IE Circular No. 80-24, AECL Teletherapy Unit Malfunctions

                                                            SSINS: 6830   
                                                            Accession No.: 
                                                            IEC 80-24     

                                UNITED STATES
                           WASHINGTON, D.C. 20555

                              December 2, 1980


Description of Circumstances: 

During the past several months NRC has continued to receive reports of 
malfunctions of AECL teletherapy units, Models Theratron 60 and 80 and 
Eldorado 6 and 8. According to these reports, malfunctions are occurring 
with the power cord takeup reel of the beam defining projection lamp. 

The malfunctions may have two possible consequences. First, the power cord 
from the malfunctioning takeup reel may jam the source drawer mechanism and 
prevent its return to the source "off" position. This condition can cause 
unnecessary exposure to both technicians and patients. Second, the loose 
cord may prevent the source drawer mechanism from going to the full "on" 

This condition may not be readily detected by the machine operator and thus 
may result in an incorrect dose being administered to the patient. 

Under a medical device recall action, AECL has notified all known users-of 
beam teletherapy, units, Models Theratron 60 and 80 and Eldorado 6 and 8 
concerning potential malfunction problems. If you are a user of one of these
Teletherapy Units you should have received "Warning Notices" WN-80-1, 
WN-80-2, WN-80-1A and WN-80-1B. 

Additionally, NRC investigators have noted that improper actions of 
operating personnel at the time of equipment malfunction may further 
aggravate the situation and contribute to the unnecessary exposure. However, 
these exposures can be minimized by licensees if their operating personnel 
are trained to promptly detect and react to equipment malfunctions in 
accordance with approved written operating and emergency procedures. 

Notice to Teletherapy Licensees: 

Current NRC regulations and licensing procedures require teletherapy 
licensees to develop, maintain, and use the following procedures and 
radiation monitoring equipment: 

o    Written operating, emergency and maintenance procedures. 

o    A program for inspection, testing and servicing of equipment components
     that are critical to safe operation. 

                                                          IEC 80-24       
                                                          December 2, 1980 
                                                          Page 2 of 3     

o    A radiation monitoring device that continuously monitors the 
     teletherapy beam condition. 

These procedures and monitoring system are intended to improve safe 
operation of the equipment under both normal and abnormal conditions. 

In addition to the above requirements, this circular identifies certain 
other actions which persons licensed by NRC pursuant to 10 CFR Part 35 
should take. These are noted below. 

NOTE:     Items 1, 2 and 3 are directed to those licensees authorized to use
          AECL, teletherapy units Models Theratron 60 and 80 and Eldorado 6 
          and 8. Items 4 through 10 are directed to all teletherapy 

1.   If you have not received "Warning Notices" WN-80-1, WN-80-2, WN-80-1A 
     and WN-80-1B you should immediately contact an AECL service Centre or 
     the Regulatory Affairs Branch, Quality Assurance Division, AECL-CP, 
     P.O. Box 6300, Ottawa Canada (tel. 613-592-2790). 

2.   If you have received the "Warning Notices" identified in Item 1 above, 
     you should implement the requested actions in those "Warning Notices". 
     Please give attention to "Warning Notice" WN 80-1B. 

3.   Cooperate with AECL in scheduling time for machine modification in 
     accordance with remedial action as described in their final notice. 

4.   Verify that emergency procedures are posted in accordance with license 
     conditions and that operating personnel are familiar with them. 

5.   Establish a schedule and conduct periodic drills in response to 
     simulated emergency situations. 

6.   Follow manufacturers' recommendations for inspection and maintenance 
     and, in particular, those concerning replacement of "critical 
     components". Guidelines for maintaining and procedures for inspection 
     of teletherapy equipment are also contained in ANSI N 499-1974 and ANSI
     N 449.1-1978. 

7.   Instruct operating personnel to be alert and report to responsible 
     management any changes from normal operating characteristics. An 
     example would be slower-than-normal source travel. 

8.   Initiate emergency response in the event that both "source on" and 
     "source off" signals are energized simultaneously. This is an 
     indication of less than full travel on the source drawer. 

9.   Following any malfunction or problem identification, take the equipment
     out of service until it is investigated and repaired as necessary. 

10.  Cooperate with manufacturers in engineering assessments, equipment 
     modification and recall actions. 

                                                          IEC 80-24       
                                                          December 2, 1980 
                                                          Page 3 of 3     

The information contained in this circular should be brought to the 
attention of all persons involved in the administration and operational 
aspects of teletherapy. 

No written response to this circular is required. If you need additional 
information regarding this subject, please contact this office. 


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