"Methods for measuring the characteristics of delayed neutrons and verifying nuclear data"

Gremyachkin D.E. (Researcher, Institute of Physics and Power Engineering, Obninsk)

In the nuclear reactor physics, one of the most essential issues is the control of a fission chain reaction. As a result of fission, 2-3 neutrons are instantly emitted. A small fraction of neutrons, less than 1%, occurs with some delay after the fission event. Thus, delayed neutrons allow to address the issue of an uncontrolled fission chain reaction on prompt neutrons, since they slow down the response of the reactor to a change in reactivity.

Due to the accumulation of long-lived highly toxic minor actinides, it is necessary to study and develop approaches to their disposal. One of such approaches is adding of long-lived minor actinides produced during the operation of nuclear power facilities to nuclear fuel in order to use them for generating energy as a result of fission. The neutron spectrum in such facilities is harder. Therefore, for the safe control of such facilities, it is necessary to know with high accuracy the characteristics of delayed neutrons emitted during the fission of nuclei that constitute nuclear fuel.

The development of a complex method for measuring the characteristics of delayed neutrons emitted during the fission of actinides using fast neutrons based on the effects that distort the results, as well as the development of methods for verifying the estimated nuclear physics data using the obtained results and recommended data, will be considered.

As a result, a technique for measuring the characteristics of delayed neutrons based on the spectral characteristics of the primary source of neutrons has been improved, a method for processing experimental data based on the spectral characteristics of the primary source of neutrons has been developed and applied,  a new approach to measuring the temporal characteristics of delayed neutrons in the fission of heavy nuclei using neutrons generated in the reaction T (d,n) on a solid target has been proposed and approaches to verifying the estimated nuclear data using experimental and recommended macroscopic data on delayed neutrons have been developed, new experimental data on the time parameters of delayed neutrons in the fission of actinide nuclei in a wide range of primary neutron energies have been obtained.