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Category Archives: Radioactive Waste

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.

Science 101 – What is Nuclear Fuel?

Kevin Heller
Reactor Systems Engineer, Division of Safety Systems

science_101_squeakychalkIn earlier Science 101 posts, we told you about nuclear chain reactions and how they are used to generate electricity in reactors. This post focuses on the fuel that reactors use to create those chain reactions.

You may recall that nuclear fuel rods get hot because of the nuclear reaction, and that heat is key to generating electricity. But what exactly are these fuel rods?

Nuclear fuel starts with uranium ore, which is found in the ground throughout the world. For now, we’ll just say that uranium ore goes through several steps to be processed and manufactured into nuclear fuel. In a future Science 101 post, we’ll talk more about the process of turning uranium ore into fuel pellets.

fuelpelletEach pellet is about the size of a pencil eraser. These pellets are stacked inside 12-foot long metal tubes known as fuel cladding. The tubes are sealed on each end to form a fuel rod, and between 100 and 300 fuel rods are arranged in a square pattern to form a fuel assembly. The number of fuel rods used to make a fuel assembly depends on the type of reactor the assembly will be used in and the company that makes the fuel.

fuelrodsWhile the assemblies are very long (about 12 feet), they are less than 1 foot wide. The assemblies have special hardware at the top and bottom and at intervals in between to keep the fuel rods firmly held and evenly spaced. Fuel assemblies are only slightly radioactive before they are placed into a reactor core. Typically, a reactor core will have between 150 and 250 fuel assemblies.

We talked before about the form of uranium that is important in commercial nuclear reactors. It is an “isotope,” or an atom with a very specific number of neutrons, known as U-235. Part of the process of turning uranium ore into nuclear fuel is enrichment—which increases the amount of U-235 relative to the other isotopes naturally found in uranium. Under the right conditions in a reactor, neutrons will cause U-235 atoms to fission, or split. This leaves two new, different atoms and a couple of neutrons. These new neutrons will then cause other U-235 atoms to fission, forming a chain reaction.

As U-235 atoms fission, energy is released in the form of heat. That heat creates steam which turns a turbine to create electricity. After a few years, there is considerably less U-235 in the fuel. If the amount of U-235 were to drop too low, there would no longer be enough to keep a chain reaction going. So every 18-24 months about one-third of the fuel in a reactor core is removed and replaced with new, fresh fuel. The used fuel is often called “spent fuel.”

Spent fuel is very hot and very radioactive. The atoms created by the fission process are unstable at first and emit particles that create heat. Therefore, spent fuel must be handled and stored carefully, and under controlled conditions. We’ll talk more about spent fuel and how it is managed in a future Science 101 post.

The Yucca Mountain Safety Evaluation Report: One Step of a Long Journey

David McIntyre
Public Affairs Officer

The NRC staff has now completed its safety evaluation report (SER) on the proposed nuclear waste repository at Yucca Mountain in Nevada, with the publication of Volume 2 and Volume 5. This is an important milestone – however, completion of the SER neither finishes the review process nor represents a licensing decision.


To recap: The NRC closed its review of the application in fiscal year 2011. (The full story is here.) The NRC staff published Volume 1 of its five-volume SER in August 2010. Volume 1 covered general information about the application. The NRC staff subsequently published three technical evaluation reports to capture the work it had already done on volumes 2, 3 and 4, though without any regulatory conclusions.

In August 2013, the U.S. Court of Appeals for the District of Columbia Circuit ordered the NRC to resume the licensing process using leftover money appropriated from the Nuclear Waste Fund. So the agency resumed its work on the formal safety evaluation report. We published Volume 3, covering repository safety after permanent closure, in October 2013. Volume 4, on administrative and programmatic requirements, was published in December. Volume 2, repository safety before permanent closure, and Volume 5, license specifications, complete the SER and the technical part of the licensing review.

That technical review concluded DOE’s application meets the safety and regulatory requirements in NRC’s regulations, except for DOE’s failure to secure certain land and water rights needed for construction and operation of the repository. These issues were identified in Volume 4.

Bottom line: the SER recommends that the Commission should not issue a construction authorization until DOE secures those land and water rights, and a supplement to DOE’s environmental impact statement (EIS) is completed.

The land DOE still needs to acquire is owned by three federal agencies: DOE’s National Nuclear Security Administration, the Department of the Interior and the Department of Defense. Legislation was introduced in Congress in 2007 to appropriate the land for the repository, but it did not pass. The water rights DOE needs are owned by the state of Nevada, which refused to appropriate the water in 1997. Litigation challenging that refusal is stayed.

yuccatunnelWhen the NRC resumed its licensing review in response to the appeals court, the agency asked DOE to supplement the EIS to cover certain groundwater-related issues. DOE declined to do so. The NRC staff is prepared to develop the supplement if the Commission tells it to.

Even if the EIS is completed, two more steps are needed before a licensing decision can be made. The adjudication of nearly 300 contentions filed by Nevada and other parties challenging the repository was also suspended in 2011. Reviving and completing this hearing will require more funding from Congress. Finally, the Commission must review issues outside of the adjudicatory context. Only then would the Commission decide whether to authorize construction.

So yes, completion of the SER is a major step, but there are many more ahead before the NRC can say yea or nay to Yucca Mountain.


“Continued Storage” – What It Means and What it Doesn’t

David McIntyre
Public Affairs Officer

UPDATE: The NRC’s final rule on the continued storage of spent nuclear fuel was published in the Federal Register on September 19, 2014, becoming effective October 20.The final Generic Environmental Impact Statement for Continued Storage of Spent Nuclear Fuel is available on the NRC website.

There has been some confusion in media reports about the purpose of the NRC’s new rule on continued storage of spent nuclear fuel. The rule, approved by the Commission August 26, will be published soon in the Federal Register and take effect 30 days later.

The continued storage rule specifically deals with the period of time after the reactor has ceased operating. The rule adopts the NRC staff’s assessments of the environmental effects of storing spent nuclear fuel at a reactor site for various periods of time following the reactor’s licensed life for operation. It adopts the conclusions of the agency’s Generic Environmental Impact Statement (GEIS) on the Continued Storage of Spent Nuclear Fuel, also approved August 26 by the Commission.

drystoragegraphic)For each new reactor, license renewal application, and storage facility specific license or renewal, the NRC performs a thorough safety review of reactor operations and spent nuclear fuel management at the site. Separately, the National Environmental Policy Act requires the NRC to perform an environmental analysis of each licensing action, which considers impacts on the surrounding environment.

The continued storage rule, when implemented, will allow the NRC to process license applications and renewals for nuclear reactors and spent fuel storage facilities without assessing the portion attributed to the environmental impacts of continued storage. This is because such impacts have now been generically assessed by the NRC in the GEIS.

The GEIS analyzed three scenarios:

  • A geologic repository for disposing of spent fuel becomes available 60 years following the licensed life of a reactor (short-term storage);
  • A repository becomes available 100 years beyond the short-term scenario, or 160 years after the licensed life of a reactor (long-term storage); and
  • A repository never is available (indefinite storage).

In evaluating the third scenario, the GEIS assumed that licensee control and regulatory oversight, or “institutional controls,” will remain in place to ensure the safety and security of the waste as long as needed.

The short-term and long-term scenarios reflect current U.S. policy that spent nuclear fuel will be disposed of in a deep geologic repository. The indefinite storage scenario is included because the Appeals Court that struck down the earlier version of the rule directed the NRC to consider the possibility a repository may never be built.

The rule is not a safety decision or licensing action for any site; it does not authorize the initial or continued operation of any nuclear power plant, and it does not authorize storage of spent fuel. The NRC licenses spent fuel storage through other means: Spent fuel pools are covered by a plant’s operating license, and dry cask storage is permitted either through a general license or a separate license, with licenses or certificates for casks issued for up to 40 years.

Media headlines proclaiming that nuclear waste will be stored in place indefinitely under this rule, or that safety controls on spent fuel storage will be weakened, do not accurately reflect the rule’s purpose or effect. Ultimate responsibility for the disposition of spent fuel lies with Congress and the Department of Energy. DOE’s most recently stated goal is to have a repository available by 2048. The NRC is committed to ensuring that spent fuel remains safe and secure, wherever it is stored or disposed.

NRC’s Materials and Waste Management Programs Coming Back Under One Roof

Chris Miller
Merge Coordinator and Director of Intergovernmental Liaison and Rulemaking


When Congress created the NRC in 1974, it established three specific offices within the agency. One of them was the Office of Nuclear Material Safety and Safeguards, or “NMSS” in NRC shorthand. This office was charged with regulating nuclear materials and the facilities associated with processing, transporting and handling them.

fuelcyclediagramThis charge was, and is, broad. The NRC’s materials and waste management programs cover facilities that use radioisotopes to diagnose and treat illnesses; devices such as radiography cameras and nuclear gauges; and decommissioning and environmental remediation. It also includes nuclear waste disposal and all phases of the nuclear fuel cycle, from uranium recovery to enrichment to fuel manufacture to spent fuel storage and transportation.

And there’s more. The program also does environmental reviews and oversees 37 Agreement States, which have assumed regulatory authority over nuclear materials, and maintains relationships with states, local governments, federal agencies and Native American Tribal organizations.

As with all organizations, the NRC’s workload has ebbed and flowed in response to a multitude of factors. Over the years, NMSS went through several structural changes to address its workload changes. In 2006, NMSS was gearing up for an increase in licensing activity related to the processing, storage and disposal of spent nuclear fuel. At the same time, the Agreement State program was growing, requiring additional coordination with the states—a function then housed in a separate Office of State and Tribal Programs.

To meet these changes and ensure effectiveness, the NRC restructured NMSS. Some of its programs were moved, including the state and tribal programs, into the new Office of Federal and State Materials and Environmental Management Programs (FSME). NMSS retained fuel cycle facilities, high-level waste disposal, spent fuel storage, and radioactive material transportation. FSME was responsible for regulating industrial, commercial, and medical uses of radioactive materials and uranium recovery activities. It also handled the decommissioning of previously operating nuclear facilities and power plants.

The NRC’s materials and waste management workload has now shifted again. At the same time, the agency is exploring ways to reduce overhead costs and improve the ratio of staff to management.

So, NRC staff launched a working group last fall to review the organizational structure of the NRC’s materials and waste management programs. With the focus shifting to long-term waste storage and disposal strategies, and an increasing number of nuclear plants moving to decommissioning, the group recommended merging FSME’s programs back into NMSS.

NRC’s Commissioners approved that proposal last week, and the merger of the two offices will be effective October 5. We think this new structure will better enable us to meet future challenges. It will improve internal coordination, balance our workload and provide greater flexibility to respond to a dynamic environment.

Current work, functions and responsibilities at the staff level will be largely unchanged. The management structure will realign into fewer divisions, with fewer managers.

In their direction to the staff, the Commissioners asked for careful monitoring of the changes and a full review after one year. We fully expect these changes to improve our communications both inside and outside of the agency, and provide for greater efficiency and flexibility going forward.


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