JP2011002301A - Neutron instrumentation system and neutron instrumentation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To integrate and simplify an instrumentation system for measuring a neutron flux outside a reactor.SOLUTION: This system includes a pulse counting circuit 5 for measuring a startup range, a fine current measuring circuit 7 for measuring a power range, and a fluctuating component measuring circuit 6 for measuring a range between the pulse counting circuit 5 and the fine current measuring circuit 7, which are arranged outside the reactor. The system further includes: aB detector 1 arranged outside the reactor, and connected so as to issue an output to the pulse counting circuit 5, the fine current measuring circuit 7 and the fluctuating component measuring circuit 6, for equalizingB coating thickness of the detector inner surface by plasma sputtering; and a measured signal selection means 8 arranged outside the reactor, for selecting some of each output from the pulse counting circuit 5, the fine current measuring circuit 7 and the fluctuating component measuring circuit 6, based on each output from the pulse counting circuit 5, the fine current measuring circuit 7 and the fluctuating component measuring circuit 6 on the basis of the output from theB detector 1.

Description

  The present invention relates to a neutron instrumentation system for measuring a neutron flux outside a nuclear reactor and a neutron instrumentation method using the neutron instrumentation system.

When measuring a neutron flux outside a conventional nuclear reactor, the neutron flux range fluctuates in a large range, and therefore it is common to use a plurality of types of measurement systems depending on the neutron flux range (see Patent Document 1). . For example, in a typical pressurized water reactor (PWR), three types of measurement systems are used depending on the neutron flux range. That is, a pulse counting system using a BF ₃ detector is used for neutron flux measurement in the start-up range (10 ⁻¹ to 10 ⁶ n / cm ² / sec), and a wide range (1 to 10 ¹⁰ n / cm ² / sec) is used. The fluctuation component measurement system using a fission ionization chamber is used for neutron flux measurement in sec), and ¹⁰ B detection is used for neutron flux measurement in the power range (5 × 10 ^{2 to} 5 × 10 ¹⁰ n / cm ² / sec). A minute current measurement system using a measuring instrument is used. Of these, subcritical monitoring of fuel is performed in a wide range, stop monitoring is performed in a startup range, and operation monitoring is performed in a power range.

JP-A-9-243784

  In the above-described PWR out-of-core neutron instrumentation system, a plurality of measurement systems are provided independently in accordance with the measurement range, resulting in a complicated system configuration.

  An object of the present invention is to realize a simplified reactor neutron instrumentation by integrating these measurement systems.

In order to achieve the above object, a neutron instrumentation system according to the present invention is a neutron instrumentation system that measures a neutron flux outside a nuclear reactor, a pulse counting circuit that is arranged outside the reactor and measures a startup range; A minute current measuring circuit arranged outside the nuclear reactor for measuring the power range, a fluctuation component measuring circuit arranged outside the nuclear reactor for measuring the range between the pulse counting circuit and the minute current measuring circuit, and the pulse counting circuit, wherein the low current measurement circuit and connected to produce an output to the fluctuation component measurement circuit, the ^{10 B} coating thickness detector the inner surface, the thickness of the range detection sensitivity for increase in the thickness is stable at substantially constant and homogenized with a micrometer order, and ^{10 B} detector disposed outside the reactor, the pulse count based on the output of the ^{10 B} detector of Selected from the output of the pulse counting circuit, the minute current measuring circuit and the fluctuation component measuring circuit based on the output of the path, the minute current measuring circuit and the fluctuation component measuring circuit Measurement signal selection means.

Further, the neutron instrumentation method according to the present invention, the neutron instrumentation methods for measuring the neutron flux in a nuclear reactor outside the ^{10 B} coating thickness detector the inner surface, the detection sensitivity for an increase in thickness is stabilized at a substantially constant A ¹⁰ B detector with a thickness within a certain range and uniform in the micrometer order is placed outside the reactor, a pulse counting circuit that measures the startup range is placed outside the reactor, and a minute current that measures the power range A measurement circuit is arranged outside the reactor, a fluctuation component measurement circuit for measuring the range between the pulse counting circuit and the minute current measuring circuit is arranged outside the reactor, and the output of the ¹⁰ B detector is used as the pulse counting circuit. The pulse counting circuit based on the output of the ¹⁰ B detector, the minute current measuring circuit, and the minute current measuring circuit. And selecting one of the output of the pulse counting circuit, the minute current measuring circuit and the minute current measuring circuit based on the output of the minute current measuring circuit.

  According to the present invention, a wide range of in-core neutron measurement ranges can be covered with a simple system.

The block diagram which shows the structure of one Embodiment of the reactor neutron instrumentation system which concerns on this invention. ^The figure which shows the detection sensitivity with respect to the increase in thickness in 10B coating thickness. FIG. 2 is a schematic sectional elevation view showing an example of a method for equalizing the coating thickness on the inner surface of the ¹⁰ B detector by plasma sputtering in the manufacturing process of the ¹⁰ B detector of the out-of-core neutron instrumentation system of FIG. 1.

  Hereinafter, an embodiment of an output distribution monitoring apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of an embodiment of an in-core neutron instrumentation system according to the present invention.

In FIG. 1, the ¹⁰ B detector 1 and the monitoring unit 4 are installed outside a reactor (for example, PWR) 2. ^{The 10} B detector 1 is manufactured by plasma sputtering so that the ¹⁰ B coating thickness is uniform in the order of micrometers and in a thickness range in which the detection sensitivity with respect to the increase in thickness is substantially constant and stable. A method for manufacturing the ¹⁰ B detector 1 by plasma sputtering will be described later with reference to FIG. In addition, it is preferable to use Ar gas as the sealed gas of the ¹⁰ B detector 1.

The output signal of the ¹⁰ B detector 1 is connected to the pulse counting circuit 5, the fluctuation component measuring circuit 6, and the minute current measuring circuit 7 incorporated in the monitoring unit 4 through the signal line 3. Measurement signals obtained from the pulse counting circuit 5, the fluctuation component measurement circuit 6, and the minute current measurement circuit 7 are input to the measurement signal selection means 8.

^The signal obtained from the ¹⁰ B detector 1 is measured by the pulse counting circuit 5, the fluctuation component measuring circuit 6, and the minute current measuring circuit 7, respectively. The fluctuation component measurement is generally called Campbell measurement or MSV (root mean square voltage) measurement.

In conventional ^{10 B} detector it is difficult to equalize the thickness ^{10 B} coated with micrometer order, to a constant amount of α-rays generated by the neutron irradiation of the ^{10 B} is absorbed to ^{10 B} itself because could not, although the ratio of the pulse count and the fluctuation component measurements it is difficult to be constant, by plasma sputtering, ^{10 10 B} detector 1 ^B coating thicknesses were homogenized in micrometer order Since the ratio between the pulse count value and the fluctuation component measurement value can be made constant, this embodiment can be realized.

In addition, by using Ar gas that has no secular change in the gas component due to radiation irradiation as the sealed gas of the ¹⁰ B detector 1, it is possible to eliminate the secular change in the ratio between the pulse count value and the fluctuation component measured value.

In addition, the ¹⁰ B coating thickness of the ¹⁰ B detector should be a thickness in a range where the detection sensitivity with respect to the increase in thickness as shown in FIG. 2 is substantially constant and stable, and preferably a thickness in the center of this range. Therefore, even if the thickness varies, stable high sensitivity can be realized.

  Measurement values measured by the respective circuits are input to the measurement signal selection means 8. The measurement signal selection means 8 automatically selects a measurement circuit to be used for monitoring when the value of the measurement signal obtained from each circuit reaches a preset value.

As described above, by switching and applying pulse counting, fluctuation component measurement, and minute current measurement according to the measurement range, the signal obtained from the ¹⁰ B detector can be used in one measurement system. The start-up range, wide range, and power range can be monitored, and a neutron instrumentation system that is simpler than the conventional system can be obtained.

  In addition, subcriticality confirmation can be performed in both the new measurement system and the conventional PWR startup range, and the diversity of monitoring for subcriticality confirmation (without changing the layout around the current PWR reactor) ( Diversity) can be secured.

Here, an example of a ¹⁰ method for producing a ^B detector 1 by plasma sputtering. FIG. 3 is a schematic diagram showing an example of a method for uniformizing the coating thickness on the inner surface of the ¹⁰ B detector by plasma sputtering in the process of manufacturing the ¹⁰ B detector of the neutron instrumentation system of FIG. FIG.

  High frequency power is supplied to the ground electrode 21 which is a pipe to be coated, a center electrode 22 having a cylindrical conductor on its inner surface and a protruding tip, an insulator 23 which electrically insulates both, and two electrodes In addition to the power source 24 and the electrode moving means 25 for moving the center electrode 22 and the insulator 23 in the pipe 21, a gas supply device 33 is connected to the coating device 20 by a pipe 32. The supplied gas is introduced into the pipe 21 through the cavity 31 in the center electrode. The pipe 21 is exhausted, for example, in the right direction of FIG. 3 by a vacuum exhaust device (not shown).

  The supplied gas is a pure gas such as argon, helium, nitrogen, hydrogen, or a mixture of them in appropriate amounts.

  The gas supplied from the gas supply device 33 is guided to the coating device 20 by the pipe 32, and is supplied into the pipe 21 through a cavity formed in the center electrode 22. The pipe 21 is exhausted by a vacuum exhaust device (not shown), and the pressure in the pipe 21 is determined by the balance between the amount of gas supplied and the exhaust speed. At this time, a certain amount of the gas in the space is exhausted, and at the same time, the same amount of fresh gas is flowing. During the process in which the sputter material 27 is sputtered on the inner surface of the pipe 21 by the action of plasma, the gas adsorbed on the surfaces of the pipe 21 and the center electrode 22 and the gas components contained as impurities in the sputter material itself are plasma. Mixed in. The impurity gas component is exhausted out of the space by exchanging the gas in the sputtering space.

By such a method, impurities contained in the plasma being sputtered can be exhausted to the outside. With this manufacturing method, the ¹⁰ B coating thickness of the ¹⁰ B detector 1 in FIG. 1 can be made uniform on the order of micrometers.

DESCRIPTION OF SYMBOLS 1 ... ¹⁰ B detector 2 ... Reactor 3 ... Signal line 4 ... Monitoring unit 5 ... Pulse measurement circuit 6 ... Fluctuation component measurement circuit 7 ... Micro current measurement circuit 8 ... Measurement circuit selection means 21 ... Ground electrode (pipe)
22 ... Center electrode 23 ... Insulator 24 ... Power source 25 ... Electrode moving means 27 ... Neutron conversion layer 30 ... Plasma 31 ... Cavity tube 32 in the center conductor ... Pipe 33 ... Gas supply system

Claims (4)

In a neutron instrumentation system that measures neutron flux outside the reactor,
A pulse counting circuit that is placed outside the reactor and measures the startup range;
A micro current measurement circuit that is placed outside the reactor and measures the power range;
A fluctuation component measuring circuit arranged outside the nuclear reactor to measure a range between the pulse counting circuit and the minute current measuring circuit;
Connected to output to the pulse counting circuit, the minute current measuring circuit, and the fluctuation component measuring circuit, and the ¹⁰ B coating thickness on the inner surface of the detector has a stable and constant detection sensitivity with respect to the increase in thickness. A ¹⁰ B detector with a thickness in the range and uniform on the micrometer order and placed outside the reactor;
Based on the outputs of the pulse counting circuit, the minute current measuring circuit and the fluctuation component measuring circuit based on the output of the ¹⁰ B detector, the outputs of the pulse counting circuit, the minute current measuring circuit and the fluctuation component measuring circuit are output. A measurement signal selection means arranged outside the nuclear reactor to select one of them;
A neutron instrumentation system comprising: The neutron instrumentation system according to claim 1, wherein the ¹⁰ B detector is coated with ¹⁰ B by plasma sputtering. The neutron instrumentation system according to claim 1, wherein the ¹⁰ B detector is filled with Ar gas. In the neutron instrumentation method for measuring neutron flux outside the reactor,
The ^{10 B} coating thickness detector the inner surface, the ^{10 B} detector sensitivity is substantially equalized and a micrometer order in a thickness of constant are stable range for an increase in the thickness disposed outside the reactor,
A pulse counting circuit that measures the startup range is located outside the reactor,
A small current measurement circuit that measures the power range is placed outside the reactor,
A fluctuation component measurement circuit for measuring a range between the pulse counting circuit and the minute current measurement circuit is arranged outside the reactor,
Connecting the output of the ¹⁰ B detector to the pulse counting circuit, the minute current measuring circuit, and the minute current measuring circuit;
Based on the outputs of the pulse counting circuit, the minute current measuring circuit, and the minute current measuring circuit based on the output of the ¹⁰ B detector, the outputs of the pulse counting circuit, the minute current measuring circuit, and the minute current measuring circuit are output. To choose one,
A neutron instrumentation method characterized by

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