JPS593334A - Detector for water leakage - Google Patents

Abstract

PURPOSE:To improve the accuracy in controlling the temp. of a hydrogen permeable film and the ease of the control, by heating the permeable film with a metallic piece which incorporates a heater and a temp. measuring element and is held in tight contact with the surface of said film. CONSTITUTION:A metallic piece 12 disposed so as to be held in tight contact with the inside of a hydrogen permeable film 2 is a palladium alloy having high hydrogen permeability and the film 2 is commonly used nickel. A heater 11 of a sheathed type which heats the film 2 and a sheathed type thermocouple 13 which detects the temp. of the film 2 are embedded in the palladium alloy. The material of the piece 12 may be not only the palladium alloy but also be any material as far as it has large hydrogen permeability, permits installation of the heater 11 and the thermocouple 13 and has the larger heat capacity than the heat capacity of the film 2 and may be a sintered alloy, a wire net, etc. The temp. of the film 2 is made controllable with good accuracy with difficulty in receiving the influence of the fluctuation in the temp. and flow rate of a cover gas 8 admitted into a housing 7 and without inaccuracy by heating with the cover gas 8 by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water leak detector for a fast reactor steam generator, and particularly to a hydrogen permeable membrane heating method suitable for a water leak detector in a cover gas.

Water leak accidents from steam generators should be detected by monitoring the total amount of hydrogen in the sodium or cover gas. FIG. 1 is an example of a conventional water-in-cover gas leak detector. A housing 7 is provided with a detection end having a hydrogen permeable membrane 2 made of a thin nickel film or the like, through which a portion 8 of the cover gas of the steam generator containing hydrogen is collected.
lead to. The gas 8 that has entered the housing flows around the hydrogen permeable membrane 2 and exits the housing 7. Inside the hydrogen permeable membrane 2 is an isolation valve 4f! By the vacuum pump (ion pump) 6 provided at the tip of the vacuum exhaust pipe 3 having r, 6 i o-' ~
10-' toll vacuum. The vacuum exhaust pipe 3 is connected to a vacuum gauge (9 meters) 5 for measuring pressure.

Hydrogen in the gas 8 flowing around the hydrogen-permeable membrane 2 permeates into the interior of the hydrogen-permeable membrane 2 which is kept in a vacuum due to the pressure difference between hydrogen on both membrane surfaces of the hydrogen-permeable membrane 2 .

The amount of hydrogen that has permeated can be determined by the pressure indicated by the vacuum gauge 5 or by the change in the current value required by the vacuum pump 6 to exhaust hydrogen.

The amount of hydrogen permeated through the hydrogen permeable membrane 2 depends on the material of the hydrogen permeable membrane 2 and the degree of permeable membrane control. A nickel film with a thickness of 0.25 to 0.5 is used as the hydrogen permeable membrane in a typical water leak detector, and the temperature of the permeable membrane is controlled to be constant at around 500C. When the permeable membrane temperature is 500C, the control range is 5
00C±2C, but the hydrogen concentration measurement value is within ±2C (
4) with measurement errors due to temperature fluctuations. If it exceeds this value, it becomes difficult to measure low hydrogen at 11 degrees.

For water-in-sodium leak detectors, this temperature control range does not pose much of a problem, but in water-in-gas leak detectors, the fluid is gas and the hydrogen permeable membrane itself has a small heat capacity, so the temperature of the permeable membrane cannot be adjusted accurately by heating the gas. Difficult to control well.

An object of the present invention is to provide a heating method that can easily and accurately control the temperature of the hydrogen permeable membrane of the above-mentioned water-in-cover gas leak detector.

As a method for improving the problems of the conventional example, the present invention provides a metal piece with a built-in heater and a measuring body, which has a larger heat capacity than the hydrogen permeable membrane that is in close contact with the surface of the hydrogen permeable membrane. This method aims to improve the temperature control accuracy and ease of control of the hydrogen permeable membrane by heating the hydrogen permeable membrane.

A palladium alloy is used as the metal piece when the metal piece is in contact with the inner surface of the hydrogen permeable membrane (]!lc empty side), and a sintered metal is used when the metal piece is in contact with the outer surface that is in contact with the cover gas 8 containing hydrogen.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3. The present embodiment is illustrated with the hydrogen permeable membrane 2fr housing 7 and vacuum exhaust pipe 3 extracted from FIG.

The metal piece 12 is placed in close contact with the inside of the hydrogen permeable membrane 2? The arrangement is shown in Figure 2. The metal piece 12 is made of a baradium alloy with high hydrogen permeability, and the hydrogen permeable membrane 2 is made of normally used nickel. Baladium alloy is often used to purify hydrogen gas, and has a hydrogen permeability approximately 10 times that of nickel, but it has extremely poor corrosion resistance against sodium, which is included in the cover gas 8 together with hydrogen, and does not come into direct contact with the cover gas. It's like that.

Here, if the thickness of the hydrogen permeable membrane 2 is 0.25 rag and the thickness of the baradium alloy is k 2.5 wm, the entire hydrogen permeable part will be formed. Comparable to hydrogen detection end.

A sheath type heater 11 with a diameter of about 1 mm is used to heat the hydrogen permeable membrane 2 for the baladium alloy with a thickness of 2.5 tIan.
A sheath type thermocouple 13 with a diameter of about 0.5 to 1 m is embedded to detect the temperature of the hydrogen permeable membrane 2. Heater 11, thermocouple 1
Possible embedding methods of 3 include directly casting both parts into a rosemium alloy, or creating and embedding grooves in the same alloy.

The material of the metal paulownia piece 12 is not only palladium alloy but also a material with high hydrogen permeability. All thermocouples 13 can be attached, and any material having a larger heat capacity than the hydrogen permeable membrane 2 may be used, and sintered public metal, wire mesh, etc. may be used.

Figure 3 shows a heater 11 and a thermocouple 1 on the outside of the hydrogen permeable membrane 2.
3i and a built-in metal piece 14 is arranged therein. Since the cover gas 8 comes into direct contact with the metal piece 14, sintered metal, wire mesh, or the like is used here as the metal piece 14. Figures 2 and 3
The illustrated housing 7 is provided with an auxiliary heater 10.

According to this embodiment, the hydrogen permeable membrane has high precision, which is not affected by temperature fluctuations and flow rate fluctuations of the cover gas 8 flowing into the housing 7, and which completely reduces the uncertainty caused by heating via the cover gas 8. 2 control temperatures can be obtained.

According to the present invention, the temperature control of the hydrogen permeable membrane of the water in cover gas leak detector can be easily performed with high accuracy.
This improves the reliability of hydrogen concentration measurements caused by changes in the hydrogen permeable membrane temperature in the detector, and also improves measurement accuracy at low hydrogen concentrations.

[Brief explanation of drawings]

Figure 1 shows the cross section of the water leakage detection end and the detection end mounting part, and the measurement system? The figures shown, FIG. 2, and FIG. 3 are diagrams showing a cross section of the detection end extracted from FIG. 1. ■...Detection end, 2...Hydrogen permeable membrane, 11...Heater, Koto 2 concave 7 Figure 3

Claims (1)

[Scope of Claims] 1. A water-in-gas leak detector having a hydrogen-permeable membrane, characterized in that a heater is disposed in a block casing on the inner edge so as to be in close contact with the surface of the hydrogen-permeable membrane. 2. A water leak detector according to claim 1, characterized in that a metal piece having a larger hydrogen permeation rate than a hydrogen permeation membrane is used for the block. 3. The water leak detector according to claim 1, characterized in that the block is made of a metal piece or the like having a large heat capacity as well as a hydrogen permeable membrane.