New Age Nuclear (Thorium is safer & cleaner)

Cosmos Magazine ^

[BlackJack]

Nuclear energy produces no greenhouse gases, but it has many drawbacks. Now a radical new technology based on thorium promises what uranium never delivered: abundant, safe and clean energy - and a way to burn up old radioactive waste.

What if we could build a nuclear reactor that offered no possibility of a meltdown, generated its power inexpensively, created no weapons-grade by-products, and burnt up existing high-level waste as well as old nuclear weapon stockpiles?

And what if the waste produced by such a reactor was radioactive for a mere few hundred years rather than tens of thousands? It may sound too good to be true, but such a reactor is indeed possible, and a number of teams around the world are now working to make it a reality. What makes this incredible reactor so different is its fuel source: thorium.

[Wonder Warthog]

"Thorium is a safer and cleaner nuclear power source. I wish the media would show some interest in this type of nuclear technology."

Ye gods. The article is mostly bull****. Fission is fission, whether it is U-233 bred from Th-232, U-235 split directly, or Pu-239 bred from U-238. The mix of fission products is virtually the same in all cases. The ONLY significant advantage thorium has is that there is a lot more of it available.

[CarrotAndStick]

Thorium

The use of thorium-based fuel cycles has been studied for about 30 years, but on a much smaller scale than uranium or uranium/plutonium cycles. Basic research and development has been conducted in Germany, India, Japan, Russia, the UK and the USA. Test reactor irradiation of thorium fuel to high burnups has also been conducted and several test reactors have either been partially or completely loaded with thorium-based fuel.

Noteworthy experiments involving thorium fuel include the following, the first three being high-temperature gas-cooled reactors:

Between 1967 and 1988, the AVR experimental pebble bed reactor at Julich, Germany, operated for over 750 weeks at 15 MWe, about 95% of the time with thorium-based fuel. The fuel used consisted of about 100 000 billiard ball-sized fuel elements. Overall a total of 1360 kg of thorium was used, mixed with high-enriched uranium (HEU). Maximum burnups of 150,000 MWd/t were achieved.

Thorium fuel elements with a 10:1 Th/U (HEU) ratio were irradiated in the 20 MWth Dragon reactor at Winfrith, UK, for 741 full power days. Dragon was run as an OECD/Euratom cooperation project, involving Austria, Denmark, Sweden, Norway and Switzerland in addition to the UK, from 1964 to 1973. The Th/U fuel was used to ‘breed and feed’, so that the U-233 formed replaced the U-235 at about the same rate, and fuel could be left in the reactor for about six years.
General Atomics’ Peach Bottom high-temperature, graphite-moderated, helium-cooled reactor (HTGR) in the USA operated between 1967 and 1974 at 110 MWth, using high-enriched uranium with thorium.

In India, the Kamini 30 kWth experimental neutron-source research reactor using U-233, recovered from ThO2 fuel irradiated in another reactor, started up in 1996 near Kalpakkam. The reactor was built adjacent to the 40 MWt Fast Breeder Test Reactor, in which the ThO2 is irradiated.
In the Netherlands, an aqueous homogenous suspension reactor has operated at 1MWth for three years. The HEU/Th fuel is circulated in solution and reprocessing occurs continuously to remove fission products, resulting in a high conversion rate to U-233.
There have been several experiments with fast neutron reactors.

Power reactors

Much experience has been gained in thorium-based fuel in power reactors around the world, some using high-enriched uranium (HEU) as the main fuel:

The 300 MWe THTR reactor in Germany was developed from the AVR and operated between 1983 and 1989 with 674,000 pebbles, over half containing Th/HEU fuel (the rest graphite moderator and some neutron absorbers). These were continuously recycled on load and on average the fuel passed six times through the core. Fuel fabrication was on an industrial scale.

The Fort St Vrain reactor was the only commercial thorium-fuelled nuclear plant in the USA, also developed from the AVR in Germany, and operated 1976 - 1989. It was a high-temperature (700°C), graphite-moderated, helium-cooled reactor with a Th/HEU fuel designed to operate at 842 MWth (330 MWe). The fuel was in microspheres of thorium carbide and Th/U-235 carbide coated with silicon oxide and pyrolytic carbon to retain fission products. It was arranged in hexagonal columns (’prisms’) rather than as pebbles. Almost 25 tonnes of thorium was used in fuel for the reactor, and this achieved 170,000 MWd/t burn-up.
Thorium-based fuel for Pressurised Water Reactors (PWRs) was investigated at the Shippingport reactor in the USA using both U-235 and plutonium as the initial fissile material. It was concluded that thorium would not significantly affect operating strategies or core margins. The light water breeder reactor (LWBR) concept was also successfully tested here from 1977 to 1982 with thorium and U-233 fuel clad with Zircaloy using the ‘seed/blanket’ concept.

The 60 MWe Lingen Boiling Water Reactor (BWR) in Germany utilised Th/Pu-based fuel test elements.

India

In India, both Kakrapar-1 and -2 units are loaded with 500 kg of thorium fuel in order to improve their operation when newly-started. Kakrapar-1 was the first reactor in the world to use thorium, rather than depleted uranium, to achieve power flattening across the reactor core. In 1995, Kakrapar-1 achieved about 300 days of full power operation and Kakrapar-2 about 100 days utilising thorium fuel. The use of thorium-based fuel was planned in Kaiga-1 and -2 and Rajasthan-3 and -4 (Rawatbhata) reactors.

With about six times more thorium than uranium, India has made utilisation of thorium for large-scale energy production a major goal in its nuclear power program, utilising a three-stage concept:

Pressurised Heavy Water Reactors (PHWRs, elsewhere known as CANDUs) fuelled by natural uranium, plus light water reactors, produce plutonium.
Fast Breeder Reactors (FBRs) use this plutonium-based fuel to breed U-233 from thorium. The blanket around the core will have uranium as well as thorium, so that further plutonium (ideally high-fissile Pu) is produced as well as the U-233. Then
Advanced Heavy Water Reactors burn the U-233 and this plutonium with thorium, getting about 75% of their power from the thorium.
The spent fuel will then be reprocessed to recover fissile materials for recycling.

This Indian program has moved from aiming to be sustained simply with thorium to one “driven” with the addition of further fissile uranium and plutonium, to give greater efficiency.

Another option for the third stage, while continuing with the PHWR and FBR programs, is the subcritical Accelerator-Driven Systems (ADS).

http://www.world-nuclear.org/info/inf62.html

[HEY4QDEMS]

And what if the waste produced by such a reactor was radioactive for a mere few hundred years rather than tens of thousands?

That may be true but when Thorium is RA it produces radon gas.

[RinaseaofDs]

One place: Nuclear Waste. It’s a byproduct of current power reactors.

[rednesss]

Even so, there is enough U-238 mill tailings sitting around that don’t need to be mined at further expense that could be used to fuel a fast breeder liquid metal reactor. Reprocess all of the spent fuel rods, glean the Pu and U in those instead of burying them. Lots of energy not being produced.

[HDCochran]

This article is largely puffery. The thorium-232 -> uranium-233 fuel cycle produces only marginally less dangerous fission products than the uranium-238 -> plutonium-239 fuel cycle, and uranium-233 is very dangerous and difficult to work with. Nor is the thorium-232 -> uranium-233 fuel cycle new. There have been several developmental nuclear reactors pointed toward this as a commercial goal over the past forty years or so. Gas-cooled, solid fueled reactors have been developed by the US and Germany, among others toward tis goal. And a molten salt cooled and fueled reactor was operated in the US at Oak Ridge National Laboratory in the late 60s and early 70s. This reactor successfully bred uranium-233 from the thorium-232 in the fuel salt. The fuel salt was processed successfully to separate uranium and fission products, and the remaining fuel salt was quite low in radioactivity. Then, this reactor was successfully fueled and operated with uranium-233. This molten-salt cooled and fueled reactor was ‘intrinsically safe’ in that, if the reactor started to ‘run away’ and overheat, the molten salt fuel expands and reduces the reaction rate and thus lowers the temperature without requiring any action by operators or control systems.

Despite all of this, the concept did not appear to be as commercially attractive or close to commercial deployment as the liquid metal cooled fast breeder reactor concept. The molten salt reactor concept was dropped and several countries developed and operated liquid metal breeder reactors. This concept has been pursued by other countries but also dropped by the US. The main reason it hasn’t been a commercial success is that there has been a global glut of enriched uranium as a result of disarmament and it doesn’t make commercial sense, in these conditions, to build breeder reactors of any kind.

[chimera]

I see nothing in the physics that would indicate a significantly different fission product spectrum from 233U versus 235U. You’re still going to have to manage the material after it’s used. That’s not an unmanageable problem, but it will still have to be dealt with.

[BlackJack]

Great post carrot....thanks!

[BlackJack]

I am also interested in the PBMR design....I see atomics is
using thorium...thanks again.

[aruanan]

And what if the waste produced by such a reactor was radioactive for a mere few hundred years rather than tens of thousands?

A pound of radioactive waste that is radioactive for a few hundred years rather than tens of thousands of years is WAY more dangerous.

[chimera]

All this is true. It’s just that we had experience with enriched uranium and light water moderated systems. The economics favored the uranium fuel cycle, and still do, unless something changes. Western countries have a lot of experience and a lot invested in LWR technology using slightly enriched uranium fuel. That’s probably going to be the future in the near term. Alternate fuel cycles should be kept available as options in case something comes up that requires their use (such as faster-than-anticipated depletion of uranium reserves). But my guess is that reprocessing of “spent” fuel is a better bet, leading into a U-Pu kind of fuel mixture, maybe coupled with a closed fuel cycle concept like the IFR in Idaho.

[<1/1,000,000th%]

More detail here.

[BlackJack]

Why do you say that?
Can you explain?

[<1/1,000,000th%]

Because it gives off a lot more radiation.

[chimera]

Shorter half-life means a higher decay probability, and thus more activity for a given mass of material. Short-lived forms are “hotter”, from a radiological viewpoint.

[Wonder Warthog]

"I see nothing in the physics that would indicate a significantly different fission product spectrum from 233U versus 235U. You’re still going to have to manage the material after it’s used. That’s not an unmanageable problem, but it will still have to be dealt with."

Not only that, but I suspect it is quite feasible to build a fission bomb and/or fusion bomb trigger with U-233. Fission is fission, after all. So even the non-proliferation "advantage" is bogus.

[BlackJack]

Thanks will look into that.

[chimera]

I was just working today with activated aluminum, 28Al, with a 2.3 minute half-life. A 50 mg total mass (stable 27Al plus activated 28Al) sample, and you wouldn’t want to hold it in your hand, it was reading tens of R/hr on contact. An equal mass of natural uranium, however, you could hold in your hands for the rest of your life and it wouldn’t hurt you. Big difference between a 4.5 billion-year half-life and one of a few minutes.

[Malsua]

Thorium is a safer and cleaner nuclear power source

Come to Northern NJ, exit 63 on Route 80, go up 17 a bit and roll in the dirt on the eastern side of the highway. When you're done, you'll be just positively glowing, thanks to Thorium!

[Centurion2000]

Thorium is a safer and cleaner nuclear power source.

Not really ... fission byproducts are all radioactive.