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Information Notice No. 96-33: Erroneous Data from Defective Thermocouple Results in a Fire
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS WASHINGTON, D.C. 20555 May 24, 1996 NRC INFORMATION NOTICE 96-33: ERRONEOUS DATA FROM DEFECTIVE THERMOCOUPLE RESULTS IN A FIRE Addressees All material and fuel cycle licensees that monitor temperature with thermocouples. Purpose The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert addressees to an incident where a defective thermocouple caused an evaporator to run at an excessively high temperature, resulting in a fire. It is expected that recipients will review the information for applica- bility to their facilities and consider actions, as appropriate, to avoid similar problems. However, suggestions in this information notice are not NRC requirements; therefore, no specific action nor written response is required. Description of Circumstances On February 21, 1996, a licensee had a fire in the ventilation system of its liquid waste process. The licensee's investigation determined that the fire was caused by a type-J thermocouple manufactured with reverse polarity. The type-J thermocouple was part of a Pulse Combustion Drier put into operation in 1985 to evaporate waste water. The drier operates with natural gas that ignites inside the drier combustion chamber. Waste water is pumped into the hot gases being expelled from the combustion chamber within an evaporation cone. The temperature is controlled by regulating the amount of waste water being fed into the system. This is based on temperature readings from a thermocouple in the duct work. The licensee had replaced the thermocouple with a spare unit while trouble- shooting a lead wire problem on February 15, 1996. The spare thermocouple was found to have reverse polarity during a test run, and the licensee believed it had corrected the problem by reversing the lead wire polarity at the instrument. The system appeared to read correctly during a 10-minute test run. However, approximately an hour into a full run the next day, the temperature reading began to behave erratically. The temperature readings dropped even though the actual temperature was increasing. By the time the licensee identified the discrepancy, a fire had started in the dust collector filter cartridges. The defective type-J thermocouple was purchased in 1985 (as a spare part), along with the Pulse Combustion Drier from Sonodyne Industries in Portland, Oregon. The thermocouple had been manufactured for Sonodyne Industries by 9605220019. IN 96-33 May 24, 1996 Page 2 of 2 Gulton Measurement and Control Systems Division (a division of Gulton Industries) in East Greenwich, Rhode Island. The licensee reported that Sonodyne Industries is out of business and Gulton Industries is no longer manufacturing thermocouples. Discussion NRC is not aware of any other Sonodyne driers currently being used by NRC licensees. Licensees that operate waste water evaporators or other heat- generating systems using thermocouples may wish to consider reviewing the source of the thermocouples and testing the polarity of thermocouples in stock. This information notice requires no specific action nor written response. If you have any questions about the information in this notice, please contact the technical contact listed below or the appropriate regional office. signed by signed by Elizabeth Q. Ten Eyck, Director Donald A. Cool, Director Division of Fuel Cycle Safety Division of Industrial and and Safeguards Medical Nuclear Safety Office of Nuclear Material Safety Office of Nuclear Material Safety and Safeguards and Safeguards Technical contact: Kevin M. Ramsey, NMSS (301) 415-7887 Internet:kmr@nrc.gov Attachments: 1. List of Recently Issued NMSS Information Notices 2. List of Recently Issued NRC Information Notices
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