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

5.89
If the 0.5 ha of contaminated land were occupied by a housing project soon after the
drilling incident with about 0.1 ha per lot, five families (probably about 25 individuals)
might be exposed to the same extent as the maximum individual.
Seventy-year accumulated doses calculated for the regional population amounted to
1.1 x 10 2 man-rem in the case of spent fuel and 1.6 x 102 man-rem in the case of repro-
cessing wastes. All of the doses to the regional population (whose exposure would result
principally from resuspension and air transport of radionuclides) are substantially less
than those which would be received from naturally occurring radioactive sources
(1.4 x 107 man-rem over the same period).
In the case of a repository in salt, the land (0.5 ha) would likely be contaminated
with salt brought up with the drilling mud. As developed in more detail in DOE/ET-0029 the
resulting ground contaminated by salt would not be well tolerated by ordinary crops.
Breach of a waste canister by exploratory drilling, if it occurred, could result in a
small increase in risk of adverse health effects occurring among about two dozen people in
the immediate area.
If exploratory drilling that reached the repository level were abandoned (whether a
canister had been penetrated or not) it could provide a means of entry of water into the
repository. It is believed that the bore hole would not remain open for long but if it did
and significant quantities of water were to flow in and out the consequences would not rea-
sonably exceed those described previously for faulting and flooding of a repository.
The key to mitigating action associated with a drilling accident is the discovery that
radioactive material had been encountered. As stated, that knowledge would probably come
from assay of the drill core or samples of the drilling mud. If the driller is aware that a
drill has brought waste to the surface, standard decontamination methods could be used to
recover the contaminants, dispose of them under suitable controls, and preclude essentially
all of the previously mentioned radiological consequences.
5.5.5 Solution Mining
In this scenario a 47,000 MTHM example geologic repository in domed salt(a) is breached
by solution mining 1000 years after the repository is closed. Although this accident is typi-
fied by solution mining for salt recovery, solution mining is also used for extraction of
other resources and for construction of underground storage cavities. This accidental breach
of a repository is believed to be conceivable only for an industrialized society having tech-
nological capabilities substantially as exist today.
Basically, solution mining in domed salt involves drilling a well to the desired level
and inserting a double-walled pipe so that water can be forced down the outer pipe into the
salt, where it dissolves the salt into a brine and forces the brine back up through the cen-
ter pipe (Kaufmann 1960). The life of such solution wells varies markedly, some failing in
(a) Solution mining of stratified salt is believed less likely than in dome salt because
of less evidence suggesting the presence of salt.