Drop Test Behavior of a Low Radioactive Waste Package
in Concrete
Sylvain Tholance, ATR Ingénierie
Background:
In the context of achieving a deep storage
of long life radioactive waste ANDRA is studying
different concepts of packages to store LLMA (Long Life
Medium Activity)
waste and C ones (High Activity) and for
spent fuel. Studies on the handling of LLMA storage packages
showed that the
risk of falling exists, especially at the
time of placing the package into the storage cell. The overall
objective
of the studies is to assess the ability of
the LLMA storage package to keep the containment of nuclear
waste in case
of fall. All dynamic simulations are performed
with RADIOSS solver, product of Hyperworks Tools.
The LLMA package is made of fiber-reinforced
concrete. Their size and weight vary according
to the dangerousness of the inner substance.
The B2.1 package has a generally cubic
shape (1.5 m square) for a total weight of
approximately 6-7 tons. The body is composed
of 4 cells where wastes are placed.
A precast concrete cover is anchored to the
body by 5 bolts. Two concepts of the body
are assessed: a standard model using
reinforcement and low density steel fiber and
an alternative one unarmed but with a greater
fiber density.
Simulation and Testing:
The first stage of simulations is to characterize
the behaviour of fiber reinforced concrete
and to identify the parameters of concrete
law n°24 of RADIOSS from a
confrontation testing - calculations on specimens:
tests of simple compression, simple tension,
bending 4 points, etc..
The concrete laws are then injected into the
complete FE models of B2.1 package. Drop tests
at scale 1 were carried out to
validate the concepts and qualifying simulations.
Results:
The 2 concepts B2.1 packages have successfully
completed the drop test on the corner of
6 meters high. The wastes placed inside are weakly
damaged and the behaviour
of the concrete storage package is satisfactory:
the closing of the package is maintained
and cracking generally does not
affect the handling ability after fall. For
the 2 concepts, the lid is kept on the body
through the anchoring system.
The extent of cracks and openings are particularly
more pronounced on the alternative concept
unarmed. The safety margin seems
less important.
The simulations provide results close to
reality in terms of overall behaviour in
terms of crush at the corner, cracking and general solicitation
on the waste. It remains
to better control the dispersion caused by
the manufacturing of the package body and
of fiber concrete itself on fall resistance
of packages to reach more robust design.
Perpectives:
Subsequent studies will be done with stochastic
analysis (Design of experiments, Optimization,
Robustness) implementing the abilities
of HyperStudy (DSS).
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