Period meter for reactors

In a device for developing a reactor scram signal in response to a reactor period T less than a specific value, the device including means for measuring the neutron flux density of the reactor and developing a first output signal which is a function of the neutron flux density, a differentiator coupled to the means for measuring for diffentiating the first output signal to develop a second output signal and a first comparator coupled to the differentiator and being responsive to the second output signal greater than a particular value to develop a first alarm signal, an apparatus for reducing noise induced scrams comprising:

• a second comparator coupled to the first comparator and the means for measuring and being responsive to first output signal greater than a predetermined value and coincidentally the first alarm signal to develop a second alarm signal, a first gate circuit coupled to the means for measuring, a first signal storage circuit coupled to said first gate circuit, a timing circuit for developing periodically a first timing signal coupled to said first gate circuit, said first gate circuit being responsive to said first timing signal to couple the first output signal to said first signal storage circuit, said first signal storage circuit acting to continuously develop a third output signal equal to the first output signal at the instant said first output signal is coupled to said first storage circuit plus a particular quantity with said third output signal being updated each time said first output signal is coupled to said first signal storage circuit in response to said first timing signal, a third comparator coupled to the means for measuring and said first signal storage circuit and being responsive to the first output signal greater than said third output signal to develop a third alarm signal, and an OR gate coupled to said second and third comparators and being responsive to an alarm signal developed thereby to develop a reactor scram signal.