=====================
Decay Resource Format
=====================
The decay resource is a simple text format file that can be processed by
COUPLE to create a binary decay-only library that can be used directly
by ORIGEN. In general, this is not necessary, as the decay resource
distributed with SCALE has already been processed with COUPLE to produce
the end7dec ORIGEN decay-only binary library file. Modifying the decay
data or the set of nuclides ORIGEN tracks requires modification of the
decay resource file. The format is described in
:numref:`tab-origen-decay-resource`. Note that as of the SCALE 6.2 release,
ORIGEN now uses the SCALE Standard Composition resource for abundance data
and the "ABUND" field shown below is ignored by COUPLE when reading the decay
resource.
.. table:: Definitions of data in the decay resource
:class: longtable
:name: tab-origen-decay-resource
+---------------+-----------------------------------------------------+
| **Data name** | **Definition** |
+---------------+-----------------------------------------------------+
| LIB | Nuclide sublib (used by COUPLE) |
+---------------+-----------------------------------------------------+
| NUC1 | Nuclide identifier |
+---------------+-----------------------------------------------------+
| IU | Units for the half life value |
| | (see numref:`tab-origen-hl-units`) |
+---------------+-----------------------------------------------------+
| HALFL | Value of the half life in IU units |
+---------------+-----------------------------------------------------+
| FB1 | Beta decay transition leading to a daughter in the |
| | metastable state |
+---------------+-----------------------------------------------------+
| FP | Positron emission decay fraction or orbital |
| | electron capture to the ground state |
+---------------+-----------------------------------------------------+
| FP1 | Positron emission decay fraction or orbital |
| | electron capture to a metastable state |
+---------------+-----------------------------------------------------+
| FA | Alpha particle emission decay fraction |
+---------------+-----------------------------------------------------+
| FT | Isomeric transition decay fraction |
+---------------+-----------------------------------------------------+
| LIB1 | Nuclide type in the library |
+---------------+-----------------------------------------------------+
| FSF | Spontaneous fission decay fraction |
+---------------+-----------------------------------------------------+
| FBN | Delayed neutron decay (beta particle and a neutron) |
| | fraction |
+---------------+-----------------------------------------------------+
| Q | Recoverable energy per decay (MeV) |
+---------------+-----------------------------------------------------+
| ABUND | Natural atom isotopic abundance in percent |
| | (**no longer used**) |
+---------------+-----------------------------------------------------+
| AMPC | Maximum permissible concentration in air |
+---------------+-----------------------------------------------------+
| WMPC | Maximum permissible concentration in water |
+---------------+-----------------------------------------------------+
| LIB1 | Nuclide type in the library (used by COUPLE) |
+---------------+-----------------------------------------------------+
| FG | Fraction of recoverable decay energy Q associated |
| | with gamma rays |
+---------------+-----------------------------------------------------+
| FB | Beta decay transition leading to a daughter in the |
| | ground state |
+---------------+-----------------------------------------------------+
| FBB | Double beta decay fraction |
+---------------+-----------------------------------------------------+
| FN | Neutron decay fraction |
+---------------+-----------------------------------------------------+
| FBA | Beta decay plus an alpha particle emission decay |
| | fraction |
+---------------+-----------------------------------------------------+
The variable LIB (and LIB1)defines the nuclide sublibrary
(1/2/3=activation product/actinide/fission product). Variable LIB1 is
included for formatting purposes only.
The nuclide identifier is read in variable NUC1 and is subsequently
stored in array NUCL. The nuclide identifier is given by
.. math::
\text{NUCL} = \text{Z} * 10000 + \text{A} * 10 + \text{I}
:label: eq-origen-nuc-id
where Z is the atomic number, A is the atomic mass number, and I is the
isomeric state, where :math:`I=0` designates a ground state, and :math:`I=1`
is the first metastable state.
The variable HALFL is the physical half-life in units designated by the
variable IU, as shown in :numref:`tab-origen-hl-units`. The definitions of 11
variables representing the different decay mode branching fractions are given in
:numref:`tab-origen-decay-resource`. The decay branching fractions are used in
constructing the transition matrix.
.. table:: Units of half-life indicated by the variable IU
:name: tab-origen-hl-units
====== ======================
**IU** **Units of half-life**
1 seconds
2 minutes
3 hours
4 days
5 years
6 stable
7 10\ :sup:`3` years
8 10\ :sup:`6` years
9 10\ :sup:`9` years
====== ======================
The variable Q is the total amount of recoverable energy (MeV) per
disintegration released by radioactive decay used for decay heat
calculations. It does not include the energy of neutrinos emitted during
beta decay transitions. The variable FG is the fraction of recoverable
energy per disintegration that comes from gamma rays and x-rays.
The value of Q is obtained directly from ENDF/B-VII.1 as the sum of the
average beta, gamma, and alpha decay energy values. The quantity
includes the energy from all electron- related radiations such as :math:`\beta^-`,
:math:`\beta^+`, Auger electrons, etc., all gamma rays, x-rays, and annihilation
radiations, and the average energy of all heavy charged particles and
delayed neutrons. The contribution from alpha decay energy includes the
energy of the recoil nucleus. A part of the recoverable energy per decay
not included in the ENDF/B-VII.1 values is the additional contribution
from spontaneous fission. This energy was calculated as the product of
the spontaneous fission branching fraction and recoverable energy per
fission using a value of 200Â MeV per fission and added to the
ENDF/B-VII.1 recoverable Q energy. AÂ value of 12.56Â MeV gamma energy per
fission was used in computing the fraction of recoverable spontaneous
fission energy from gamma rays.
External bremsstrahlung radiation is **not** included in the values of
FG since the bremsstrahlung spectrum depends on electron interactions
with the medium that contains the decay nuclide. The energy from capture
gamma rays accompanying :math:`\left( \alpha,n \right)` reactions is also not included since it
also depends on the medium. The variable ABUND is the atom percent
abundance of naturally occurring isotopes.
An example of the decay resource content for selected fission products is
presented as :numref:`ex-dec-res-fp`.
.. literalinclude:: dec-fp.txt
:caption: Example of the ENDF/B-VII.1 decay data resource entries for selected fission products.
:name: ex-dec-res-fp
:language: none
=============================
Fission Yield Resource Format
=============================
The independent fission product yields are stored as a formatted text
file. The header record for each set of fission product yields includes
the fissionable nuclide ID and an unused entry (0.0), followed by the
number of incident neutron energies included for this nuclide. The
fission yields for each energy are preceeded by a single record
containing the incident neutron energy (eV), an unused entry (0.0), an
index for the incident energy, the number of data entries per fission
product, the total number of entries for each incident energy, and the
number of fission products. The fission product yields for each
fissionable nuclide and incident neutron energy are then listed as pairs
of entries for the fission product nuclide ID and the independent
(direct) fission yield as atom percent per fission. An example of the
format is shown below in :numref:`ex-origen-fy-th227` for :sup:`227`\ Th.
The number and order of the fission product yields must be the same for
all fissionable nuclides and must correspond to the fission products in
the nuclear decay data. The fission product yields for each fissionable
nuclide, excluding the yields for the terniary fission products
:sup:`3`\ H, :sup:`3`\ He, and :sup:`4`\ He, sum to 200.
The fissionable nuclides and the tabulated incident neutron energies for
which yields are available are listed in :numref:`tab-origen-fiss-isotopes`.
.. literalinclude:: fy-th227.txt
:caption: Fission yield format example showing a portion of :sup:`227`\ Th.
:name: ex-origen-fy-th227
:language: none
=====================
Gamma Resource Format
=====================
An example of the photon data entries for the emissions from
:sup:`140`\ La decay is shown below in :numref:`ex-origen-dec-la140`. The header
record for each nuclide contains the nuclide ID, the total number of emission
lines in the evaluation, as well as the number of discrete x-ray lines,
discrete gamma lines, and number of pseudo lines used to represent
continuum data if present in an evaluation used to reconstruct
continuous energy emission spectra from the discrete representation. The
last entries in the header record include the total gamma energy (MeV),
and the character nuclide name. The emission spectrum is listed using
pairs of entries for the photon energy (MeV) and photon emission
(photons per disintegration).
.. literalinclude:: gam-la140.txt
:caption: Gamma resource format example showing :sup:`140`\ La decay photon
emission.
:name: ex-origen-dec-la140
:language: none