Required Cards:

MECHANISM <type_string>

The mechanism block specifies a waste form mechanism. The mechanism includes the details of the radionuclide species, the waste form bulk material details, and the canister that contains the waste form. Several different custom mechanisms can be defined, or chosen from pre-defined options. Each mechanism is given a unique name, and later associated with specific listed waste forms. The following types are currently supported: GLASS, DSNF, FMDM, CUSTOM.

MECHANISM GLASS
/

Within the MECHANISM block, the following sub-blocks and cards can be included:

NAME <name_string> (required for all mechanism types)

Specifies a name for the mechanism. This name should be unique.

NAME glass02

SPECIES sub-block (required for all mechanism types)

Specifies a list of waste form species, their formula weights (in units of g-species/mol-species), decay constant (in units of 1/sec), initial mass fraction within the waste form matrix (g-species/g-bulk), instant release fraction (a number between 0 and 1), and the name of the species daughter (if it exists). The species listed here must also be listed in the CHEMISTRY block under Primary Species. Isotopes decay and ingrowth occurs following a 3-generation analytical solution derived for multiple parents and grandparents and non-zero initial daughter concentrations.

SPECIES
 I-129   128.90d0 1.29d-15  2.18d-4  0.7d0
 Am-241  241.06d0 5.08d-11  8.70d-4  0.0d0  Np-237
 Np-237  237.05d0 1.03d-14  8.59d-4  0.7d0  U-233
 U-233   233.04d0 1.38d-13  9.70d-9  0.0d0  Th-229
 Th-229  229.03d0 2.78d-12  4.43d-12 0.0d0
  ...      ...      ...        ...    ...     ...
/

SPECIFIC_SURFACE_AREA <double> <unit_string> (required for types GLASS, FMDM; semi-optional for type CUSTOM; do not include for type DSNF)

Specifies the specific surface area of the waste form bulk (or matrix). If specific surface area is given for the CUSTOM mechanism type, the DISSOLUTION_RATE keyword must also be specified (see below).

SPECIFIC_SURFACE_AREA 2.78d-3 cm^2/g

DISSOLUTION_RATE <double> <unit_string> (semi-optional for type CUSTOM; do not include for type GLASS, DSNF, FMDM)

Specifies the dissolution rate for the waste form bulk (or matrix), in units of mass per surface area per time. If dissolution rate is given for the CUSTOM mechanism type, the SPECIFIC_SURFACE_AREA must also be specified (see above).

DISSOLUTION_RATE 7.8d-8 kg/m^2-day

FRACTIONAL_DISSOLUTION_RATE <double> <unit_string> (semi-optional for type CUSTOM; do not include for types GLASS, DSNF, FMDM)

Specifies the fractional dissolution rate for the waste form bulk (or matrix), in units of fractional volume per time. The unit string should resemble 1/time. For type DSNF, a fractional dissolution rate of 1.0d0/day is assumed.

FRACTIONAL_DISSOLUTION_RATE 3.4d-8 1/day

MATRIX_DENSITY <double> <unit_string> (required for all mechanism types)

Specifies the density of the waste form bulk (or matrix).

MATRIX_DENSITY 2.0d3 kg/m^3

CANISTER_DEGRADATION_MODEL sub-block (optional for all mechanism types)

If this optional block is included, the canister degradation model will be turned on. Currently, this model will keep track of canister vitality, a parameter which controls the time of waste form breach. At the beginning of the simulation, vitality = 1. Waste form breach occurs when the canister vitality falls to zero. The reference vitality degradation rate (Rv0) is either (a) chosen at the beginning of the simulation, for each waste form, based on a normal distribution of degradation rates, (b) specified for each waste form by the user, or (c) ignored if the user specifies a canister breach time for each waste form instead of a rate. The effective vitality degradation rate (Rv) is calculated as an Arrhenius function of temperature, canister material constant (C), and the reference vitality degradation rate:

ln(Rv) = ln(Rv0) + C * (1/333.15[K] - 1/T[K])

If option "a" is desired, the normal distribution for the reference rate is formed by providing the following block keywords (all required):

VITALITY_LOG10_MEAN

Specifies the Log(base10) mean vitality degradation rate (in units of log10-1/yr). If this distribution parameter is omitted, then CANISTER_VITALITY_RATE must be included for all waste forms associated with this mechanism.

VITALITY_LOG10_STDEV

Specifies the Log(base10) standard deviation of the vitality degradation rate (in units of log10-1/yr). If this distribution parameter is omitted, then CANISTER_VITALITY_RATE must be included for all waste forms associated with this mechanism.

VITALITY_UPPER_TRUNCATION

Specifies the Log(base10) upper truncation of the mean vitality degradation rate (in units of log10-1/yr). If this distribution parameter is omitted, then CANISTER_VITALITY_RATE must be included for all waste forms associated with this mechanism.

CANISTER_MATERIAL_CONSTANT

Specifies the canister material constant (ex: 1500 for 316L stainless steel).

CANISTER_DEGRADATION_MODEL
  VITALITY_LOG10_MEAN -4.5
  VITALITY_LOG10_STDEV 0.5
  VITALITY_UPPER_TRUNCATION -3.0
  CANISTER_MATERIAL_CONSTANT 1500
/

Full examples of the MECHANISM sub-block:

MECHANISM GLASS
  NAME glass02
  SPECIFIC_SURFACE_AREA 2.78d-3 m^2/kg
  MATRIX_DENSITY 2.0d3 kg/m^3
  SPECIES
   #name,   MW[g/mol],dcy[1/s], initMF, inst_rel_frac,daughter
    I-129   128.90d0  1.29d-15  2.18d-4   0.2d0
    Am-241  241.06d0  5.08d-11  8.70d-4   0.0d0
    Np-237  237.05d0  1.03d-14  8.59d-4   0.2d0  Am-241
    U-233   233.04d0  1.38d-13  9.70d-9   0.0d0  Np-237
    Th-229  229.03d0  2.78d-12  4.43d-12  0.0d0  U-233
  /
  CANISTER_DEGRADATION_MODEL
    VITALITY_LOG10_MEAN -3.5
    VITALITY_LOG10_STDEV 1.5
    VITALITY_UPPER_TRUNCATION -2.75
    CANISTER_MATERIAL_CONSTANT 1500.0
  /
/

MECHANISM DSNF
  NAME dsnf01
  MATRIX_DENSITY 3.56d3 kg/m^3
  SPECIES
   #name,   MW[g/mol],dcy[1/s], initMF, inst_rel_frac,daughter
    Am-243  243.06d0  2.98d-12  1.12d-5  0.0d0
    Th-230  230.03d0  2.75d-13  2.45d-8  0.0d0
  /
  CANISTER_DEGRADATION_MODEL
    VITALITY_LOG10_MEAN -3.2
    VITALITY_LOG10_STDEV 0.75
    VITALITY_UPPER_TRUNCATION -2.0
    CANISTER_MATERIAL_CONSTANT 1200.0
  /
/

MECHANISM CUSTOM
  NAME custom05
  FRACTIONAL_DISSOLUTION_RATE 2.0d-9 1/day
  MATRIX_DENSITY 2.44d3 kg/m^3
  SPECIES
   #name,   MW[g/mol],dcy[1/s], initMF, inst_rel_frac,daughter
    Pu-240  240.05d0  3.34d-12  2.84d-3  0.2d0
    U-236   236.05d0  9.20d-16  4.33d-3  0.0d0  Pu-240
    Tc-99   98.91d0   1.04d-13  8.87d-4  0.0d0
  /
  CANISTER_DEGRADATION_MODEL
    CANISTER_MATERIAL_CONSTANT 1500.0
  /
/

MECHANISM CUSTOM
  NAME custom03
  DISSOLUTION_RATE 4.1d-8 kg/m^2-day
  SPECIFIC_SURFACE_AREA 2.11d-3 m^2/kg
  MATRIX_DENSITY 2.44d3 kg/m^3
  SPECIES
   #name,   MW[g/mol],dcy[1/s], initMF, inst_rel_frac,daughter
    Pu-240  240.05d0  3.34d-12  2.84d-3  0.2d0
    U-236   236.05d0  9.20d-16  4.33d-3  0.0d0  Pu-240
    Tc-99   98.91d0   1.04d-13  8.87d-4  0.0d0
  /
  CANISTER_DEGRADATION_MODEL
    VITALITY_LOG10_MEAN -3.5
    VITALITY_LOG10_STDEV 0.5
    VITALITY_UPPER_TRUNCATION -2.75
    CANISTER_MATERIAL_CONSTANT 1500.0
  /
/

  MECHANISM FMDM
    NAME fmdm02
    MATRIX_DENSITY 10.97d3 kg/m^3
    BURNUP 60 #MWd/MTHM
    SPECIFIC_SURFACE_AREA 0.001 m^2/g
    SPECIES
     #name,   MW[g/mol],dcy[1/s], initMF, inst_rel_frac,daughter
      Uranium 238.02d0  1.00d-90  0.50d0  0.0d0
    /
    CANISTER_DEGRADATION_MODEL
      CANISTER_MATERIAL_CONSTANT 1500.0
    /
  /

WASTE_FORM sub-block

Specifies the details of each waste form. This block should be repeated for each waste form, and can include the following cards:

COORDINATE <double> <double> <double> -or- REGION <string>

If COORDINATE, <double> <double> <double> gives the location of each waste form in x, y, z. Waste forms can be co-located (i.e., there can be multiple waste forms located at the same coordinate point. If REGION, <string> gives the name of a defined region that the waste form occupies. The source term will be released over the cells of the REGION, or the single cell of the COORDINATE. Note that REGION and COORDINATE can't be given, only one is allowed.

EXPOSURE_FACTOR <double> (optional)

Gives the exposure factor of each waste form, which is a multiplier to the waste form dissolution rate. If this keyword is not specified, the default value is 1.

VOLUME <double> <unit_string>

Gives the volume of each waste form.

MECHANISM_NAME <string>

Specifies the name of the mechanism associated with the waste form. The mechanism name given here must match one of the mechanisms defined in the MECHANISM sub-block(s).

CANISTER_VITALITY_RATE <double> <unit_string> (optional)

Specifies the waste form canister's vitality degradation rate in units of 1/time. If this parameter is specified, the mechanism associated to this waste form must include the CANISTER_DEGRADATION_BLOCK, but without the distribution parameters (e.g. VITALITY_LOG10_MEAN, VITALITY_LOG10_STDEV, and VITALITY_UPPER_TRUNCATION). This option cannot be combined with CANISTER_BREACH_TIME for a single waste form, but both CANISTER_BREACH_TIME and CANISTER_VITALITY_RATE can be combined for different waste forms under the same mechanism which omits the distribution parameters.

CANISTER_BREACH_TIME <double> <unit_string> (optional)

Specifies the waste form canister's breach time in units of time. The canister will breach during the next timestep where time > CANISTER_BREACH_TIME. If this parameter is specified, the mechanism associated to this waste form must include the CANISTER_DEGRADATION_BLOCK, but without the distribution parameters (e.g. VITALITY_LOG10_MEAN, VITALITY_LOG10_STDEV, and VITALITY_UPPER_TRUNCATION). This option cannot be combined with CANISTER_VITALITY_RATE for a single waste form, but both CANISTER_BREACH_TIME and CANISTER_VITALITY_RATE can be combined for different waste forms under the same mechanism which omits the distribution parameters.

WASTE_FORM
  COORDINATE 0.5d0 4.5d0 0.5d0
  EXPOSURE_FACTOR 4.d0
  VOLUME 1.14d0 m^3
  MECHANISM_NAME glass02
/

WASTE_FORM
  REGION WF-a1
  VOLUME 2.1d0 m^3
  CANISTER_BREACH_TIME 250 yr
  MECHANISM_NAME custom01
/

WASTE_FORM
  REGION WF-3b
  VOLUME 0.55d0 m^3
  CANISTER_VITALITY_RATE 1.0d-7 1/yr
  MECHANISM_NAME custom01
/

Optional Cards:

PRINT_MASS_BALANCE

If this option is included, output will be generated at each timestep that the waste form process model is called. The output includes the cumulative mass and instantaneous mass rate for each species in each waste form, the volume, dissolution rate, and the canister vitality of each waste form.

Full Example:

The following example specifies several waste forms, each associated with one of two particular mechanisms. Output will be generated for each waste form.

WASTE_FORM_GENERAL

  PRINT_MASS_BALANCE
  MECHANISM FMDM
    NAME fmdm01
    MATRIX_DENSITY 10.97d3 kg/m^3
    BURNUP 60 #MWd/MTHM
    SPECIFIC_SURFACE_AREA 0.001 m^2/g
    SPECIES
     #name,   MW[g/mol],dcy[1/s], initMF, inst_rel_frac,daughter
      Uranium 238.02d0  1.00d-90  0.50d0  0.0d0
    /
    CANISTER_DEGRADATION_MODEL
      VITALITY_LOG10_MEAN -3.2
      VITALITY_LOG10_STDEV 0.75
      VITALITY_UPPER_TRUNCATION -2.0
      CANISTER_MATERIAL_CONSTANT 1200.0
    /
  /
  MECHANISM CUSTOM
    NAME custom05
    FRACTIONAL_DISSOLUTION_RATE 2.0d-9 1/day
    MATRIX_DENSITY 2.44d3 kg/m^3
    SPECIES
     #name,   MW[g/mol],dcy[1/s], initMF, inst_rel_frac,daughter
      Pu-240  240.05d0  3.34d-12  2.84d-3  0.2d0
      U-236   236.05d0  9.20d-16  4.33d-3  0.0d0  Pu-240
      Tc-99   98.91d0   1.04d-13  8.87d-4  0.0d0
    /
    CANISTER_DEGRADATION_MODEL
      CANISTER_MATERIAL_CONSTANT 1500.0
    /
  /
  WASTE_FORM
    REGION WF-custom-1
    EXPOSURE_FACTOR 3.d0
    VOLUME 1.14d0 m^3
    MECHANISM_NAME custom05
    CANISTER_BREACH_TIME 375 yr
  /
  WASTE_FORM
    REGION WF-custom-2
    EXPOSURE_FACTOR 4.d0
    VOLUME 1.14d0 m^3
    MECHANISM_NAME custom05
    CANISTER_VITALITY_RATE 3.d-6 1/day
  /
  WASTE_FORM
    COORDINATE 12.5d0 55.5d0 0.5d0
    VOLUME 1.55d0 m^3
    MECHANISM_NAME fmdm01
  /
  WASTE_FORM
    COORDINATE 5.5d0 4.5d0 0.5d0
    VOLUME 1.55d0 m^3
    MECHANISM_NAME fmdm01
  /

END_WASTE_FORM_GENERAL