What Is the Nuclear Fission Xenon-135 Equilibrium Poisoning Calculator?
Xenon-135 poisoning is the accumulation of an intense neutron-absorbing fission product that penalizes core reactivity.
How Does the Nuclear Fission Xenon-135 Equilibrium Poisoning Calculator Work?
Xenon-135 is formed directly in fission and via beta decay of Iodine-135, burned out by neutron absorption and radioactively decaying with a 9.2-hour half-life.
Nuclear Fission Xenon-135 Equilibrium Poisoning Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
N_{\text{Xe}} = \frac{(\gamma_I + \gamma_{\text{Xe}})\Sigma_f \phi}{\lambda_{\text{Xe}} + \sigma_{\text{Xe}} \phi}, \quad \rho_{\text{Xe}} = -\frac{N_{\text{Xe}} \sigma_{\text{Xe}}}{\Sigma_f}
Equilibrium Xenon-135 concentration and negative reactivity insertion.
How to Use the Nuclear Fission Xenon-135 Equilibrium Poisoning Calculator
- Input thermal neutron flux and macroscopic fission cross section.
Step-by-Step Example Calculation
Commercial PWR Full Power Equilibrium
Input Values:
thermalNeutronFluxNPerCm2S:100000000000000
fissionCrossSectionCmMinus1:0.1
iodineFissionYieldGammaI:0.061
xenonFissionYieldGammaXe:0.003
Worked Steps: Predicts equilibrium Xe-135 concentration of ~2.28×10¹² atoms/cm³ producing -5,939 pcm negative reactivity.
Understanding Your Result
Outputs equilibrium Xe-135 and I-135 densities and total negative reactivity penalty in pcm.
Factors That Affect the Result
- Higher flux burns out xenon faster during steady operation, but creates a massive Iodine-135 inventory that causes the post-shutdown "xenon pit".
When Should You Use This Calculator?
- Nuclear plant power maneuvering, load following schedules, and post-trip restart windows.
Assumptions & Limitations
- Applies to steady-state equilibrium at constant thermal flux.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard point reactor poison kinetics formulation.