9/16/11 Update: New story from Wired — Thorium potential ‘overstated’ says government report
Following last week’s R-Squared Energy TV episode that discussed thorium nuclear reactors, there were a number of comments and emails from readers that added a lot of clarity to the discussion. I want to highlight some of those comments, because as I had indicated that was definitely outside of my area of expertise.
My general feeling is that there are some technical challenges that have been downplayed, and I compared the situation to that of hemp. Advocates of hemp for fuel frequently suggest that were it not for government regulations against it, hemp could be a major raw material for biofuels for the U.S. My comment to that is always that hemp is legal to grow in many countries, and yet is not utilized in those countries for biofuels. Thus, there are challenges regarding hemp other than simply government regulations against it.
Nevertheless, many readers provided very good complementary information on the topic of thorium reactors, and I share three of those comments and one email below.
The fuel fabrication for thorium reactors is not costly. Thorium oxide mined from the earth can be put straight into a liquid fluoride thorium reactor (LFTR). Thorium is about 4 times more abundant that uranium 238. Thorium is about as abundant as lead.
A LFTR works by converting the fertile thorium into fissionable (burnable) uranium. Both the thorium and uranium are mixed with molten salts that allows the reactor to pump the ‘fuel’ around for processing and heat transfer.
A LFTR has many advantages over a light water reactor; however, there are two main features that contribute to its safety: 1) since the ‘fuel’ is liquid, the reactor is ‘self-regulating’. As the reactor heats up the molten salt expands and moves the uranium away from the core; thereby slowing the reaction. 2) liquid fuel allows a ‘safety plug’ (made of the same ‘fuel’ salt with a fan blowing across it to keep it solid) to be installed on the reactor. In the event that the pump circulating the fuel stops or the reactor needs to be shutdown, the fan stops blowing, the molten salt melts the ‘plug’ and drains into a tank designed for maximum heat transfer. This ‘drain plug’ is walk away safe since it depends upon gravity to work.
This is a great advantage over light water reactors. They all require some kind of active cooling and hence some kind of generator to run the cooling. This is what failed at Fukushima. The tsunami wiped out all of the back up generators that would have cooled the solid fuel uranium. A LFTR in the same scenario as Fukushima would have had no problems. The molten salt fuel would have drained into their tanks and solidified back to crystal salt in the tanks. Once the danger was over, the Japanese could have heated the drain tanks and pumped the molten salt back into the reactor to restart it. This technology was demonstrated at Oak Ridge National Labs in 1965 – 1969. At Oak Ridge the technicians would shut off the reactor over the weekends this way and restart it on Monday.
I recommend that you read Dr. Richard Hargraves book called “THORIUM: energy cheaper than coal.” The book was published just last month. He runs through all of the competing energy production technologies, prices them, and discusses how thorium can be cheaper than all of them. The book’s website is http://www.thoriumenergycheaperthancoal.com/. It is available on Amazon.
AFAICT, there are numerous challenges in building high temperature molten salt reactors, and this is why we are unlikely to see them commercialised – at least not in a large scale – anytime soon. But I’m fairly sure that if the engineering hurdles can be overcome, LFTR-style designs hold an enormous promise, mainly because of the strongly negative thermal coefficient of reactivity, which means they can be easily throttled to match demand. They might work extremely well as a complement to solar and wind; they could be cranked up nighttime and during calm weather and idled whenever solar and wind are plentiful.
Actually, a liquid fuel reactor could be run on uranium as well. It’s more about the reactor design than about the fuel. I think the main reason they did not get commercialised in the past was that the whole concept was so different from all previous reactor designs that none of the conventional nuclear reactor expertise was any good for them and that to be viable they would have needed to make a couple of material science breakthroughs to prevent corrosion of the reactor chamber structures at the sustained high temperatures. I am all for continued research and development in nuclear power and LFTR is one of the most exciting ideas that are floating around, and certainly one of the most radical ideas that might actually become reality. But it’s still in its early stages, and huge showstopper issues might still come up.
After reading a bunch of pro Thorium articles a year or so back, I also wondered why it hasn’t been commercially successful if it’s truly as superior as proponents claim (and has been fairly well understood for nearly 50 years). So I did a very quick google and easily found a slew of articles that seem to directly contradict many of the claims made by the pro-Thorium crowd. Here is one example from a very well respected organization
I’d like to hear a true Thorium expert respond to the claims in this document.
The other thing is that a significant percentage of the pro-Thorium articles seemed to include a very faint but detectable whiff of conspiracy to them. Many of them included verbage that implied ‘If only big-oil/big-uranium/government/the UN/etc would stop suppressing Thorium we’d all have clean nuclear energy that is nearly too cheap to meter’. That type of stuff always sets my baloney detector into high gear.
I really do have an open mind about it. I appreciate there absolutely is great potential there. I just would like to hear the response to critics, and of course, I’d really like to see the results from a functional, near-industrial sized reactor before I hop fully on board. I mean hasn’t India been pursuing commercial Thorium power for years with very limited success?
Three quick thoughts about thorium development:
1. Your comparison to hemp advocates stung a little (I’m a thorium advocate), but I have to admit, it was apropos. Still, there is a huge difference in regulation between biomass and nuclear of any sort in this country.
2. Thorium fuel processing into thorium oxide is indeed expensive, but that is only for solid-fueled reactors. Most thorium advocates (at least as I have observed them) are pushing for liquid-fueled thorium reactors, a type of molten salt reactor. These don’t need thorium oxide, just plain old thorium. Of course they do need a neutron source to get them going, which is something of a challenge.
3. There are good reasons to believe that uranium will get very expensive in the next few years. The world hasn’t produced as much uranium as we consume in probably 40 years because we are still drawing down inventories of it from the 40s and 50s. Those will probably deplete before too long, and the price of uranium will jump accordingly. Of course the fuel inputs are such a small part of the cost of nuclear power that this would not be analogous to oil or coal jumping substantially in price.