DISQUS

DaveMart · 1 year ago

Hi, Cyril R over at TOD commented that the fuel burnup is of the fissile fraction of the fuel, and so as a percentage of total uranium the burn is in fact lower than in a conventional reactor.
He did not know if reprocessing was so much easier with this design that very high eventual bun could be attained.
I wonder if you would comment on this?
Thanks

nextbigfuture · 1 year ago

From the patent for the UH reactor:
http://www.wipo.int/pctdb/en/wo.jsp?IA=WO200402...

These devices [I believe referring to normal pressure water and boiler reactors] usually are operationally marginal, assembled only a few percent over the critical mass achievable with the controls optimized. It therefore may not be possible to achieve more than a few percent burnup of the fuel in the reactor. In contrast, the hydride reactor can maintain control of the fission activity for a large excess of fuel, which permits high burnup of the available fuel. Fissile fuel burnup of at least 50% should be achievable with adequate design. The critical parameters for the initial design of the reactor and the point where the reactor finally fails to reach nuclear criticality can be estimated from work detailed in H. C. Paxton, J. T. Thomas, D. Callahan, and E. B. Johnson,"Critical Dimensions of Systems Containing U235, Pu239, and U233', Los Alamos Scientific Laboratory and Oak Ridge National Laboratory Report TID-7028 (June 1964), or by using MCNP. To a first order approximation, a 50% burnup requires about twice the minimum amount of fuel and about one half the stoichiometric amount of hydrogen to achieve initial criticality.

=========

This link is to an article on the state of nuclear plants in 2007
http://www.scribd.com/doc/2154140/ntr2007

On pages 103-112 it talks about conventional reactor burnup levels 10-50 gwd/t with potential to go to 65-100 gwd/t.

Page 131 talks about the fast breeder reactor in Russia. the BN-600 and the similar BN-800. Those with burnup levels of 150gwd/t and up to 200 gwd/t or more. Total [100%] burnup means about 930 gwd/t

The chinese HTR can get to 200gwd/t

I do not see gwd/t figures from hyperion. I will ask them

nextbigfuture · 1 year ago

Wikipedia on burnup and fissile
http://en.wikipedia.org/wiki/Burnup

http://en.wikipedia.org/wiki/Fissile

Fissile nuclides in nuclear fuels include:

Uranium-235 which occurs in natural uranium and enriched uranium
Plutonium-239 bred from Uranium-238 by neutron capture
Plutonium-241 bred from Plutonium-240 by neutron capture. The Pu-240 comes from Pu-239 by the same process.
Uranium-233 bred from Thorium-232 by neutron capture
In general, most actinide isotopes with an odd number of neutrons are fissile

"Fissile" is distinguished from "fissionable". "Fissionable" are any materials with atoms that can undergo nuclear fission. "Fissile" is defined to be materials that are fissionable by neutrons with low kinetic energy. "Fissile" thus, is more restrictive than "fissionable" — although all fissile materials are fissionable, not all fissionable materials are fissile. A few writers even restrict the term fissionable to include only fissile materials.

Notably, uranium-238 is fissionable but not fissile.

DaveMart · 1 year ago

Hi! Thanks for the reply - now I only wish I understood it! Not being an engineer means that it has to be broken down into small pieces for me - does your reply mean that the burn is around 50% of the total of the uranium, or only 50% of a very small fraction of it?
Thanks!

nextbigfuture · 1 year ago

I believe the situation is that 50% of the original uranium will be burned but the stuff that becomes U238 or the even number isotopes will not get burned. So it would involved analyzing the nuclear reaction equations to know how much would get burned and how much energy is generated from it.

I believe Hyperion can be 66% better than regular reactors now (burn 30% of original load) which would put it in the range of 65-90 gwd/t. gigawatt days per ton. I will email Hyperion Power Generation and see if they know or can clarify. I presume that Otis Peterson was precise with his wording of fissile instead of fissionable. In terms of total nuclear material I think it is in range of 6-9% which is better than the 4% or less of current reactors. the MIT pdf on advanced fuel cycles, burnup and waste that I cited had more details on the complexity of what is happening.

There do not appear to be working versions of deep burn systems. Even the current breeders are not deep burn. So there are several deep burn designs but they have not been built (accelerator driven, molten salt, integral breeder, VHTR). Current ones in the development pipeline could get to 80-200 gwd/t. 8-20% efficiency. right now we are in the 10-65 gwd/t with rare 80-150 gwd/t. 1-7% overall efficiency.

The reactors are improving, the main benefits of the Hyperion Reactors would be factory mass production, somewhat more efficient, meltdown proof with benefits for oilshale and oilsand recovery, far smaller thus able to be used in many more niches and situations and using a lot less material overall.

DaveMart · 1 year ago

Thanks Brian.
I have posted your response on TOD, as I did not have Cyril's e-mail.
Hyperion certainly seems one to watch, and if not them then some of the Japanese variants of small mass-producible reactors.

honzik · 1 year ago

It's probably worth mentioning that Uranium Hydride reactors have been around for about 50 years, with the idea going back to Edward Teller in 1956. Since then, many reactors have been built around this idea: They are called TRIGA reactors and are manufactured by General Atomics. Granted, there are some significant differences in Hyperion's and General Atomic's design, still the basic concept is quite sound, and it is not a stretch to expect Hyperion to succeed.

nextbigfuture · 1 year ago

http://reactor.reed.edu/about.html

Uranium hydride have been used as fuel elements (rods) in Triga pool reactors. the Hyperion reactor is liquid metal.

honzik · 1 year ago

I understand that. I thought you might have given another historical reference other than that Teller tried to make a bomb out of it.

nextbigfuture · 1 year ago

Honzik

I should have made this clear before. I appreciate your reference to the prior use of uranium hydride.
I was previously not complete in my historical references to the uses of uranium hydride.

You pointed out a useful addition to the validity of uranium hydride

Thanks

newpapyrus · 1 year ago

One of the major advantages of nuclear energy is that it reduces global warming. So why would you want to increase global warming by using nuclear heat for shale oil production?

Marcel F. Williams

http://newpapyrusmagazine.blogspot.com/

nextbigfuture · 1 year ago

We will stilll be using oil for many decades. Peak oil could be a problem. The US economy will need oil. This will likely be an economically profitable and beneficial transition path. Deal with CO2 with sequestering in geo structure or with new concrete.

newpapyrus · 1 year ago

Investing in more carbon dioxide polluting technologies is a bad idea, IMO.

But technologies for the renewable extraction of carbon dioxide from the atmosphere are probably less than a decade away from full commercialization. And renewable CO2 combined with cheap hydrogen produced from nuclear and hydroelectric power plants can produce gasoline, diesel fuel, methanol, jet fuel, and dimethyl ether without adding additional CO2 to the atmosphere.

But even without future aerocarbon dioxide extraction devices, the urban and rural biowaste currently produced in the US could be used to produce gasoline, diesel fuel, methanol, jet fuel, and dimethyl ether using existing technologies. And combined with hydrogen from nuclear and hydroelectric power plants, they could supply at least 30% of our current transportation fuel needs.

Combined with PHEV vehicle technology, 65% of our total transportation fuel needs could be met. Combined with methanol fuel cell technology, 80% of our current total transportation needs could be met.

Additionally, DOE reports suggest than rural biowaste could be increased substantially over the next 25 years which could lead to total independence from petroleum if combined with hydrogen from nuclear and hydroelectric facilities.

And , of course, if those extremely land efficient elevated farms ever come into fruition then substantially more renewable biomass fuel could be produced.

So there's really no need to go down the road of exploiting more carbon dioxide fossil fuel resources.

But aero carbon dioxide extraction technologies appear to be the simplest and perhaps the cheapest long term solution to the transportation fuel crisis, IMO.


Thanks for your response:-)

Marcel F. Williams

nextbigfuture · 1 year ago

the net fissile burnup rate in a light water reactor is only 30% of the original U-235 charge.

From information frmo Charles Barton
http://nucleargreen.blogspot.com/2008/04/respon...

The Wikipedia reports that 1% of the fuel mass of spent fuel is reactor grade plutonium. While U-235 would constitute >.83 percent of the fuel mass. The Wikipedia also reports, “Fissile component starts at 0.71% 235U concentration in natural uranium). At discharge, total fissile component is still 0.50% (0.23% 235U, 0.27% fissile 239Pu, 241Pu).”
http://en.wikipedia.org/wiki/Spent_nuclear_fuel

The UH reactor is not at 50% fissionable material but it still appears higher than regular lwr.

MIT has a detailed pdf on advanced fuel cycles, burnup and waste
http://dspace.mit.edu/bitstream/handle/1721.1/1...

HTR will probably start at about 80 gwd/t and go as high was 200gwd/t

The max is 1000 gwd/t for complete fissionable burnup