MARTIN HOWARD COOPER
Engineers in Pittsburgh, PA

4698200, Oct 6, 1987

Dec 23, 1985

6/812045

Robert K. Sievers - N. Huntingdon PA
Martin H. Cooper - Churchill PA
Robert B. Tupper - Greensburg PA

The United States of America as represented by the United States
Department of Energy - Washington DC

G21C 702

376233

A self-actuated shutdown system incorporated into a reactivity control assembly in a nuclear reactor includes pumping means for creating an auxiliary downward flow of a portion of the heated coolant exiting from the fuel assemblies disposed adjacent to the control assembly. The shutdown system includes a hollow tubular member which extends through the outlet of the control assembly top nozzle so as to define an outer annular flow channel through the top nozzle outlet separate from an inner flow channel for primary coolant flow through the control assembly. Also, a latching mechanism is disposed in an inner duct of the control assembly and is operable for holding absorber bundles in a raised position in the control assembly and for releasing them to drop them into the core of the reactor for shutdown purposes. The latching mechanism has an inner flow passage extending between and in flow communication with the absorber bundles and the inner flow channel of the top nozzle for accommodating primary coolant flow upwardly through the control assembly. Also, an outer flow passage separate from the inner flow passage extends through the latching mechanism between and in flow communication with the inner duct and the outer flow channel of the top nozzle for accommodating inflow of a portion of the heated coolant from the adjacent fuel assemblies.

4405558, Sep 20, 1983

Oct 15, 1980

6/197380

James D. Mangus - Hempfield Township, Westmoreland County PA
Martin H. Cooper - Churchill PA

Westinghouse Electric Corp. - Pittsburgh PA

G21C 708

376233

The nuclear reactor shutdown system comprises a temperature sensitive device connected to a magnetic latch of a neutron absorbing mechanism. The temperature sensitive device is disposed in the neutron absorbing mechanism in such a manner that it is exposed to the reactor coolant so that when the reactor coolant temperature rises above a specific level, the temperature sensitive device will cause the magnetic latch to open and allow neutron absorbing material to enter the reactor core. The temperature sensitive device comprises temperature sensitive material which may be a temperature sensitive resistor sometimes referred to as a thermistor. The thermistor is a device wherein its resistivity significantly increases with increase in its temperature such that when its temperature has significantly increased, the current passing through this system substantially decreases. Therefore, when the nuclear reactor coolant temperature rises significantly, the resistivity in the temperature sensitive material significantly increases to the point where little electricity flows through the circuit thereby causing the magnetic field in the magnetic latch to fall to a level at which the magnetic latch opens thereby inserting neutron absorbing material in the reactor core.