Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
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
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May 24, 1996
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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
