modelXenon
xenon as fission product
Information
# Xenon Evolution
The Xenon evolution follows the following Bateman equations:
$$ \frac{dI^{135}}{dt} = FissionRate * \gamma_I - I^{135} \lambda_I $$
$$ \frac{dXe^{135}}{dt} = FissionRate * \gamma_{Xe} + I^{135} \lambda_I - Xe^{135} \lambda_{Xe} - \Phi_{Th} Xe^{135} \sigma_{Xe} $$
where \\(\gamma\\) is the fission yield, \\(\lambda\\) the decay constant, \\(\Phi_{Th}\\) the thermal neutron flux
and \\(\sigma_{Xe}\\) the microscopic absorption cross section of the Xenon.
The *FissionRate* is computed from the thermal power:
$$ Power / Vfuel = FissionEnergy * FissionRate $$
and \\(\Phi_{Th}\\) from the *FissionRate*, taking into account a small amount of fast fissions:
$$ FissionRate = FastFissionFactor * \Phi_{Th} * \sigma_f * N_f $$
where *FastFissionFactor* is the ratio between the total number of fissions and the thermal ones, \\(\sigma_f\\) the microscopic fission cross-section of the fuel
and \\(N_f\\) the density of fissil atoms in the fuel.
The used microscopic cross-section values should refer to the thermal neutron flux.
## Copyright © EDF 2002 - 2026
## ThermoSysPro Version 4.2
Parameters
| Type | Name | Default | Description |
|---|
| Real | pi | Modelica.Constants.pi | pi |
| Real | OAtomicMass | 15.9949 | Oxygen atomic mass |
| Initialization |
| Boolean | steady_state | true | Steady-state (true) or fixed values (false) initialization |
| Real | Xe_start | 0 | Initial concentration of Xenon (if steady_state=false) |
| Real | I_start | 0 | Initial concentration of Iode (if steady_state=false) |
| Fuel Properties |
| ThermoSysPro.Units.SI.Density | FuelDensity | 10950 | Fuel Density |
| Real | Enrichment | 0.02433 | Fuel enrichement |
| Fuel Volume |
| ThermoSysPro.Units.SI.Radius | Rp | 0.004095 | Radius of the fuel pellet |
| ThermoSysPro.Units.SI.Length | Length | 4.270 | Active lenght of the fuel rods |
| Integer | Rods_per_FA | 264 | Number of fuel Rods per Fuel Assembly |
| Integer | FA | 193 | Number of Fuel Assemblies |
| Nuclear Data |
| ThermoSysPro.Units.SI.Frequency | I_decay | 2.913e-5 | Decay constant of 135Iode |
| ThermoSysPro.Units.SI.Frequency | Xe_decay | 2.116e-5 | Decay constant of 135Xenon |
| Real | FastFissionFactor | 1.07 | Fast Fission Factor |
| ThermoSysPro.Units.SI.Area | Fuel_Fission_CS | 5.82e-26 | Fuel thermal microscopic fission cross-section |
| ThermoSysPro.Units.SI.Energy | FissionEnergy | 3.2e-11 | Energy from each fission |
| Real | FAtomicMass | 235.04393 | Fissil atomic mass |
| Real | I_yield | 0.0632 | Total fission yield of 135Iode |
| Real | Xe_yield | 0.0026 | Total fission yield of 135Xenon |
| ThermoSysPro.Units.SI.Area | Xe_abs_CS | 2.75e-22 | Microscopic absorption cross-section of 135Xenon |