Automatic temperature and humidity regulation – Thermostatic – Expanding solid
Reexamination Certificate
1999-08-02
2001-11-06
Carone, Michael J. (Department: 3641)
Automatic temperature and humidity regulation
Thermostatic
Expanding solid
C376S282000, C376S283000, C376S277000, C376S336000, C376S337000, C137S079000, C137S078100
Reexamination Certificate
active
06311897
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a passive pulse generator and to a method for activating a safety fitting in a nuclear power plant.
In a nuclear power plant which is equipped, for example, with a pressurized or boiling water reactor, cold coolant is fed to and heated coolant is discharged from a reactor pressure vessel in a closed circuit in a reactor safety vessel. The coolant is heated by core processes taking place in the reactor pressure vessel. Heat energy that is absorbed at the same time by the coolant serves for generating electric energy. At the same time, the heated coolant is cooled through the use of heat exchange processes and is fed to the reactor pressure vessel again. A leak in that closed cooling circuit leads to a reduction in the coolant and therefore to a temperature rise in the reactor pressure vessel. A temperature rise in the reactor pressure vessel also leads automatically to a temperature rise, for example in a condensation chamber, to which the reactor pressure vessel is connected for safety reasons. At present, however, a small leak in the coolant circuit is not detected. Instead, the coolant loss which occurs is compensated automatically by regulating a filling level of the reactor pressure vessel from existing coolant reservoirs. However, should a major coolant loss incident occur, in that case the temperature in the reactor safety vessel would be increased by the amount of the temperature rise due to the leak.
Published French Patent Application 2 690 219 discloses a safety fuse which releases a valve when a temperature is exceeded. The disadvantage of a safety fuse is that it is available only once and, after use, has to be replaced by a new one.
Published UK Patent Application GB 2 209 200 A discloses a thermal closing valve that, particularly in the domestic sector, is used for fire protection reasons in gas lines in which an easily flammable or explosive gas flows. The closing valve closes the gas line reliably and permanently when a specific temperature is exceeded. For that purpose, a special spring is provided and closing of the gas line is brought about by thermal expansion of the spring in reaction to a temperature rise. The spring is specially constructed so that the gas line still remains closed even when the temperature falls again. The spring therefore does not return to its initial position in the event of a lowering of temperature. On the contrary, it has to be replaced by a new spring, in order to ensure that the closing valve is operative again.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a reversibly operating passive pulse generator which reacts to a temperature change and a method for activating a fitting with a passive pulse generator in which a control pulse for the fitting is released as a result of a temperature change, which overcome the herein afore-mentioned disadvantages of the heretofore-known devices and methods of this general type.
With the foregoing and other objects in view there is provided, in accordance with the invention, in a nuclear power plant having a safety fitting and a pressure-carrying line connected to the safety fitting, a passive pulse generator to be connected to the line for activating the safety fitting, the passive pulse generator comprising a closure element for reversibly opening and closing the line; a first actuating element generating a force effect as a result of a thermal volume change of the first actuating element, the first actuating element supplying the force effect for actuating the closure element; and a locking device releasing actuation of the closure element by the first actuating element when the force effect caused by the thermal volume change exceeds a predeterminable value.
Therefore, in the event of a temperature change in the vicinity of the pulse generator, the result of the expansion or contraction of the first actuating element is that, for example, the closure element releases the pressure-carrying line. The medium, for example compressed air, which is located in the line, may then be used as a signal for a downstream fitting. This operation is reversible, so that the pulse generator can transmit a signal as often as desired, in order to initiate further steps, for example in order to rectify a coolant loss in a reactor safety vessel. The locking device is constructed in such a way that the value of the force effect beyond which the locking device is to be released can be set. The temperature beyond which the pulse generator is triggered and transmits a signal can consequently be set indirectly. An essential point for the safety requirements in a nuclear power plant is the passive functioning of the pulse generator. The pulse generator transmits a signal to a downstream fitting solely in reaction to a temperature change in the vicinity. No other external control signals, for example electric control signals, are necessary. The passive pulse generator is therefore fully operational even in the event of a complete power failure.
Devices which, in principle, have features similar to the pulse generator are known in various versions, for example from German Published, Non-Prosecuted Patent Application DE 195 17 655 A1 or from German Patent DE 40 21 580 C1. They are used, for example, in heating technology, as thermostats. However, those thermostats or valves differ fundamentally from the pulse generator in terms of both their functioning and their structure. They are therefore in no way suitable for use in the highly sensitive safety sectors of a nuclear power plant for activating a fitting and not even for achieving objects specific to power stations.
In accordance with another feature of the invention, the first actuating element is constructed as a memory pressure element. The advantage of a memory pressure element is that its thermal volume change commences essentially only beyond a specific temperature, but then virtually in a jump. Therefore, through the use of such a memory pressure element, the temperature beyond which the pulse generator is to be triggered can be set.
In accordance with a further feature of the invention, in the pulse generator, the first actuating element is held in a basic position by the locking device. The closure element is therefore exposed to a force effect only when the predetermined value for the temperature is exceeded. This increases the operating reliability and prevents the pulse generator from being triggered prematurely.
In accordance with an added feature of the invention, for the same purpose, the closure element is capable of being closed with an adjustable closing force through a second actuating element.
With the objects of the invention in view there is also provided a method for activating a safety fitting in a nuclear power plant with a passive pulse generator transmitting a signal through a pressure-carrying line to the fitting, which comprises generating a force effect from a thermal volume change of an actuating element in the pulse generator; actuating a closure element in the pulse generator with the force effect for reversibly opening and closing the pressure-carrying line; and releasing the actuation of the closure element by the actuating element with a locking device, when the force effect caused by the thermal volume change exceeds a predeterminable value.
In accordance with a concomitant mode of the invention, it is advantageous, in particular, to place a pulse generator, as described above, in a pressure chamber and/or condensation chamber of a nuclear power plant, so that the temperature, which has increased as the result of a coolant loss, in the reactor safety vessel and therefore also in the pressure chamber or condensation chamber, can be detected. It is particularly advantageous for the operation of a nuclear power plant, with a view to safety aspects, that the pulse generator be triggered passively. The pulse generator therefore releases the pressure-carrying line beyond a specific increased temperature, without additional co
Carone Michael J.
Greenberg Laurence A.
Lerner Herbert L.
Richardson John
Siemens Aktiengesellschaft
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