A new method for improving critical extrapolation

The divergent phenomenon of critical extrapolation and ρ–1/N extrapolation curve is analyzed during the physical startup of a reactor. Aiming at the deficiency of the existing improving method—constant neutron source elimination (CNSE) method, a new method—variable neutron source elimination (VNSE) is proposed. This new method aims at getting accurate neutron count rate for extrapolation, and considers all the errors caused by the neutron source leakage, reactor spatial effect and neutron detector positions as a whole. Applied to a small reactor, this VNSE method can remove all errors and eliminate the divergence of extrapolation so that the accurate ρ–1/N extrapolation curve is got. The VNSE method is efficient and accurate for the critical extrapolation.

► A new method—variable neutron source elimination (VNSE) is proposed.
► VNSE considers all the errors caused by the neutron source leakage, reactor spatial effect and neutron detector positions.
► VNSE method can eliminate the divergence of extrapolation in a small reactor.
► VNSE method is efficient and accurate for the critical extrapolation.