KR100960788B1 - Fixed In-core Detectors in PWRs - Google Patents

Abstract

The present invention relates to a stationary measuring instrument of a nuclear reactor fixedly mounted within a nuclear reactor and measuring a neutron or gamma ray that changes in proportion to the nuclear power output distribution, and implements a rhodium measuring instrument, platinum measuring instrument and vanadium measuring instrument installed in the nuclear reactor in a multi-overlapping structure. It implements the overlap between the full length instrument and the partial length instrument of different lengths, and configures the position and length of the current value measuring logic to cope with the failure. By generating the output distribution of the area where is located, it increases the signal-to-noise ratio of the fixed instrument output signal of the reactor, it is possible to self-diagnose the failure of the instrument, and to improve the reliability and accuracy of the core protection / monitoring system It relates to a measuring instrument.

Reactors, Instruments, Rhodium, Vanadium, Platinum, Emitters, Electrical Field Instruments, Subfield Instruments, Superposition

Description

Fixed In-core Detectors in PWRs}

The present invention relates to a stationary measuring instrument of a nuclear reactor, and more particularly, to improve the core safety by improving the accuracy and reliability of the instrument used in the core protection and monitoring system, which is a system for monitoring / guaranteing the safety of the nuclear reactor. It relates to a stationary instrument of a nuclear reactor capable of measuring accurate neutron flux despite failure.

In general, the designer of a nuclear power plant calculates in advance the maximum permissible power that a nuclear fuel can withstand and provides the operator with information about the maximum permissible power. Ensure soundness is maintained.

In order to calculate the maximum allowable power, it is necessary to accurately measure the neutron output distribution in the reactor core. Thus, accurately measuring the neutron output distribution in the reactor core is very important in securing the stability of the reactor.

As such, the stationary instrument for measuring the neutron output distribution in the reactor core to ensure the stability of the reactor, as shown in Figure 2, the instrument assembly (1) and other support structures (2), cables (3), It consists of a connector 4 and signal measuring and processing equipment 5.

In general, rhodium (Rh-103), vanadium (V-51), platinum (Pt-195), and the like are used as an emitter material in a stationary measuring instrument of a reactor for measuring neutron flux in a core of a power plant reactor.

As shown in FIG. 3, in the case of the Korean standard nuclear power plant, instrument assemblies are installed in 45 nuclear fuel assemblies in a radial direction among all 177 nuclear fuel assemblies, and each instrument assembly is located at the center of the nuclear fuel assembly.

As shown in FIG. 4, five rhodium meters of the same length in the longitudinal direction are provided.

The rhodium meter is generated from fissile material and the neutron incident on the meter reacts with the rhodium isotope present as an emitter in the rhodium meter to emit beta particles and generate a current proportional to the neutron flux.

Rhodium has a high absorption cross-sectional area with respect to thermal neutrons, and the characteristics of the measurement signal are good.However, rhodium is continuously burned in response to neutrons, which reduces the signal output per neutron flux from the rhodium meter emitter. As it continues to decrease, the signal-to-noise ratio decreases, making accurate output distribution measurements impossible.

Therefore, the rhodium meter must be replaced when it reaches a point where output distribution measurements are not possible.

The lifetime of the instruments used in rhodium reactors is only 2 to 3 cycles (3 to 5 years). As a result, 15-20 replacements are required every cycle, which incurs enormous replacement costs.

In addition, even if a malfunctioning signal occurs due to a significant deterioration of the instrument's performance before the replacement cycle, the output distribution analysis of the core monitoring is performed until the actual measured value and the predicted value differ by more than 15% from those predicted by the nuclear design program. Problems that occur in the.

In the case of a neutron flux error signal measured higher than the normal output due to a malfunction of the rhodium meter, the local power distribution near the position of the meter is highly evaluated, thereby reducing the power plant operating margin.

Therefore, if the actual measured value of the nuclear design program shows a difference of more than 15% compared with the predicted value, the instrument will be treated as a failure and excluded from the output distribution evaluation, but it will be impossible to replace it until the plant prevents shutdown. There is a problem that the output distribution information cannot be provided.

Therefore, in order to solve such a problem, in order to extend the life of the rhodium meter, the emitter material is started for the meter of the reactor including platinum and vanadium to optimize the quantity, length and arrangement of the meter, thereby causing the problem of the rhodium meter. As shown in FIG. 5, the Westinghouse Co., Ltd. was composed of five platinum meters using platinum emitters and one vanadium meter using vanadium emitters to solve the signal delay of the rhodium meter. In order to increase the signal length of the platinum meter, the PASSEL meter was invented.

In other words, platinum (24 barns) and vanadium (5 barns), which have a lower neutron absorption cross-sectional area than rhodium, are used to reduce the combustion of the meter emitter material by neutron reaction, thereby extending the life.

At this time, the length of the longest platinum and vanadium meter is about 345cm, the length of the shortest platinum meter is about 90cm.

However, due to the low neutron absorption cross-sectional area of platinum and vanadium, the signal length of the neutron meter was found to be small. In addition, as shown in FIG. 6, Westinghouse Corp. solves the problem of low output signal of the vanadium meter. In order to reduce the length of five vanadium measuring instruments inserted into the same channel from the core electric field, the invention invented an OPARSSEL measuring instrument to obtain longitudinal output distribution by subtracting adjacent superimposed measuring instrument signals.

In the above-described PARSSEL and OPARSSEL measuring instrument disclosed by Westinghouse Co., Ltd., the overlapping structure is a signal of another measuring instrument located in the longitudinal direction of the same channel when one measuring instrument failure occurs among 4-5 vanadium or platinum measuring instruments. There is a problem that can not be used.

Accordingly, the present invention has been invented to solve the above problems, while improving the overlapping structure of the stationary measuring instrument of the reactor so that the accurate output distribution can be reconstructed even if a failure occurs in one instrument, but installed in the cylindrical reactor It is to provide a fixed measuring instrument of a nuclear reactor composed of current value measuring logic to properly determine the overlapping position of the plurality of measuring instruments in the instrument assembly in the longitudinal direction.

In order to achieve the above object, the present invention provides a fixed measuring instrument of a nuclear reactor,

A single full-length instrument 10 having a length of 150 inches, four sub-length instruments 20 having a length of 60 inches, and a sub-length instrument 20, 30 having a length of 90 inches, The 60-inch partial instrument 20 is installed downward to overlap each other by 30 inches, and the 90-inch partial instrument 20 is installed at a position spaced 30 inches apart from the upper side. It is installed at a position corresponding to the 90-inch partial instrument 30 and at the same time one full-length instrument 10 is installed on the side of the 60-inch partial instrument 20 is characterized in that the overlapping structure It is done.

In a preferred embodiment, the meters 10, 20, 30 have five longitudinal outputs p1, p2, p3, p4, p5 (40) installed at regular intervals in the longitudinal direction depending on their installation position and length. It is preferred to be configured to measure.

As described above, according to the stationary measuring instrument of the present invention, it has the function of increasing the signal-to-noise ratio of the output signal to the stationary measuring instrument of the nuclear reactor, and having the function of self-diagnosing the failure of the measuring instrument, the same channel in the event of a single instrument failure By using the superimposed instrument signal of, output distribution of the area where the faulty instrument is located has the effect of improving the reliability and accuracy of the core protection / monitoring system.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing a stationary measuring instrument of a nuclear reactor according to the present invention.

The technical constitution of the present invention is to determine the overlapping position in the longitudinal direction of a plurality of measuring instruments located in a measuring instrument assembly installed in a cylindrical reactor, and to configure the current value measuring logic which can cope with a failure.

In the present invention, the length of the instrument is configured to be at least 2 times to 5 times larger than that of a conventional rhodium instrument for the purpose of increasing the signal size of the instrument.

In other words, if the length of the measuring instrument is less than 2 times, the signal size of the measuring instrument cannot be increased, and if the length of the measuring instrument exceeds the maximum 5 times, the capacity of the measuring instrument assembly is limited, which is not preferable.

The present invention implements the logic for the self-diagnosis of the instrument, and is configured to have multiple overlapping structures so that the output distribution can be measured even when a single instrument fails in the same channel.

As shown in FIG. 1, in the preferred embodiment according to the present invention, the configuration of the longitudinally overlapping position of the instrument in the nuclear reactor core includes a full length instrument 10 and a plurality of partial length instruments 20 and 30. It consists of five longitudinal outputs (p1, p2, p3, p4, p5).

At this time, the full-length measuring instrument 10 in a preferred embodiment according to the present invention is made of a single piece having a length of 150 inches, the partial length measuring instruments (20, 30) is a partial length measuring instrument (20) consisting of four 60 inches of length ), And a partial meter measuring device 30 consisting of one 90-inch.

That is, four 60-inch sub-meters 20 in a single measuring instrument assembly are installed downwards so as to overlap each other by 30 inches with respect to the upper side, and one 90-inch sub-meter measuring unit 30 at the side thereof has an upper side. It is installed at a position spaced 30 inches apart from the reference, and installed at a position corresponding to the 90-inch partial meter 30 and at the same time one full-length instrument 10 on the side of the 60-inch partial meter 20 Is installed.

Each of the measuring instruments 10, 20, and 30 located in the measuring instrument assembly measures five longitudinal outputs 40 installed at an interval from the upper side downward, that is, at a predetermined interval in the longitudinal direction, depending on the installation position and length thereof. do.

Hereinafter, a, b, c, d, e, and f in the formula refer to current value measurements of the respective instruments 10, 20, and 30, and p1, p2, p3, p4, and p5 denote the current value measurements ( Mean longitudinal output 40 calculated using a, b, c, d, e).

Equation 1 is a relationship between the current value measurement (a, b, c, d, e) of the element for each meter and the output (p1, p2, p3, p4, p5).

a = p1 + p2 + p3 + p4 + p5

b = p1 + p2

c = p2 + p3

d = p3 + p4

e = p4 + p5

f = p2 + p3 + p4

The longitudinal outputs p1, p2, p3, p4, and p5 in the measuring instrument assembly are used to measure the current value measurement values a, b, c, d, and e of the full-length measuring instrument 10 and each of the partial-length measuring instruments 20 and 30. It is obtained by arithmetic operation.

Equation 2 is a normal measurement state (that is, a is healthy and f is not used for output measurement). In this case, the output distribution of p1 to p5 can be calculated without using f.

p1 = a-c-e

p2 = f-d

p3 = a-b-e

p4 = f-c

p5 = a-b-d

At least one measuring instrument in the measuring assembly is in a faulty state (Equations 3a to 3d) without using the measuring instrument in the failing state of the longitudinal outputs p1, p2, p3, p4, and p5 in the measuring assembly. The distribution can be calculated.

If instrument b fails

     p1 = a-c-e

     p2 = f-d

     p3 = d-f + c

     p4 = f-c

     p5 = c + e-f

If instrument c fails

     p1 = b + d-f

     p2 = f-d

     p3 = a-b-e

     p4 = e-a + b + d

     p5 = a-b-d

If instrument d fails

     p1 = a-c-e

     p2 = c-a + b + e

     p3 = a-b-e

     p4 = f-c

     p5 = c + e-f

If meter e fails

     p1 = b + d-f

     p2 = f-d

     p3 = d + c-f

     p4 = f-c

     p5 = a-b-d

Within the instrument assembly, it is possible to determine whether the single instrument i is out of the 60-inch partial instrument (i = b, c, d, e) 20.

That is, among the (p1 + p2 + p3 + p4 + p5) values obtained from the calculation results of the above equations 3a, 3b, 3c, and 3d, which assumes a failure of the measuring instrument i, the full-length instrument a (10) If there is a case with the current value of, since the instrument i is not used, it can be determined that the instrument is faulty.

Further, if (p1 + p2 + p3 + p4 + p5) values obtained from the calculation results of the equations (3a), (3b), (3c) and (3d) are not equal to the current value of the electric field measuring instrument a (10), Since one or more instruments are faulty, the entire instrument assembly can be determined as faulty.

In other words, Equations 3a, 3b, and 3d are not the same as the full-length instrument a (10) except for Equation 3c where the instrument d is faulty, and it is determined that the instrument is faulty. It is meant to be the same as the electric field measuring instrument a (10).

This means that if the instrument d is not used, the instrument d is a fault.

Therefore, while the present invention has a length different from the electric field measuring instrument 10 in the nuclear reactor, while implementing the partial length measuring instruments 20 and 30 installed in different positions to be constantly overlap, the position and length can be relatively derived It can be configured to generate the output distribution of the area where the faulty instrument is located by using the overlapped instrument signal of the same channel in case of a single instrument failure, thereby increasing the signal-to-noise ratio of the output signal of the fixed instrument of the reactor, and self-diagnosing the fault of the instrument. It is a new reactor stationary instrument that can improve the reliability and accuracy of the core protection / monitoring system.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation in the scope of the appended claims. It will be understood by those skilled in the art that various modifications may be made and equivalents may be resorted to without departing from the scope of the appended claims.

1 is a block diagram showing a stationary measuring instrument of the reactor according to the present invention,

2 is a configuration diagram showing a fixed measurement system of a conventional nuclear reactor;

3 shows a radial position of a stationary instrument of a conventional reactor,

4 is a view showing a longitudinal position of a conventional stationary instrument,

5 is a view showing a conventional PARSSEL measuring instrument,

6 is a view showing a conventional OPARSSEL measuring instrument.

* Description of the symbols for the main parts of the drawings *

10: full length measuring instrument (150 inches) 20: partial length measuring instrument (60 inches)

30: partial instrument (90 inches) 40: output

Claims (4)

In the stationary instrument of the reactor, A single full length instrument 10 having a length of 150 inches, four partial length meters 20 having a length of 60 inches, and a partial length meter 30 having a length of one 90 inch, The 60-inch partial instrument 20 is installed downwards so as to overlap by 30 inches on the upper side, and the 90-inch partial instrument 30 is installed at a position spaced 30 inches apart from the upper side. The length measuring instrument 10 is installed at a position corresponding to the 90-inch partial instrument 30 and at the same time, one full-length instrument 10 is installed on the side of the 60-inch partial instrument 20 to form an overlapping structure. Stationary instrumentation. The method of claim 1, The measuring instruments 10, 20, and 30 are installed at regular intervals in the longitudinal direction according to the installation position and length so as to satisfy the following equation, and the measured current values measured from the measuring instruments 10, 20, and 30 (a). , b, c, d, e) and the five longitudinal outputs (p1, p2, p3, p4, p5) is determined by the following equation (2). Equation 2 p1 = a-c-e p2 = f-d p3 = a-b-e p4 = f-c p5 = a-b-d Where a, b, c, d, e, f are current value measurements of the meter element, and p1, p2, p3, p4, p5 are outputs derived from the current value measurements The method according to claim 1 or 2, The meter (10, 20, 30) is a stationary meter of the reactor, characterized in that the emitter is made of any one material selected from rhodium, vanadium, platinum. The method according to claim 1 or 2, Current value measurement (a, b, c, d, e) and the output (p1, p2, p3, p4, p5) of the elements of the instruments (10, 20, 30) is determined by the following equation Fixed instrument of nuclear reactor. Equation 1 a = p1 + p2 + p3 + p4 + p5 b = p1 + p2 c = p2 + p3 d = p3 + p4 e = p4 + p5 f = p2 + p3 + p4 Where a, b, c, d, e, f are current value measurements of the meter element, and p1, p2, p3, p4, p5 are outputs derived from the current value measurements

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