KR20180079644A - method of Failed Feul Location Monitoring - Google Patents

Abstract

The present invention relates to a method for detecting the position of a defective fuel in a heavy-water reactor (CANDU-600), which is performed by 12 BF3 meters and more accurately detects a defective fuel by determining a fuel as a detective fuel when HR is 1.05 or greater by using a formula, HR(i, j, k) = DR(i, j, k) / {HR(i, j, k) + 2*σ(i, j, k)}. Accordingly, the reliability is improved.

Description

Method of Failed Feel Location Monitoring [

HR (i, j, k) = DR (i, j, k) / {HR (i, j, k)) is a method for detecting the position of a CAUGU- j, k) + 2 * σ (i, j, k)}, HR is determined to be a defective fuel when the HR is equal to or higher than the set value 1.05.

The CANDU-600 Defective Fuel Location Detection System performs defect identification by measuring the number of neutrons in the isotope indicating the occurrence of defective fuel by 12 instruments at a time.

Usually, once or twice a month, it operates the defective fuel position detection system. If it is confirmed that the defects have occurred, it is necessary to identify the location and to release the defective fuel early to keep the coolant system clean. do.

If a fault occurs, uranium must be suspended from the reactor (Tramp Uranium) and the I-131 will be released into the defective fuel.

The instrument is BF3 and 12 units are installed in two rooms (R-303, R-304). Three are placed on the top and three are placed on the bottom of the sample line to measure the neutron response for 100 seconds. 12 channels in two rooms [Figures 1 and 2] Measurement of 16 samples in the order # 1, # 3, and # 5 of Loop # 1 and Loop # do.

In the design guide, it is determined that the defect fuel discrimination is 1.3 or more by the following equation [1].

Discrimination ratio: individual detector counting rate ÷ 12 counting average counting rate ------- [Equation 1]

The outputs of the twelve channels for simultaneous measurement of FIG. 2 are not similar to each other as in FIG. 3, and thus there is a problem in defect discrimination. That is, there is a problem that the coefficient is large and the discrimination ratio is always high in a channel where a large output is output by using [Equation 1] simply.

Korean Patent Laid-Open Publication No. 10-2011-0008662 discloses a defective fuel position detection system having a self-diagnosis function, a method for testing the same, and a computer-readable recording medium storing a program for executing the method, Patent Publication No. 4063895 discloses a system for detecting defective fuel rods of a fuel assembly by detecting the release of a trace amount of Kr-85 in the fuel assembly generated by the gentle leakage fuel in the nuclear reactor core environment, The present invention contemplates an elevated effect of improving the reliability of faulty fuel detection in a technical configuration that is performed with 12 BF3 meters and uses a sigma formula to determine defective fuels when the HR is 1.05 or higher and more accurately detect defective fuels have.

The problem to be solved by the present invention is to evaluate the characteristics of the measuring instrument based on the measurement values of the 16 channels of the corresponding loops of this measurement and to evaluate the reliability by using past data instead of only using the measured values .

Another problem to be solved by the present invention is to consider the uncertainty (σ) such as the increase of the number of neutrons measured by the bad uranium (Tramp Uranium) due to the deposition of new fuel, the precipitation in the fuel channel, And the reliability of the defect fuel discrimination is improved.

The method of the present invention is a CANDU-600 deficient fuel position detection method, wherein defective fuel position detection is performed with twelve BF3 meters,

(I, j, k) = HR (i, j, k) = DR

Wherein the HR is set to 1.05 by using the equation and the fuel is determined to be defective fuel when the HR is equal to or greater than the set value.

{In the above formula

ego,

(A value obtained by calculating the measured value of the corresponding channel based on the measurement value average of the corresponding 16 loops)

I: Detector number (i = 1 to 12)

j: Position number (j = 1 to 16)

k: Loop number (k = 1, 2)

jj: Position number of channel not excluded

n: Number of channels that are not excluded (up to 16)

h: history number (serial number for DN scan)

Number of hits used for calculation N: (n2 - n1 + 1, usually 20 times)

σ: uncertainty}

Since the present invention evaluates the measured values of the sixteen channels of the corresponding loop, it takes into account the characteristics of the corresponding measuring instrument. It is effective.

Further, since the present invention is evaluated in consideration of uncertainty (?) Such as reduction of neutron number due to increase of neutron count due to new fuel loading, precipitation of neutrons due to bad uranium (Tramp Uranium) due to sedimentation in a fuel channel or fuel combustion, There is an increased effect of improving the reliability of the discrimination.

FIG. 1 shows the result of a single measurement 12-channel measurement of the defective fuel position detection system.
Figure 2 shows the fault fuel position detection system measurement sequence and channel location.

Hereinafter, the present invention will be described in detail.

As shown in FIG. 3, in the method of applying Equation 1 of 12 measurement channels, reliability is deteriorated because defect determination is performed using only 12 channel results at present.

Discrimination ratio = individual detector counting rate ÷ 12 counting average counting rate ------- (Equation 1)

It is necessary to utilize past measurement values of the corresponding channels according to the passage of time. Based on the past data (Formula 2), HR (Historical Ratio) is judged as defective fuel when the set value is 1.05 or more.

Thus, it was found that the reliability is improved when the fuel defect is judged by using (Equation 2).

HR (i, j, k) = DR (i, j, k) 2)

here,

to be.

(A value obtained by calculating the measured value of the corresponding channel based on the measurement value average of the corresponding 16 loops)

I: Detector number (i = 1 to 12)

j: Position number (j = 1 to 16)

k: Loop number (k = 1, 2)

jj: Position number of channel not excluded

n: Number of channels that are not excluded (up to 16)

h: history number (serial number for DN scan)

Number of hits used for calculation N: (n2 - n1 + 1, usually 20 times)

σ: uncertainty

(I, j, k) = HR (i, j, k) = HR (i, j, k) ) + 2 * σ (i, j, k)}, HR is determined to be a defective fuel when the HR is equal to or higher than the set value 1.05, so that the reliability can be improved by detecting the defective fuel more accurately.

Claims (2)

In the CANDU-600 deficient fuel location detection method,
Performed with 12 BF3 instruments,
HR (i, j, k) = DR (i, j, k)
A method for detecting a heavy fuel deficient fuel position using the equation (2), wherein HR is determined to be defective fuel when the HR is equal to or greater than a predetermined value.
(In the formula

ego,
(A value obtained by calculating the measurement value of the corresponding channel based on the measurement value average of the 16 channels of the corresponding loop)
I: Detector number (i = 1 to 12)
j: Position number (j = 1 to 16)
k: Loop number (k = 1, 2)
jj: Position number of channel not excluded
n: Number of channels that are not excluded (up to 16)
h: history number (serial number for DN scan)
Number of hits used for calculation N: (n2 - n1 + 1, usually 20 times)
σ: uncertainty} The method according to claim 1,
Wherein the set value of HR is 1.05.

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