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

By: billrowe

billrowe — Mon, 18 Oct 2010 02:12:13 +0000

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.

By: Tom Blakeslee

Tom Blakeslee — Sat, 06 Sep 2008 20:16:22 +0000

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

By: Tom Blakeslee

Tom Blakeslee — Sat, 06 Sep 2008 20:16:00 +0000

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

By: Chris Bell

Chris Bell — Tue, 26 Aug 2008 05:43:07 +0000

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

By: Chris Bell

Chris Bell — Tue, 26 Aug 2008 05:43:00 +0000

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:

Again, a dullard…

CJB

By: Rod Adams

Rod Adams — Sat, 12 Jul 2008 14:46:09 +0000

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.

By: Rod Adams

Rod Adams — Sat, 12 Jul 2008 14:46:00 +0000

JDinaustin:

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.

By: JDinaustin

JDinaustin — Fri, 11 Jul 2008 22:47:07 +0000

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.

By: JDinaustin

JDinaustin — Fri, 11 Jul 2008 22:47:00 +0000

By: billrowe

billrowe — Thu, 10 Jul 2008 03:43:59 +0000

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.