Authors & Affiliations

Levchenko Yu.D., Delnov V.N.
A.I. Leypunsky Institute for Physics and Power Engineering, Obninsk, Russia

Levchenko Yu.D. – Leading Researcher, Dr. Sci. (Tech.), Senior Researcher (academic title), A.I. Leypunsky Institute for Physics and Power Engineering. Contacts: 1, pl. Bondarenko, Obninsk, Kaluga region, Russia, 249033. Tel.: +7(484) 399-54-93; e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it..
Delnov V.N. – Head of Intellectual Property Department, Dr. Sci. (Tech.), Associate Professor, A.I. Leypunsky Institute for Physics and Power Engineering.


The article describes the method for selection of fast reactor fuel assembly (FA) throttle design that consists of two or more throttling washers in the central tube or in the inner shell wall of the bottom nozzle. The washers are arranged with an equal pitch relevant to the preset hydraulic resistance of the throttling device. The main physical point is based on a well-known fact that hydraulic losses in two or more washers located with a zero clear distance between them differ insignificantly from the losses of one washer and constantly grow with an increase in the distance between the neighboring washers. The constant and maximum values of hydraulic losses are observed at the gap value equal to approximately 10 heights of washer lips. The applicability of this method in the design calculations was verified in the analysis of throttling devices in fast neutron reactor FA bottom nozzles. The analysis was performed with the use of a universal dependence of the mutual effect of a few washers placed in series in the flow part of the bottom nozzle. For all the options of the bottom nozzle design the coolant rates did not exceed 15 m/s.

nuclear reactor, core; fuel assembly, bottom nozzle, flow throttling, throttling washers, hydraulic calculation, hydraulic resistance (drag) coefficient, methods and examples of calculation

Article Text (PDF, in Russian)


UDC 532

Problems of Atomic Science and Technology. Series: Nuclear and Reactor Constants, 2017, issue 4, 4:4