NRC Monitoring Company’s Response To Three Mile Island Nuclear Plant Contamination

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

 - By Stephen Heiser -

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.

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 amount of contamination for any worker 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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