JPH01126595A - Core performance monitoring apparatus - Google Patents

Abstract

PURPOSE:To enable calculation of a highly accurate burnup distribution in a short time, by computing a burnup distribution in the entire core based on an output distribution of a 1/4 core calculated with an output distribution calculator and a previous brunup distribution inputted from a memory. CONSTITUTION:An output distribution calculator 3 receives counts inputted from various measuring devices disposed in a reactor 1 and a burnup distribution inputted from a burnup distribution memory 5 to calculate an output distribution alone in an area a quarter of the core having a 1/4 symmetry based on a core 3-D physical model previously incorporated into the apparatus. A burnup distribution calculator 4 calculates a burnup distribution in the entire core with a fine a symmetry corrected in a fissile material load weight based on an output distribution of a 1/4 core calculated with the output distribution calculator 3 and a previous burnup distribution inputted from the burnup distribution memory 5. Then, the results of calculation are outputted from an operator's output unit 6.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a fuel loading pattern and a control rod pattern that are
The present invention relates to a core performance monitoring device for monitoring the core performance of a nuclear reactor having 74 symmetry.

(Prior art) Generally, in a nuclear reactor, it is required to obtain a highly accurate core power distribution in order to monitor whether the core is exhibiting the required performance while maintaining its health. Ru. When incorporating a three-dimensional core physical model into a process computer for the purpose of improving the accuracy of online monitoring of reactor core performance, an accurate burnup distribution is required to calculate the power distribution.

The burnup distribution represents the integrated power per unit weight of the heavy element uranium contained in the fuel assembly.

When the core is spatially represented by a set of many nodes, the burnup distribution of node n at time t1 can be expressed by the following equation using the burnup distribution at time to.

Eo (t+)=En (to)+/ [pi
<t)/wn] ctt...(1)t.

Here, En (t)... Burnup of node n at time vqt Pn (t)... Output Wo of node n at time t... Weight of uranium at the time of core loading of node n.

The fuel loading pattern of a nuclear reactor core is generally designed to have 174 mirror symmetry or 174 rotational symmetry. Therefore, if the control rod pattern also has similar symmetry, the core performance calculation time can be significantly shortened by performing calculations using the core three-dimensional physical model only in 174 core regions.

(Problem to be Solved by the Invention) However, even when the fuel loading pattern has 174 symmetry, the weight of uranium at the time of core loading at node n in equation (1) has a small difference due to errors in the manufacturing process. What it has is a back passage. The burnup distribution is a very important quantity in calculating the thermal limit value of the fuel and also in the management of heavy element isotopes, so this minute difference cannot be ignored, and conventionally it was It was not possible to obtain an accurate burnup distribution only by calculation in the core region of 4.

In addition, FIG. 4 shows an example of the difference in the bundle initial heavy element content and the difference in the bundle average burnup in an 800,000 KW class boiling water nuclear reactor with 174 mirror image symmetry. In this example, point A of locus (05, 10) at the mirror image symmetrical position, locus a (O5,
17) cy>B point, coordinates (22,10) no C point, (
The initial heavy element content of the bundle at point D at 22°11) is
172055 (1, 1719490, 1720 respectively)
87(], 171931(1), and the bundle average burnup is 175758 Wd/l and 17550 Wd/l, respectively.
MWd/l, 17555MWd/l, 175678
It is d/l.

The present invention has been made in response to this problem, and aims to provide a core performance monitoring device that can obtain highly accurate burnup distribution in a short time for a core with 1/4 symmetry. be.

[Structure of the Invention] (Means for Solving the Problems) The core performance monitoring device of the present invention includes a power distribution calculation device that calculates the power distribution of a 1/4 core region based on a three-dimensional core physical model; Based on the power distribution of the 1/4 core region calculated by this power distribution calculation device, the past burnup distribution, and the ratio of the weight of fissile material at the time of core loading, the symmetry of the core power is used to calculate the power distribution in the entire core. The present invention is characterized by comprising a burnup distribution calculation device that calculates a burnup distribution.

(Function) In the core performance monitoring device of the present invention, the power distribution calculation device inputs counts from various measuring instruments placed in the reactor and also inputs the burnup distribution from the burnup distribution storage device. Based on the core three-dimensional physical model built into the equipment, the core 174 has a quarter symmetry.
The burnup distribution calculation device calculates the fissionability based on the power distribution of the 1/4 core calculated by this power distribution calculation device and the past burnup distribution input from the burnup distribution storage device. By calculating the burnup distribution throughout the core with correction for small asymmetries in the material loading, it is possible to calculate an accurate burnup distribution in a shorter time than conventional methods.

(Example) Hereinafter, the present invention will be described in detail with regard to an example shown in the drawings.

FIG. 1 shows the configuration of a core performance monitoring device according to an embodiment of the present invention. A device 2, a power distribution calculation device 3 that calculates the power distribution in the core based on a three-dimensional physical model of the reactor core pre-built in the device, and a burnup calculation device 3 that calculates the power distribution in the core based on the power distribution calculated by the power distribution calculation device 3. A burnup distribution calculation device 4 that calculates the distribution, a burnup distribution storage device 5 that stores the burnup distribution calculated by the burnup distribution calculation device 4, and an operator output wave r that outputs the results of these core performance calculations. ! It consists of 16.

Next, the operation of the core performance monitoring device configured as described above will be explained with reference to the flowchart of FIG. 2.

First, the data input device 2 inputs plant data representing the current state of the reactor core from various measuring instruments installed in the reactor 1 (a).

Next, in the output distribution calculation device 3, the data input device 2
The power distribution of 174 regions (hereinafter referred to as problem regions) of the reactor core is calculated based on the core three-dimensional physical model from the core current data input from the reactor core and the burnup distribution stored in the burnup distribution storage device 5. (b).

After this, the burnup distribution calculation device 4 calculates the burnup increment in this region from the output distribution of the above problem region (c)
.

After that, the burnup distribution calculation device 4 calculates the coordinates of bundles at symmetrical positions other than the problem area (d), calculates the uranium weight ratio between the bundles in the problem area and these bundles at symmetrical positions (e), and Calculate the burnup increments outside the area f), and integrate the burnup of the entire core from these burnup increments (g).

Note that the burnup distribution calculation device 4 calculates the burnup distribution of the entire core from the power distribution of the 1/4 core as follows.

In the radial cross-sectional view of the reactor core shown in Figure 3, if n is a node at a mirror-symmetric or rotationally symmetrical position within the problem area indicated by diagonal lines of node m outside the problem area, then for node n inside the problem area, The output distribution P11 has been calculated, and the burnup increments δE and Q between time to and time t1 are (1)
From the formula, δE, =/ [P, (t)/VL] dt・
(2)t.

Therefore, the burnup distribution Efl(tl
) is given by the following equation.

Ea Ct+ ')=En (to)+δEl+
-(3) Here, the burnup distribution Eo(to
) is stored in the burnup distribution storage device 5.

On the other hand, since the output distribution P is not given for the node m outside the problem domain, if we substitute the output distribution P0 of the node at the symmetric position within the problem domain as a first approximation, then The burnup increment δE, is: δ E, =f [Pn (t)/w, dt ・<4)t.

Equation (4) is δB m = (wn/Wm) xf (Pn
(t)/Wn)at...(5)t.

Therefore, the burnup increment δE1 is finally expressed as δE@=(Wn/Wm)δEn=(6). Here, W, , W are nodes n, respectively.
This is the weight of uranium when loaded into the core.

Burnup distribution E of node m outside the problem area at time t1
−(t+) is Ea (tl) −Evs (t o )+δE,
−(7), so from equations (6) and (7), Ex
(t+)=E! l (t o ) +<Wf
l /Wm ) δEfi (8).

The contents of the burn-up distribution storage device 5 are updated with the burn-up distributions Efi and El calculated by the burn-up distribution calculation device 4 as described above.

The operator output device 6 displays the above core performance calculation results to the operator.

As described above, according to the core performance monitoring device of the present invention, when the core has 174 symmetry, even if the power distribution is calculated only in the 1/4 region of the core, it is possible to detect slight asymmetry in the uranium loading amount. Accurate burnup distribution over all considered cores can be calculated in a short time.

〔Effect of the invention〕

As is clear from the above explanation, according to the core performance monitoring device of the present invention, for a core having 1/4 symmetry,
The burnup distribution, which is extremely important for core performance monitoring and requires accuracy, can be calculated in a short time, making it possible to perform high-speed and highly accurate core performance monitoring.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a core performance monitoring device according to an embodiment of the present invention, FIG. 2 is a flowchart showing the operation of the core performance monitoring device shown in FIG. 1, and FIG. 3 is a radial cross-sectional view of the core. FIG. 4 is an explanatory diagram showing an example of a difference in bundle initial heavy element content and a difference in bundle average burnup. 1...... Nuclear reactor 3... Output distribution calculation device 4...
...Burnup distribution calculation device 5...Burnup distribution storage device Applicant: Japan Atomic Power Industry Co., Ltd. Applicant: Toshiba Corporation Representative Patent attorney Satoshi Suyama - Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) A power distribution calculation device that calculates the power distribution of the 1/4 core region based on a three-dimensional core physical model, and the power distribution of the 1/4 core region calculated by this power distribution calculation device and the past A reactor core characterized by comprising a burnup distribution calculation device that calculates a burnup distribution in the entire reactor core using symmetry of the core output based on the burnup distribution and the ratio of the weight of fissile material when loaded into the core. Performance monitoring equipment.