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Biofuels HTR-10 Schematic

Published on July 3rd, 2008 | by Rod Adams

15

China's Second Pebble Bed Reactor Steam Plant; World's Third Commercial HTGR

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July 3rd, 2008 by  

HTR-10 Schematic There is some excitement in the nuclear focused blog world about “The World’s First Commercial High Temperature Nuclear Reactor” based partly on a recent article in Power Engineering by Jana Miller titled “Powering Up A Growing Nation”. This project in Shandong Province will be a unique plant whose reactor heat source is two containers full of spherical fuel elements, each one of which is about the size of a billiard ball.

I am a bit reluctant to call this plant a “first”, but I can get just as excited about the third, 10th or 100th plant in a progressive series of improved plants that should number 1000 reactors or more.

The plant, designated as HTR-PM, will be a 200 MWe pebble bed reactor heated steam plant with two reactors, each with a single steam generator (boiler) feeding a single turbine. The plant will be built in Rongchen City on a site large enough to host series of perhaps 10-12 similar plants. In that area of China, there are hundreds of older coal fired power plants generating 50-300 MWe each.

The HTR-PM is a carefully watched project that uses technology old enough to be new again. The concept was introduced in the late 1940s by Farrington Daniels who suggested the idea of combining uranium with graphite, which is a high temperature substance that also moderates neutrons, into small, discrete units that could be piled into a simple, shielded container.

This concept, known as the Daniels’ Pile, was a bit before its time. The material science available in the late 1940s could not provide the tight, vapor-proof coatings needed to ensure that all fission by-products remained sealed in the pebbles in all core conditions. That problem was addressed and overcome by the German project known as the Arbeitsgemeinschaft Versuchsreaktor (AVR) run in Julich from 1959-1988.

General Atomics provided Pebble circa 1994The AVR started operating in 1961, provided power to the grid in 1967 and was shut down after many years of testing and fuel developmental improvements in 1988.

The first commercial high temperature reactors

The AVR did not operate in isolation; during the same time there was a high temperature gas cooled reactor, built by Gulf General Atomics (now just General Atomics) and operated in the US at Fort St. Vrain. That HTGR was based on fuel in a different form, but it used fuel particles surrounded by layers of graphite and silicon carbide to provide the capability of operating at a significantly higher temperature and thermal efficiency than the conventional light water reactors.

I had the opportunity to visit General Atomics in 1994, before they decommissioned the fuel manufacturing facility that produced the Ft. St. Vrain fuel, and they gave me the pebble that you see here as a keep sake. It has been on my desk ever since.

The German group operating the AVR also built a commercial unit – Thorium High Temperature Reactor (THTR) – using fuel pebbles where some pebbles contained uranium-235 and others contained thorium-232. This fuel combination intrigued the designers because thorium is about 3-4 times as abundant as uranium, but it needs to be exposed to neutrons in a reactor before it can be used as fuel.

Unfortunately, though they were both commercial reactors, neither the Ft. St. Vrain HTGR nor the THTR operated for very long and neither led to any immediate successors. Good ideas, however, often incubate in the minds of problem solvers that see all of the potential and determine ways to solve the problems for another try.

China’s New High Temperature Reactors (HTR)

In 2000, the AVR rose up like a Phoenix in a new location at Tsinghua University with a new name – HTR-10. The Chinese had recognized the potential of the design and purchased essentially all of the makings including technical drawings, machinery, and consulting engineering services from the German owners. In January 2003, the HTR-10 began critical operations and testing. I have a number of friends and colleagues who have visited the facility and have been impressed. You can have a similar experience by watching a video produced by the Australian Broadcasting System titled Nuclear China.

There are many things about pebble bed reactors that fascinate me, but one of them is the fact that they can be configured to be able to withstand a complete loss of cooling without causing any core damage. As long as each reactor unit produces less than 400 MW of thermal energy, operators can turn off the cooling circulators and walk away knowing that the plant will heat up a bit, shut itself down, and never exceed a temperature at which any fuel damage will occur. Now that is a hot idea whose time has come!

The HTR-PM is capable of providing very high quality steam, identical to the steam produced in the most efficient coal fired power plants. In fact, Jim Holm has suggested that we could short cut the lengthy nuclear plant construction process by replacing boilers in existing steam plants with high temperature pebble beds.

It is one hell of a way to help solve the world’s most pressing energy challenge – how do we replace the low cost heat that coal provides to enable our modern economy without creating emissions that may overheat our planet?

Photo credits HTR-10 Schematic and simulated pebble fuel element from Rod Adams archives under creative commons.

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About the Author

loves and respects our common environment, but he has a fatal flaw in the eyes of many environmentalists -- he's a huge fan of atomic energy. Reduce, reuse, and recycle have been watchwords for Rod since his father taught him that raising rabbits is a great way to turn kitchen scraps into fertilizer for backyard fruit trees and vegetable gardens. They built a compost heap together in about 1967, when he was 8 and when Earth Day was a mere gleam in some people's eye. During his professional career, he has served in several assignments on nuclear submarines, including a 40-month tour as the Engineer Officer of the USS Von Steuben. In 1994, he was awarded US patent number 5309592 for the control system for a closed-cycle gas turbine. He founded Adams Atomic Engines, Inc. in 1993, started Atomic Insights in 1995, and began producing the Atomic Show Podcast in 2006. He is currently an active duty officer (O-5) in the US Navy. He looks forward to many interesting discussions.



  • http://ballroom.com billrowe

    The best and also old reactor concept is the molten salt breeder reactor where the fuel is molten and circulates through heat exchangers to transfer heat to faorly conventional plant backends. THe reactor operates at essentially atmospheric pressure and practically never requires refueling over the life of the plant and pptentially could generate more fuel than it consumes and/or could destroy the longest lived radiaoactive fission products in the enerfy generation process. Many variations are possible with many sizes and some small ones with high degrees of modular factory production. Like pebble bed concepts such promising ideas are difficult for a private company to invist the billions of dollars to bring to commercialization=== governments need to get involved as was the case for the curent commercial reactor concepts.

  • http://www.clrlight.org Tom Blakeslee

    The article casually mentions the shutdown of the German reactor without mentioning the reason. The “fail-safe” reactor broke a jammed pebble about a week after the Chernoble accident and released dangerous amounts of radiation. They tried to cover it up the accident but were discovered. That’s why the project was cancelled!

    http://www.nirs.org/factsheets/pbmrfactsheet.htm

    The world has a dangerous enough collection of dangerous waste already.

    The power of atomic decay can be safely and cleanly harnessed using EGS geothermal technology.

    http://www.renewableenergyworld.com/rea/news/reinsider/story?id=53467

  • http://www.clrlight.org Tom Blakeslee

    The article casually mentions the shutdown of the German reactor without mentioning the reason. The “fail-safe” reactor broke a jammed pebble about a week after the Chernoble accident and released dangerous amounts of radiation. They tried to cover it up the accident but were discovered. That’s why the project was cancelled!

    http://www.nirs.org/factsheets/pbmrfactsheet.htm

    The world has a dangerous enough collection of dangerous waste already.

    The power of atomic decay can be safely and cleanly harnessed using EGS geothermal technology.

    http://www.renewableenergyworld.com/rea/news/reinsider/story?id=53467

  • Chris Bell

    Hi JDinaustin,

    This is coming from a Nuclear Dullard!

    You Da’ Man!!!!

    I think I understand the direction of your post, and being an Engineer I easily grasp the Math. All of the other actions and interactions begin to blur my vision.

    Dumb question:

    Won’t a balanced Nuclear based generation capability require the use of several different type of reactors? Does you well informed post essentially mean that Pebble Bed Reactors are not a good solution to the “heavy lifting” aspect of Nuclear Power generation?

    Again, a dullard…

    CJB

  • Chris Bell

    Hi JDinaustin,

    This is coming from a Nuclear Dullard!

    You Da’ Man!!!!

    I think I understand the direction of your post, and being an Engineer I easily grasp the Math. All of the other actions and interactions begin to blur my vision.

    Dumb question:

    Won’t a balanced Nuclear based generation capability require the use of several different type of reactors? Does you well informed post essentially mean that Pebble Bed Reactors are not a good solution to the “heavy lifting” aspect of Nuclear Power generation?

    Again, a dullard…

    CJB

  • http://redgreenandblue.org Rod Adams

    JDinaustin:

    Fine comment. In addition to U-238, the harder spectrum that you propose would also make Th-232 available as fuel. The world’s supply of Th-232 is about 3-4 times as large as its U-238 supply, so heavy metal fuel supplies will last 3-4 times the forever that you foresee.

    That’s a thought that must cause scarcity driven commodity suppliers NUTS.

    No wonder there is such a widespread and well-funded effort to keep the knowledge of fast spectrum fission tied up in knots.

  • http://redgreenandblue.org Rod Adams

    JDinaustin:

    Fine comment. In addition to U-238, the harder spectrum that you propose would also make Th-232 available as fuel. The world’s supply of Th-232 is about 3-4 times as large as its U-238 supply, so heavy metal fuel supplies will last 3-4 times the forever that you foresee.

    That’s a thought that must cause scarcity driven commodity suppliers NUTS.

    No wonder there is such a widespread and well-funded effort to keep the knowledge of fast spectrum fission tied up in knots.

  • JDinaustin

    Pebble Beds can be run as fast spectrum reactors as well obliviating the need to have seperate breed reactors. By replacing the pyrographite with more silicon carbide the moderation of each pebble is reduced hardening the neutron spectrum. Helium is already transparent to neutrons. once you have a fast spectrum a core can be configured to give a Keff of 1.0+ therefore breeding its own fuel as it runs. If the design is good the reactor “Breeds and Feeds” meaning over a 30+ year life time the Keff of the reactor never swings negative bacause the reactor is in balance burning as much as it is producing. All transuranics are fissile in a fast spectrum eliminating the higher actinides, transuranics and most long lived fission products by the n-p capture route. wastes from a fast reactor fuel cycle are only radioactive for 600 years not tens of thousands like the current thermal spectrum once through cycle. Once a fast reactor is loaded with its initial fuel it never has to be feed enriched U or Pu again it breeds all its own fuel from the natural U238 in its pebbles, after the core life is expended which can be upwards of 30 years in a fast core the remaning U238 and all the isotopes of Pu can be recycled along with the amount of natural U238 consumed in the breeding process added back in to new pebbles while the now fission product waste is virtified and stored for 600 years in a geologic repository to cool. using a fast spectrum allows all the energy in natural uranium to be used not just 7% like a thermal spectrum reactor does. there is enough Pu and U235/238 in the 50000lbs of spent fuel from the existing reactor fleet to run fast reactor for a century at current power levels with out having to mine a single gram of new uranium. Peak uranium is a myth spread by those who dont understand how reprocessing and fast reactors work. even if the US decided to stay with the once through cycle the Japanese are commercializing the process to remove uranium from seawater currently they can get a kilo of yellow cake for 25000 yen thats $260 American. The fuel cost for a PWR are 3% of the total electricity costs. last i checked mined NU was $70 a kg and nuclear power was wholesaleing for 1.5c a kwr here in the states. even moving to $260 a kilo for fuel since fuel is only 3% of the total cost the total cost would only rise 3×3% this is nuclears strongest advantage even at 10X current market rates the cost would only increase 30% still putting nuclear cheaper than a natural gas plant when gas is $8 MMBtu. Gas is trading at $12MMbtu btw. the oceans have billions of tones of natural uranium in them and the Japanese can get at it for 3 times the market rate. No nuclear power is the answer with or without fast reactors. As I just have shown even current PWR using the once through cycle can be cost competetative even at $700+ a kg for yellow cake. given that an almost unlimited supply can be had from seawater at $260 a kilo fuel is not the issue. the economics are even stronger for a fast reactors since it uses 60 yes 60 times less yellow cake per watt hour because they can burn all the U238/235 +Pu239 +Americium +Curium +Neptunum where a PWR can only burn U235 and some of the PU239 it creates.The higher tranuranics are left in the spent fuel being relativly unfissile in a thermal spectrum. given that a fast reactor only needs natural uranium plus 20%PU239 once at start up after which only natural uranium be added to keep the reactor running at a consumption rate 60 times less than a thermal reactor one can say that natural uranium prices can increase by 60 times and a fast reactor will still equal on a dollar per watt basis a thermal spectrum reactor. 60 times 70 is $4200 a kg. At that price mining crustal granite that is 4ppm Uranium anywhere on the planet would be economical give than currently in-situ leaching of granites is economic at 500 ppm and $70 a kg. No were not going to run out of uranium ever.

  • JDinaustin

    Pebble Beds can be run as fast spectrum reactors as well obliviating the need to have seperate breed reactors. By replacing the pyrographite with more silicon carbide the moderation of each pebble is reduced hardening the neutron spectrum. Helium is already transparent to neutrons. once you have a fast spectrum a core can be configured to give a Keff of 1.0+ therefore breeding its own fuel as it runs. If the design is good the reactor “Breeds and Feeds” meaning over a 30+ year life time the Keff of the reactor never swings negative bacause the reactor is in balance burning as much as it is producing. All transuranics are fissile in a fast spectrum eliminating the higher actinides, transuranics and most long lived fission products by the n-p capture route. wastes from a fast reactor fuel cycle are only radioactive for 600 years not tens of thousands like the current thermal spectrum once through cycle. Once a fast reactor is loaded with its initial fuel it never has to be feed enriched U or Pu again it breeds all its own fuel from the natural U238 in its pebbles, after the core life is expended which can be upwards of 30 years in a fast core the remaning U238 and all the isotopes of Pu can be recycled along with the amount of natural U238 consumed in the breeding process added back in to new pebbles while the now fission product waste is virtified and stored for 600 years in a geologic repository to cool. using a fast spectrum allows all the energy in natural uranium to be used not just 7% like a thermal spectrum reactor does. there is enough Pu and U235/238 in the 50000lbs of spent fuel from the existing reactor fleet to run fast reactor for a century at current power levels with out having to mine a single gram of new uranium. Peak uranium is a myth spread by those who dont understand how reprocessing and fast reactors work. even if the US decided to stay with the once through cycle the Japanese are commercializing the process to remove uranium from seawater currently they can get a kilo of yellow cake for 25000 yen thats $260 American. The fuel cost for a PWR are 3% of the total electricity costs. last i checked mined NU was $70 a kg and nuclear power was wholesaleing for 1.5c a kwr here in the states. even moving to $260 a kilo for fuel since fuel is only 3% of the total cost the total cost would only rise 3×3% this is nuclears strongest advantage even at 10X current market rates the cost would only increase 30% still putting nuclear cheaper than a natural gas plant when gas is $8 MMBtu. Gas is trading at $12MMbtu btw. the oceans have billions of tones of natural uranium in them and the Japanese can get at it for 3 times the market rate. No nuclear power is the answer with or without fast reactors. As I just have shown even current PWR using the once through cycle can be cost competetative even at $700+ a kg for yellow cake. given that an almost unlimited supply can be had from seawater at $260 a kilo fuel is not the issue. the economics are even stronger for a fast reactors since it uses 60 yes 60 times less yellow cake per watt hour because they can burn all the U238/235 +Pu239 +Americium +Curium +Neptunum where a PWR can only burn U235 and some of the PU239 it creates.The higher tranuranics are left in the spent fuel being relativly unfissile in a thermal spectrum. given that a fast reactor only needs natural uranium plus 20%PU239 once at start up after which only natural uranium be added to keep the reactor running at a consumption rate 60 times less than a thermal reactor one can say that natural uranium prices can increase by 60 times and a fast reactor will still equal on a dollar per watt basis a thermal spectrum reactor. 60 times 70 is $4200 a kg. At that price mining crustal granite that is 4ppm Uranium anywhere on the planet would be economical give than currently in-situ leaching of granites is economic at 500 ppm and $70 a kg. No were not going to run out of uranium ever.

  • http://ballroom.com billrowe

    I used to be really gungho about pebblebed reactors because of the walkaway safety features. I still think they are great in many ways.Small size makes them amenable to much greater factory construction and delivery to site.But I expect it would take decades to establish the licensing requirements for such plants (for example would the typical containment housing be eliminated for these plants since they are extremely safe? Or would this ultimate safety feature be retained?This would severely limit any backfit to existing plants.And building factory production capacity would also take many years. So I would not count on pebble bed reactors implementation schedule being shorter to help the CO2 problem. Also,I have a concern about a primary selling feature of PBR’s: it is difficult (no existing capability) to easily reprocess the spent fuel pebbles to remove the plutonium to proliferate bombs. Sounds great, but if nuclear is ever to be a large enough factor in reducing CO2,natural Uranium mine reserves would be depleted way too fast to be a long term solution.For that the spent fuel would have to be reprocessed to recover the usable Uranium and plutonium,and used in breeder reactors that generate more usable uranium/plutonium than they use. Well you see the long term problem with PBR fuel being difficult to reprocess. THere is a better nuclear reactor system—the molten salt breeder which is a socalled 4th generation concept that is receiving almost no development funding. It is as safe as PBR and undergoes inherent continous online breeding of new fuel,drastically extending the potential energy available from finite natural uranium and thorium reserves.It is not being funded because it would require billions of development funding which current nuclear supply companies are unwilling to invest since the existing designs are accepted by the public and governments and current natural uranium supply is high (for current number of nuclear power plant)and prices are low.However,a long term view would say its best to develop and implement this technology now to reduce the amouint of highly radioactive waste materials and reprocessing future backlog.Alas, our societal systems do not favor the long range better plan.

  • http://ballroom.com billrowe

    I used to be really gungho about pebblebed reactors because of the walkaway safety features. I still think they are great in many ways.Small size makes them amenable to much greater factory construction and delivery to site.But I expect it would take decades to establish the licensing requirements for such plants (for example would the typical containment housing be eliminated for these plants since they are extremely safe? Or would this ultimate safety feature be retained?This would severely limit any backfit to existing plants.And building factory production capacity would also take many years. So I would not count on pebble bed reactors implementation schedule being shorter to help the CO2 problem. Also,I have a concern about a primary selling feature of PBR’s: it is difficult (no existing capability) to easily reprocess the spent fuel pebbles to remove the plutonium to proliferate bombs. Sounds great, but if nuclear is ever to be a large enough factor in reducing CO2,natural Uranium mine reserves would be depleted way too fast to be a long term solution.For that the spent fuel would have to be reprocessed to recover the usable Uranium and plutonium,and used in breeder reactors that generate more usable uranium/plutonium than they use. Well you see the long term problem with PBR fuel being difficult to reprocess. THere is a better nuclear reactor system—the molten salt breeder which is a socalled 4th generation concept that is receiving almost no development funding. It is as safe as PBR and undergoes inherent continous online breeding of new fuel,drastically extending the potential energy available from finite natural uranium and thorium reserves.It is not being funded because it would require billions of development funding which current nuclear supply companies are unwilling to invest since the existing designs are accepted by the public and governments and current natural uranium supply is high (for current number of nuclear power plant)and prices are low.However,a long term view would say its best to develop and implement this technology now to reduce the amouint of highly radioactive waste materials and reprocessing future backlog.Alas, our societal systems do not favor the long range better plan.

  • M. Wang

    Depending on China’s ability to solve the engineering problems in a brand new design, volume deployment can be expected some 10 to 20 years in the future. I have been trying to lobby Vice Premier Wu for more urgent investment in this technology a few years back, but none of the government economists considered it worth the risk back then. They also did not forecast $140 per barrel of oil, however, and now the decision makers see a different calculus.

    The South African design is similar and not any more mature than the Chinese one. Remember, the principle of the pebble bed design is extremely simple. It is the safety engineering and commercial economics issues that will take time. Unfortunately, neither the South Africans nor the Chinese have much experience in these areas, but given China’s greater resources and much greater needs for this reactor, my bet is on the Chinese to popularize it.

  • M. Wang

    Depending on China’s ability to solve the engineering problems in a brand new design, volume deployment can be expected some 10 to 20 years in the future. I have been trying to lobby Vice Premier Wu for more urgent investment in this technology a few years back, but none of the government economists considered it worth the risk back then. They also did not forecast $140 per barrel of oil, however, and now the decision makers see a different calculus.

    The South African design is similar and not any more mature than the Chinese one. Remember, the principle of the pebble bed design is extremely simple. It is the safety engineering and commercial economics issues that will take time. Unfortunately, neither the South Africans nor the Chinese have much experience in these areas, but given China’s greater resources and much greater needs for this reactor, my bet is on the Chinese to popularize it.

  • Bobcat

    Rod,

    Recycling older steam plants with pebble bed reactors sounds interesting indeed. But I do have a question for you. How long will it take for this type of reactor to be ready and be produced in significant quantities to really make a difference with global climate change? Are we talking years or decades?

    When I Google pebble bed reactors I come up with a lot of stories from South Africa about the problems and cost overruns they are having with this type technology.

  • Bobcat

    Rod,

    Recycling older steam plants with pebble bed reactors sounds interesting indeed. But I do have a question for you. How long will it take for this type of reactor to be ready and be produced in significant quantities to really make a difference with global climate change? Are we talking years or decades?

    When I Google pebble bed reactors I come up with a lot of stories from South Africa about the problems and cost overruns they are having with this type technology.

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