POTENTIAL OVEREXPOSURE OF RADIOGRAPHER
The following was received from the Mississippi Division of Radiological Health via phone:
A radiographer was exposed to a 100 Curie Ir-192 source for 8 minutes while changing film during a radiography shot. The radiographer was not wearing dosimetry and did not have a hand held radiation meter. While changing film, the radiographer realized the source had not been retracted and left the area. This was not an equipment malfunction, and the source was retracted when it was realized that the radiographer had been exposed. The radiographer reported the event to the Mistras Radiation Safety Officer (RSO). Estimated dose is 20 Rem to the hands and 19.6 to 19.7 Rem whole body. The radiographer was sent to a local hospital for bloodwork.
* * * UPDATE FROM ROBERT SIMS TO HOWIE CROUCH VIA EMAIL AT 1706 EST ON 11/8/19 * * *
"[A state of Mississippi Health Physicist investigator] interviewed the RSO on 11/7/2019 and investigated the incident. After reviewing and questioning the incident details, [the investigator] found the following evidence that may determine this may not have been an overexposure. The assistant radiographer retracted the source, but did not perform the bump test to fully retract the source into the locked position. This caused the assistant radiographer to believe the source was still in the collimator. When returning to change the film, he saw the red button on the camera instead of green which would indicate the source was in the locked position. The assistant was not using dosimetry, rate alarm or survey instrumentation. He appears to have panicked, came down the ladder, and couldn't get the crank to move in. The lead radiographer then grabbed the crank and cranked out and back in immediately to fully retract the source into the camera. [The investigator] reviewed compliant leak tests of camera and wipes along with maintenance and service reports before and after the incident and the RSO could not replicate any problems that would prevent them from retracting the source. There was no malfunction with the camera or the cranks. It appears that the source was in the end of the camera but not in the fully shielded position, which could allow some radiation out of the tube that the source enters. However, we do not know how much because the assistant was not wearing any dosimetry. The other assistant's dosimetry [assistant radiographer 2] only picked up 1 milliRem of dose but he was approximately 25 ft. away with steel shielding from the tank they were working on in between him and the source. [The investigator is] waiting on the emergency reading of the doses recorded on the OSL badges used by the crew and follow up doctor's visit. [The investigator] interviewed [the assistant radiographer on] 11/8/2019 at 1549 CST. [The assistant radiographer] reports that he had more blood drawn today and will provide results next week. He said he feels great and has had no sickness such as nausea, pain or redness and swelling in the hands. Will update again next week after receiving lab results."
* * * UPDATE FROM ROBERT SIMS TO THOMAS KENDZIA VIA EMAIL AT 1409 EST ON 11/19/19 * * *
"[A state of Mississippi Health Physicist investigator] interviewed the assistant radiographer [who was not wearing dosimetry] on 11/12/2019. [The assistant radiographer] reported that lab was drawn on 11/3/2019 and 11/8/2019. Both labs results returned within normal limits and [the assistant radiographer] has no physical symptoms of radiation sickness. [The assistant radiographer] remains at regular work duties recommended in his physician reports that he provided to [the investigator]. [The RSO] was interviewed on 11/11/2019 and provided the Landauer dosimetry report for the three RT crew members. The crew received new dosimeters on 11/1/2019 and they were sent for an emergency read the day after the incident.
"[The] lead radiographer received 109 milliRem, [assistant radiographer 2 who was wearing dosimetry] received 269 milliRem and [the assistant radiographer] received 150 milliRem although he was not wearing his dosimeter during this incident. [The assistant radiographer] is also on UT and other duties until the end of the year until his new annual dose limit year starts January 1, 2020. This is upon the recommendation of [the investigator] because although it has been determined that [the assistant radiographer] did not receive an over exposure equaling or exceeding the 15 to 25 RAD to cause radiation sickness, it does not rule out if he did or did not exceed his 5 rem TEDE. The licensee's personnel believe that the source was in the end of the camera, but not in the fully locked position because the red button was showing on the QSA 880 camera when [the assistant radiographer] returned from changing the digital film plate. Due to his elevation up on the tank and the tank shielding we cannot use any of the other crew members dosimetry to make any determinations. However based on the medical reports and physical evidence it appears that [the assistant radiographer] has no physical symptoms from radiation sickness. [The assistant radiographer] will have his last lab test on 11/22/2019, if it is normal, [the assistant radiographer] states that the physician intends to release him completely from all medical care related to this incident."
Notified the R4DO (O'Keefe) and NMSS Events Notification via email.
* * * UPDATE AT 1333 ON 12/5/2019 FROM ROBERT SIMS TO JEFF HERRERA * * *
"As the investigation continued [a state of Mississippi Health Investigator] reviewed additional information received throughout the day on 11/18/2019, but sufficient time did not exist to thoroughly review the latest findings to include them on the 11/19/2019 update.
The current additional findings are as follows: [the state of Mississippi Health Physicist Investigator] Re interviewed all personnel again, and requested all lab results and Physician findings from [the assistant radiographer].
"[The assistant radiographer] willingly provided all CBC and cytogenetic lab test results that were taken on 11/3/2019, 11/8/2019, and 11/22/2019. [The assistant radiographer] stated that the physician reported the lab results to be within normal limits and the physician released [the assistant radiographer] from medical care on 11/22/2019 that had resulted from this incident.
"[The state of Mississippi Health Physicist Investigator] also found during the second interview of personnel that the films that were with [the assistant radiographer] and located on the pipe during the 8 minutes that it took [the assistant radiographer] to change out the film were processed later and were acceptable images. [The state of Mississippi Health Physicist Investigator] attached the images in the file as evidence to support that [the assistant radiographer] was not overexposed. If the films had been exposed with an open source out for 8 minutes they would be blacked out from overexposure. The original exposure time to produce the radiograph with the film combination, distance and thickness of steel for this job was 1 minute. Even with digital radiography, an image receptor plate can be overexposed beyond acceptable exposure limits, and cannot be window leveled to make it an acceptable image, but this was not the case. The radiographer and RSO reported that an attempt to crank out and retract the source was made by each assistant and the radiographer when trying to retract the source after [the assistant radiographer] returned down the ladder. This would explain why the images produced were acceptable radiographs. There had been enough exposure to properly expose the film but not overexpose it. This appears to support the possibility that the source was not out the entire 8 minutes while [the assistant radiographer] was changing the film and moving the source tube on the jig. At this point [the assistant radiographer] was also down the ladder 25 feet away with the other radiographers who were wearing the required dosimetry behind the shielding of the tank. Three (3) violations were issued and corrective actions have been submitted to the Mississippi Division of Radiological Health All records are included in the 2019 Incident file at the Mississippi State Department of Health Division of Radiological Health. [The state of Mississippi Health Physicist Investigator] considers this investigation and incident closed. If you require any further information, documentation or have questions, please contact [The state of Mississippi Health Physicist Investigator].
"Mississippi Incident No.: MS-190005, NMED #190535"
Notified the R4DO (Taylor) and NMSS (via email).
* * * RETRACTION ON 12/6/19 AT 1452 FROM ROBERT SIMS TO CATY NOLAN * * *
"A review of the incident details represented a 'substantial potential for an exposure in excess of 10 CFR 20.' However, there was not enough evidence to definitively prove there was an overexposure due to the details listed throughout this investigation. These included the assistant who was allegedly overexposed. This individual never experienced any signs of radiation sickness or erythema or redness to the hands throughout the investigation period to its close date on 12/3/2019. None of the other crew members' dosimeter readings exceeded occupational dose limits. On 12/2/2019, Mistras also requested anonymity for the individuals involved in this incident.
"All documentation concerning this incident investigation is stored in Mississippi State Department of Radiological Health 2019 Incident File, under incident Report No. MS-190005."
NMED #190535
Notified the R4DO (Taylor) and NMSS (via email). |