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Part 21 Report - 1996-111

ACCESSION #: 9512290054 SENTINEL Amersham Corporation 40 North Avenue Burlington, MA 01803 tel (617) 272-2000 tel (800) 225-1383 fax (617) 273-2216 21 December 1995 Document Control Desk Amersham U. S. Nuclear Regulatory Commission QSA Washington, D. C. 20555 Dear Sir or Madam: Amersham is reporting a Part 21 defect in accordance with 10CFR21.21 "This report concerns the model 660B radiographic exposure device. We have determined that in a lot of rear plates (quantity 16) that were assembled for installation onto the 660B, that the four screws holding the positive locking assembly on to the rear plate were not torqued to the required specification upon initial manufacture in July 1994. This caused a customer to notice that the locking assembly had become loose after approximately a year of service. Upon investigation it was determined that the screws had backed out approximately 0.25 inch allowing the locking assembly to become loose. This condition occurred on two of the rear plates from the lot of sixteen, we have not heard of any problems from the users of the other devices in the lot. In this condition the source can still be returned to the stored position and the device secured. However if a user did not notice that the locking assembly was loose, they may continue to use the device, allowing the screws to further loosen. If the screws were backed off approximately 0.75 inch, this could result in the locking assembly backing-off from the rear plate and potentially pulling the source past the fully shielded position. In the worst case scenario the locking assembly could fall off the back of the device, which would allow the source to be pulled out the back of the camera. Both of these situations are extremely unlikely, as users are required to perform a daily maintenance on the device to assure all fittings are tight and that the camera is operating properly. In addition to the daily check, users are required to perform a service every three months to verify safe operation of the device. Users are also required to perform a full maintenance on the device at least annually. This annual service requires that the rear plate be taken off and the entire locking assembly disassembled and inspected. The performance of any of these required checks would easily detect the possibility of loose screws and could be corrected immediately. Although we are confident that these checks would detect the possibility of a problem well before any chance of a decrease in safety of the device occurred, we are concerned that if these checks are not performed or if the user ignores the information and continues to use the device there could be a potential safety hazard. At this point, although we believe the problem is isolated to only one lot of rear plates, we are planning to send out an information notice to users advising them to pay particular attention to locking assembly and assure it is still secure. It will also reemphasize the requirement to perform the daily, three month and annual inspections in accordance with the specifications and to pay attention to the torque requirement. Please contact me if you require any additional information. Sincerely, Cathleen Roughan Regulatory Affairs Manager cc: Mr. John Kinneman U. S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406 Mr. Steve Baggett Sealed Source Safety Section Source Containment and Devices Branch Division of Industrial and Medical Safety, NMSS U. S. Nuclear Regulatory Commission 1 White Flint North 11555 Rockville Pike Rockville, Maryland 20852 *** END OF DOCUMENT ***

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