Specifies parameters for radioactive decay reaction. This reaction differs from the GENERAL_REACTION in that only one reactant species may be specified with a unit stoichiometry (i.e. the rate is always first order) and the reactant species is decayed in both the aqueous and sorbed phases.
- REACTION <string>
- Reaction equation. Only one reactant species may be listed on the left side of the equation (i.e. or on the right side with a negative stoichiometry). The reactant's stoichiometry is fixed at 1.0. The forward rate is applied to that one species as a first order rate constant [1/sec]. Multiple species are supported as daughter products on the right hand side and stoichiometries can be specified.
RATE_CONSTANT or HALF_LIFE (but not both)
- RATE_CONSTANT <float>
- rate constant for 1st-order decay reaction [1/sec]. The rate constant may be calculated from -ln(0.5) / half-life
- HALF_LIFE <float>
- half life of species [sec].
Note that rate constant or half life units other than sec or 1/sec may be specified.
RADIOACTIVE_DECAY_REACTION REACTION Tracer <-> Tracer2 RATE_CONSTANT 1.7584d-7 ! half life at 0.125 y /CHEMISTRY PRIMARY_SPECIES A(aq) B(aq) C(aq) / ... RADIOACTIVE_DECAY_REACTION REACTION A(aq) <-> B(aq) ! Calculating forward rate from half-life ! rate = -ln(0.5) / half-life [1/sec] RATE_CONSTANT 1.75836d-9 ! 1/s half life = 12.5 yrs / RADIOACTIVE_DECAY_REACTION REACTION B(aq) <-> C(aq) RATE_CONSTANT 8.7918d-10 ! 1/s half life = 25. yrs / RADIOACTIVE_DECAY_REACTION ! Note that C(aq) simply decays with no daughter products REACTION C(aq) <-> HALF_LIFE 5. y / ... /