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)