Authors & Affiliations

Klinov D.A., Gulevich A.V., Eliseev V.A., Malysheva I.V., Buryevsky I.V.
A.I. Leypunsky Institute for Physics and Power Engineering, Obninsk, Russia

Klinov D.A. – First Deputy Director General for Science, PhD (Tech.).
Gulevich A.V. – Deputy Director of Nuclear Energetic Department, Dr. Sci. (Tech.).
Eliseev V.A. – Leading Researcher of Nuclear Energetic Department, PhD (Tech.). Contacts: 1, pl. Bondarenko, Obninsk, Kaluga region, Russia, 249033. Tel.: +7 (484) 399-84-47, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Malysheva I.V. – Senior Researcher of Nuclear Energetic Department.
Buryevsky I.V. – Senior Researcher of Nuclear Energetic Department.

Abstract

In the pre-Chernobyl period, the task of fast reactors was to provide fuel for the intensive development of nuclear energy with a deficit of natural uranium: short doubling time, high HF, high heat intensity, short campaign. After the Chernobyl accident, the main thing was to ensure safety, including in beyond design basis and postulated accidents. Modern fast sodium reactors must, on the one hand, satisfy the safety requirements in design and beyond design basis accidents (in accordance with the requirements of GEN-IV), and on the other, be competitive in comparison with water reactors and other energy sources. The article discusses the methods of transformation of the core of existing and planned Russian fast reactors to meet these requirements. The safety of these reactors in design and beyond design basis accidents is ensured by rejecting the upper end shield and replacing it with a sodium cavity, which allows reducing the NER and ensuring the input of negative reactivity when sodium boils. Such an core is implemented in BN-800 and the designed BN-1200. Improving the competitiveness (increasing the duration of the fuel campaign and KIUM) of the designed and existing reactors is ensured by switching to radiation-resistant clad steel EK164 (currently sold in BN-600, planned in BN-800) and the transition to the core with an axial layer of depleted uranium dioxide (planned for BN-800 and BN-1200). In BN-1200, due to the abandonment of a number of switchgear elements and optimization of the design, a one-and-a-half reduction in metal consumption is achieved. For fuel economy, a ″thick″ fuel rod with a diameter of 9.3 mm and a fuel campaign of 4 years have been adopted. This reduces the annual consumption of fuel rods and fuel assemblies by 2–2.5 times. Both events require modernization of the core. Each of these events allows you to increase the duration of the campaign by 25 %, and the implementation of both measures (transition to new steel and the introduction of a layer) will allow you to increase the campaign and reduce fuel consumption by more than 50 %. The introduction of the axial layer does not require core expansion, which gives additional fuel savings. But the axial layer should not be located in the central plane of the core, but with a shift of 3–5 cm downward. This will improve many characteristics of the core: increase fuel enrichment by a quarter and, as a result, proportionally reduce the neutron flux and radiation damage to the claddings of fuel elements; increase the fuel campaign to 5 years; to reduce the reactivity margin for burnout, without compromising the effectiveness of the control systems, to increase the micro-campaign to 1 year; to level the heat-release field in the vertical direction, to reduce the maximum heat intensity; to improve the course of beyond design basis accidents like ULOF. This method of reducing the rate of accumulation of a damaging dose is equally effective for both MOX and nitride fuels, which makes it possible to unify the core design.

Keywords
fast neutron reactor, safety, competitiveness, core, fuel element, reactivity, accidents, shell steel, fuel, depleted uranium, enrichment, neutron flux, axial layer, sodium cavity, campaign, heat intensity

Article Text (PDF, in Russian)

References

UDC 621.039.51

Problems of Atomic Science and Technology. Series: Nuclear and Reactor Constants, 2020, issue 2, 1:1