思路解析：
1. 看懂基本过程和原理，定位流程的起点和终点。
2. 按照箭头依次进行描述，不能出现顺序颠倒，或是过程缺失。
3. 图中的文字提示应加入到描述之中。
4. 分段原则：流程图基本不分段，一个主体段包含所有过程，但请注意过程之间的连接词，eg,首先，然后，接下来，最后。
参考范文：
The process of how a gas-cooled nuclear reactor works consists of the reactor itself and a heat exchanger.
The reactor contains uranium fuel elements which are surrounded by graphite moderators and topped by charge tubes for loading fuel elements, and boron control rods. The whole reactor is contained in a pressure vessel surrounded by a concrete shield.
From the reactor the hot gas flows through a duct into the heat exchanger which is outside the concrete radiation shielding. In the heat exchanger, steam is generated in a secondary loop. There a pipe brings in water which is heated to steam, and this then flows out to the turbo-alternator. Meanwhile the hot gas sinks to the bottom of the heat exchanger and passes through a gas blower which pushes it into a cool gas duct and back to the reactor.
As can be seen, this is a continuous cycle that keeps the reactor from overheating, while carrying away the heat and steam, which will power the turbines.
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