Investigation of a self-actuated, gravity-driven shutdown system in a small lead-cooled reactor

• Passive safety systems in a nuclear reactor allow to simplify the overall plant design, beside improving economics and reliability, which are considered to be among the salient goals of advanced Generation IV reactors. This work focuses on investigating the application of a self-actuated, gravity-driven shutdown system in a small lead-cooled fast reactor and its dynamic response to an initiating event. The reactor thermal-hydraulics and neutronics assessment were performed in advance. According to a first-order approximation approach, the passive insertion of shutdown assembly was assumed to be influenced primarily by three forces: gravitational, buoyancy and fluid drag. A system of kinematic equations were formulated a priori and a MATLAB program was developed to determine the dynamics of the assembly. Identifying the delicate nature of the balance of forces, sensitivity analysis for coolant channel velocities and assembly foot densities yielded an optimal system model that resulted in successful passive shutdown. Transient safety studies, using the multi-point dynamics code BELLA, showed that the gravity-driven system acts remarkably well, even when accounting for a brief delay in self-actuation. Ultimately the reactor is brought to a sub-critical state while respecting technological constraints.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Energiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Energy Engineering (hsv//eng)

Nyckelord

Gravity-driven shutdown system

Lead-cooled fast reactor

Self-actuated passive system

Small modular reactor

Critical current density (superconductivity)

Fast reactors

MATLAB

Reactor shutdowns

First-order approximations

Generation IV reactors

Kinematic equations

Lead cooled fast reactor

Lead-cooled reactor

Passive safety systems

Reactor thermal hydraulics

Technological constraints

Sensitivity analysis

Publikations- och innehållstyp

ref (ämneskategori)

kon (ämneskategori)