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Lifting the nuclear load

August 24, 2016

Safety is always the nuclear power industry’s top priority and cranes are essential to achieving this goal. What does it take to operate in such a sensitive environment?

What’s the first thing that comes to mind when you think of nuclear power? Maybe a recent news story or debate about the future of energy? It’s almost certain that images of cranes don’t spring to mind when the word “nuclear” is mentioned, so prepare to be surprised. Cranes are, in fact, vital to the nuclear power industry.

To the casual observer, the significance of cranes to the nuclear power industry is far from obvious. The history of cranes in nuclear power, however, is almost as old as the industry itself. Steve Waisanen, Vice President, Head of Nuclear Business Globally at Konecranes, puts it succinctly: “If nuclear power plants did not have cranes and hoists, they would not be able to perform the services necessary to keep the plant operational.”

Cranes are crucial

Just what is it that makes cranes so important to nuclear power? The answer is twofold: First, cranes are essential to the construction of nuclear facilities, where heavy-duty cranes are needed to lift components, such as reactor pressure vessels and steam generators, typically weighing more than 300 tons. Second, much of the work carried out inside nuclear power plants relies on material handling equipment.

Waisanen expands upon this: “There are literally thousands of pieces of lifting equipment inside a nuclear power plant. A short list would include reactor cranes, fuel handling machines, spent fuel cask cranes, cask transporters, radioactive waste handling cranes, hot cell cranes, turbine hall cranes, diesel building cranes, intake pump cranes, and general maintenance cranes.”

This plethora of equipment carries out the broadest range of functions within nuclear plants. For example, reactor cranes both remove and install reactor heads during plant outages; fuel handling machines load, offload, and shuffle the fuel in the reactor’s core; and spent fuel cask cranes are used to remove casks to areas where they can be transported to temporary or longer-term storage.

Safety everywhere, all the time

All of these tasks are of the utmost importance to the safety and efficiency of nuclear power plants. And that word “safety” is one that crops up with reassuring frequency.

“Safety is the number one priority in the nuclear industry and ALARA (As Low As Reasonably Achievable) is the goal the industry strives to achieve. This refers to the dose of nuclear material workers are exposed to inside a nuclear facility,” continues Waisanen. Lifting equipment plays an integral part in this goal.

“Quality is of the utmost importance as it relates to the equipment supplied to a plant. Often times, there is a misconception that because the equipment is not sitting in the reactor building, then nothing special is required of it. This is just not true. Nuclear plants have one quality system and one culture, footed to the highest level of safety and the lowest possibility of a safety problem.”

Central to this is the concept of the single failure proof (SFP) crane. Put simply, this means that cranes involved in handling nuclear materials must be designed and equipped in such a way that the single failure of any part or component will not result in a system failure, thereby causing a crane’s critical load to drop or move uncontrollably. The US Nuclear Regulatory Commission defines a critical load as “any lifted load whose uncontrolled movement or release could adversely affect any safety-related system when such a system is required for unit safety or could result in potential off-site exposure to radiation in excess of the limit determined by the purchaser.”

Needless to say, preventing failure is of the highest importance when carrying critical loads, something that Waisanen is quick to point out. “In some countries, loads such as high level radioactive waste or the reactor head require that the crane be rated single failure proof. There may be safety systems in the floor of the plant; if a load were to drop on these areas, the safety system could be damaged or radiation released. In either case, the plant would have to shut down.”

SFP cranes are not just designed to handle the maximum critical load – in many cases, they can handle  more than that. For example, wear and tear on components can be minimized by a load capacity that is designed to handle more than 10%–15% of the maximum critical load; this also enables the crane to sustain load-handling capabilities for longer periods of time.

Konecranes was heavily involved in the original development of SFP cranes, and this history of safety-oriented lifting has some unexpected cosmic origins. “Innovations were born by providing material handling equipment to the space industry. Some of our first single failure proof features were invented for the cranes that built and assembled rockets used by NASA,” shares Waisanen.

Additional safety features help prevent failure

Compared to general industry cranes, SFP cranes have a significant number of redundant components built into their lifting systems, in an effort to minimize the impact of a single failure incident. But that is not all that separates the cranes used inside nuclear plants from their non-nuclear cousins. For example, the engineering standards of nuclear cranes exceed those required for general cranes; structural systems must be more robust and must pass exacting quality control standards; and further analysis is conducted to make sure the cranes can withstand extreme stress, such as that exerted by an earthquake.

SFP cranes also feature additional systems that are increasingly found in newer industrial cranes, such as load location monitoring, visible location confirmation, and very low speed (or creep) capability. Another area of growing convergence between general industrial cranes and those used in handling nuclear materials is that of special lifting devices. Inside nuclear facilities, these lifting devices can be capable of carrying loads weighing more than 5 tons. Specially designed lifting rigs can also be found in areas where repetitive lifting actions are a frequent requirement.

One of the biggest differences between crane actions inside a nuclear facility and more general crane actions is the rigorous implementation of safe load paths. While it is standard practice in the construction industry to sketch out an intended load path with duly noted hazards, inside nuclear facilities, the load path must be explicitly prescribed for every single lifting activity. In some cases, electrical or mechanical interlocks may prevent the crane from operating near any potential hazards, such as powerlines, and collision monitoring is paramount.

Some of the above requirements may be considered excessive in general construction; but inside the impeccably planned world of nuclear material handling, these requirements are essential to safety.

Nuclear: the original green power?

As is clear, nuclear power is an industry that cannot function properly without the correct lifting equipment: let’s take a look at the current state of the industry and its future prospects.

In the wake of the 2015 UN Climate Change Conference, in which 195 countries agreed upon the urgent need to reduce climate emissions in order to limit the rise of global temperatures to below 2°C, the search for clean power sources that can aid in this goal has never been more salient. This leads to the question – what role can nuclear power play in mitigating climate change?

Tuomo Huttunen, Adviser, Power Generation at Finnish Energy, is clear on this point. “Nuclear power is a vital tool. It answers the energy trilemma –sustainability, security of supply, affordability – and is direly needed in combating climate change,” he says.

Renewable sources of energy, such as solar power and hydroelectricity, are sometimes posited as alternatives to nuclear power, but Huttunen takes another view. “Solar and wind will have a growing share in power production, but they alone cannot replace fossil fuels. All low carbon sources are needed, especially in light of the instability and inefficiency of current renewables. There is no one solution for all situations.”

The events of Fukushima had an undeniable impact on the growth of nuclear power worldwide, resulting in a somewhat mixed picture in Europe. Germany is gradually phasing out nuclear reactors and France is scaling back; whereas Finland’s four reactors provided 30% of its electricity in 2015, and a fifth reactor is under construction, with another planned.

Huttunen underlines the lessons learned from Fukushima. “Safety in nuclear power is something that is continually improving. Especially since Fukushima and the subsequent stress tests, new safety measures have been implemented in existing plants.”

There are also signs of robust growth: China, spurred by the need to cut carbon emissions, plans to triple its nuclear generating capacity by 2020 and increase it five-fold by 2050, making it the world’s largest nuclear nation. Other important markets include South Korea and India.

“Nuclear power is low carbon, weather-independent, reliable, and the cost is affordable and predictable. Nuclear is needed now more than ever,” Huttunen summarizes.

Maintenance and modernization

Unsurprisingly, the lifting equipment found inside nuclear plants requires constant care. As Waisanen explains, “One of Konecranes’ businesses involves maintenance and modernization at nuclear facilities. The requirements for this work can be more stringent than in some other industries. There are security requirements and safety training that must be completed to gain access to the plant site.”

Waisanen is emphatic when asked about the importance of crane modernizations inside nuclear facilities. “Modernizing existing equipment is one focus. Many of the cranes and hoists in plants are either at the end of their life or no longer meet new regulatory requirements and must be replaced or upgraded. Upgrades are also needed due to obsolete components.”

Despite the various differences in nuclear regulations around the globe, the aim is always the same: safety above all else. “No matter where you are, once you enter a nuclear facility, the expectation is the same. The codes and requirements might be different, but there is only one quality mentality.”

 

Text: Daniel Penfold
Photos: Konecranes, Getty Images, Shutterstock

 

3 Facts

  • Nuclear energy produces more than 63% of all US emission-free electricity.
  • Globally, over the period 1996-2015, 66 nuclear reactors were retired and 71 became operational.
  • A single uranium pellet produces the same amount of energy as 474 liters of oil – enough electricity to power an average household for up to four months without producing carbon emissions.