def bkg_xs(self, nuc, temp=300):
"""Calculates the background cross section for a nuclide (nuc)
Parameters
----------
nuc : int
Nuclide id.
temp : float, optional
The nuclide temperature in [K].
Returns
-------
sig_b : array like
Group wise background cross sections.
"""
e_n = self.src_group_struct
sig_b = np.zeros(self.src_ngroups, float)
for i, a in self.atom_dens.items():
if i == nuc:
continue
rtn = self.pointwise(i, 'total', temp)
if rtn is None:
continue
sig_b += a * bins.pointwise_linear_collapse(e_n, rtn[0], rtn[1])
return sig_b / self.atom_dens.get(nuc, 0.0)
def _load_reaction(self, nuc, rx, temp=300.0):
"""Loads reaction data from ACE files indexed by OpenMC.
Parameters
----------
nuc : int
Nuclide id.
rx : int
Reaction id.
temp : float, optional
The nuclide temperature in [K].
"""
rx = rxname.id(rx)
try:
mt = rxname.mt(rx)
except RuntimeError:
return None
totrx = rxname.id('total')
absrx = rxname.id('absorption')
ace_tables = self._rank_ace_tables(nuc, temp=temp)
lib = ntab = None
for atab in ace_tables:
if atab not in self.libs:
lib = self.libs[atab] = ace.Library(atab.abspath or atab.path)
lib.read(atab.name)
lib = self.libs[atab]
ntab = lib.tables[atab.name]
if mt in ntab.reactions or rx == totrx or rx == absrx:
break
lib = ntab = None
if lib is None:
return None # no reaction available
E_g = self.src_group_struct
E_points = ntab.energy
if rx == totrx:
rawdata = ntab.sigma_t
elif rx == absrx:
rawdata = ntab.sigma_a
else:
ntabrx = ntab.reactions[mt]
if ntabrx.IE is None or ntabrx.IE == 0:
rawdata = ntabrx.sigma
else:
rawdata = np.empty(len(E_points), dtype='f8')
rawdata[:ntabrx.IE] = 0.0
rawdata[ntabrx.IE:] = ntabrx.sigma
if (E_g[0] <= E_g[-1] and E_points[-1] <= E_points[0]) or \
(E_g[0] >= E_g[-1] and E_points[-1] >= E_points[0]):
E_points = E_points[::-1]
rawdata = rawdata[::-1]
rxdata = bins.pointwise_linear_collapse(E_g, E_points, rawdata)
return rxdata
def _load_reaction(self, nuc, rx, temp=300.0):
"""Loads reaction data from ACE files indexed by OpenMC.
Parameters
----------
nuc : int
Nuclide id.
rx : int
Reaction id.
temp : float, optional
The nuclide temperature in [K].
"""
rx = rxname.id(rx)
try:
mt = rxname.mt(rx)
except RuntimeError:
return None
totrx = rxname.id('total')
absrx = rxname.id('absorption')
ace_tables = self._rank_ace_tables(nuc, temp=temp)
lib = ntab = None
for atab in ace_tables:
if atab not in self.libs:
lib = self.libs[atab] = ace.Library(atab.abspath or atab.path)
lib.read(atab.name)
lib = self.libs[atab]
ntab = lib.tables[atab.name]
if mt in ntab.reactions or rx == totrx or rx == absrx:
break
lib = ntab = None
if lib is None:
return None # no reaction available
E_g = self.src_group_struct
E_points = ntab.energy
if rx == totrx:
rawdata = ntab.sigma_t
elif rx == absrx:
rawdata = ntab.sigma_a
else:
ntabrx = ntab.reactions[mt]
if ntabrx.IE is None or ntabrx.IE == 0:
rawdata = ntabrx.sigma
else:
rawdata = np.empty(len(E_points), dtype='f8')
rawdata[:ntabrx.IE] = 0.0
rawdata[ntabrx.IE:] = ntabrx.sigma
if (E_g[0] <= E_g[-1] and E_points[-1] <= E_points[0]) or \
(E_g[0] >= E_g[-1] and E_points[-1] >= E_points[0]):
E_points = E_points[::-1]
rawdata = rawdata[::-1]
rxdata = bins.pointwise_linear_collapse(E_g, E_points, rawdata)
return rxdata
def self_shield(self, nuc, rx, temp, E_points, xs_points):
"""Calculates the self shielded cross section for a given nuclide
and reaction. This calculation uses the Bonderanko method.
Parameters
----------
nuc : int
Nuclide id.
rx : int
Reaction id.
temp : float, optional
The nuclide temperature in [K].
E_points : array like
The point wise energies.
xs_points : array like
Point wise cross sections
Returns
-------
rxdata : array like
collapsed self shielded cross section for nuclide nuc and reaction
rx
"""
sigb = self.bkg_xs(nuc, temp=temp)
e_n = self.src_group_struct
sig_b = np.ones(len(E_points), 'f8')
for n in range(len(sigb)):
sig_b[(e_n[n] <= E_points) & (E_points <= e_n[n + 1])] = sigb[n]
rtn = self.pointwise(nuc, 'total', temp)
if rtn is None:
sig_t = 0.0
else:
sig_t = rtn[1]
numer = bins.pointwise_linear_collapse(
self.src_group_struct, E_points,
xs_points / (E_points * (sig_b + sig_t)))
denom = bins.pointwise_linear_collapse(
self.src_group_struct, E_points,
1.0 / (E_points * (sig_b + sig_t)))
return numer / denom
def _load_reaction(self, nuc, rx, temp=300.0):
"""Loads reaction data from ACE files indexed by OpenMC.
Parameters
----------
nuc : int
Nuclide id.
rx : int
Reaction id.
temp : float, optional
The nuclide temperature in [K].
"""
rtn = self.pointwise(nuc, rx, temp=temp)
if rtn is None:
return
E_points, rawdata = rtn
E_g = self.src_group_struct
if self.atom_dens.get(
nuc, 0.0) > 1.0E19 and rx in self.self_shield_reactions:
rxdata = self.self_shield(nuc, rx, temp, E_points, rawdata)
else:
rxdata = bins.pointwise_linear_collapse(E_g, E_points, rawdata)
return rxdata
def check_pointwise_linear_collapse(x_g, x, y, exp):
obs = bins.pointwise_linear_collapse(x_g, x, y)
assert_equal(len(exp), len(obs))
assert_equal(len(x_g) - 1, len(obs))
assert_array_almost_equal(exp, obs)
def check_pointwise_linear_collapse(x_g, x, y, exp):
obs = bins.pointwise_linear_collapse(x_g, x, y)
assert_equal(len(exp), len(obs))
assert_equal(len(x_g) - 1, len(obs))
assert_array_almost_equal(exp, obs)