No. I-09-046 

Contact: Diane Screnci, 610/337-5330 

 Neil Sheehan, 610/337-5331 

November 23, 2009

E-mail: opa1@nrc.gov

NRC MONITORING COMPANY’S RESPONSE 

 TO THREE MILE ISLAND 1 NUCLEAR PLANT CONTAMINATION EVENT 

 The Nuclear Regulatory Commission is continuing to monitor Exelon’s actions in 

response to a radiation contamination incident at the Three Mile Island 1 nuclear power plant on 

Saturday. The event involved minor contamination of about 20 workers during activities inside 

the plant’s containment building. The levels of contamination were low and do not pose a health 

or safety concern. No radioactivity left the site as a result of the event and there was no threat to 

public health and safety. 

NRC Resident Inspectors assigned on a full-time basis to the Middletown, Pa., plant went 

to the site on Saturday and Sunday to review Exelon’s response to the event, as did two radiation 

safety specialists from the agency’s Region I Office. With the assistance of these specialists, the 

Resident Inspectors are continuing to independently evaluate the company’s efforts to identify 

the source of the contamination, the adequacy of controls in place to prevent a recurrence and the 

development of a root cause evaluation of what occurred. 

 “Although the event was relatively minor in terms of public health and safety, our 

expectation is that Exelon will get to the bottom of the event in a timely and thorough manner,” 

NRC Region I Administrator Samuel J. Collins said. “We will be working to better understand 

the source of the contamination and whether adequate controls were in place at the time of the 

event.” 

Three Mile Island 1 is currently shut down for a refueling and maintenance outage, part 

of which includes the replacement of components known as steam generators. At about 4 p.m. on 

Saturday, radiation monitors alarmed briefly inside the Three Mile Island 1 containment 

building, which is the large concrete structure surrounding the plant’s reactor. Per safety 

procedures, the approximately 150 workers inside the building at the time were instructed to exit. 

They were then scanned for any radioactive contamination. While contamination can occur 

during nuclear plant outages and maintenance activities, operators are expected to take 

precautions to minimize exposures. 

NRC NEWS

U.S. NUCLEAR REGULATORY COMMISSION

Office of Public Affairs, Region I 

475 Allendale Road, King of Prussia, Pa. 19406 

Site: http://www.nrc.gov
According to Exelon, all of the workers were checked and initially less than 20 were determined 

to have low levels of skin contamination. Further testing, including an evaluation of internal 

uptake of radiation, has since reduced the total number of contaminated. The maximum dose to 

any worker from the contamination was 40 millirems. None of the contamination levels is 

considered significant. 

To put the levels in perspective, the average American receives about 300 millirems of 

radiation exposure each year from natural sources. The annual federal limit for nuclear plant 

worker exposure is 5,000 millirems. Another measure is the amount of radiation in our bodies 

from the food and water we ingest. That is estimated at 40 millirems per year. 

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