United States Nuclear Regulatory Commission - Protecting People and the Environment

Morning Report for January 28, 2004

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Part 21 - 2003-0033-00 - Potential Failure of Model 977-201 and 977-210 Wide Range Ion Chamber Area Monitors


Solon, Ohio

License No:

MR Number: H-2004-0006
Date: 12/23/2003

Source Document: Letter



Part 21 - 2003-0033-00 - Potential Failure of Model 977-201 and 977-210 Wide Range Ion Chamber Area Monitors

This morning report is being issued due to a safety concern regarding a potential failure of wide range ion chamber area monitors distributed by Cardinal Health Radiation Management. Apparently, an incorrect radiation value might be displayed due to a noncatastrophic failure of the detector high voltage power supply in the Wide Range Ion Chamber Area Monitors manufactured between 10/1/90 and 11/1/03. The Model 945A Wide Range Ion Chamber Area Monitor consists of a Model 946A-200 Control Room Readout and a Model 977-201 or Model 977-210 Digital Preamplifier/Detector. Both the readout and preamplifier are microprocessor-controlled devices, and communicate via a modified RS232C protocol. The readout and detector operate together as a Wide Range Area Radiation monitor, designed to monitor the radiation levels in a specific area, and to warn personnel of an increase in radiation level above predetermined set points. In the units subject to this notification, a failure in the high voltage power supply circuit may result in a detector high voltage bias that is less than the voltage required for 100% collection efficiency. With the reduced collection efficiency, the value displayed at high radiation levels will be inaccurate and will read low.

The vendor (Cardinal Health Radiation Management) was contacted, and they stated that there will be letters sent to all customers by February 15, 2004. The only facility known at this time to have this issue is First Energy (Davis-Besse). The vendor also stated an Engineering Change Notice (ECN) has been initiated and is scheduled to be completed by March 31, 2004.

Information for this issue as well as other Part 21s is available at the NRC's Operating Experience web page at: http://www.nrc.gov/reading-rm/doc-collections/event-status/

Accession Numbers:

Accession No Accession Date
ML033630565 12/23/2003


Name Office Abbrev Phone No E-Mail
HEATH, MAURICE L NRR (301) 415-3137 MLH5@nrc.gov
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