JAEA-Data/Code 2007-004 - Welcome to Research Group for ...

EPSI6 = 0.0 (not used)
Card-003-4 Miscellaneous data (6E12.5)
XMIS1 External extrapolated boundary constant C g
> 0 The constant for all extrapolated boundaries (See NUAC11-16) for all
groups
< 0 This is the total number of energy groups and Card-003-5 are to follow
this card, which give the group-dependent extrapolated boundary
constants for problem boundaries for all energies.
= 0 The code will use the built-in value for all extrapolated boundaries
Note:
The extrapolated boundary constant C g of energy group g is defined as
C
g
⎡−
D
= ⎢
⎢⎣
ϕ g
g
∂ϕ
g
⎤
⎥
∂x
⎥⎦
X =
X 0
(x) ϕ g
and as the extrapolated length d g is
defined by
∂ϕ g
∂x
x 0
1 ⎡ −1
∂ϕ
g
⎤
≡ ⎢ ⎥
d g ⎢⎣
ϕ g ∂x
⎥⎦
X = X
0
x0
d g
x
thus the relation C g = D g /d g holds, where D g is diffusion coefficient.
As the diffusion coefficient D g is defined as
1 λtr,
g
D g
= = ,
3Σ
3
tr,
g
the constant C g has the relation below;
C = λ / 3d
g
tr,
g
g
If the extrapolation length of the Milne’s problem
d g 0.7105λtr,
g
= is applied,
the extrapolation constant C g becomes the defaulted value (0.4692) which does not
depend on neutron energy. It is the reason to apply XMIS1=0.0 (defaulted value for
all groups). If a sufficiently large value of extrapolation constant is applied,
d g =D g /C g tends to zero so that the zero flux at the boundary is assumed.
XMIS2
The extrapolation constant for internal black absorber boundary specified by
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