 INES 2 |
Radiographer Overexposure |
On November 19, 2005, the State of Oklahoma notified the Nuclear Regulatory Commission (NRC) that a radiographer received a calculated effective dose of 230 mSv (23 rem), and a hand dose of 1.7 Gy (173 rad), a dose in excess of the NRC’s annual occupational and extremity limit of 50 mSv (5 rem) and 0.5 Sv (50 rem) respectively.
According to the licensee, during the conduct of radiographic operations on 11/18/05, a radiographer approached the device containing a 2.4 TBq (66 curie) iridium-192 sealed source to change film with the source in its unshielded position and with his alarming ratemeter turned off. The radiographer’s assistant was supposed to retract the source to the shielded position, but failed to do so because he was responding to cellular phone text messages. The radiographer was in the vicinity of the unshielded source until the radioagrapher’s assistant advised him the source was not retracted. The licensee estimated that the radiographer was in the area of the unshielded source for approximately three minutes.
The licensee sent the personal dosimeters worn by the individuals for analysis on 11/21/05. The radiographer’s direct reading personal dosimeter was off-scale and the radiographer’s assistant’s personal dosimeter had a reading of 1.2 mSv (120 mrem).
The individuals’ blood was tested for white blood cell count and cytogenetic studies were conducted for the radiographer. Results of the cytogenetic analysis concluded that at a 95 percent confidence interval, the dose to the individual was 40 mSv (4 rem). The analysis is in agreement with the dosimeter analysis of approximately 41 mSv (4.1 rem) and the licensee has assigned the radiographer a dose of 69 mSv (6.9 rem) for calendar year 2005. The radiographer’s assistant’s dosimeter analysis concluded that he received a dose of 1.21 mSv (121 mrem).
The Final rating for this event is Level 2.
Event date: Fri, 18-11-2005
