The Nuclear Regulatory Commission has sent to Congress its annual report on abnormal occurrences involving the medical and industrial uses of radioactive material. An abnormal occurrence is defined by law as an unscheduled incident or event that the NRC determines to be significant from the standpoint of public health or safety. The NRC sets specific criteria, most recently updated in October 2017, for determining which events qualify.
The NRC identified nine abnormal occurrences in fiscal year 2020, eight of which were medical events, such as the misadministration of radioactive material in the diagnosis or treatment of an illness. According to the NRC, the number of occurrences represents a very small portion of the thousands of nuclear medicine and radiation therapy procedures involving radioactive material performed annually in the United States.
The ninth event involved an unintended radiation exposure to an embryo or fetus during a medical procedure. No events occurred at commercial nuclear power plants in FY 2020 that met the criteria for an abnormal occurrence declaration.
Other events: The NRC report (NUREG-0090, Volume 43) also describes four events that did not meet the criteria to be declared abnormal occurrences but received enough attention from the NRC, state regulators, or the public to be deemed of interest. Three of these were industrial events that resulted in worker exposures. The fourth was a severe storm that caused a loss of off-site power at the Duane Arnold nuclear power plant in Iowa in August 2020, leading the plant to permanently shut down earlier than previously scheduled.