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

3-23 3-24
Comment Comment
Number 'lumber
.f Long-Term Effects of Repository Construction and Operation f.4 p. 3.1.32
The first paragraph does not reflect fissure and joint permeability differ-
3.f.1 pp. 3.1.5, 3.1.6, 3.1.19 ences, and induced characteristics due to construction.
One area of serious concern which appears to be neglected is the effect of
repository construction and operation and the thermal effects of the 3.f.5 p. 3.1.124
emplaced waste on the effectiveness of the geohydrologic barriers to What the GEIS is really discussing is the creation of flowpaths by creating
long-term transport of radioactive materials from the repository. The fractures or opening fractures that already exist. The question then is
following examples are cited: how does the predictive model treat the flow of liquids and transport of
dissolved radionuclides through fractures? Both flow and transport could
Construction is likely to increase hydraulic conductivity of the rock be significantly different in fractures than in porous media. We know
mass. There is no evidence presented in GEIS to show that such factors that retardation is less and, also, that retardation is the most important
have been considered. This is a serious deficiency. attenuation mechanism that has been modeled. The term "thermally induced
permeability" does not convey the difference between porous flow and
Rock fractures, joints and fissures are potential paths for increased fracture flow.
groundwater flow. Mine construction and testing may induce local fracture
conditions that may or may not be identified in sample permeability testing. 3.f.6 pp. 3.1.228, 3.3.22, 3.3.27, 3.3.30
However, the in situ extent of fractures, joints, and fissures could pp. 7.4.6, DOE/ET-0028 o
produce increased groundwater flow in other than direct downgradient The general impression conveyed regarding the sealing of shafts, bore
directions. Have such factors been considered and what conclusions have holes and canister holes into an underground repository is that no sig-
been drawn? nificant problems of leakage are expected. This contrasts with the discussion
of the same activities associated with disposal of wastes by the
3.f.2 pp. 3.1.9, 3.1.13, 3.1.14 very deep hole concept. If anything, the maintenance of the integrity of
pp. 7.2.15, 7.2.18, 7.2.22, 7.2.26; DOE/ET-0028 shaft seals, room seals and canister seals in an underground repository
Permeabilities of granite and basalt, while low, are not nil. If they (particularly in salt) would be expected to pose significantly greater
were, the repositories in granite and basalt could be located a few meters problems than in deep hole disposal.
beneath the weathered layer. There seems to be no appreciation that
values of permeability determined in the laboratory differ quite frequently 3.f.7 p..7.3.5; DOE/ET-0028
from effective (rock mass) permeability by several orders of magnitude. The unit cell used to analyze the maximum temperature of the waste canister
is described on page 7.3.5. It has a sleeve and an air gap. At the
3.f.3 p. 3.1.24 bottom on page 7.4.6 it is stated: "After the readily retrievable period,
Thermal uplift around the repository is expected as a result of the thermal use of sleeves in emplacement holes is discontinued and holes are backfilled
loading. This may increase effective hydraulic conductivities of the host with crushed rock after canister placement." Emplacement of waste canisters
rock and may even result in the creation of a flow path between overlying without the sleeves does not appear to be considered in the thermal analysis.
aquifers and the repository.