Management of Commercially Generated Radioactive Waste - U.S. ...

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which is postulated to result in large releases of radioactive material, may be substan-
tially reduced with these additional transportation personnel. Thus, if a severe accident
does occur, consequences may be partially mitigated compared to the severe accidents
described here.
Truck and rail transport of spent fuel are both expected to be used in the once-through
fuel cycle. Descriptions of the systems considered in the analysis along with detailed
accident descriptions are reported in DOE/ET-0028. Dose calculations for postulated acci-
dents are reported in DOE/ET-0029. Accident frequency estimates cited in this section are
based on an assumed 250 GWe nuclear industry.
The impacts examined in DOE/ET-0028 and DOE/ET-0029 were developed assuming unpackaged
short-cooled (6 months out of the reactor) spent fuel. These impacts are thus much more
severe than those from accidents involving long-cooled fuel. They also do not take into
account the mitigation of impact that is likely to result from the new escorting regulations.
Similar accidents are also plausible for packaged spent fuel if transportation is
required following packaging. However, since packaging provides an additional barrier to
release of nuclides in transportation of spent fuel, the releases would be smaller and more
infrequent than for unpackaged spent fuel. For this reason, specific accidents for packaged
spent fuel transport are not discussed but can be assumed to cause lesser impact than
unpackaged spent fuel transport.
Six accidents for truck transport of spent fuel were analyzed: three minor, two moder-
ate, and one severe. The minor accidents involved rollovers, collisions and the undetected
leakage of coolant. Only coolant leakage was expected to release radioactive material and
could result in a 70-yr accumulated dose to the maximum-exposed individual of 3 x 10 -6 rem
at an expected frequency of approximately twice per year.
The moderate accident giving the largest release of radioactive material is a fire
that activated a pressure relief valve on the cask. A 70-yr accumulated dose of
8 x 10 -5 rem to the maximum-exposed individual would occur at an estimated frequency of
about once every 50 years.
The severe accident culminating in a long-lasting fire results in a 70-yr accumulated
dose to the maximum-exposed individual of 10 rem. The estimated frequency for this accident
is about once every 50,000 years.
Eight accidents for rail transport of spent fuel were analyzed: three minor, three
moderate and two severe. Two minor accidents involved derailments and 30-minute fires; no
release occurred. The third minor accident involved undetected leakage of cask coolant.
This accident could occur up to twice per year and result in a 70-yr accumulated dose of
2 x 10 -5 rem to the maximum-exposed individual.
The moderate accidents involved cask impacts, fire-induced cask venting, and failures
in the mechanical cooling system as a result of accident forces. The cooling system fail-
ure is estimated to occur once every 50 years and results in a 70-yr accumulated dose of
8 x 10 -5 rem to the maximum-exposed individual.