JPS60174933A - Hydrogen fluoride gas analyzer - 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 Application of the Invention] The present invention provides a hydrogen fluoride (HF) gas analyzer with j'f,
h'-'-M 19ruA=-//TTD-1x-
The slight 1 that inevitably exists as p+ryτ pair +Jbh+
The present invention relates to an HF gas analyzer suitable for online analysis of iHF gas concentration in piping.

[Background of the invention]

In a UFs gas handling plant, a small amount of HF gas inevitably exists in the piping. The reason is that UF6 gas immediately causes the following reaction in the presence of HzO.

U Fs +2 HxO−”UOzF+ +4HF ・
(1) UFs gas itself is a corrosive gas, but HF gas is a highly corrosive gas that is even more so, and constant monitoring of its concentration is essential in terms of plant reliability. Furthermore, as can be seen from equation (1), if an accident such as a crack in a plant pipe occurs, the HF gas concentration will rise rapidly, so monitoring transient changes in the HF gas concentration will lead to accident detection.

As mentioned above, in the UF6 gas handling plant,
Constant online monitoring of the steady-state value and transient changes in the HF gas concentration in the piping is essential from the standpoint of plant reliability.

A conventional example of HF gas concentration analysis in UFa gas is a gas chromatograph (A, Q, Hamlin).

etal, , Anal, Chem,, 35
, 2037 (1963)).

Mass spectrometry (Koaki Heno et al. 9 Atomic Energy Society of Japan 1972 Annual Meeting, Proceedings A7. (1972)), and infrared absorption spectroscopy (
Ken Owada et al. 9 Journal of the Atomic Energy Society of Japan.

■, 77 (1975)). Gas chromatographs have corrosion resistance, especially column corrosion resistance, which is a problem in online measurements.
It is necessary to constantly exhaust Fa gas. In addition to being a nuclear fuel material, UF6 gas immediately generates highly corrosive I(F gas) according to equation (1) at the time of exhaust, so the exhaust treatment of this HF' gas becomes a problem.Gas chromatograph Another problem is that it does not have enough responsiveness to track transient changes in HF gas concentration.In the case of mass spectrometry,
However, corrosion resistance is a problem, and the ion source has a long lifespan, making it unsuitable for online use. In addition, like gas chromatographs, there are problems with analysis piping, exhaust systems, and responsiveness. On the other hand, in the case of infrared absorption spectroscopy, since light is probed, problems with corrosion resistance can be avoided by performing spectroscopy from outside the plant piping, and the response is also sufficient. However, there is a problem in that the detection limit is large (0.5 to 1 Torr, Owada et al., cited in the Journal of the Atomic Energy Society) and cannot be put to practical use.

Each of the techniques described above cannot be used to constantly monitor the concentration of HF gas flowing in the pipe or to constantly monitor transient changes.

In addition, thermal lens refraction spectroscopy (A, C-Boccara et al.) has the advantages of infrared absorption spectroscopy and has a detection limit comparable to that of photoacoustic spectroscopy.

Appl, phys, Lett, 36.130
(1980)). This principle is briefly illustrated using FIG.

The intensity of excitation light 2 from an excitation light source 1 is modulated using a chopper 3, and is irradiated through a lens 4 to a portion of a sample 5 to be analyzed. Heat generated by absorption of the excitation light by the sample 5 is transmitted to the periphery of the sample in synchronization with the modulation of the excitation light 2 by the chopper 3, forming a thermal lens region 6. Therefore, the probe laser beam 8 from the globe laser 7 passing near the sample is refracted in synchronization with the modulation of the chopper 3. The amount of refraction is measured by a probe light receiver 9 such as a position detector or a plurality of photodetectors. Since the amount of refraction is quantitatively linked to the concentration of molecules or atoms to be analyzed in the sample, quantitative analysis is possible. Also, like the photoacoustic method, since the absorption of the excitation light 3 is not directly measured, there is no effect of scattering, etc., and it has the advantage that the sensitivity increases as the excitation light intensity increases, and its detection sensitivity is the same as that of photoacoustics. It is of excellent quality.

[Purpose of the invention]

An object of the present invention is to provide an HF gas analyzer that can accurately analyze HF gas concentration using thermal lens refraction spectroscopy that eliminates the influence of fluctuations in the flow of UF6 gas.

[Summary of the invention]

The present invention is based on the fluctuation of the gas flow by passing the probe laser beam through a beam sinter to the outside and inside of the thermal lens region in the gas. By separating the displacement of the globe laser beam with refraction due to the Shinze effect and amplifying and measuring these displacements using a refractive optical element,
HF gas analysis has been achieved that allows continuous online analysis of the HF gas S degree in the piping of a UF6 gas handling plant during steady and/or transient conditions using the method that effectively offsets the displacement caused by fluctuations in the gas flow. It is.

A basic study was conducted using the equipment configuration shown in Figures 2 and 3.

FIG. 2 is a diagram of the analysis section viewed from the cross-sectional direction of the pipe, and FIG. 3 is a diagram viewed from the lateral direction. HF laser 10 was used as the excitation light source, and HeNe laser 1 was used as the globe laser.
1 was used. In addition, CaFz windows 13 were provided in the transmission region of the excitation light 2 and the probe laser light 8 provided in the pipe 12. A junction type light receiver 14 with two light receiving elements connected is used as the globe light receiver, and its detected intensity is measured using a lock-in amplifier 15 synchronized with the chopper 3, and the amount of refraction of the probe laser light 8 is measured. I met. In the above configuration, the pipe 12 was removed and installed in the break-break -f+. Piping 12
A mixed gas 1 of UF6 gas and HF gas is used as shown below.
I played 6. The gas flow configuration used in the experiment is shown in FIG. 4, and the analysis system shown in FIGS. 2 and 3 was installed at the analysis point 17 surrounded by the dotted line. UFs introduced into pipe 12
Gas is supplied from a UFs gas cylinder 18. The HF gas concentration was set using the H20 tank 19 using the vapor pressure and equation (1). These gases were circulated in the pipe 12 by the circulation pump 20. As a preliminary preparation, piping 1
2. Sufficiently expose the inner wall to U Fs gas and HF gas,
The experiment was conducted after the reaction and adsorption amount were saturated. The gases used in the preparation stage were liquid nitrogen trap 21 and NaF)
The air was evacuated through the wrap 22 by an exhaust pump 23. The experimental results are shown in FIGS. 5 and 6. These are UFs pressure 10 TOrr.

HF pressure 8 x I Q""'l'orr and 0.8
This is for the case of X 10-3 Torr. FIG. 5 shows the results when the necrosis pump 20 was driven, and it was found that similar signals were given even if the HF pressure was different by a factor of 10.

On the other hand, FIG. 6 shows the results when the circulation pump 20 is stopped and the conditions are the same as those for experiments in gas-filled cells conventionally carried out on a laboratory scale. )-dependent signals were obtained. That is, it was found that the results shown in FIG. 5 were based on fluctuations in the gas flow. Furthermore, when the valve 24 of the UF6 gas pump 18 was opened to introduce UFs gas into the pipe 12 while the circulation pump 20 was being driven, it was found that the influence of pressure fluctuations appeared as shown in FIG.

From the above results, thermal lens refraction spectroscopy is shown in Figures 2 and 3.
In the configuration shown in the figure, HF in the piping of a UF6 gas handling plant is
It turns out that it cannot be applied to analysis.

The present invention has been made based on the above study results, and examples thereof will be shown below.

[Embodiments of the invention]

The configuration of a preferred embodiment of the present invention is shown in FIGS. 8 and 9. FIG. 8 is a cross-sectional view of the pipe 12, and FIG. 9 is a view from the side. An HF laser oscillator 10 is used as an excitation light source. ) (The F laser transmitter 10 emits a laser beam corresponding to the optical absorption line unique to the HF molecule, so it is not an idiot with good excitation efficiency, and it does not match the absorption wavelength of other gases such as UFa gas or N2 gas. As a means for obtaining the probe laser 8, a HeNe laser oscillator 11 with stable output and long life is used. A CaFz single crystal window 13 is used which does not have an absorption band and has excellent resistance to U F s and HF.

The beam splinter 24 of the globe laser beam 8 is composed of a half mirror 25 and a mirror 26. Glass windows 27A and 27B coated with fluorine to provide U Fs resistance and HF resistance are used for the piping portion through which the probe laser beam 8 passes.

Concave lenses 28A and 28B are used as refractive optical elements that amplify the amount of refraction of the globe laser beam 8.

Position detectors 9A and 9B are used as probe light receivers. As a position detector, an ordinary photodiode array (position resolution ~10 μm) is sufficient, and it can be periodically modulated.
UFa and H flowing through the CaF2 window 13 and the pipe 12
The mixed gas 16 of F is irradiated. A thermal lens region 6 is formed in the region through which the excitation light 2 passes, in order to non-radiatively de-excite the HF molecules excited by absorbing the excitation light 2 . The globe laser beam 8 is separated into υ two beams by the beam splinter 24, and one beam is split inside the thermal lens area 6,
One side has two fluorine coated glass windows on the outside.
7A and 27B. The probe laser light (below reference beam 29) that does not pass through the thermal lens region 6 is slightly deflected by the fluctuation of the mixed gas 16, and then passes through the concave lens 28.
The deflection is magnified at B, and the displacement is detected by the position detector 9B. On the other hand, the probe laser light (hereinafter referred to as analysis beam 30) passing through the thermal lens region 6 is deflected in synchronization with the modulation of the excitation light 2 due to refraction due to the thermal lens effect in addition to the fluctuation of the mixed gas, and is deflected in synchronization with the modulation of the excitation light 2. The displacement is detected by the position detector 9A. The signals from the position detectors 9A and 9B are processed by the data M'L control circuit 31 to subtract the displacement of the reference beam 29 from the displacement of the analysis beam 30 to remove the influence of the flow of the mixed gas 16. Only the amount of refraction based on the absorption of the excitation light 2 of the HF gas is extracted. Note that the components other than the piping 12 and the data processing circuit 31 are installed on a seismic stand. When the apparatus configurations shown in FIGS. 8 and 9 were installed in the gas loop shown in FIG. 4 described above and tested, the results shown in FIGS. 10 and 11 were obtained. Figure 10 is U
The result is when circulating F a 10 Torr + HFlXl0''Torr and IXI Q=4Torr,
The results showed good agreement with the analysis results obtained without gas circulation (Fig. 11). FIG. 12 shows the results of simulating a plant accident by opening the pulp 24 of the H20 tank 19 in the pump loop of FIG. 4 and instantly introducing H2O into the pipe 12. From this result, it was found that HF gas analysis during transient conditions is also possible in this example. In the above experiment, the detection signal of the analysis beam 30 itself was similar to that shown in FIGS. 5 to 7.

As described above, according to this embodiment, the HF laser 10 and C
In combination with the aFz window 13, HF gas molecules can be efficiently and selectively excited, and the HF gas concentration in the U Fa gas flowing in the pipe can be analyzed online during steady state and transient times.

Next, another embodiment of the present invention will be described using FIG. 13.

This figure is a view seen from the cross-sectional direction of the pipe.

An F center laser oscillator 32 that oscillates in the same wavelength region as the HF laser oscillator 10 is used as the excitation light source. As the probe laser, an Ar laser 33 whose output is stable like the HeNe laser oscillator 11 is used. In addition, the excitation light 2 of the pipe 12, the reference beam 29 and the analysis beam 3
A fluorine-coated plastic window 34, which is hard to break, is used in the zero transmission area. 28A and 28B are concave lens refractive optical elements, and 9A and 9B are position detectors. The reference beam 29 does not necessarily need to be positioned directly upstream of the analysis beam 30 (see Figures 8 and 9) (see Figure 13).
9 and analysis beam 30 are not on the same page). However, of course, in both the previous embodiment and this embodiment, both beams 29 and 30 must be close to each other within a range that satisfies the above conditions. Furthermore, this embodiment differs from the previous embodiment in that an exit from the pipe 12 for the excitation light 2 is not provided.

In this case, the influence of excitation light scattering on the inner wall of the pipe is considered, but in the case of normal pipes, the inner wall is sufficiently rough that the excitation light 2
The influence of the scattered light 35 on the reference beam 29 and the analysis beam 30 can be ignored since it is scattered in the same direction and the spatial density is weakened.

As described above, according to this embodiment, the exit of the excitation light 2 is not provided, and the other excitation light 2, the reference beam 29, and the analysis beam 30 are
By using a fluorine-coated plastic window 34 in the transmission region of the
It has the advantage of being able to analyze HF gas while reducing the risk of an accident involving F a and HF gas leakage. As a modification of this embodiment, the excitation light 2, the reference beam 29, and the analysis beam 30 do not necessarily need to be perpendicular to each other, so these laser beams may be made to enter the inside of the pipe 12 by sharing a fluorine-coated plastic window. mashinhi+m 4
? / blt 1J fi Next, still another embodiment of the present invention will be described using FIG. 15. This embodiment applies Fourier transform spectroscopy, and uses a white infrared light source 35 as an excitation light source. The excitation light 2 from the lens is split by a splitter 36 and becomes interference light 40 according to the optical path difference between a movable mirror 38 driven by a mirror drive motor 37 and a fixed mirror 39, and is focused into the pipe 12 by a lens 4. A knotted thermal lens area 6 is generated. Probe laser
The roles of the reference beam 29 and the analysis beam 30 from the 3D are the same as in the other embodiments shown so far. When the movable mirror 38 finishes moving within the set range, fast Fourier transform is performed inside the data processing circuit 31 to determine the absorption spectrum of the gas flowing inside the pipe 12. If necessary, the above operations can be repeated to accumulate spectra and improve accuracy. 9 is a position detector, and 28 is a refractive optical element having a concave lens.

As described above, according to this embodiment, it is possible to measure infrared absorption spectra, so that Hp gas vents in one pipe can be installed in a UF6 gas handling plant. It has the advantage that other impurity gases can be analyzed simultaneously.

Next, still another embodiment of the present invention will be described using FIG. 16. In this embodiment, a reference beam 29 and an analysis beam 30
A feature is that a fluorine-coated prism 41 is provided in the transmission area of the pipe 12 on the position detector 9 side. Therefore, there is no need to separately provide a refractive optical element as in other embodiments. Note that a concave lens may be used instead of the prism.

Although omitted in FIG. 16, the configurations of the excitation light source, chopper, etc. are the same as in the other embodiments.

As described above, according to this embodiment, by providing the transmission region of the pipe 12 with a refraction function, the displacement of the reference beam 29 and the analysis beam 30 can be enlarged without separately providing a refraction optical element. [It has the advantage of being able to measure and analyze HF gas in U F s gas plant piping.

As an embodiment similar to this embodiment, the configuration shown in FIG. 17 is also possible. That is, by using a seven element coated beam splitter 42 whose surface in contact with the mixed gas 16 is coated with fluorine to provide corrosion resistance, similarly to the fluorine coated prism 41, the probe laser light 8 can be
This has the advantage that there is no need to separately provide a transmission window and a beam splitter. In addition, in Fig. 17, the 16th
As in the figure, structures such as the excitation light source and chopper are omitted. The beam splitter 42 is not limited to the prism having the structure shown in FIG. 17.

Next, still another embodiment of the present invention will be explained with reference to FIG. The feature of this embodiment is that, unlike the other embodiments shown so far, a chopper is not used. That is, excitation light 2
Since the zero intensity is irradiated into the pipe 12 without being periodically modulated, the thermal lens region 6 is constantly present and the analysis beam 30 is therefore not periodically refracted.

In principle, thermal lens refraction spectroscopy for gases does not require periodic excitation, unlike photoacoustic spectroscopy.

This is because in the case of a gas, the excited molecules are replaced one after another, so even if the excitation light 2 is constantly irradiated, the thermal lens effect does not change. However, since the amount of refraction of the analysis beam 30 due to the thermal lens effect is small, the measurement accuracy is poor as a steady displacement, so thermal lens regions are generated periodically and conventionally measured as changes depending on the presence or absence of the thermal lens effect. There is. However, if the detection means is limited to detecting changes in HF concentration during a transient period as shown in FIG. 12, steady excitation is also effective.

As described above, according to this embodiment, the HF gas concentration in the UFa gas handling plant piping can be controlled without using a chopper for the excitation light 2 and without providing a lock-in mechanism in the data processing circuit 31. Detects transient changes,
It is possible to provide an HF gas analyzer that can be used to detect plant abnormalities.

Next, still another embodiment of the present invention will be described with reference to FIG. This embodiment is characterized in that Perot 43 is provided on the upstream and downstream sides of the pipe 12.

By providing the above-mentioned Perot 43, it is possible to reduce vibrations caused by plant operation in the portion of the piping 12 related to analysis, and prevent the vibrations from affecting the analysis. An excitation light source, a probe laser, a chopper, a probe light receiver, etc. can be arranged on an electrically shielded stand, or can be integrally connected to the piping 12 to eliminate the influence of vibration. In addition, in Fig. 19,
The specific shape of the fluorine coated beam splitter 42 is omitted. Further, the reference beam 29 is not on the same plane as the excitation light 2 and does not pass through the thermal lens region 6, similar to FIGS. 13 to 15.18.

As described above, according to this embodiment, there is an advantage that the vibration of the plant piping 12 can be reduced by using the Perot 43, and the HF gas in the piping can be analyzed while eliminating the influence of vibration.

〔Effect of the invention〕

According to the present invention, a globe laser beam is separated into an analysis beam and a reference beam, which pass inside and outside a thermal lens region, respectively, and the displacement of these beams is magnified using a refractive optical element. Since the displacement of the analysis beam and reference beam due to fluctuations in the gas flow in the piping can be effectively offset, the concentration of HP-rich soot in the UFs gas flowing in the piping of a UF6 gas handling plant is steady and
We can provide 1 (F gas analyzer) that can analyze transient values.

In the present invention, as long as there is a transmission window for excitation light and probe laser light, HF analysis can be performed at any location in the plant piping.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the principle of thermal lens refraction spectroscopy, Figures 2 and 3 are schematic diagrams of the basic experimental equipment for thermal lens refraction spectroscopy,
Fig. 4 is a schematic diagram of the gas loop configuration of the above experiment, Figs. 5 to 7 are the results of the above experiment, Figs. 8 and 9 are diagrams showing the structure of an embodiment of the present invention, and Figs. , 9, Figure 13 shows the configuration of another embodiment, Figure 14 shows a modification thereof, and Figures 15 and 16 each show the configuration of another embodiment. In the figure, Figure 17 is the 16th
Modifications of the embodiment shown in the figure, FIGS. 18 and 19, are diagrams showing the configuration of still other embodiments, respectively. DESCRIPTION OF SYMBOLS 1... Excitation light source, 2... Excitation light, 6... Thermal lens area, 7... Probe laser-18... Probe laser light, 9.9A, 9B... Position detector, 10...
・HF laser, 12...Piping, 13...CHF2
Window, 14... Junction type light receiver, 16... Mixed gas of U Fa gas and HF gas, 24... Beam splitter, 27, 27A. 27B...Fluorine coated glass window, 28°28
A, 28B... Concave lens, 29... Reference beam, 3
0... Analysis beam, 31... Data processing device, 32
...F center laser, 34...Fluorine coating plastic window, 41...Fluorine coating prism, 42...Fluorine coating beam splitter-143...Bello. ¥l 1 mouth broom 2 figure 3 day 4 picture temple 5 figure ¥-, w Defense B is rl → foil 8 Mi Mori B'mo 10 figure thousand 1 'l figure no 13 sword too 14 figure I5 15 too 1G Figure also 11 (2) Bamboo shoots 13 Mouth

Claims (1)

[Claims] 1. A means for irradiating a hydrogen fluoride laser into a pipe through which uranium hexafluoride gas containing hydrogen fluoride flows, a means for generating a probe laser, and heat generated in the pipe by the irradiation with the hydrogen fluoride laser. a first optical means for guiding the probe laser to pass through a lens region; a second optical means for guiding the probe laser to pass through a region in the piping other than the thermal lens region; a probe laser that has passed through the thermal lens region; and means for measuring the concentration of hydrogen fluoride based on the probe laser that has been guided by the second optical means and has passed through a region other than the thermal lens region. Hydrogen fluoride analyzer.