Neutron noise analysis using the basic element method

Highlights: • Algorithm for disentangling neutron noise from reactor-operations' power changes. • Algorithm tested on both static and dynamic states of the reactor. • Algorithm optimized for the best separation between neutron noise and power changes. • Algorithm speed adequate for real-time monitoring. - Abstract: Neutron noise spectra in nuclear reactors are a convolution of multiple induced reactivities. Under normal IBR-2M reactor operating conditions the full noise range can reach $\pm$22% with respect to average power. Slow changes in average power (induced for instance by the control rods) are thereby much smaller than the neutron noise, however they are of importance in conducting the safe operation of the reactor. The problem we address is the separation of neutron noise from the slow power-changes. For this task we used an algorithm based on the basic element method (BEM) developed at Laboratory of Information Technologies – LIT JINR. The algorithm was applied to both static and dynamic states of the reactor in the 0–2 MW power range. The average processing time for one point on a x86₆4 Intel Core i5-4570 Sandy Bridge processor at 3.20 GHz, was approximately 50 $\mu$s, which allows the use of the MSPPA-6 algorithm in real time.