JPS63159736A - Concentration measuring method for uranium or plutonium - Google Patents

Abstract

PURPOSE:To securely correct the drift of a measured value due to the damage of an optical system and to measure concentration with high accuracy by providing an interference filter, an optical fiber for light projection, a fiber for photodetection, etc. CONSTITUTION:A sector 7 to which the interference filter is fitted is rotated by a motor 8 to send light beams with respective wavelengths alternately. Then their interference light is sent by an optical system such as a reflecting mirror 9, etc., to the projection-side optical fiber 10. Then, light which is absorbed and attenuated by uranium or plutonium is photodetected by a sensor and then sent to a light emission and reception part through the photodetection-side fiber 11. Here, light which is converged 12 is photodetected 13 and amplified 14, and a gain controller 15 adjusts the light so that reference light intensity is equal. Then, a sample holder 16 identifies from a sample number recognized with the rotation period signal of the sector 7 and the result is outputted 17 as a concentration signal. Thus, the drift of the measured value due to the damage of the optical system is corrected and high-accuracy measurement is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring the concentration of uranium or plutonium in a nuclear fuel reprocessing facility.

[Conventional technology]

Insertion type densitometers, which measure concentration using the light absorption properties of uranium or plutonium, consist of a light source, an interference filter that selects a specific wavelength, an optical fiber that transmits light of the selected wavelength, a cover glass in contact with the liquid, and a light that passes through the liquid. It consists of an optical fiber that transmits the reflected light, and a light receiving element that converts the intensity of the reflected light into an electrical signal.The concentration is determined by measuring the absorbance of uranium or plutonium.

[Problem that the invention seeks to solve]

However, in concentration analyzers that utilize light absorption, contact between the sample liquid and the optical system consisting of a liquid-contacted cover glass and a reflecting mirror is unavoidable, resulting in the disadvantage that measured values may drift due to contamination or damage to the optical system. In particular, when used in a nuclear fuel reprocessing facility, the optical system is exposed to high radiation, resulting in significant damage, and therefore, a technique for calibrating the drift of measured values due to damage is important.

The present invention eliminates the drawbacks of the conventional method for measuring the concentration of uranium or plutonium using an optical system, reliably calibrates the drift of measured values due to damage to the optical system, and enables highly accurate concentration measurement of uranium or plutonium. This paper attempts to provide a method for measuring concentration.

[Means for solving problems]

The present invention is a facility that reprocesses spent nuclear fuel, and uses a light source to measure the concentration of a liquid containing uranium or plutonium by utilizing the light absorbing properties of the substance, an interference filter that selects a specific wavelength, and a light source with a selected wavelength that is transmitted. An insertion-type concentration of uranium or plutonium consisting of an optical fiber that transmits the light, a cover glass that comes into contact with the liquid, a mirror that reflects the light that passes through the liquid, an optical fiber that transmits the reflected light, and a photodetector that converts the intensity of the reflected light into an electrical signal. This is a method for measuring the concentration of uranium or plutonium, which uses the absorption intensity of light at an absorption wavelength of uranium or plutonium and the absorption intensity of light at a non-absorption wavelength of uranium or plutonium.

[Function] While researching damage to optical systems, the present inventors discovered that tetravalent uranium, hexavalent uranium, trivalent plutonium, tetravalent plutonium, and hexavalent plutonium in the visible region. A detailed observation of the absorption spectrum revealed that
It was confirmed that at a wavelength of 700 um, the absorption coefficients of uranium and plutonium are extremely small and are almost unaffected by concentration. Therefore, as a result of measuring the absorbance of uranium or plutonium using this light with a wavelength of 700 nm as a reference light, it was possible to significantly reduce the drift in measured values due to contamination and damage to the optical system.

〔Example〕

FIG. 1 shows an overall view of an insertion type spectrophotometer according to an embodiment of the present invention. This meter consists of a light emitting/receiving section 1, a light guide section 2, and a sensor 3. Figure 2 shows details of the light emitting/light receiving section.

The light emitting unit is equipped with a power supply device 4, a lamp 5 (a tungsten halide light source or the like is used since the absorption wavelength is in the visible light range in the case of uranium or plutonium), a condensing lens 6, and an interference filter that can select a specific wavelength. Sector 7 is strange. The interference filter uses the following wavelengths depending on the valence of uranium and plutonium.

σ(IV)...650nm U (M)・ψ・420nm Pu　(n[)　　　・-Fist　s　6o　n.

pu(■)---470nm Pu(■)@11852nm Also, a 700 nm interference filter for reference light is used. The sectors to which these interference filters are attached are rotated by a motor 8, and transmit each wavelength alternately.

Each of the interference lights is sent to a projection optical fiber 10 by an optical system such as a reflection mirror 9.

Next, the light absorbed and attenuated by uranium or plutonium is received by the sensor 3 and then sent to the light emitting/light receiving section 1 by the light receiving fiber 11. Here, the condenser lens 12
The light collected is received by a light receiving element made of silicon 13 or the like, and after being amplified by a main amplifier 14, it is adjusted by an automatic gain control (Go) 15 so that the above-mentioned reference light intensity becomes the same. That is, the absorption intensity of uranium or plutonium is converted into a value of the ratio of the reference light intensity.

Then sector 7 at sample hold (8/H) 16
After identification by the sample number recognized by the rotation period signal, the output total 17 outputs it as a concentration signal.

FIG. 3 shows an example of measurement of tetravalent uranium obtained in this example. The measurement wavelength was 520 nm.

The reference light wavelength is 700 nm, and the uranium concentration of the test liquid is 120.
f uranium/l. From Figure S, even though the absorption luminous intensity at 520 nm decreases with time,
It can be seen that the ratio between the absorption intensity and the reference light intensity shows a stable value.

[Effects of the Invention] By adopting the above configuration, the present invention uses light with a wavelength of 700 nm as a reference light, measures the absorption intensity of uranium or plutonium as a ratio value of the reference light intensity, and By determining the concentration of plutonium, it has become possible to perform stable measurements with significantly less drift in measured values due to contamination or damage to the optical system.

[Brief explanation of the drawing]

FIG. 1 is an overall view of one embodiment of the present invention, FIG. 2 is a detailed view of the light emitting/light receiving portion of FIG. 1, and FIG. 3 is a graph showing the absorption luminous intensity of the embodiment. Sub-Agents 1) Meifuku Agent Ryo Hagiwara − Sub-Agent Atsuo Anzai

Claims (1)

[Claims] A facility that reprocesses spent nuclear fuel uses a light source to measure the concentration of a liquid containing uranium or plutonium by using the light absorbing properties of the substance, an interference filter that selects a specific wavelength, and an optical fiber that transmits light of the selected wavelength. , a uranium or plutonium insertion type densitometer consisting of a liquid-contacted cover glass, a mirror that reflects light transmitted through the liquid, an optical fiber that transmits the reflected light, and a photodetector that converts the intensity of the reflected light into an electrical signal. Alternatively, a method for measuring the concentration of uranium or plutonium, characterized by using the absorption intensity of light at an absorption wavelength of plutonium and the absorption intensity of light at a non-absorption wavelength of uranium or plutonium.