Nuclear power is an important source of electricity in many parts of the world. With more than 500 reactors either in operation or under construction, nuclear power accounts for about 11% of the world’s electrical power generation. Although there are environmental concerns surrounding nuclear power, nuclear electricity generation produces no atmospheric carbon dioxide; as concerns about global warming become more acute, it is likely that this method of generating electricity is going to become more prevalent.
Nuclear power works by using the heat from a controlled nuclear reaction to boil water – in essence, an atomic power plant is a giant teakettle. The steam from the boiling water turns a turbine, which generates electricity. The steam is then recaptured, allowed to condense back into liquid water, and run back through the reactor system. Many reactors also use water to cool the operating machinery of the plant itself. All of this water, of course, must be piped and conveyed and stored. The hydraulic systems of a nuclear power plant are more complicated than the actual nuclear reaction machinery itself, and contain vast amounts of water. Of course, those hydraulic systems need inspection and repair work.
Unfortunately, however, the environment of a nuclear power plant’s cooling systems tend to be unfriendly to human beings, to put it mildly. Since the water is drawn into the plant and boiled, the water that discharges from the condensing system is still very hot. Radiation levels in the coolant system, while nowhere near what they would be in the containment chamber of the reactor, can be significantly higher than the background level. Finally, the conditions in the hydraulic systems tend to be cramped and constricted. All of these things make putting human divers into a plant’s hydraulic system a really bad idea. At the same time, the exceptionally clear water conditions inside the cooling system make visibility exceptionally good.
ROVs, while not immune to radiation (electronic devices can be damaged by high levels of ionizing radiation), can handle levels of radiation that would make a human being sick or increase their cancer risk without any problems. This allows plant operators to use ROVs to inspect cooling tanks for leaks, check the walls of reservoirs, test the condition of intake pipes and storage dams, and measure water conditions in holding tanks. The use of ROVs in hazardous areas eliminates the need to put human divers at risk and also eliminates the need to dewater areas of the plant (often necessitating an expensive and time-consuming shutdown of the plant) for visual inspections.
ROVs are also of use in decommissioning nuclear plants. When a nuclear plant reaches the end of its life, there is a great deal of inspection and demolition work that must go into decontaminating the site. ROVs can be used for visual surveys of underwater structures at the site, to conduct radiometric surveys of potentially contaminated areas, and even assist in demolishing contaminated areas underwater. Tethered ROVs actually perform very well in these areas, because the umbilical connection means that the need for sophisticated electronics on the ROV is reduced – more of the sensitive electronic components are safely away from the contaminated area, in the control console or PC being used to run the ROV. Combined sonar/radiologic surveys of contaminated areas reduce the cost of the physical demolition work, as workers have a perfect map of the area and know which spots are “hot”.
As nuclear power grows more important in providing our civilization’s energy needs, ROVs will play a major role in ensuring that this form of electrical generation is safe and economical.
Nuclear Power Plant Diagram By Tennessee Valley Authority (tva.com) [Public domain], via Wikimedia Commons
An offshore windfarm is an array of power-generating wind turbines usually built in the shallow water close to the coastline. Offshore wind power has three main advantages over land-based wind power: the wind directly offshore is usually stronger and steadier than it would be inland, the windfarm can be placed very close to the urban area that will be using the power, and there is less “not-in-my-backyard” opposition from local residents, since the local residents are mainly fish. The primary disadvantage of offshore wind farms is that they are much more expensive to build and maintain than other forms of low-carbon power generation.
The European Union is by far the world leader in offshore wind generation, with about 10 gigawatts (GW) of capacity. China and Canada both have modest windfarm operations and India is working on windfarm development, while the United States will open its first operational windfarm in late 2016 off Block Island in Rhode Island. Despite the high costs of offshore wind power development, projections of installed capacity continue to grow; the European Union expects to have between 20 and 40 GW of capacity online by 2020, and China perhaps optimistically expects to have 30 GW by the same year.
The primary component of an offshore windfarm is the wind turbine - the huge set of blades set atop an enormous pole, which spin as the wind blows. To achieve maximum effect, turbines need to be high off the surface of the water, so the pole must be very long - more than 200 meters.
Such a large structure must be anchored extremely securely to the seabed, and there are a number of ways in which this is done. Regardless of the exact nature of the structural engineering, the underwater structures of offshore wind turbines need to be inspected on a regular basis.
In the United States, offshore windfarm inspections will be under the oversight of the Department of the Interior’s Bureau of Safety and Environmental Enforcement (BSEE). BSEE’s draft standards draw heavily on the experience of the United Kingdom, and lay out an inspection regime that concentrates a great deal of attention on the turbines themselves, naturally enough. However, the underwater bases of the turbines come in for their share of attention as well.
BSEE draft standards will likely require that windfarms be inspected on an annual basis, with 20% of a farm’s individual turbines and foundations inspected in each annual cycle. Critical components should be evaluated annually, while less critical areas can be inspected as infrequently as every five years. Foundations need to be checked for structural health, bioaccumulation, scouring, spalling, and corrosion. Subsea cables need to be inspected for damage due to sand, marine animals, or anchoring.
BSEE suggests that general visual inspections can be carried out by ROVs, while close visual inspections need to be done by human divers.
BSEE standards are likely to recommend the use of ROVs specifically in order to reduce risks to human divers. Because there are often powerful tidal currents around the foundations of structures like wind turbine foundations, this can be a dangerous dive environment for humans. There is a great deal of general visual inspection work that needs to be done, but where an extremely close view is simply not required; the inspection needs to check the general condition of the pilings and caissons, for example. In this work, putting a human diver into the water isn’t necessary, as an ROV can provide the needed visual check.
(Primary source: http://www.bsee.gov/uploadedFiles/BSEE/Technology_and_Research/Technology_Assessment_Programs/Reports/700-799/747AA.pdf)
There are almost 80,000 dams in the US Army Corps of Engineers National Inventory of Dams (NID), and that isn’t even a comprehensive list; the NID only covers dams which reach a minimum height and which hold back a minimum volume of water. There are many thousands of other dams, on private and government land, which are used for irrigation, flood control, aquaculture, drinking water, industrial use, and a myriad of other applications. Although most of these dams are extremely useful, they can also pose a serious danger to people and objects downstream of the dam. For obvious reasons, dam failure can have catastrophic consequences.
Accordingly, it is critically important that dams be inspected on a regular basis.
The federal government, via the Federal Emergency Management Agency (FEMA), provides guidelines for inspections on dams under federal control. These guidelines suggest that dams should receive an informal “eyes-on” inspection as needed or following any significant incident at a dam (such as a flood, an earthquake, or vandalism), as well as a more thorough intermediate inspection of the dam and all related structures on an annual basis. Federal guidelines also suggest a formal full inspection of the dam be carried out at least every five years, with a full special inspection to be conducted when there is a major event such as a large flood or a major earthquake. Around 3,200 dams in the United States are owned outright by the federal government, and another 5,200 or so are not owned by the government but are located on government land. Although there are some complications about the regulation of those non-federally-owned dams, all told about 10% of the largest American dams fall under the federal guidelines.
The remainder of the dams in the United States are regulated by the state governments, with the notable exception of Alabama which leaves dams essentially unregulated. The state laws and regulations are a fairly diverse patchwork; some states require inspections to be paid for by the dam owners, while other states put that expense on the taxpayer. A few states like Texas do not have a formal inspection schedule at all (although inspections are strongly suggested) while most states have stringent schedules and extensive systems of classifications for which kinds of dams must be inspected and how often.
In general, however, in most places, dams are supposed to be inspected at intervals ranging from annually to every five years. The size of the dam’s impoundment (the volume of water the dam is holding back) and the population of the area in the dam’s potential flood area are the major factors determining how often and how stringent such inspections must be. Again depending on the location, inspections can be carried out by divers or by surface inspection, usually with at least some underwater work being required. Clearly, there is an astonishingly large amount of inspection work called for in the dam safety regulations.
ROVs play a major role in accomplishing the difficult task of inspecting dams while leaving them in service. Many dams are simply not able to be “turned off” so that an inspection can take place. Even when dams are equipped with the ability to dewater areas for inspection or repair, such dewatering is time-consuming and expensive. ROVs and human divers are able to work in areas of the dam without having to go through the dewatering process, saving large amounts of money.
One area where ROVs have saved enormous sums for dam owners is in assessing the need for cleaning of trashracks, reservoirs, and head ponds.
Rather than adhering to a calendar schedule for the dredging of such ancillary dam components, an ROV inspection using sonar can inexpensively check whether an area needs to be dredged at all.
Of even more importance than saving money is saving lives. At many dams, particularly hydropower dams, there are areas where it is very dangerous for a human diver to enter the water. High water flows and high pressure differentials can be life-threatening conditions. The use of an ROV allows dive teams to conduct preliminary safety assessments, measuring flow, depth, and water temperature before ever putting a human being into the water. ROVs have also been used to check safety concerns such as the open or closed status of a head gate, where a gap of a few inches in a nominally “closed” gate could pose a lethal risk to a diver in the area.
At large dams with deep water areas, ROVs have the ability to work deeper than human divers without needing mixed-gas equipment. (Divers going below 30 meters require decompression tanks and other specialized equipment that make a dive more expensive.) By using divers for shallow work at a dam, and ROVs for the deeper dives, a cleaning or inspection process can be accomplished at much less expense. In addition, ROVs can conduct survey work using tools such as multibeam sonar more efficiently than human dive teams. As dam infrastructure ages, inspections of components like downstream draft tube slabs require a great deal of precise surveying work to assess the condition of the slab.
As in many other areas of underwater work, ROVs are capable of making a large contribution to the jobs being done by human divers.
ROVs make underwater work safer, more effective, and less expensive.
The Aquabotix HydroView and Endura remote-operated vehicle (ROV) family have any number of terrific features that set them apart from the competition. Among the most compelling of those features are those which make the Aquabotix ROVs extremely easy to use. The ability to control a full-featured ROV using a gamepad controller, an iPad, or a laptop, and the company’s commitment to the 3-3-3 learning curve model (three minutes to get into the water, three hours to learn how to drive, three days to mastery) makes learning to use the vehicles very simple.
Aquabotix is now expanding that ease of use with the development of a new self-diagnostics panel on all ROV software. The self-diagnostic panel helps even the most inexperienced users quickly identify and fix any problems that may hold up the deployment of an Aquabotix ROV. The diagnostics panel can be called up on the iPad or laptop being used to run the Aquabotix software by clicking on the ‘Diagnostics’ icon at the right side of the bottom control panel.
The self-diagnostic panel has four major elements. At the top is the System Overview, a graphical representation of the entire chain of communication from the controlling PC to the ROV itself. At the bottom left is the App pane, with information about the controlling PC. In the bottom center is the Network Statistics pane, and at the bottom right we find the Vehicle Information pane. We’ll take a quick look at each of these elements.
The System Overview panel provides an at-a-glance status report on the communication and control path between the controlling PC and the ROV. This pane gives a graphic representation of the status of your PC, your PC’s connection to its own network, the topside box which interfaces between your PC network and the ROV, the wired connection between the topside box and the ROV, and the ROV itself. These status displays are simplified to a green check (all is well), a red ‘X’ (something is not working), and a yellow ‘!’ (there is some important piece of information relating to this element of the system which you need to see). Looking at this panel gives the user a quick assessment of the system status when things are working properly, and an exact idea of where the problem is when they are not.
The other sections of the self-diagnostic panel provide useful information for drilling down deeper into any problems that arise. The App pane gives some basic information about your PC, including the current software version, whether your PC is supported by the Aquabotix software, whether a gamepad controller is connected, and how your local video performance is holding up. The Network Statistics pane tells you the health of the network connections to the topside box, alerting you to any latency issues, and also gives statistics on the health of the video feed from the ROV. Finally, the Vehicle Information pane tells you the current date and time, the vehicle’s current uptime, the time of the last shutdown, and information about the vehicle version.
Using the self-diagnostics panel in the Aquabotix software package allows even beginning ROV users to quickly identify the source of any problems with their ROV deployment, making it even quicker and easier to get into the water and get to work.