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
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