# We *already built* the light water breeder?

1. Jan 8, 2015

### nikkkom

In another thread http://en.wikipedia.org/wiki/Shippingport_Atomic_Power_Station was mentioned. I went to the link, thinking "okay, I remember this one, the first commercial reactor exclusively for electricity generation, not weapon needs. Mostly only historical interesting..."

I was reading the article at leisure when it struck me. It was a U-233/thorium reactor. It was a light water reactor. It was a breeder. It succeeded in demonstrating that breeding was achieved.

WAIT A SECOND. The light water thorium breeder. The holy grail of unlocking full energy reserves of thorium and possibly all uranium too (as opposed to only using U-235, a much more scarce resource). We already had it, and it *worked*. In *1982*.

Why our today's reactors aren't light water thorium breeders, then?

Why Indians are torturing themselves trying to build a heavy water breeder, which is more expensive and has some additional problems such as tritium generation?

Why did US and other nations spent lots of effort trying to develop fast breeders, which have significant problems too?

Last edited: Jan 8, 2015
2. Jan 8, 2015

### Doug Huffman

It is a long hard step from a one off demonstration to economically practical, as my friend Rod Adams explains.

3. Jan 8, 2015

### nikkkom

But... "the reactor reached criticality on December 2, 1957" (wiki). It was one of the very first power reactors. The "hard step" from experiment to commercially viable power stations wasn't yet made for _any_ reactor type.

From what I read here http://www.inl.gov/technicalpublications/Documents/2664750.pdf [Broken]
the reactor's core and fuel weren't radically different from what is in use today. Ceramic oxide pellets as fuel. Zirconium cladding.

I just don't see an obvious reason why this particular type of reactor (thorium LWR breeder) wasn't developed further, but uranium NON-breeders were. The basics of their designs are reasonably similar. I know this place has people very knowledgeable of US nuclear power history, I hope someone knows the reason "why".

Last edited by a moderator: May 7, 2017
4. Jan 8, 2015

5. Jan 9, 2015

### Doug Huffman

Shippingport is where my seniors got their experience before the resources that I enjoyed existed.

About why, explanations are ignored, denied and disputed. "Similar" is a Sorites heap paradox; 2000 exceptional hand measurements per module is hardly similar. I suspect that our disputant knows as little of fuel physics as do I, but I had a physicist at my elbow while I tested his product.

6. Jan 9, 2015

### nikkkom

Ah... that probably explains it: by the time successful thorium breeding was confirmed, uranium LWR designs were already built and running commercially.

7. Jan 9, 2015

### Hologram0110

The key for commercial power plants is the cost of producing power while maintaining license requirements. What makes you think thorium is any better at this goal? UO2 works, has a long (relatively) well understood behavior (easier to license), its fuel cost are relatively cheap with well established global supply chains and there is no risk of running out of it in the short term. If you enrich it sufficiently you can get relatively high burnup and run long batch cycles with no need to reprocess.

Thorium has some interesting benefits (better material properties), large global reserves and the possibility of thermal breeding. However, these don't necessarily translate into cheaper power or higher profits. Some how people have gotten the impression that thorium is some sort of superfuel, but I don't see where the major gains as supposed to come from.

8. Jan 9, 2015

### Doug Huffman

Thorium is done no favors being conflated with liquid alkaline metal coolant/moderator/vehicle.

9. Jan 9, 2015

### nikkkom

Nothing makes me think that way. You jumped to a conclusion that I do.

I know that the motivation behind breeders is not lower cost, but more complete usage of our finite fissionable resources. I said: "The holy grail of unlocking full energy reserves of thorium and possibly all uranium too (as opposed to only using U-235, a much more scarce resource)."

10. Jan 9, 2015

### Hologram0110

Fair enough! That was my bad. I'm so used to people thinking thorium is magic that I interpreted your interest that way.

11. Jan 9, 2015

### mheslep

I'd like to comment, if I may.

Thorium has some advantages. In particular, a switch to thorium i) eliminates the long lived actinides leaving only fission products in the spent fuel stream, thereby reducing the storage time of harmful radiotoxicity from tens of thousands to a couple hundred years, ii) eliminates the enrichment fuel cycle aside from the need for breeding seeds; thus, regardless of the cost of the uranium enriched fuel cycle, thorium as a fuel must be less expensive, and iii) the high burnup afforded by thorium (170 GWd/t Th at Fort St Vrain) as compared to the typical LWR (35 or 40 GWd/t U) means fuel service intervals might be extended and the waste stream mass greatly reduced.

The suggestion for uranium fuel high burnup via higher enrichment ("enrich it sufficiently") runs counter to the goal of minimizing proliferation potential. Yes highly enriched uranium reduces the hazard of the waste stream, but has its own proliferation issues. If operating within existing regulations is a goal, 5% enrichment is the legal limit in the US. As long as U-238 is in the fuel stream of LWRs Pu will also appear in the waste stream.

The enriched fuel cycle is not entirely "global". Visibly there are several countries that buy and sell enriched fuel to each other, but that list is highly restricted. The like of Yemen, Nigeria, Burma, Iran are not allowed in, nor should they be IMO for security reasons. A future where the developing world starts adding nuclear plants instead of coal plants is made more likely without enriched fuel.

12. Jan 9, 2015

### mheslep

I list below the IAEA given "benefits" of thorium. "Challenges" are also given in the document.
http://www-pub.iaea.org/mtcd/publications/pdf/te_1450_web.pdf

13. Jan 9, 2015

### nikkkom

I assume this means "... by increasing burnup, and thus decreasing amount of waste".

Well, this is "almost untrue". Granted, the weight of generated spent fuel is less. But the amount of actual waste (fission products + actinides) will be about the same.

IOW: 1 ton of spent fuel at 100 GWd/t burnup has about the same amount of fission products as 2 tons of spent fuel at 50 GWd/t. After reprocessing and, say, vitrification you'll have about the same amount of glass to bury.

14. Jan 9, 2015

### mheslep

I don't mean fission products, which have relatively short half-lives, but the actinides which derive from U238. Reduce the ratio of U238 via enrichment, and one reduces actinides.
https://www.hzdr.de/db/PicOri?pOid=30404

15. Jan 9, 2015

### Hologram0110

I'm not disagreeing that thorium can do some cool things. I'm suggesting that doing cool things doesn't directly translate into cheaper power. Longer cycle times I'd wager is the most attractive aspect of thorium economically.

Are utilities incentivized to reduce waste? Does reducing production of actinides affect cost? Not really waste disposal is a very small component of the total cost. Greater chemical stability? Well maybe a little bit of a source term reduction, but it doesn't fundamentally change the game. Greater abundance of thorium doesn't decrease cost because there isn't the same supply chain and infrastructure in place (yet). Proliferation concerns don't really matter in countries that already have nuclear weapons or already posses other routes to nuclear weapons.

The benefits have to be balanced against the cost of licensing something different. And training everyone to work with 'different'. Investments in nuclear are already extremely expensive (capital) and high risk (financially speaking). Adding first of a kind (or generation) technology adds to those troubles.

16. Jan 9, 2015

### Hiddencamper

I was under the impression that LWRs cant get a high enough burnup to really take advantage of thorium. Thorium requires a higher neutron economy due to some parasitic effects and that combined with actinide buildup would limit available burnup from the fuel,

17. Jan 9, 2015

### mheslep

IAEA:
High burnup with Th (mixed with HEU) has been demonstrated (170 GWd/t)

18. Jan 9, 2015

### Hiddencamper

In a LWR?

I know it can in a HWR. Or a high temp has reactor. (Ft at vrain was where the 170gwd/ton came from, that's an htgr, not a LWR)

Last edited: Jan 9, 2015
19. Jan 9, 2015

### mheslep

Apparently you are considering only O&M money? Backup to new construction and staffing, and consider the spent waste pool construction for a given tonnage, long term waste storage for a given tonnage. Thus, the relevant question is, can the utility save money in new nuclear construction. Consider the cost of the construction of new enrichment plants at $4B each. A bit of a strawman: nothing is effective until it is built, and note that thorium has been used in commercial reactors three or four times so far. Yes. Proliferation though is a concern by definition about countries that do not have weapons. The A.Q. Khan episode was all about his delivery of enrichment technology to rogue states, and about which he had long experience and education. Take away the enrichment industry, and the likelihood of such events must decrease. Yes, which explains in part why no new nuclear projects have been completed in the US last 30 years. The five new reactors now under construction will just barely manage to maintain the collective output of the US nuclear fleet. The reality is that the public's unease, justified or not, about waste and proliferation and accidents drive costs (relative to say India,$1500/KW), made that way by regulation and legal battles. Thorium can help with the first two.

20. Jan 9, 2015

### mheslep

Sorry. For LWRs you may be correct.
Maybe only gas, heavy water, and molten salt can obtain high burnup.