1
Neutron Effective Dose calculation behind
Concrete Shielding of Charge Particle
Accelerators with Energy up to 100 MeV
V. E Aleinikov, L. G. Beskrovnaja, A. R. Krylov
Joint Institute for Nuclear Research, Dubna,
Russia
2
Introduction
All accelerators of the charged particles
with energy up to 100 MeV represent a
complex geometrical design with set of
sources of radiation. The most penetrating
component of radiation at the working
accelerator is the neutrons of a wide energy
spectrum.
3
Introduction
Calculations
of
shielding
and
the
doses
of
neutrons
behind
shield
are
used
various
methods
and,
created
on
their
basis,
algorithms
:
•
Method
Monte
-
Carlo
allows
carrying
out
direct
modeling
of
radiation
transport
through
substance
in
real
geometry
.
The
codes,
created
on
its
basis,
require
essential
expenses
of
computer
time
at
account
of
a
dose
behind
rather
thick
shields
.
•
Much
more
practicable
method
is
phenomenological
approach
based
on
existent
experimental
and
calculated
data
of
dose
attenuation
by
shielding
.
4
The purpose is
comparison of results
of calculations of neutron doses
behind concrete shielding by
method Monte
-
Carlo and
phenomenological method
.
5
Methods used
The calculation by a method of Monte
-
Carlo was carried out with the program
MCNP4B (package of libraries DLC189). The
statistical error of the calculat
ed data
did
not
exceed 5%.
6
The phenomenological method
based on following expression
was used :
E
d
E
B
E
h
R
f
E
d
E
ef
/
exp
,
2
This
equation
applies
to
a
source
of
monoenergetic
neutrons
of
energy
E
with
symbols
having
the
following
meanings
:
Е
ef
(d,
Е
)
is
the
effective
dose
behind
shield
with
thickness
of
d
;
f
is
the
neutron
yield
per
steradian
;
R
is
the
distance
from
the
source
to
the
point
of
interest
outside
the
shield
;
h(E)
is
the
conversion
coefficient
that
relate
neutron
fluence
to
the
effective
dose
;
B(E)
is
the
build
-
up
factor
of
neutrons
;
(
Е
)
is the attenuation length for effective dose through the shield.
7
The geometry of calculation
Geometry of barrier shielding was chosen for comparison of
calculation methods. The thickness of
the
shield
varied from 25
с
m up
to 300
с
m with a step 25 cm. The calculations have been performed by
Monte Carlo and
phenomenological methods for monoenergetic
neutrons with energy from 5 MeV to 100 MeV as well as for neutron
spectra produced by protons with energies of 30 MeV and 72 MeV in
thick targets.
Neutron
Source
нейтронов
d
30
O
Location of dose
calculation for
phenomenological
method
Cell for M
onte Carlo
calculation: cylinder
h = 50cm, r = 75 cm
5
m
10 m
8
Comparison between Monte Carlo and phenomenological methods
calculated
data of neutron effective dose attenuation by concrete.
Isotropic
p
oint
neutron
source
with energy
5, 20, 50
and
100
MeV at
5
m
from shield.
0
50
100
150
200
250
300
10
-11
10
-10
10
-9
10
-8
10
-7
10
-6
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
5 MeV
20 MeV
50 MeV
100 MeV
Attenuation faktor of neutron effective dose
Shielding thickness(d), cm
Calculation by Monte-Carlo method
for energy neutron
Е=5 МэВ
Е=20 МэВ
Е=50 МэВ
Е=100 МэВ
9
20
30
40
50
60
70
80
90
100
1E-13
1E-12
1E-11
1E-10
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
3m
2m
1m
Effective dose, pSv
Neutron energy, MeV
The
neutron
effective
dose
as
a
function
of
incident
neutron
energy
calculated
for
concrete
shield
of
the
thickness
indicated
.
Phenomenological
method
,
Monte
-
Carlo
10
0
2
4
6
8
10
0
2
4
6
8
10
Y Axis Title
X Axis Title
###
1,0
1,5
2,0
2,5
3,0
1E-8
1E-7
1E-6
1E-5
1
2
Effective dose, pSv
Shielding thickness, m
Comparison
of
effective
dose
calculations
as
a
function
of
a
concrete
shield
thickness
when
the
shield
irradiated
by
neutrons
produced
in
a
copper
thick
target
by
protons
with
energies
of
72
MeV
at
an
angle
of
9
0
with
an
axis
of
proton
beam
:
1
–
phenomenological
method
,
2
-
Monte
-
Carlo
11
1,0
1,5
2,0
2,5
3,0
1E-8
1E-7
1E-6
1E-5
1
2
Effective dose, pSv
Shielding thickness, m
Comparison
of
effective
dose
calculations
as
a
function
of
a
concrete
shield
thickness
when
the
shield
irradiated
by
neutrons
produced
in
a
copper
thick
target
by
protons
with
energies
of
72
MeV
at
an
angle
of
9
0
0
with
an
axis
of
proton
beam
:
1
–
phenomenological
method
,
2
-
Monte
-
Carlo
12
1,0
1,5
2,0
2,5
3,0
1E-13
1E-12
1E-11
1E-10
1E-9
1E-8
1E-7
1E-6
2
1
Effective dose, pSv
Shielding thickness, m
.
Comparison
of
effective
dose
calculations
as
a
function
of
a
concrete
shield
thickness
when
the
shield
irradiated
by
neutrons
produced
in
a
copper
thick
target
by
protons
with
energies
of
30
MeV
at
an
angle
of
0
0
with
an
axis
of
proton
beam
:
1
–
phenomenological
method
,
2
-
Monte
-
Carlo
13
10
100
10
15
20
25
30
35
40
2
1
Attenuation length, cm
Neutron energy, MeV
The
variation
of
the
attenuation
length
of
effective
dose
for
monoenergetic
neutrons
in
concrete
as
a
function
of
neutron
energy
.
1
–
phenomenological
method
,
2
-
Monte
-
Carlo
14
20
30
40
50
60
70
80
90
100
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
2
1
Build-up factor
Neutron energy, MeV
.
Build
-
up factor for effective dose of neutrons
:
1
–
phenomenological
method
,
2
-
Monte
-
Carlo
15
Conclusions.
Data
obtained
by
these
two
methods
agree
within
factor
2
over
considered
range
of
neutron
energies
and
shielding
thickness
.
Comparison
of
the
results
shows
that
difference
in
shield’s
thickness
between
calculated
by
Monte
Carlo
and
phenomenological
method
is
not
exceeded
half
-
value
layer
for
neutron
effective
dose,
that
is
from
10
cm
to
30
cm
for
considered
energies
and
thickness
of
shields
.
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