United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9512290054


                                                  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.


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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