Information Notice No. 82-42: Defects Observed in Panasonic Model 801 and Model 802 Thermoluminescent Dosimeters

                                                       SSINS NO.: 6835 
                                                       IN 82-42 

                               UNITED STATES 
                           WASHINGTON, D.C. 20555 

                              November 5, 1982 

Information Notice No. 82-42:   DEFECTS OBSERVED IN PANASONIC MODEL 801 
                                   AND  MODEL 802 THERMOLUMINESCENT 


All NRC licensees 

Description of Circumstances: 

Many licensees use thermoluminescent dosimeters (TLDs) for personnel 
radiation monitoring. One of the major suppliers of these TLD systems is the
Panasonic Industrial Company. It has come to the attention of the NRC that 
Panasonic Model 801 and Model 802 dosimeters have exhibited a defect that 
could reduce the response of affected elements. Panasonic has sent a letter 
to its customers describing the problem and providing actions to be taken in
case the defects are found in the customers' dosimeters. A copy of this 
letter is attached. The purpose of this Information Notice is to inform NRC 
licensees of the defect and its significance and how to respond if their 
dosimeters are affected. 


In September 1982, during an interlaboratory calibration check, the NRC 
noted a decrease in the response of a number of the dosimeters which it uses 
in its TLD Direct Radiation Monitoring Network. Inspection of the dosimeters
indicated that the affected elements had bubbles on the carbon-coated 
polyamide backing material and the aluminum substrate. The bubbles affect 
the heat transfer and thus the calibration. When these defects were 
discussed with the manufacturer, NRC staff learned that four other customers 
had also observed the same defect in their dosimeters. The precise cause of 
the defect is not yet known with certainty, but the following 
characteristics have been observed thus far: 

1.   Affected dosimeters apparently lose sensitivity to a variable degree, 
     thus underestimating radiation exposure. The NRC has observed response 
     reductions as high as a factor of two and other users have reported 
     even greater reductions. 

2.   The effect appears to occur randomly. Though two dosimeters may be 
     handled identically and have the same production date, one may produce 
     a bubble in one or more elements and the other may not have any. 

3.   The bubbles usually appear on the carbon-coated polyamide backing 
     material but have also been seen on the aluminum substrate. Changes in 
     element calibration factors may also indicate the presence of a defect;
     however, bubbles have been observed that have not significantly 
     affected element calibration factors. The bubbles are large and easily 

                                                         IN 82-42  
                                                         November 5, 1982 
                                                         Page 2 of 2 

4.   The effect has been seen on both lithium borate and calcium sulfate 
     elements, but more frequently on the latter. 

Although Panasonic believes that this defect is the result of manufacturing 
problems at the factory, the possibility that the defect may be reader-
related has not been ruled out, because of possible TLD element overheating.


NRC licensees are required to perform personnel radiation monitoring in 
accordance with 10 CFR 20.202. Licensees who use Panasonic Model 801 or 
Model 802 TLD systems should verify that their dosimeters continue to 
respond accurately and should be prepared to take compensatory actions if 
the defects described herein appear on their dosimeters. Other Panasonic 
models that employ calcium sulfate elements may also be affected and should 
be checked as well. The only way to ensure that one's dosimeters are not 
affected is to visually examine each dosimeter. Therefore, recalibrations 
and visual examination of dosimeters should be sufficient to identify 
damaged dosimeters. The dosimeters should be recalibrated whenever bubbles 
are observed. Where damaged dosimeters are detected, personnel exposure 
should be re-evaluated using data from undamaged elements or by using other 
available dosimetry such as self-reading dosimeters. 

No written response to this information notice is required. If you need 
additional information regarding this matter, contact the Administrator of 
the appropriate NRC Regional Office. 

                              L. I. Cobb, Director 
                              Division of Fuel Facilities, Materials 
                                and Safeguards 
                              Office of Inspection and Enforcement 

Technical Contact:  J. Metzger 

1. Ltr. fm Panasonic Industrial Co. to its 
     customers signed by Panasonic Natl. 
     Sales Manager. 
2. List of Recently Issued Information Notices  


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