| 摘要 |
An instrument for monitoring cooling conditions in the reactor core of a light-water reactor comprises a probe 2 fitted inside the reactor vessel, which probe is made up of a sleeve 12 made of a material which has long neutron absorption and is also watertight, and a resistor 11 hermetically sealed in the sleeve 12. The resistor 11 is connected to leads 5 for delivery of power. The resistance of the resistor 11 depends on its temperature. The instrument also includes sensors which produce an output signal, dependent on the resistance of resistor 11, when current flows through it. In a first functional condition, the monitoring instrument is used to detect any reduction or loss of the cooling capacity of the cooling medium which surrounds the probe 2. A relatively large amount of power is delivered when the resistor and the delivered power are arranged to correspond to the cooling capacity, so that the heat generated in the resistor as a result of the said delivered power is removed via the cooling medium which surrounds the probe 2. If, however, the cooling capacity drops for any reason, e.g, through an accident causing loss of cooling medium, the temperature in the resistor 11 will rise. Since the resistance of the resistor 11 is strongly dependent on temperature, the resistance will change, and as a result a change also occurs in the output signal produced by the sensors. <IMAGE>
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