Patent ID: 12259342

DETAILED DESCRIPTION

FIG.1shows an example of a handheld inspection device100for inspecting an infrastructure10having a structure wall20at least partially supported into material such as soil12. Other examples of supporting material can include, but not limited to, cement, mortar, grout and any other suitable supporting material.

As depicted, the handheld inspection device100has a portable frame102to which are mounted a high energy photon source104and a scattered photon detector106. Examples of such a high energy photon source can include, but is not limited to, a gamma ray source comprising an unstable isotope emitting high energy photons from a natural decay process, an x-ray tube, a cyclotron produced radionuclide, a fast neutron source, or any combination thereof. A controller108is also communicatively coupled at least to the scattered photon detector106.

The high energy photon source104has a field of radiation110which diverges towards a target region112of the infrastructure10. The high energy photon source104is used to radiate a photon beam114along the field of radiation110and at least partially penetrates across the structure wall20and through the soil12behind said structure wall20. In some embodiments, the controller108may also be communicatively coupled to the high energy photon source104, to its power supply and/or to a shutter thereof, in order to control the radiation of the photon beam114.

It is noted that the high energy photon source104, and/or its photon beam114, has a radioactivity level below a threshold radioactivity level. For instance, Schedule 1 in Nuclear Substances and Radiation Devices Regulations (SOR/2000-207) under the Nuclear Safety and Control Act (S. C. 1997, c.9) defines the exemption quantities for various isotopes. Cobalt-57 and Cesium-137 have threshold radioactivity levels of 1×106and 1×104Becquerels (or 100 kBq and 10 kBq), respectively. In some embodiments, the high energy photon source104includes two Cesium-137 isotope sources operated at 300 kBq each which may require a license in Canada. In the United States, however, such high energy photon sources do not require a license, as the threshold radioactivity level may be about 370 kBq. The threshold radioactivity level is set so that the high energy photon source104cannot be identified as a too radioactive radiation source which would otherwise require a minimal amount of safety requirements. In some embodiments, the threshold radioactivity level may be below 400 kBq, preferably below 375 kBq, and most preferably below 350 kBq. Accordingly, the handheld inspection device100can be operated by operators with minimal amount of training and/or minimal backscatter shielding; thereby simplifying the use of the handheld inspection device100compared to more sophisticated inspection apparatuses. An example of such a high energy photon source104can include, but is not limited to, Cesium-137 as an unstable isotope generating the photon beam. However, other high energy photon sources such as Iridium-192, Europium-152 or any suitable unstable isotope may also be used. The high energy photon source104can have a shielding member116shielding the operator from any of its radiation. The high energy photon source104can also have a diverging member118ensuring that the field of radiation110diverges towards the target region112. The shielding and diverging members116and118can be arranged such that the high energy photon source104bombards the target region112while blocking such radiation from directly reaching the scattered photon detector106and/or the operator.

The scattered photon detector106has a field of view120which diverges towards the target region112of the infrastructure10. As shown, the field of view120encompasses at least a portion of the field of radiation110. In this way, the scattered photon detector106detects scatter events incoming from the target region112during a given period of time, and generates a signal indicative of the detected scatter events detected during that period of time. Examples of scattered photon detectors can include, but is not limited to, a photomultiplier tube, a scintillator, a solid-state detector, a silicon photo-multiplier, a Geiger-Mueller detector, a liquid scintillation detector and the like. In some preferred embodiment, the scattered photon detector106can be provided in the form of a single photon sensitive detector capable of detecting high energy photons in the gamma range of the electromagnetic spectrum. Such scattered photon detectors can be, for example, made up of scintillation crystals coupled with silicon photomultipliers or classical photomultiplier tubes.

Upon receiving the signal generated by the scattered photon detector106, the controller108can generate an integrity indication associated to the target region112of the infrastructure10based on the received signal. The integrity indication can differ from one embodiment to another. For instance, the integrity indication may be a value representative of the number of scatter event(s) detected during a given period of time. The integrity indication can be indicative of whether the number of scatter events detected during a given period of time exceeds a given number threshold in some embodiments. It is also envisaged that the signal generated by the scattered photon detector106be processed using reference data in order to measure a dimension of the void behind the structure wall, if any. The signal generated by the scattered photon detector106may be an electrical signal (e.g., analog signal, digital signal) to be processed by a controller for instance. In some embodiments, the signal may also be visual, auditory and/or haptic, as the scattered photon detector106may be communicatively coupled to corresponding visual, auditory and/or haptic indicators which render the signal in real time.

In some embodiments, the controller108can determine a void dimension indicative of a dimension of a void16in the soil12behind the structure wall20, in which the void dimension extends along an axis of the field of view110and/or to the field of radiation120, such as shown inFIG.1A. As depicted, the handheld inspection device100is shown during inspection of a first target region112aof the infrastructure10. As shown, the void16has a dimension d which can be part of the indication of the integrity of the infrastructure10generated by the controller108. Inspection of second and third target regions112band112cwould have otherwise provided an indication that no void is present behind the structure wall20or that alternately the void dimension is null, such as shown in the graph ofFIG.2. As depicted in this figure, one can appreciate that the determined void dimensions have a limited resolution as the field of radiation of the high energy photon source and the field of view of the scatted detector are divergent. In any case, the determined void dimensions can nonetheless be used as an indication that there is some kind of void or absence of supporting material behind the structure wall20at the first target region112awhich can therefore be tagged or labeled as such for further inspection using more sophisticated devices. For instance, in some embodiments, the inspected target region is at least 20 cm2, preferably at least 40 cm2and most preferably at least 80 cm2, as measured at 10 cm from the handheld inspection device100, preferably 50 cm meter from the handheld inspection device100, and most preferably one meter or more from the handheld inspection device100.

In some embodiments, the void dimension is given by a relation equivalent to the following equation:

Z=∝-1ln⁢y⁡(z)-AC-A,(1)

where z is the void dimension, y(z) is the number of scattered photons detected by the scattered photon detector106during the period of time, ∝ denotes a constant dependent on the soil, A denotes a first reference value indicative of a signal generated by a scattered photon detector when a structure wall or similar construction is surrounded with no soil and C denotes a second reference value indicative of a signal generated by a scattered photon detector when a structure wall of similar construction is fully surrounded with soil.

Referring back toFIG.1, the portable frame102shown in this embodiment has one or more handles122to be grabbed by one or two hands of the operator. The handle122can be provided in the form of one or more straps which can be wrapped around the body or limb(s) of the operator. The handle122can be made flexible or rigid depending on the embodiment.

In the illustrated embodiment, the frame102has a base portion102aand a head portion102b. The head portion102bcomprises both the high energy photon source104and the scattered photon detector106whereas the base portion102acomprises the controller108, in this example. The base portion102aand the head portion102bcan be communicatively coupled to one another using a wired connection124, a wireless connection126or a combination of both.

As shown, the base portion102aand the head portion102bare mechanically coupled to one another using an extension pole128which can be made rigid or flexible. The extension pole128can be straight or curvilinear. In some embodiments, the extension pole128can be an articulated arm having one or more articulations along its length. Additionally or alternatively, the handheld inspection device100can have a trigger130which can simultaneously trigger the high energy photon source104and the scattered photon detector106. The trigger130can be provided for ease of use and can allow the operator to quickly notify the handheld inspection device100when it is in position and ready for a measurement to be performed. It is intended that in embodiments where the high energy photon source104is a gamma source, it cannot be triggered per se as such sources are based on a radionuclide. However, the trigger130may block the photon path or expose it depending on the activation or de-activation of the trigger130, using a shutter for instance. In embodiments where the high energy photon source104is a x-ray source, the trigger130may activate or de-activate the power supplied to the source104.

Multiple styles of head portion can be used to achieve different radiation exposure profiles, thus allowing for multiple application specific head portion designs. Optionally, the head portion102bmay also contain additional device(s). The head portion102bcan be removably attached to the rest of the handheld inspection device100. For instance, the head portion102bcan be placed with one operator's hand while the rest of the handheld inspection device100is held with other operator's hand. Such a configuration may occur when inspecting small diameter pipes where it is not convenient to have a pole mounted device. Accordingly, the extension pole128is only optional.

In some embodiments, the base portion102aencloses power cell(s), charging mechanism(s), voltage regulator(s), signal receiver(s), computational platform(s), data storage system(s), communication driver(s), and/or human interface component(s).

The power cell(s) can comprise on or more lithium polymer cells in series and/or parallel configuration; however, it may also consist of other primary or secondary type power cells. Additional protection such as current flow diodes, fuses, positive temperature coefficient devices, or circuit breakers may also be used in series with the battery cells. In some cases, power can be acquired via the charging connector or by means of some other off board connection.

The charging input can comprise a standard USB port, which can double as a data communication channel if required, and appropriate charging electronics. The charging electronics may interface with the computational platform to provide charge level information. Advanced models may include a wireless charging system.

The voltage regulators provide the required voltage to the CPU, human interface devices, head unit, and any other peripherals requiring power. In the case of the photomultiplier tube, a voltage regulator capable of producing up 1,000 volts may be required. When such a high voltage rail is required, additional voltage calibration and circuit isolation may also be provided through mechanical interfaces or through a digital interface to the computational platform. The signal receivers can consist of any number of amplifiers, isolations devices, rectifiers, shapers, or other analog manipulation components. In some embodiments, the end product of the signal receivers is to provide a signal pattern or simple data bank which can be read by or that will trigger events within the computational platform. The information provided by the data channel(s) must convey some degree of chronological and energy information for each individual photon or a strike count for photons of a predefined energy range within a predefined time period.

The controller108can be provided as a combination of hardware and software components. The hardware components can be implemented in the form of a computing device300, an example of which is described with reference toFIG.3. Moreover, the software components of the controller can be implemented in the form of a software application.

Referring toFIG.3, the computing device300can have a processor302, a memory304, and I/O interface306. Instructions308for performing a method of inspecting an infrastructure using the handheld inspection device100ofFIG.1, including instructions for processing the signal received from the scattered photon detector106for the purpose of determining a void dimension, can be stored on the memory304and accessible by the processor302.

The processor302can be, for example, a general-purpose microprocessor or microcontroller, a digital signal processing (DSP) processor, an integrated circuit, a field programmable gate array (FPGA), a reconfigurable processor, a programmable read-only memory (PROM), or any combination thereof.

The memory304can include a suitable combination of any type of non-transitory, computer-readable memory that is located either internally or externally such as, for example, random-access memory (RAM), read-only memory (ROM), compact disc read-only memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable read-only memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like.

In some embodiments, there can be two basic options for data logging: internal and external. Internal data logging requires some form of non-volatile memory such as an SD Card. External logging requires the presence of some device attached via one of the external digital communication channels. Each embodiment has its own advantage and disadvantage. Internal data logging has the advantage of being more streamlined and reliable since there may not be any required data communication channels which can be interrupted. External data logging requires the user to have additional hardware (such as an android powered tablet) to perform the data logging for them. It does, however, have the advantage of performing computational operations on the data as it is acquired which the base unit itself is not capable of. For example, an android device can present the user with an up to date view of the pipe measurement grid so that inspection decisions can be made on the spot rather than waiting for the data to be uploaded and analyzed later on. Additionally, the cellular connectivity of the mobile platform can be leveraged to update the project data quickly allowing for decisions and directives to be made by the project manager remotely before the field crew leaves the site.

Each I/O interface306enables the computing device300to interconnect with one or more input devices, such as computer mouse(s), keyboard(s), trigger(s), scattered photon detector(s), or with one or more output devices such as a display, a memory system for storing the generated data, a communication unit for communicating the generated data to an external network.

Each I/O interface306enables the controller to communicate with other components, to exchange data with other components, to access and connect to network resources, to server applications, and perform other computing applications by connecting to a network (or multiple networks) capable of carrying data including the Internet, Ethernet, plain old telephone service (POTS) line, public switch telephone network (PSTN), integrated services digital network (ISDN), digital subscriber line (DSL), coaxial cable, fiber optics, satellite, mobile, wireless (e.g. Wi-Fi, WiMAX), SS7 signaling network, fixed line, local area network, wide area network, and others, including any combination of these.

In some embodiments, the I/O interface306can comprise external digital communication channels with a wired or wireless digital communication driver along with any necessary hardware (such as antennae or physical connection ports). Some examples of which are Bluetooth, WiFi, RS-232 Serial, USB, and NFC (Near-Field Communication). Additionally, a wired communication channel can be employed through an added connection port or through the same USB port used by the charging mechanism.

The I/O interface306can have many different types of components. Typically, a small screen and keypad will suffice. However, additional items such as an external trigger or an LED bank can also be added. Interface to the CPU can be made via GPIO (General Purpose Input/Output) lines, a centralized system bus (such as12C or some other serialized peripheral bus). It is also possible to build in a mobile platform to provide such an interface (such as an Android powered platform). In the case of remote operation, such interfaces can be omitted in favor of a remote-control system via one or more of the digital communication channels.

The computing device300described above is meant to be an example only. Other suitable embodiments of the controller can also be provided, as it will be apparent to the skilled reader.

Reference is now made toFIG.4which illustrates a flow chart of a method400of inspecting an infrastructure having a structure wall at least partially received into soil.

At step402, the high energy photon source radiates a photon beam within a field of radiation diverging towards a target region of the infrastructure. By doing so, the photon beam at least partially penetrates across the structure wall and through the soil behind the structure wall. As mentioned above, it is noted that the photon beam has a radioactivity level below a threshold radioactivity level. In some embodiments, the high energy photon source is monoenergetic in which case each radiated photon has an energy comprised within an energy bandwidth spanning no more than 50 keV, preferably no more than 20 keV and most preferably no more than 10 keV.

At step404, the scattered photon detector detects scatter events incoming from the radiated target region during a given period of time. In some embodiments, that period of time can be below 1 minute, preferably below 30 seconds and most preferably below 10 seconds, which may allow swift inspections to be performed. When the high energy photon source is monoenergetic, the scattered photon detector can have a monoenergetic detection bandwidth matched to the energy bandwidth of the high energy photon source. For instance, the monoenergetic detection bandwidth may span no more than 20 keV, preferably no more than 10 keV and most preferably no more than 10 keV, depending on the embodiment. In some embodiments, it may preferable for backscattered photons to be in the range of 100 to 200 keV however it is not necessary in some embodiments.

In some embodiments, the handheld inspection device can record the entire spectrum (e.g., from 0 to 255 keV) and log it for later consultation and/or processing. Energy filtering can thus be made later in a post-processing manner. Such post-processing can allow to change the desired energy window after the acquisition, if desired. However, recording the entire spectrum may not be necessary. If cost savings are sought, the windowing can be applied in real time by the controller and thereby only record the final count.

At step406, the scattered photon detector generates a signal indicative of the scatter events detected during the period of time.

At step408, the controller generates an integrity indication associated to the target region of the infrastructure based on the received signal. As discussed above, the steps406and408can be performed sequentially to one another during a live inspection in some embodiments. In such embodiments, an auditory, visual and/or haptic indication may be rendered in real time or quasi real time using corresponding indicators communicatively coupled to the scattered photon detector and/or to the controller. However, in some other embodiments, the step406may be performed on-site whereas the step408, and other post-processing steps, can be performed later. As such, the generated signals are stored on a memory system which is accessible by a processor for later post-processing.

At step410, the controller can determine a void dimension indicative of a dimension of a void behind the structure wall. It is envisaged that the step410is only optional and can therefore be omitted in some embodiments.

Equation (1) described above can be obtained following the reasoning described in the following paragraphs. All measurements can be made by classifying individual photons into approximate energy bins within an energy spectrum. Each measurement can result in a histogram of signal strength for each energy bin within a specific range. The range may be defined by such factors as application and isotope. For example, a Cesium 132 isotope has a strong 622 kEv photon emission. In order to isolate signals from signal scatter events located X cm from the detector face with the source—detector distance also at X cm, the Compton energy shift formula can be used to calculate the energy range that needs to be examined given the initial energy source (e.g., 622 kEv) and/or the scatter angle. In some embodiments, the scatter angle may be 135 degrees. However, it is intended that the actual scatter angle can vary depending on the design of the head portion and on the location of the supporting material (e.g., soil) and/or of the wall structure. Note that the energy distribution may be used to calculate the most likely scatter angle and, therefore, help find the structure wall for inspection purposes.

The first stage of data processing can be to select an energy range of interest and compute the total number of counts within that range. This can be done by integrating the histogram data set for each measurement from the lower energy bounds to the upper energy bounds.

∑i=L⁢ower⁢Energy⁢BountU⁢pper⁢Energy⁢Bount⁢S⁢i⁢g⁡(i),(2)

where Sig (i) is the signal at energy i.

The count value can be used to determine the certainty by using a Poisson distribution or, if the count is high enough, a normal approximation. The primary unit to analyze is the normalized CPS (Counts per Second) value.

∑i=L⁢ower⁢Energy⁢BountU⁢pper⁢Energy⁢Bount⁢S⁢i⁢g⁡(i)/Time(i);(3)

where Sig(i) is the signal at energy i and Time(i) is the amount of time spent measuring Sig(i).

The above sums can be performed for each measurement resulting in a CPS and count value for each measurement taken. These values will be referred to as CPSiand Countiwhere i is the measurement enumeration ranging from 0 to n−1 where n is the total number of measurements that are performed by the handheld inspection device.

In the Insight Lite application, one can sought to determine which location in the pipe (as represented by a single measurement) should be prioritized for follow up using additional inspection methods such as BCT. Such areas can be identified by the lack of material behind the culvert wall. This lack of material, or “voiding”, can present the incoming photons with less material for Compton scattering within the required depth given by the energy range chosen in the first stage of processing. The lowered probability of Compton scatter results in a lower probability of photons being directed back to the detection volume and a lower CPS value.

The exact CPS threshold to determine voided area can depend on many factors such as source strength, detector efficiency, measurement integrity, culvert wall thickness, and/or backfill type. Furthermore, one must determine how much void is an issue for the asset under inspection. For instance, a threshold may have to be determined depending on the type of supporting material behind the structure wall, and/or the type of structure wall that is to be inspected. A simple comparison of measurements within a full data set (e.g., a collection of measurements along an entire asset) can be used by taking the all measurements lower than the mean value to prioritize inspection points, however this assumes that there exists flaws within the asset significant enough to create a range that extends from “unhealthy” to “healthy.” This may not always be the case. If a pipe were to be in excellent conditions, this method will yield a set of inspection points at roughly half of the total number of inspection points, distributed randomly along the pipe due to the variability and noise present within each measurement placing them evenly above and below the mean.

A second method can include the measurement of a known good point and a known bad point. Each measurement can be classified relative to their proximity to the known good and known bad points. A challenge with this method is that the size of the void may not scale linearly with CPS value. For example, a 2 mm void may present a significantly smaller CPS value than a 1 mm void, however a 6 mm void may be indistinguishable from a 10 mm void.

It is ultimately desirable for each measurement to be translated to a void size. This cannot be directly calculated using the measured values since each incremental unit of void effects the CPS value nonlinearly along the depth axis of the measurement. However, since the incremental increases in voids beyond a certain point becomes trivial, one can create a fair trade off by calculating an “Equivalent Soil Loss” or ESL. The ESL value can represent the size of the void along the depth axis assuming it is present immediately behind the culvert wall, for instance in a the worst-case scenario. The ESL conversion represents the second processing stage.

Through simple physical modeling, the backscatter computations for a void which increases behind a metal wall (of fixed gauge) can be generalized as follows:
y(z)=A+(C−A)e∝z(4)

y(z) represents the CPS value expected given a void measurement (z) made on the depth axis starting immediately behind the metal wall. A represents the expected CPS value with no fill present. This can be found experimentally by performing a single measurement with only a representative metal plate against the detection surface. The measured value represents a baseline that accounts for such values as noise, leakage, multiple scattering through the plate, and the scatter through open air. C represents a value indicative of the signal with optimal fill (no voids). Both A and C can be measured directly from prebuilt calibration blocks at the beginning of each scan. In some embodiments, A and C can be measured on site by inspecting reference structure wall portions that are either known to have void therebehind or known be satisfactorily buried into soil. In some embodiments A and C can be fetched from a memory system accessible by the controller. α represents a system constant dependent on the supporting material. In our case the supporting material varies little from site to site and can be found experimentally using the following equation:

∝=Z-1⁢ln⁢y⁡(z)-AC-A(5)

Lab experiments using multiple void sizes and metal plate thicknesses have shown this constant in the vicinity of:
∝=−0.23 cm−1(6)

A slight variation of the above equation can be used to calculate Equivalent Soil Loss given a measurement value as follows:

Z=-0.23cm-1⁢ln⁢y⁡(z)-AC-A(7)

Assuming that α is calculated to sufficient accuracy, it can be omitted from any error calculations. Error calculations can be drawn from the two values calculated in the first phase of the data processing; counts and time. The counts for a backscatter system following a Poisson statistical distribution. The measurement device can be programmed such that each measurement requires a minimum number of counts before completing. This number should be of sufficient quantity to allow for a Gaussian approximation to the Poisson distribution. As a result of the normal distribution, one can utilize something called ‘confidence intervals’ to calculate the error.

A third method can be to calculate the number of standard deviations that each measurement falls from a standard measurement indicative of a healthy measurement. The baseline measurement would still need to be computed for each pipe in order to consider all variations present from site to site in these embodiments.

FIG.5shows an example of a handheld inspection device500. As depicted, the handheld inspection device500has a portable frame502to which are mounted a high energy photon source504and a scattered photon detector506. As discussed above, the high energy photon source504has a divergent field of radiation510along which is radiated a photon beam514with a radioactivity level below a threshold radioactivity level. The threshold radioactivity level can differ from one embodiment to another. The scattered photon detector506has a divergent field of view520encompassing at least a portion of the divergent field of radiation510of the high energy photon source504. As shown, the scattered photon detector506detects scatter events incoming from a target region512during a given period of time, and generates a signal indicative of scatter events detected during that period of time.

In this example, the frame502has a head portion102benclosing the high energy photon source504and the scattered photon detector506, and a base portion102aenclosing a controller508. In this example, the controller508has a user interface comprising a keyboard, a first type of visual indicator along with a second type of visual indicator. A communication and/or power supply port534is also provided.

In some embodiments, the frame502has an extension pole528to which the head portion102b, i.e., the high energy photon source504and the scattered photon detector506, is mounted. The frame has a handle522which is in this case provided as an end of the extension pole528. Gripping material may cover that end for enhancing the grip of an operator's hand. As depicted, a trigger530is provided proximate to the handle522. In this way, the operator can conveniently trigger on or off the measurements by toggling the trigger530.

FIG.6shows an example of scatter events detected by the scattered photon detector506following radiation of the photon beam514across the target region512. In this example, the scattered photon detector506is polyenergetic as it detects, records and logs scattered photons distributed across a range of energy levels. In this specific example, the controller508may receive signal(s) from the scattered photon detector506and generate an integrity indication associated to the target region512based on the received signal. In some embodiments, it may be preferable to record and log the scattered photons of all energy level, as shown per the raw data curve A. The controller508may post-process the raw data by filtering the raw data, e.g., by passing it through a low pass filter such as shown by low pass filtered curve B. The controller508may then count the strikes in one or more energy band(s) of interest, e.g., usually from 100 to around 180 keV, depending on the application. Afterwards, the integrity indication can be provided in the form of an integrity map using the raw and/or filtered data.

FIG.7shows an example of an integrity map comprising integrity indicators as a function of spatial coordinates matched to spatial coordinates of the pipe that was inspected using the handheld inspection device500. The determined integrity indicator can be compared to a corresponding threshold for mapping purposes. As shown, colored areas show target regions of unsatisfactory integrity whereas white or paler areas show target regions having a satisfactory integrity. As can be understood, the raw data may be stored for a given period of time as other useful ways to process the raw data, and more specifically the spectral distribution of the detected scattered photons may appear. For instance, analyzing not only the absolute count within a certain energy window, but the distribution of the count as well, as it may yield satisfactory integrity indicators.

As can be understood, the examples described above and illustrated are intended to be exemplary only. The scope is indicated by the appended claims.