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Moments in NRC History: Research and Test Reactors Series

Thomas Wellock

One of the earliest proposals to meet “the promise of the peaceful atom” was a small research reactor so simple and inexpensive that universities could buy one for scholars and students. That was the plan back in April 1948.

The Atomic Energy Commission (the NRC’s predecessor agency) touted research reactors as a peaceful counterpoint to nuclear weapons. The AEC thought research reactors could jump-start a civilian industry at home and cultivate allies abroad. And in large measure, it worked. As the nation’s first civilian owned reactors, they broke down military secrecy and demonstrated the atom’s peaceful potential for education, medicine, research, and industry.

Moments in NRC History_The first of a series of videos outlining this promise and the unique safety challenges of research reactors went live today on the NRC’s YouTube channel.

The video starts its journey with North Carolina State College’s first civilian-owned reactor — part of its new program in nuclear engineering. Then, two years later, Oak Ridge’ research reactor made a debut in Geneva, Switzerland, in 1955. It was an inexpensive “swimming pool” reactor unveiled at the world’s first international conference on the peaceful uses of nuclear energy. Over 60,000 people, including prime ministers, royalty, and presidents, lined up to peered down into the blue glow of the future.

As the video points out, dozens of universities and corporations followed with their own research reactors. They were small, safe, and used only a small amount of uranium fuel compared to nuclear power plants. For only a small investment, researchers could open up the secrets of the atom and produce isotopes critical to medicine and industrial uses. Ultimately, these research reactors led to the innovative idea of testing the age of ancient pottery

Worldwide more than 670 research reactors were built in 55 countries with 227 in the United States alone.

We hope you’ll take the time to watch the video. And look for the next one coming soon, focusing on key challenges in ensuring safety, preventing diversion of  fuel for weapons, and preserving the benefits of research reactors even as their numbers have declined.


Examining the Reasons for Ending the Cancer Risk Study

Scott Burnell
Public Affairs Officer

One way NRC regulations protect communities around U.S. nuclear power plants is by requiring the plants to regularly sample air, water, and vegetation around their sites. Results of this sampling are sent to the NRC (and in some cases state agencies) to show only very tiny amounts of radioactive material are released during normal operations.

Even with this scrutiny — and a 1990 study showing no difference in cancer mortality rates between those living near U.S. reactors and those living elsewhere — questions persist about cancer risk from nearby reactors. The NRC had worked with the National Academy of Sciences (NAS) since 2010 on a study into the potential cancer risk of living near a U.S. nuclear power plant. But we ended this work earlier this month after a hard look at the low likelihood of getting usable results in a reasonable time frame.

radiationsymbolWhy are we comfortable that this decision, also driven by our budget situation, is in line with our mission to protect public health and safety?

First and foremost, the staff considered existing conditions around U.S. reactors, as shown by the ongoing environmental sampling and analysis we mentioned earlier. That evidence supports the conclusion that the average U.S. citizen’s annual radiation dose from natural sources, such as radon and cosmic rays, is about a hundred times greater than the largest potential dose from a normally operating reactor.

This information shows how complicated it would be to single out an operating reactor’s potential contribution to cancer risk. Researchers looking for small effects need a very large study population to be confident in their results. The NAS discussed this issue in its report on Phase 1 of the cancer risk study. The NAS said that the effort “may not have adequate statistical power to detect the presumed small increases in cancer risks arising from… monitored and reported releases.”

The NRC staff examined the NAS Phase 2 report plans to validate the methods recommended in Phase 1. The Academy was very clear that the pilot study at seven U.S. sites was unlikely to answer the basic risk question. The NAS proposal said: “any data collected during the pilot study will have limited use for estimating cancer risks in populations near each of the nuclear facilities or for the seven nuclear facilities combined because of the imprecision inherent in estimates from small samples.”

The pilot study would also examine potential differences between individual states’ cancer registries. Large differences in registry quality or accessibility would hurt the study’s chances of generating useful results.

The NAS concluded they would need more than three years and $8 million to complete the pilot study. If the pilot succeeded, expanding the research to all U.S. operating reactors would require additional years and tens of millions of dollars. The NRC decided that in our current budget environment the time and money would not be well spent for the possible lack of useful results.

The NRC agrees with the NAS that the study’s overall approach is scientifically sound. Interested individuals or groups can examine the NAS Phase 1 and 2 reports for a more detailed discussion of the methods and resources needed to conduct the proposed study. The NRC staff will examine international and national studies on cancer risk to see if we should conduct any future work in this area.

REFRESH — Who Sets National Nuclear Energy Policy?


refresh leafWho decides if the U.S. is going to use nuclear energy to meet this country’s electric needs? It’s a question we get here at the NRC not infrequently. The short answer: Congress and the President. Together they make the nation’s laws and policies directing civilian nuclear activity – for both nuclear energy and nuclear materials used in science, academia, and industry.

Federal laws, like the Atomic Energy Act, set out our national nuclear policy. For example, in the Atomic Energy Act, Congress provided that the nation will “encourage widespread participation in the development and utilization of atomic energy for peaceful purposes.” Other federal laws, like the Energy Policy Act of 2005, call for the federal government to provide support of, research into, and development of nuclear technologies and nuclear energy. The President, as the head of the executive branch, is responsible for implementing these policies.

But sometimes, things get confusing as to who does what when it comes to putting these laws into practice! Although the NRC is a federal government agency with the word “nuclear” in its name, the NRC plays no role in making national nuclear policy. Instead, the NRC’s sole mission is to regulate civilian use of nuclear materials, ensuring that the public health, safety, and the environment are adequately protected.

The NRC’s absence from nuclear policymaking is no oversight, but a deliberate choice. Before there was an NRC, the U.S. Atomic Energy Commission (AEC) was responsible for both developing and regulating nuclear activities. In 1974, Congress disbanded the AEC, and assigned all of the AEC’s responsibilities for developing and supporting nuclear activities to what is now the U.S. Department of Energy (DOE). At the same time, Congress created the NRC as an independent regulatory agency, isolating it from executive branch direction and giving it just one task – regulating the safety of civilian nuclear activities.

Today, the DOE, under the direction of the President, supports federal research and development of nuclear technologies and nuclear energy in accordance with federal laws and policy goals. At the DOE, the Office of Nuclear Energy takes the lead on these programs.

Since its creation  four decades ago, the NRC’s only mission has been to regulate the safe civilian use of nuclear material. For that reason, the most important word here in the NRC’s name is not “Nuclear,” but “Regulatory.” Because the NRC has no stake in nuclear policymaking, the NRC can focus on its task of protecting public health and safety from radioactive hazards through regulation and enforcement.

REFRESH is an occasional series where we revisit previous posts. This originally ran in August 2012.


Dry Cask 101 – Criticality Safety

Drew Barto
Senior Nuclear Engineer

CASK_101finalIn earlier Science 101 posts, we told you about how nuclear chain reactions are used to generate electricity in reactors. In a process known as fission, uranium atoms in the fuel break apart, or disintegrate, into smaller atoms. These atoms cause other atoms to split, and so on. This “chain reaction” releases large amounts of heat and power. Another word for this process is “criticality.”

The potential for criticality is an important thing to consider about reactor fuel throughout its life. Fuel is most likely to go critical when it is fresh. It is removed from the reactor after several years (typically four to six) because it will no longer easily support a self-sustaining chain reaction. This “spent fuel” is placed into a storage pool. After cooling for some time in a pool, the fuel may be put into dry storage casks.

Here, a spent fuel assembly is loaded into a dry storage cask.

Here, a spent fuel assembly is loaded into a dry storage cask.

When fuel is removed from the reactor, we require licensees to ensure it will never again be critical. This state is referred to as “subcriticality.” Preventing an inadvertent criticality event is one safety goal of our regulations. Subcriticality is required whether the fuel is stored in a pool or a dry cask. We require it for both normal operating conditions and any accident that could occur at any time.

There are many methods that help to control criticality. The way spent fuel assemblies are positioned is an important one. How close they are to each other and the burnup of (or amount of energy extracted from) nearby assemblies all have an impact. This method of control is referred to as fuel geometry.

Certain chemicals, such as boron, can also slow down a chain reaction. Known as a “neutron absorber,” boron captures neutrons released during fission, and keeps them from striking uranium atoms. Fuel burnup is another factor. As we said above, after some time in the reactor it is harder for fuel to sustain a chain reaction. The longer the fuel is in the reactor, the less likely it is to go critical. However, high burnup fuel generates greater heat loads and radiation, which must be taken into account.

Spent fuel storage cask designs often rely on design features to make sure the fuel remains subcritical. When we review a cask design, this is one of the key elements the NRC looks at in detail.

Casks have strong “baskets” to maintain fuel geometry. They also have solid neutron absorbers, typically made of aluminum and boron, between fuel assemblies. The applications that we review must include an analysis of all the elements that contribute to criticality safety. Part of the analysis is a 3-D model that shows how the fuel will act in normal and accident conditions.

A dry storage canister is loaded into a horizontal storage module.

A dry storage canister is loaded into a horizontal storage module.

Our technical experts review this analysis to make sure the factors that could affect criticality have been identified. We check to see that the models address each of these factors in a realistic way. In cases where the models require assumptions, we make sure they are conservative. That means they result in more challenging conditions than we would actually expect. We also create our own computer models to confirm that the design meets our regulatory requirements. We will only approve a storage cask design if, in addition to meeting other safety requirements, our criticality experts are satisfied that our subcriticality safety requirements have been met.

Our reviewers look at several other technical areas in depth any time we receive an application for a spent fuel storage cask. We will talk about some of the others—materials, thermal, and shielding—in future posts.

The Open Forum is Open for Business

Holly Harrington
Blog Moderator

communicationwordcloudWe created the Open Forum section of the NRC blog more than four years ago. It was not part of our original plan, but our blog comment guidelines stipulated that comments needed to be related to the topic of the post to which they are submitted. We quickly realized there were a number of comments being submitted that didn’t adhere to this guideline and would have therefore not been posted, but otherwise met the comment criteria. And we wanted to be able to post them. So we decided we needed a place where anyone could bring up any topic they wish (related to the NRC).

And so the Open Forum section was created.

Since its creation there have been more than 300 submitted comments on a wide range of topics including climate change, nuclear power’s future and solar storms.

Comments on the Open Forum (as with the rest of the blog) are moderated and must adhere to the Comment Guidelines. Otherwise, the platform is open for any NRC-related topic you’d like to bring up or to comment on. It’s important to note that blog comments are not considered formal communication with the NRC. Questions and concerns can always be submitted in a variety of formal ways. Safety or security allegations should not be submitted via the blog, and will not be posted if submitted. For more information, go here.

You can easily find the Open Forum section listed on left side of every page of the blog. You can also sign up to receive notice of new comments to the section by clicking on “Reply” at the bottom of the comments and then clicking the “Notify me of new comments via email” box.


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