US 4,158,602 A · Method and apparatus for controlling the neutron flux in nuclear reactors

Abstract

A control rod assembly in a nuclear reactor that automatically scrams the reactor when a loss of coolant flow occurs and that can also control the level of neutron flux in the reactor. The control rod assembly includes a separator plate having an orifice through which the reactor coolant flows and a sealing surface around the orifice. The control rod in the assembly has a complementary sealing surface. When the control rod and separator plate are brought into contact, the differential pressure across the separator plate caused by the flow of the primary coolant through the reactor core retains the two sealing surfaces together. If the flow of coolant stops or the differential pressure across the separator plate decreases for any reason, the control rod drops by gravity and the reactor is scrammed. The control rod is also automatically dropped as a result of the lateral vibration of an earthquake or by the downward motion of the rod drive shaft, either of which will open the sealing surfaces and reduce the sealing pressure.

Claims22

Dependent claims

Apparatus for scramming a nuclear reactor having fuel elements and cooled by a flow of primary coolant, comprising:

(a) reactor scramming means having a large neutron absorption and insertable into the high neutron flux region of the reactor;
(b) means in the nuclear reactor for retaining the scram means away from the high neutron flux region of the reactor and in contact with a separator plate by restricting a portion of the flow of coolant through the reactor and developing a differential pressure across said separator plate, said separator plate being concurrently exposeable to the pressure of primary coolant flowing past the reactor fuel elements, said restricted flow and resulting differential pressure generating a force which maintains the scramming means away from the high neutron flux region when there is a flow in the reactor, said retaining means being adapted for releasing the scramming means from the separator plate independently from external actuation and in response to and substantially simultaneously with a reduction in the flow of coolant past the reactor fuel elements, thereby causing the scramming means to enter the high neutron flux region of the reactor;
and
(c) a supporting drive shaft and connector means connected between said drive shaft and the scramming means for manuvering the scramming means with respect to the high flux region of the core irrespective of coolant flow.

1 more element

In a nuclear reactor of the type cooled by a flow of coolant and having controls rods that are mounted for movement with respect to the fuel elements in the core, the improvement comprising:

(a) a control rod in a control rod housing in a nuclear reactor, said control rod having a sealing surface and insertable into the high neutron flux region of the reactor independently from external actuation;
(b) a supporting drive shaft connected to the control rod for moving the control rod with respect to the fuel elements;
and
(c) a stationary separator plate forming a top wall of the control rod housing and directly and concurrently exposed to the pressure of coolant flowing past the fuel elements in the nuclear reactor and having an orifice across which a differential pressure is developed by the flow of coolant through the reactor, said separator plate also having a sealing surface around said orifice which complements the sealing surface of the control rod, the sealing surfaces on the control rod nd separator plate can be retained together by the differential pressure developed by the coolant flow, said separator plate being positioned within the reactor so that a reduction in the flow of coolant past the fuel elements causes, in direct response thereto, a corresponding reduction of the differential pressure across the separator plate, release of the sealing surfaces on the control rod and the separator plate, and the entry of the control rod into the high neutron flux region of the reactor substantially simultaneously with the reduction in flow.

1 more element

In a nuclear reactor of the type cooled by a flow of coolant and having control rods that are mounted for movement with respect to the fuel elements in the core, the improvement comprising:

(a) a control rod in a control rod housing in a nuclear reactor, said control rod having a sealing surface and being adapted for self-initiating a scram;
and
(b) a separator plate forming a top wall of the control rod housing and directly and concurrently exposed to the pressure of coolant flowing past the fuel elements in the nuclear reactor and having an orifice across which a differential pressure is developed by the flow of coolant through the reactor, said separator plate also having a sealing surface around said orifice which complements the sealing surface of the control rod, the sealing surfaces on the control rod and separator plate can be retained together by the differential pressure developed by the coolant flow, said separator plate being positioned within the reactor so that a reduction in the flow of coolant past the fuel elements causes, in direct response thereto, a corresponding reduction of the differential pressure across the separator plate, release of the sealing surfaces on the control rod and the separator plate, and the entry of the control rod into the high neutron flux region of the reactor substantially simultaneously with the reduction in flow;
(c) a rod drive shaft operatively connected to the control rod for maneuvering the control rod sealing surface into sealing engagement with the sealing surface of the separator plate, said control rod being insertable into the high neutron flux region of the reactor independently from actuation by the rod drive shaft;
and
connecting means between the control rod and supporting rod drive shaft for manuvering said control rod with respect to the high neutron flux region of the reactor irrespective of the flow of coolant.

3 more elements

Dependencies are inferred from the claim text.

Method and apparatus for controlling the neutron flux in nuclear reactors

Life of this patent

Method and apparatus for controlling the neutron flux in nuclear reactors

Life of this patent

Abstract

Claims22