United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 85-42, Revision 1: Loose Phosphor in Panasonic 800 Series Badge Thermoluminescent Dosimeter (TLD) Elements

                                                        SSINS No.:  6835  
                                                         IN 85-42, Rev. 1  

                                UNITED STATES
                       NUCLEAR REGULATORY COMMISSION 
                    OFFICE OF INSPECTION AND ENFORCEMENT 
                           WASHINGTON, D.C. 20555 

                              August 12, 1985 

Information Notice No. 85-42 Rev. 1: LOOSE PHOSPHOR IN PANASONIC 800 
                                        SERIES BADGE THERMOLUMINESCENT 
                                        DOSIMETER (TLD) ELEMENTS 

Addressees: 

Certain materials and fuel cycle licensees who may use the subject TLDs. 

Purpose: 

This information notice was previously issued on May 29, 1985 and addressed 
to all holders of a nuclear power plant operating license or construction 
permit. This revision is being issued to inform certain materials and fuel 
cycle licensees that were inadvertently omitted when the notice was first 
issued to power plant licensees. No other revisions have been made to this 
information notice. 

The notice was provided to alert NRC licensees to a problem noted in some 
Panasonic 800 series TLD badges that has caused spurious high readings in 
one of the badges' TLD elements. This information is intended to assist 
licensees in diagnosing any spurious readings with the Panasonic TLD system.

It is expected that recipients will review the information provided for 
applicability, if appropriate, to their dosimetry programs. However, 
suggestions contained in this information notice do not constitute NRC 
requirements; therefore, no specific action or written response is required.

Description of Circumstances: 

The Panasonic 800 series TLD badge contains a card that holds four TLD 
elements. Each TLD element consists of a thin film of TL phosphor attached 
to a disk backing with a clear teflon bubble cover. During reading, the 
phosphor is heated by converging infrared light on the backing. The 
luminescence from the phosphor (which is proportional to the dose received) 
radiates through the teflon cover and is read with a photomultiplier tube. 

Several Panasonic TLD users (including NRC's Region I) have identified 
badges where crystals of the phosphor have detached themselves from the 
backing of the element, resulting in high erratic readings in that element. 
When viewed through a, stereoscopic microscope, phosphor crystals can be 
observed sticking to the teflon cover (presumably by electrostatic charge). 
In this position,  



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                                                           IN 85-42, Rev. 1 
                                                           August 12, 1985 
                                                           Page 2 of 2     

the loose TL material is not in contact with the backing and does not get 
heated when the badge is read. These TL crystals remain at an elevated 
energy state and continue to accumulate dose. Apparently erratically high 
readings result when the loose crystals are shaken back onto the backing 
surface during a subsequent reading. They are then heated and luminescence 
proportional to the total doses received during several read cycles is 
produced. This process can cause the affected element to erroneously read as
much as an order of magnitude higher than the other elements in the same 
card. Although the frequency of occurrence is small (one licensee found only
one problem badge in 30,000), there is evidence that the frequency increases
substantially once the badges have been through 100-200 read cycles. 

Panasonic has a manufacturing quality control (QC) specification on the 
amount of loose phosphor in an element. However, physical shock and thermal 
cycles, experienced during badge use, appear to loosen additional material. 
Panasonic has stated that they have modified their QC program to provide a 
greater physical challenge to the badge before they are screened. For those 
badges already in use, licensees can visually inspect any TLD elements 
suspected of having loose TL crystals. Panasonic has been exchanging badges 
identified as having excessive loose TL material. 

No specific action or written response is required by this information 
notice. If you have any questions about this matter, please contact the 
Regional Administrator of the appropriate regional office or this office. 


                                   Edward L. Jordan, Director
                                   Division of Emergency Preparedness
                                     and Engineering Response
                                   Office of Inspection and Enforcement

Technical Contact:  R. L. Pedersen, IE 
                    (301) 492-9425 

Attachment:    List of Recently Issued IE Information Notices 
Page Last Reviewed/Updated Tuesday, November 12, 2013