Induced nuclear reactions: processes – systems – and elements – With control of reactor – By movement of control element or by release of neutron...
Patent
1988-09-06
1991-04-16
Behrend, Harvey E.
Induced nuclear reactions: processes, systems, and elements
With control of reactor
By movement of control element or by release of neutron...
376247, 376258, 376327, G21C 716, G21C 1700
Patent
active
050080687
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a control rod system for a nuclear reactor plant. More particularly, this invention relates to a control rod system for a heating reactor of a nuclear reactor plant.
Heretofore, various types of plants have been known which employ a nuclear reactor, particularly a heating reactor. For example, German OS 3430929 describes a heating reactor plant more particularly a heating reactor, having a pressure vessel receiving a coolant and a reactor core embodied mainly by straight vertical channel-like fuel elements containing fissile material and, disposed between such elements, tubular vertically movable control rods to which absorber rods are secured.
Conveying means are also provided which pressurize coolant from the pressure vessel in order to move the control rods, each control rod so extending around a tubular guide rod which is immobile relative to the fuel elemnets as to leave a first annular gap between the control rod and the guide rod. The guide rod interior is operative as a first pressure chamber and communicates with the delivery side of the conveying means. The top end of the control rod is closed so that the coolant conveyed by the conveying means returns from the first pressure chamber through the first annular gap to the pressure vessel.
The coolant flowing through the first pressure chamber maintains therein a pressure which retains the associated control rod in a particular position which, given a constant delivery of coolant, is substantially constant. The pressure in the first pressure chamber can be altered by altering the delivery of coolant so that the control rod shifts and, if the pressure remains constant, takes up a new position. The reactor power output can therefore be controlled by shifting the control rods. An advantage of the known plant is that there is no appreciable friction when the control rods shift on the guide rods and in the event of a cessation of coolant flow and, therefore, of the rodsupporting pressure, the control rods automatically return to their bottom safety position in which the absorber rods screen the fuel elements from one another so that the nuclear reaction is interrupted. However, control rod position cannot be adapted sufficiently accurately to the associated reactor power output in the known plant. To obviate this disadvantage, the known plant has ultrasonic transmitters which are disposed in the reactor channels above the control rods and which ascertain control rod position and report it to the exterior.
Accordingly, it is an object of the invention to improve the association between a control rod position and reactor power so that control rod position detectors are not required.
It is another object of the invention to permit pressure surges to be produced in a control rod system in a controlled manner.
It is another object of the invention to maintain a control rod in an equilibrium position during normal operating conditions of a reactor plant.
Briefly, the invention provides a nuclear reactor plant which includes a pressure vessel for receiving a coolant, a reactor core including a plurality of vertical fuel elements containing fissile material and tubular control rods which are vertically movable between the fuel elements and which carry absorber rods which are positioned between the fuel elements. In addition, a plurality of fixed guide rods are provided with each guide rod being disposed within a respective control rod to define a first annular gap therebetween and a first pressure chamber between an upper end of the guide rod and the respective control rod. In accordance with the invention, a plurality of vertical spindles are also provided with each spindle being secured to a control rod and depending into a guide rod to define a second annular gap therewith as well as a second pressure chamber below the spindle within the guide rod for receiving a flow of coolant in order to position the control rod relative to the guide rod. In addition, a restrictor is placed in each gap for throttling the flow of coolant therethrou
REFERENCES:
patent: 3031397 (1962-04-01), Fortescue et al.
patent: 3442759 (1969-05-01), Molle et al.
patent: 3462345 (1969-08-01), Jabsen
patent: 3752736 (1973-08-01), Kornbichler et al.
patent: 4686077 (1987-08-01), Straub
Behrend Harvey E.
Sulzer Brothers Limited
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