Ripping out a reactor’s heart: radiation, risk and robots
About 200 nuclear reactors around the world will be shut down over the next quarter century
As head of the Muelheim-Kaerlich nuclear reactor, Thomas Volmar spends his days plotting how to tear down his workplace. The best way to do that, he says, is to cut out humans.
About 200 nuclear reactors around the world will be shut down over the next quarter century, mostly in Europe, according to the International Energy Agency. That means a lot of work for the half a dozen companies that specialise in the massively complex and dangerous job of dismantling plants.
Those firms – including Areva, Rosatom’s Nukem Technologies Engineering Services, and Toshiba’s Westinghouse – are increasingly turning away from humans to do this work and instead deploying robots and other new technologies.
That is transforming an industry that until now has mainly relied on electric saws, with the most rapid advances being made in the highly technical area of dismantling a reactor’s core – the super-radioactive heart of the plant where the nuclear reactions take place.
The transformation of the sector is an engineering one, but companies are also looking to the new technology to cut time and costs in a competitive sector with slim margins.
Dismantling a nuclear power plant can take decades and cost up to 1 billion euros, depending on its size and age. The cost of taking apart the plant in Muelheim-Kaerlich will be about 800 million euros, according to sources familiar with the station’s economics.
Some inroads have already been made: a programmable robot arm developed by Areva has reduced the time it takes to dismantle some of the most contaminated components of a plant by 20-30 percent compared with conventional cutting techniques.
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For Areva and rival Westinghouse, reactor dismantling is unlikely to make an impact on the dire financial straits they are mired in at present as it represents just a small part of their businesses, which are dominated by plant-building.
But it nonetheless represents a rare area of revenue growth; the global market for decommissioning services is expected to nearly double to $8.6 billion by 2021, from $4.8 billion last year, according to research firm MarketsandMarkets. Such growth could prove important for the two companies should they weather their current difficulties.
“We’re not talking about the kind of margins Apple is making on its iPhone,” said Thomas Eichhorn, head of Areva’s German dismantling activities. “But it’s a business with a long-term perspective.”
When reactors were built in the 1970s, they were designed to keep radiation contained inside at all costs, with little thought given to those who might be tearing them down more than 40 years later.
First, engineers need to remove the spent nuclear fuel rods stored in reactor buildings – but only after they’ve cooled off. At Muelheim-Kaerlich this took about two years in total. Then peripheral equipment such as turbines need to be removed, a stage Muelheim-Kaerlich has begun and which can take several years.
Finally, the reactor itself needs to be taken apart and the buildings demolished, which takes about a decade. Some of the most highly contaminated components are cocooned in concrete and placed in iron containers that will be buried deep underground at some point.
While the more mundane tasks, including bringing down the plants’ outer walls, are left to construction groups such as Hochtief, it’s the dismantling of the reactor’s core where more advanced skills matter — and where the use of technology has advanced most in recent years.
Enter companies such as Areva, Westinghouse, Nukem Technologies, GE Hitachi as well as GNS, owned by Germany’s four nuclear plant operators. They have all begun using robots and software to navigate their way into the reactor core, or pressure vessel.
“The most difficult task is the dismantling of the reactor pressure vessel, where the remaining radioactivity is highest,” said Volmar, who took charge of the RWE-owned Muelheim-Kaerlich plant two years ago. “We leave this to a specialised expert firm.”
The vessel — which can be as high as 13 metres and weigh up to 700 tonnes — is hidden deep inside the containment building that is shaped like a sphere to ensure its 30-centimetre thick steel wall is evenly strained in case of an explosion.
The 2011 Fukushima disaster and the Chernobyl accident of 1986 are imprinted in the world’s consciousness as examples of the catastrophic consequences of the leakage of radioactive material.
France’s Areva recently won the contract to dismantle the pressure vessel internals at Vattenfall’s 806 megawatt (MW) Brunsbuettel nuclear plant in Germany, which includes an option for the Swedish utility’s 1,402 MW Kruemmel site.
There, the group will for the first time use its new AZURo programmable robot arm. It hopes this will help it outstrip rivals in what is the world’s largest dismantling market following Germany’s decision to close all its last nuclear plants by 2022, in response to the Fukushima disaster.
AZURo operates under water because the liquid absorbs radiation from the vessel components — reducing the risk of leakage and contamination of the surrounding area. The chamber is flooded before its work begins.
Areva’s German unit invests about 5 percent of its annual sales, or about 40 million euros, in research and development, including in-house innovation such as AZURo. By comparison, the world’s 1,000 largest corporate R&D spenders, on average, spent 4.2 percent last year, according to PwC.
The robot arm technology helped Areva beat Westinghouse by winning tenders to dismantle pressure vessel internals at EnBW’s Philippsburg 2 and Gundremmingen 2 blocks, industry sources familiar with the matter said.
Areva and EnBW both declined to comment. Westinghouse — whose US business filed for bankruptcy in March — did not respond to repeated requests for comment.
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Britain’s OC Robotics has built the LaserSnake2, a flexible 4.5-metre snake arm, which can operate in difficult spaces and uses a laser to increase cutting speeds — thus reducing the risk of atmospheric contamination. It was tested at the Sellafield nuclear site in west Cumbria last year.
This followed France’s Alternative Energies and Atomic Energy Commission (CEA), whose laser-based dismantling technology generates fewer radioactive aerosols — a key problem during cutting — than other technologies.
The complexity of the dismantling process is also giving rise to modelling software that maps out the different levels of radiation on plant parts, making it easier to calculate the most efficient sequence of dismantling – the more contaminated parts are typically dealt with first — and gives clarity over what safety containers will be needed to store various components.
GNS, which is jointly owned by E.ON, RWE, EnBW and Vattenfall, is currently helping to dismantle the German Neckarwestheim 1 and Philippsburg 1 reactors, using its software to plan the demolition.
The company also hopes to supply its software services for the dismantling of PreussenElektra’s Isar 1 reactor, which is being tendered, and aims to expand to other European countries.
“Two things matter: time and money,” said Joerg Viermann, head of sales of waste management activities at GNS. “The less I have to cut, the sooner I will be done and the less I will spend.”