Nuclear reactor shutdown system

• US 4,405,558 A
• Filed: 10/15/1980
• Issued: 09/20/1983
• Est. Priority Date: 10/15/1980
• Status: Expired due to Term

• Current Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Cooper, Martin H., Mangus, James D.
• Primary Examiner(s): Behrend, Harvey E.
• Application Number:
  US06/197,380
• Time in Patent Office: 1,070 Days
• Field of Search: 176/DIG. 5, 176/86 R, 176/36 R, 176/22, 73/349, 73/362 AR, 73/347, 338/22, 338/24, 338/25, 338/27, 376/228, 376/243, 376/233, 376/336, 376/337
• US Class Current: 376/233
• CPC Class Codes: G21C 9/02 Means for effecting very rapid reduction of the reactivity factor under fault conditions, e.g. reactor fuse; Control elements having arrangements activated in an emergencycontrol elements per se G21C7/00
• CPC Class Codes: Y02E 30/30 Nuclear fission reactors

Abstract

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.

Claims

1. Nuclear reactor shutdown apparatus comprising:

neutron absorbing control rods arranged to be inserted in a control assembly of a nuclear reactor core having a coolant flowing therethrough;

a magnetic latch comprising an upper member having a bore therethrough for flow of reactor coolant, a lower member, and a coil;

said lower member slidably disposed on the lower end of said upper member and attached to said control rods for suspending said control rods above said reactor core;

said coil disposed around said upper member and connected in an electrical circuit for establishing a magnetic flux through said upper member and said lower member for magnetically suspending said lower member above said reactor core when said coil is energized;

a tubular member connected to said bore in said upper member and disposed in the flow of reactor coolant;

a plurality of conduits located remote from said coil and connected to said tubular member for conducting a portion of said reactor coolant exiting said reactor core through said tubular member; and

a temperature responsive resistor disposed in said tubular member near said conduits in the flow of said reactor coolant and located downstream of and remote from said coil and connected to said coil by said electrical circuit whereby an increase in said reactor coolant temperature raises the temperature and resistivity of said temperature responsive resistor thereby reducing the electrical current flowing through said coil and reducing the magnetic flux through said upper member and said lower member which causes said lower member to slide downwardly relative to said upper member thereby inserting said control rods into said control assembly.