Studies on Influence of Sodium Void Reactivity Effect on the Concept of the Core and Safety of Advanced Fast Reactor

Abstract

The paper is devoted to studies on the influence of the sodium void reactivity effect (SVRE) on the safety and technical and economical characteristics of the BN-1200-type reactor. Different core options are considered for application to this reactor. These core options differ in design, dimensions, and, hence, SVRE value. It is shown by the analysis that the most flattened core with sodium plenum at the top assures reactor self-protection under beyond-design-basis accident conditions. Sodium plenum abandonment and core height increase causing an SVRE value increase deteriorate reactor self-protection, but at the same time, improve some technical and economical characteristics of the reactor. Self-protection means the possibility to avoid rapid core meltdown under conditions of the above-listed beyond-design accidents. The possibility of controlling beyond-design accidents (for instance, by restoring the power supply of the main pumps in a rather short time) is taken into account. Issues of choosing the optimal core design under these conditions are discussed.

Assessment of Neutron Flux Stability in a High Power BN-Type Reactor in Terms of Modal Spatial Kinetic

“…ния диффузии, аналогичное (1). Рассмотрим нестационарное уравнение диффузии (координаты r, E, t, от которых зависят входящие в уравнение величины, для краткости опущены)…”

“…в запроектных авариях типа ULOF высота а.з. должна быть не более 85 -90 см, а над ней должна рас полагаться натриевая полость [1]. Чтобы в этих ограничениях обеспечить необходимую тепловую мощность а.з., ее диаметр для реактора типа БН большой мощности должен составлять более 4.3 м. Отношение диаметра к высоте для такой а.з.…”

Review of safety improvement on sodium-cooled fast reactors after Fukushima accident

“…The requirement for the sodium void reactivity effect was changed after Chernobyl accident to such that the integral sodium void reactivity effect is near zero. To minimize the sodium void reactivity effect, the following analyses were performed using the following design changes [15]: 1) Arrangement of sodium plenum above the core; sodium void in the plenum gives negative reactivity;…”

Analysis of sodium boiling initiated by unprotected loss of flow in European sodium fast reactor core with different subassembly designs

“…Although there is no specific safety feature operating to ensure the safe reactor shutdown under ULOF conditions, a state-of-the-art low void effect core is implemented, which is anticipated to stabilize the reactor behavior during the accident. This low void effect core has been considered in recent studies (Chenaud et al, 2013;Poplavsky, 2011), where a so-called sodium plenum is incorporated at the top of the fuel instead of the traditionally used fertile material region. This feature is meant to decrease the positive reactivity effect of the core voiding, due to sodium boiling, by increasing the neutron leakage of the core.…”