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

5.11
packed around each package. After all holes are filled, the entire tunnel system is filled
with a mixture of sand and bentonite similar to that used in the storage holes.
A "reference group" made up of members of the Swedish Corrosion Research Institute
concluded that the stainless steel/lead/titanium composite canister could be expected to
remain intact for 500 to 1000 yr, even when very pessimistic assumptions were used (KBS
1978, p. 110).
At least two waste package designs appear capable of achieving the longer life sought
for spent fuel disposal. In one design the spent fuel is encapsulated, after about 40 yr
of interim storage, in copper canisters 77 cm in diameter with walls 20 cm thick (KBS 1978).
The other design utilizes a synthetic corundum (A1 20 3 ) canister. A feasibility study has
shown that it is possible to manufacture such canisters using hot isostatic pressing. Each
canister would have an interior diameter of 0.3 m, a 100-mm-thick wall, and be about 3 m
long.
Although the Swedish waste disposal packages may be more complex than some packages
now under study, they have served to increase our understanding of long-term package
performance.
5.1.2.4 Current Status of Waste Package Development in U.S.
Extensive testing and development studies on various individual barrier components of
the waste package system, under expected conditions of geologic isolation, have been in pro-
gress for several years. These studies are being conducted in industrial and national
laboratories and in universities. While most of the studies are not complete, data and
results generated during the past few years indicate that components of the waste package
system, individually and in combination, can prevent or minimize release of radionuclides
outside of the repository by functioning as effective chemical and physical barriers
(Katayama 1979, Ross and Mendel 1979, Braithwaite and Molecke 1978, McCarthy et al. 1979,
Magnani and Braithwaite 1978 and Nowak 1979).
Through laboratory materials performance evaluation under realistic repository environ-
mental conditions and accelerated aging tests, a number of waste package candidate materials
are being selected. Following laboratory testing, nonradioactive bench-scale experiments
and radioactive hot cell experiments are planned. These tests employ small-scale mockups
of complex systems or groups of system components to investigate the influence of components
upon each other. For example, leaching/corrosion studies utilizing a scaled down canister
of an actual waste form with rocks and ground waters are in progress (ONWI-9(4)).
The logical culmination of a series of studies investigating waste package material
performance and qualification is a field test specific to each repository rock type which
involves all components of the waste package. The extent of field testing will be deter-
mined from the analysis of earlier results. Various aspects of required laboratory and
field tests have been described by the U.S. Geological Survey and the DOE in the Earth
Science Technical Plan (DOE/USGS 1980 ). A Waste Package Design, Development, and Test Plan
is being formulated to direct development efforts in an effective and timely manner. An