Borescope inspections are vital to help ensure the safety, reliability, and regulatory compliance of nuclear power plants. These inspections are key to preventive maintenance, root cause analysis, and maintaining operational efficiency. However, for those carrying out boroscope inspections there is the potential for radiation exposure. Minimizing any exposure for inspectors in nuclear plants is critical to protect their health, ensure compliance with regulations, and facilitate safe and effective inspections and maintenance activities.
For example, the Nuclear Regulatory Commission (NRC), the key US nuclear regulatory body, imposes stringent guidelines to monitor and regulate nuclear facilities. They ensure compliance with safety protocols to minimise potential risks associated with nuclear materials and radiation. Workplace radiation exposure is meticulously regulated in accordance with these safety standards, and the annual effective dose limit is established at 5 rem (0.05 sievert (Sv)).
To provide context, the average person typically encounters less than 0.003 Sv of naturally occurring radiation annually. Workers in nuclear plants generally experience exposure levels of less than 0.01 Sv per year, a threshold deemed reasonably safe by prevailing standards. Adhering to these guidelines ensures a controlled and secure environment for individuals operating in nuclear facilities.
Another fundamental approach to radiation safety is the ALARA principle, which stands for “as low as reasonably achievable.” It emphasises the need to minimise radiation exposure to the lowest achievable levels without compromising the efficiency of plant operations.
This principle requires continuous vigilance, employing advanced technologies, and optimizing work procedures to keep radiation doses well below established limits. Remote visual inspection (RVI) technology has continued to evolve and provide a safer alternative for personnel to make their inspections from a sufficient distance to help decrease their annual effective dose level.
A safer way to inspect nuclear plants
When critical inspections at nuclear plants reveal suspected corrosion or blocked conduits or vessels in the containment area, they must be handled immediately to help avoid accidental radiation leakage. In some cases, the reactor may need to be shut down so that workers outfitted in full-body protective gear can perform the inspection.
Remote visual inspection using video borescopes offers a safer and more efficient alternative to this method. It helps avoid costly shutdowns, saves time and operational costs, and reduces the risk of a harmful radiation dose for workers.
Industrial video borescopes are advanced inspection tools that enable inspectors to perform visual observations remotely via external camera-based equipment.
In this remote visual inspection, the video borescope’s insertion tubes are used to access the target area. The video technology on the borescope lets the inspector analyse the area from a distance through a monitor. Inspectors can view image data in real time on the screen and record it for further assessment, analysis, and reporting.
Navigating nuclear inspection challenges
Advanced video borescope systems offer inspectors the ability to quickly identify issues. This aids in faster decision-making and targeted maintenance. The captured video and images are valuable documentation for reporting, supporting thorough inspections that comply with regulations.
In addition, durable and manoeuvrable insertion tubes can easily navigate complex structures within the plant. Video borescopes come with different configuration options and multiple insertion tube diameters and lengths to adapt to varying and challenging inspection conditions.
Time and distance are important factors for determining inspection conditions. Video borescopes equipped with a long insertion tube enable the visual inspection of difficult-to-access locations, such as water conduits. The longer the insertion tube, the farther away the inspectors can be from the radiation. The reactor vessel contains components crucial to the plant’s operation. However, accessing these areas can be challenging due to high radiation levels.
Video borescopes are used to visually inspect the reactor vessel internals on a regular basis. Typical inspection areas include the core shroud, control rod drive mechanisms, and other critical elements in the non-nuclear balance of plant such as the steam generators and condensers. Inspectors can navigate the borescope remotely, capturing real-time video and images to assess the condition of these components without direct human entry into the high-radiation environment.
Unfortunately, even the best video borescope equipment does not come out completely unscathed when exposed to radiation. If the insertion tube is used to inspect dirty-water-filled pipes, contamination is inevitable, and damage is also a possibility. When the equipment is used in high-radiation areas, in some instances, decontaminating the equipment may be considered too costly and risky for the health of the workers. The plant may opt to sacrifice the insertion tube, leaving it permanently in the radiation area.
Regardless, the insertion tube and the video borescope need to be robust enough to satisfy the requirements and expectations of the nuclear plant’s safety inspection and maintenance programs.
Borescope capabilities for nuclear plants
Advanced video borescopes have features that enable them to survive longer in radiation areas. The following video borescope capabilities are helpful for navigating the challenging inspection environment of nuclear power
plants while improving user efficiency, worker safety, and equipment uptime.
● Resistant to radiation damage
The video borescope’s insertion tube must be tough enough so that the illumination and image sensor still work even after being exposed to a significant amount of radiation, such as 1,400 Gy (a unit that measures an absorbed radiation dose). A particularly beneficial feature to prolong the life of your borescope is an LED illuminated optical tip adapter. This adapter type eliminates the need to use optical fibers that can yellow when exposed to radiation. Ultimately, the insertion tube should withstand many times more radiation than the established safe limits for workers: around 140,000 times a person’s annual exposure limit of 5 rems (0.05 Sv).
● Long-distance insertion tube
Video borescopes with an extra-long insertion tube enable workers to make inspections from a safer distance. For example, a 30-meter (100-foot) tube can be fed into dirty water pipes in the radiation containment area, and workers can control and manoeuvre it from afar.
For greater flexibility and safety, use a video borescope with a wireless connection. This lets you observe live images and record still images and video on another screen, such as a tablet or PC, away from the borescope unit. Workers can keep their distance while remotely controlling the borescope.
● Replaceable insertion tubes and tip adapters
An interchangeable insertion tube can be replaced at the inspection site. This both saves time and reduces costs as the inspector can bring a spare scope and change it in the field if the original becomes contaminated with radiation. Interchangeable tip adapters (see figure 3) offer similar flexibility – if a lens is damaged, just replace the optical tip and keep inspecting.
● Optimal illumination, contrast, and exposure
Image brightness is essential to inspect the inside of a pipe or vessel from far away. A video borescope’s optical tip adapter should continuously deliver bright light regardless of the scope length. LED illumination paired with advanced image processing technology can produce bright, contrast-balanced images throughout the entire depth of field. A long exposure function can help operators find defects easily when inspecting large spaces, such as a reactor vessel.
● Compact for quick transport
To maximize worker safety, inspections in a radiation environment must be completed as quickly as possible. A compact video borescope system enables workers to quickly transport the system to an inspection site. For example, a borescope with a wheeled carrying case is easy to move, and wheel locks keep the system in place when workers are ready to inspect.
● Easy to handle for fast inspection
Another helpful feature to improve efficiency is a gravity sensor in the scope tip. This technology automatically orients the image so that you know which direction is up, reducing any confusion and speeding up the inspection (see figure 4). In addition, a guide head on the scope’s distal end makes it easier to pass smoothly through pipe elbows, further enhancing your inspection efficiency.
Nuclear Plant Construction
In addition to playing a key role in nuclear power plants’ operations, long video borescopes are an asset in the construction of these facilities.
James Steven, the quality control manager of Altrad Engineering Services, uses the IPLEX GX video borescope as an inspection tool during the construction of a new nuclear power station when delivering a mechanical, electrical and HVAC package (MEH). This unit has scope options with lengths up to 10 meters (32.8 ft).
The operators use the long video borescope to perform clear bore inspections. This is an important inspection for construction, as clearing the internal surfaces after welding helps ensure the surfaces have minimum oxidation.
Steven noted, “Carrying out inspections using this technology ensures we have met the design intent defect-free. With the IPLEX GX video borescope, we can accurately measure the sizes of defects. We use this technology as an activity in all of our documentation.”
When choosing a video borescope for the task, Steven looked for a model with a long articulated insertion tube and excellent after-sales service, including local training support. Training flows down at the facility, as their fully trained operators can train other operators on the inspection team for greater efficiency.
The use of industrial video borescopes in the construction and operation of nuclear power plants exemplifies how technological advancements can enhance inspection processes throughout the industry. These tools enable detailed, remote inspections, reducing the risk of radiation exposure and helping ensure comprehensive assessments without the need for reactor shutdowns.
Ultimately, the integration of advanced video borescopes in nuclear power plant inspections underscores a commitment to safety, regulatory adherence, and operational excellence. As these technologies continue to evolve, they will play an even more crucial role in safeguarding the future of nuclear energy.
