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

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relative to waste treatment and packaging requirements for an island mined repository, and
considerable development activity might be required if the waste form and package concepts
developed for mined repositories proved unsuitable for the island repository environment.
The island concept would also require development of ocean transport and related transship-
ment facilities. Development of this equipment, however, is not viewed as particularly dif-
ficult, but largely an extension of existing technology.
The technology and methodology for siting geologic and subseabed repositories are
developed to the point that they may be implemented. Space is unique in that the final
location for disposition is not severely restricted by terrestrial concerns. Other options
are poorly developed with respect to siting technology.
Implementation of the subseabed option, in addition to requiring development of the
transshipment and ocean transport technology, would also require development of emplacement
and emplacement monitoring technology, suitable waste form and packaging for the subseabed
environment, and recovery technology for emplaced waste packages.
Space disposal would require development of a number of supportive technologies. Some
(e.g., the space shuttle) are currently under development for other purposes and much of
the remaining hardware represents extension of existing technology.
The very deep hole concept would require a significant extension of existing technology
if the 10,000-m depth is required. Of the techniques available for making deep holes only
rotary drilling has been used to develop wells to depths approaching those envisioned for
very deep holes. Rotary drilling has been used for drilling to depths of about 9,000 m at
bottom diameters of 6-1/2 inches--both shallower and of less diameter than postulated for
the reference very deep hole concept. Deeper holes of larger diameter are thought possible
but have not been demonstrated. It is quite possible that 10,000-meter holes will not be
required by the concept. Other current limitations include casing to required depths and
tensile strength of wire rope. In addition to technology related to making the very deep
hole, development of a suitable waste form and packaging is required.
Availability of Technology for Adequate Performance Assessment
All of the alternative options appear to require further development of performance
assessment and integrated safety and reliability analysis; however, the extent of such
development is likely to be far greater with those concepts which have not received substan-
tial attention, especially very deep hole, island mined repository, and space disposal.
Fewer performance uncertainties appear to be associated with the subseabed concept; consid-
erable research is underway on the deep ocean environment and the sediments are a homoge-
neous and probably fairly predictable environment. Fewest uncertainties appear to be asso-
ciated with the mined repository concept largely because of the greater amount of research
that has been accomplished on this concept.
The following order of decreasing preference is suggested relative to the current
status of development of the concepts: mined repository; subseabed/island mined repository;
space/very deep hole.