Numerical Simulation of the Howard Street Tunnel Fire, Baltimore, Maryland, July 2001 (NUREG/CR-6793, NISTIR 6902)
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Manuscript Completed: August 2002
Date Published: January 2003
K.B. McGrattan and A. Hamins
Fire Research Division
Building and Fire Research Laboratory
National Institute of Standards and Technology
100 Bureau Drive, Stop 8600
Gaithersburg, Maryland 20899-8600
C. Bajwa, NRC Project Manager
Spent Fuel Project Office
Office of Nuclear Material Safety and Safeguards
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001
NRC Job Code J5414
This report documents a study undertaken to estimate the thermal environment of the Howard Street Tunnel in Baltimore, Maryland, following the derailment in July 2001 of a freight train and the burning of spilled tripropylene and the contents of surrounding rail cars. A numerical fire model developed by the National Institute of Standards and Technology (NIST) has been used to simulate the fire’s growth and spread in the tunnel. The fire model has been validated for this application using temperature data collected during a series of fire experiments conducted at a decommissioned highway tunnel in West Virginia. The cross-sectional area of the tunnel and the fire sizes used in the West Virginia experiments are similar to the Howard Street Tunnel.
For the Howard Street Tunnel fire, the peak calculated temperatures within the tunnel were approximately 1,000 °C (1,800 °F) within the flaming regions, and on average approximately 500 °C (900 °F) when averaged over a length of the tunnel equal to three to four rail car lengths. Because of the insulation provided by the thick brick walls of the tunnel, the calculated temperatures within a few car lengths of the fire were relatively uniform, consistent with what one would expect to find in an oven or furnace. The peak wall surface temperature reached about 800 °C (1,500 °F) where the flames were directly impinging, and on average 400 °C (750 °F) over the length of three to four rail cars. The steel temperature of the rail cars would be expected to be similar to the surrounding gas temperature because of the long exposure time and the high thermal conductivity of steel.