JPS586456A - Detector for lithium metal - 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 Field of the Invention The present invention relates to a lithium metal detection device, and more particularly to an improved metal detection device for detecting thermally ionized lithium particles or vapors, or mixtures of such lithium particles or vapors. Regarding sensors.

Prior art alkali metal detection devices have been described in numerous publications, and more details have been published in 2019. U.S. Pat.
U.S. Pat. @//'JJ? It is listed in item A.

Prior art alkali metal detection devices have an electrically heated filament electrode, typically a Sing-coated Mo8i1-cermet wire, and a collector electrode, typically plate-shaped.

The filament electrode is heated to about 900° C. by a first electrical circuit and exposed to an atmosphere or carrier gas in which the alkali particles of interest are believed to be present. Upon contact between the filament electrode surface and the particles, the particles are thermally dissociated (if the particles are an alkaline compound), become positively ionized, and evaporate from the filament electrode surface to produce positive ions. The electric field created between the filament electrode and the collector electrode by the second electrical circuit moves the ions to the collector electrode, creating an ionic current that can be detected with a sensitive current needle. The magnitude of the ionic current indicates the presence and concentration of alkali metal in the gas atmosphere to which the heated filament electrode is exposed.

Alkali metal detection equipment is mainly used in fast neutron breeder reactors) It is used as an alarm monitor in the event that IJium leaks into the air. If sodium leaks, it reacts with air to form sodium and sodium compounds like airborne particles (smoke or other aerosols).

In order to detect such leaks, a highly sensitive alkali and metal detection device (approximately 3
"ll sensitivity" was developed, manufactured and sold by the Westinghouse Electric Company.

Recently, new applications for alkaline detection devices have been established.

Fusion reactors and fusion test systems incorporate systems containing large amounts of high temperature liquid lithium. The detection device, which is essentially identical in its relevant features to the commercially available device described in the above-mentioned patent specification, detects the presence of lithium in the air, since lithium, like sodium, burns in the air and produces smoke. Safe monitoring of leaks is desirable. Li0)I
, Li, O and Li,l:'O, in experiments with aerosols, the detection device did not respond, unlike similar experiments with Na)IJium compound aerosols.

The authors investigated the cause of the lack of responsiveness of the detection device to lithium and improved the detection device, making it possible to detect lithium.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to overcome the drawbacks of the prior art and to provide an improved lithium metal detection device.

The present invention provides a filament electrode for responding to collisions of the lithium atoms and lithium compounds in a carrier gas by ionizing the lithium atoms and lithium compounds on a heated surface to produce lithium cations; a first electrical circuit means for regulating and maintaining the temperature of the filament electrode above too'C for ionizing the compound; a collector electrode; and electrical circuit means for generating and detecting a flow of lithium cations indicating the presence and concentration of lithium cations.

The above-mentioned alkaline gold is in full swing! The device is modified so that the detector filament operates at significantly higher temperatures than normal. The detector filament in the detection of lithium must operate at temperatures above 10°C.

The invention will be explained in more detail below on the basis of exemplary embodiments and figures.

The filament temperature of the alkali metal detector is /10
Lithium is effectively detected when operated at or above 0°C. To do this, a filament ammeter is used as the filament's first electric circuit means, and a current adjustment means such as a variable voltage power supply is used to control the filament current to a predetermined value to achieve the desired filament temperature. can.

The relationship between filament temperature and filament current is determined by using an optical pyrometer and referring to a calibration curve determined under operating conditions where other parameters such as atmospheric gas flow are held constant, if any. .

FIG. 1 (prior art) is a diagram showing the response curve of a standard Westinghouse alkali metal detection device that has been developed.

W, Figure 1 shows the relationship between the net response value (signal minus background) of the detection device on the vertical axis (/) and temperature on the horizontal axis (co) for sodium and potassium compounds. It is clear from this figure that the net response of the aerosol detection device containing NaOH and KOH ([4' is
Approximately i of background 3 in all measured temperature ranges
It is o times.

This dissociates sodium and potassium compounds at the low temperatures at which the detection device normally operates (approximately 900°C);
It also shows that the temperature is sufficient to ionize the generated alkali metal atoms. Although the net response value of the sensing device increases somewhat by operating at higher temperatures, it is believed that operating at such higher temperatures shortens the lifetime of the filament. Since the response value of the detection device at 900°C is sufficiently greater than the background, operation at 100°C is preferred.

FIG. 1 shows curves similar to FIG. 1 for the lithium compounds LiOH, Ll, and Co. These behaviors are markedly different from those for sodium and potassium. The net response value of the detector at a filament temperature of 900° C. is at most 10 times smaller than the background A (the response value is essentially zero). 10OOC~/10
At 0° C., as shown in FIG. 2, the net response value of the detection device exceeds the background signal, making it possible to detect lithium. When the filament temperature is high (tt00
The behavior of the response value to lithium is only at ℃) IJ
um and potassium, ie, at least an order of magnitude above background. Obviously, a filament operating temperature of around 7100°C is suitable for detecting lithium.

A possible theoretical explanation for these experimental results is that lithium compounds are very ξ compared to sodium and potassium compounds.
This is thought to be due to its stability. #1 Table lists the dissociation enthalpies of related compounds. IJium and potassium hydroxide have almost the same values, whereas lithium compounds require more energy to dissociate. This is almost qualitatively consistent with the filament temperature relationship, but in reality these compounds may dissociate and catalyze reactions at surfaces consisting essentially of Sing), so the applicable net dissociation is I don't know about enthalpy.

Since the thermal ionization reaction is considered to be a catalytic reaction, not only the filament temperature but also the properties of the filament electrode are important. The response values of the detection device shown in FIG. 2 were obtained using LloSil-cermet wire coated with Sin.

Li0H-H,O/l11.77 Li, GO, Ko? OJ 4I NaOH10/, 99! FIG. 3 is a schematic diagram of a Westinghouse alkali metal detection system modified to operate in ore cars at 1100° C. or higher for lithium detection. Detector housing
The filament electrode is in fluid contact with the ant electrode. The carrier gas stream may include lithium ions/and aerosol-like lithium-air reaction products.

The filament electrode 7 is connected to a variable voltage power source /j.

Using a calibration curve similar to that illustrated in FIG. The ionic products 12 generated in contact with the filament electrode 7 become lithium ions //, which are attracted to the collector electrode t by the electric field generated by the bias power supply /f. The ion current is read with an ammeter or an alarm is issued.

A model of the detection device with a filament electrode temperature of /100° C. was successfully tested and detected lithium.

Although the general apparatus according to the invention has been described, it should be understood that various modifications can be made without departing from the true spirit and scope of the invention. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.

[Brief explanation of drawings]

FIG. 9 is a schematic diagram showing the Estinghaus sodium detection device, and FIG. 9 is a diagram showing a typical filament temperature calibration curve. In the figure, (θ...vertical axis, (blade...horizontal axis, 3...background, da...net response value of the detection device, 3...detection device housing, 6...carrier gas flow. 7.・Filament electrode, za・Collector electrode, q,
io... ammeter, //... lithium ion, 7.2-@
Ion product, /q...bias power supply, /j...variable voltage power supply. Patent Applicant's Agent Terufitsument X&l@C) FIG, 1 Filament 1d Button (@G) FIG, 2

Claims (1)

[Scope of Claims] 1.1J A filament electrode for responding to collisions of said lithium atoms and lithium compounds in a carrier gas by ionizing said lithium atoms and lithium compounds at a heated surface to produce lithium cations; a first electrical circuit means for constantly maintaining the temperature of the scissor filament electrode at 7000° C. or higher to ionize lithium atoms and lithium compounds; a collector electrode; and a carrier gas from the filament electrode to the collector electrode. 1. A lithium metal detection device, comprising: electric circuit means for generating and detecting a flow of lithium cations indicating the presence and concentration of lithium in the mold. MO81g with filament electrode coated with Sin
- The lithium metal detection device according to claim 1, which is a cermet wire. 3. The lithium metal detection device according to claim 1 or 2, wherein the first electric circuit means includes a variable voltage power supply.