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Neutron dance: What happens at the heart of a nuclear reactor?

The views expressed are those of the author and are not necessarily those of Scientific American.


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EPFL, Switzerland, Japan, neutron, RPIAs officials in Japan deal with the accumulation of radioactive seawater near the devastated Fukushima Daiichi nuclear power plant in the wake of last month’s earthquake and tsunami, the U.S. Department of Energy is investing in fundamental research it hopes can be used to build safer nuclear reactors and avoid reactor emergencies.

The department’s Nuclear Criticality Safety Program (NCSP) on Wednesday awarded $1.5 million to researchers at Rensselaer Polytechnic Institute (RPI) in Troy, N.Y., for a new nuclear engineering research program and laboratory dedicated to the careful measurement and analysis of how neutrons interact with different materials around them. Nuclear criticality refers to a sustained nuclear fission chain reaction.

Part of the NCSP’s charter is to ensure that nuclear material is stored safely and securely to reduce the threat of a criticality accident, during which an unintended critical reaction releases a dangerous surge of neutron radiation. "Doing this requires calculations of the different scenarios when you store materials," says Yaron Danon, the nuclear engineering professor heading up the research. "Let’s say you have a dry cask [of radioactive waste] or you are storing fresh material that hasn’t already been used in a reactor. If it’s suddenly flooded with water, for example, what will happen?"

Accurate predictions can be made by knowing the basic properties of how the neutrons and gamma rays will interact with the metals, composites and other materials in their surrounding environment. "An analogy: If you want to calculate how an oven will heat, you need to know the heat transfer properties of the materials," he adds. "We are doing the same thing at the level of nuclear interaction."

The hope is that this study of basic nuclear interactions will enable more accurate predictions of energy production and shielding effectiveness in a working nuclear reactor. More specifically, the research is expected to produce data that would, for example, help nuclear scientists and engineers more accurately inventory the amount of fissile material in a given nuclear fuel rod and predict how much energy that rod might release. "This knowledge isn’t going to change the design of a reactor dramatically, but it’s going to improve it," adds Danon, director of RPI’s Gaerttner Linear Accelerator Laboratory.

RPI researchers will use a linear accelerator on campus to produce neutrons for study. The data produced will be available for engineers designing new reactors and facilities as well as those looking at storage issues and disposal of spent nuclear fuel—anyone who deals with neutron interactions with different materials. These probabilities, once measured and validated, will be made public and hopefully used by engineers and scientists around the world as inputs in a wide range of engineering models and simulations.

Image of CROCUS Reactor used for research at the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland courtesy of Rama, via Wikimedia Commons





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  1. 1. sjn 5:54 am 04/22/2011

    This is a pretty sad commentary on US nuclear engineering departments.
    This seems to be pretty basic knowledge if you’re designing reactors, temporary storage pools or long term storage. Where has all the subsidized research, national labs, etc been for the last 40 years if you’re starting such basic data gathering on neutron & other high energy radiation interactions with common design materials at such a late date late date. There has got to be more to this research than described in this article, or else you’re telling us engineers really don’t have the basic data to estimate design safety.

    Link to this
  2. 2. ennui 1:40 am 04/23/2011

    They should,look into switching over to the system of Gravity Control for generating power.
    It is based on the technology, used by the Flying Saucer, which was discovered and patented.
    The spheres under a Flying Saucer are the Propulsion UInits (PUs) and can lift a One Hundred ton vehicle off the ground and beyond.
    They can also be used to lift a One Hundred ton weight in a Silo 1000 feet high.
    A Power Station would consist of two Silos, side by side.
    In Silo #1 the PU would be powered externally the first time to push the weight to maximum height.
    Once at the top, the power to the PU would disconecct, the weight would come down, activating the generator(s) and powering the PU in Silo #2. When the weight in Silo #1 nears bottom, Silo # 2 takes over the work and repowers the PU in Silo #1.
    The trick used by the technology is that the PU is (e.g) charged with 1000 Watts.
    That is released in one millisecond or faster.
    It makes it act like a 1000 Kilowatt, 1.333 HP force.
    A Power Station would cost a fraction of a Nuclear Installation and would be run by a few elecricians.
    It can be built at any size from Micro to Gigawatt.
    Power at 1 cent per Kilowatt or less at any place.
    No pollution, radiation, no water needed.

    Link to this
  3. 3. jack.123 7:12 pm 04/26/2011

    I very much hope that we learned from what happened in Japan.The two things I hope we now know is first it is allot better to release a few large clouds of radioactive hydrogen then letting it build up in a containment vessel till it explodes and releases thousands of times as much more radiation,and that we need to develop immediate shut down procedures even at that risk of some radiation being released by it.

    Link to this

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