Saturday, December 23, 2006

PBR advantages are attractive


Pebble bed reactor fuel spheres
    1. Pebble bed reactor (PBR) technology is safe; the reactor can not melt down. While today's reactors are safe due to multiple, redundant, engineered shutdown, cooling, and containment systems, the PBR is safe because the basic physics increases neutron absorption if the temperature rises.

    2. PBR’s are cooled by helium gas, which is chemically inert and not radioactive, so the high temperature helium gas can directly power turbines to generate electricity at 45 percent efficiency, compared to typical 33 percent efficiencies.

    3. The 900 to 950 degree Celsius heat enables efficient thermo-chemical production of hydrogen and disassociation of water into hydrogen and oxygen. Although hydrogen per se is unlikely to be a fuel of the future, it is readily combined with recycled CO2 such as from coal power plants to create methanol. Methanol is a suitable fuel for internal combustion engines and fuel cells, and unlike hydrogen it can be distributed through the existing infrastructure of pipelines and gas stations used today for petroleum derived fuels, says Nobel-prize winning chemist George Olah in his 2006 book, “Beyond Oil and Gas: The Methanol Economy.”

    4. PBR’s are modular, costing about $200 million for a 100 megawatt unit. Utility companies can add modules as demand increases and investment capital becomes available, rather than risking a 2 billion expenditure for a 1,000 megawatt large power plant. The ROI will be in the 15-25 range, provided Congress provides a path through the legal gauntlets that discourage capital investment in nuclear power.

    5. PBR’s can be built in factories, shipped by truck and rail, and assembled on site. This permits production line economies, strong quality controls, and continuing improvements.

    6. China has a pilot PBR running. China has announced firm plans to build a full size 190 megawatt PBR which if successful will be expanded by 18 further modules creating a 3,600 megawatt power station in Rongcheng, China. South Africa is also building a PBR which they hope to have operational by 2012.

    7. The U.S. is funding some basic research on Generation IV reactors, e.g. PBR’s at Idaho National Laboratories, but no funds have been appropriated to build a pilot plant, although the 2005 Energy Policy Act authorizes $1.25 billion for this.

    I'll treat these topics in depth in future posts.

    11 comments:

    Anonymous said...
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    Stewart Peterson said...

    What about waste?

    Robert Hargraves said...

    On the positive side, the radioactive used fuel pebbles are already in a form to be put into long term storage. One negative is that the very hard coatings make fuel reprocessing to recover plutonium for future fuel impractical, but this also guards against proliferation. All nuclear reactors generate waste, which does have to be managed. I'll try to write about waste later on.

    Jim Baerg said...

    Re: "Although hydrogen per se is unlikely to be a fuel of the future"

    That's true if you mean for use directly for transportation & other mobile uses. However, hydrogen can be piped around like natural gas is, or the CO/H2 mix made by reacting steam & coal was. Since the natural gas pipelines aren't necessarily compatible with hydrogen, the use of nuclear produced hydrogen for such things as gas stoves with expand only slowly.

    Dana Robinson said...

    Good Morning Robert Hargraves: This is a Dana Robinson, a member of a small group here at Heritage Heights in Concord, NH calling ourselves The Concord Energy Policy Group. My personal interest is how to help educate and persuade our NH Legislators to bring New Hampshire back into the real world and include in their new Energy Policy Statement a positive reference to our Seabrook Nuclear Power Plant. Are you following overall Energy-related developments in New England - such as the 2006 Market Report of ISO New England concluding that within the next 5 years we will need an additional 400 MW of Electric Power? Have you ever been involved in considering what impact the 2nd Reactor at Seabrook would have for the Northeast Region?

    Regards,

    Dana Robinson

    Robert Hargraves said...

    I have not read the report. I did try to schedule my PBR presentation to the NH state energy policy group last year, but they only wanted to hear about near-term solutions.

    james said...

    What companies will be or are building the pebble bed reactors?

    Proctor, ALabama said...

    Too bad about the head-in-the- sand mentality of many politicians,such as those in NH. Near-term results get next-term votes. Longer range plans [and action] do not, such as in 1995 when additional oil drilling was quashed by the administration of the day. We'd be reaping the bountiful fruits of that today, 2008.
    Proctor, Alabama

    Wayne said...

    In regards to nuclear waste, since the PBR implements "deep-burn" technology, shouldn't most of the nuclear wastes, namely actinides, be destroyed by allowing the TRISO fuel to be irradiated by thermal neutrons?
    Because of the incredible thermal/stress resistance of the carbon TRISOs, nuclear fuel and wastes within the TRISOs can remain inside the reactor longer than traditional fuels, thus destroying the long-living radioactive isotopes.

    Robert Hargraves said...

    Wayne, tell us more about deep burn technology. Do you have a reference?

    I understood that the PBR uses somewhat more enriched uranium than LWRs, and I suppose the TRISO fuel might allow somewhat more fission product containment. I don't think it runs nearly long enough to consume much of the actinide wastes, which it would continue to manufacture from the U-238.

    Wayne said...

    You can look up deep-burn technology on Google for more information. However, from my understanding deep-burn tech generally refers to any cladding or fuel material that can withstand tremendous amounts of heat and irradiation, while retaining excellent mechanical properties and retain fission products. The TRISO particle is one example because its made up of layers of carbon (possibly pyrolytic carbon because of its excellent properties) and silicate.
    Therefore, with deep-burn materials such as the TRISO, the PBR's fuel pebbles can remain inside the core under a high neutron flux for a long period of time. This will allow the transmutation of actinides and thus destruction of must nuclear wastes.
    Deep burn tech can also be used in virtually any VHTR (Very High Temperature Reactors). Moreover, there are PBR designs that undergo once-through cycles and destroy the actinides.
    Below is a link that describes deep-burn.

    http://cat.inist.fr/?aModele=afficheN&cpsidt=14772073

    Deep-burn technology isn't the only process to remove the waste. There are a few different re-processing methods that can be used. However, for the PBR deep-burn should be sufficient.