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.

“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.