APPLICATION OF HEAT PIPE IN NUCLEAR REACTOR

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APPLICATION OF HEAT PIPE IN NUCLEAR REACTOR

After the Fukushima Daichi nuclear power plant accident in 2011, there has been an increase on the safety of nuclear reactors and power plants. And the concept of passive safety began to be more and more widely accepted, in other words, passive cooling systems are more potential to enhance plant safety through system reliability and eliminate cost associated with the installation, maintenance and operation of the active cooling system that constitutes numerous electric pumps with independent and dedicated power supplies. For instance, in the new generation nuclear reaction, AP1000, passive cooling technologies are widely adopted and the inherent safety features improves dramatically [1, 2].However, the cooling of Spent Fuel Pool (SFP) has not been taken into full consideration.

在2011年福岛第一核电站事故发生后,反应堆和核电站的安全性有所提高。非能动安全的概念开始被越来越多的人接受,换言之,非能动冷却系统更有可能通过系统可靠性提高电厂安全性,主动冷却系统包含多个需要独立专用电源支持的电动泵,这增加了主动冷却系统安装、维修以及操作的成本,而非能动冷却系统恰恰可以消除所有这些成本。例如,在新一代核反应堆AP1000中,非能动冷却技术被广泛采用,固有安全特性显著提高[1,2],但是,乏燃料池(SFP)的冷却仍然没有得到充分的考虑。

The most recent development of heat pipes has been the application within the nuclear sector. Hybrid heat pipes are used to cool down nuclear reactors and increase the control of the system (Fig. 1). As pointed earlier, the concept of a hybrid heat pipe, that is, the combination of the heat pipe and neutron absorber was proposed to enhance the safety of advanced nuclear power plants. With the unique features of heat pipe and control rod, the hybrid heat pipe can remove decay heat directly from the core as it is inserted into the reactor pressure vessel with the same drive mechanism of a control rod. Furthermore, the actual shut down system in nuclear reactors is composed of a neutron absorber (or rod assembly).

热管的最新发展是在核工业中的应用。混合热管被用来冷却反应堆,同时增加对系统的控制(图1)。如前所述,混合热管(即热管和中子吸收器的结合)的提出,正是为了提高先进核反应堆的安全性。混合热管有着独特的热管结合控制棒的特点,其与控制棒以相同的驱动机理被安装在反应堆压力容器中,这使得混合热管能够直接排出堆芯的衰变热。此外,核反应堆的实际停堆系统由中子吸收器(或棒组件)组成。

Fig.1|Hybrid heat pipes

The function of the rod assembly is to control the nuclear reaction in the reactor core. Raising and lowering the control rods allow operators to control the rate of the nuclear reaction. For emergency cases, the control rod will be lowered by gravity to stop the nuclear reaction and shutdown the reactor. However, this system is limited as far as the Three Miles Island and the Fukushima Daichi nuclear power plant accidents are concerned. Truly, the active cooling system failed to remove the heat decay of the water contained in the reactor, which led to a fusion or melt down of the core, even after the depressurisation of the pressure vessel. In the nuclear reactors, Heat pipe serves as a shutdown device. Investigations of heat pipe technology has been reviewed in [3].The hybrid heat pipe is used for two main purposes. The first is to shut down the reactor in case of accident, and the second is to remove the heat decay generated during the reaction from the core after the shutdown. A passive device that combines the functions of the current control rod assembly and the passive cooling systems could avoid such accidents in the future.

控制棒组件的作用是控制反应堆堆芯内的核反应。控制棒的上升和下降使操作员能够控制核反应的速率。在紧急情况下,控制棒将在重力作用下下降,以停止核反应并关闭反应堆。主动冷却系统在三里岛和福岛第一核电站核事故中体现出了其局限性—事实上,主动冷却系统未能消除事故反应堆的热衰变,从而导致堆芯熔化,即使在压力容器减压后也是如此。在核反应堆中,热管是一种停堆装置。文献[3]对热管技术的研究进行了综述,混合热管主要有两个用途—第一种是在发生事故时关闭反应堆,第二种是在停堆后将反应过程中产生的衰变热从堆芯中排出。将现有控制棒组件和非能动冷却系统的功能结合起来的非能动装置,可以避免将来发生此类事故。

References:

  1. Mochizuki, M., et al., Heat pipe based passive emergency core cooling system for safe shutdown of nuclear power reactor. Applied Thermal Engineering, 2014. 73(1): p. 699-706.
  2. Sutharshan, B., et al., The AP1000TM Reactor: Passive Safety and Modular Design. Energy Procedia, 2011. 7: p. 293-302.
  3. Jeong, Y.S., et al., Hybrid heat pipe based passive in-core cooling system for advanced nuclear power plant. Applied Thermal Engineering, 2015. 90: p. 609-618.

Writer: Emmanuel Osei Tutu (Harbin Engineering University)
Editor: Zhang Chao& Priscilla Oforiwaa
Designers: Zhang Chao& Zhang Jing
Translation : Zhang Chao

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