JPH02110399A - Automatic atomic reactor starting apparatus - Google Patents

Abstract

PURPOSE:To alleviate the load of an operator and to perform safe and efficient starting by computing the pulling amount of a control rod per unit time in response to the input amount of reactivity, and selecting a sequence corresponding to the pulling amount of the control rod from predetermined control-rod pulling sequences. CONSTITUTION:A reactivity-input-amount computing device 16 computes the reactivity of a core based on the distribution of neutron flux which is transmitted from a neutron-flux computing device 15. The input amount of the reactivity per unit time is computed and transmitted to a control-rod-pulling-amount computing device 17. The control-rod-pulling amount computing device 17 computes the pulling amount of the control rod per unit time. A sequence corresponding to said pulling amount is selected out of control-rod pulling sequences stored in a control-rod-pulling sequence memory device 19. The control-rod-pulling- amount computing device 17 transmits the control-rod pulling sequence to a control-rod-driving control device 20. A control rod 22 is pulled with a control- rod driving device 21. The control-rod pulling sequence is displayed for operators through an input/output device 18.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to an automatic nuclear reactor startup device.

(Prior art) Generally, when starting up a nuclear power plant, such as a boiling water nuclear power plant, the control rods are pulled out from the reactor core one after another to first bring the core to a critical state, and then shift to an output operating state. The method is to do so. The control rod withdrawal sequence at this time is predetermined based on the critical control rod pattern predicted by off-line calculation, and the operator withdraws the control rods according to this sequence.

At this time, the operator must keep the following in mind. In other words, the neutron flux increases when the control rod is withdrawn, but
This means that the rate of increase must not exceed a certain predetermined limit value. If the neutron flux increases beyond this limit, core control may be impaired and, in extreme cases, reactor shutdown may occur. Specifically, this is determined based on the reactor period (the reciprocal of the logarithmic rate of change of neutron flux) calculated from the readings of neutron flux detectors placed at various locations in the reactor core. For this reason, operators must judge the timing of withdrawing the control rods by measuring the reactor cycle. When the reactor reaches a critical state, the neutron flux increases at a constant rate depending on the reactivity of the reactor core, so operators pull out the control rods until the neutron flux reaches a predetermined value to achieve a critical state.

(Problems to be Solved by the Invention) However, the conventional nuclear reactor startup method described above has the following problems.

As shown in FIGS. 2 and 3, there are two types of neutron fluxes in the reactor core: a local power region detector (hereinafter referred to as LPRM) 1 and a neutron source region detector (hereinafter referred to as NSRM) 2. A detector is installed, but is it LPI? N 1
While NSRM 2 has more than 100 detectors installed to cover the entire core, NSRM 2 has only about 10 detectors installed throughout the core. In addition, in FIGS. 2 and 3, reference numeral 3.
4.5 indicates the fuel assembly, control rod, and neutron source, respectively.

On the other hand, in the low output region at startup as mentioned above, the L
Since PRMI does not play that role, N is used to measure the furnace cycle.
! Although a reading of 3RM2 is used, the neutron flux distribution at startup is extremely non-uniform spatially due to the high control rod density in the core.

Therefore, measuring the reactor period under such conditions requires information about the neutron flux throughout the reactor core, and the NSRM
There is a problem in that the reactor period measured only from the readings of No. 2 may include errors due to non-uniformity of the neutron flux distribution.

Furthermore, with conventional methods, it is not possible to monitor the response of neutron flux during control rod withdrawal and reactor cycle measurements, so it is not possible to monitor the response of neutron flux during control rod withdrawal or reactor period measurement. If the neutron flux suddenly increases due to an increase in

In addition, since control rod withdrawal is completely left to the operator's manual operation, the operator's workload is heavy and, especially in conditions approaching criticality, excessive withdrawal due to incorrect operation may occur.
It is also necessary to consider the possibility of an alarm occurring or a reactor trip, and there is also the problem that the mental burden placed on the operators is extremely large.

Therefore, the present applicant et al.
9982, proposed an automatic nuclear reactor startup system that can correct the above-mentioned drawbacks.

This automatic reactor startup system first calculates the input reactivity due to control rod withdrawal per unit time based on the appropriate reactor cycle and target reactivity given by the operator, according to the following formula.

(dR/dt) -K (Rt-R)...
・・・・・・・・・(1) However, (aR/dt): Input reaction rate R per unit time
1=target reactivity R: core reactivity X: control gain.

The reactivity of the reactor core in equation (1) is determined in the reactor automatic startup system as follows. That is, in a state of high subcriticality, the following relationship exists between the reactivity of the core and the total number of neutrons.

R--LS/n ・・・・・・・・・
(2) Where, n: total number of neutrons in the core L: neutron life of the core S: total neutron source strength, and the total number of neutrons in the core is given by the reading of N5RH.

Further, the control gain in equation (1) is determined as follows.

In a state with a large degree of subcriticality, Rt((-R, so 1,
Equation (1) can be approximated as follows.

(dR/dt) --KR (3) Therefore, if LS is considered constant, then equation (2) and (3)
), the control gain is given as follows.

K-(dn/dt)/n-(dlogn/dt)-1/
T ＋＋＋＋＋＋＋・(4) However, T: is the furnace cycle given by the operator.

Then, the control rod withdrawal amount per unit time is calculated from the above-mentioned input reactivity per unit time using the following formula, and is instructed to the operator.

(dN/dt) -v (dR/dt) ---
(5) However, (dN/dt) Amount of control rod withdrawal per unit time V: This is a conversion coefficient obtained by off-line three-dimensional calculation.

Since the above operations are automatically performed within the reactor automatic startup system, the operator's workload and mental burden are reduced. Also, in response to sudden reactivity injection into the reactor core,
Since the reactivity of the reactor core is always evaluated using equation (2),
It is possible to respond quickly. Furthermore, as can be seen from equation (4), if the control gain is kept constant, startup with a constant furnace cycle is possible, and by selecting an appropriate furnace cycle, efficient startup can be performed.

However, as mentioned above, in this automatic reactor startup system, the reactivity of the reactor core is evaluated using equation (2) based on the total number of neutrons given from the NSRM reading, so the reactivity of the reactor core is does not include information on the total number of neutrons in the core, and there is a problem in that it may contain errors due to non-uniformity in the neutron flux distribution.

The present invention has been made in response to such conventional circumstances, and is capable of automatically starting a nuclear reactor, which can significantly reduce the burden on operators compared to the conventional method, and also enable safe and efficient startup. The aim is to provide equipment.

[Structure of the Invention] (Means for Solving Notification 1) That is, the present invention provides an automatic nuclear reactor startup device that injects reactivity into the reactor core by withdrawing control rods, achieves a critical state, and increases neutron flux. , a neutron flux calculation device that calculates the neutron flux of the core based on readings from a core data measuring device and a physical model; and a neutron flux calculation device that calculates the total number of neutrons and reactivity of the core from the neutron flux calculated by the neutron flux calculation device. A reactivity input amount calculation device that calculates the reactivity input amount per unit time due to control rod withdrawal from this reactivity and the target reactivity, and a reactivity input amount calculation device that calculates the reactivity input amount per unit time by withdrawing the control rod. The present invention is characterized by comprising a control rod withdrawal total calculation device that calculates the control rod withdrawal amount per unit time and selects a sequence corresponding to the control rod withdrawal amount from predetermined control rod withdrawal sequences.

(Function) In the automatic reactor startup system of the present invention having the above configuration, the neutron flux of the reactor core is calculated using the readings of the core data measuring device and the physical model, and the total number of neutrons and the reactivity of the reactor core are calculated from this neutron flux. Then, the amount of reactivity input per unit time due to control rod withdrawal is calculated from this reactivity and the target reactivity.

Then, the control rod withdrawal amount per unit time is calculated according to this reactivity input amount, and a sequence corresponding to this control rod withdrawal amount is selected from predetermined control rod withdrawal sequences.

Therefore, the burden on operators can be significantly reduced compared to the conventional method, and the reactor can be started up safely and efficiently based on the reactivity of the reactor core, which is calculated from the accurate total number of neutrons in the reactor core. be able to.

(Example) Hereinafter, details of the automatic nuclear reactor startup device of the present invention will be described with reference to the drawings for one example.

FIG. 1 shows the configuration of an automatic nuclear reactor starting device according to an embodiment of the present invention, and in the figure, reference numeral 10 indicates a nuclear reactor.

Inside the reactor 10 are NSRMI 1 and core coolant?
A core data measuring device 12 is installed to measure core data such as lt amount, core pressure, core inlet coolant temperature, and control rod position. The signal is configured to be input to the reactor automatic starting device 14 via the data sampler 13.

The reactor automatic startup device 14 includes a neutron flux calculation device 15,
It is composed of a reactivity input amount calculation device 16, a total control rod withdrawal calculation device 17, and an input/output device 18.

The neutron flux calculation device 15 inputs the signal of the core data n1 constant device 12 transmitted from the data sampler 13, and calculates the neutron flux distribution using a built-in physical model. As a physical model used for such calculations, it is desirable to use a so-called -group coarse lattice point diffusion model, etc., in order to improve the responsiveness of the entire apparatus.

In the single group/coarse grid point diffusion model, the neutron flux satisfies the following equation.

Lφ+ Bφ−S'・・・・・・・・・
(6) Here, square matrix B is a finite-difference approximation of the φ2 neutron east distribution L nila plus operator: square matrix S' whose diagonal elements are material buckling: neutron source intensity distribution.

The neutron flux calculation device 15 uses a well-known method (for example, rM, Tsulkl, et al.
;'Convergence and Acceler
ation of Void 1terations
in Boiling Water Reactor
Core Calculattons, Nucl
, Sci. Eng., 64.724-732 (1977
) Calculate the neutron flux distribution using the method described in J.) and transmit it to the reactivity input amount calculation device 16.

The reactivity input amount calculation device 16 first includes the neutron flux calculation device 1
From the neutron flux distribution transmitted from No. 5, the total number n of neutrons in the core is calculated using the following formula.

n=j(w'φ/v) dr−(7) where V: neutron velocity v/, an arbitrary weighting function, and the integral is taken over the entire core.

The total neutron number calculated from equation (7) is based on the neutron flux distribution calculated by the physical model expressed by equation (6), and therefore includes information on the total neutron flux of the reactor core.

Next, the reactivity input calculation device 16 calculates the reactivity of the reactor core using the above-mentioned equation (2) from the total number of neutrons calculated from the equation (7). Furthermore, the reactivity input amount calculation device 16
From the reactor period given by the operator from the input/output device 18, the control gain is calculated using the above-mentioned equation (4), and from this and the above-mentioned core reactivity, the reactivity input amount per unit time is calculated as described above. It is calculated using equation (1) and transmitted to the control rod withdrawal total calculation device 17.

The control rod withdrawal total calculation device 17 calculates the control rod withdrawal amount per unit time using the above-mentioned formula (5) from the reactivity input amount per unit time transmitted from the reactivity input amount calculation device 16. , a sequence corresponding to this amount of withdrawal is selected from the control rod withdrawal sequences stored in the control rod withdrawal sequence storage device 19. Then, the control rod withdrawal total calculation device 17 transmits this control rod withdrawal sequence to the control rod drive control device 20, and
At the same time, the control rod 22 is withdrawn, and the control rod withdrawal sequence is displayed to the operator through the input/output device 18.

That is, according to the automatic reactor startup device 14 of this embodiment described above, it is possible to carry out efficient reactor cycle-constant start-up based on the reactivity of the reactor core calculated from the accurate total number of neutrons in the reactor core. In addition, it is possible to quickly respond to sudden reactivity injection into the reactor core. therefore,
The burden on the operator can be significantly reduced compared to the conventional method, and safety at startup can be significantly improved.

In the above example, the reading value of NSRMI 1 is not used at all, but by using this reading value, the accuracy of the neutron flux distribution calculated by the neutron flux calculation device 15, and therefore the total number of neutrons in the reactor core, can be improved. It can be further increased. In this case, instead of the neutron flux calculation device 15, the neutron flux distribution is calculated from the core data measurement device 12 that measures core data such as core coolant flow rate, core pressure, core inlet coolant temperature, and control rod position, and the readings of NSRMll. An apparatus for calculating , for example, an apparatus proposed in Japanese Unexamined Patent Publication No. 58-62595, etc. can be used.

[Effects of the Invention] As explained above, the automatic nuclear reactor startup device of the present invention enables efficient startup with a constant reactor period based on the reactivity of the reactor core calculated from the accurate total number of neutrons in the reactor core. It becomes possible. Furthermore, it is possible to quickly respond to sudden reactivity injections into the reactor core, greatly reducing the burden on operators and improving safety during startup.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an automatic reactor startup system according to an embodiment of the present invention, FIG. 2 is a top view showing the configuration inside the reactor core, and FIG. 3 is a side view showing the configuration inside the reactor core. . 10......Reactor 11...Neutron source area Neutron flux detector 1
2...Core data measuring instrument 13...
・・・・Data sampler 14・・・・・・Reactor automatic startup device 15・・・・・・Neutron flux calculation device 16・・・・・・Reactivity input amount calculation Device 7...
......Control rod withdrawal amount calculation device 8...
...Input/output device 9...Control rod withdrawal sequence storage device 0...Control rod drive control device 1...
... Control rod drive device 2 ... Control rod applicant Japan Atomic Energy Corporation applicant
Toshiba Corporation

Claims (1)

[Claims] (1) In an automatic reactor startup system that injects reactivity into the reactor core by withdrawing control rods to achieve a critical state and increase the neutron flux, the neutron flux in the reactor is calculated based on readings from a core data measuring device and a physical model. A neutron flux calculation device calculates the total number of neutrons and reactivity of the core from the neutron flux calculated by this neutron flux calculation device, and from this reactivity and target reactivity, the reaction per unit time by control rod withdrawal is calculated. A reactivity input amount calculation device that calculates the reactivity input amount, and a control rod withdrawal amount per unit time is calculated according to the reactivity input amount calculated by this reactivity input amount calculation device, and a predetermined control rod An automatic nuclear reactor startup device comprising: a control rod withdrawal amount calculation device that selects a sequence corresponding to the control rod withdrawal amount from withdrawal sequences.