Model-Free Coordinated Control for MHTGR-Based Nuclear Steam Supply Systems

Zhe Dong

doi:10.3390/en9010037

Abstract

The modular high temperature gas-cooled reactor (MHTGR) is a typical small modular reactor (SMR) that offers simpler, standardized and safer modular design by being factory built, requiring smaller initial capital investment, and having a shorter construction period. Thanks to its small size, the MHTGRs could be beneficial in providing electric power to remote areas that are deficient in transmission or distribution and in generating local power for large population centers. Based on the multi-modular operation scheme, the inherent safety feature of the MHTGRs can be applicable to large nuclear plants of any desired power rating. The MHTGR-based nuclear steam supplying system (NSSS) is constituted by an MHTGR, a side-by-side arranged helical-coil once-through steam generator (OTSG) and some connecting pipes. Due to the side-by-side arrangement, there is a tight coupling effect between the MHTGR and OTSG. Moreover, there always exists the parameter perturbation of the NSSSs. Thus, it is meaningful to study the model-free coordinated control of MHTGR-based NSSSs for safe, stable, robust and efficient operation. In this paper, a new model-free coordinated control strategy that regulates the nuclear power, MHTGR outlet helium temperature and OTSG outlet overheated steam temperature by properly adjusting the control rod position, helium flowrate and feed-water flowrate is established for the MHTGR-based NSSSs. Sufficient conditions for the globally asymptotic closed-loop stability is given. Finally, numerical simulation results in the cases of large range power decrease and increase illustrate the satisfactory performance of this newly-developed model-free coordinated NSSS control law.

Highlights

Small modular reactors (SMRs) are those nuclear fission reactors with electrical output power less than 300 MWe, and could be beneficial in providing electricity to the areas without transmission or distribution infrastructure in generating local power for a large population center and in being viable for specific applications such as heat sources for industrial complexes [1,2]
Motivated by the necessity of developing model-free coordinated control method for nuclear steam supplying system (NSSS), a model-free coordinated controller of the NSSS composed of one modular high temperature gas-cooled reactor (MHTGR) and one once-through steam generator (OTSG) are proposed through the physics-based approach in this paper
MHTGR-based NSSS coordinated control given by Equations (16), (31) and (32) is model-free, which leads to easy implementation and tuning

Summary

Introduction

Small modular reactors (SMRs) are those nuclear fission reactors with electrical output power less than 300 MWe, and could be beneficial in providing electricity to the areas without transmission or distribution infrastructure in generating local power for a large population center and in being viable for specific applications such as heat sources for industrial complexes [1,2]. The above control strategies can provide large-scale closed-loop stability for the nuclear reactors or steam generators These control laws have the drawback of heavy model-reliance. Motivated by the necessity of developing model-free coordinated control method for NSSSs, a model-free coordinated controller of the NSSS composed of one MHTGR and one OTSG are proposed through the physics-based approach in this paper This NSSS coordinated control law has three key features: (a) there is no representation of any dynamic models for generating control input, state-observation or prediction; (b) the controller parameters are insensitive to the NSSS physical or thermal-hydraulic parameters; and (c) the closed-loop is globally asymptotically stable. Numerical simulation results in the cases of large range power increase and decrease illustrate the satisfactory regulating performance of this NSSS coordinated controller

Modeling and Problem Formulation

Model-Free Coordinated Control Design

Simulation Results with Discussion