Our Future Nuclear Challenge: Decommissioning Plants

By Catherine
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By Catherine Bolgar

Nuclear power plants last a long time, but not forever. Around the world, 158 nuclear reactors have been permanently shut down, although only 15 have been fully decommissioned, or dismantled. The U.S., which has by far the most nuclear facilities, has decommissioned 10 commercial reactors and has 18 others going through that process. Germany decided in 2011 to phase out nuclear power entirely by 2022.

The question of how best to dismantle nuclear power plants will continue far into the future, considering that 60 reactors are under construction now, and that nuclear plants operate for 30-60 years.

“Our reactors had an initial design life of 30 years,” says Jerry Keto, vice president of nuclear decommissioning for Ontario Power Generation, which operates 20 of Canada’s 22 reactors. “But in operating them, we have confirmed that the plants can run much longer. Most plants in the U.S. and Canada confirm through aging-management programs that they’re fit.”

Some countries choose to dismantle and decommission their nuclear facilities immediately after shutdown. Some prefer deferred dismantling and delay the process for several years. Others choose entombment and convert theirs into waste-disposal facilities, after ensuring that the targeted end-state of the facilities is safe, according to Michael Siemann, head of the Nuclear Energy Agency’s division of radiological protection and radioactive waste management, part of the Organization for Economic Cooperation and Development (OECD).

“The choice of approach depends on many factors, some of which may be related to national circumstances,” Dr. Siemann says. “Nevertheless, immediate decommissioning is usually considered as the preferred strategy, meaning that the shutdown nuclear-power plants are usually dismantled and major parts also completely removed.”

One of the challenges in decommissioning is that for “some plants designed in the 1960s and ‘70s, not a lot of attention was given to fact that somebody has to take them apart in future,” Mr. Keto says. “Now, decommissioning is entrenched in design for new construction. The new reactors being built in the United Arab Emirates were designed already thinking of how they will be dismantled in the future.”

The age of many plants means that their original designs were on paper. “The main problem is there is so little information about the state of the buildings. The plans of the plants were mostly nondigital,” says Joseph W. Dörmann, mechanical engineer at the Fraunhofer Institute for Material Flow and Logistics, in Dortmund, Germany. “While the plant was running for 30 years, there were changes to the building. It’s really difficult to have a clear 3D model of the plant. It’s difficult to find out where, for example, radiation has had an impact. You need a lot of time to develop the information, to know which part of the plant can be demolished, by which technology, and whether to bring to safehouse”—a special nuclear-waste repository—“the nuclear waste or materials that have had contact with nuclear waste.”

Rather than try to digitize paper designs, OPG makes scans of the plants, “so we’re less reliant on what the paper says and totally reliant on the real area. Especially in high-radiation fields, it’s not a place for sending workers,” Mr. Keto says, adding that digitization is needed so that machines can be programmed to do the work automatically.

Where workers are needed, OPG even builds exact replicas of the area for training and practice, so that when workers enter a radioactive zone they can get the work done in the shortest period possible. OPG hasn’t yet decommissioned full facilities, Mr. Keto says, but it has “done some very highly radioactive work in our plants. We have permanently shut down two reactors and laid them up for future dismantlement.”

Only a small part of a typical nuclear plant is highly contaminated, with slightly more low-to-medium-level waste. About 90%-95% of a nuclear plant isn’t radioactive at all and can be demolished like any other industrial building, with waste taken to landfills or recycled, Mr. Dörmann says.

The walls of such plants can be 1.5 to 2 meters thick, and even in contaminated areas only the first 2-5 centimeters may be affected, he says. New cutting techniques, cameras and robots allow the contaminated part to be removed separately.

Concrete may be blasted with dry-ice pellets rather than sand, because dry ice disappears when it melts, whereas used sand must also be disposed of as contaminated waste. Scabbling is another technique for removing a layer of concrete. Rubble is then cracked into morsels smaller than 2 millimeters.

Non-contaminated material can be recycled as sand, concrete and metal. Parts of Germany’s Jade West Port on the North Sea used materials from a demolished nuclear plant, Mr. Dörmann says, adding, “It’s a way to do recycling on a large scale.”

The steel bars reinforcing the concrete can be melted down and recycled. Metal that’s slightly contaminated is turned into shield blocks for use at other nuclear facilities.

Nuclear facilities can’t be retrofitted into conventional power plants because they aren’t built for the same levels of heat, and the turbines are different, Mr. Dörmann says. However, the office buildings and even some other facilities can be renovated for new uses. With cooling tower foundations 18-21 meters deep, keeping them and building a new facility, such as a logistics center, on top would vastly reduce the amount of rubbish, he says.

“Given the low number of only 15 completed decommissioning projects world-wide,” says the NEA’s Dr. Siemann, “it is too early to draw conclusions and to derive trends in the reuse of entire sites after decommissioning completion.”

 

 

Catherine Bolgar is a former managing editor of The Wall Street Journal Europe, now working as a freelance writer and editor with WSJ. Custom Studios in EMEA. For more from Catherine Bolgar, along with other industry experts, join the Future Realities discussion on LinkedIn.

Photos courtesy of iStock

 

3D Design in Nuclear Engineering

By Nikoloz
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ATLAS Detector CERN Dassault Systemes

ATLAS Detector, 3D version

‘Every great advance in science has issued from audacity of imagination’ – John Dewey.

Nowadays, mankind tackles new challenges within the R&D industry. One of the leading places is hold by particle physics and its ambitious project to explain phenomena of the material universe and its origins.

The European Organization for Nuclear Research is the place where people started the quest to find this explanation by constructing the Large Hadron Collider, including its large scale detectors called ATLAS and CMS (ATLAS is 45m long, 25m high, it weighs about 7,000 tons which is almost the Eiffel Tower weigh!). It required high engineering excellence in different areas, but as a major in 3D design, I want to talk about the assembly parts.

The ATLAS collaboration gathered 169 partner institutes from 37 countries with over 3,000 physicists and engineers. Quite a lot of people huh? :) Everything started by developing 3D assembly of the detector which took 10 years and consisted in 10,000,000 sub-assemblies and parts.

3D visualization made a huge impact in calculation of heat transfer for cooling, simulation of stress and dynamical 3D modeling of installation (which in reality is one of the main concerns for engineers). How to place large and complex assemblies below 100m with 50mm clearance?

To give you an idea, the video below shows you a simulation of a 220 tones End Cap Torroid installation. In reality, lifting down such a heavy baby needs a special approach, like stopping it every five meters in order to reduce and avoid its swinging, which could cause significant damage to the surrounding assemblies.

YouTube Preview Image

This is a new field of engineering activity, called nuclear engineering, and it has no major ties with the traditional auto, aerospace or ship building industries. Basic difference is, in nuclear engineering, there are no standards. Thus, 3D design plays a major role as assembly or installation process is unique and based on ‘know – how’.

Does it make you feel dizzy? ^^

Best,

Nikoloz

Nikoloz Sharmazanashvili CERN CADNikoloz Sharmazanashvili Works at the European Organization for Nuclear Research as a Project Analyst and CAD designer

Why Are My Street Lights Off?

By Tim
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candlelight2My first thought was the lights were out due to a storm, an accident, or a fire. But there was no evidence of any such calamity. Then I remembered that, to save money, my town of Plainville, Massachusetts was planning to turn-off the street lights. Apparently, tonight was the night for a majority of the lights to be turned-off. The town’s action reminded me of mother always saying, “Shut off the lights, you’re causing our electricity bill to get out of control”.

As a kid – I thought electricity was magic and endless, and I certainly thought it was free! I finally realized that electricity was not free when I received the first bill that I had to pay on my own.  Electricity is so pervasive, especially in developed countries, that most of us take it for granted, and maybe just a bit magical, until we find our streetlights turned off, or experience a multi-day power outage like I did after the Loma Prieta earthquake in California in 1989 and again in 2003 during the major Northeast blackout.

Electricity, as most of us know, is produced in a variety of ways. While Nuclear generated power gets a lot of attention, according to the U.S. Department of Energy, it only produces about 20 percent of the electricity in the United States. More than half of the U.S. electricity comes from burning coal. The remainder is produced through hydroelectric, or natural gas and even smaller amounts are created by wind and solar power systems.

Energy discussions can quickly devolve into controversy. I plan to leave the eco-political debates to others and focus a series of blog posts on the innovative use of realistic simulation to improve the efficiency and safety of energy creation and exploration.

Ensuring Nuclear Power Safety

From the onset of the civilian nuclear power era, there has been a strong awareness of the importance of safety. Originally designed for 30- to 40-year operating lives, the systems, structures, and components of nuclear plants  simply wear out, corrode, or degrade. Identifying and correcting such issues can extend the operating license of a plant by several decades, which is why the upgrading of older facilities is now a major focus of nuclear regulatory bodies and plant operators.

Wolfgang Hienstorfer, TÜV

Wolfgang Hienstorfer, TÜV

Recently, my team had the privilege of interviewing Wolfgang Hienstorfer, head of the department of structural analysis at TÜV SÜD ET, a leading global technical service corporation, located in Filderstadt, Germany.  “The structural integrity and operational management of nuclear facilities must be secured far into the future — whatever the type or age of the plant’,” stated Mr. Heinstorfer”. His team at TÜV independently tests, inspects, and certifies nuclear facilities for licensing by the German government.

To assist in the accurate evaluation of nuclear plant systems, structures and components, the group employs Abaqus finite element analysis (FEA) software from SIMULIA.  

Pressurized thermal shock analysis of a reactor pressure vessel

Pressurized thermal shock analysis of a reactor pressure vessel

Abaqus eanables the engineers to analyze stress loads over a wide range of scenarios such as rapidtemperature and/or pressure changes, earthquakes, and radiation embrittlement. The software analyzes everything from key mechanical components —including pumps, piping systems, vessels, supports, and tanks — to fuel assemblies, building structures, and lifting devices such as cranes.

Hienstorfer sees FEA as having an integral role to play in both operational evaluation and ongoing monitoring of nuclear facilities to assist in complying with regulations. “We depend on FEA for computer modeling and virtual testing of reactor pipelines, vessels, and materials under extremes of stress and time,” he says.  “It definitely provides guidance to engineers to build both safety and longevity into their nuclear power plant designs.”

Read the complete TUV case study online at Power Magazine or you can download a PDF of the story from SIMULIA’s INSIGHT Magazine.

Do you think engineers can continue to make Nuclear Energy safe?

What do you think of my town’s decision to save money by turning off the streetlights? (Maybe they should have positioned it as a ‘Green Initiative’?).

Check back soon or subscribe to 3D Perspectives for additional posts on Energy and Realistic Simulation.

Enjoy the magjic of electricity,

Tim



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