaSalle Generating Station is located about 75 miles southwest of Chicago [...]

Morris Daily Herald: The U.S. Nuclear Regulatory Commission Region III staff is monitoring the La Salle nuclear power plant after a lightning strike knocked out offsite power to both Units 1 and 2. The NRC has mobilized its Incident Response Center in Region III, located in Lisle, Ill., and is monitoring the events along with the resident inspector onsite. [...] An Unusual Event is the lowest levels of the NRC’s four level emergency classification system. [...]

NRC: Event Notification Report for April 18, 2013: “In addition to information [previously provided], LaSalle Unit 2 received a high drywell pressure signal [1.77 psig] due to loss of containment cooling from the loss of power. [...] There is no evidence of reactor coolant leakage. There was no additional ECCS systems discharging into the RCS [Reactor Coolant System]. [...] two Unit 2 primary containment vent and purge valves were opened to vent the Unit 2 containment. Once Unit Two containment pressure reached 1.77 [psig], these two vent valves isolated as expected. “Due to the loss of offsite power, the Station Vent Stack Wide Range Gas Monitor (WRGM) and the Standby Gas Treatment Wide Range Gas Monitor (VGWRGM) also lost power. Manual sampling has been implemented and power is restored to the VGWRGM, however the VGWRGM has not been declared operable yet. Normal radiation levels have been reported from the manual sampling. [...]

UPDATE AT 0057 EDT ON 04/18/13: “After the Unit 2 primary containment vent and purge system isolated on the Unit 2 containment High Pressure signal, Venting of the Unit 1 primary containment was commenced. At 2005 CDT, Unit 1 primary containment pressure reached the Group 2 primary containment isolation system setpoint (1.77 PSIG) causing the primary containment vent and purge valves being used to vent the Unit 1 containment to isolate. Unit 1 primary containment venting was being performed through the Standby Gas Treatment system which is a filtered system. [...]

From: enenews.com

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