JPS6140334B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydrogen isotope measuring device capable of continuously measuring hydrogen isotopes, which is suitable for detecting damage to fuel assemblies, control rods, etc. in a nuclear reactor, for example.

In the damaged fuel detection system, the nuclear fission products contain a considerable amount of tritium, and the boron in the control rods contains lithium as an impurity, and the lithium fissions to produce tritium, so tritium is extracted from these. Detection is important from the standpoint of nuclear reactor operation control.

The content of tritium has conventionally been measured using a gas method in which the tritium is directly passed through a measuring device such as a gas flow counter or proportional counter.

Furthermore, when tritium is mixed with other gases, a semiconductor radiation detector is used to detect tritium and measure its content.

However, when the tritium content is small, there is a drawback that the amount of tritium cannot be accurately measured due to the background and the performance of the detector.

Therefore, it has become necessary to take out the tritium mixed in radioactive materials by some means, or to reduce the background noise and improve the performance of the detector.

However, there are drawbacks such as the need for various types of equipment, which makes the equipment itself complex and expensive. Proposed. This device will be explained with reference to FIG.

That is, the opening 2 of the gas chamber 1 to be measured, whose upper part containing the gas to be measured is only partially shown, is removably closed by a flange 3, which is connected to the hydrogen isotope detection section 4. A tubular body 5 is attached therethrough in an airtight manner. A bottomed tubular diffusion membrane section 6 made of metal such as nickel or stainless steel that selectively permeates hydrogen is connected to the lower end of the tubular body 5, and a heater 7 is directly wound around the outer surface of this diffusion membrane section 6. It's being passed around. The heater 7 is controlled to a predetermined temperature by a temperature control device 9 based on a signal from a temperature detection element 8.

Furthermore, a transport gas supply pipe 10 that penetrates the tubular body 5 from outside the measurement chamber 1 is suspended within the diffusion membrane section 6 . The transport gas supply pipe 10 is connected to a transport gas source 12 via a valve 11, and the detection unit 4 is provided with a valve 13, which is connected to the valve 13 for discharging the gas after measurement. Here, temperature control of the diffusion film section 6 must be performed accurately because it directly affects the performance of the detection section 4. As the transport gas, a rare gas such as helium or argon containing a small amount of hydrogen is used so that hydrogen, tritium, etc. in the gas to be measured can easily permeate selectively to the diffusion membrane section.

In the hydrogen isotope measurement apparatus shown in FIG. 1, the heater 7 is directly wound around the surface of the diffusion membrane section 6, so that the membrane section 6 is directly affected by the surface temperature of the winding 7a, and the membrane section 6 There is a temperature gradient upward from the lower end of the membrane part 6, and it is further affected by the transport gas flowing inside the membrane part 6, so that it is difficult to accurately control the temperature.

In addition, since the flow of the gas to be measured flowing on the surface of the membrane part 6 is obstructed by the heater 7, hydrogen and tritium in the gas to be measured have an adverse effect when permeating through the membrane part 6, so accurate hydrogen isotope concentration can be measured. This was a difficult drawback.

The present invention has been made to eliminate the above-mentioned drawbacks, and has a diffusion membrane that selectively transmits hydrogen and tritium, which eliminates the temperature gradient on the surface of the diffusion membrane without being affected by the surface temperature of the heater. By eliminating the influence of the transport gas, it is possible to accurately control the temperature of the diffusion membrane part, and by eliminating the influence of the flow of the gas to be measured due to the heater, it is possible to measure the concentration of hydrogen isotopes with high reliability and accuracy. The purpose of this research is to provide hydrogen isotope measurement surveys.

Hereinafter, one embodiment of the hydrogen isotope measuring device according to the present invention will be described with reference to FIG.

Note that in FIG. 2, the same parts as in FIG. 1 are indicated by the same reference numerals, and explanations of overlapping parts are omitted. That is, in this invention, the flange 3 is directly attached horizontally to the opening 2 of the gas chamber 1 to be measured,
A cylindrical body 2 through which gas to be measured flows through this flange 3
0 is fixed. This cylindrical body 20 is provided with a gas inflow hole 21 and an outflow hole 22 through which the gas to be measured flows from below to above. This cylindrical body 2
A tubular body 5 made of stainless steel, for example, is attached inside the housing 0. A sleeve-shaped diffusion membrane portion 6 is connected to the tubular body 5 from the center downward.
As the diffusion membrane portion 6, palladium, iron, nickel, or the like, which selectively permeates hydrogen, is used. A first heat source 23 is provided below this diffusion film section 6,
Also, the tubular body 5 near the gas outlet hole 22 of the tubular body 20
A second heating source 24 is provided. The heating sources 23 and 24 are adjusted to a predetermined temperature by temperature detection elements 25 and 26 and temperature control devices 27 and 28. Above the flange are a transport gas source 12 and isolation valve 11 for transporting hydrogen and tritium that have passed through the membrane section 6 to the detection section 4, and a hydrogen isotope detection section 4 that detects the transported hydrogen and tritium. A hydrogen isotope measuring device is constructed by installing an atmospheric isolation valve 13.

Note that the transport gas is heated by a third heating source 29 attached to the transport gas nozzle 10. This heating source 29 is adjusted to a predetermined temperature by a temperature sensing element 30 and a temperature control device 31. In such a measuring device, the gas inflow hole 2 of the cylindrical body 20
The gas to be measured flowing in from the first heating source 23 is heated by the first heating source 23, rises due to buoyancy, passes through the flow path 32, and is discharged from the gas outlet hole 22.

In other words, gas is circulated using natural convection generated by the cylindrical body 20, the first heating source 23, and the second heating source 24, the first heating source 23 heats the gas to be measured, and the gas to be measured forms a film. Heat section 6.

Furthermore, by providing the second heating source 24 to prevent heat from escaping from the tubular body 5 due to heat conduction, the membrane portion 6 can eliminate the influence of the surface temperature caused by the direct heating source 23, and eliminate the temperature gradient from the bottom to the top. It becomes possible. Here, the transport gas is further adjusted to a predetermined temperature using a third heating source 29, a temperature detection element 30, and a temperature control device 31, so that the membrane part 6 can be accurately adjusted.
temperature control function can be maintained.

In addition, temperature sensing elements 25, 26, 30 in FIG.
For example, a thermocouple is used, and the cylindrical body 20 is a heating or shielding body. Here, in the present invention, the gas flows in from the gas inflow hole 21 of the cylindrical body 20, is heated by the first heating source 23, is maintained at a predetermined temperature, passes through the membrane part 6, and is transported by the hydrogen isotope detection part. 4 and is detected.

In other words, forced circulation by natural convection is possible without attaching the first heating source 23 to the surface of the membrane part 6, which eliminates the negative effects of hydrogen and tritium in the gas to be measured when they permeate through the membrane part 6, thereby ensuring accuracy. It becomes possible to provide a hydrogen isotope measurement device that can measure the concentration of hydrogen isotopes.

For example, in the apparatus shown in FIG. 1, when the temperature is raised to a set value of 500°C using only the heater 7 on the surface of the membrane part 6, the temperature gradient is 50°C from the lower end to the upper end when the length of the membrane part 6 is 100 mm. Since it is directly affected by the surface temperature of the heater 7 and by the transport gas, it is very difficult to maintain the set value and it always fluctuates within a range of ±10°C.

Next, calibration was performed using a standard gas, and the irregular distribution of measured values was about ±20%, resulting in extremely poor reproducibility.

On the other hand, in the device according to the present invention shown in FIG. 2, when the set value of the membrane section 6 is also set at 500°C, no temperature gradient is observed and the set value can be maintained within ±2°C. Ta.

Next, we performed calibration using a standard gas, and as a result, we obtained results with very good reproducibility and no variation.

In other words, according to the present invention, it is possible to perform temperature control with high precision, and furthermore, it has become possible to eliminate the adverse effects when hydrogen and tritium permeate through the membrane portion 6, and to obtain a reliable hydrogen isotope concentration.

As described above, according to the present invention, since the temperature sensing element can be directly attached to the diffusion membrane part that selectively permeates hydrogen and tritium, The gas to be measured can be circulated by the natural convection that occurs, and the third heating source 29 can eliminate the adverse effects of the transport gas, making it possible to accurately control the temperature of the diffusion membrane section. Therefore, there is no adverse effect when hydrogen and tritium permeate through the membrane portion 6, and a highly reliable hydrogen isotope measuring device can be provided.

Furthermore, by heating the diffusion membrane section using natural convection, it is possible to directly measure the hydrogen isotope in the hydrogen isotope detection section.

Furthermore, since there is no need for a sampling line for the gas to be measured, the device can be significantly downsized, can be installed in locations with limited space, and has the effect of reducing costs.

[Brief explanation of the drawing]

FIG. 1 is a partially block sectional view of a conventional hydrogen isotope measuring device, and FIG. 2 is a partially block sectional view of an embodiment of the hydrogen isotope measuring device according to the present invention. DESCRIPTION OF SYMBOLS 1... Gas to be measured, 2... Opening, 3... Flange, 4... Hydrogen isotope detection section, 5... Tubular body,
6... Diffusion membrane section, 7... Heater, 8... Temperature detection element, 9... Temperature control device, 10... Transport gas supply pipe, 11... Valve, 12... Transport gas source, 1
3... Valve, 20... Cylindrical body, 21... Gas inflow hole, 22... Gas outflow hole, 23... First heating section, 24... Second heating source, 25, 26, 30...
... Temperature detection element, 27, 28, 31 ... Temperature control device, 29 ... Third heating source, 32 ... Gas flow path.

Claims (1)

[Scope of Claims] 1. A gas chamber to be measured, a detection section arranged outside the gas chamber for detecting a hydrogen isotope, and a gas chamber connected to the detection section and inserted airtight into the gas chamber to be measured. A tubular body connected to a diffusion membrane portion that selectively permeates hydrogen, and a transport gas source placed outside the measured gas chamber inserted into the tubular body via a valve and extending to the vicinity of the lower portion within the diffusion membrane portion. A cylindrical body having a hanging transport gas supply pipe, a gas inflow hole and an outflow hole that are provided in a gas to be measured chamber and surround the tubular body with a space therein, and allow the gas to be measured to flow from below to above. , a first heat source disposed at the lower part of the cylindrical body that indirectly heats substantially the bottom of the outer surface of the diffusion membrane portion; and a second heat source that directly heats substantially the vicinity of the connection portion between the cylindrical body and the diffusion membrane portion. A hydrogen isotope measuring device comprising: a heating source; and a third heating source that heats a transport gas supply pipe outside the measured gas chamber. 2. The hydrogen isotope measurement device according to claim 1, wherein the transport gas is heated to a predetermined temperature by a heating source, temperature-controlled, and then flows into the diffusion membrane section. 3. A patent characterized in that each of the first to third heating sources is provided with a temperature control device that controls the temperature to an arbitrary temperature based on a signal from a temperature detection element, and maintains the gas to be measured at a predetermined temperature. Claim 1
Hydrogen isotope measuring device described in Section 2.