JPS6252487A - Neutron measuring device for nuclear fusion reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a neutron measurement device for a nuclear fusion reactor.

[Technical background of the invention and its problems]

Figure 3 shows the schematic configuration of a tokamak-type fusion reactor.
Plasma 1, which is an ionized gas of deuterium (D) and tritium (T>), is generated in a toroidal vacuum container 2, and energy is injected from the outside using a plasma heating device 8 to generate a temperature of about 100 million degrees. This heating causes a DT fusion reaction, resulting in the generation of high-energy neutrons of about 14 MeV.

Around the vacuum container 2, planchers 1 to 3 and a shield 4 are arranged.
are arranged in a circular pattern. The inside of the blanket 3 is filled with lithium (Li) for multiplying fuel tritium, and is provided with a large number of coolant channels for extracting the energy of high-energy neutrons. Therefore, in the blanket 3, the high energy neutrons generated by the nuclear fusion reaction react with 1-i to generate tritium and multiply, and at the same time, the high energy neutrons are decelerated in the coolant flow path, and the coolant flow path It is configured to extract fusion energy to the outside in the form of thermal energy using a coolant flowing through it as a medium. On the other hand, radiation such as gamma rays generated as a result of the nuclear fusion neutron flux and the reaction between the blanket 3 and neutrons is shielded by the shielding body 4 .

Further, around the blanket 3 and the shielding body 4, there is a toroidal magnetic field group 9 for creating a magnetic field in the toroidal direction inside the vacuum container 2, and a voloidal coil group 10 for creating a magnetic field in the voloidal direction. is set up.

[Toroidal magnetic field coil 9 and voloidal magnetic field] The superimposed magnetic field created by the coil 10 forms a donut-shaped magnetic surface inside the vacuum container 2. As a result, the high-temperature plasma 1 is kept in the illustrated shape without directly contacting the wall surface of the vacuum container 2, and is confined within the vacuum container 2. usually,
Plasma having an elongated cross-sectional shape as shown in the figure becomes unstable with respect to positional displacement in the vertical direction (up and down direction). Therefore, a plasma position control coil 11 is provided as a means for suppressing the positional displacement of the plasma 1. In other words, when the plasma 1 is displaced in the vertical direction due to disturbance,
Plasma 1 is generated by passing a current through the plasma position control coil 11.
A magnetic field is created inside, thereby suppressing displacement of the plasma 1 in the vertical direction.

In the fusion reactor configured as described above, it is necessary to measure many plasma physical quantities such as temperature and density for core plasma diagnosis and control. As previously mentioned,
In a fusion reactor, fast neutrons (14 M
eV) and uses the neutrons to obtain heat output. The output of the fusion reactor is proportional to the number of DT fusion reactions per median time, that is, the number of 14 Mev neutrons generated. Therefore, the output can be measured by measuring the number of 14Mev neutrons generated in the plasma.

For this reason, neutron measurement devices are extremely important for output measurement and control, and various neutron measurement devices that measure nuclear fusion output, that is, the number of neutrons generated, are being considered.

However, all conventional neutron measurement devices measure the fusion output, that is, the number of neutrons generated, and assume that the position and shape of the plasma are constant. In reality, the position of plasma 1 may change constantly, and even if the number of neutrons generated in the entire plasma 1 is the same, detection may occur if plasma 1 moves in the direction closer to the detector during measurement. If the signal increases and, conversely, the plasma 1 moves away from the detector, the detection signal will become smaller, and a problem can be expected where the measurement result will appear as if the output (number of neutrons generated) has changed. .

Furthermore, conventional neutron measuring devices were intended to measure neutron energy spectral distribution, temporal and spatial distribution of neutron generation, and the like. Therefore, with conventional equipment,
It was necessary to install a large-scale shield in order to shield the gamma rays generated by the shield 4 (gamma rays act as measurement noise on the neutron detector).

In addition, in order to accurately measure R-energy neutrons in the vicinity of 14 MeV, it is necessary to measure the neutrons before they are decelerated by a blanket or the like, and therefore it is necessary to directly look into the core plasma 1. Therefore, it becomes necessary to provide a through hole directly from the core.

In contrast, nuclear fusion reactors are currently being designed to the level of experimental reactors in various countries, and nuclear fusion has moved from the physical stage to the engineering and experimental stages, but as a measurement device for a commercial reactor, , minimizes the impact on the furnace body,
It is necessary to reduce the size.

[Purpose of the invention]

An object of the present invention is to provide a neutron measuring device for a fusion reactor that can always measure the output of core plasma with high precision even when the position and shape of plasma fluctuate without being affected by the fluctuations. .

[Summary of the invention]

The neutron measurement device of the present invention installs neutron detectors at multiple locations around the torus cross section of a fusion reactor so as to be close to the plasma, and monitors and processes the detection signals of these detectors to measure the plasma. It is a force that enables output measurement that is unaffected by changes in position and shape.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG.

FIG. 1 shows a part of a tokamak-type fusion reactor.
A measurement boat 6 that accommodates a neutron detector 5 is provided close to the vacuum vessel 2 .

A plurality of measurement boats 6 are installed to surround the plasma 1 (
A small neutron detector 5 is installed inside the nuclear measurement port 6. In the figure, in particular, a detector installed above the plasma 1 is shown as 5A, and a detector installed below the plasma 1 is shown as 5B. Furthermore, as these neutron detectors 5, one with low sensitivity to gamma rays, such as a 2i1ff U fission coefficient tube used as a nuclear fission counter tube for light water reactors, will be used, and no special shielding for gamma rays will be provided. do. A signal cable 7 for extracting ionizing current is led out from the neutron detector 5.

The detection signals of each of the neutron detectors 5 are input to the position calculation unit 12 as shown in FIG. 2, and FIG. 2 particularly shows the detector 5A above the plasma and the detector 5B below the plasma. . - In the position calculation section 12, the detector 5
A difference signal between the detection signals A and 5B is taken, and based on the difference signal, the amount of vertical displacement of the plasma 1 is calculated with the equilibrium position as a reference. The difference signal from the position calculation unit 12 is
The signal is input to a position 31 node unit 13 which has arithmetic functions such as proportional, integral, and differential (hereinafter referred to as PID). This position adjustment section 1
Reference numeral 3 is composed of an operational amplifier, a digital meter, or the like, and performs calculations such as the above-mentioned PID on the difference signal from the position calculation section 12 and outputs it to the power supply control section 14 . The power supply control section 14 has a computing device such as a PID, and is a control regulator for providing a drive signal to the position control coil power supply section 15.

This power supply control section 14 is composed of an operational amplifier or a digital bullet meter, detects the signal input from the position adjustment section 13, and outputs a drive signal for driving the position control coil power supply section 15. Here, the position calculation section 12, the position adjustment section 13, the power supply control section 14, and the position control coil power supply section 15 constitute means for monitoring and processing the detection signal of the neutron detector 5, and serve as a means for controlling the position. The coil power supply section 15 generates an output voltage for exciting the plasma position control coil 11 based on the output signal from the power supply control section 14 .

In the above configuration, when the plasma position is at the equilibrium position, the number of neutrons reaching the neutron detectors 5A and 5B, which are installed symmetrically with respect to the plasma center, is the same. Therefore, the difference signal between the signals from the neutron detectors 5A and 5B becomes zero. On the other hand, if the plasma is displaced vertically upward, for example, the neutron detector 5A installed above the plasma
The detection signal of the neutron detector 5B increases, and conversely, the detection signal of the neutron detector 5B installed below the plasma decreases. Since it is considered that there is a one-to-one correspondence between the difference signal of the neutron detections 55A and 55B and the amount of plasma displacement, the amount of plasma displacement can be calculated from this difference signal. Therefore, by confirming the relationship between the difference signal and the amount of plasma displacement in advance, for example, through a numerical experiment or an experiment in a real system, and providing the position calculation function with the calculation function, the detection for controlling the plasma position can be performed. It can be used as a signal.

With the above configuration, for example, when the position of the plasma 1 shifts upward from normal, the signal level of the detector 5A disposed above increases, and the signal level of the detector 5B disposed below decreases. Therefore, by comprehensively processing the signals from all detectors, it becomes possible to accurately measure the core plasma output without being affected by the instability of the plasma position and shape.

As described above, according to this embodiment, it is possible to perform highly accurate output measurement that is not affected by fluctuations in the position and shape of the plasma, and at the same time, it is possible to use a neutron detection signal as a detection signal for controlling the position of the plasma.

Note that the present invention is not limited to the above embodiments.

For example, in the above embodiment, a neutron detector for a light water reactor is used.
Although a 3"rU fission counter is assumed, instead of a 2"5IJU, 238U, Th, etc., which are highly sensitive to high-energy neutrons, may be used.

〔Effect of the invention〕

As described above, according to the present invention, neutron detectors are arranged at multiple locations around the cross section of the fusion reactor torus so as to be close to the plasma, and the detection signals of these detectors are monitored and processed. , it is possible to measure the core plasma output with high precision, which is not affected by fluctuations in the position and shape of the plasma.
We are able to provide a neutron measurement device that can also be used as a position detector for plasma position control.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is a sectional view showing the arrangement of a neutron detection device, and FIG. 2 is a means for monitoring and processing the detection signal of the neutron detector. FIG. 3 is a cross-sectional view of the fusion reactor. 1-...Plasma, 5.5A, 5B...Neutron detector, 12...Position calculation section, 13...Position adjustment section, 14
...-power supply control section, 15...position control coil power supply section. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (2)

[Claims] (1) The fusion reactor is equipped with neutron detectors installed close to the plasma at multiple locations around the torus cross section, and means for monitoring and processing the detection signals of these neutron detectors. A neutron measuring device for a nuclear fusion reactor. (2) The neutron measuring device for a fusion reactor according to claim 1, wherein the neutron detector is a fission counter for a light water reactor.