JP2005172641A - Monitoring test piece of reactor pressure vessel and method for monitoring/evaluating degradation status - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a monitoring test piece of a reactor pressure vessel which has a characteristic that when stress of a specific level corresponding to the operation state works in high temperature region not causing brittle fracture and when temperature lowers to a region possible to cause brittle fracture, stress lowers to a level not causing brittle fracture, and a method for monitoring/evaluating the degradation in the reactor pressure vessel by using the test piece. <P>SOLUTION: A recess part 23 is provided to one side of a test piece body 16a, a notch 24 is continuously provided on the bottom of the recess part 23. A stress adding function member 26 is inserted in the recess part 23. The test piece body 16a and the stress adding function member 26 are arranged in this state in a reactor, so that a load works on the test piece body 16a during temperature elevation in the reactor and thus degradation of materials used in the reactor pressure vessel 1 can be historically monitored. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a test piece for monitoring a deterioration state of a material used for a reactor pressure vessel of a commercial light water reactor over time, and a method for monitoring and evaluating the test piece.

Generally, a pressurized water reactor is used to drive a turbine by introducing a high-temperature and high-pressure reactor coolant heated by the nuclear reaction heat of the reactor pressure vessel core to a steam generator provided outside the reactor pressure vessel. Steam is generated (see, for example, Patent Document 1).
In this way, reactor pressure vessels, including boiling water reactor pressure vessels, are vessels that contain the core of the thermal energy generation source, and are exposed to harsh environments that are subject to neutron irradiation from core fuel in addition to high temperature and pressure Therefore, it is a device that requires high reliability and must be sound for a long time. The materials used in the reactor pressure vessel undergo irradiation embrittlement when irradiated with neutrons, so the progress of embrittlement is monitored while the amount of embrittlement is evaluated and operation is performed so as not to cause brittle fracture. Need to manage.
JP 2002-257971 A

  At present, the evaluation of the embrittlement amount by neutron irradiation of the reactor pressure vessel is performed based on the test results obtained by monitoring test pieces (collected from the reactor pressure vessel) installed in the reactor pressure vessel.

However, while the reactor pressure vessel described above is subjected to a stress of about 15 kgf / mm ² in a normal operating state, neutron irradiation is performed in a state where no load is applied to the conventional monitoring specimen. Therefore, when there is an influence on the embrittlement due to the action of stress, the test result of the monitoring test piece does not include the effect.
On the other hand, in a state where stress is constantly applied to the monitoring test piece, there is a possibility that the monitoring test piece breaks due to brittle fracture when the temperature decreases due to the shutdown of the reactor.

  The present invention has been made in view of such a situation, and its purpose is to cause a predetermined level of stress corresponding to the operating state in a high temperature region where no brittle fracture occurs, which may cause brittle fracture. Provided are a reactor pressure vessel monitoring test piece having a characteristic that stress is reduced to a level at which brittle fracture does not occur at a low temperature region, and a method for monitoring and evaluating the deterioration state of the reactor pressure vessel using the test piece. There is.

  In order to solve the above-described problems of the prior art, in the present invention, a recess is provided on one side of the test piece body, a notch is continuously provided on the bottom surface of the recess, and a stress applying function member is provided in the recess. In this state, by placing the test piece body and the stress applying functional member in the furnace, a load acts on the test piece body at the time of temperature rise in the furnace, and it is used for a reactor pressure vessel. The deterioration state of the material is monitored over time.

  Further, in the present invention, a notch portion is provided on one side of the test piece main body, and the stress applying functional member is disposed in a direction intersecting the notch portion with the test piece main body interposed therebetween, and the test piece main body and Both ends of the stress applying functional member are fixed with a jig, and in this state, the test piece main body and the stress applying functional member are arranged in the furnace, thereby loading the test piece main body at the time of temperature rise in the furnace. Acts to monitor the deterioration of the materials used in the reactor pressure vessel over time.

  Furthermore, in the present invention, a notch portion is provided on one side of the test piece main body, stress applying function members are respectively arranged at two support points and one load point of the test piece main body, and the test piece main body And the periphery of the stress applying functional member is fixed with a jig, and in this state, the test piece main body and the stress applying functional member are disposed in the furnace, so that the test piece main body can be attached to the test piece main body when the furnace is heated. The load is applied and the deterioration state of the material used for the reactor pressure vessel is monitored over time.

  As described above, the reactor pressure vessel monitoring test piece according to the present invention is provided with a recess on one side of the test piece body, a notch is continuously provided on the bottom surface of the recess, and a stress applying function in the recess. A member is inserted, and in this state, the test piece main body and the stress applying functional member are disposed in the furnace, so that a load acts on the test piece main body when the temperature rises in the furnace, and the reactor pressure vessel Since deterioration of the materials used is monitored over time, there is a possibility of causing brittle fracture by applying a predetermined level of stress corresponding to the operating condition to the test piece body in a high temperature range where brittle fracture does not occur. When the temperature is low, the stress on the test piece body can be reduced to a level at which brittle fracture does not occur. Therefore, if the monitoring test piece of the present invention is used, it is possible to monitor the deterioration state of the reactor pressure vessel with high accuracy, promptly and over time, and to ensure the reliability of the reactor pressure vessel.

  Further, the reactor pressure vessel monitoring test piece according to the present invention is provided with a notch portion on one side of the test piece main body, and the stress applying functional member in the direction intersecting the notch portion between the test piece main bodies, respectively. At the same time, both ends of the test piece main body and the stress applying functional member are fixed with a jig, and in this state, the test piece main body and the stress applying functional member are arranged in the furnace. Since the load acts on the test piece main body at the time of temperature and the deterioration state of the material used for the reactor pressure vessel is monitored over time, the same effect as the above invention can be obtained, Charpy impact characteristics and fracture toughness characteristics can be examined from another viewpoint.

  Furthermore, the monitoring test piece of the reactor pressure vessel according to the present invention is provided with a notch portion on one side of the test piece body, and a stress applying function member is provided at two support points and one load point of the test piece body. Each of the test piece main body and the stress applying functional member is fixed with a jig, and in this state, the test piece main body and the stress applying functional member are arranged in the furnace. Since a load acts on the test piece body at the time of temperature rise and the deterioration state of the material used for the reactor pressure vessel is monitored over time, the same effect as the above invention can be obtained. From another viewpoint, Charpy impact characteristics and fracture toughness characteristics can be examined.

  Hereinafter, the present invention will be described in detail based on illustrated embodiments.

  1 to 5 show a first embodiment of a monitoring test piece for a reactor pressure vessel according to the present invention. FIG. 1 is a cross-sectional view schematically showing a reactor pressure vessel in which a monitoring test piece of this embodiment is arranged, and FIG. 2 is a main part showing a state in which an irradiation test piece capsule is installed in the reactor pressure vessel of FIG. FIG. 3 is a perspective view showing the irradiation test piece capsule of FIG. 2, FIG. 4 is a schematic plan view showing the monitoring test piece of this embodiment, and FIG. 5 is stress on the test piece body of the monitoring test piece of this embodiment. It is a temperature schematic diagram based on the difference in the used material of the stress addition functional member which provides.

As shown in FIG. 1, the reactor pressure vessel 1 of the first embodiment includes a vessel body 2 formed in a bottomed cylindrical shape and a lid 3 that is detachably attached to an upper opening of the vessel body 2. A coolant inlet nozzle 4 and a coolant outlet nozzle 5 are provided on the upper side wall of the container body 2. A cylindrical core tank 6 is supported inside the container body 2 from a shelf near the upper opening, and a downcomer 7 is defined between the core tank 6 and the container body 2. . A lower core support plate 8 and a lower core plate 9 are horizontally provided at the lower portion of the core tank 6, and the core tank 6 is supported in the horizontal direction from the vessel body 2 at the position of the lower core support plate 8. Yes.
A number of fuel assemblies (not shown) are arranged adjacent to each other above the lower core plate 9 to form a core 10. The upper end of the fuel assembly is pressed by the upper core plate 11, and an upper plenum 12 is formed above it. The upper plenum 12 communicates with the outlet nozzle 5 via the nozzle flange of the core 6. The bottom of the container body 2 is formed as a hemispherical end plate 13, and a lower plenum 14 is formed between the end plate 13 and the lower core support plate 8.

  The flow of the coolant C in the reactor pressure vessel 1 having such a structure will be described. First, the coolant C flows through a pipe by a coolant pump (not shown) and flows into the internal downcomer 7 through the inlet nozzle 4. . Then, the coolant C flows down in the downcomer 7 as indicated by an arrow, reverses in the lower plenum 14, flows through the lower core support plate 8 and the lower core plate 9, and enters the core 10. In the core 10, while the coolant C flows upward along the outside of the fuel rod of the fuel assembly, it absorbs the nuclear reaction heat and rises in temperature. Thereafter, the coolant C rises in the core 10 and reaches the upper plenum 12, and then the coolant C turns in the horizontal direction and flows out from the outlet nozzle 5 toward the steam generator.

On the other hand, in the reactor pressure vessel 1 of the present embodiment, as shown in FIG. 2, a long sealed irradiation test piece capsule 15 is disposed. In this irradiation test piece capsule 15, various monitoring test pieces 16 and loads used for monitoring the deterioration state of the material used for the reactor pressure vessel 1 by neutrons over time and evaluating the amount of embrittlement. The jigs 17 and 18 are arranged in a plurality of rows.
Therefore, as shown in FIG. 3, the irradiation test piece capsule 15 includes an upper plug 19 and a bottom plug 20 at the upper and lower ends, and the monitoring test piece 16 and the load jigs 17 and 18 include a temperature monitor 21 and a spacer. In the state where 22 etc. are interposed, it arrange | positions between the upper part plug 19 and the bottom part plug 20. FIG. Moreover, the irradiation test piece capsule 15 is attached to the outer peripheral surface of the reactor core 6 by the upper plug 19 and the bottom plug 20 in a state in which the monitoring test piece 16 and the load jigs 17 and 18 are enclosed. The monitoring test piece 16 is placed in the same environment as the reactor pressure vessel 1. FIG. 3 shows an example of the arrangement of the monitoring test piece 16 and the load jigs 17 and 18 in the present embodiment.

The monitoring test piece 16 of the first embodiment includes a test piece main body 16a which is a compact tension test piece (CT test piece) as shown in FIG. A concave portion 23 having a U-shaped cross section is provided at the center of one side surface of the test piece main body 16a, and a notch portion 24 and a crack 25 extending toward the opposite side surface are formed on the bottom surface of the concave portion 23. Are provided continuously. These notches 24 and cracks 25 are provided so that the stress load is strongly applied to the test piece main body 16a.
Further, as shown in FIG. 4A, a stress applying function member 26 having substantially the same cross-sectional shape and having substantially the same dimensions is inserted and disposed in the recess 23 of the test piece main body 16a as a wedge.

As the stress application function member 26, a thermoelastic martensitic transformation (shape memory effect) is performed within a range from room temperature (about 25 ° C.) to the operating temperature range of the reactor pressure vessel 1 (in-furnace operating temperature, about 290 ° C.). As shown in FIG. 4B, as the temperature rises, the stress applying functional member 26 expands and expands due to the shape memory effect, and the stress load is applied to the test piece main body 16a. It is comprised so that it may act on the arrow direction (the direction which the notch 24 and the crack 25 open). Candidate materials for such a stress application function member 26 include Fe-Mn-Si based alloys and Fe-Cr-Ni-Mn-Si based alloys, etc., but for reducing exposure due to activation associated with transmutation, It is preferable to select a material that does not contain Co.
Further, as the stress application function member 26, a material having a linear expansion coefficient larger than that of the material of the test piece main body 16a (for example, low alloy steel) can be used. As shown in FIG. As the temperature increases, the stress application function member 26 expands and expands due to the difference in thermal expansion so that the stress load acts on the test piece main body 16a in the direction of the arrow (the direction in which the notch 24 and the crack 25 open). It is configured. A candidate material for such a stress application function member 26 is austenitic stainless steel.
As shown in FIG. 5, when a shape memory alloy is used as the material of the stress application function member 26, a characteristic that an applied stress abruptly occurs in the middle of the operating temperature as shown by a solid line and thereafter becomes a constant stress. Have. In addition, when a material having a high linear expansion coefficient is used, the applied stress gradually increases as the operating temperature increases as indicated by the broken line.

In order to evaluate the amount of embrittlement caused by neutron irradiation of the reactor pressure vessel 1 using the monitoring test piece 16 including the test piece main body 16a and the stress application function member 26 of the first embodiment, first, the monitoring test is performed. The irradiation test piece capsule 15 in which the piece 16 is enclosed is placed in the furnace, and the reactor pressure vessel 1 is operated for a certain period in this state. During this time, a predetermined level of stress corresponding to the operating state of the reactor pressure vessel 1 is applied to the test piece main body 16a in a high temperature region where no brittle fracture occurs. Is being loaded.
Next, the operation of the reactor pressure vessel 1 is stopped at the time of periodic inspection, the lid 3 is removed, the upper opening is opened, and the irradiation test piece capsule 15 is taken out from the container main body 2 and monitored from this irradiation test piece capsule 15. The test piece 16 is taken out. During this time, even if the monitoring test piece 16 is in a low temperature region where there is a possibility of brittle fracture, the stress load on the test piece main body 16a is reduced to a level at which brittle fracture does not occur.
Thereafter, the monitoring test piece 16 is installed in a jig of a tester (not shown) using a pair of fitting holes 27 provided in the test piece main body 16a. In this state, if the fracture toughness is measured by applying a load load in the direction in which the notch 24 and the crack 25 of the test piece main body 16a are opened by the test machine, the amount of embrittlement due to neutron irradiation of the reactor pressure vessel 1 is increased. It can be evaluated through the monitoring test piece 16, and the deterioration state of the reactor pressure vessel 1 can be monitored over time.

FIG. 6 is a schematic plan view showing the temperature rising state of the three-point bending test piece of the monitoring test piece according to the second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals. Description is omitted.
The monitoring test piece 16 according to the second embodiment of the present invention is different from that of the first embodiment in that the test piece main body 16b is a three-point bending test piece. Therefore, the test piece main body 16b is formed in a rectangular shape in a plan view as shown in FIG. 6, and a concave portion 23 having a U-shaped cross section is provided at the center of one side surface of the long side. The bottom surface of the recess 23 is continuously provided with a notch 24 and a crack 25 extending toward the opposite side surface.

  In order to evaluate the amount of embrittlement caused by neutron irradiation of the reactor pressure vessel 1 using the test specimen 16 provided with the specimen main body 16b and the stress application function member 26 of the second embodiment, Similarly, the reactor pressure vessel 1 is operated for a certain period, and after the operation is stopped, the monitoring test piece 16 is taken out from the irradiation test piece capsule 15. Then, as shown in FIG. 6, the test piece main body 16 b is installed on a jig of a test machine (not shown) in a state where the two positions on both ends of the lower surface on the concave portion 23 side are supported as support points. In this state, if the test machine is used to measure the fracture toughness by applying a load in the direction of the arrow with one place at the center of the upper surface opposite to the concave portion 23 of the test piece body 16b as the load point, the first embodiment described above. Similarly, the amount of embrittlement caused by neutron irradiation of the reactor pressure vessel 1 can be evaluated through the monitoring test piece 16.

FIG. 7 is a schematic plan view showing the temperature rising state of the three-point bending test piece of the monitoring test piece according to the third embodiment of the present invention. The same parts as those in the second embodiment are denoted by the same reference numerals. Description is omitted.
The monitoring test piece 16 according to the third embodiment of the present invention is different from that of the second embodiment in that the stress applying function member 36 is inserted in the center of one side surface of the test piece main body 16b which is a three-point bending test piece. The recess is not provided, and only the notch 24 and the crack 25 are provided. On the other hand, as shown in FIG. 7, the stress application function member 36 is a rod-like material made of the same material as the stress application function member 26 of the first and second embodiments and having the same size as the length of the test piece main body 16b. It is formed in the body, and is arranged at intervals in the direction intersecting the notch 24 and the crack 25 with the test piece main body 16b interposed therebetween. In addition, both ends of the test piece main body 16b and the stress application function member 36 are fixed by the loading jig 17, respectively.

  In order to evaluate the amount of embrittlement caused by neutron irradiation of the reactor pressure vessel 1 using the test specimen 16 provided with the specimen main body 16b and the stress application function member 36 of the third embodiment, Similarly, the reactor pressure vessel 1 is operated for a certain period, and after the operation is stopped, the monitoring test piece 16 and the load jig 17 are taken out from the irradiation test piece capsule 15. Then, the test piece main body 16b is separated from the stress applying function member 36 and the loading jig 17, and, similar to the one shown in FIG. 6, two places on both ends of the lower surface on the cutout portion 24 side of the test piece main body 16b. Install it on the jig of the testing machine (not shown) while supporting it as a supporting point. In this state, if the test machine is used to measure the fracture toughness by applying a load in the direction of the notch 24 with the central portion of the upper surface opposite to the notch 24 of the test piece body 16b as a load point. As in the second embodiment, the amount of embrittlement caused by neutron irradiation of the reactor pressure vessel 1 can be evaluated through the monitoring test piece 16.

FIG. 8 is a schematic plan view showing the temperature rising state of the three-point bending test piece of the monitoring test piece according to the fourth embodiment of the present invention. The same reference numerals are used for the same parts as those in the second and third embodiments. A description thereof will be omitted.
The monitoring test piece 16 according to the fourth embodiment of the present invention is different from that of the second and third embodiments in that the stress applying functional member 36 is provided at the center of one side surface of the test piece main body 16b which is a three-point bending test piece. There is no recessed portion for inserting a stub, and only the notch portion 24 and the crack 25 are provided. Further, as shown in FIG. 8, the stress application function member 46 is made of the same material as the stress application function members 26 and 36 of the first to third embodiments, but is formed in a square shape in plan view. In other words, the test piece body 16b is arranged at a total of three places including two support points and one load point. Moreover, the periphery of the test piece main body 16b and each stress applying functional member 46 is fixed by a frame-shaped load jig 18 formed in a size surrounding the test piece main body 16b and each stress applying functional member 46.

  In order to evaluate the amount of embrittlement caused by neutron irradiation of the reactor pressure vessel 1 using the test specimen 16 provided with the specimen main body 16b and the stress application function member 46 of the fourth embodiment, Similarly, the reactor pressure vessel 1 is operated for a certain period, and after the operation is stopped, the monitoring test piece 16 and the load jig 18 are taken out from the irradiation test piece capsule 15. Then, the test piece main body 16b is separated from the stress applying function member 46 and the load jig 18, and, similar to the one shown in FIG. 6, two places on both ends of the lower surface on the cutout portion 24 side of the test piece main body 16b. Install it on the jig of the testing machine (not shown) while supporting it as a supporting point. In this state, if the test machine is used to measure the fracture toughness by applying a load in the direction of the notch 24 with the central portion of the upper surface opposite to the notch 24 of the test piece body 16b as a load point. As in the second embodiment, the amount of embrittlement caused by neutron irradiation of the reactor pressure vessel 1 can be evaluated through the monitoring test piece 16.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the scope of the present invention. is there.
For example, in the monitoring test piece 16 according to the third and fourth embodiments shown in FIGS. 7 and 8, the test piece main body 16b that is a three-point bending test piece is applied, but the test piece main body 16c that is a Charpy impact test piece is used. It may be applied. Also in the case of the test piece main body 16c according to this modification, as shown in FIG. 6, the test piece main body 16c is not shown in the state of supporting the two points on both ends of the lower surface on the cutout portion 24 side as support points. Installed in the jig of the testing machine, and with a pendulum-shaped hammer etc., hitting the center of the upper surface opposite the notch 24 of the test piece body 16c as a load point in the direction of the notch 24 If the Charpy impact value is measured, the amount of embrittlement due to neutron irradiation of the reactor pressure vessel 1 can be evaluated through the monitoring specimen 16 as in the third and fourth embodiments.

It is sectional drawing which shows roughly the reactor pressure vessel by which the monitoring test piece which concerns on 1st Embodiment of this invention is arrange | positioned. It is principal part sectional drawing which shows the state which installed the irradiation test piece capsule in the reactor pressure vessel of FIG. It is a perspective view which shows the irradiation test piece capsule of FIG. BRIEF DESCRIPTION OF THE DRAWINGS The compact tension test piece of the monitoring test piece which concerns on 1st Embodiment of this invention is shown, Comprising: (a) is a schematic plan view of the room temperature state, (b) is a schematic plan view of the state at the time of temperature rising. is there. It is a temperature schematic diagram based on the difference in the material used of the stress addition functional member which gives stress to the test piece main body of the monitoring test piece of this embodiment. It is a schematic plan view which shows the state at the time of temperature rising of the 3-point bending test piece of the monitoring test piece which concerns on 2nd Embodiment of this invention. It is a schematic plan view which shows the state at the time of temperature rising of the 3 point | piece bending test piece (or Charpy impact test piece) of the monitoring test piece which concerns on 3rd Embodiment of this invention. It is a schematic plan view which shows the state at the time of temperature rising of the 3 point | piece bending test piece (or Charpy impact test piece) of the monitoring test piece which concerns on 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reactor pressure vessel 2 Vessel main body 6 Reactor core tank 15 Irradiation test piece capsule 16 Monitoring test piece 16a, 16b, 16c Test piece main body 17, 18 Load jig 23 Recess 24 Notch 25 Crack 26, 36, 46 Stress application Functional members

Claims (9)

A concave portion is provided on one side of the test piece main body, and a notch portion is continuously provided on the bottom surface of the concave portion, and a stress applying function member is inserted into the concave portion, and in this state, the test piece main body and the stress applying function are provided. By placing the members in the furnace, a load was applied to the test piece body during the temperature rise in the furnace, and the deterioration state of the material used for the reactor pressure vessel was monitored over time. Characteristic reactor pressure vessel monitoring specimen. A notch portion is provided on one side of the test piece main body, and the stress applying functional member is arranged in a direction intersecting the notch portion between the test piece main body and both ends of the test piece main body and the stress applying functional member. In this state, the test piece main body and the stress applying functional member are arranged in the furnace, so that a load acts on the test piece main body when the temperature rises in the furnace, and the reactor pressure A reactor test specimen for a reactor pressure vessel, characterized in that the deterioration state of the material used for the vessel is monitored over time. A notch is provided on one side of the test piece main body, stress applying functional members are arranged at two support points and one load point of the test piece main body, and the test piece main body and the stress adding functional member The periphery is fixed with a jig, and in this state, the test piece main body and the stress applying functional member are arranged in the furnace, so that a load acts on the test piece main body when the temperature rises in the furnace, and the nuclear reactor A reactor test specimen for a reactor pressure vessel, characterized in that a deterioration state of a material used for the pressure vessel is monitored over time. The reactor pressure according to any one of claims 1 to 3, wherein a material having a thermoelastic martensitic transformation within a range of room temperature to an operating temperature in the reactor is used as the stress application function member. Container test specimen. The reactor pressure vessel monitoring test piece according to any one of claims 1 to 3, wherein a material having a larger linear expansion coefficient than the material of the test piece main body is used as the stress application function member. . 6. The reactor pressure vessel monitoring test piece according to claim 1, wherein the test piece body is a compact tension test piece. 6. The reactor pressure vessel monitoring test piece according to claim 1, wherein the test piece body is a three-point bending test piece. 6. The reactor pressure vessel monitoring test piece according to claim 2, wherein the test piece main body is a Charpy impact test piece. The monitoring test piece according to any one of claims 1 to 8 is installed in a reactor pressure vessel, taken out during periodic inspection, and a deterioration state of the reactor pressure vessel is monitored by performing a fracture toughness test or an impact test. • How to evaluate.

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