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
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
Certain materials and fuel cycle licensees who may use the subject TLDs.
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
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,
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
Attachment: List of Recently Issued IE Information Notices
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