Energy From Thorium Discussion Forum

It is currently Jul 16, 2018 3:57 am

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 18 posts ]  Go to page 1, 2  Next
Author Message
PostPosted: May 14, 2014 11:14 am 
Offline

Joined: Dec 24, 2011 12:43 pm
Posts: 219
Location: Newport Beach, CA
I guess the same question applies for low-enriched uranium, high-enriched uranium, and spent fuel. Why are these treated as significantly more sensitive materials than depleted uranium? The NRC license for commercial use of DU is basically registration. DU is used as armor, armor penetrating rounds, ballast, counterweights etc. This doesn't make sense to me given that overwhelmingly Pu-239 has been preferred for weapons use, even when HEU is easily accessible.

Am I completely off-base in thinking that it's easier in some respects to make Pu-239 via neutron bombardment of DU than it is to make HEU via centrifuge/gas diffusion? It certainly requires a lot less equipment. A non-state operator would need: a modest amount of DU; some chemicals and a chemical bath; a neutron source (e.g. hospital-grade accelerator, fusor, cyclotron etc); a generator; a forge. It may not be "easier" than stripping the little Pu-239 you can get from stolen SNF, but that's significantly harder to get a hold of. Speaking of which, I find the "threat" of a dirty bomb to be highly dubious...it probably wouldn't even cause any direct casualties.


Top
 Profile  
 
PostPosted: May 14, 2014 12:25 pm 
Offline

Joined: Dec 13, 2011 9:57 pm
Posts: 33
Hi Chrom
Bombarding DU with neutron requires a lot of neutrons (theoretically 6.02 with 23 zeros per mole), however if you have a source of neutrons such as a reactor it may be used for that pupose. Usually those reactors are designed to optimize Pu transmutation.

Because U and Pu are different elements, separate Pu from U is more easy than separate U from U and the byproduct of Pu production is energy, contrary to centrifuges which cost is very high and does not produce any valuable byproduct.

For the mentioned reasons, Pu is the prefered route instead of separate 235U at over 95%.

Thorium cycle is better because even in the two fluid design, each small amount produced is mixed with the fluoride fuel and to extract them it will be necessary centrifugation which again is more costly, equipment is more dificult to obtain and does not produce additional value.

Dirty bomb material is another topic.


Top
 Profile  
 
PostPosted: May 14, 2014 12:33 pm 
Offline

Joined: Jun 19, 2013 11:49 am
Posts: 1525
And until Britain blagged its way into the American bomb design records it used to build all its weapons from HEU, trading its domestic plutonium production to the Americans for things like Tritium.

So HEU is a very useful bomb material for a 'budget' programme without very high grade technical information.


Top
 Profile  
 
PostPosted: May 14, 2014 12:38 pm 
Offline

Joined: Aug 31, 2011 12:41 am
Posts: 28
I defer to the real experts on this site for confirmation, but I would guess that the neutron flux needed to breed sufficient 239Pu from 238U is not practically achievable outside a fission reactor of some sort. I assume the same goes for breeding 233U from thorium. If one could easily create fission-bomb-grade material in one's garage, as it were, I assume it would have been done by now.


Top
 Profile  
 
PostPosted: May 14, 2014 12:57 pm 
Offline

Joined: Dec 24, 2011 12:43 pm
Posts: 219
Location: Newport Beach, CA
NickL wrote:
I defer to the real experts on this site for confirmation, but I would guess that the neutron flux needed to breed sufficient 239Pu from 238U is not practically achievable outside a fission reactor of some sort. I assume the same goes for breeding 233U from thorium. If one could easily create fission-bomb-grade material in one's garage, as it were, I assume it would have been done by now.


Bogdan Maglich presented on the topic of U233 breeding using neutrons from a colliding beam at TEAC3. http://youtu.be/2uX1Twr9gkk

Admittedly I haven't done the math as far as how many neutrons would be required, but you don't necessarily need more than 1 kg Pu-239 to be dangerous.


Top
 Profile  
 
PostPosted: May 14, 2014 6:40 pm 
Offline

Joined: Jun 19, 2013 11:49 am
Posts: 1525
With the proliferation of high power (Relative to when all the current weapons were designed) there is some thought that you will be able to build a one-kiloton range weapon with a kilogramme of reactor grade Pu, if you have access to tritium.


Top
 Profile  
 
PostPosted: May 14, 2014 8:17 pm 
Offline

Joined: Apr 19, 2008 1:06 am
Posts: 2225
DU is the 'waste' stream of uranium enrichment, the non-fissile part, as difficult to burn as thorium. LEU is closer to weapon grade material. Enrichment is tedius work, requiring machinery and power. Only Russians at present do any enrichment of DU.
The fissile isotopes, depleted in the DU, are the real fuel in weapons or even the reactor. There is an increasing consideration of breeding, the conversion of fertile isotopes to fissile material even for nuclear power. The examples are fast reactors, under construction in Russia, India and China from DU and in LFTR from thorium in active discussion.


Top
 Profile  
 
PostPosted: May 15, 2014 9:57 am 
Offline

Joined: Dec 24, 2011 12:43 pm
Posts: 219
Location: Newport Beach, CA
jagdish wrote:
DU is the 'waste' stream of uranium enrichment, the non-fissile part, as difficult to burn as thorium. LEU is closer to weapon grade material. Enrichment is tedius work, requiring machinery and power. Only Russians at present do any enrichment of DU.
The fissile isotopes, depleted in the DU, are the real fuel in weapons or even the reactor. There is an increasing consideration of breeding, the conversion of fertile isotopes to fissile material even for nuclear power. The examples are fast reactors, under construction in Russia, India and China from DU and in LFTR from thorium in active discussion.


Okay let's start over. I've been here for a pretty long time, I know the basics of LEU/HEU/DU/Natural Uranium and how they're used/made. Given the tedium and equipment required to enrich uranium, isn't breeding from fertile-to-fissile more of a "proliferation risk" than LEU?

Thorium - it is possible but less than ideal given the decay chain of U-232.
LEU - You have 5% U-235, there is a lot of enriching left to get to weapons-grade. If you try a breeding approach you'll be getting a significant amount of fission and gammas.
Natural Uranium - There is a ton of enriching between here and weapons-grade. A breeding approach would work, you'd have an insignificant amount of fission complicating things.
Depleted Uranium - Even lower U-235 content than natural uranium. A breeding approach would be ideal.

Am I wrong?


Top
 Profile  
 
PostPosted: May 15, 2014 10:30 am 
Offline
User avatar

Joined: Nov 30, 2006 3:30 pm
Posts: 3666
Location: Alabama
Cthorm wrote:
LEU - You have 5% U-235, there is a lot of enriching left to get to weapons-grade.
Am I wrong?


Well, not wrong, but you'd be surprised how far you've gotten towards HEU (from a separative work perspective) with 2-3% LEU. It's not like you're only a few percent of the way there. You're more like 2/3rds of the way there. Check out this graph that will help you see that.

Attachment:
slide_uraniumSWperUnitFeed.png
slide_uraniumSWperUnitFeed.png [ 15.04 KiB | Viewed 4249 times ]


Here's the derivation, if you want to repeat the calculations:

Code:
feed(F) = product(P) + tails(T)
xf = concentration in feed (0.0071)
xp = concentration in product (0.0071 < xp < 1.0)
xt = concentration in tails (0 < xt < 0.0071)

xf*F = xp*P + xt*T
xf*F = xp*(F - T) + xt*T
T*(xp - xt) = F*(xp - xf)
T/F = (xp - xf)/(xp - xt) = tails-to-feed ratio

V(x) = (1 - 2x)*ln((1 - x)/x)

SWU = P*V(xp) + T*V(xt) - F*V(xf)
SWU = (F - T)*V(xp) + T*V(xt) - F*V(xf)
SWU = F*V(xp) - F*V(xf) + T*V(xt) - T*V(xp)
SWU = F*(V(xp) - V(xf)) + T*(V(xt) - V(xp))
SWU = F*(V(xp) - V(xf)) + F*(T/F)*(V(xt) - V(xp))
SWU/F = (V(xp) - V(xf)) + (T/F)*(V(xt) - V(xp))


Top
 Profile  
 
PostPosted: May 15, 2014 1:07 pm 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5048
Wow, thanks Kirk, that's a great graph. Amazing to see if you have 20% LEU you only need 1/10th extra enrichment capacity to make >90% HEU. For countries that are just starting to develop enrichment technology for a bombs program, that makes 20% LEU an attractive feed material if they can get it somehow.

DU is no great threat at all, because it has similar Pu production capability as NU. Which is dirt-common, literally...

In any case proliferation is a silly argument, like saying steel mills are a proliferation threat because steel can be used to make machine guns, bullets, bombs and missiles (which is, in fact, being done almost everywhere around the world, unlike nuclear proliferation).


Top
 Profile  
 
PostPosted: May 15, 2014 4:05 pm 
Offline

Joined: Dec 24, 2011 12:43 pm
Posts: 219
Location: Newport Beach, CA
Awesome Kirk, thanks. That was exactly what I was looking for. So the tl;dr version is that enrichment is not at all a linear process.

@ Cyril

I certainly haven't bought into the proliferation argument, it is indeed a dead end. I was just wondering if people who worry were worrying about the wrong material. Turns out not to be the case.


Top
 Profile  
 
PostPosted: May 15, 2014 5:49 pm 
Offline

Joined: Sep 15, 2011 7:58 pm
Posts: 186
Am I alone here? I do rightly fear the consequences of nuclear weapons for all, even if they're just in the 10 kiloton range. See the plot of "The Sum Of All Fears". Worse, I heard the idea of nuking one US city, and then threatening publicly to do it again in a week. I'm pretty sure the entire nation would shut down from panic as everyone starts to leave major cities. We want to avoid that.

Of course, I don't think the answer is to ban all things nuclear. However again, I do think that some proper appreciation for proliferation concerns is warranted. IMHO, if it's easier to build the nuclear weapon from scratch than to use a particular power plant, then there are no proliferation concerns about that plant. I imagine this is not true for most nuclear plant designs. For plant designs which make it significantly easier to get a nuclear weapon, I favor a strong non-voluntary international oversight from the IAEA. Is this a reasonable position? Do people here disagree?

PS: Is there a better thread for this?


Top
 Profile  
 
PostPosted: May 15, 2014 6:21 pm 
Offline

Joined: Aug 31, 2011 12:41 am
Posts: 28
As far as proliferation worries go, I believe HEU (not 239Pu) in the hands of non-state actors is the big risk. State actors (e.g. Iran) are going to be visible and subject to sanctions, political pressure, etc.

If I am an Al-Queda group, say, intent on having a fission bomb, building a gun-type device is the easiest path--implosion devices are more difficult. A non-state actor is not likely to be able accomplish enrichment, so theft is the likely strategy. Stealing a critical-mass of HEU from some research reactor somewhere is the big worry for me (and for the Obama administration, as they have been diligently securing HEU all over the world).

Although they run on HEU (233U), I don't see LFTRs as a big proliferation risk if they don't include means to isolate pure 233U. Convincing the public and regulatory authorities is another matter, however.


Top
 Profile  
 
PostPosted: May 16, 2014 2:14 am 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5048
Joshua Maurice wrote:
Am I alone here? I do rightly fear the consequences of nuclear weapons for all, even if they're just in the 10 kiloton range. See the plot of "The Sum Of All Fears".


I hate to break it to you, but if your fears of nuclear anything is based on Hollywood, you might want to reconsider the popular media and movie hyperbole attitude towards nuclear anything.

If you do believe in the movies you shouldn't worry, we have Ben Affleck and Morgan Freeman to save the day.

Quote:
Worse, I heard the idea of nuking one US city, and then threatening publicly to do it again in a week. I'm pretty sure the entire nation would shut down from panic as everyone starts to leave major cities. We want to avoid that.


Not very effective at all. Very high profile material/bomb type, difficult to get, not very destructive compared to say biological agents. You want something more under-the-counter. Dirty bombs are many orders of magnitude less deadly still. So, why would terrorists go the hard way that pays less dividend? They could go the easy way and quietly spread biological agent, killing many more.

Quote:
Of course, I don't think the answer is to ban all things nuclear. However again, I do think that some proper appreciation for proliferation concerns is warranted.


1. Most so called 'greens' disagree with this statement. They explicitly or implicitly use proliferation as an argument to not build nuclear powerplants. They prefer to have more greenhouse gas and pollutant proliferation, with a death toll of some 7 million/year currently and counting. (not including climate change which could, in the unlikely but worst case scenario, kill about 7 billion).
2. The two proliferation super highways are enrichment and small, low pressure, cool, Pu production reactors. If you want to make a difference, focus on blocking these two routes. This has absolutely nothing to do with commercial powerplants.

Quote:
IMHO, if it's easier to build the nuclear weapon from scratch than to use a particular power plant, then there are no proliferation concerns about that plant. I imagine this is not true for most nuclear plant designs. For plant designs which make it significantly easier to get a nuclear weapon, I favor a strong non-voluntary international oversight from the IAEA. Is this a reasonable position? Do people here disagree?


International oversight would be a good thing, it is already strongly implemented, but there are always some nations that don't cooperate... an inherent sovereignty issue, I'm afraid. It sort of only works for nations that aren't interested in making bombs or already have them.

Meanwhile, back in the real world... 7 million a year premature deaths due to pollution from so called renewable energy (wood and dung burning) and fossil fuels. Climate change risks are largely unknown (best case scenario: nothing much happens. Worst case scenario: Venus gets a twin sister and >7 billion people die).


Top
 Profile  
 
PostPosted: May 17, 2014 11:38 pm 
Offline

Joined: Apr 19, 2008 1:06 am
Posts: 2225
Proliferation is inevitable, like death. Let us follow the equivalent of normal health care. Keep nuclear power under peer review. Keep nuclear activities under IAEA review rather than let it control design and development.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 18 posts ]  Go to page 1, 2  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group