5.1.9.4. COUPLE Module

Warning

COUPLE is deprecated as of SCALE 6.3 with the ORIGEN build_lib capability replacing it. All of the capabilities of COUPLE are available and more. The legacy FIDO COUPLE input described here is still supported but a completely new computational engine is used to create the library, the same as is used for the build_lib block. See Sect. 5.1.5.2.12 for details.

COUPLE is a coupling code that prepares the transition matrix A from Eq. (5.1.2), which contains the decay and cross section transition rate constants according to the procedures defined in Sect. 5.1.3.1.1. The transition matrix and other important data are stored on an ORIGEN library (f33) file for use by other modules. COUPLE has two distinct modes of operation:

1. to create a new decay-only ORIGEN library from an ORIGEN decay resource, and

2. to add new or to update existing reaction transitions yield resource, reaction resource, and optionally an AMPX working library containing multigroup cross sections.

Details on the decay, yield, and reaction resources may be found in the ORIGEN Data Resources chapter.

5.1.9.4.1. Key Features

This section briefly highlights some key features in COUPLE and describes how they are used.

5.1.9.4.1.1. AMPX multi-group libraries

AMPX multigroup libraries contain multigroup cross sections by nuclide and material-zone identifiers. If the working library is the result of a multiregion transport calculation, then it is important to specify the correct zone identifier, e.g. corresponding to the fuel in a problem with moderator, clad, and fuel zones. The neutron flux is also stored on the AMPX library associated with a nuclide and a zone as are the cross sections. An AMPX library flux can be used to perform the cross section collapse as an alternative to providing a flux spectrum in the COUPLE input. New transitions may be added to the ORIGEN binary library for all reactions for which there are data in the weighted AMPX library if both the target and product nuclides are present in the ORIGEN library.

5.1.9.4.1.2. Nuclide Specification

In COUPLE, the following nuclide identifier is used:

Nuclide identifier = Z * 10000 + A * 10 + I

where

Z = atomic number,

A = mass number,

I = metastable/isomeric state (0 is ground/1 is first metastable)

Examples include 922350 for ²³⁵U and 952421 for ^242mAm. Note that this varies from the identifiers used in other ORIGEN-related modules in which the isomeric state I comes first, as in 1095242 for ^242mAm.

5.1.9.4.1.3. Adding new transitions and user-defined transitions

The use of a transition matrix in ORIGEN allows any nuclide to transition to any other nuclide. By default, when the reaction data on the library is updated, then the transition matrix’s sparse storage is expanded to include the new reaction transition if both the target and the reaction product nuclide are in the library. The user may request that the code does not add new transitions by setting Block1 JADD=0 (1$$ a4 0). This option ensures that the matrix structure on the input library is identical to that of the output library. The user may explicitly set one-group transition coefficients by setting Block1 LBUP=1 (1$$ a3 1) and entering Block6 and Block8 data.

5.1.9.4.1.4. Unit numbers and Aliases

In COUPLE, a unit number is used instead of a full file name to specify files, where unit number XY links to the data file “ftXYf001” in the working directory. For example, unit number 33 means file ft33f001. There are several predefined unit numbers that are controlled by a special “origen_filenames” file, which creates an alias for the local file “ftXYf001” to a file in the data directory. Table 5.1.20 shows the basic COUPLE unit numbers, their aliases, and a description of the file.

Table 5.1.20 Basic COUPLE unit numbers

Unit	Alias	Description
17	YIELDS	ORIGEN Yield Resource
21	END7DEC	ORIGEN library ENDF/B-VII-based decay transitions only
27	DECAY	ORIGEN Decay Resource
80	JEFF252G	ORIGEN Reaction Resource (252 groups)

An “origen_filenames” list which maps unit number 21 to alias “END7DEC” could link unit 21 to the file “${DATA}/origen.rev04.end7dec,” where ${DATA} is the path to the SCALE data directory. To override this association, COUPLE must find a file named “ft21f001” in the working directory. The entire set of unit numbers is given in the ORIGEN Data Resources chapter.

5.1.9.4.2. Input Description

COUPLE uses the FIDO input system, except for title entries. The input is arranged in blocks, with each block containing one or more arrays, followed by the FIDO block terminator “t.” Each input parameter is named and defined below in the order in which it appears, with the index of the parameter in the array. Some options have been deprecated over time and thus the first available entry may not correspond to index “1” and some indices may be skipped. Default values are given in parentheses. In the SCALE code system, COUPLE input appears between “=couple” and “end.”

5.1.9.4.2.1. Block1: titles, unit numbers, and case controls.

TITLE — Title lines

Title lines can provide information about the ORIGEN library created and printed when the library is used. The input Block1 1\$\$ NUMA allows title lines to be copied from the input library to the output library.

The first blank line terminates the title.

A maximum of 40 lines can be included in the library.

A special title of “DONE” in the first four columns marks the completion of a COUPLE input case.

0\$\$ Array – Logical Unit Assignments

1. NOUT – Printed output unit number (6)

2. LIBDEC – Unit number of ORIGEN decay resource (27)

Only used if 1\$\$ LBIN=1

3. JD – Unit number of ORIGEN reaction resource (80)

4. ND – Input ORIGEN binary library file (21)

Only used if 1\$\$ LBIN=0

5. LD – Unit number of AMPX multigroup library file (0)

Only used if LD>0; energy group structure must be consistent with that on ORIGEN reaction resource (JD)

6. MD – Unit number for output ORIGEN library file (33)

8. NY – Unit number of ORIGEN yield resource (17)

1\$\$ Array – Control Constants [19 entries]

1. LBIN – 1/0 – Decay library creation/reaction update mode (0)

In decay library creation mode with LBIN=1, the reaction resource (0\$\$ JD) is not used, any input associated with reaction processing is ignored, and Block2 and Block8 may not be entered. In reaction update mode with LBIN=0, Block3 may not be entered.

2. PRT – 1/0 – Suppress all informational output / print informational output (0).

3. LBUP – 1/0 – Update from user input cross sections (Block6 and Block8 Arrays) / no user update (0).

4. JADD – 1/0 – Add/do not add new transitions to the library (1).

5. JEDT – 1/0 – Edit input library only/normal library generation case (0).

6. NXX – 1/0 – Allow/do not allow transitions with zero cross section (0).

7. NMO – Current month (as integer) for output library (0).

8. NDAY – Current day for output library (0).

9. NYR – Current year for output library (two digits) (0).

12. IDREF – Nuclide ID in AMPX multigroup library (0\$\$ LD) containing neutron flux weighting spectrum to use in cross section collapse (0).

If IDREF=0, uses first nuclide found in NZONE. Only used if NWGT=0.

13. NZONE – Zone ID (usually a mixture ID) in AMPX multigroup library (0\$\$ LD)

from which to add/update transitions (0).

If NZONE=0, the AMPX library must not contain zone IDs.

14. IEDOU – 1/0 – Edit/no edit of transition cross sections (0)

15. NFISW – Number of nuclides with fission yields (-1)

-1 fission yields included for all fissionable nuclides

0 no yields added

N input N nuclides with fission yields (Block2 7\$\$ Array)

16. NUMA – Number of title lines to copy from the input ORIGEN library (0\$\$ ND) to the output ORIGEN library (0\$\$ MD) (0).

18. NWGT – Flux spectrum source (0).

0 flux spectrum from AMPX multigroup library (IDREF)

N input N-group flux spectrum (Block2, 9** Array)

T – Block1 terminator.

5.1.9.4.2.2. Block2: nuclides with fission yields and weighting flux spectrum

This block is only read if in reaction update mode (Block1 0\\$\\$ LBIN=0).

7\$\$ Array – Nuclide IDs with fission yields [Block1 1\$\$ NFISW entries]

9** Array – Weighting flux spectrum [Block1 1\$\$ NWGT entries]

The flux spectrum must be given in order of descending neutron energy according to the convention that group 1 is the highest energy group. The group structure (number of groups and group boundaries) must be consistent with the ORIGEN reaction resource (Block1 0\$\$ JD).

T – Block2 terminator.

5.1.9.4.2.3. Block3: array dimensions for decay library creation

This block is only read if in decay library creation mode (Block1 0\$\$ LBIN=1). The default values usually apply. The values are used only internally for memory allocation and may be set to a larger value than is required.

3\$\$ Array – Library constants

18. ITMAX – Total number of nuclides in library (2600)

19. ILMAX – Number of activation product nuclides (1000)

-1, omits light-element library

20. IAMAX – Number of actinide nuclides (200)

-1, omits actinide library

21. IFMAX ––Number of fission-product nuclides (1400)

-1, omits fission-product library

22. IXMAX – Total number of decay transitions from one nuclide to another (40,000)

T – Block3 terminator.

5.1.9.4.2.4. Block6: number of user-defined transition coefficients

This block is only read if user-defined transition coefficients have been specified in decay library creation mode (Block1 1\$\$ LBUP=1).

15\$\$ Array – Number of user update nuclides

1. LBU – Total number of transitions to be entered in Block8 71\$\$, 72\$\$, and 73** Arrays (0)

T – Block6 terminator

5.1.9.4.2.5. Block8: user-defined transition coefficients

Block8 is only required only if a nonzero value is entered in the Block6 15\$\$ array. The three arrays (71\$\$, 72\$\$, and 73**) represent the parent, daughter, and coefficients for Block6 LBU user-defined transitions, or the quantity \(f_{\text{ij}}\sigma_{j}\) for a given parent j and daughter i from Eq. (5.1.4).

71\$\$ Array – Parent Nuclides [LBU entries]

ISN1 – Parent Nuclide ID

72\$\$ Array – Daughter Nuclides or Reaction MT number [LBU entries]

ISN2 – Daughter Nuclide ID for the reaction product of the corresponding entry in ISN1

or reaction MT number

Note

The reaction transition will be added if it does not already exist by setting Block1 1$$ JADD=1. Otherwise, new transitions are omitted.

73** Array – Reaction Cross Sections [LBU entries].

SIGMA– Reaction cross section (in barns) for the reaction described by ISN1 and ISN2

There are two special rules to facilitate modifying fission cross sections \(\sigma_{\text{fj}}\) and removal cross sections \(\sigma_{j}\).

if ISN1=ISN2, the removal cross section is set equal to the corresponding SIGMA. Note that this overrides the automatic calculation of the removal cross section as the sum of all transition cross sections.

if ISN1=-ISN2, the fission cross section is set equal to the corresponding SIGMA.

T -Block8 terminator.

This concludes the input for a single case in COUPLE. COUPLE allows for multiple cases in a single input and will automatically begin processing the next case’s Block1 TITLE unless “DONE” (without quotes) is entered as the TITLE entry.