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What does it take to refuel a commercial nuclear power plant?

4/29/2014

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By Chris Wagener

Nuclear power plants are very different than their fossil fuel counterparts both in how the energy is generated and in the day to day operations. Both nuclear power plants and fossil fuel power plants rely on generating steam to spin a turbine to generate electricity but that is where the similarities end. Fossil fuel plants rely on burning hydrocarbons, such as coal and natural gas, to generate heat to boil water while nuclear power plants rely on fission. Fission generates substantially more energy than the burning of fossil fuels, especially on a pound per pound basis. Inside of a commercial nuclear power plant, fission is the splitting of a uranium and plutonium atoms into smaller atomic pieces.  By splitting these atoms, a large amount of energy is released. A fossil fuel plants works differently by chemically burning hydrocarbons into mainly water and carbon dioxide.

Have you ever seen a train carry loads of coal from a mine to a coal power plant? For a coal power plant to continue to generate electricity, coal must be constantly provided to the boiler.  However, for most commercial nuclear power plants, new fuel is added to the reactor every 12 to 24 months, which denotes the cycle of the reactor. Each cycle, between a quarter and a half the fuel assemblies, which contain the uranium and plutonium for fission, are removed and replaced with new fuel assemblies.  After the reactor is refueled, no fuel is added to the reactor and all the energy that will be generated during that cycle is already there, it only needs to be extracted.  Since the fuel will be in the same location in the reactor for up to 24 months, placement within the nuclear reactor is very important.

For each cycle, engineers start preparing up to a year and a half in advance to determine where the fuel assemblies should be located within the core. The first step in the process is to determine how many new fuel assemblies are required and what the uranium enrichment should be. This is the most important step since the manufacture and delivery of the new fuel takes a long time to ensure that the fuel is properly manufactured and inspected prior to use. Once the fuel is built and delivered, the fuel inventory is set for the cycle and it is very difficult to make major changes to the design.  During this phase, engineers will use computational tools to model the reactor core, which is made up of the fuel assemblies, to determine key characteristics of the cycle.  Once a candidate design has been determined, the safety analysis for the cycle can be performed.
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Nuclear fuel shown in a smaller research reactor.
For each cycle, engineers start preparing up to a year and a half in advance to determine where the fuel assemblies should be located within the core. The first step in the process is to determine how many new fuel assemblies are required and what the uranium enrichment should be. This is the most important step since the manufacture and delivery of the new fuel takes a long time to ensure that the fuel is properly manufactured and inspected prior to use. Once the fuel is built and delivered, the fuel inventory is set for the cycle and it is very difficult to make major changes to the design.  During this phase, engineers will use computational tools to model the reactor core, which is made up of the fuel assemblies, to determine key characteristics of the cycle.  Once a candidate design has been determined, the safety analysis for the cycle can be performed.

Due to the unique nature of nuclear power, a wide variety of safety analysis calculations are performed to ensure that the core will meet all the safety requirements as defined by the Nuclear Regulatory Commission (NRC). The calculations performed for each plant are documented in the plant’s Final Safety Analysis Report, describing all the work done to ensure the safety of the plant for a multitude of accident scenarios. Each time the reactor is refueled, engineers will perform calculations using core and plant models to show that in the event of an accident, the regulations set out by the NRC will be met. These regulations exists to ensure the safety of not only the public, but also the workers at the plant. Once the calculations have been completed, engineering reports are generated for submission to the NRC demonstrating that refueling the core continues to meet all the regulations and requirements. The safety analysis calculations that are performed each cycle are done to demonstrate that the plant can operate safely in the worst possible scenarios and during an accident.  
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After demonstrating that the core can safely operate for a cycle, engineers will generate the information necessary to operate the plant. This will include information for the plant to show to predict how the reactor will behave when intentional changes are made, such as going up and down in power. In addition, it provides information for the reactor operators to benchmark against their measurements. This is used to help ensure that the models used for the safety analysis were accurate. If any issues arise that indicate that the models were inaccurate at predicting the actual operation of the core, engineers will have to determine whether the plant can still operate safely given the new information. The final set of information provided to the plant before refueling the reactor, is all the information necessary to do what is called startup physics testing.

Startup physics testing is a series of tests performed after each refueling as the reactor is brought to power to demonstrate that the reactor is actually as it was modeled. This shows that the reactor is behaving as predicted and validates the safety analysis. Specific calculations are done each cycle and compared to the results of the startup physics testing. If the plant is within a certain tolerance to the predictions, it demonstrates that the safety analysis is bounding and the plant and continue to operate. If outside of the predictions, engineers must investigate to determine what the issue is and whether or not the plant can continue to operate.

After startup physics testing, the plant will continue to operate until the end of the cycle, assuming that the predictions remain accurate.  During this time, reactor operators will continue to check and ensure the overall safe performance of the reactor.  Once the startup is completed, engineers will restart the process to prepare for the next reactor refueling. Overall, nuclear power plants operate on a cyclical basis with the refueling of the reactor being the main goal. Once the refueling is performed, reactor operators monitor the performance of the core to ensure safe operations while other engineers prepare to refuel the core again.  The breakdown of this cyclical nature is to generate a design for the reactor cycle, demonstrate that the design can operate safely for the entire cycle, provide the necessary data for plant operations, including startup information, and then finally perform startup physics testing to validate all the work performed. After this process is completed, the reactor operators will operate the plant and ensure the safety of the reactor until the next refueling is needed.
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Radioactive Waste Management Facts

4/24/2014

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By Lenka Kollar

As a follow on to the meme that I posted last week for #Atoms4Earth, here's some more facts about radioactive waste that you should know. People often question "the waste problem" when talking about expanding nuclear energy. The reality is that nuclear power takes care of all of its waste, unlike coal and natural gas, which release much of their waste to the atmosphere. The amount of waste for nuclear is also much smaller than you think because reactors are only refueled once every 18 months on average.
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Here's some great facts from the World Nuclear Association:

  • Nuclear power is the only large-scale energy-producing technology which takes full responsibility for all its wastes and fully costs this into the product.
  • The amount of radioactive wastes is very small relative to wastes produced by fossil fuel electricity generation.
  • Used nuclear fuel may be treated as a resource or simply as a waste.
  • Nuclear wastes are neither particularly hazardous nor hard to manage relative to other toxic industrial wastes.
  • Safe methods for the final disposal of high-level radioactive waste are technically proven; the international consensus is that this should be geological disposal.

What questions do you have about radioactive waste?
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#Atoms4Earth

4/22/2014

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The Nuclear Literacy Project is celebrating Earth Day with a month-long campaign to create memes "inspired by the intersections of nuclear energy, the environment and social justice." You can search for the memes submitted on social media with the tag #Atoms4Earth on Twitter and Facebook. Here are the ones submitted by Nuclear Undone!
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There's a great mix of serious, inspiring, and funny memes created for #Atoms4Earth. Check out the Week 1, Week 2, Week 3, and Grand Prize winners!

Also, learn about why nuclear energy can play an important

How are you celebrating Earth Day today? Read about what I'm doing here.
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The Periodic Table of Elemental Discoveries

4/17/2014

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Have you seen this Periodic Table of the Elements categorized by country location of discovery? This image was created by science communicator Jamie Gallagher by The Smithsonian. 
The Period Table of Elemental Discoveries
Click to see larger image.
From Jamie Gallagher:
One of my favourites has to be polonium, though, the first element to be discovered by Marie and Pierre Curie. They were working in a modified shed with substances so dangerously radioactive their notes are still too active to be handled safely.

Working together they isolated this element and later named it Polonium after Marie’s home country. (A country, I may add, that turned her away from her pursuit of education as she was a politically interested female). It was her hope that by naming the element after Poland she could generate interested in the independence (from Germany) campaign for the country. Yet the victory comes in under the French flag where the work was carried out.

It remains to this day the only element to be named after a political cause, and a wonderful tribute to a phenomenal woman.

What is your favorite element or story of discovery?
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Nuclear Technology Preserves Art in Romania

4/10/2014

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Think nuclear technology is just about nuclear energy? Think again. There are limitless applications for nuclear science and radiation, including protecting and preserving works of art around the world. The techniques in this video are supported by the International Atomic Energy Agency (IAEA), which operates projects to preserve cultural heritage artifacts using radiation.

Watch the video to learn more!
What are your thoughts?
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Argonne Energy Slam

4/8/2014

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By Lenka Kollar

Last week Argonne National Laboratory held an Energy Slam featuring four Argonne researchers to debate non-fossil energy sources. If you missed the webcast, here's a great recap. Each presenter had 10 minutes to give the case for their energy source and then the audience voted by clapping for their favorite.
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Nuclear -  J’Tia Taylor, nuclear engineer and Nonproliferation Technical Associate at Argonne (pictured above)
  • The 1957 Disneyland episode Our Friend the Atom
  • Reliable, efficient, near-zero emissions
  • Lowest mortality rate of ANY electricity source
  • Doesn't need back-up fossil plant (like wind and solar)
  • Lowest carbon emitting and no greenhouse gases

Wind - Guenter Conzelmann, head of Argonne’s Wind Power Technologies and Analysis Program
  • Zero fuel, no waste
  • Doesn't run the risk of major nuclear accidents
  • 23 fold increase in wind capacity over the last 15 years (globally)
  • Wind is variable because of weather but we can manage it
  • 70% of everything that goes into a wind turbine is made in the U.S.

Biofuels - Jennifer Dunn, head of Argonne’s Biofuel Life Cycle Analysis Team
  • The other sources only work if we can electrify the transportation sector 
  • Hard to beat the energy density of liquid fuels
  • We can convert landfill waste to biofuel
  • Not just corn ethanol, but also waste and energy crops, algae, oil crops, and soy
  • Lots of interest for biofuels in aviation, both military and commercial

Solar - Seth Darling, nanoscientist who focuses on solar energy conversion
  • All energy is actually solar energy (except man-made nuclear)
  • Feasible to use about 2% of land in U.S. for solar
  • Solar prices have been coming down drastically
  • Can design solar panels into architecture
  • Can design grid to handle variability and utilize energy storage
  • Democratization of energy because you don't need a utility and can sell back to grid
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All of the presenters made a great case for their energy source and of course the answer is an "all of the above" approach. However, Argonne used a tool to measure the decibel level of the audience applause and determined that Seth Darling and his solar presentation had the most support. Probably because he brought a prop (pictured above); a flexible solar panel on which he was charging his phone!

Watch the full video of the Argonne Energy Slam here.

Which energy source gets your vote?
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Apply Now! The Nuclear Engineering Student Delegation

4/4/2014

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By Nicholas Thompson

The Nuclear Engineering Student Delegation (NESD) is a student run organization that brings students from around the country to Washington, D.C., for a week over the summer to talk with politicians and policymakers about nuclear engineering education funding, energy policy, and any other concerns nuclear engineering students may have. 
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Delegates start the week with writing a policy statement expressing their concerns and interests, which is distributed in meetings throughout the week. Last year, delegates met with key governmental affairs staff at the Nuclear Energy Institute (NEI) and Areva, high level staff at the Department of Energy’s Office of Nuclear Energy (DOE NE), four of the five Nuclear Regulatory Commission (NRC) Commissioners (including the Chairman), non-proliferation experts at the Department of State, budget staff at the Office of Management and Budget (OMB), staff on the Natural Resources and Environment and Public Works Committees, and over one hundred congressional offices (including a few Representatives and Senators in person). The NESD gives students a voice in government and helps to inform policymakers about nuclear issues while simultaneously giving students an inside perspective on how government works and how to get involved.
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Anyone who is interested in policy or government, or just wants to have their voice heard should apply on the website. The program is open to both undergraduate and graduate students. Applications are due on April 20th. Policy statements from the previous years can be found here and for more information or for answers to any questions, please contact NESD.
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Where Do Nuclear Engineering Students Work After Graduation?

4/3/2014

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By Lenka Kollar

Earlier this month, the Oak Ridge Institute for Science and Education (ORISE) published its annual survey on nuclear engineering enrollment and degrees. The 2013 data shows that the number of graduates in nuclear engineering programs continues to grow (shown below) and that students work in a variety of fields after graduation.
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Read this full article on the ANS Nuclear Cafe...
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Congress passes new Clean Energy Act

4/1/2014

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By Lenka Kollar

Congressmen have long disagreed on global warming and the need for clean energy but the two sides of of the isle finally came together on legislation that will drastically reduce carbon emissions. The game-changer is actually the oldest form of energy used by man: wood-burning fire. 
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Greenpeace heavily advocating for the passing of this bill because when trees are grown sustainably and burned for heat, the process is carbon-neutral. "This is the cleanest form of energy we've got," says President Obama, "Forget windmills and solar cells, the people in the dark ages had it right. This bill is our first step to fighting climate change."
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The new Clean Energy Act calls for phasing out of all electric power plants by 2020 and requirements for all new construction to contain fireplaces. The Department of Energy is also working on an efficient wood-burning engine for cars and long-lasting candles for indoor lighting. The EPA estimates that carbon emissions should decrease back to pre-industrialization levels by 2040 and that climate change will no longer be an issue. 

Rumors on the Hill also indicate that bills for demilitarization and outlawing marriage are being negotiated.

Happy April 1st!
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Photos from Idaho National Laboratory, Jim.Richmond, Idaho National Laboratory, IAEA Imagebank