ENS 47148
ENS Event | |
|---|---|
12:00 Jan 20, 2009 | |
| Title | Agreement State Report - Stuck Source |
| Event Description | The following report was received via fax:
The field service engineer was conducting the quarterly source exchange at the facility. While unloading the source into the transport container, the engineer received an error code indicating there were issues with the source side drive mechanism. The problem with the drive mechanism prohibited the source from fully deploying into the transport container or retracting back into the safe. The emergency motor was not able to retract the source. Following emergency procedures, the engineer tried to manually retract the source, however, the cable drum was locked-up and would not wind the source cable, He removed the unload transfer tube from the indexer, cut the exposed source cable and manually inserted the source in to the emergency container. The engineer disassembled the drive mechanism and collected the damaged parts. The unit was then cleaned and the cable drum and gear wheel were replaced. The system was tested repeatedly and found to be functioning properly. Initial calculations of 241 mR whole body dose were 'worst case scenario'. The dosimeter badge report indicated a whole body dose of 40 mR which does not exceed the regulatory limit for occupational exposure. The Root Cause Investigation was completed on 06-15-2009 by Nucletron B.V. in the Netherlands. For the investigation and analysis of the incident, the collected damaged parts were sent to Nucletron B.V. in the Netherlands where they were photographed and inspected. Additionally, the engineer was asked for his findings and the system logbook was scrutinized. According to the damage on the source cable drum, the drum had made at least 2.2 rotations before it got stuck (293 mm to move out of the indexer; 242 mm from where the source cable was cut off; source cable drum diameter is 80 mm). After examining the damaged parts, there was no visible cause as to why the drum became damaged. An obstruction at this position during the source exchange into the transport container is not expected since at this point it is a single straight tube; however, this cannot be ruled out as a possibility. The message logbook of the system was investigated and showed that during the source exchange, the engineer received seven error code 3's at 176 mm all within a six minute time frame. Error code 3 is a source obstruction which can happen when the bushing between the rigid and flexible part of the source cable cannot pass through the indexer clamp of the unload tube due to a misalignment of the clamping mechanism or damage to the source cable. The transfer tube was removed and a normal 'treatment' was performed without problem. The transfer tube was then reattached to exchange the source and four more error code 3's were received within two minutes at the same distance, thus indicating it was purely a container problem. There were no errors in the logbook that indicated the source remained outside the system. After the multiple tries with the error code 3, the system was switched off. Upon restart an hour later, two more attempts were made. However, the engineer now received error code 2 indicating the source would no longer come out of the safe. The system was turned back off again. Upon restart thirty minutes later, the unit had a dummy source in it; the source had apparently been unloaded by hand and replaced with a dummy. Later, the source exchange procedure was performed and a dummy source loaded properly; after which, the system worked normally again. According to the engineer, the system did not show any error or radiation/out-of-safe message when it was switched off following the problem with the container. When he entered the treatment room, he unexpectedly found the source to be outside the system, at which point he followed the emergency procedures in order to secure the source. Once the source was secure, the engineer forcibly pulled the remaining cable from the cable drum. He then proceeded to clean the system and assess the damaged parts. There is no logical explanation as to how the source got stuck outside the system. The logbook does not have any indication to this fact. The damage to the drum and cable may have occurred during the emergency procedure that was carried out to secure the source. Since operator error by the service engineer cannot be ruled out, a retraining on source exchange and handling is required. In addition, the transport container has been returned to Nucletron B.V. in the Netherlands for further investigation. The source exchange was being conducted on a MicroSelectron HDR-V2, S/N 31526, TCS software version 1.50C, located at the Grant/Riverside Methodist Hospital in Columbus Ohio. The field problem report number is FPR 252753. |
| Where | |
|---|---|
| Nucletron Corporation Columbia, Maryland (NRC Region 1) | |
| Organization: | Maryland Dept Of The Environment |
| Reporting | |
| Agreement State | |
| Time - Person (Reporting Time:+22418.45 h934.102 days <br />133.443 weeks <br />30.709 months <br />) | |
| Opened: | Ray Manley 13:27 Aug 12, 2011 |
| NRC Officer: | Joe O'Hara |
| Last Updated: | Aug 12, 2011 |
| 47148 - NRC Website | |
Nucletron Corporation with Agreement State | |
WEEKMONTHYEARENS 471482009-01-20T12:00:00020 January 2009 12:00:00
[Table view]Agreement State Agreement State Report - Stuck Source 2009-01-20T12:00:00 | |