Session: 04-03: SMRs, Advanced Reactors and Fusion

Paper Number: 133069

133069 - Core Design and Neutronic Analysis of the European Sodium Fast Reactor With Metallic Fuel 

Abstract: 

The current ESFR (European Sodium Fast Reactor) design was proposed and in-depth evaluated in the frame of the past ESFR-SMART project. As a follow-up project, the ESFR-SIMPLE has been launched with the aim of challenging the current commercial-size ESFR design in terms of safety features and economic performance. Among the new safety measures to be developed and assessed in ESFR-SIMPLE, the current oxide fuel ESFR design will be challenged by a modified version of the core with a high-density fuel. In this case, metallic fuel is chosen due to its significant operational experience worldwide and inherent safety characteristcis, being the reference fuel in the US for new SFR designs. The metal and oxide fuel types differ in their properties, such as density or thermal conductivity, and provide the core with a unique set of responses to operational transients. Thus, the ESFR-SIMPLE project aims to assess what types of benefits can be obtained with high-density fuel, under similar safety and design constraints. Indeed, this evaluation will rely on the joint feedback from neutronics, fuel performance and safety analysis computational tools, but the first step should address the design of a new fuel rod, a new fuel assembly and a new core. Then, this paper describes the designing approach, which aims to preserve the reference oxide-fueled core specifications as well as to reach similar safety requirements. Firstly, and according to the existing irradiation data collected in the US, a ternary U-Pu-Zr alloy is selected as a reference fuel for the new ESFR design with metallic fuel, embedded into a sodium-bonded fuel pins with HT9 cladding material. Regarding the core design, different fuel rod and assembly configurations are proposed and evaluated by means of their neutronic behavior. Core performance characteristics are evaluated in detail for the different design proposals, including reactivity coefficients, equilibrium cycle and their potential reduction of the plutonium mass feed. As a result, the optimal option is selected, relying on the same core map as for the oxide fuel ESFR design but with reduced assembly pitch and fuel rod dimensions, being this more compact design consistent with past experience on metallic fuel systems. The proposed core design presents a significantly reduced reactivity swing compared to the oxide fuel core, allowing to decrease the plutonium content up to 13.25%, in comparison to the content of 18.00% used for the oxide-fueled core. Concerning the preliminary evaluation of the reactivity coefficients, the harder neutron spectrum in the metallic fuel core leads to a less negative Doppler reactivity coefficient and larger positive value of sodium density coefficient. Overall, while the main recommendations for metallic-fuel SFR designs are rigorously met, there is still room for further design modifications based on the core safety performance under accidental conditions.

Presenting Author: Antonio Jiménez-Carrascosa Paul Scherrer Institut

Presenting Author Biography: Antonio Jiménez-Carrascosa is a Postdoctoral Fellow at Paul Scherrer Institut, Switzerland, where he works on the optimization, neutronics and safety analysis for the European Sodium Factor Reactor in the frame of the ESFR-SIMPLE project. He holds a PhD in Nuclear Science and Technology from the Technical University of Madrid, Spain.

Authors:

Antonio Jiménez-Carrascosa Paul Scherrer Institut
Konstantin Mikityuk Paul Scherrer Institut
Nicolas Stauff Argonne National Laboratory
Aydin Karahan Argonne National Laboratory
Emil Fridman Helmholtz-Zentrum Dresden-Rossendorf
Alexander Ponomarev Helmholtz-Zentrum Dresden-Rossendorf