METHOD AND DEVICE FOR NON-DESTRUCTIVE TESTING OF A WELDED JOINT OF A NUCLEAR RECIPIENT PART

Description

TECHNICAL FIELD

[0001] The present invention relates to a method and a device for non-destructive ultrasonic testing of a weld made in a nuclear reactor part, for example in a steam generator, in a nuclear reactor vessel or pressurizer. The present invention can be applied in the non-destructive testing of thick welds, i.e. welds with a thickness greater than or equal to 80 mm. STATE OF THE PRIOR ART

[0002] Nuclear reactors contain many parts made by assembling several sections welded together. Thus, the main vessel of a nuclear reactor has a wall made of ferritic steel forgings assembled by welding, ferritic circular butt joints of great thickness. Similarly, steam generators or pressurizers for nuclear reactors are made from sheets or forgings assembled by thick circular welds. Although the manufacture of such parts is subject to every precaution, the welds can contain defects that must be detected.

[0003] To achieve this, the prior art proposes a non-destructive welding testing technique that combines radiography and a manual ultrasonic welding testing method. However, such a technique is time-consuming, requires numerous measuring points, numerous manual adjustments, and furthermore, requires access to the inside and outside of the parts to be tested, which is not always easy.

[0004] US 2007 / 00328 A1 describes the ultrasonic inspection of a weld in a part for a nuclear reactor, using a multi-element TOFD sensor in the “phased-array” technique to probe several areas of the weld; said sensor comprises a multi-element transmitter and a multi-element receiver, aligned along an axis perpendicular to the axis along which the weld extends. STATEMENT OF THE INVENTION

[0005] The inventionaims to remedy the drawbacks of the state of the art by proposing a method and a device for non-destructive testing of welds in parts for nuclear reactors which is faster than those of the prior art, simpler and which does not require access to the interior of the parts.

[0006] Another object of the invention is to propose a method and a device for volumetric control of welds which is more reliable than those of the prior art and which only requires a limited number of acquisitions.

[0007] To do this, the invention proposes to carry out non-destructive testing of welds of parts for nuclear reactors by a combination of the TOFD (Time of flight diffraction) technique, also called "time of flight measurement" and the phased-array technique, also called "multi-element", so as to carry out automated testing of the weld which can be carried out during a single data acquisition.

[0008] More specifically, the invention provides a control method according to claim 1.

[0009] A sensor implementing the conventional TOFD technique is called a "single-element TOFD sensor". Such a sensor comprises a single-element transmitter and a single-element receiver.

[0010] A sensor implementing the TOFD multi-element technique is called a "multi-element TOFD sensor". Such a sensor comprises a multi-element TOFD transmitter and a multi-element receiver.

[0011] Thus, the invention proposes to combine the single-element TOFD technique, which is the conventional TOFD technique, for probing the area close to the outer surface of the part, with the multi-element TOFD technique for probing the area of ​​the weld which is furthest from the outer surface. Thus, using a limited number of sensors, a thick weld can be probed precisely. InIn fact, the process is particularly intended for welds with a thickness between 100 and 300 mm, and preferably between 100 and 250 mm.

[0012] The method according to the invention may also, in addition to the characteristics of claim 1, have one or more of the following characteristics taken independently or in all technically possible combinations.

[0013] Advantageously, the first zone has a thickness strictly less than that of the second zone, which makes it possible to precisely probe the zone close to the exterior surface of the weld.

[0014] The area near the outer surface of the part, called the "first zone", is preferably located at a depth of between 0 and 10 mm from the outer surface of the part. The first zone is preferably located just below the outer surface of the part.

[0015] The single-element TOFD technique in the first zone is preferably implemented with a first frequency, preferably equal to 7.5 MHz.

[0016] The second zone is preferably located at a depth greater than 30 mm, preferably greater than 35 mm. The second zone preferably has a thickness of between 100 and 300 mm. Thus, the entire second zone, which has a significant thickness, is controlled using a single sensor, which saves time.

[0017] The second zone is preferably located at a depth of between 30 and 250 mm, more preferably between 35 and 250 mm.

[0018] The multi-element TOFD technique in the second zone is preferably implemented with a second frequency, preferably equal to 2 MHz

[0019] Advantageously, the weld further comprises a third zone located between the first zone and the second zone, the method using a second single-element TOFD sensor to probe the third zone of the weld.

[0020] The third zone is preferably located at a depth of between 5 and 40 mm, preferably between 6 and 36 mm. The third zone preferably has a thickness of between 10 and 40 mm, more preferably between 10 and 30 mm.

[0021] Each TOFD sensor preferably has a transmitter and a receiver located on either side of the weld.

[0022] The transmitter and receiver of the first single-element TOFD sensor are preferably spaced apart by a first distance D1.

[0023] The transmitter and receiver of the multi-element TOFD sensor are preferably spaced a second distance D3 apart.

[0024] The transmitter and receiver of the second single-element TOFD sensor are preferably spaced apart by a third distance D3.

[0025] The transmitter and receiver of the first multi-element probe are preferably aligned along an axis parallel to the axis of the weld.

[0026] The first multi-element probe emits a beam at a misorientation angle between -15° and +15° in order to optimize the reflective surface of the weld.

[0027] Advantageously, the method also uses a second multi-element probe which makes it possible to search for transverse defects.

[0028] Another aspect of the invention also relates to a control device according to claim 6.

[0029] Advantageously, the device further comprises a second single-element TOFD sensor for probing a third area of ​​the weld.

[0030] The device also includes a first multi-element probe.

[0031] The device preferably also comprises a second multi-element probe. BRIEF DESCRIPTION OF THE FIGURES

[0032] Other characteristics and advantages of the invention will emerge on reading the detailed description which follows, with reference to the appended figures, which illustrate: There figure 1 , a top view of a part controlled by a method according to an embodiment of the invention; The figure 2 , a sectional view of a part controlled by a method according to an embodiment of the invention; The figure 3 , a sectional view of a part controlled by a method according to an embodiment of the invention; The figure 4 , a side view of a multi-element probe used by a method according to an embodiment of the invention; The Figure 5 , a perspective view of the probe of the figure 4 ; THE figures 6 and 7, top views of the probe of the figure 4 ; There figure 8 , a top view of a part controlled by a control method according to an embodiment of the invention; The figure 9 , a sectional view of a part controlled by a method according to an embodiment of the invention.

[0033] For clarity, identical or similar elements are identified by identical reference signs throughout the figures. DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT

[0034] There figure 1 represents a top view of a part whose welding 1 is to be controlled with a device and a control method according to an embodiment of the invention.

[0035] The control device 2 used is shown in the figure 1 This control device 2 comprises a plate 3 on which are fixed: A first single-element TOFD sensor 4 for probing a first zone z1 of the weld; A multi-element TOFD sensor 5 for probing a second zone z2 of the weld; a second single-element TOFD sensor 6 for probing a third zone z3 of the weld.

[0036] The first single-element TOFD sensor 4 comprises a single-element TOFD transmitter 7 and a single-element TOFD receiver 8. The transmitter 7 and the receiver 8 are aligned along an axis 11 perpendicular to the axis along which the weld 1 extends. The distance D1 between the transmitter 7 and the receiver 8 is chosen so that the first sensor 4 makes it possible to control the zone z1 of the weld which is located directly under the outer surface 10 of the part to be controlled. The zone z1 is preferably located at a depth p1 of between 1.5 and 9.5 mm relative to the outer surface of the part.

[0037] The second single-element TOFD sensor 6 comprises a single-element TOFD transmitter 12 and a single-element TOFD receiver 13. The transmitter 12 and the receiver 13 are aligned along an axis 14 perpendicular to the axis along which the weld 1 extends. The distance D3 between the transmitter 12 and the receiver 13 is chosen so that the second sensor 6 makes it possible to control the zone z3 of the weld which is located under the zone z1. The zone z3 is preferably located at a depth p3 of between 6 and 36 mm relative to the external surface of the part.

[0038] The multi-element TOFD sensor 5 comprises a multi-element TOFD transmitter 15 and a multi-element TOFD receiver 16. The transmitter 15 and the receiver 16 are aligned along an axis 17 perpendicular to the axis along which the weld 1 extends. The distance D2 between the transmitter 15 and the receiver 16 is chosen so that the multi-element TOFD sensor makes it possible to monitor the zone z2 of the weld which is located under the zone z3. The zone z2 of the weld is preferably located at a depth p2 of between 35 and 250 mm relative to the outer surface of the part. The multi-element TOFD transmitter 15 may for example comprise sixteen elements, each element implementing the TOFD technique. Each element of the multi-element TOFD transmitter can be controlled independently of the other elements so as to emit an ultrasonic beam making it possible to probe a part of the zone z2 of the weld.To do this, control parameters are inserted into a computer and pulse delay laws on the elements are defined. Each element has a function in angle and detection depth. The TOFD technique is thus implemented on the basis of a combination of conventional sensors for the zones z1, z2 close to the surface and multi-element for the zone z2 further from the outer surface. The thickness to be inspected is divided into several zones. Each zone is inspected by a dedicated TOFD configuration. The zones z1, z2, z3 were defined on the basis of simulations and practical tests on blocks with notches. It is thus possible to control thicknesses between 35 and 250 mm with the TOFD technique, which was not the case in the prior art. The acquisitions thus carried out can be used according to two methods: scanning parallel to the weld and non-parallel to the weld.

[0039] The first and second single-element TOFD sensors preferably operate at a frequency of 7.5 MHz. The multi-element TOFD sensor preferably operates at a frequency of 2 MHz.

[0040] The plate 3 also comprises a first multi-element probe 18 comprising a multi-element transmitter 19 and a multi-element receiver 20. This first multi-element probe 18 makes it possible to vary the opening angle from 45° to 70° and the skew angle, preferably from -15 to + 15°, as shown in the Figures 5 and 6 . The multi-element transmitter 19 and the multi-element receiver 20 are arranged on the same side of the weld. The multi-element transmitter 19 is shown more precisely in the figures 4 to 5. The multi-element transmitter 19 comprises a matrix of 56 individual elements 21, each of which can be controlled independently. These individual elements 21 are connected to suitable control electronics enabling independent and simultaneous transmission and reception on each of the channels. These electronics must also be able to apply different electronic delays to transmission and reception for each channel. The traditional mechanical scanning is replaced by a much faster electronic scanning, which makes it possible to detect longitudinal and transverse defects. Electronic focusing makes it possible to use a single sensor to work at different depths. Electronic deflection allows the variation of the incidence angles with a single sensor.

[0041] The 18 multi-element probe can generate transverse waves with refracted angles of 45° to 70° and a disorientation of -15° to +15°, called “skew” in English.

[0042] Plate 3 also includes a second multi-element probe 22.

[0043] As shown in the figure 8 , the plate 3 thus formed moves relative to the weld along the path 24, along an x ​​axis and along a y axis. The acquisition of the ultrasonic data is carried out by a “raster” scan. The resolution of the x axis defines the spatial acquisition points in the direction of the orientation of the beam of the sensors which aim at the weld perpendicularly. The resolution of the y axis defines the spatial acquisition points in the direction of the orientation of the beam of the sensors which aim parallel to the weld.

[0044] In reference to the figure 9 , the multi-element sensors are positioned to obtain an optimized scanning amplitude for an angle of 60°.

[0045] The plate according to the invention therefore makes it possible to move all the sensors at the same time and with the same amplitude relative to the weld. It also makes it possible to check thick welds only by the external surface of the part to be checked.

[0046] Naturally, the invention is not limited to the embodiments described with reference to the figures and variants can be envisaged without departing from the scope of the invention.

Claims

1. A method of non-destructive testing of a weld (1) in a part for a nuclear reactor, the testing combining the time-of-flight measurement technique and the phased-array technique, the part comprising an external surface (10), the weld (1) comprising a first zone (z1) close to the outer surface (10) and a second zone (z2) further from the outer surface (10), the method using an inspection device (2) comprising a plate (3) to which are fixed: - a first single-element TOFD sensor (4) for probing the first zone (z1) of the weld (1), the first single-element TOFD sensor (4) comprising a single-element transmitter (7) and a single-element receiver (8), the single-element transmitter (7) and the single-element receiver (8) being aligned along an axis (11) perpendicular to the axis along which the weld (1) extends, and - a multi-element TOFD sensor (5) for probing the second zone (z2) of the weld (1), the multi-element TOFD sensor (5) comprising a multi-element transmitter (15) and a multi-element receiver (16), each element of the multi-element transmitter being controllable independently of the other elements so as to emit an ultrasonic beam enabling part of the second zone (z2) to be probed, control parameters being inserted in a computer and pulse delay laws on the elements of the multi-element transmitter being defined, the multi-element transmitter (15) and the multi-element receiver (16) being aligned along an axis (17) perpendicular to the axis along which the weld (1) extends, the stage (3) comprising a first multi-element probe (18), the first multi-element probe (18) emitting transverse wave beams, the first multi-element probe (18) being capable of generating transverse waves with refracted angles of 45° to 70° and a disorientation of -15° to +15°, the first multi-element probe (18) comprising a multi-element transmitter (19) and a multi-element receiver (20), the multi-element transmitter (19) and the multi-element receiver (20) being arranged on the same side of the weld.

2. A method according to the preceding claim, in which the first zone (z1) is located at a depth (p1) of between 0 and 10 mm.

3. A method according to one of the preceding claims, in which the second zone (z2) is located at a depth (p2) of between 30 and 300 mm.

4. A method according to any of the preceding claims, wherein the weld (1) further comprises a third zone (z3) located between the first zone (z1) and the second zone (z2), the method using a second single element TOFD sensor (6) to probe the third zone (z3) of the weld (1).

5. A method according to the preceding claim, in which the third zone (z3) is located at a depth of between 5 and 40 mm.

6. A device for non-destructive testing, combining the time-of-flight measurement technique and the phased-array technique, of a weld in a part for a nuclear reactor, the device comprising a plate (3) to which are fixed: - a first single-element TOFD sensor (4) for probing a first zone (z1) of the weld (1), the first single-element TOFD sensor (4) comprising a single-element transmitter and a single-element receiver, the single-element transmitter (7) and the single-element receiver (8) being adapted to be aligned along an axis (11) perpendicular to which the weld (1) extends; and - a multi-element TOFD sensor (5) for probing a second zone (z2) of the weld (1) further from an external surface (10) of the part to be inspected than the first zone (z1), the multi-element TOFD sensor (5) comprising a multi-element transmitter and a multi-element receiver, the multi-element transmitter (15) and the multi-element receiver (16) being aligned along an axis (17) perpendicular to the axis along which the weld (1) extends, each element of the multi-element transmitter being controllable independently of the other elements so as to transmit an ultrasound beam making it possible to probe part of the second zone (z2), and the plate (3) further comprising a first multi-element probe (18), the first multi-element probe (18) being capable of generating transverse waves with refracted angles of 45° to 70° and a disorientation of -15° to +15°, the first multi-element probe (18) comprising a multi-element transmitter (19) and a multi-element receiver (20), the multi-element transmitter (19) and the multi-element receiver (20) being capable of being arranged on the same side of the weld.

7. A test device as claimed above, also comprising a second single-element TOFD sensor (6) capable of probing a third zone (z3) of the weld (1).