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Western U.S. Reactors are Completing Their Seismic Picture

Lauren Gibson
Project Manager
Japan Lessons-Learned Division

An ongoing lesson from 2011’s Fukushima Dai-ichi accident involves U.S. reactors better understanding their earthquake hazard. Reactor owners in the Western parts of the country have had to assemble a particularly complex jigsaw puzzle of seismic information. They’ve just sent the NRC their detailed re-analysis.

seismicgraphicThe graphic shows the three pieces of information U.S. reactor owners have used to analyze their specific hazard:

  • Where quakes are generated (seismic source)
  • How the country’s overall geology transmits quake energy, (ground motion/attenuation) and
  • How an individual site’s geology can affect quake energy before it hits the reactor building (site amplification).

Central and Eastern U.S. reactors benefitted from region-wide updated earthquake source information and a model of quake energy transmission for the first two pieces. Plants west of the Rockies, however, had to deal with the West’s more active and interconnected faults.

Columbia, Diablo Canyon Part I and Part II and Palo Verde used the Senior Seismic Hazard Analysis Committee (SSHAC) approach to develop site-specific source models and ground-motion models. This group of independent seismic experts develops guidance on major seismic studies such as this. The group has met several times the past few years to ensure the Western plants properly conduct and document their seismic activities.

The NRC carefully considers SSHAC comments and recommendations before the agency comes to its own conclusions on seismic issues. We’re currently evaluating the Western plants’ reports and will issue our short-term screening and prioritization review later this spring.

As for the Central and Eastern U.S. plants’ March 2014 submittals, we screened them to determine what other actions the plants might have to take. Plants that have more to do were grouped into three priority groups with staggered deadlines. Many of those plants submitted additional analyses in December 2014, and the NRC continues reviewing both that information and the March 2014 submittals.

Dry Cask Storage – The Basics

Michele Sampson
Chief, Spent Fuel Licensing Branch
Division of Spent Fuel Management

Fuel pellets, rods, and casks_r9You may have read our recent Science 101 posts in which we explained the basics of nuclear fuel and what happens when it is taken out of the reactor. We mentioned storing it in a pool, something every reactor in this country does immediately after removing the fuel. Today we want to talk about the option of storing spent nuclear fuel in dry casks.

Pools can only hold so much spent fuel. As they began filling up, utilities started looking for other ways to manage their fuel. A handful of companies developed dry storage systems. The idea is that after the fuel spends some time cooling in the pool, it can be loaded into a cask that is sealed to keep the radioactive material inside and protected.

At its most basic, a dry storage system is a cylinder that is lowered into the pool and filled with spent fuel. When full, the cylinder is raised and dried before it is sealed and placed outdoors. There are many varieties of spent fuel storage casks. All storage casks need to manage the spent fuel’s heat and contain its radioactivity, and to prevent nuclear fission (the chain reaction that allows a reactor to produce heat). The casks must resist earthquakes, tornadoes, floods, temperature extremes and other scenarios.

Casks come in different sizes. They are tall enough to hold spent fuel, which can be 14 feet long, and they can weigh up to 150 tons—as much as 50 midsize cars. In fact, plants may need a special crane that can handle heavy loads to be able to lift a loaded cask full of water out of their pool for drying. After the casks are dried and filled with helium, robotic equipment welds them closed to keep doses to workers as low as possible. Then the canisters are tested to ensure they are sealed.

And once the dry, welded canister is placed inside thick shielding, the plants use a special transporter to move the cask outdoors to where it will be stored. At that point, the radioactivity from the cask must be less than 25 millirem per year at the site boundary. That means the highest dose to someone standing at the fence for a full year would be about what you would get going around the world in an airplane. The actual dose at the site boundary is typically much lower. As of December 2014, just over 2,000 casks have been loaded and are safely storing nearly 84,000 spent fuel assemblies.

Cask designers must show their cask systems meet our regulatory requirements. The NRC staff reviews their applications in detail. We only issue an approval to systems that we know can perform safely.

Most dry storage systems in use today have the spent fuel placed into an inner metal canister that is welded shut, then placed into a large metal or metal-and-concrete cask. The canisters are designed so they can be removed and put into transportation casks for eventual shipment offsite. Some casks store the fuel horizontally, the others vertically.

drystoragegraphic)The NRC inspects the design, manufacturing and use of dry casks. These inspections ensure licensees and vendors are following safety and security requirements and meeting the terms of their licenses and quality assurance programs. NRC inspectors also observe practice runs before utilities begin moving their spent fuel into dry casks.

There are strict security requirements in place to protect the stored fuel. Security has multiple layers, including the ability to detect and respond to an intrusion. There have been no known or suspected attempts to sabotage cask storage facilities.

Since the first casks were loaded in 1986, dry storage has released no radiation that affected the public or contaminated the environment. Tests on spent fuel and cask components after years in dry storage confirm that the systems are providing safe storage.

The NRC also analyzed the risks from loading and storing spent fuel in dry casks. That study found the potential health risks are very, very small. To ensure continued safe dry storage of spent fuel, the NRC is further studying how the fuel and storage systems perform over time. The NRC is also staying on top of related research planned by the Department of Energy and nuclear industry.

We’ll talk about “high burnup spent fuel,” which is receiving a lot of attention at shutdown reactor sites, in an upcoming blog post.

 

Spreading the Sunshine!

Stu Reiter
Co-Chair Open Government Advisory Group

Given the terrible winter much of the U.S. has been experiencing, you may be excited to learn that next week is “Sunshine Week.” But before you break out the beach towels, you should know that the week actually celebrates the public’s right to know its government’s business. In fact, this year marks the initiative’s 10th anniversary.

sunshineSunshine Week was launched by the American Society of News Editors in March 2005. This non-partisan, non-profit initiative is celebrated in mid-March each year to coincide with James Madison’s birthday on March 16.

We thought it an excellent time to highlight the NRC’s actions to be open and transparent about its business. The NRC has a long history of commitment to openness and transparency and encouraging stakeholder and public engagement. Most recently, we’ve used Web streaming and conferencing technologies to enhance public participation in our public meetings, regardless of stakeholder location. And our web-based systems make it easier to share public meeting information before and after, and for the public to provide feedback on these meetings.

And, we have embraced President Obama’s Open Government efforts to make the federal government even more open and accountable and to increase citizen participation, collaboration, and transparency in government.

In January, 2009 the President instructed OMB to issue an Open Government Directive. To comply with the directive, each agency was required to develop and publish an Open Government Plan (updated every two years) describing how it will improve transparency and integrate public participation and collaboration into its activities. NRC’s most recent plan can be found here. Examples of commitments highlighted in our plan include:

  • Reducing the average FOIA request processing time and backlog.
  • Enhancing availability and delivery of official agency information throughout the public Website.
  • Making it easier for mobile users to find/access regulatory information.
  • Continued use of Social Media to share information with the public – launching Facebook.
  • Promoting the objective of clear communications, the use of plain language.
  • Increasing the transparency of our rulemaking activities.

President Obama then went further, and in September 2010, he challenged members of the United Nations General Assembly to work together to make all governments more open and accountable to their people. To meet that challenge, in July 2011, President Obama joined the leaders of seven other nations in announcing the launch of the Open Government Partnership – a global effort to encourage transparent, effective, and accountable governance. Now, some 60 nations participate, affecting more than 2 billion people around the world.

As an organization, the NRC is dedicated to continuous improvement. We will continue to focus on what is important to our stakeholders and public — FOIA responsiveness, maintaining our public Web site as the agency’s central information portal and providing a mobile‑friendly Web site, growing our social media programs and modernizing our records management program.

NRC Science 101 – About Spent Nuclear Fuel Part II

Greg Casto
Branch Chief
Division of Reactor Safety Systems

 
science_101_squeakychalkOur last post talked about the fuel that powers nuclear reactors. Today, we’ll talk about what happens to that fuel when it’s removed from a reactor.

You’ll recall that fuel becomes very hot and very radioactive as it is used in the reactor core to heat water. After about five years, the fuel is no longer useful and is removed. Reactor operators have to manage the heat and radioactivity that remains in the “spent fuel” after it’s taken out of the reactor. In the U.S., every reactor has at least one pool on the plant site where spent fuel is placed for storage. Plant personnel move the spent fuel underwater from the reactor to the pool. Over time, as the spent fuel is stored in the pool, it becomes cooler as the radioactivity decays away.  

These pools contain an enormous quantity of water—enough to cover the fuel by about 20 feet. The water serves two purposes: it cools the fuel and shields workers at the plant from radioactivity. Having 20 feet of water above the fuel means there is a lot more water than is needed for cooling and shielding the workers. Also, because of the extra water and the simple design of the pool, there is a lot of time for plant personnel to add water to the pool if needed for any reason.

fuelpoolThe pools are built to meet strict NRC safety requirements. They have very thick, steel-reinforced concrete walls and stainless-steel liners, and are protected by security personnel. There are no drains that would allow the water level to drop or the pool to become empty. The plants have a variety of extra water sources and equipment to replenish water that evaporates over time, or in case there is a leak. Plant personnel are also trained and prepared to quickly respond to a problem. They keep their skills sharp by routinely practicing their emergency plans and procedures.

When the plants were designed, the pools were intended to provide temporary onsite storage. The idea was for the spent fuel to sit in the pool for a few years to cool before it would be shipped offsite to be “reprocessed,” or separated so usable portions could be recycled into new fuel. But reprocessing didn’t end up being an option for nuclear power plants and the pools began to fill up.

In the early 1980s, nuclear plants began to look for ways to increase the amount of spent fuel they could store at the plant site. One way was to replace spent fuel storage racks in the pools with racks containing a special material that allowed spent fuel to be packed closer together. Another way was to place older, cooler and less radioactive fuel in dry storage casks that could be stored in specially built facilities at the plant site. We’ll talk more about dry spent fuel storage in future blog posts.

Most plants today use both re-designed storage racks and dry storage facilities to store spent fuel. All storage methods must be reviewed in detail and approved by the NRC before a plant is allowed to change storage methods.

OIG Audits NRC’s Scientific Research Program

Stephen Dingbaum
Assistant Inspector General for Audits

An Office of the Inspector General audit regarding the NRC’s process for ensuring integrity in scientific research is now available here. The audit set out to determine if the NRC has the controls is place to oigassure that scientific research is objective, credible, and transparent.  

The NRC’s regulatory research program conducts research in the areas of nuclear reactors, nuclear materials, and radioactive waste. Scientific information that supports research includes factual inputs, data, models, analyses and technical information, or scientific assessments. This scientific information often informs NRC regulations.

The OIG found that while the NRC has controls in place, the way it manages scientific information, including information associated with scientific research, needs to be strengthened. Specifically, the NRC must improve the internal controls associated with responding to public requests to correct scientific information and for designating it as influential scientific information. Additionally, the OIG audit states the NRC must adopt required guidelines on conducting peer review of its information products associated with scientific research.

The audit also states the NRC must have effective controls in place to ensure that its information products are objective, credible, and transparent. Without effective controls, an opportunity for maximizing the quality, objectivity, utility, and integrity of NRC scientific information is being missed and may result in compromising stakeholder confidence in NRC’s ability to regulate in an unbiased, trustworthy, and open manner.

The report makes five recommendations specific to the way the NRC handles scientific information, to ensure that the NRC adopts federal requirements on peer review, and to ensure that internal guidance that may be impacted by new or revised federal guidance is regularly reviewed to determine if revisions are necessary.

NRC management stated their general agreement with the audit findings and recommendations.

 

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