"On the possibility of creating a UCN source at a periodic pulsed reactor II"

A.I. Frank


It has recently been shown that the principle of time focusing and F.L. Shapiro's idea of pulsed filling of a UCN trap make it possible to create a sufficiently intense UCN source at a pulsed reactor of medium power. For a time-dependent effect on the neutron velocity, providing focusing in time, it was proposed to use the phenomenon of nonstationary neutron diffraction on a moving diffraction structure. Subsequent analysis has shown that the creation of a time lens based on this principle is associated with hardly surmountable difficulties. This forces us to turn to an alternative focusing approach based on the principle of nonstationary spin flip in a magnetic field.
The report will consider both approaches to time focusing and analyze the advantages and disadvantages of each of them. The results of conceptual calculations of a UCN source with magnetic focusing in the conditions of the IBR-2 and Neptun reactors will be presented, as well as the main problems encountered in the creation of such a source will be formulated.

“On areas of neutron investigations at the URAL research reactor”

Gubkin A.F. M.N. Mikheev Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences

"Kurchatov Complex for Synchrotron and Neutron Investigations:Main Areas of Work"

S.N.Yakunin(first deputy head, KCSNI NRC KI)


"Applications of modern X-ray methods in studies of liquid interfaces"

N.N.Novikova (chief researcher, NRC KI)

"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.