Information Notice No. 81-37, Revision 1: Unnecessary Radiation Exposures to the Public and Workers During Events Involving Thickness and Level Measuring Devices

                                                      SSINS No.: 6835 
                                                      Accession No.: 
                                                      IN 81-37, Rev. 1 

                                UNITED STATES
                           WASHINGTON, D.C.  20555

                              February 9, 1982

Information Notice No. 81-37, Rev. 1:     UNNECESSARY RADIATION EXPOSURES 
                                             TO THE PUBLIC AND WORKERS 
                                             DURING EVENTS INVOLVING 
                                             THICKNESS AND LEVEL MEASURING 


Licensees holding byproduct material licenses have recently received IE 
Information Notice No. 81-37 dealing with unnecessary radiation exposures to
the public and workers during events involving thickness and level measuring
devices.  Further NRC staff review of the circumstances of Case 2 suggests 
that licensees using measuring devices may not always be totally familiar 
with their licensed devices and associated equipment.  This supplemental 
information is intended to reemphasize the need to assess the capability of 
the device to maintain full integrity in adverse environments--in this case,
a high-temperature environment.  Additionally, associated equipment, the 
radiation detector in this case, would have shown that the radioactive 
source was not fully shielded.  This information should be brought to the 
attention of all persons involved in the administration and operation of the 
facilities using licensed measuring devices.  

Description of Circumstances (Case 2): 

In Case 2, a level measuring device containing a 10 curie cesium-137 sealed 
source was subjected to a high-temperature environment that resulted in a 
meltdown and loss of the lead shielding.  Subsequent to this event, 31 
individuals received unnecessary radiation exposures ranging from 0.14 to 3 
rems while the unshielded source remained undiscovered.  During a four-day 
period, the radiation detector, which was part of the process equipment, 
showed that the source was not shielded; however, no one had noted this 

This information is intended to remind licensees about the importance of 
being familiar with the construction and installation of their measuring 
devices and to take full advantage of associated equipment, such as 
radiation detectors, that may be part of the process. 

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

Recently issued IE Information Notices 


Page Last Reviewed/Updated Thursday, March 25, 2021