U.S. NRC Blog

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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.

12 responses to “NRC Science 101 – About Spent Nuclear Fuel Part II

  1. profstanblog May 9, 2016 at 11:22 am

    Where and when did that Beagle experiment occur please? How difficult is it to reach the Pu filter within the spent fuel facility?

  2. Tom Clements February 27, 2015 at 8:32 am

    Thank for using the legally defined term “spent fuel” and not some other extra-legal term for spent fuel. A big concern about “consolidated” storage instead of dry cask storage at reactor sites is that such highly radioactive waste would be a tempting stock for companies, like AREVA, aiming to profit from reprocessing of that spent fuel. The article notes that reprocessing has not been an option, which remains the case due to cost and technical reasons and that it magnifies the waste problem. Those backing consolidated storage at the Savannah River Site (SRS) actually wrote a report saying the goal with consolidated storage was reprocessing. Strategically that was a huge mistake as the community pushed back, not wanting yet more HLW at SRS, and the SRS Citizens Advisory Board (a FACA committee on SRS clean-up) has twice overwhelmingly voted that no commercial spent fuel be brought to SRS. If consolidated storage is again used as a foot in the door for reprocessing at SRS there will be strong opposition. On-site, dry storage is happening at a fast rate and should be the chosen stoarge method until a longer-term option is developed. Tom Clements, Director, SRS Watch, Columbia, South Carolina

    • Public Pit Bull February 27, 2015 at 1:50 pm

      Really, Tom, what a lame excuse for not properly taking care of a public safety threat. It may be a backdoor way of getting a foot in the door of reprocessing, you say. Are you saying that you would just let the feds jump in and start reprocessing this dangerous waste if it was consolidated in a remote desolate area of this country?! Reprocessing will not happen in this country no matter where the waste is located and you know it! Why are you standing in the way of a perfectly sane way of dealing with the buildup of this waste around the country and especially near large metro areas. I guess your solution involves guess, hope, and wait for another half century for a permanent repository that will also probably never be built. I am for taking long overdue action to get this dangerous stuff out of our backyards!

  3. Erica Gray February 26, 2015 at 9:08 pm

    Why has the NRC allowed the industry to put the cart before the horse?
    The truth is we don’t know how well HB spent fuel will hold up long term.
    I was told at one NRC meeting, only 1 dry cask has ever been opened and examined since the industry started using dry casks and that was one with lower burn up fuel.
    I would like to see the NRC produce that document to prove even one has been open and examined.

    The breaks need to be applied to the nuclear industry. They shouldn’t be allowed to continue making more of this waste when they still don’t know how to manage what they’ve already produced.
    Plus there is no where to store it safely for thousands of years.
    Now the industry wants to push their “new and improved” reactors.
    Give me a break!
    Different reactor, but produces the same problematic waste.


    The potential need to store Spent Nuclear Fuel (SNF) for many decades will have a near-term and potentially significant impact on nuclear plant licensing and operations. While dry storage of lower burnup SNF [less than 45 gigawatt days per metric ton uranium (GWD / MTU)] has occurred since 1986, dry storage of high burnup SNF is more recent. Approximately 200 dry storage casks now have been loaded with at least some high burnup SNF, and almost all SNF being loaded in the U.S. is now high burnup. Industry needs additional data on high burnup SNF under typical storage conditions. In response to DOE R&D project initiation, the Electric Power Research Institute (EPRI, project lead) in concert with U.S. national laboratories are developing and implementing this test plan to collect data from an SNF dry storage system containing high burnup fuel. This Test Plan for the High Burnup Dry Storage Research Project (HDRP) outlines the data to be collected, the high burnup fuel to be included, and the storage system design, procedures, and licensing necessary for implementation. The Test Plan results are anticipated to provide confirmatory data to support license extensions of ISFSIs containing high burnup spent fuel and to evaluate the integrity of the dry storage systems. Planned models and tests are intended to supply a large amount of data relevant to the assessment of the safety of long-term storage followed by transportation.

  4. CaptD February 26, 2015 at 7:17 pm

    I’ve already suggested that the NRC offer a Million Dollar Prize for the best way to “solve” the nuclear waste storage problem” for the next 50 years, so please consider this idea as my “low cost” solution to America’s “long term” radioactive waste storage problem:

    Make use of our Military Testing Bases and or our MOA’s (Military Operation Area’s) out west, which are really huge tracts of land (think tens of thousands of acres) used ONLY by the military and already secured by them 24/7!

    Placing these very large (heavy) concrete casks in a poke-a-dot pattern will allow for at least 50 to 100 years of storage, safe from everything except a War, (in which case every reactor is just as vulnerable) and then revisit the storage problem then; at which time, probably a future solution will allow for an even better, lower cost “final solution”…

    Because these casks would be very large and all look alike nobody would know what was in any one of them, which would be yet another level of security for the casks containing even higher levels of nuclear waste! An ideal outside coating for these casks would be similar to the spray-on “bed liner” used for pickup trucks that not only prevents rusting and or damage for the life of the vehicle but would also seal the casks to prevent leakage of any kind!

    Hopefully these casts would be similar in size to a large shipping container so that existing material handling equipment could be used to load, unload and or move them about without “inventing” a mega hauler vehicle. By keeping the “footprint” of these casks similar to a large 40 foot container, the stacking and or placement of them might also be semi or fully automated which would not only save money but again keep the exact location of any specific cask secret! The monitoring of these casks 24/7/365 could even be done via satellite since these casks are similar in size to rocket launchers which are easily seen from space.

    In another 50 to 100 years, storage technology will be such that, yet another lower cost solution for all this waste will be found, and then it can be considered verses continuing to using the above storage plan… Perhaps sometime In the future, a safe low cost solution like lifting it all into space via a space elevator* and then shoving it in an orbit that will send it into the SUN for final recycling will present itself…

    BTW: Area 51 (which does now actually exist officially) contains huge tracts of land that has already been used as a nuclear testing site (and is still contaminated and is now off limits to all but a few forever) which would allow all this material to effectively disappear…

    * The Space Elevator Project (LiftPort) http://liftport.com/ is something that the NRC should help fund ASAP, because it represents the best way to actually eliminate storing nuclear waste on Earth!

    First posted 10/26/12

  5. msvivphd February 26, 2015 at 5:13 pm

    The fact that during the entire nuclear era our scientists, technical people and politicians have utterly
    failed to solve the rad/waste problem means that we absolutely must stop producing this waste stream. Not only will it be dangerous for thousands of years, it is supremely irresponsible for our civilization to be leaving this kind of legacy for our descendants into the farthest future we can imagine. What gives us the right, because we wish to live elegantly and wastefully, to ruin the only planet that sustains life for everyone who comes after us? Our descendants will curse our memory.

  6. gasbuggy February 26, 2015 at 4:13 pm

    The design assumption has always been consistent with traditional planning and economics in capitalistic societies. It assumes that skilled workers will be able to maintain the operations of the spent fuel pools and the cask storage for many decades after the fuel has been removed from the fission reactors. The planning fails to take into account the evidence of the vast majority of climatologist and evolutionary biologist that planet Earth is likely rapidly heading into sixth mass extinction event due to human impacts on this planet’s life support systems. Most of the planet’s 7.22+ billion people are living in a profound state of denial regarding the gravity of the data they are coming up with.

    The above report fails to explain the failures that would take place if skilled workers and power were not present to maintain the operation of these facilities.

  7. Deb Reed February 26, 2015 at 3:04 pm

    What is the ratio, energy supply needed to boil water vs energy used to cool spent fuel?

  8. Nikohl Vandel February 26, 2015 at 2:56 pm

    #nuclearizedwater, what happens when it leaks our evaporates? I’m just thinking #fuqafukushimied #acidrain coming down eventually if it didn’t this past weekend!!!¡

    AND once the water becomes radioactive, can the water ever return to its natural, normal state?

    #thinking #shutdowndiablocanyon because that’s just too scary to live with now, especially with new designs and a renewed commitment to industry stepping up safety first!

  9. Public Pit Bull February 26, 2015 at 12:08 pm

    Very fair, balanced, and informative article. Does not minimize the threat that this spent fuel poses. I would only add that this spent fuel needs to be moved from 93 sites around the country to a much safer area, like in the middle of a military reservation, until a permanent underground spent fuel repository is built. These 93 sites become even more tempting terrorist targets as this spent fuel piles up. And a lot of this spent fuel is stored near large metropolitan areas in this country.

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