JP2007147397A - Method for operating reactor, and instrument and method for surveying the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a survey instrument for a reactor which detects the hydrogen concentration in a member of an object to be surveyed, such as a fuel assembly in a nondestructive manner to analyze and evaluate it, without mechanically or physically damaging the member. <P>SOLUTION: This survey instrument has the object to be surveyed, such as an irradiated fuel assembly 11 that is installed erect in the reactor water of the reactor or in the water of a fuel pool 21, a cylindrical closed vessel 22 installed facing the object, a laser apparatus 23 which outputs a pulse laser beam (a), an irradiation optical system 24 which condenses the beam (a), by passing it through the inside of the vessel 22 and irradiates the surface of the member of the object with the beam (a), a fluorescence condensing optical system 25 which guides fluorescence (b) emitted from the atoms and ions of the plasma generated on the surface of the member of the object by irradiation with the beam (a) and makes the fluorescence (b) condense, a spectral means 26 which outputs the light intensity detection signal for each wavelength of the fluorescence (b) and a computer 27, into which the fluorescent wavelength and a light intensity signal for each wavelength are input to calculate sorts and concentrations of elements and analyze them through laser plasma spectroscopy. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a nuclear reactor and an operation method thereof, a nuclear reactor inspection apparatus, and an inspection method thereof that increase an average fuel burnup and improve a fuel economy of a nuclear reactor.

  Boiling water reactor (hereinafter referred to as BWR), pressurized water reactor (hereinafter referred to as PWR), reduced speed light water reactor (hereinafter referred to as PMWR), supercritical pressure light water cooled fast breeder reactor (hereinafter referred to as SCFBR). ) Etc., water is used as a coolant. A zircaloy material that is an alloy of zirconium is generally used for the fuel assembly member of this nuclear reactor.

  Zircaloy has excellent properties as a material for a fuel assembly with low neutron absorption loss. However, when the fuel assembly is placed in high-temperature and high-pressure water, it easily absorbs hydrogen and accumulates in the zircaloy material. When the concentration of hydrogen accumulated in the Zircaloy material having properties exceeds the solid solution limit, it precipitates as hydride, and when the hydride is organized together, mechanical and physical strength decreases, so-called hydrogen It is known that a phenomenon called embrittlement appears.

  In a commercially operated boiling water reactor (BWR) or pressurized water reactor (PWR), the fuel assembly is loaded into the core of the reactor and used for power generation in a short period. The fuel assembly loaded into the reactor core and used for power generation is then taken out of the reactor and its removal burnup, which is the cumulative calorific value until it is replaced with a new fuel assembly, is small. The hydrogen embrittlement phenomenon of the body member cannot occur. In these nuclear reactors, the duration of combustion of the fuel assemblies and the magnitude of the burnup rate are determined mainly by the upper limit of the enrichment of uranium 235 that generates energy by fission in the fuel assemblies.

  However, in the reduced speed light water reactor (PMWR) and supercritical pressure light water cooled fast breeder reactor (SCFBR), which are being studied as future types of nuclear reactors, they are several times the burn-up burn-up in boiling water reactors and pressurized water reactors. The target is a high burn-up burnup with the goal of realizing a high burn-up burnup time, and the fuel assembly is loaded into the reactor core for a longer period of time for power generation. Zircaloy hydrogen embrittlement may become a problem.

  In future reactors, hydrogen concentration gradually increases due to long-term power generation, and there is a possibility that hydrogen embrittlement will proceed at such a high concentration that the members of the fuel assembly exceed the solid solution limit. If the phenomenon of hydrogen concentration exceeding the solid solution limit becomes prominent, the integrity of the fuel assembly may not be guaranteed, and hydrogen embrittlement is a power generation that can generate electricity using a single fuel. It may be one of the factors that limit the amount of electric power, that is, fuel economy.

  In future-type nuclear reactors that are being developed for ultra-high burnup, the limit on uranium enrichment in the fuel should be relaxed to achieve ultra-high burnup, which is an important factor for fuel assembly health. This is due to hydrogen embrittlement of the fuel assembly member and an increase in the internal pressure of the fuel cladding.

  In future-type nuclear reactors such as low-speed light water reactor (PMWR) and supercritical pressure light water-cooled fast breeder reactor (SCFBR), even if the fuel has been used for a predetermined period in the reactor, It is thought that there are many cases where the reactor is reloaded and used for further power generation if it is inspected from the viewpoint of the health of the body and found that there is no problem from the viewpoint of hydrogen embrittlement and internal pressure of fuel.

  Among the two factors related to the fuel integrity of the fuel assembly, the increase in the internal pressure of the fuel cladding tube is related to the release of fission products. As a technique for evaluating the internal pressure of this fuel, a technique for evaluating the fission product (FP) gas release rate by measuring the radioisotope Kr-85 in the plenum portion of the fuel assembly has already been used as a non-destructive analysis technique for fuel. Established.

In addition, as a conventional method for analyzing the hydrogen concentration of the members of the fuel assembly, after the used fuel is cooled in the fuel pool for a certain period of time, the fuel assembly is disassembled, the member is cut into sample pieces, and the high temperature furnace Patent Documents 1 to 3 disclose a method of detecting hydrogen dissolved out by a gas analyzer or a mass analyzer.
JP-A-6-289181 Japanese Patent Laid-Open No. 10-185843 JP 2002-181795 A

  In the conventional hydrogen concentration analysis technology for the members of the fuel assembly, it is clear that there is no problem from the viewpoint of hydrogen embrittlement after analyzing the hydrogen concentration of the member. Because the body parts were cut into sample pieces, they could not be reassembled and returned to the reactor.

  The present invention has been made in consideration of the above-described circumstances, and can analyze the hydrogen concentration of a member in a non-destructive manner without causing mechanical and physical damage to a member of an inspection target such as a fuel assembly. An object of the present invention is to provide a nuclear reactor and a method for operating the nuclear reactor, an inspection apparatus for the nuclear reactor, and an inspection method therefor.

  Another object of the present invention is to ensure the integrity of the fuel by enabling hydrogen embrittlement and internal pressure management of the fuel without performing destructive analysis such as melting and cutting of the irradiated fuel assembly member, It is an object of the present invention to provide a nuclear reactor that can easily realize a high burnup reactor core and improve fuel economy, and an operating method thereof.

  Another object of the present invention is to easily and accurately detect a change in the hydrogen content of the surface of a member such as a fuel cladding tube or a spacer that is likely to be hydrogen embrittled in an inspection object such as an irradiated fuel assembly. It is in providing the inspection apparatus of a nuclear reactor, and its inspection method.

  In order to solve the above-described problems, a nuclear reactor according to the present invention is formed in a core unit composed of a set of four fuel assemblies loaded in a nuclear reactor core, and in the central portion of the core unit. A cross-shaped cross-shaped control rod provided in the space so as to be movable up and down in the longitudinal direction. The core unit is subjected to a hydrogen concentration analysis and continues to be a fuel assembly determined to be free from hydrogen embrittlement. Thus, the reactor core is composed of a large number of core units.

  Further, in order to solve the above-described problems, the reactor operating method according to the present invention is configured by loading a set of four fuel assemblies into the core of the reactor to form a core unit, and the center of the core unit. A control rod having a cross-shaped cross section is housed in a cross-shaped space formed in the section so as to be movable up and down in the longitudinal direction, while a large number of core units are arranged in a substantially circular arrangement in plan view with the core unit as a basic unit. The operation method is characterized in that a fuel assembly that has been analyzed for hydrogen and has no fear of hydrogen embrittlement is continuously used in the core unit, and the output of the reactor core is controlled by moving the control rod up and down. .

  Furthermore, in order to solve the above-described problems, the reactor inspection apparatus according to the present invention is an inspection target for irradiated fuel assemblies and the like installed in a standing state in the reactor water of the reactor or the water of the fuel pool. An object, a cylindrical sealed container placed opposite to the inspection object, a laser device for outputting pulsed laser light, and the pulsed laser light output from the laser device through the cylindrical sealed container Irradiating optical system for condensing and irradiating the object surface of the object, and fluorescence condensing for guiding and condensing the fluorescence emitted from the atoms and ions of the plasma generated on the surface of the object to be inspected by the irradiation of the pulse laser beam An optical system, a spectroscopic unit that makes the guided fluorescence enter the fluorescent light collecting system, divides the light into each wavelength and outputs a light intensity detection signal for each wavelength, and the fluorescence wavelength from the spectroscopic unit and the light intensity for each wavelength. Trust The type and density of the input to element by calculating the is characterized in that it has a calculation means for analyzing the laser plasma spectroscopy.

  Still further, in order to solve the above-described problems, the nuclear reactor inspection method according to the present invention accommodates a plurality of fuel rods in a channel box, and a plurality of fuels arranged so that a coolant passes through the inside. In an inspection method for a nuclear reactor having an assembly and a control rod arranged to be movable in a longitudinal direction in a space in the fuel assembly, and analyzing a hydrogen concentration of a member of an inspection object such as the fuel assembly In the inspection method, the hydrogen concentration of the member to be inspected is analyzed nondestructively by laser plasma spectroscopy at the time of periodic inspection of the nuclear reactor.

  According to the present invention, in a nuclear reactor aiming at realization of an ultra-high burnup such as a reduced-speed light water reactor or a supercritical light water-cooled breeder reactor, a member of an inspection object such as a fuel assembly is cut or melted during a periodic inspection. Therefore, it is possible to analyze the soundness of the fuel assembly of the inspection object and the hydrogen concentration in a non-destructive manner without causing physical or mechanical damage to the member of the inspection object.

  As a result of analyzing the hydrogen concentration of the member of the fuel assembly, if it is found that the hydrogen concentration of the member is lower than a predetermined hydrogen concentration which is a criterion for determining the hydrogen embrittlement state, the method described in the prior art is used. Since it can be evaluated that there is no problem with the increase in internal pressure, the integrity of the fuel assembly can be guaranteed, and it can be continuously used to extend the loading period of the fuel assembly to the reactor or to remove the irradiated fuel assembly. The burnup can be greatly increased, and the fuel economy of the reactor may be significantly improved compared to the conventional one.

  DESCRIPTION OF EMBODIMENTS An embodiment of a nuclear reactor, an operating method thereof, a nuclear reactor inspection apparatus, and an inspection method thereof according to the present invention will be described with reference to the accompanying drawings.

  A nuclear reactor according to the present invention is a reduced speed light water reactor (PMWR) of a type in which a plurality of fuel assemblies are loaded on a reactor core, water is used as a coolant, and this water flows as a coolant between fuel assemblies. And a supercritical pressure light water cooled fast environmental reactor (SCFBR). In this nuclear reactor, a set of four fuel assemblies is loaded on the core of a large number of nuclear reactors, and a flat core structure is formed. A cross-shaped cross-shaped control rod reciprocates in a space surrounded by one set of four fuel assemblies.

[First Embodiment]
FIG. 1 is a perspective view showing a fuel assembly 11 loaded in a reactor core 10 according to the present invention.

  A core of a light water reactor or SCFBR as a nuclear reactor 10 is loaded with a set of four fuel assemblies 11 arranged in a grid pattern from two rows and two columns, one set of fuel assemblies 11. A core unit 12 is configured. A cross-shaped cross-shaped control rod 14 reciprocates vertically in the longitudinal direction by a control rod driving means 15 in a cross-shaped space 13 formed at the center of the core unit 12. The fuel assembly 11 contains a large number of fuel rods in a rectangular tube box.

  The control rod drive means 15 has a control rod drive shaft 16 coupled to the upper end (or lower end) of the control rod 14, and the control rod drive shaft 16 forms a space 13 between four fuel assemblies 11. It can be raised and lowered along the longitudinal direction.

  The neutron absorption rate of the control rod 3 of the two-row, two-column, four-body set of fuel assemblies 11 loaded on the reactor core 10 varies depending on the position of the control rod 14 moved up and down by the control rod driving means 15. To do. During the operation of the nuclear reactor, the raising / lowering position of the control rod 14 is always controlled so that the heat generated from the fuel assembly 11 becomes a required heat generation amount.

  The status of the nuclear reactor is the operating state in which it is operating for power generation, the temporary stop state in which the temporary operation is stopped due to unforeseen factors (situations), and the nuclear reactor is stopped for maintenance and inspection. Roughly divided into regular inspection states. The period in which the state of the reactor is in the operating state or the suspended state is referred to as the operating period, and the period in which the reactor is in the periodic inspection state is referred to as the periodic inspection period. The operation of the nuclear reactor is planned so that the operation period and the periodic inspection period are repeated alternately.

  In the nuclear reactor, the fuel assembly 11 used for power generation for a certain period is taken out during this periodic inspection period, transferred to the fuel pool, cooled for a predetermined period, and a new fuel assembly 11 is loaded into the nuclear reactor.

  In the conventional nuclear reactors BWR and PWR, the fuel assembly is unconditionally taken out after a predetermined operation period and replaced with a new fuel assembly. According to the embodiment of the present invention, the inspection is performed. If the hydrogen concentration analysis of the member of the fuel assembly 11 as an object indicates that there is no concern about hydrogen embrittlement and there is no problem in increasing the internal pressure of the fuel, the fuel assembly 11 is used further continuously. It becomes possible. Therefore, by reloading the fuel assembly 11 that can be used continuously to the reactor core 10 or by continuing to use the fuel assembly 11 as it is, the entire fuel assembly 11 can be used for a longer period of time and the burnup can be improved. Can do. In this embodiment, a fuel assembly that can be continuously used is reloaded into the core 10 to operate the nuclear reactor, thereby reducing the amount of fuel used for a predetermined power generation amount and improving fuel economy. Is possible.

  In this nuclear reactor, the fuel integrity can be ensured by the hydrogen embrittlement diagnosis of the fuel assembly 11, and the burnup can be improved while ensuring the fuel integrity.

  FIG. 2 is a plan view showing an arrangement example of the fuel assemblies 11 and the control rods 14 arranged in the core 10 of the nuclear reactor. This reactor core arrangement structure schematically shows an example in which a large number of units, for example, 32 units, are arranged with the arrangement of the fuel assemblies 11 and the control rods 14 in two rows and two columns and one set as basic units. Is. The reactor core 10 shown in FIG. 2 is an example of an arrangement structure close to a circular shape in plan view so that neutrons generated from the fuel can be used efficiently. In this core arrangement configuration example, There will be 4 × 32 = 128 spaces in the core 10 where the fuel assemblies 11 can be placed.

[Second Embodiment]
FIG. 3 is a principle diagram showing an embodiment of a nuclear reactor inspection method for analyzing a hydrogen concentration of a member of a fuel assembly loaded in a nuclear reactor core.

  This embodiment shows the principle of laser plasma spectroscopy for analyzing the hydrogen content of a member constituting a fuel assembly 11 as an inspection object, for example, a zircaloy member such as a fuel cladding tube or a spacer. The surface of the member constituting the body 11 is focused and irradiated with a pulse laser beam a having a required pulse width, for example, about 100 nanoseconds or less, and a thin layer of micron units on the surface of the member is instantaneously heated and evaporated and atomized. Generate tens of thousands of degrees of plasma.

  The plasma atoms and ions in the generated plasma 18 are in a high-energy excited state. The laser beam is a pulsed laser beam, and in the time zone in which the laser pulse width is repeated and the energy of the laser beam a is not irradiated, the atoms and ions in the plasma 18 emit light and lose energy to stabilize the ground state. Return to. The fluorescence b emitted when returning to the low energy state is subjected to wavelength analysis by laser plasma spectroscopy.

  The wavelength of the fluorescence a varies depending on the type of element and energy state. Further, when the number of atoms of the same element existing in the plasma 18 is large, the intensity of fluorescence inherent to the element also increases.

  Accordingly, the surface of the fuel assembly 11 is irradiated with the pulsed laser beam a to generate plasma 18, and the type of atoms in the plasma 18 and the wavelength of fluorescence b emitted from the ions and the intensity of the fluorescence are measured and analyzed. By doing so, the element type and fluorescence intensity can be specified nondestructively from the fluorescence wavelength, and the concentration of the element can be analyzed from the intensity for each wavelength of the fluorescence a.

  In this way, the surface of the member of the fuel assembly 11 is focused and irradiated with pulsed laser light, the constituent energy on the surface of the member is converted into plasma by the laser energy, and the wavelength of the emission spectrum of the fluorescence b emitted from the plasma 18 The material composition of the member of the fuel assembly 11 can be analyzed from the fluorescence intensity for each wavelength. This material composition analysis method is called laser plasma analysis method.

[Third Embodiment]
FIG. 4 shows a first embodiment of a reactor inspection apparatus for analyzing the hydrogen concentration of members of the fuel assembly 11 and an inspection method therefor.

  The reactor inspection apparatus 20 shown in FIG. 4 includes an irradiated fuel assembly 12 installed upright in the reactor or in the water of the fuel pool 21, and the longitudinal direction of the fuel assembly 12. A rectangular cylindrical or cylindrical sealed container 22 that can be moved up and down along with, a laser device 23 that outputs a pulsed laser beam a, and a pulsed laser beam a output from the laser device 23 into the fuel assembly 11. The irradiation optical system 24 for condensing and irradiating the surface of the member, and the surface of the member is instantaneously heated and evaporated and atomized by the irradiation of the pulsed laser light a to form a plasma state of tens of thousands of degrees, and from the generated plasma state atoms and ions A fluorescence condensing optical system 25 that guides the emitted fluorescence b, and the fluorescence b that has been guided through the fluorescence condensing optical system 25 and is divided for each wavelength, and the fluorescence intensity is detected by a built-in optical sensor. Spectroscopic means 2 When, and a computer 27 as an arithmetic means of the light intensity signal for each wavelength and the wavelength of fluorescence measured by the spectral means 26 is input.

  The spectroscopic unit 26 includes a fluorescence spectroscopic unit that distinguishes fluorescence having a wavelength unique to hydrogen from generation of plasma, and a fluorescence detection unit such as an optical sensor that detects a wavelength unique to hydrogen and its wavelength intensity. In the computer 27, the element concentration such as hydrogen and the relative element concentration are calculated from the fluorescence wavelength and the intensity for each wavelength, and the calculation result is displayed on a display means (not shown). The display means may be a display attached to the computer as the calculation means, or may be connected to a remote display via wireless or wired connection and displayed on this display.

  The cylindrical sealed container 22 has a transmission window 30 that transmits the pulse laser light a and the fluorescence b from the laser device 23 at the top, and a total reflection mirror 31 is installed at the bottom of the cylindrical sealed container 22. The pulsed laser light a whose direction is changed by the total reflection mirror 31 and reflected in a right angle direction is condensed by a condensing lens 32 provided on the side of the sealed container 22 to increase the energy density. A member surface of a certain fuel assembly 11 is focused and irradiated. Further, a perforated mirror 34 is obliquely disposed above the cylindrical sealed container 22, and the pulsed laser light a oscillated from the laser device 23 is guided into the cylindrical sealed container 22 from the hole 34 a of the perforated mirror 34. ing.

  The irradiation optical system 24 includes a hole portion of a perforated mirror 34, a transmission window, a total reflection mirror 32, and a condensing lens 33. Pulse laser light a having a pulse width of 100 nanoseconds or less oscillated from the laser device 23 is put into water. The member surface of the irradiated fuel assembly 11 which is the inspection object installed is condensed and irradiated.

  Plasma is generated on the surface of the member by condensing and irradiating the member surface of the fuel assembly 11, and fluorescence b is generated from the measurement target element by the generated plasma. The generated fluorescence is guided to the spectroscope 26 through the fluorescence inspection optical system 25. The fluorescence condensing optical system 25 includes a condensing lens 33, a total reflection mirror 32, a transmission window 31, a perforated mirror 34, and a condensing lens 35.

  Fluorescence from the plasma generated by condensing and irradiating the member surface of the fuel assembly 11 becomes parallel light by the condensing lens 33, is reflected by the total reflection mirror 32, passes through the cylindrical sealed container 22, Most of the light is reflected by the mirror surface of the perforated mirror 34 from the transmission window 31, and the reflected fluorescent light b is collected by the condenser lens 35 and incident on the spectroscopic means 26. The fluorescence intensity for each wavelength is detected. This detection signal is sent to the computer 27 and analyzed by laser plasma spectroscopy, the element type and the relative element concentration are calculated, and the calculation result is displayed on the display means.

  Next, the operation of the nuclear reactor inspection apparatus will be described.

  This nuclear reactor inspection apparatus 20 passes through a hole 34a of a perforated mirror 34 obliquely provided with a pulsed laser beam a oscillated from a laser apparatus 23, and enters an irradiation optical system 24 formed in a cylindrical hermetic container 22. Guided and focused on the member surface of the irradiated fuel assembly 11 of the inspection object to be analyzed by the condenser lens 33 disposed on the lower side surface of the cylindrical sealed container 22.

  Here, the laser beam a output from the laser device 23 is a pulse laser beam having a pulse width of 100 nanoseconds or less, for example, a pulse width of several nanoseconds to 100 nanoseconds. When this pulsed laser beam a is condensed and irradiated on the member surface of the fuel assembly 11, a thin layer of micron units on the member surface is instantaneously heated and evaporated and atomized into a plasma state of several tens of thousands of degrees. Generate.

  The member surface of the fuel assembly 11 is locally (point-like) in a plasma state, and the generated plasma 18 emits fluorescence b from atoms and ions in the plasma state. The fluorescence b is scanned in the opposite direction to the irradiation path (traveling path) of the pulsed laser light a, becomes parallel light by the condenser lens 33, and the traveling direction of the fluorescence b is changed by the total reflection mirror 32, and is sealed in a cylindrical shape. Ascends inside the container 22 and passes through the transmission window 31 on the top surface of the sealed container 22. Most of the light is reflected by the perforated mirror 34, changed in the direction to the horizontal direction, and condensed by the condenser lens 35. 26 is incident.

  In the spectroscopic means 26, the incident fluorescence b is divided for each wavelength, and the fluorescence intensity for each wavelength is measured by an optical sensor built in the spectroscopic means 26. The fluorescence wavelength measured by the spectroscopic means 26 and the light intensity signal for each wavelength are transmitted to the computer 27 as detection signals. In the computer 27, the element type and relative element concentration are calculated from the fluorescence wavelength and the light intensity for each wavelength, and the calculation result is displayed on a display means (not shown).

  Further, the computer 27 can control the emission timing of the laser pulse output from the laser device 23 by periodically sending the trigger signal c to the laser device 23 by the function of the built-in program. Further, the computer 27 matches the timing at which the fluorescence b from the plasma 18 is measured by the spectroscopic means 26 with the fluorescence generation lifetime of the element to be analyzed, here, the hydrogen atom, and the backland emission that is not related to the light emission of the element to be measured (analyzed). By controlling the timing to an optimum condition that is easily distinguishable from the plasma 18, it is possible to accurately and efficiently measure only the fluorescence signal of the measurement target element from the plasma 18.

  Further, the cylindrical airtight container 22 is moved up and down as indicated by an arrow A in the vertical direction in FIG. 4 and is moved in the vertical direction by a lift driving device (not shown), so that the fuel assembly 11 is fixed while the fuel assembly 11 is fixed. Plasma 18 is generated at different locations on the constituent member surface, light emission (fluorescence) from the moving plasma is always incident on the spectroscopic means 26, and information on the fluorescence wavelength and light intensity is calculated and processed by the computer 27. The hydrogen concentration at different locations on the member surface of the fuel assembly 11 can be measured.

  By performing this hydrogen concentration measurement operation for each continuous laser pulse or for each of a plurality of laser pulses, the vertical (longitudinal) distribution of the hydrogen concentration on the member surface of the fuel assembly 11 is measured. can do.

  In the modification of the nuclear reactor inspection apparatus 20 shown in FIG. 4, by moving the cylindrical airtight container 22 in the vertical direction A, the irradiation position of the pulsed laser light a, that is, the plasma generation position is moved in the vertical direction. Although the example of measuring the vertical distribution has been described, a horizontal movement mechanism (horizontal scanning optical system) for moving the cylindrical airtight container 22 in the horizontal direction is provided, and the irradiation position of the pulse laser beam a is moved in the horizontal direction. The horizontal distribution of the hydrogen concentration may be measured. Further, the nuclear reactor inspection apparatus 20 performs two-dimensional distribution measurement of the hydrogen concentration on the member surface of the fuel assembly 11 by combining the irradiation position of the laser beam with two movement directions of the vertical direction and the horizontal direction. You may be able to.

  Further, in this nuclear reactor inspection apparatus 20, as shown in FIG. 5, the pulse width is from several nanoseconds to several tens of nanoseconds, for example, 10 nanoseconds, on the surface of the member constituting the fuel assembly 11 from the laser device 23. It is also possible to collect and irradiate about a pulsed laser beam, and a thin layer in units of microns on the surface of the member of the fuel assembly 11 may be instantaneously heated and evaporated and atomized to generate plasma in a plasma state of tens of thousands of degrees.

  Since the atoms and ions in the plasma state formed on the surface of the member of the fuel assembly 11 are in a high energy state, the pulse laser beam a has no energy during the period of the time zone between the laser pulse widths. In the time zone between the widths, the atoms and ions in the plasma lose light and return to a low energy state (stable energy level) by emitting light (fluorescence).

  At this time, the wavelength of the fluorescence emitted from the atoms constituting the plasma differs depending on the type and energy state of the atoms, and the type and concentration of the constituent elements are analyzed and evaluated by measuring the wavelength and light intensity of the fluorescence. be able to.

  FIG. 6 is an enlarged view of the plasma 18 generated by the irradiation of the pulsed laser beam a and its periphery.

  By irradiation with one pulse of pulse laser light, an extremely thin layer (micron order thin layer) on the member surface 37 of the fuel assembly 11 is heated and evaporated and atomized to generate plasma 18. Since most of the atoms scattered in the space after the member surface 37 is heated and evaporated and atomized do not return to the member surface 37 of the fuel assembly 11, the portion irradiated with the pulse laser beam a is shown in FIG. As shown in Fig. 4, the thickness is reduced slightly.

  The surface layer 38 in which the member material of the fuel assembly 11 has been thinned by irradiation with the pulsed laser beam a is scraped as a thin layer from the member surface 37 for each pulse of the laser beam a. When the pulse irradiation of the laser beam “a” is repeated at the same position, the surface of the portion that is slightly deeper from the member surface 37 is exposed although it is very slight. Therefore, by measuring the wavelength and light intensity of the fluorescence from the plasma 18 for each pulse of the laser light a, the change in the depth direction of the hydrogen concentration can be measured.

[Fourth Embodiment]
FIG. 7 is a diagram showing another embodiment of the nuclear reactor inspection apparatus and the inspection method thereof according to the present invention.

  In describing the nuclear reactor inspection apparatus 20A of this embodiment, the same components as those in the nuclear reactor inspection apparatus 20 shown in FIG. 4 are denoted by the same reference numerals, and description thereof is simplified or omitted.

  The reactor inspection apparatus 20A shown in FIG. 7 is provided with a cylindrical spacing spacer 40 that protrudes outward so as to surround the lower side surface of the cylindrical sealed container 22 near the condenser lens 33. The interval holding spacer 40 is provided with a sealing packing 41 such as a rubber packing so as to face the member surface of the fuel assembly 11 installed underwater and to be in close contact with the member surface. Between the cylindrical sealed container 22 and the member surface of the fuel assembly 11, a vacuum container 43 that covers the condenser lens is configured.

  A discharge (exhaust) pipe 44 is connected to the cylindrical vacuum vessel 43 so that fluid such as water (water vapor) and gas can be discharged, and an exhaust device 45 is provided at the end of the discharge pipe 44.

  The reactor inspection apparatus 20A shown in FIG. 7 activates the laser apparatus 23 to irradiate the pulsed laser light a to perform hydrogen measurement in a nondestructive manner. The fluid such as water (hydrogen, etc.) and gas is discharged, and the space in the vacuum vessel 43 is set in advance so that water vapor and hydrogen are sufficiently reduced.

  After the inside of the cylindrical vacuum vessel 43 is evacuated and set to a negative pressure or a vacuum state so that water vapor and hydrogen are sufficiently reduced, a change in the hydrogen content on the surface of the member of the fuel assembly 11 which is the inspection object The work of measuring is performed.

  Next, the operation of the nuclear reactor inspection apparatus 20A will be described.

  In this nuclear reactor inspection apparatus 20A, after the cylindrical sealed container 22 is disposed facing the member surface of the fuel assembly 11 in a standing state in the water of the fuel pool 21 or the like, the sealed packing 41 of the cylindrical vacuum container 43 is used as the fuel. The assembly 11 is closely attached to the member surface.

  Thereafter, the discharge device 45 is operated to exhaust the water vapor and hydrogen in the cylindrical vacuum vessel 43 through the exhaust pipe 44, and the inside of the vacuum vessel 43 is set to a negative pressure or a vacuum state. In this set state, the distance between the condenser lens 33 and the member surface of the fuel assembly 11 is maintained at a required value.

  After the inside of the cylindrical vacuum vessel 43 is set to a negative pressure or a vacuum state, the laser device 23 is operated to output the pulse laser beam a. The output pulsed laser beam a passes through the transmission window 31 of the cylindrical sealed container 22 from the hole 34a of the perforated mirror 34 provided obliquely, travels through the cylindrical sealed container 22, and obliquely enters the sealed container 22 therein. The direction is changed by the provided total reflection mirror 32, and the condensing lens 33 focuses and irradiates the member surface of the fuel assembly 11 to be analyzed.

  That is, the pulsed laser light a output from the laser device 23 is scanned through the irradiation optical system 24 and focused on the member surface of the fuel assembly 11 to increase the energy density. As the laser light a output from the laser device 23, pulse laser light having a pulse width of 100 nanoseconds or less, preferably from several nanoseconds to several tens of nanoseconds, for example, about 10 nanoseconds is used. When the pulse laser beam oscillated from the laser device 23 is focused and irradiated on the member surface of the fuel assembly 11, the energy density is increased, and a thin layer on the member surface is instantaneously heated and evaporated, atomized, and several It becomes a plasma state of ten thousand degrees.

  On the surface of the member in the plasma state, the fluorescence b is emitted from the generated atoms and ions in the plasma 18 state, and the emitted fluorescence b passes through the fluorescence condensing optical system 25 contrary to the traveling path of the laser light a. move on.

  Fluorescence of atoms and ions generated from the plasma on the member surface of the fuel assembly 11 becomes parallel light by the condensing lens 33, the traveling direction is changed by the total reflection mirror 32, and the inside of the cylindrical sealed container 22 rises. The majority of the fluorescent light b passes through the transmission window 31 on the upper surface of the sealed container 22, is reflected by the perforated mirror 34, travels in the lateral direction, is collected by the condenser lens 35, and enters the spectroscopic means 26.

  In the spectroscopic means 26, the incident fluorescence b is divided for each wavelength, and the light intensity of the fluorescent light for each wavelength is measured by a photosensor built in the spectroscopic means 26. The fluorescence wavelength measured by the spectroscopic means 26 and the detection signal of the light intensity for each wavelength are transmitted to the computer 27. In the computer 27, the element type and relative concentration are calculated from the fluorescence wavelength and the intensity for each wavelength using laser plasma spectroscopy, and the calculation result is displayed on a display means (not shown).

  In addition, the computer 27 sends a trigger signal to the laser device 23 to control the timing of laser pulse emission, and to control the timing at which the fluorescence b from the plasma 18 is measured by the spectroscopic means 26 to an optimum condition. Only the fluorescence signal of each element from the plasma 18 can be measured accurately and accurately.

  In this reactor inspection apparatus 20A, the member surface of the fuel assembly 11 to be irradiated with the laser is surrounded by a cylindrical vacuum vessel 43 at this time, and the residual water vapor and hydrogen are sufficiently small. Hydrogen in the plasma 18 generated by irradiation is heated, evaporated, atomized by the laser beam a together with the constituent elements of the material of the member from the member of the fuel assembly 11, and is turned into plasma. Since the fluorescence from the plasma 18 has a small background fluorescence signal due to hydrogen derived from moisture or the like, the hydrogen concentration in the material can be accurately measured.

[First Modification]
FIG. 8 shows a first modification in another embodiment of the nuclear reactor inspection apparatus of the present invention.

  FIG. 8 shows an enlarged area around the cylindrical vacuum vessel 43 in the reactor inspection apparatus 20A shown in FIG. 7, and the other configuration is not different from the inspection apparatus 20A shown in FIG. The same components are denoted by the same reference numerals and description thereof is omitted.

  In the enlarged view shown in FIG. 8, an exhaust device 45 is connected to the cylindrical vacuum vessel 43 and an inert gas supply device 46 is connected to exhaust and supply air by opening and closing the on-off valves 47, 48 and 49. It can be switched.

  An air supply pipe 50 is connected in the middle of the exhaust pipe 44, and an inert gas supply device 46 is connected to the other end of the air supply pipe 50.

  In the first modification, the laser device 23 is operated to irradiate the laser beam a, and the on-off valves 47 and 48 are opened before the hydrogen measurement is performed, and the on-off valve 49 is closed. The water and gas in the container 43 are discharged (exhaust), and the water vapor and hydrogen in the vacuum container 43 are set to be sufficiently reduced.

  Thereafter, the on-off valve 48 is closed and the on-off valve 49 is opened to introduce an inert gas into the vacuum vessel 43.

  After the inert gas is introduced into the vacuum vessel 43 from the inert gas supply device 46, the on-off valve 49 is closed to stop the supply of the inert gas, and the on-off valve 48 is opened again to make a vacuum in the exhaust device 45. The gas in the container 43 is exhausted. A three-way switching valve may be provided at the connection between the exhaust pipe 44 and the air supply pipe 50, and the on-off valves 48 and 49 may be omitted.

  By repeating the exhaust and supply of air in the vacuum vessel 43 and performing a so-called gas replacement operation, water vapor and hydrogen gas remaining in the vacuum vessel 43 are reduced as much as possible.

  Then, the laser device 23 is operated in a state where water vapor and hydrogen gas are reduced as much as possible in the cylindrical vacuum vessel 43, and the pulse laser beam a is focused on the member surface of the fuel assembly 11, and the fluorescence is measured. Thus, the background fluorescence signal that becomes hydrogen derived from moisture contained in the fluorescence b from the plasma 18 can be further reduced, and the concentration of hydrogen contained in the material of the fuel assembly 11 can be accurately and accurately measured. it can.

  In the nuclear reactor inspection apparatus 20B shown in FIG. 8, after the gas replacement operation, the on-off valve 48 is closed, the on-off valve 49 is opened, and the inert gas is supplied by the inert gas supply apparatus 46 to measure the hydrogen concentration. The inside of the cylindrical vacuum vessel 43 is maintained at atmospheric conditions of 0.5 to 3 atmospheres. It is possible to measure the hydrogen fluorescence signal by the irradiation with the pulsed laser beam a after supplying the inert gas until the pressure reaches the optimum inert gas atmosphere pressure.

  As the inert gas supplied into the cylindrical vacuum vessel 43, for example, easily available and inexpensive He gas or Ar gas is employed. Since the inert gas is supplied into the vacuum vessel 43 every time the gas replacement operation is performed before the hydrogen concentration measurement or during the measurement, the inert gas is easily available, and is inert when the plasma 18 is generated by irradiation with the laser beam a. If the generation of the gas itself is strong, the insoluble background signal becomes stronger than the fluorescence signal of hydrogen, so it is important that the generation of the inert gas itself is weak. From these viewpoints, the hydrogen concentration can be efficiently measured by using He or Ar gas as the kind of inert gas.

[Second Modification]
FIG. 9 shows a second modification of another embodiment of the nuclear reactor inspection apparatus according to the present invention.

  The reactor inspection apparatus 20C shown in the second modification is characterized in that gas is supplied to and discharged from the cylindrical vacuum vessel 43, and the other structure is the same as that of the reactor shown in FIG. Since the configuration is the same as that of the inspection apparatus 20A, the same components are denoted by the same reference numerals, and description thereof is simplified or omitted.

  FIG. 9 is an enlarged view of the periphery of the cylindrical vacuum vessel 43. The exhaust device 45 exhausts water and water vapor from the cylindrical vacuum vessel 43, and the inert gas supplying the inert gas into the vacuum vessel 43. In order to maintain the inert gas atmosphere conditions in the gas supply device 46, the inert gas supply control device 52 that controls the operation of the gas supply device 46 and the on-off valves 47, 48, and 49, and the vacuum vessel 43, a vacuum is provided. A gas pressure gauge 53 for measuring the gas pressure in the container 43.

  In the reactor inspection apparatus 20C shown in FIG. 9, a cylindrical interval holding spacer 40 is disposed so as to cover a portion where the condensing lens 33 on the lower side of the cylindrical sealed container 22 is set from the outside. A sealing packing 41 such as a rubber packing is attached to the tip of the interval holding spacer 40. A sealing packing 41 attached to the tip of the interval holding spacer 40 is attached to the surface of the member of the fuel assembly 11 to form a cylindrical vacuum container 43.

  An exhaust pipe 44 for discharging water and gas is connected to the cylindrical vacuum vessel 43. The exhaust pipe 44 is provided with a gas pressure gauge 53 and on-off valves 47 and 48, and an exhaust device 45 is provided at the tip thereof. Connected.

  The exhaust pipe 44 is connected to a gas supply pipe 50 between the on-off valves 47 and 48, and the gas supply pipe 50 is also provided with an on-off valve 49 and connected to the inert gas supply device 46.

  The inert gas supply device 46 and the on-off valves 47, 48, and 49 are controlled by an inert gas supply control device 52, and a gas replacement control mechanism 54 that controls the exhaust of the gas in the vacuum vessel 43 and the supply of the inert gas. Is configured. On the other hand, the pressure detection signal from the gas pressure gauge 53 is input to the inert gas supply control device 52.

  In the nuclear reactor inspection apparatus 20C shown in FIG. 9, a cylindrical sealed container 22 is installed opposite to the fuel assembly 11, a cylindrical vacuum container 43 is mounted on the surface of the fuel assembly 11, and the vacuum container 43 is set in a sealed state. Before the hydrogen measurement is performed by condensing and irradiating the member surface of the fuel assembly 11 with the laser light a oscillated from the laser device 23 through the irradiation optical system 24 in this set state, the on-off valves 47 and 48 are opened, The exhaust device 45 is operated with the on-off valve 49 closed to exhaust water and gas in the cylindrical vacuum vessel 43 so that water vapor and hydrogen in the vacuum vessel 43 are sufficiently reduced.

  After evacuating the exhaust device 45 to exhaust water and gas, the on-off valve 48 is closed and the on-off valve 49 is opened to supply an inert gas into the cylindrical vacuum vessel 43.

  After the inert gas is introduced into the cylindrical vacuum vessel 43, the on-off valve 49 is closed to stop the supply of the inert gas, the on-off valve 48 is opened again, and the exhaust device 45 is used to open the inside of the vacuum vessel 43. Exhaust the gas. The supply / discharge operation to / from the vacuum container 43 is controlled by the inert gas supply control device 52, and the supply / discharge of gas to / from the vacuum container 43 is repeated.

  When the exhaust operation of the gas from the vacuum vessel 43 is completed, the on-off valve 48 is closed, the on-off valve 49 is opened, and an inert gas is supplied into the cylindrical vacuum vessel 43. From the viewpoint of maintaining the atmospheric conditions of the vacuum vessel 43 during the measurement of the hydrogen concentration, the inert gas is supplied so that the inert gas is supplied in accordance with the gas pressure detection signal of the gas pressure gauge 53 until the optimum inert gas atmospheric pressure is reached. Control is performed by the control device 52.

  The supply control of the inert gas pressure in the vacuum vessel 43 is not performed from the inside of the vacuum vessel 43 due to a change in the gas pressure gauge 53 even during the measurement of the hydrogen fluorescence signal by the focused irradiation of the laser beam a. By detecting leakage of active gas or changes in atmospheric pressure due to water vapor intrusion, the on-off valves 47 and 49 are opened to control supply of additional inert gas.

  By the additional supply control of the inert gas, the analysis target position and state of the member surface are changed by maintaining the member surface of the fuel assembly 11, that is, the atmosphere in the vicinity of the measurement surface, in an atmosphere condition suitable for hydrogen concentration analysis. However, the hydrogen concentration in the member of the fuel assembly 11 can always be measured with high accuracy.

  In the reactor inspection apparatus shown in FIGS. 3 to 9, the example in which the emission of the fluorescence b from the hydrogen atom is measured by laser plasma spectroscopy and the hydrogen concentration analysis is performed is shown. However, the embodiment shown in FIG. Then, in addition to the hydrogen concentration analysis, the fluorescence from one or more elements among zirconium, iron, chromium, which are constituent elements of the members of the fuel assembly 11 as the inspection object, and oxygen present in the atmosphere and water. The wavelength of b and its light intensity can be measured. For example, an analysis result corresponding to the relative concentration of hydrogen and zirconium can be obtained by calculating and evaluating the ratio of the light intensity signal of the fluorescence b having the intrinsic wavelength of hydrogen atoms and the light intensity signal of the fluorescence b having the intrinsic wavelength of zirconium atoms. it can.

  If the hydrogen concentration is calculated and evaluated only from the intensity of the fluorescence b of the intrinsic wavelength of the hydrogen atom, the degree of absorption of the laser beam a varies depending on the state of the member surface of the fuel assembly 11 to be analyzed, for example, the state of impurity adhesion. Even if the laser pulse of energy is irradiated, the intensity of the fluorescence b having the intrinsic wavelength of hydrogen atoms from the plasma 18 will fluctuate. Even if the fluorescence intensity fluctuates, the intensity of the fluorescence b at the intrinsic wavelength of the zirconium atom varies in the same way as the hydrogen atom, so the analysis can be performed by using the ratio of the fluorescence intensity peculiar to the two atoms. Even when the surface state of the object is different, the hydrogen concentration can be accurately calculated and evaluated.

  Thus, in order to ensure a sufficient hydrogen concentration, the type of element that takes a ratio to the signal of the fluorescence b at the natural wavelength of the hydrogen atom, the hydrogen concentration is more than the hydrogen concentration among the constituent elements of the material to be analyzed. It is desirable to select elements that are present in high concentrations.

  FIG. 10 shows the fluorescence emitted from the plasma 18 generated by the pulse of the laser beam a, with the horizontal axis representing the fluorescence wavelength and the vertical axis schematically representing the fluorescence intensity at that wavelength. The signal of the peak height or peak area of the fluorescence signal peak P of hydrogen corresponds to the hydrogen concentration, but only this can analyze the hydrogen concentration. For example, by scanning the spectral wavelength of the spectral means 26 in FIG. 7, the fluorescence signal intensities for the wavelengths P, R, and S as shown in FIG. 10 are obtained.

  Thus, by evaluating the zirconium concentration from the fluorescence signal intensity at the wavelength of the zirconium fluorescence signal, that is, the peak height or area of the zirconium fluorescence peak R, and calculating the two ratios, the member of the fuel assembly 11 is obtained. The composition of the two components in it can be analyzed.

  Furthermore, when the peak of different fluorescence wavelength, the fluorescence peak S of the element X, and the element X are, for example, oxygen, the relative concentration of the member of the fuel assembly 11 with oxygen can be calculated and evaluated. The same applies when iron or chromium is selected as the element X. Further, when two kinds of zirconium and oxygen are simultaneously measured as the element X, the ratio of zirconium and oxygen, that is, the oxidation state can be analyzed.

  FIG. 11 is a flowchart showing an example of a procedure for inspecting the hydrogen concentration and replacing the fuel assembly 11 with a new fuel during the periodic inspection of the reactor.

  In the nuclear reactor inspection method and operation method shown in FIG. 11, the flow of the procedure for the hydrogen concentration inspection of the members of the fuel assembly 11 during the periodic inspection and the replacement of the fuel assembly to the new fuel assembly as a result is performed. It is shown.

  In the nuclear reactor inspection method and operation method shown in FIG. 12, the procedure for the hydrogen concentration inspection of the members of the fuel assembly 11 during the periodic inspection and the replacement of the fuel assembly with a new fuel assembly based on the inspection result. This flow is shown.

  In the embodiment of the present invention, in order to easily detect a change in the hydrogen content of the surface of a member of the fuel assembly 11 such as a fuel cladding tube or a spacer made of zircaloy which is easily hydrogen embrittled in the irradiated fuel assembly. A new inspection method and inspection apparatus thereof have been described.

  In this nuclear reactor inspection apparatus and inspection method, a laser beam focused on a member material surface of a fuel assembly 11 that is an object to be inspected by laser plasma spectroscopy is used to irradiate constituent atoms on the material surface by the laser energy. The composition of the member material is analyzed from the information of the wavelength of the emission spectrum (fluorescence b) from the plasma 18 and the light intensity for each wavelength.

  In this nuclear reactor inspection apparatus and inspection method, laser plasma spectroscopy is applied to constituent materials of irradiated fuel assemblies installed in the reactor water or in the spent fuel pool 21, such as fuel cladding tubes and spacers made of Zircaloy. It is applied to the analysis of the hydrogen content of the site.

  When this laser-induced plasma spectroscopy is used, it is not necessary to perform destructive analysis such as melting and cutting of the constituent material of the fuel assembly as in the prior art, and the constituent members of the fuel assembly 11 on the spot (on-site) Analysis can be performed without any mechanical or physical damage. Therefore, the hydrogen concentration in Zircaloy can be measured and inspected for inspection objects placed in the reactor or in the fuel pool 21 at the time of periodic inspection or when used, etc., in a non-destructive manner. The hydrogen embrittlement situation can be diagnosed.

  Therefore, hydrogen embrittlement and the control of the internal pressure of the fuel cladding tube, which are important in ensuring the soundness of the fuel, become possible, making it easy to achieve a high burnup in the fuel assembly and improving the fuel economy. The operation of the nuclear reactors made can be realized.

The perspective view which shows the structure of the core unit which consists of 1 set of 4 bodies loaded in the core of the reactor which concerns on this invention, and a fuel assembly of 2 rows 2 columns. The top view which shows one Embodiment of the nuclear reactor which concerns on this invention, and shows typically arrangement | positioning of the fuel assembly arrange | positioned at a nuclear reactor core. The principle figure explaining the inspection principle which analyzes the hydrogen concentration of inspection objects, such as a fuel assembly loaded into a nuclear reactor core. BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows typically embodiment of the inspection apparatus and the inspection method of the reactor which concern on this invention. The figure which shows the pulse laser beam irradiation area | region to the test object with which the inspection apparatus of the reactor which concerns on this invention is equipped. The figure which expands and shows the irradiation area | region of the pulse laser beam shown by FIG. The block diagram which shows typically other embodiment of the inspection apparatus of the reactor which concerns on this invention, and its inspection method. The figure which shows partially the 1st modification in other embodiment of the inspection apparatus of the reactor shown by FIG. The figure which shows partially the 2nd modification in other embodiment of the inspection apparatus of the reactor shown by FIG. The figure which shows the relationship between the wavelength of the fluorescence light-emitted from the plasma produced | generated by irradiation of the pulse laser beam, and fluorescence intensity. The flowchart which shows the procedure of the hydrogen concentration test | inspection in the case of the periodic inspection of a nuclear reactor, and replacement | exchange to a new fuel assembly. The flowchart which shows the hydrogen concentration test | inspection in the case of the periodic inspection of a nuclear reactor, and the replacement procedure example to a new fuel assembly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Reactor core 11 Fuel assembly 12 Core unit 13 Space 14 Control rod 15 Control rod drive means 16 Control rod drive shaft 18 Plasma 20, 20A, 20B, 20C Reactor inspection device 21 Fuel pool (reactor water )
22 cylindrical sealed container 23 laser device 24 irradiation optical system 25 fluorescence condensing optical system 26 spectroscopic means 27 computer 31 transmission window 32 total reflection mirror 33 condensing lens 34 perforated mirror 35 condensing lens 37 member surface 38 surface layer 40 interval Holding spacer 41 Sealing packing 43 Vacuum container 44 Discharge (exhaust) piping 45 Discharge device (exhaust device)
46 Inert Gas Supply Device 47-49 Open / Close Valve 50 Air Supply Pipe 52 Inert Gas Supply Control Device 53 Gas Pressure Gauge 54 Gas Replacement Control Mechanism

Claims (16)

A core unit composed of a set of four fuel assemblies loaded in the nuclear reactor core, and a cross-shaped cross-shaped control rod provided in a space formed in the center of the core unit so as to be movable up and down in the longitudinal direction; The core unit was continuously loaded with a fuel assembly that had been analyzed for hydrogen concentration and determined to be free of hydrogen embrittlement, and the reactor core was configured with a number of core units. A nuclear reactor characterized by A set of four fuel assemblies is loaded on the reactor core to form a core unit, and a control rod with a cross-shaped cross section can be moved up and down in the longitudinal direction in a cross-shaped space formed in the center of the core unit. In the meantime, a large number of core units are arranged in a circular arrangement in plan view with the core unit as a basic unit, and a fuel assembly that is analyzed for hydrogen and has no fear of hydrogen embrittlement is continued in the core unit. A method for operating a nuclear reactor, comprising: controlling the power output of a nuclear reactor core by moving the control rod up and down. When the fuel assembly member is subjected to non-destructive inspection of the hydrogen concentration or hydrogen concentration distribution of the member using laser plasma spectroscopy, and the hydrogen concentration of the fuel assembly member is a predetermined value or less, the fuel assembly 3. The method of operating a nuclear reactor according to claim 2, wherein a fuel assembly of a group represented by the fuel assembly is continuously used. When the fuel assembly member is subjected to non-destructive inspection of the hydrogen concentration or hydrogen concentration distribution of the member using laser plasma spectroscopy, and the hydrogen concentration of the fuel assembly member is a predetermined value or more, the fuel assembly Or replace the fuel assembly of the group represented by this fuel assembly with a new fuel assembly,
When the hydrogen concentration of the fuel assembly is equal to or lower than a set value, the fuel assembly or a group of fuel assemblies represented by the fuel assembly is continuously used, and the operation of the reactor is resumed. A method of operating a nuclear reactor according to claim 2. Inspection objects such as irradiated fuel assemblies installed standing in reactor water or fuel pool water,
A cylindrical sealed container placed opposite to the inspection object;
A laser device for outputting pulsed laser light;
An irradiation optical system for condensing and irradiating the surface of a member of the inspection object through the inside of a cylindrical sealed container with a pulse laser beam output from the laser device;
A fluorescence condensing optical system that guides and collects the fluorescence emitted from the atoms and ions of the plasma generated on the surface of the member to be inspected by the irradiation of the pulse laser beam;
Spectroscopic means for making the fluorescence guided by this fluorescence condensing optical system incident, dividing the wavelength and outputting a light intensity detection signal for each wavelength,
An inspection apparatus for a nuclear reactor, comprising: a calculation means for inputting a fluorescence wavelength from a spectroscopic means and a light intensity signal for each wavelength, calculating a kind and concentration of an element, and analyzing the element by laser plasma spectroscopy. A vacuum vessel capable of forming an airtight space around a member surface of an inspection object such as a fuel assembly in the cylindrical sealed vessel, and a negative or positive pressure gas atmosphere suitable for light emission of hydrogen atoms in the vacuum vessel And an exhaust device for forming a laser beam, condensing and irradiating a laser beam on the surface of a member to be inspected in the vacuum vessel, generating a plasma in the vacuum vessel, and generating a fluorescence having a hydrogen intrinsic wavelength in the fluorescence from the plasma. 6. The nuclear reactor inspection apparatus according to claim 5, wherein measurement is performed. An exhaust device for forming a negative pressure gas atmosphere in the vacuum vessel in a vacuum vessel provided on the lower side of the cylindrical sealed vessel, and an inert gas supply device for supplying an inert gas into the vacuum vessel An inspection apparatus for a nuclear reactor, comprising a gas replacement control mechanism capable of switching and controlling the exhaust of gas in the vacuum vessel and the supply of inert gas. The cylindrical sealed container is provided so as to be movable up and down in the longitudinal direction of an inspection object such as a fuel assembly,
By moving the cylindrical airtight container up and down, the irradiation position of the pulsed laser beam output from the laser device is moved for each pulse of the laser beam or for each of a plurality of pulses, and the hydrogen concentration analysis with the target part surface of the inspection object is performed. The nuclear reactor inspection apparatus according to claim 5, wherein analysis is possible in a longitudinal direction. The cylindrical airtight container is fixedly installed, the irradiation position of the pulse laser light irradiated to the target part of the inspection object is fixed, and the fluorescence from the plasma generated by the irradiation of the pulse laser light is changed to the pulse laser light irradiation position. A reactor inspection apparatus characterized by being able to analyze a hydrogen concentration distribution in a member depth direction of an inspection object such as a fuel assembly by continuously acquiring the same without changing the above. The spectroscopic means includes a fluorescence spectroscopic unit for distinguishing fluorescence having a wavelength unique to hydrogen from light emission of plasma generated by pulsed laser light applied to a target site of an inspection object, and a wavelength unique to hydrogen and the intensity of the fluorescence. The nuclear reactor inspection apparatus according to claim 5, further comprising: a fluorescence detection unit that detects the fluorescence detection unit. A plurality of fuel assemblies that contain a plurality of fuel rods in a channel box and through which a coolant passes, and control rods that are arranged to be movable in the longitudinal direction in a space between the fuel assemblies. And a nuclear reactor inspection method for analyzing a hydrogen concentration of a member of an inspection target such as the fuel assembly,
A method of inspecting a nuclear reactor, wherein the hydrogen concentration of a member of the inspection object is analyzed nondestructively by laser plasma spectroscopy at the time of periodic inspection of the nuclear reactor. Condensing and irradiating the surface of a member to be inspected with pulsed laser light output from a laser device,
Generate plasma containing the elements of the object to be inspected by the energy of the irradiated pulsed laser beam,
Analyzing the wavelength of fluorescence emitted from the generated plasma and the light intensity thereof, and analyzing the hydrogen concentration of the inspection object using laser plasma spectroscopy for analyzing the elemental composition of the inspection object. The method for inspecting a nuclear reactor according to claim 11, wherein the nuclear reactor is inspected. The irradiation position of the pulsed laser beam used in the laser plasma spectroscopy is moved in the longitudinal direction of the inspection object for each pulse or for each of a plurality of pulses, and the hydrogen concentration distribution on the surface of the target part of the inspection object is determined. The method for inspecting a nuclear reactor according to claim 12, wherein analysis is performed. By continuously acquiring each pulse without changing the irradiation position of the pulse laser beam used in the laser plasma spectroscopy, the surface of the member of the inspection object is thinly cut by the irradiation of the pulse laser beam. Accordingly, the hydrogen concentration distribution in the depth direction of the member of the inspection object is analyzed. The vacuum container which can form an airtight space around the member surface of the inspection object is provided, and the inert gas supplied into the vacuum container is helium or argon gas. Reactor inspection method. Not only the fluorescence having a wavelength unique to hydrogen generated by plasma generated by condensing and irradiating the surface of a member of the inspection object with pulsed laser light, but also the intrinsic wavelength of at least one element of zirconium, iron, chromium, and oxygen The method for inspecting a nuclear reactor according to claim 12, wherein the fluorescence can be detected by a fluorescence detection unit.

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