Introduction Near surface trench is one of
the most common methods for
disposal of LILW.
Trench design besides waste
characteristics, site
characteristics, type of barriers
and characteristics of cover
layers are influencing on
overall safety of disposal.
Introduction LILW wastes have different
physical and chemical
properties because of their
different sources.
In long term, degradation
of waste packages due to
corrosion and also
settlement of backfill
layers and cover can
reduce safety of disposal
trench. So evaluation of
different aspects of trench
in design stage is an
important step toward
ensuring operational as
well as long term safety
disposal.
Finite Element
Simulation
Numerical methods have
been used in engineering
project, extensively.
Stability analysis of near
surface trenches in
Anarak Repository has
been evaluated by finite
element method to predict
deformations and
settlements. In primary
stage of trenches design
dimension of trenches has
been selected based on
design criteria. 2-
dimensional profile of
trench with wastes and
backfill layers has been
considered for convenient
meshing and further
analysis.
Iran Radioactive Waste Management Co. (IRWA)/ Atomic Energy Organization of IRAN/ Tehran/Iran
Material Assignment
For assignment of material
properties, elasticity properties
of host rock, backfill layers and
waste packages should be
considered. Mohr-Colomb
criterion was selected for
material properties
assignment. This area consist
of two parts include of
alluvium layers and host rock.
Conclusion
Weights of cover layers, waste
packages and backfill layers
which are considered as
external loads can influences
on trench's performance. Solid
wastes and solidified waste
after corrosion will have very
low strength and they can't
tolerate external loads and
finally settlement may occur.
Finite element simulation for
trench's geotechnical model
(as one of simulation method)
was performed to analyze the
trench deformations under
different conditions.
Displacement, plastic strain
and stress concentration in the
trenches evaluated in different
situation.
Results 1. Stability analysis of
trenches with high stiffness
and cover loads
The model was analyzed with
high stiffness for
consideration wastes in
primary conditions.
maximum stress and
deformation are 0.64 MPa
and 1.96 cm.
2. Stability analysis of
trenches with low stiffness
and cover loads
Waste packages in trenches
will corrode and baring
capacity of them will be
decreased.
These deformations can be
followed by settlements and
decrease of performance of
covers.
deformations increased to
28 cm
Study Area
The Anarak site has been
selected as disposal facility for
LILW in Iran. This site is located
in Isfahan province, about 24
km west of Anarak city and 90
km northeast of Naein. This
site has been located in a
syncline structure which
consists of clay, marl and
sandstone layer that create
good condition for controlling
of radionuclides migration.
Abstract. At this paper, simulation and stability analysis of near surface disposal trenches in Anarak Repository has been evaluated by
finite element method. Emplacing of waste packages in the trenches impose extra load to bottom and sides of trenches and it may
increase deformations in the trench walls and cover. Also corrosion of waste packages in long term may increase deformations and
settlements and finally failure of trenches may be occur. 2D model of trench containing waste packages with elasto-plastic behavior of
materials in finite element software has been designed and analyzed. Amount of deformations were measured and considered in design
of trenches.
Material Young Modulus (E)
GPa
Poisson ratio
)ν(
Friction Angle (φ)
Cohesion (C(
MPa
Host rock (clay and
marl stone)
1.96 0.23 40 6
Backfill and Soil layers 25*10-3 0.25 34 0.05
Waste Packages 204 0.29 - -
Deformation and stresses of model for wastes with low stiffness
Location of boreholes for site
characterization
MATERIAL PROPERTIES OF WASTE
PACKAGES, SOIL AND ROCKS
Conceptual Design for Near Surface
Disposal