Siren Problems at Three Mile Island


  • From October 5-9, 2001, “Licensee sirens in Lancaster County were inoperable October 5 through October 9, 2001, due to a radio transmitter being deenergized at the county facility. The transmitter is part of the siren actuation system. This issue is unresolved pending further investigation into the lines of ownership and maintenance of the actuation system.” (IR 50-289/01-07).
  • On January 11, 2002 , Siren testing at TMI encountered numerous problems: all sirens failed in York County and one siren failed in Lancaster County. AmerGen attributed to computer malfunctions.
  • On March 3, 2002, a siren malfunctioned in York County again. During TMI’s annual test on on January 30, 2002, all 34 sirens in York County, located within ten-miles of the plant, failed to activate.
  • On June 25, 2002, “...station emergency preparedness personnel discovered that the emergency planning siren base station at the site, was unable to communicate with the off site sirens, due to external radio frequency noise in the area.” (IR-50-277/02-05; 50-278/02- 05)
  • On December 12, 2002, TMI sirens malfunctioned in Cumberland and York counties. In Dauphin County, 28 sirens malfunctioned due to the “inadvertent” discharge of the “space bar” by a computer operator (Refer to June 22, August 15 and October 5-9, 2001 and January 11, March 3 2002, for related problems.)
  • On July 28, 2010, the NRC issued a report of an inspection at the Three Mile Island plant for the quarterly period ending June 30.
    The NRC said it found no findings of significance. However, it noted that the TMI plant operator identified a violation that was determined to be of very low safety significance. The NRC said it would treat the violation as a non-cited violation.
    The issued stemmed from the TMI Emergency Plan and the plant paging system. The report said that plant operator Exelon began testing its on-site speakers in March 2010. A total of 301 out of 405 speakers were tested, and of those tested, 108 had identified deficiencies, the report said. “Contrary to the TMI Emergency Plan, the 108 speakers would not provide immediate warning and instruction to on-site personnel during an emergency,” the report said. “Upon discovery, Exelon issued a standing order to issue blow horns to operations and security staff to notify people in areas that would need to be evacuated during an emergency.“ The report added, “The finding is of very low safety significance because prompt compensatory measures were taken upon discovery.”
  • June 23, 2011, Three Mile Island's emergency sirens sounded at 12:15 p.m. Thursday as part of an annual test -- but it didn't work everywhere. The 96 sirens, which cover five counties and are within a 10- mile radius of TMI, were set to sound for three minutes. They sounded everywhere except in Lancaster County.
    Officials ran another test, this time just in Lancaster County, at 1:15 p.m. At that time, the sirens did work in Lancaster County. (WGAL)
    A Lancaster County EMA official said Lancaster County and another county pressed the siren test button simultaneously and the system did not register the Lancaster County test.
  • July 14, 2011, A Three Mile Island warning siren sounded accidentally on Thursday afternoon, according to Dauphin County officials.
    The TMI siren at 2nd and Hanover streets in Hummelstown inadvertently sounded at 1:19 p.m. It lasted for fewer than 30 seconds, according to Stephen Libhart, Director of the Dauphin County EMA.
    Libhart says Exelon will repair or replace any components of the siren if necessary. (WGAL)