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> NUREG/CR-6894
Spent Fuel Transportation Package Response to the
Caldecott Tunnel Fire Scenario (NUREG/CR-6894, Rev. 1)
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Publication Information
Manuscript Completed: December 2006
Date Published: January 2007
Prepared by
H.E. Adkins, Jr., B.J. Koeppel, J.M. Cuta, A.D. Guzman ( PNNL)
C. S. Bajwa (NRC)
Pacific Northwest National Laboratory
902 Battelle Boulevard
Richland, WA 99352
A. Hansen, NRC Project Manager
Prepared for
Division of Spent Fuel Storage and Transportation
Office of Nuclear Material Safety and Safeguards
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001
Job Code J5167
Availability
Notice
Abstract
On April 7, 1982, a tank truck and trailer carrying 8,800 gallons of gasoline was involved in an accident
in the Caldecott Tunnel on State Route 24 near Oakland, California. The tank trailer overturned and
subsequently caught fire. Because this event is one of the most severe of the five major highway tunnel
fires involving shipments of hazardous material that have occurred world wide since 1949, the United
States Nuclear Regulatory Commission (USNRC) selected it for analysis to determine the possible
regulatory implications of such events for the transportation of spent nuclear fuel by truck.
The Fire Dynamics Simulator (FDS) code developed and maintained by the National Institute of
Standards and Technology (NIST) was used to determine the thermal environment in the Caldecott
Tunnel during the fire. The FDS results were used to define boundary conditions for a thermal transient
model of a truck transport package containing spent nuclear fuel. The Nuclear Assurance Corporation
(NAC) Legal Weight Truck (LWT) transportation package was selected for this evaluation, as it
represents a typical truck (over-the-road) cask.
Detailed analysis of the response of the transport package to the fire was performed using the ANSYS®
computer code. The staff concluded that small transportation packages similar to the NAC LWT would
probably experience degradation of some seals in this severe accident scenario. The maximum
temperatures predicted in the regions of the lid and the vent and drain ports exceed the rated service
temperature of the tetrafluoro-ethylene (TFE) or Viton® seals, making it possible for a small release to
occur due to CRUD that might spall off the surfaces of the fuel rods. However, any release is expected to
be very small due to a number of factors. These include (1) the metallic lid seal does not exceed its rated
service temperature and therefore can be assumed to remain intact, (2) the tight clearances maintained by
the lid closure bolts, (3) the low pressure differential between the package interior and exterior, (4) the
tendency for solid particles to plug small clearance gaps and narrow convoluted flow paths such as the
vent and drain ports, and (5) the tendency of CRUD particles to settle or plate out and consequently not be
available for release.
USNRC staff evaluated the radiological consequences of the package response to the Caldecott Tunnel
fire. The results of this evaluation strongly indicate that neither spent nuclear fuel (SNF) particles nor
fission products would be released from a spent fuel shipping package involved in a severe tunnel fire
such as the Caldecott Tunnel fire. The NAC LWT design analyzed for the Caldecott Tunnel fire scenario
does not reach internal temperatures that could result in rupture of the fuel cladding. Therefore,
radioactive material (i.e., SNF particles or fission products) would be retained within the fuel rods. The
potential release calculated for the NAC LWT package in this scenario indicates that any release of
CRUD from the package would be very small - less than an A2 quantity (see Section 8.2).
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