# Research on the Dynamic Characteristics Analysis and Power Control Method of Heat Pipe Reactors
## 4 Research on Power Control Method of HPR
### TD3 Algorithm
## 6 Conclusions

In this paper, a lightweight dynamic model of the \"MegaPower\" HPR is established through equating the core of the HPR, designing the heat pipe heat exchanger, and building the thermal resistance network based on the lumped parameter idea. After the simulation, the absolute value of the steady-state error between the model solution and the reference value in the steady-state full power case does not exceed 3.2%, and the model can be used for the analysis of the dynamic characteristics and the study of the power control method of the HPR. Through introducing a reactivity step disturbance of \(-10\) PCM and a 5% step disturbance of mass flow rate to the HPR, the dynamic characteristics of the HPR are analyzed. It shows that the HPR can reach the new steady state using its own temperature negative feedback characteristics and has good self-stability and self-regulation. But its adjustment time is long, and the parameters of each part are accompanied by oscillation changes. In order to improve the anti-disturbance and load tracking capability of the HPR, this paper designs an RL controller for reactor power control based on the TD3 algorithm, with reasonable settings of the states \(\mathbf{s}\), the structure of the neural network, the reward functions, and other hyperparameters of the TD3 algorithm. To verify the RL controller, the control performance of the RL control was compared with that of the uncontrolled case in a step simulation from 100%FP to 90%FP, and the control performance of the RL controller and the PID controller under the compound condition and the condition of significant load power fluctuations was also compared. The results show that the RL controller can quickly regulate the reactor power and suppress the impact of disturbances, and the settle time of nuclear power is less than 51.70 s and the steady-state error is less than 2.37% in both simulations, which means that the RL controller can improve the dynamic and steady-state performance of the HPR and has the ability to control nuclear power in all operating conditions. The influence of the SCO\({}_{2}\) Brayton cycle on reactor power control is not considered in this paper. On the basis of this paper, some propositional research can be carried out from the following aspects in the future: On the one hand, appropriate collaborative control strategies and methods can be proposed based on the safe operation requirements of the HPR and SCO\({}_{2}\) Brayton cycle. On the other hand, in view of the possibility that the HPR nuclear power plant will operate in the unmanned condition in the future, autonomous control strategies and other key technologies, such as situational awareness technology and autonomous fault-tolerant control technology, can be studied. Conceptualization, S.Y. and R.Y. ; methodology, S.Y. ; software, S.Y. ; validation, S.Y., D.S., W.M. and Y.Z. ; formal analysis, R.Y. ; investigation, W.M. ; resources, Y.Z. ; data curation, D.S. ; writing--original draft preparation, S.Y. ; writing--review and editing, R.Y. ; visualization, W.M. ; supervision, W.M. ; project administration, R.Y. ; funding acquisition, R.Y. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. The data that support the findings of this study are available from the corresponding author upon request. The authors declare no conflict of interest. ## References

* (1) IAEA. Advances in Small Modular Reactor Technology Developments. 2022 Edition. 2022. Available online: [[https://aris.iaea.org/Publications/SMR_booklet_2022.pdf](https://aris.iaea.org/Publications/SMR_booklet_2022.pdf)]([https://aris.iaea.org/Publications/SMR_booklet_2022.pdf](https://aris.iaea.org/Publications/SMR_booklet_2022.pdf)) (accessed on 21 August 2023). * (2) [PERSON]; [PERSON]; [PERSON]; [PERSON] _Design of Megautaut Power Level Heat Pipe Reactors_; Technical Report LA-UR-15-28840; Los Alamos National Lab: Los Alamos, NM, USA, 2015.