JPS58129386A - Emergency shutdown device for bwr type reactor - 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 The present invention relates to a boiling water nuclear reactor OII sudden stop device,
The scram mechanism is optimized for use in nine cases, and a sudden stop device is installed.

Figure 1 shows a boiling water source reactor V-stem OS 11, in which a reactor core 11, a seed pump 3, a steam separator 4, and a leakage dryer S are installed in the pressure volume 111, and the water in the vessel 11 is is circulated by a recirculation pump 2. The air generated here is sent to the turbine 6, condenser 7, and condensate pump 8, sent to the feed water heater 9, heated, and sent to the reactor core again by the feed water pump IOK. That is, during normal operation, the cooling water condensed in the condenser 7 is extracted from the turbine 6 and heated by steam in the feed water heating 1) 9, and then pumped into the pressure vessel 11 by the feed water pump 10. Water is provided.

However, if the function of the P water heater 90 is lost due to a failure of the 411 unit, the cooling water with a low temperature of O becomes a pressure vessel! Water is supplied to reactor 11, and positive O void reactivity is applied to the rounding where the void volume decreases in the reactor core l, increasing the output. This event is called feedwater heating loss.

When this loss of feed water heating occurs, the reactor output becomes abnormally high. Therefore, in conventional boiling water basin reactors, the heat flux on the fuel cladding surface is determined from the measured value of the neutron flux in the reactor core. An interlock is provided that scrams the reactor (emergency shutdown) if the value exceeds a set value.

Figure 2 shows the decrease width ΔMCPH of the heat flux on the surface of the fuel cladding tube and the minimum critical power ratio MCPH when loss of feedwater heating occurs.
It shows the change in the heat flux Q (neutron chain measurement signal with a first-order delay ll
! The output of the thermal output monitor (TPM), which is converted into a signal equivalent to heat flux through the heat flux, increases, and when this exceeds its set value, the reactor scrams.

On the other hand, due to the increase in heat flux, the minimum output ratio decreases by Δ
MCPR increases and becomes severe when scrumming and running. The maximum value of this ΔMCPR is, for example, about 0.15.

In this case, the neutron flux is below the set value of the neutron flux high scram, and no scram occurs due to the neutron flux high signal.

ζHere, the allowable value of MOPR stored during operation, that is, the operating limit MCPR, is the maximum value of MOPR for events in which the maximum value of jMcPRo is large among all abnormal transient change events that occur in the reactor. Safety limit MOPR (LO7)
determined by adding In a conventional nuclear reactor, the maximum value of ΔMCPRO when loss of feed water heating occurs is:
Other events, such as rounding that is smaller than the maximum MCPR value (for example α21m degrees) when a generator load shedding occurs,
The conventional 'I' PM scram interface was used as the scram interface that operated when a loss of feed water heating occurred, and no problems occurred.

However, as a recent trend, the maximum value of OjMcPR when an abnormal transient change occurs is being reduced by adopting a high-speed scram mechanism that increases the control rod insertion speed of the atomic desk. However, the scram caused by the TPM signal when loss of feed water heating occurs is to scram when the heat flux exceeds the set value (set to a slightly lower value than the value of heat ILWL corresponding to the safety limit MCPH). ,
Even if a high-speed scram mechanism or the like is adopted, the maximum value of jMcPH at the time of loss of feed water heating does not decrease.

Therefore, the maximum value of ΔMCPR at the time of loss of feedwater heating is the largest among all events, and there is a possibility that the operating limit MOPR is determined by the maximum value of ΔMCPH at the time of loss of feedwater heating. The safety margin for fuel integrity in the event of an occurrence is reduced, creating a problem with the safety of the reactor.

The purpose of the present invention is to reduce the maximum value of AfCPH when loss of feed water heating occurs, and to reduce the safety limit MCP when abnormal transient changes occur.
An object of the present invention is to provide an emergency shutdown device for a boiling water #Ii nuclear reactor that can further improve fuel integrity by increasing the margin for R.

In order to couple the above objectives, in the present invention, the phenomenon of loss of feedwater heating progresses gradually over time, or the loss of feedwater heating is detected by the cooling water temperature at the outlet of the feedwater heater. Focusing on the property that it is possible,
The set value for feed water heating loss is set to a smaller value than before.
When this setting value is used for a long time when the heat flux is in a good condition,
Alternatively, the reactor scram is performed under the conditions that the heat flux exceeds this set value and the feedwater heater outlet temperature is below a certain set value.

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 3 shows an embodiment of the present invention, in which the output Q of a thermal output monitor (TPM) 12 is applied to a scram mechanism 14 via a timer 13 to control a control rod 15. . And the conventional TPM system is TPM1
When the output signal q of No. 2 exceeds, for example, 120% of the rating, a scram is started, but in this embodiment, the setting value for the TPM output signal is set lower than before, and further,
When the signal Q from the TPM 12 exceeds the set value and the timer 13 confirms that the exceeded state has continued for a certain set time or more, the scram mechanism 14 starts a scram. In this way, by using the timer, it is possible to prevent an event other than loss of feed water heating from occurring when the TPM output signal stage fixed value is lowered, or an erroneous cycle time that occurs due to the TPM output output signal stage 1111. Prevents start-up and reliably scrams against gradual loss of feed water heating. Moreover, if the setting value of the TPM output signal stage is, for example, 110% of the rating (100%) and the time setting value of the timer is 10 seconds, the scram when the feed water heating loss occurs, as shown in Figure J14. The starting time starts from the conventional A point to the A point with a short elapsed time,
Along with this, the reduction width jMcPR of the minimum ocular field output ratio is also reduced by about half BK from the conventional B.

Figure 5 shows another embodiment of the present invention, in which the temperature detected by the temperature needle 16 provided at the outlet pipe of the feed water heater is below a certain set value, and the output signal of the TPM 12 is set to O. An interlock is provided in which an AND circuit 17 detects that the limit has been exceeded, and a scram occurs when this AND condition is satisfied. As the setting value for the TPM output signal, a smaller value (compared to the conventional O value) is adopted.

In the device of this embodiment, if the O set value for the TPM signal is set to 110%, for example, from the conventional 120%, and the 0 set value for the temperature needle signal is set to, for example, a value lower than the temperature during normal operation by 30, then Even if the temperature at the feedwater heater outlet is normal, even if n.

(Depending on the cause) Even if the PM output compensation code Q#110% or more, it will not operate, and this device will only operate in response to loss of feed water heating. For example) even faster <16% minimum output ratio reduction width MC
Conventionally, the maximum value of PH can be set to about 0 1/311 degrees.

In addition, with the above-mentioned apparatus of the present invention, it is not possible to deal with causes other than loss of heating of the water supply, so it is necessary to provide a separate system for these problems.

As explained above, according to the present invention, it is possible to greatly reduce the maximum value of 9VaO MOPR when feedwater heating loss occurs in the atom, and it is possible to significantly reduce the maximum value of MOPR when feedwater heating loss occurs, and to improve fuel integrity when feedwater heating loss occurs. The safety margin can be significantly increased. Furthermore, if the high-speed scram mechanism mat and the device of the present invention are used together, various abnormalities will occur in the reactor, the safety margin for the nine VaO fuel integrity will be improved overall, and the financial and economic aspects of the boiling water reactor will be improved. It has a great effect on sexual modification.

[Brief description of the drawings] No. 1111 is a schematic system diagram of a boiling water basin nuclear reactor system, No. 2 Ill is an explanatory diagram of scram operation when loss of feed water heating occurs,
FIG. 3 is a diagram showing one embodiment of the present invention, FIG. 4 is an explanatory diagram of one embodiment of the embodiment of FIG. 3, and FIG. 5 is a diagram showing another embodiment of the present invention. 9... Water supply heater, 12... Heat output electrician, 13.
··sea bream! , 14... Scram mechanism, 15... Control rod, 16-4.

Claims (1)

[Scope of Claims] 1. First means for determining whether the boiling water 11j [child-〇 heat output exceeds the nine threshold value set in advance and is a friend, and the reason why the heat output exceeds the above-mentioned value and a means for determining whether or not the loss of heating of the feed water is caused by a decrease in the temperature of the feed water to the reactor, and the heat output is determined to be the threshold value due to the loss of heating of the p feed water by the first and second means. The reactor is configured to make an emergency shutdown when it is determined that the
Emergency stop device for boiling water basin atomic P as IIIk. 2. A patent characterized in that the second means is constituted by a timer that determines that there is a loss of heating of the water supply if the state in which the thermal output exceeds the aforementioned value continues for a predetermined period of time or more. Boiling water basin atom-〇 emergency stop device as described in item 1 of the MS section of the claim. 3. The patented OS characterized in that the second means is constituted by a temperature detector that determines that the feed water has lost its heating when the feed water temperature falls below a predetermined value.
Boiling edema reactor o'ii according to No. 1a, sudden shutdown device.