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

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These existing casks were designed to transport short-cooled (6 months or less) irradi-
ated fuel, consistent with the earlier expectation of rapid recycling of fissile materials.
The current situation, however, indicates that most spent fuel transport will involve fuel
that has been cooled for at least several years. Consequently, there appears to be consid-
erable incentive to build a fleet of casks specifically designed for this long-cooled fuel
because its lower thermal and radiation output would permit an increase in cask capacity and
a reduction in handling costs. Several cask fabricators have announced new cask construc-
tion programs; some of these address the prospect of transporting long-cooled fuel.
Existing cask designs are for the transportation of unpackaged spent fuel. Transporta-
tion of spent fuel that has been packaged in canisters (either as intact spent fuel or as
treated spent fuel) will require some additional design modifications. If existing casks
or cask designs cannot be suitably modified, new cask designs may be required.
Past experience indicates that an estimated six to eight years could be required to
design, test, license, and then fabricate a fleet of newly designed casks. However, with a
licensed standard cask, a vendor could significantly shorten the length of time required to
deliver a fleet of casks. The useful life of spent fuel shipping casks is estimated to be
20 to 30 years.
Several factors can influence the choice of rail or truck casks for use in the shipment
of spent fuel. Rail casks have a significantly larger payload than truck casks. About
10 times as much fuel can be shipped in a rail cask with an increase in shielding weight of
only about a factor of 4 over the amount required for a truck cask. On the other hand,
truck shipments normally require less time for completion than rail shipments. About 50%
of the reactors now operating in the U.S. or scheduled for completion by 1980 do not have
rail spurs at the site. Many of these reactors without rail spurs can be serviced by inter-
modal (truck or rail) casks, which require overweight permits for shipment by truck to the
nearest rail siding.
In this Statement, it is assumed that 90% of unpackaged spent fuel will be shipped from
reactors by rail and 10% by truck. To accommodate the reactors without rail access, half
of the rail shipments are assumed to be in intermodal casks that allow truck shipment for
short distances. Shipments from interim storage to repositories or reprocessing are assumed
to be 100% by rail. Any shipments of packaged spent fuel are assumed to be by rail using
casks that can handle 7 PWR or 17 BWR packaged assemblies. Spent fuel in the once-through
cycle is assumed to cool at least five years before shipment. In the assumed reprocessing
cycle, however, spent fuel (which is not a waste in this cycle) can be shipped to a repro-
cessing plant after one year cooling.
Transport of spent fuel by barge and by ship has also been considered. Barge transport
is an alternative when both the nuclear power plant and the encapsulation or storage
facility are on navigable waterways. Barge transport suggests high payloads and low tar-
iffs. However, cost gains in these two areas could be offset by the longer transit times
estimated for barge shipments. Should offshore (floating) nuclear power plants be con-
structed, barge transport is an obvious choice for the initial portion of the journey of the