Dynamic Matrix Control for the Thermal Power of MHTGR-Based Nuclear Steam Supply System

Di Jiang,Xiaojin Huang,Zhe Dong,Miao Liu

doi:10.3390/en11102651

Abstract

The modular high temperature gas-cooled reactor (MHTGR) based nuclear steam supplying system (NSSS) is constituted by an MHTGR, a once-through steam generator (OTSG) and can generate superheated steam for industrial heat or electric power generation. The wide range closed-loop stability is achieved by the recently proposed coordinated control law, in which the neutron flux and the temperatures of both main steam and primary coolant are chosen as controlled variables, and the flowrates of both primary and secondary loop and the control rod speed are chosen as manipulated variables. However, the thermal power is only controlled in open loop manner and hence could be further optimized through feedback. Motivated by this, a dynamic matrix control (DMC) is proposed for optimizing the thermal power of MHTGR based NSSS. A simple step-response model with the thermal power response data is utilized in designing the DMC. The design objective of DMC is to optimize the deviation of the thermal power from its reference under its rate constraint. Then, by the virtue of strong stability of existing control law and optimization ability of DMC, a cascade control structure is implemented for the thermal power optimization, with the coordinated control law in the inner loop and DMC in the outer loop. Numerical simulation results show the satisfactory improvement of thermal power response. This cascade control structure inherits the advantages of both proportional-integral-differential (PID) control and DMC, by which the zeros offset and the short settling time of thermal power are realized.

Highlights

Nuclear steam supply system (NSSS), which utilizes the nuclear fission to produce high-pressure steam and to drive some thermal load devices, occupies an important role in nuclear power plants (NPPs)
The Modular high temperature gas-cooled reactor (MHTGR)-based NSSS module operates at reactor full power power (RFP)
The thermal power set-point begin to ramp down from 100% to 50% RFP with the rate of 5% RFP/min manually set by operator at 8000 s, and ramp up to 100% RFP with the same rate at 12,000 s

Summary

Introduction

Nuclear steam supply system (NSSS), which utilizes the nuclear fission to produce high-pressure steam and to drive some thermal load devices, occupies an important role in nuclear power plants (NPPs). Modular high temperature gas-cooled reactor (MHTGR) is a representative small modular reactors (SMRs) and has received a lot of attention due to its virtues of inherent safety and strongly efficient energy source [1,2]. The power-level control of MHTGR-based NSSS, which regulates the neutron flux, temperatures of both helium and steam by changing the control rod speed, rotation-rate of feed water pump and helium blowers, is a critical technique for the efficient and safe operation of NPPs. Currently, in China, stimulated by the need in the carbon emission reduction, local power demand and heat sources for industrial complexes, control performance optimization and guaranteed inherent stability are two promising directions of MHTGR-based NSSS power control [3].

Results

Discussion

Conclusion