Performance-of control and safety circuits

6 Performance of Control and Safety Circuits. The two instruments in which most interest has been evidenced are the period indicator and the servo mechanism. 

The period meter is a direct indicator of rate of increase or decrease of reactor level. Its scale is calibrated in seconds so that the period, i.e., the time required for the power level to change by a factor of 2-7, cart be read directly. This instrument proved extremely valuable in start-ups and was also useful for making changes in power level when the reactor was being controlled manually. 

The servo mechanism performed exceptionally well. With this device any desired power level in the operating range could be maintained for hours with 

Another feature of the MTB control arrangement is the safety circuits which protect against higher-than-normal power levels. Unsafe levels causW a reduction in current to the electromagnets and subsequent release of the control rods. The time required for.release of the rods had been measured as approximately 15 msec before installation in the Mock Up. During operation the time interval between the scram signal and shutdown of the reactor was observed to be approximately 30 nsec. 

Although a number of minor changes in the control instrumentation were deemed desirable before construction of the final. UTR instrumenta. it can be said that their performance in the Mock-Up was very satisfactory. 

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