ENS 51341
ENS Event | |
|---|---|
14:35 Aug 18, 2015 | |
| Title | Flexitron Source Lodged in Check Ruler |
| Event Description | On August 18, 2015, at 1035 EDT as a part of acceptance of a new Flexitron mHDR Unit, [Mt. Clemens Regional Medical Center d/b/a McLaren McComb] tested the source position accuracy using a position check ruler. Licensee programmed the source so that it would go to certain positions. The positions were initialized at 1034 EDT. The source was being watched with the room monitor camera and the camera was zoomed in on the position and not the entire ruler. The source was viewed moving out and passing the positions. The source was supposed to dwell two seconds in each position. After 10 seconds, the cable was seen retracting. At 1035 an error message was received from the machine. The camera was zoomed out and noticed the cable was stuck in the ruler and the source was lodged somewhere between the faceplate and the groove in the ruler. At this point the service engineer from Elekta was there and he looked at the situation and the door had been decided to be opened so the source could be retracted to resolve the situation. With the door open, the room monitor was showing radiation present so we closed the door. At this point, the service engineer engaged the emergency switch and tried to add additional force to the source to retract. This was unsuccessful. Contacted the Elekta Radiation Safety Officer (RSO) for advice. The Elekta RSO suggested to go into the room and retract the source manually. The service Engineer and the Director for Radiation Services then entered the room to secure the ruler with the source in it inside the lead pig sitting right next to the mHDR unit. The plan for securing the source and ruler was discussed and approved with the Elekta RSO.
The event was planned and timed. It took 11 seconds from opening the door to securing the source inside the pig. The source cable was secured to the pig. The pig was secured inside a cabinet and the room was secured to prevent unauthorized entry. The exposure around the container was 50 mR/hr at the surface and 18 mR/hr at one meter away. Lead bricks were placed around the cabinet to reduce the exposure and the dose was measured at <1mR/hr at the lead bricks where the door is located. The Device is an Elekta Nucletron Flexitron Serial Number: 00225 Source: Ir-192, 12.21 Ci on 7/30/2015 Serial Number: D363E-0477 Model Number: 136.147 This event was also reported by the device manufacturer, ELEKTA, at 0948 EDT on 08/19/2015 NRC License No. 10-35096-01- SEE EN 51330
The following additional information summary was excerpted from a detailed time line provided by licensee via email: McLaren Macomb was in the middle of a project to replace a microSelectron v2 HDR unit with a Flexitron unit. The installation was scheduled to be completed on Friday, August 14, 2015, with training and commissioning to begin immediately. However, the dedicated camera for source position verification was pending shipment and installation by the vendor. In light of this missing camera, a Source Position Ruler was borrowed from our sister facility at Karmanos Cancer Institute in Detroit, MI to check the source position accuracy with Gafchromic film as part of acceptance procedures. On August 18, 2015, the source position check ruler was connected to the Flexitron channel five using matching transfer tubes. The plan was created for the source to dwell at positions 360 (most proximal), 370, 380, 390, 395, and 400mm (most distal) within the ruler for two seconds each. In the absence of dedicated Elekta camera, the CCTV camera for in-room patient monitoring was used. The camera was zoomed on the part of the ruler where the source was expected to dwell. The plan was executed successfully with the source position check ruler two times. On the third attempt, the source got wedged inside the ruler and could not be retracted into the HDR safe. No patient was involved in this incidence and the event did not result in any unplanned exposure to any personnel. [During source retrieval] , the total time from entering the room until the source was secured inside the emergency container was 11.16 seconds, which would result in total exposure of 140 mRem to the whole body. The survey around the lead container showed an exposure rate of 8 mR/hr at the top, 48 mR/hr at the side and 18 mR/hr 3 feet away. The background radiation recorded by the meter was 0.002 mR/hr. The power to the unit was removed. The radiation survey meter recorded background radiation at the console area and patient access hall about 20 feet away from HDR door. The door to the HDR room was secured. The automatic door switch to the HDR room was disabled, and the door knob inside the room turned so that the keypad to unlock the door was deactivated. The electrical door opener was also disengaged from inside the room. As such, one could only enter the room using a dedicated key. There are only two copies of the key which are in the possession of the Authorized Medical Physicists[AMP]. A 'Do Not Enter' sign, along with the AMPs name and mobile phone number, was placed on the door. The emergency container was placed inside the HDR cabinet into the back corner and the cabinet locked. The survey meter showed an exposure rate of 5 mR/hr at the cabinet door. A wall was built around the emergency container using 8 inch x 5 inch x 2inch steel bricks. This reduced the exposure rate at the cabinet door to about 1 mR/hr. Notified R1DO(DeFrancisco), R3DO(Skokowski) and NMSS Events Notification (via email). |
| Where | |
|---|---|
| Mclaren Mccomb Mt. Clemens, Michigan (NRC Region 3) | |
| License number: | 21-04080-01 |
| Organization: | Mclaren Mccomb |
| Reporting | |
| 10 CFR 30.50(b)(2), Licensed Material Protection Equipment Failure | |
| Time - Person (Reporting Time:+22.93 h0.955 days <br />0.136 weeks <br />0.0314 months <br />) | |
| Opened: | Praveen Dalmia 13:31 Aug 19, 2015 |
| NRC Officer: | Jeff Herrera |
| Last Updated: | Aug 24, 2015 |
| 51341 - NRC Website | |
Mclaren Mccomb with 10 CFR 30.50(b)(2) | |
WEEKMONTHYEARENS 513412015-08-18T14:35:00018 August 2015 14:35:00
[Table view]10 CFR 30.50(b)(2) Flexitron Source Lodged in Check Ruler 2015-08-18T14:35:00 | |