Investigation of the validity of the point-kinetic approximation and of the break-frequency method in 2-D subcritical systems
Paper in proceedings, 2007

The accuracy and applicability of the break-frequency method for estimating the reactivity in a subcritical 2-D, 2-group reflected system with a distributed source is investigated for two different system sizes. The source is distributed according to the static thermal flux. This method could be useful in power reactor cores during loading conditions for determining the subcriticality. The validity of the point-kinetic approximation in the same systems is also tested. A neutron noise simulator is used to calculate the actual neutron noise induced by fluctuations of the source which is compared with the analytically calculated point-kinetic term. The break-frequency method is used to estimate the reactivity from the neutron noise calculated by the simulator. The conclusion of this work is that the point-kinetic approximation in general is not valid in 2-D, 2-group reflected systems and hence the break-frequency method is not valid either.



reflected system


subcritical system


Carl Sunde

Chalmers, Applied Physics, Nuclear Engineering

Christophe Demaziere

Chalmers, Applied Physics, Nuclear Engineering

Imre Pazsit

Chalmers, Applied Physics, Nuclear Engineering

Proc. Joint Int. Topl. Mtg. Mathematics & Computation and Supercomputing in Nuclear Applications (M & C + SNA 2007)

Subject Categories

Other Engineering and Technologies not elsewhere specified

Areas of Advance




More information