JPH0381695A - Method and device for nuclear fuel breakage detection - Google Patents

Abstract

PURPOSE:To shorten a measurement time and to securely nuclear fuel breakage in a short time by separating and measuring four kinds of nuclear species by using one or two precipitators. CONSTITUTION:The scintillation detector 4e of a 1st precipitator 4 measures rare gas FP flowing in from primary cooling system piping 1 through a sampling pipe 2, its detection signal is discriminated by crest discriminators 6a and 6b into a low-energy and a high-energy part, and respective output signals are counted by counters 8a and 8b, whose outputs are sent to a computer 10. Similar processing is performed by a precipitator 5. A delay time is set and the discrimination levels of the low-energy part and high-energy part of the crest distribution of beta rays are set to separate and measure four counted values.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Industrial Application Field The present invention relates to a nuclear fuel damage detection method and apparatus for a gas-cooled nuclear reactor using a wire-driven precipitator (hereinafter abbreviated as precipitator).

(2) Conventional technology precipitators are rare gas fission products (hereinafter abbreviated as noble gas FP) and their daughter nuclides ( It is known as a device that measures nuclides that undergo beta ray decay in a short period of time (less than half-life addition).

FIG. 5 shows a method of measuring rare gas FP using the precipitator. According to the figure, the sampling gas 52 containing the rare gas FP flowing through the sampling pipe 51 enters the gas reservoir 53 of the precipitator force.

When the rare gas FP undergoes beta ray decay in this gas reservoir 53, the newly generated daughter nuclide becomes positively charged. Therefore, if a negative voltage is applied to the metal wire 54, which is placed through the center of the gas reservoir 53, using a high-voltage power source (not shown), the daughter nuclides are attracted to the metal wire 54 and become attached to the wire. adhere to. The wire 54 runs for a certain period of time (T) to collect the daughter nuclides.
s) After being placed in the gas reservoir 53, the wire drive device 5
5 to the scintillation detector 57 of the scintillator 56, where the scintillation detector 57 detects the beta rays emitted when the daughter nuclide attached to the wire decays according to its half-life. The detection signal of the scintillation detector 57 is discriminated into a noise component and a beta ray signal component by a pulse height discriminator 58, and the beta ray signal component is input to a counting circuit 59 and counted.

(3) Problems to be Solved by the Invention In the case of a light water reactor, when there is no nuclear fuel damage, the sampling gas contains rare gas FP. Nuclear fuel damage can be detected if all detectable nuclides are counted by distinguishing them from the components, and if nuclear fuel damage occurs when this counted value exceeds a preset value.

On the other hand, in gas-cooled nuclear reactors, coated particle fuel is used, so even if the fuel is undamaged, a small amount of rare gas F'P is constantly released into the cooling gas. The rare gas F'P circulates through the primary gas cooling system,
It saturates according to its half-life and becomes pack ground during measurement (counting).

For this reason, it is necessary to predict the pack ground in advance based on the reactor operating conditions, and if it exceeds this predicted value, it is assumed that nuclear fuel damage has occurred. However, if some of the coated particulate fuel is damaged, it would be difficult to count all the nuclides that are released that can be detected by the precipitator, as in light water reactors, because the half-life of each noble gas FP is different. It becomes very difficult to predict the value of packground in the system.

For this reason, it is conceivable to detect fuel damage by paying attention to appropriate nuclides, for example. In addition, in the event of nuclear fuel damage, the release ratio of long-half-life nuclides and short-half-life nuclides may differ from the release ratio in the case of no damage, so it is a good idea to take measures such as measuring both separately and comparing them. It will be done. In this way, it becomes easy to correct the half-life, etc., and it becomes possible to detect fuel damage in a nuclear reactor using coated particle fuel with high sensitivity.

As mentioned above, in order to improve the detection sensitivity of fuel damage in a gas-cooled nuclear reactor, a precipitator that can separate and detect each rare gas FP nuclide is required.

As a method for separating and measuring rare gas FP nuclides using a precipitator, for example, as shown in Figure 6, there is a method that uses four types of delay piping and separates only by the difference in attenuation due to the half-life of the rare gas FP. Are known.

However, in order to separate and determine the four nuclides, the above method requires the power of four precipitators, and in order to improve accuracy, a delay time is required to increase the difference in the number of decays due to half-life. Since it is necessary to take a long time and the same time as the delay time is required until a response is received, there is a drawback that the detection time is long.

The present invention was made in order to solve the problems of the prior art described above, and its purpose is to improve detection sensitivity without using four precipitators, and without requiring detection time. An object of the present invention is to provide a method and device for detecting nuclear fuel damage that is capable of detecting nuclear fuel damage.

(4) Means for Solving the Problems The means of the present invention to achieve the above object is to detect damage to nuclear fuel by measuring noble gas fission products released from nuclear fuel during reactor operation using a wire-driven precipitator. In doing so, two wire-driven precipitators are used to measure rare gas fission products at different times, and the count values of the wire-driven precipitators differ for each nuclide depending on the half-life, and the wire-driven precipitators The count values of the high-energy part and the low-energy part obtained by pulse height discrimination of the output signal of the scintillation detector that measures the beta rays emitted from the daughter nuclides of the rare gas fission products attached to the wire have different energy pulse height distributions. For this purpose, four detectable nuclides are separated and measured by calculating four-dimensional linear simultaneous equations using the fact that they differ for each nuclide, and solving the four-dimensional linear simultaneous equations. .

In addition, using one wire-driven precipitator, the daughter nuclides of the rare gas fission products attached to the wire of the wire-driven precipitator are measured twice at different times, and the counted value obtained is determined by the half-life period. This is because it differs for each nuclide, and because the count values of the low energy part and the high energy part obtained by discriminating the pulse height of the output signal of the scintillation detector that measures the beta rays emitted from the daughter nuclide have different energy pulse height distributions. The method is characterized in that four detectable nuclides are separated and measured by determining four-dimensional linear simultaneous equations using the fact that they are different for each nuclide, and solving the four-dimensional linear simultaneous equations.

(5) Operation Of the rare gas FP released from the nuclear reactor, there are the following 11 nuclides that can be detected by the precipitator.

Here, h is hour, m is minute, and S is second.

Among the nuclides, 91Kr, 92Kr, 93Kr,
140Xe, 141Xe.

The half-life of the 6 nuclides of 142Xe is very short, and they decay until they flow into the precipitator, making them practically impossible to measure.Also, the amount of 139Xe generated is thought to be small, and in reality, 88Kr ( Half-life: 2.
8 hours), 89Kr (half-life: 3.:l), 90Kr (
Half-life: 32.2 seconds), 138Xe (Half-life: 14
．． 1 minute) are the targets of measurement.

When the four nuclides are to be measured and, for example, two precipitators are used to detect nuclear fuel damage, the rare gas F'P containing the four nuclides is measured by a scintillation detector in the first precipitator. Then, the actual measured values of the low energy part and the high energy part S1. Find S2. Next, after a delay of Td seconds, the scintillation detector in the second precipitator measures the actual measured values S3. of the low energy portion and the high energy portion. Find S4.

As a result, the following four-dimensional linear simultaneous equations are obtained.

In other words, EL□, N1+ from the first precipitator
EL□-N2+EL3・N3+EL4・N4=S1Eh
0. N1+EL□・N2+Eh3. N3+Eh4. N4
-82 is derived, and from the second precipitator 6'-rl-ELI -N1 + e-" ・El2
・N2+e-r3-El3, N3+e-r4 ・El
4-N4 =83e-r1'Ehl'Nl+e
"-r2"Eh2°N2+e-r3" El3 ・N
3+6-r4'El4'N4''s4 is derived.

Here, r1+ r21 r31 r4 is 88Kr, 8
The decay constants of four nuclides, 9Kr, 90Kr, and 138Xe, are shown, and N1. N2゜N3 + N4 indicates the count value of each nuclide measured by the first precipitator, and E
LI・Ehl・El2・El2・El, 3・Eh3 +
EL4 + Eh4 indicates the detection ratio of sulbeta rays emitted when a daughter nuclide of a nuclide is detected into a low energy part and a high energy part by the scintillation detector in the precipitator.

Since each of the above equations is independent of each other, it can be solved mathematically strictly as a four-dimensional linear system of equations, and as a result, 88Kr
The count value N1 + N2 * N3 + N4 measured by the first precipitator corresponding to each of the four nuclides of , 89Kr, 90Kr, and 138Xe can be separated and determined, and the calculated count value NI I N21
Nuclear fuel damage can be detected based on N31 N4.

(6) Examples An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the nuclear fuel damage detection device of the present invention. In the figure, reference numeral 1 is a primary cooling system pipe, 2 is a sampling pipe, 3 is a delay pipe, and 4.5 is a precipitator.

The primary cooling gas containing the rare gas FP from the reactor flows from the primary cooling system piping 1 through the sampling pipe 2 to the first (first) precipitator 4, and also through the delay piping 3 branched from the sampling pipe 2. The signal then flows to the second precipitator 5 after a predetermined time delay (16 seconds).

The first precipitator 4 and the second precipitator 5 have the same structure, and have gas reservoirs 4a, 5a, metal wires 4b, 5b, and wire drive section 4c, respectively, like the conventional precipitator shown in FIG. , 5c, scintillation 4d, 5d and scintillation detectors 4e, 5e
Equipped with: The rare gas F'P that has flowed into the gas reservoirs 4a and 5a undergoes beta ray decay here, and the daughter nuclides produced during the decay are positively charged, so the gas reservoirs 4a and 5a
When a negative voltage is applied to the metal wires 4b, 5b passing through the center of the metal wires 4b, 5b using a high voltage power source (not shown), daughter nuclides are attracted and adhere to the metal wires 4b, 5b. After the metal wires 4b, 5b are placed in the gas reservoirs 4a, 5a for a certain period of time (Ts), they are moved to the positions of the scintillation detectors 4e, 5e by the wire drive units 4c, 5c, and the attached daughter nuclides have a half-life. The beta rays emitted during decay are detected. For this detection, the thickness of the scintillation detectors 4e and 5e was set to be 20wn or more in order to be able to measure the maximum energy beta ray (5MeV). It is set to be much thicker than a scintillation detector.

Here, the important point is that the scintillation detector 4e,
The wave height distribution measured by 5e is divided into a high energy portion and a low energy portion and counted.

That is, first pulse height discriminators 6a and 6b are connected to the output side of the scintillation detector 4e for discriminating the wave height distribution measured by the scintillation detector 4e into a low energy portion and a high energy portion, and Connected to the output side of the scintillation detector 5e are second pulse height discriminators 7a and 7b which discriminate the pulse heights of the pulse height distribution measured by the scintillation detector 5e into low energy portions and high energy portions. And the first
Counting circuits 8a and 8b are connected to the output sides of the second wave height discriminators 6a and 6b, respectively, for counting the output signals of the low energy portion and the high energy portion subjected to the wave height discrimination. Also connected to the output side are counting circuits 9a and 9b, respectively, which count the output signals of the low energy portion and the high energy portion, which are subjected to wave height discrimination.

Count values S1. of the counting circuits 8a, 8b, 9a, 9b.
S2゜S3. S4 is input to the computer 10 which is a calculation means, and the following calculation processing is performed here according to a preset program.

That is, the measurement results of the first precipitator 4 (S□
, S2), ELl°N1+EL2°N2+EL3°N3+E,°N
4-8IEhl 'Nl +Eh2' N2 +E
h3 ”N3 +Eh4°N4:S2 is derived, and the measurement result of the second precipitator 5 (83134
), e-rl・EL□・N1+e-r2・EL2・N2+e
-r3- EL3- N3. +er4 ・EL4-
N4 = 83e-rl"Ehl"Nl, e-r2
．． Eh2'N2+e-r3-Eh3'N3+e-"
-Eh4-N4=S4 is derived.

Then, by solving the four-dimensional linear simultaneous equations, 88Kr,
Count values Nl, N2. measured by the first precipitator 4 corresponding to each of the four nuclides of 89Kr, 90Kr, and 138Xe. N3. N4 is continuously measured.

Here, r1+r2. r3+r4 is 88Kr, 89K
r, 90Kr.

The decay constants of the four nuclides of 138Xe are shown, and the ELI I
EhllEL2・Eh2・EL3・”h3・EL4・
Eh4 is a scintillation detector 4e, 5 in the precipitator of beta rays emitted when daughter nuclides of each nuclide decay.
It shows the detection ratio of low energy parts and high energy parts by e.

The calculation result of the computer 10 is displayed on the display device 11, and the count value Nl exceeds a preset value.

N2. N3. When N4 is displayed, it is known that nuclear fuel damage has occurred.

Next, a first embodiment of the nuclear fuel damage detection method of the present invention will be described using the nuclear fuel damage device.

First, the scintillation detector 4e of the first precipitator 4 measures the rare gas FP flowing through the primary cooling system pipe 1 or the sampling pipe 2, and then the detection signal of the scintillation detector 4e is passed to the pulse height discriminators 6a, 6.
After the wave height is discriminated into a low energy portion and a high energy portion in step b, and each output signal is counted by counting circuits 8a and 8b, the counted value is sent to a computer 10 for arithmetic processing. Then, after a delay time Td seconds, the rare gas F' flows in.
P is measured by the scintillation detector 5e of the second precipitator 5, and the detection signal of the scintillation detector 5e is similarly differentiated into a low energy part and a high energy part by the pulse height discriminators 7a and 7b, and the respective outputs are After the signals are counted by the counting circuits 9a and 9b, the counted values are sent to the computer 10 for arithmetic processing.

Here, the important parameter to separate and measure the count value N1 + N2 + N3 * N4 is the delay time T
d and the discrimination level between the low energy part and the high energy part of the wave height distribution of beta rays, which will be explained below.

The setting standard is to make the four equations described above more independent and to select parameters that can be separated with high accuracy. Therefore, in this embodiment, the delay time Td was set to 200 seconds, which is close to the half-life of 89Kr. When the delay time Ta is set in this way, the counts of 88Kr and 138xe, which have long half-lives, are almost unchanged, whereas the counts of 89Kr and 90Kr, which have short half-lives, are clearly 1/2 and 1/10, respectively. Be able to distinguish. In addition, the discrimination level was set to 2.5 MeV and Tab
According to the data book of Radiative Engineering 5otopes, the proportion of high energy part is 88Kr and 35.8% as shown in Table 1 below.

While it is 13.9% at 90Kr, it is 7.9% at 89Kr.
7%, 138xe with 3.4 more, 88Kr,
The contribution of 90Kr (former), 89Kr, and 138xe (latter) can be clearly distinguished.

Table 1 Ratio of high energy part and low energy part of beta rays (
Table of Radioactive l
5otopes) That is, if the parameters (delay time Td, discrimination level) are set as described above, ■ 88Kr and 13Kr have almost no difference in attenuation difference due to half-life.
8xe can be clearly distinguished by wave height discrimination, ■ 89Kr and 138Xe, which are difficult to differentiate by wave height discrimination, can be clearly distinguished by attenuation due to half-life, ■ 90Kr and other nuclides can be clearly distinguished by the difference in attenuation. become able to do.

The four-dimensional linear simultaneous equations obtained by inputting the above parameters are shown below.

0.642xN1+0.923xN2+0.966xN
3+0.966xN4=S10.358XN,, +○,077XN2+0.034XN3+0.139XN4
=S20.633XN1+0.445XN2+0.81
9XN3+0.011XN4=S30.353XN1+
0.037XN2+0.029XN3+0.002XN
4=S4 By solving this four-dimensional linear system of equations with the computer 10, the four rare gas F'P nuclides 88Kr and 89K
r, 90Kr.

The count values N11, N21, N31, and N4 of 138Xe can be measured separately.

This eliminates the need to use four precipitators and four types of delay pipes as in the prior art, making it possible to significantly shorten the measurement time (detection time).

FIG. 2 shows a second embodiment of the nuclear fuel damage detection device of the present invention. In FIG. 5, the same parts as those shown in FIG. 1 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In the first embodiment, two precipitators are used to collect four rare gas FP nuclides: 88Kr, 89Kr, 90Kr, 1
38×8 count value Nl, N2. N3. While N4 is separated using the attenuation difference in half-life of the rare gas F'P nuclide, in the second embodiment, one precipitator is used to separate the rare gas FP nuclides 88Kr, 89Kr, and 90. Ding,
Daughter nuclide 88 that 138Xe decays and adheres to wire 4b
The attenuation difference due to half-life of Rb (half-life: 17.8 minutes), 89Rb (half-life: 15.2 minutes), 90Rb (half-life: 2.55 minutes), and 138C8 (half-life: 32.2 minutes) Usage: 88Rb, 89Rb, 90Rb, 1
38C8 count value Nl, N2°N3. I am trying to separate N4.

That is, the beta rays emitted when the daughter nuclide attached to the wire 4b of the precipitator 4 decays are
It is configured to measure times.

When the daughter nuclide emits beta rays, the pulse height distribution measured by the scintillation detector 4e is discriminated into a low energy portion and a high energy portion by the pulse height discriminators 6a and 6b, as in the first embodiment.

Here, the scintillator 4d has a thickness of 20 mm or more in order to be able to measure the maximum energy beta ray (5 MeV), as in the first embodiment, and a thickness of 1 m to lower the back ground. The scintillator is much thicker than conventional scintillators.

The output signals from the wave height discriminators 6a and 6b are outputted to a counting circuit 8a,
After Tc seconds are counted at step 8b, it is input to the computer 10.

Then, after Tb seconds have passed, the beta rays emitted from the daughter nuclide attached to the same wire 4b are measured again by the scintillation detector 4e, and the counted value is similarly calculated by the computer 1.
0 is input. The computer 10 is designed to perform the following arithmetic processing according to a preset program.

That is, from the first measurement results (Sl, S2), E
L□・N engineering+EL2・N1+EN3・N3+EL,・N
4=S1”hl・N1+Eh3・N2+Eh3・N3・
Eh4・N4=S2 is derived, and from the second measurement result after 14 seconds (S3.S4), e′−rl・EL□・N1+e−r2・EL2. N2
+e-r3・EL3-N3+e-r4-EL4-N4
=S3e ” -EhI-N1+6-r2.Eh2-N
2+e-r3-Eh3 ・N3+e-r4-Eh4-N
4 = S4 is derived.

Then, by solving the four-dimensional linear simultaneous equations, 88Rb,
First counted value N□+ N2+ corresponding to each nuclide of 89 Rb, 90 Rb, and 138 C8
N3 t N4 are separated and measured.

Here, rl, r2+ r3. r4 is 88Rb,
The decay constants of the four nuclides 89Rb, 90Rb, and 138Cs are shown, and EL□, Eh□+ ”L2 +
Eh2 + EL3 + ”N3 * EL4 + Eh
4 shows the detection ratio of beta rays emitted when the daughter nuclides of each nuclide decay into low energy parts and high energy parts by the scintillator 4d in the precipitator.

The calculation results of the calculator 10 are displayed on the display device 11, and the calculated values N1°N2.
N3. When N4 is displayed, it is known that nuclear fuel damage has occurred.

Next, a second embodiment of the nuclear fuel failure detection method of the present invention will be described using the nuclear fuel failure device.

- When the rare gas FP flowing from the secondary cooling system piping 1 through the sampling tube 2 undergoes beta decay, the daughter nuclides are positively charged and adhere to the wire 4b, which has a negative voltage. Then, beta rays emitted when the daughter nuclide attached to the wire 4b decays are measured by the scintillation detector 4e. Next, the detection signal of the scintillation detector 4e is subjected to pulse height discrimination into a low energy part and a high energy part by pulse height discriminators 6a and 6b, and the respective output signals are counted by counting circuits 8a and 8b.
Send to 0. After this, after a delay of Td seconds, the same wire 4
The beta rays emitted when the daughter nuclide attached to b decays are measured by the scintillation detector 4e, counted in the same manner, and then the counted value is sent to the computer 10.

Here, the count values N, , N2. N3. Important parameters for separately measuring N4 are the setting of the delay time Td and the setting of the discrimination level between the low energy part and the high energy part of the pulse height distribution of beta rays, which will be explained below.

The standard for setting is to make the four equations described above very independent and to select parameters that can be separated with high accuracy. Therefore, in this example, the delay time Td was set to 400 seconds, which is nearly twice the half-life of 90 Rb.

If the delay time Td is set in this way, 9
0 Rb is 1/6 and can be clearly distinguished from other nuclides. In addition, for Rb and Cs, which have relatively long half-lives, the difference is 0.74 times and 0.87 times, which is a discernible difference.On the other hand, as for the discrimination level, 2
．． When set to 5 MeV, the proportion of high-energy parts is 35.8% for 88Rb and 13.9% for 90Rb, while it is 7.7% for 89Rb and 3.4% for 138C8.
%, 88Rb, ``Rb (former) and 89
The contribution from Rb and 138C8 (the latter) can be clearly distinguished.

That is, if the parameters (delay time Ta, discrimination level) are set as described above, 88Rb and 89Rb, which have almost no difference in attenuation due to half-life, can be clearly distinguished by wave height discrimination; 8 that is too old to give out
9Rb and 138O8 can be clearly distinguished by their attenuation due to half-life, and 90Rb and other nuclides can be clearly distinguished by the difference in their attenuation. In this example, the nuclides that show little difference in half-life are 89Rb, which has a half-life of 15.2, and 89Rb, which has a half-life of 32.2.
Cs, but if the delay time Ta is set longer,
It is possible to clarify the difference between the two.

The four-dimensional linear simultaneous equations obtained by inputting the above parameters are shown below.

0.642XN□+0.923xN2+0.966xN
3+0.861 xN4= S10.358XN1+0
．． 077XN2+0.034XN3+0.139XN4
==320.459XN1+0.681xN2+0.8
36XN3+0.140XN4 =:S30.276x
N1+0.057xN2+0.029xN3+0.02
2xN4 ==S4 This four-dimensional linear simultaneous equation is calculated by computer 1.
By solving for 0, the four noble gas F'P nuclides 88R
b, 89Rb, 90Rb.

138C8 count value Nl + N2 t N3 r N
4 can be separated and measured.

This eliminates the need to use four precipitators and four types of delay pipes as in the prior art, making it possible to significantly shorten the measurement time (detection time).

FIG. 3 shows a third embodiment of the nuclear fuel damage detection device of the present invention. In the figure, the same parts as those shown in FIGS. 1 and 2 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In the third embodiment, the beta rays from the daughter nuclide attached to the same wire 4b that was once measured in the second embodiment are measured again by the same scintillation detector 4e after a delay time, and the count value attenuated by the half-life is calculated. Instead of getting 2
2 scintillation detectors with the same structure 4e1*4ez
using the scintillation detector 4el I 4a
By making the interval between the gas reservoir 4a and the first scintillation detector 4el an integral multiple (nl) of the interval (IPs), and making the precipitator 40 soak time and counting time (Ts) the same, the half-life Obtain the attenuated count value and calculate L.

That is, the wire 4b measured by the first scintillation detector 4el is measured by the second scintillation detector 4e2 after an integer multiple of the soak time (Ts×n seconds), so that the wire 4b is measured by the second scintillation detector 4e2 after a delay time (TsXn seconds=Ta). We have obtained a count value of .

This makes it possible to drive the wire 4b one after another for measurement, and to provide a sufficient delay time, making it possible to carry out the method of the second embodiment continuously with even higher precision. Become.

Regarding coated particle fuel used in gas-cooled nuclear reactors,
As a result of measuring changes in the concentration of rare gas FP nuclides released upon failure, it was found that long half-life nuclides increased rapidly, although it was on the order of several hours compared to intermediate and short half-life nuclides. has been confirmed. FIG. 4 shows an example of measurement of a rare gas FP using a GeStrometer. As is clear from the figure, 135xe (half-life: 9.
1 hour), 88Kr (half-life: 2.8 hours) is a medium-short half-life nuclide, 138Xe (14,1 minutes) and 89Kr.
(3, 2 minutes), a result with a large increase rate was obtained.

Therefore, by the apparatuses of the first, second and third embodiments, 8
By selecting and measuring 8Kr, it is possible to increase the sensitivity several times compared to measuring the entire count value, and by comparing the increase rate of long half-life nuclides and medium-short half-life nuclides, it is possible to Damage can be detected reliably.

(9) Detailed Description of the Invention According to the present invention, four types of nuclides can be separated and measured using one or two precipitators. The measurement time (detection time) can be significantly shortened compared to conventional examples using different types of delay piping, and nuclear fuel damage can be detected reliably in a short period of time.

[Brief explanation of drawings]

Fig. 1 is a schematic explanatory diagram of a nuclear fuel damage detection device showing a first embodiment of the present invention, Fig. 2 is a schematic explanatory diagram of a nuclear fuel damage detection device showing a second embodiment, and Fig. 3 &-1 Third implementation FIG. 4 is a graph showing changes in concentration of rare gas FP at the time of clad fuel failure, and FIGS. 5 and 6 are schematic illustrations showing conventional techniques. In the figure, code 1 is the primary cooling system piping, 2 is the sump 1 non-long pipe,
3 is delay piping, 4.5 is precipitator. 4a and 5a are gas reservoirs, 4b and 5b are wires, 4C15
C is a wire drive unit, 4d and 5d are scintillators, 4e,
5e is a scintillation detector, 6a, 6b, 7a, 7
b is a pulse height discriminator; 8a, 8b, 9a, and 9b are counting circuits; 10 is a counter; and 11 is a display device.

Claims (5)

[Claims] (1) In a nuclear fuel failure detection method that detects nuclear fuel failure by measuring noble gas fission products released from nuclear fuel during reactor operation using a wire-driven precipitator, rare gas fission products are measured at different times. The count value of the wire-driven precipitator differs for each nuclide depending on the half-life, and the daughter nuclide of the rare gas fission product attached to the wire of the wire-driven precipitator is used. The output signal of a scintillation detector that measures emitted beta rays is divided into pulse heights, and the count values of high-energy and low-energy parts are calculated using the fact that the energy pulse height distribution differs for each nuclide. Find the simultaneous equations,
A method for detecting nuclear fuel damage, characterized in that four detectable nuclides are separated and measured by solving the four-dimensional linear simultaneous equations. (2) In a nuclear fuel failure detection device that detects nuclear fuel failure by measuring rare gas fission products released from nuclear fuel during reactor operation using a wire-driven precipitator, daughter of rare gas fission products attached to the wire is used. A first wire-driven precipitator having a scintillation detector that measures beta rays emitted from the nuclide; and a scintillation detector that measures the beta rays emitted from the daughter nuclide of a rare gas fission product attached to the wire. and a second wire-driven precipitator that performs measurement after the first wire-driven precipitator, and a low-energy portion of the output signals of the scintillation detectors of the first and second wire-driven precipitators. first and second wave height discriminators having two wave height discriminators for discriminating wave heights in the high energy portion and the first and second wire-driven precipitators, and the count values of the first and second wire-driven precipitators differ for each nuclide depending on the half-life. and a four-dimensional linear combination obtained by taking advantage of the fact that the count values of the low energy part and the high energy part whose wave heights are discriminated by the first and second wave height discrimination means are different for each nuclide due to the difference in the energy wave height distribution. 4 by solving the equation
1. A nuclear fuel damage detection device comprising: calculation means for separating and measuring two detectable nuclides. (3) In a nuclear fuel damage detection method that detects nuclear fuel damage by measuring noble gas fission products released from nuclear fuel during nuclear reactor operation using a wire-driven precipitator, using one wire-driven precipitator, The count value obtained by measuring the daughter nuclides of the rare gas fission products attached to the wire of the wire-driven precipitator twice at different times differs for each nuclide depending on the half-life, and that the daughter nuclides are released from the daughter nuclides. A four-dimensional linear simultaneous equation is created by utilizing the fact that the count values of the low-energy part and the high-energy part obtained by discriminating the pulse height of the output signal of the scintillation detector that measures beta rays differ for each nuclide due to the difference in the energy pulse height distribution. A method for detecting nuclear fuel damage, characterized in that four detectable nuclides are separated and measured by solving the four-dimensional linear simultaneous equations. (4) In a nuclear fuel failure detection device that detects nuclear fuel failure by measuring rare gas fission products released from nuclear fuel during reactor operation using a wire-driven precipitator, daughter of rare gas fission products attached to the wire is used. A wire-driven precipitator that has a scintillation detector that measures beta rays emitted from nuclides; and pulse height discrimination of the output signal of the scintillation detector of the wire-driven precipitator into a low energy portion, a high energy portion, and a high energy portion. a wave height discrimination means having two wave height discriminators, and a count value obtained by measuring the daughter nuclide twice at different times, which differs for each nuclide depending on the half-life, and obtained from the wave height discrimination means. The four detectable nuclides are separated and counted by solving a four-dimensional linear simultaneous equation, which takes advantage of the fact that the count values of the low-energy part and the high-energy part are different for each nuclide due to the difference in energy wave height distribution. What is claimed is: 1. A nuclear fuel damage detection device comprising: calculation means. (5) In a nuclear fuel failure detection device that detects nuclear fuel failure by measuring rare gas fission products released from nuclear fuel during reactor operation using a wire-driven precipitator, daughters of rare gas fission products attached to the wire are used. A wire-driven precipitator has two scintillation detectors that measure beta rays emitted from nuclides at different times, and the output signal of the scintillation detector of the wire-driven precipitator is divided into a low energy part and a high energy part. first and second wave height discriminators each having two wave height discriminators for discriminating wave heights, and a count value obtained by measuring the daughter nuclide twice at different times, which differs for each nuclide due to its half-life; Four detections are possible by solving four-dimensional linear simultaneous equations obtained by taking advantage of the fact that the count values of the low-energy portion and the high-energy portion obtained from the wave height discrimination means differ for each nuclide due to the difference in energy wave height distribution. What is claimed is: 1. A nuclear fuel damage detection device comprising: calculation means for separating and counting nuclides.