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

Timing
6.183
The timing of implementation of a waste management system could potentially affect the
feasibility of the concepts because of declining decay heat generation rates or by the
availability of facilities required to implement the concept. Substantial reduction of
decay heat rates prior to emplacement of spent fuel or high-level waste could conceivably
affect the operation of the rock melt and the ice sheet concepts; however reduction in decay
heat rates over the time frames being considered for deferred fuel cycles do not appear to
be great enough to materially affect operation of either of these concepts. Postponement
of waste disposal operations beyond the period when light water power reactors were the
dominant commercial type could impact the transmutation concept by requiring alternative
transmutation devices. However, alternative devices, including fast breeder fission
reactors and fusion devices, may be available and probably superior to light water reactors
(Croff et al. 1980). Thus it is not felt that any concept can be dismissed on the basis of
timing alone.
Summary of Fuel Cycle Issues
In summary, it appears that all of the concepts offer some potential benefit with any
fuel cycle and that none should be dismissed because of sensitivity to fuel cycle issues
(although the case for transmutation with a once-through fuel cycle appears to be quite mar-
ginal). Pursuit of the rock melt, well injection, transmutation or space disposal concepts
with either fuel cycle would require concurrent development of one of the concepts capable
of disposing of TRU waste, probably a mined repository.
6.2.3.9 Concepts Should Be Independent of Reactor Design Issues
None of the concepts appear to be especially sensitive to reactor design issues.
6.2.3.10 Implementation of a Concept Should Allow Ability to Correct or Mitigate Failure
This standard tends to favor those concepts in which wastes may be readily retrieved
if observations of their actual behavior under full-scale implementation reveal previously
unanticipated defects in the disposal system. Mined geologic disposal lends itself most
readily to this requirement although obviously attempts at transmutation could easily be
abandoned if large-scale operations failed to work.
Those concepts in which retrieval from a large-scale sy:.tem would be difficult or
impossible fail to meet this requirement. These concepts include space disposal, rock
melt, well injection, and under certain circumstances, ice sheet disposal.
6.2.3.11 Maintenance or Surveillance Should Not Be Required for Extended Periods Following
Termination of Active Repository Operations
The resolidification period of 1,000 years required of the rock melt concept would
appear to require surveillance for a substantial period to verify long-term stability and
satisfactory containment of the molten mass. This is seen as sufficiently contrary to this