JPS63135669A - Relief valve - Google Patents

Abstract

PURPOSE:To prevent repeated stress from exerting a specific relief valve, by changing the set pressures for at least two of a plurality of relief valves, including an actuated relief valve each time when one of the relief valve is actuated. CONSTITUTION:There are provided a set pressure value memory device 10 which stores therein set pressure values corresponding to relief valves 3 with respect to relief valve actuating logic 5, and a set pressure exchanger 11 for exchanging set pressure corresponding to the relief valves 3 each time when arbitrary one of them is operated. Estimating that a first system relief valve is actuated as the arbitrary relief valve, the exchanger 11 receives an operation signal for the first system relief valve, and shifts a set pressure P1 corresponding to the first system to another system such as, for example, a second system. Similar shifts are successively carried out for the other systems so that the set pressures for all relief valve systems are substituted.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a relief safety valve for a system that discharges fluid inside a pressure vessel to the outside of the system and suppresses a rise in pressure, and is particularly applicable to repeated discharges of fluid. The present invention relates to an operation logic of a safety relief valve suitable for avoiding concentration of stress on a particular relief valve.

[Conventional technology]

An example of the prior art will be described with reference to FIGS. 6 to 8, with reference to a relief safety valve installed in a boiling water nuclear reactor.

In the conventional technology, as shown in FIG. 6, the steam generated in the reactor pressure vessel 1 is released to the outside through the main steam piping via the main steam flow rate restrictor 12 and the main steam isolation valve 13. . On the other hand, if the main steam isolation valve 13 is intentionally stopped due to abnormal transient changes during operation, the pressure within the reactor pressure vessel may increase. In order to maintain the safety of the plant even when the pressure increases, a system is provided to release the steam inside the reactor pressure vessel 1 to the outside of the system and suppress the pressure increase. When the pressure increases, a relief safety valve 3 provided in the main steam pipe 2 opens and releases steam via a quencher 17 into a suppression chamber 16 located below a dry well 15 that constitutes a reactor containment vessel 14.

Generally, these safety relief valves 3 are connected to a plurality of main steam pipes 2.
There are multiple locations distributed throughout the area.

The function of the safety relief valve is shown in Figure 7. In this example, the number of safety relief valves is four, each having a different operating pressure setting.

The relief safety valve 3 has three types of operating functions.

That is, upon receiving a pressure signal from a pressure gauge 4 provided in the steam phase portion of the reactor pressure vessel 1, a predetermined set pressure (Pz to P4) is determined.
Relief valve operation logic 5 that opens electrically when exceeding
When the pressure further increases (P5 to PB), a spring-driven safety valve function 6 provided in the relief safety valve itself is activated to release steam. Furthermore, a signal is received from the water level gauge 7 installed in the reactor pressure vessel 1, and the water level signal is set to the set value (LL
), an automatic pressure reduction system operation logic 8 is provided which operates a specific relief safety valve 3 via a time delay logic 9.

Among these operating logics, automatic pressure reduction system operating logic 8 is provided assuming a coolant loss accident, and unlike the above two operating logics, it is used during the plant life except for planned operations. Also, the set pressure of the safety valve function is set higher than that of the relief valve function, and it is rarely used.

An example of the operation of the safety relief valve is shown in Fig. 8. In this figure, the same relief safety valve configuration as in Figure 7 is adopted, and it is assumed that the time after the accident is O and the main steam isolation valve 13 in Figure 6 is suddenly closed. With the sudden closing of main steam V1 separation valve 13,
The reactor pressure is rated P.

It rises rapidly from With this sudden increase in reactor pressure.

All relief safety valves open from set pressure P1 to P4,
Releases large amounts of steam (maximum Qa). If a large amount of steam is released, the reactor pressure will also drop and all safety relief valves will close. After that, the steam generation inside the reactor pressure vessel decreased, but did not reach zero.

After time TI, only the relief safety valve with the lowest set pressure Px operates. This minimum set pressure relief safety valve operates repeatedly over a long period of time until the plant is brought to a cold shutdown. That is, in the conventional technology, since the set pressure of each safety relief valve is fixed, the safety relief valves that operate during the life of the plant are concentrated in the system with the lowest set pressure. This results in excessive mechanical and thermal cyclic stress on the lowest set pressure relief safety valve system. For example, in a typical WR plant, the number of activations of the lowest set pressure relief safety valve is expected to be more than 10 times that of other set pressure relief safety valves5. The design value of the suppression chamber 16 shown in FIG. 6 is determined by the maximum number of activations of the safety relief valve, and therefore a very large five-point scale is required.

C Problems to be Solved by the Invention] In the above-mentioned conventional technology, since the operation of the relief safety valve, which is expected to be experienced during the life of the plant, is concentrated in a specific valve, from the viewpoint of ensuring plant safety, the relief safety valve is There has been a tendency for strict requirements to be placed on system and suppression chamber design.

However, relief safety valves other than the above-mentioned specific valves are not subjected to that much stress, and if these valves are manufactured using the same design standards, a significant imbalance will occur between the stress actually applied and the design standards. It turns out.

An object of the present invention is to provide a relief safety valve that prevents repeated stress from concentrating on a specific relief safety valve due to selective activation, and disperses the stress among a plurality of relief safety valves, thereby increasing safety. .

[Means for solving problems]

In order to achieve the above object, the present invention has developed a system of relief safety valves consisting of a plurality of relief valves that release mutually different set pressures to the extent that the pressure inside the container exceeds the pressure, and release the fluid inside the pressure container to the outside of the system. and a set pressure value memory for storing set pressures corresponding to the multiple relief valves, and settings corresponding to at least two relief valves including the relief valve activated each time one of the plurality of relief valves is activated. The present invention provides a relief safety valve equipped with a set pressure exchanger for exchanging pressure within the set pressure value memory.

However, if the 1111 number of relief valves include a relief valve that operates in response to changes in the level of the fluid in the pressure vessel, the set pressure value should be changed in consideration of the reliability required for this valve. Store it in an external dedicated memory area.

[Effect]

In the present invention, the relief valves with the lowest set pressure, which are expected to operate most times during the life of the plant, are prevented from concentrating in a specific system by the following method.

That is, assuming that the first system operates as an arbitrary (usually the lowest set pressure) relief safety valve.

The exchanger receives the activation signal of the relief safety valve of the first system,
The set pressure Pz for the first system is set for the other systems.

For example, a similar transfer to the second system is sequentially executed for other systems to replace the set pressure of the entire relief safety valve system. When the reactor pressure rises again and reaches the minimum set pressure, the safety relief valve system that operates here becomes the second system.

With this method, the number of times the safety relief valve operates during the life of the plant is averaged among the individual safety relief valves, and concentration of operations in a specific safety relief valve system is suppressed.

〔Example〕

The system configuration of an embodiment of the safety relief valve according to the present invention is shown in FIG. 1.
This is installed in the main steam piping 2 that carries the steam generated in the system out of the system. Its operation logic includes receiving the signal from the water level gauge 7,
An automatic pressure reduction system logic 8 that opens the valve after a time delay logic 9, a safety valve function 6 that opens when the spring of the relief safety valve comes off as the pressure rises, and a relief valve operation logic that opens upon receiving the signal from the pressure gauge 4. There are 5.

The device of the present invention is different from the conventional example in that the relief valve operation logic 5 includes a set pressure value memory 10 that stores the set pressure values corresponding to nine individual relief and safety valves 3, and a set pressure value memory 10 that stores the set pressure values corresponding to the relief valve operation logic 5. The point is that a set pressure exchanger 11 is provided for exchanging the set pressure value corresponding to the relief safety valve 3.

FIG. 1 shows a state in which 5RV (relief safety valve) group 1 having a set pressure P1 is activated, and the set pressure combination for the second operation is inputted to the relief valve operation logic 5 by the set pressure exchanger 11. .

When the pressure in the reactor pressure vessel 1 rises again, SRV group 2, which has the lowest set pressure, is activated. In this way, a similar replacement is performed each time a safety relief valve is operated, and the operation is not concentrated on a particular safety relief valve.

Note that in this embodiment, the set value of the set pressure P4 for the relief safety valve is not replaced. I mean.

This is because the relief safety valve for the set pressure P4 is provided exclusively for the automatic pressure reduction system logic 8, and frequent activation by the relief valve operation logic 5 must be suppressed based on the setting request standard.

FIG. 2 shows a specific embodiment in which the operation logic of the above embodiment is achieved using an electric circuit.In this embodiment, electricity is supplied to the equipment through the U phase and the P phase. The pressure signal is distributed from PAL to PA4 of comparator 18 via the P phase. When the pressure signal exceeds the set value P1, the comparator 18 P
AL becomes energized and activates Pl of relay 20. With the activation of R1 of relay 20, P is turned on by its b contact.
A valve opening signal is sent to the relief safety valve via the VI, and.

Power is supplied to the multiple/multi-contact switch 19 through the a contact. When this power supply ends, the multiple/multi-contact switch 19 switches from contact 1 to contact 2, causing each relay 20 to exchange the corresponding set pressure. A similar exchange is performed each time the safety relief valve is activated. The L phase is a water level signal, which together with the LAI of the comparator 18 and the time delay logic 9 constitutes an automatic pressure reduction system logic.

In addition, PA4 of the comparator 18 is the multiple/multi-contact switch 1.
Regardless of the operation of relay 9, it always operates in correspondence with relay 20 R4.

FIG. 3 shows an embodiment in which the embodiment shown in FIG. 1 is constructed using an electronic circuit.

The signal of the pressure gauge 4 or the signal of the water level gauge 7 is selected by the 1 selection gate circuit 21, and sent to the CPU 2 via the A/D converter 22.
4 is input. The CPU 24 compares the set pressure value or set water position stored in the RAM with the input signal, and outputs a valve opening signal 0/C. At the same time, a signal S corresponding to the corresponding valve is output. This signal S is sent to the proportional counting gate circuit 27 via the D/A converter 26. The AND circuit 28 receives the output of the proportional counting gate circuit 27 and the valve opening signal 0/C, and sends the valve opening signal to the corresponding relief safety valve. Also,
Each time any relief safety valve opens.

The setting values stored in the ROM 23 are sent to the RAM 25 via the CPU 24, and the setting values are exchanged. The reception and delivery of signals from the proportional counting gate circuit, RAM, ROM, etc. and the output of signals S and O/C are performed in synchronization with the clock signal of the CPU 24.

A flowchart of the above calculation process is shown in FIG.

In step A, all relief safety valves (in this example,
For 1 to 4), steps B to J are assigned. In step B, set CLOCK=O,
Input pressure signal P. In step C, the pressure signal P is compared with the corresponding set pressure P(I) (I = 1 to 4), and if one condition is satisfied, in step D, the relief safety valve is flagged to open. In step E, steps F to H are performed for valves other than relief safety valve 4.
Bypass. Step F sets CLOCK=1,
Input the water level signal. In step G, the water level signal is compared with the corresponding set water level L (I), and if one condition is satisfied, in step H, a flag is set to open the valve, taking into account the time delay. In Step E, the signal S and the valve open signal ○/ of the relief safety valve with the valve open flag set are
Output C. Finally, if the valve open flag due to the pressure signal is canceled in calculation J, it means that the operation of the relief safety valve has ended, and the set pressure is replaced in step K, that is, it is read anew from the memory. .

The effect of the present invention is shown in FIG.

In the figure, the relationship between the number of actuations of the safety relief valve and the number of years of plant operation for SRV groups 1 to 4 is shown for the present invention and the prior art.

The set pressure increases according to SRV groups 1 to 4.

In the prior art, the number of activations of SRV group 1 was significantly increased. For this reason, if we define the number of operations at Y1, the end of the plant life, as Nx with a margin, we get
In the present invention, the operation of SRV group 1 is distributed to SRV groups 2 and 3.

It will drop to Nl. N1 and N2 are the number of times the safety relief valve operates during the life of the plant, including a design margin, and are approximately related to each other by the following linear equation.

ni: Number of safety relief valves with set pressure i ml: fi Number of times the relief safety valve with constant pressure i operates during the plant life n The number of times the safety valves are operated is averaged to about 1/3 to 115, and all relief safety valves can be operated more uniformly.

Although the safety relief valve for a BWR has been described here, the present invention is applicable to relief safety valves for any pressure vessel. In addition, 1 operation logic considers the safety of the system,
Needless to say, multiple designs may be used.

〔Effect of the invention〕

According to the present invention, a specific drop-off safety valve can be selectively operated to prevent repetitive mechanical and thermal stress from being concentrated on the valve. Furthermore, since the number of activations of the safety relief valve is averaged, the life span of the valve, ie, the replacement cycle, is significantly extended. Furthermore, in order to carry out the present invention, there is no need to make major changes to the system, and only the logic of the control system needs to be changed, so it is easy to backfit not only plants to be constructed in the future but also existing plants.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the system configuration of one embodiment of the relief safety valve according to the present invention, FIG. 2 is a diagram showing the configuration of a specific embodiment in which the operation logic of FIG. 1 is realized by an electric circuit,
The figure also shows a specific example realized using an electronic circuit.
FIG. 4 is a flowchart showing the arithmetic processing of the device shown in FIG.
Figure 5 is a diagram showing the effect of the safety relief valve of the present invention in comparison with a conventional example, Figure 6 is a diagram showing the system configuration of a boiling water reactor as an example of setting a safety relief valve, and Figure 7 is a diagram showing a conventional safety relief valve. FIG. 8 is a diagram showing an example of an event in which the reactor pressure increases. 1... Reactor pressure vessel, 2... Main steam piping, 3...
・Relief valve, 4...Pressure gauge, 5...Relief valve operation logic, 6...Safety valve function, 7...Water level gauge, 8...
・Automatic pressure reduction system operation logic, 9... Time delay logic, 10... Set pressure value memory, 11... Set pressure exchanger, 12... Main steam flow rate restrictor, 13... Main steam isolation Valve, 14... Reactor containment vessel, 15... Drywell, 16... Suppression chamber, 17...
Quencher, 18... Comparator, 19... Multiple/multi-contact switch, 20... Relay, 21... Selection gate circuit, 22... A/D converter, 23-ROM, 24...
CPU, 25/RAM,) eS...D/A converter, 2
7... Proportional counting gate circuit, 28... AND circuit.

Claims (1)

[Scope of Claims] 1. In order to suppress the pressure increase in the pressure vessel, a plurality of relief valves open mutually different set pressures to the extent that the pressures exceed the pressures, and release the fluid in the pressure vessel to the outside of the system. a set pressure value memory that stores a set pressure corresponding to each of the relief valves; and at least two relief valves including a relief valve that is activated each time one of the plurality of relief valves is activated. A relief safety valve comprising a set pressure exchanger for exchanging a set pressure in the set pressure value memory. 2. In claim 1, the plurality of relief valves include a relief valve that operates according to a change in the liquid level of the fluid in the pressure vessel, and the set pressure value memory includes a relief valve that operates according to a change in the liquid level of the fluid in the pressure vessel. A relief safety valve characterized by comprising a dedicated memory area that is not subject to replacement in order to hold a set pressure value.