Maxwellian Average :
σmacs(T) =
2
 
√  
π
∫
EU
 
EL
 σ(E,T) ⋅ E ⋅ exp (
E
  
kBT
 ) dE
 
∫
EU
 
EL
 E ⋅ exp (
E
  
kBT
 ) dE
,
where T denotes the temperature, and kB the Boltzmann constant. The upper and lower limits of integration, EL and EU are set to 10−5 eV and 10 eV, respectively.
Resonance Integral :
σri(T) = ∫
EU
 
EL
 σ(E,T) ⋅
1
 
E
 dE ,
with  EL = 0.5 eV  and  EU = 10 MeV.
U-235 Thermal Fission-Neutron Spectrum Average (Fiss. Spec. Average) :
σfacs(T) =
∫
EU
 
EL
 σ(E,T) ⋅
√  
4
 
πa3b
⋅ exp (
ab E
     
4 a
 ) ⋅ sinh
√  
bE
 dE
 
∫
EU
 
EL
√  
4
 
πa3b
⋅ exp (
ab E
     
4 a
 ) ⋅ sinh
√  
bE
 dE
,
with  EL = 10−5 eV  and  EU = 20 MeV. The parameters a and b are 0.988 MeV and 2.249 MeV−1, respectively. The fission spectrum is based on Watt's formula (Phys. Rev. 87, 1041 (1952)).
Westcott g-factor :
g(T) =
σmacs(T)
 
σ(0.0253 eV,T)
  .
νp, νd : numbers of prompt and delayed neutrons per fission.