JPS60166892A - Steam relief valve - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a light water-cooled nuclear reactor (hereinafter referred to as a light water reactor), which uses a relief system to release steam generated by the decay heat of the core from the primary system to the outside of the system during reactor isolation. The present invention relates to a steam release method and apparatus suitable for removing decay heat related to valves, particularly after a nuclear reactor scram.

[Background of the invention]

An example of the conventional technology will be explained using FIGS. 1 and 2 as a means for removing decay heat generated in the reactor core during reactor isolation.
In the boiling water reactor (BWR) 2, as shown in Figure 1, secondary steam is discharged through a safety relief valve (S/RV) 5 installed in the main steam pipe 4 connected to the steam dome 3. By doing so, the pressure in the reactor pressure vessel (RPV) 6 is controlled and suppressed during reactor isolation or abnormal events.

This S/RV is composed of multiple valves (1100M
At the We plant, there are 18 valves), which are opened and closed in multiple pressure groups based on the measured RPV6 pressure.

Therefore, the above S/
Pressure is suppressed by opening all RV5 valves, and multiple S
Of /RV5, one valve with the lowest set pressure can discharge steam corresponding to the decay heat after scram, and it is possible to control the pressure of the primary system.

In the conventional example, a plurality of S/RV5s are all designed and manufactured with the same specifications and the same capacity, but the opening/closing set pressure of the S/RV5s differs depending on the valve.

On the other hand, in the pressurized wooden reactor (PWR) 7, a pressurizer 9 is installed in a part of the -order system loop piping, and this pressurizer 9 controls the pressure in the reactor pressure vessel 6 during normal operation and during abnormal operation. Control and suppress when an event occurs. For example, if the pressure in the primary system drops during normal operation, the heater 1 installed in the pressurizer 9
By heating at 0, the pressure of the primary system is returned to a predetermined pressure. On the other hand, when the pressure in the secondary system increases, the spray system 11 installed in the gas phase of the pressurizer 9 is operated to condense the steam, thereby maintaining the pressure in the primary system at a predetermined pressure. It becomes. Nevertheless, if the pressure rise in the secondary system cannot be suppressed, the safety valve 12 provided at the top of the pressurizer 9 opens and releases steam from the primary system, thereby controlling the pressure in the secondary system. I can do it.

As explained above, both the BWR 2 and the PWR 7 have sufficient pressure control in the primary system and have multiple control devices. However, in the event of a slow pressure increase such as a reactor isolation event, the capacity of the S/RV 5 and safety valve 12 is too large, and the valves must repeatedly open and close until the event is resolved. Ta. That is, as shown in FIG.
The pressure in PRV6 fluctuates as RV5 opens and closes. This is because when reactor 1 scrams, the amount of steam generated in the core is 3 to 1.5% of the rated operation (over a long period of 1 minute to 1 day after scram), but This is because the flow rate of blown steam is approximately 6% of the rated main steam flow rate.

The repeated opening and closing of S/RV5 is as shown in Figure 4.
The capacity of the accumulator 13, which is the driving source of the S/RV 5, was made large.

[Purpose of the invention]

The purpose of the present invention is to be able to process steam of 1.5 to 3% of the rated main steam flow rate with one valve, and to provide a steam relief valve that lowers the blow-off setting pressure of the valve, thereby improving the efficiency of nuclear reactor isolation. The objective is to provide a good decay heat removal system that reduces furnace pressure fluctuations and repetitive valve operation.

[Summary of the invention]

The present invention focuses on the fact that the decay heat during reactor isolation is about 3 to 1.5% of the rated main steam flow rate for a long period after the reactor scram. This system is designed to exhaust steam from the primary system.

In a preferred embodiment of the present invention, the steam blowout flow rate of one or two valves having the lowest set pressure among a plurality of S/RVs connected to the RPV gas phase section is reduced, and the blow-off set pressure is reduced. The system reduces the pressure to around 600 to 900 psia.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG.

(1) The reactor system according to the present invention consists of the RPV6 and the RPV6 as shown in FIG.
A main steam pipe 4 connected to the steam dome 3 at the top of the PV 6 and a main steam isolation valve (MSIV) installed in the main steam pipe 4
) Consists of 14. During reactor isolation, MSiV
14 is closed and heat removal in the turbine and condenser is no longer possible, the reactor is scrammed and the steam generated by the decay heat of core 1 is transferred to multiple S/RV 5s installed upstream of MSIV 14. is led to the pressure suppression pool 15 via the pressure suppression pool 15.

The present invention relates to this S/RV, and is a steam relief valve 16 whose blowout/stop pressure, blowout capacity, and number of valves are shown in Table 1.

That is, the dead-end pressure of the S/RV that blows out at the lowest set pressure is lowered to 600 to 800 psia, and the blowout capacity per valve is set in the range of 1.5 to 3% of the rated main steam flow rate (
100-200 ton/h in 1100 MWe plant
r valve).

The operating mechanism of the steam relief valve 16 of the present invention is as shown in FIG.
This is basically a dynamic system compared to the conventional example, and by switching the three-way solenoid valve 17 in response to the RPV6 pressure high signal, the steam relief valve 16 is opened in conjunction with the action of the spring 19 of the steam relief valve 16.

On the other hand, the RPV6 pressure is set to 600 to 900 p in advance.
When the pressure value set in the range of sia is reached, the steam relief valve 16 is closed by switching the three-way solenoid valve 17 again. At this time, the driving gas for operating the steam relief valve 16 is
In the present invention, the capacity of the accumulator 13 can be reduced by reducing the S/RV5 operation frequency, which will be described later.

(2) Contents of the present invention As shown in Table 1, the present invention provides a relief valve 16 with a minimum set pressure.
In the case of a 1100 MWe BWR2 plant, the capacity will be as follows so that steam generated by decay heat can be discharged with one valve.

Steam flow rate: 100-200 t; on/hr
・Valve minimum flow path area: 0.03 to 0.06 ft" Blowout pressure: 1084 psia Blow-off pressure: 600 to 900 psia In addition, the present invention can replace the steam relief valve 16 with the above specifications with one or two valves, with the conventional capacity S/ It is characterized by being built into the RV5.

(3) Results of Examples FIG. 5 shows plant behavior during an abnormal event in an example adopted in the present invention.

Since the present invention employs a small-capacity steam relief valve 16 that processes steam equivalent to decay heat, the reactor pressure is maintained at a substantially constant pressure as shown in FIG.

For this reason, the frequency of opening and closing of the S/R'V 5 is reduced, improving the reliability of the valve, and reducing the frequency of opening and closing of the S/R'V 5.
capacity can be reduced.

As a modification of the present invention, as shown in FIG. 6, a flow rate limiting orifice 21 can be installed in the downstream piping of the S/RV 5 in an existing plant to appropriate the flow rate of the blown steam.

〔Effect of the invention〕

According to the present invention, the number of S/RV operations during reactor isolation can be significantly reduced, so it is possible to improve the reliability of the valve and reduce the capacity of the 7 cumulator.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a conventional example of BWR, Fig. 2 is a diagram showing a conventional example of PWR, Fig. 3 is a diagram showing plant behavior during an abnormal event in the case of conventional BWR example, and Fig. 4 is a diagram showing a conventional example of PWR. FIG. 5 is a diagram showing the operating mechanism of the S/RV, FIG. 5 is a diagram showing plant behavior at the time of an abnormal event in the case of the embodiment, and FIG. 6 is a diagram showing a modification of the present invention. l...Reactor core, 2...Boiling water reactor (BWR), 3
... Steam dome, 4... Main steam pipe, 5... Safety relief valve (S/RV), 6... Reactor pressure vessel (RPV)
, 7... Pressurized wooden reactor (PWR), 8...-secondary system loop, 9... Pressurizer, 10... Heater, 11...
・Spray system, 12...Safety valve, 13...Accumulator, 14...Main steam isolation valve (MSIO), 15
... Pressure suppression pool, 16... Steam relief valve, 17.
...Gas exhaust valve, 18...Gas supply valve, 19...Spring, 20...AC system, 21...Flow rate control orifice. To ゝ, O3 Funeral 3 figure ratio ω figure (B) MS Shimo 5 figure

Claims (1)

[Claims] 1. During reactor isolation of a light water reactor or during an abnormal event, steam generated by decay heat after reactor scram is transferred from the gas phase space of the primary system of the light water reactor. A steam relief valve characterized by opening and closing in response to a process amount signal such as the pressure of the secondary system or the amount of coolant when discharging the steam. 2. In claim 1, 1 of the steam generated during reactor rated power operation generated by decay heat after scram
．． A steam relief valve characterized by having at least one valve having a capacity to discharge 5 to 3% of steam at near reactor operating pressure. 3. A steam relief valve according to claim 1, characterized in that the minimum constricted area of the relief valve is in the range of 0.03 to 0.06 ft''. 4. In claims 1, 2, and 3,
The opening and closing of valves is controlled by the pressure of the reactor-subsystem, and at that time, multiple valves are opened and closed within pressure ranges divided into several groups,
In particular, a steam relief valve that opens at the lowest set pressure has a lower dead-end pressure than other groups. 5. The steam relief valve according to claim 4, characterized in that the set pressure for opening and closing of the relief valves divided into groups is set to the following. Valve group Number of valves Opening pressure Dead end pressure Minimum set pressure 1 valve 1084 psia 600~900 psia 2nd group Multiple valves 1094 psia 1018~1
061061p 3rd group multiple valves 1104psi
a 1027~1071 psia 4th group multiple valves 1114 psia 1036~1080 psia