The US Nuclear Regulatory Commission (NRC) recently issued its Report to Congress on Abnormal Occurrences for fiscal year 2020. The report documents key aspects of those events that the NRC considers “Abnormal Occurrences” (AOs) and allows the regulated community to review the operating experience of reactor, medical, and industrial users of radioactive materials. AOs are unscheduled events that the NRC determines to be significant from the standpoint of public health or safety. Examples of such events appear below:

1. Human exposures to radiation from licensed radioactive material
2. The discharge or dispersal of radioactive material from its intended place of confinement
3. Medical events involving the use of radioactive materials in patients or research subjects
4. The theft, diversion, or loss of licensed material
5. The malfunction of a facility, structure, or equipment
6. An operating reactor plant that has overall unacceptable performance
7. A major deficiency in design, construction, control, or operation having significant safety implications that require immediate remedial action
8. An accidental criticality

In total, the NRC identified nine AOs in fiscal year 2020, eight of which were medical events involving the misadministration of radioactive material in the diagnosis or treatment of an illness, and one of which involved an unintended radiation exposure to an embryo or fetus during a medical procedure. None involved a commercial nuclear power plant. Summaries of the AOs as described by the NRC in its report appear below.

ABNORMAL OCCURRENCES

1. An embryo/fetus received an unintended radiation dose when a patient not known to be pregnant received the first of four doses of lutetium-177 (Lu-177) Dotatate for treatment of a neuro-endocrine tumor. The cause of the event was determined to be a weakness in the pregnancy policy to address limitations and contraceptive measures between collecting the pregnancy test and therapy dosage administration.
2. A patient received a dose that was at least 10 Gy (1,000 rad) more than expected to the wrong treatment site while undergoing an eye plaque radiotherapy procedure. The licensee believes the event occurred due to the lack of a second intact suture, which might have prevented the eye plaque from becoming dislodged and shifting to an incorrect treatment site.
3. A high dose rate (HDR) remote afterloader brachytherapy Tandem and Ovoid applicator dislodged from patient during treatment. The exact cause of the event is unknown; however, the licensee believes that the patient may have changed positions during treatment, causing the applicator to slip out of position.
4. I-125 brachytherapy seeds were inadvertently implanted into a patient’s bladder instead of the prostate during a prostate brachytherapy procedure. The licensee identified several aspects of its procedure that might have contributed to the event.
5. The stereotactic frame holding a patient in proper treatment position disengaged during a procedure. As a result of the mispositioning of the patient, the patient received an excess dose to a region of the left temporal lobe of the brain. The cause of the event is believed to be improper positioning of the patient.
6. A patient received a dose that was at least 10 Gy (1,000 rad) more than expected and administered to the wrong treatment site during an ovarian cancer treatment involving an HDR remote afterloader. The cause of the event is believed to be the entry of the incorrect catheter length into the HDR remote afterloader treatment delivery system.
7. A patient received a dose that was greater than 1 Gy (100 rad) to the lens of the eye while undergoing an eye plaque radiotherapy procedure. While receiving that treatment, the patient experienced a life-threatening medical event which caused medical staff to be unable to remove the plaque in accordance with the treatment plan.
8. A patient undergoing treatment for liver cancer with yttrium Y-90 microspheres received a dose that was at least 10 Gy (1,000 rad) more than expected to the wrong treatment site. The cause was likely placement of the tip of the intra-arterial catheter into the wrong branch of the hepatic arterial system.
9. A patient undergoing liver cancer treatment using split dose Y-90 microspheres received a dose that was at least 10 Gy (1,000 rad) more than expected to the wrong treatment site. The cause could not be determined.

OTHER EVENTS OF INTEREST

The report also identified “Other Events of Interest,” which did not constitute AOs, but received significant attention from the NRC. Three of these events were industrial events that resulted in worker exposures (e.g., a gauge failure, a stuck source, and improper cutting into a welded container containing radioactive material). The fourth was the severe storm that caused a loss of offsite power at an operating nuclear power plant.

The fact that all of fiscal year 2020’s AOs involved medical licensees is notable and coincides with other trends involving nuclear materials licensees. For example, as we previously reported, the number of allegations involving materials licensees in 2020 increased by 73%, while the number of NRC investigations involving materials licensees increased by 56% .

We will continue to follow issues and trends involving medical and industrial radioactive material licensees.