Averaging of constants in the B2 approximation for reactor calculation

Analytical derivation of a formula for determining the effec-- tive neutron multiplication factor Ksub(eff) in the B2 approximation using the methods of averaging over neutron spectrum and taking into account the neutron importance is given. Dependence of averaged reactor core constants on the value of the geometric parameter B2 is studied. It is shown that the averaging of reactor core constants when using the B2 approximation doesn't cause the change in Ksub(eff). The averaging of constants over neutron spectrum with neutron importance account for and without it gives the same Ksub(eff) value. The core constants averaged over neutron spectrum de- pend less on B2 value as compared with corresponding values ob- tained with the averaging taking into account the neutron impor- tance value. Considerable dependence of reflector albedo on the me- thod of constant averaging is discovered