Good question Robert! It's about the accidents of history and politics, not physics. Nuclear engineer Kirk Sorenson explains in his half hour Google Tech Talk, "Why the MSR didn't happen?" If you want the whole story, please watch this 30 minute introduction to the history of MSR's.
http://energyfromthorium.com/2011/12/23/techtalk-why-tmsr/

The short version is that:-
1. The military already knew about uranium & plutonium from the Manhattan Project and "The Bomb".
2. Nixon wanted to push jobs in a certain electorate, and so went with a fast breeder program instead of the 'slow' thermal reactor like the Molten Salt Reactor burning thorium.
3. An arrogant Senator basically thought Weinberg's insistence on more safety than the Light Water Reactor (that Weinberg invented!) meant Weinberg shouldn't be in the nuclear game, and fired him. This effectively ended the MSR program.
https://en.wikipedia.org/wiki/Alvin_M._Weinberg#Leadership

The only good to come out of it is that the Liquid Metal Fast-Breeder program eventually created the EBR2. Fast-breeders are a GOOD reactor, and can be configured to prevent 'bomb grade' plutonium, and burn nuclear waste and warheads instead. The EBR2 ran well for decades, and like the MSR / LFTR has inherent safety, is room pressure, and can burn nuclear waste. But I don't like it using sodium, which is unstable. However, I'd much rather the world use a whole fleet of LMFB's burning nuclear waste than coal, as it would save 3 million lives a year! Coal kills 4000 times more people than nuclear.
GE have developed plans for the PRISM reactor based directly on the EBR2.
https://en.wikipedia.org/wiki/PRISM_(reactor)

The only problem? Politicians again! They shut down the EBR2 program fearing proliferation, and didn't understand there are different isotopes and purities of plutonium, and not every reactor can make a bomb! GE are now just looking for a country willing to let them build the PRISM, then they could start converting all that lovely nuclear waste into clean energy for the whole planet for 500 years! Today we should build out AP1000's as fast as we can. They produce the perfect 'waste' for future PRISMS and MSR's to eat.

Nuclear 'waste' is actually not a problem to store for 100,000 years, but a fuel to burn in IFR's and LFTR's and could power the world for 500 years! Because the nuclear 'waste' in the USA could power America alone for 1,500 years, nuclear 'waste' is actually worth $30 TRILLION!

(Once all the actinides are burned out, the final 'fission products' are the true waste, and only have to be stored for 300 years).
$30 TRILLION dollars from point 4 here!
http://bravenewclimate.com/2009/10/16/ifr-spm/

I have had a look at the figures for renewable energy generated in Europe and compared it to Australia.
Europe in 2013 generated GWh of power by:-

Hydro 361000
Wind 352067
Solar 89482

Total 793303

Australia generated in total from all sources:-
213500 GWh

Therefore Europe which is smaller in area than Australia produced 3.7 times more renewable energy than Australia did from all sources.
So why would we even bother with underdeveloped thorium nuclear power with all its technical and political problems?

Wind and hydro are almost certainly cheaper than nuclear, and solar will probably be as well fairly soon.

Yes, there are some big figures there, but the BIGGEST is the amount of money wasted on relatively tiny energy returns! It's ideology, not rational energy policy, driving any attempt to get to 100% wind and solar. Some countries with large hydro can go 100% renewable with a good mix of hydro wind and solar. But they're few and far between. The MOST abundant renewables are also the MOST intermittent and unreliable: wind and solar. Let's check them out!

First, in Germany solar is 3 times more expensive than nuclear: and it doesn't run on a cold German winter night.
"An analysis by the Breakthrough Institute finds that the entire German solar sector produces less than half the power that Fukushima Daiichi – a single nuclear complex – generated before it was hit by the tsunami. To build a Fukushima-sized solar industry in Germany would, it estimates, cost $155bn. To build a Fukushima-sized nuclear plant would cost $53.5bn. And the power would be there on winter evenings."
http://thebreakthrough.org/blog/2011/03/doing_the_math_comparing_germa.shtml

Secondly, to back up renewables seasonal fluctuations in northern countries like Germany could bankrupt any nation that tried it. You can *either* buy Tesla Powerpack batteries to back up *one week* of winter in Germany (at a hypothetical 30% penetration of wind and solar, and these wind and solar farms must still be bought), OR you can just buy safe modern nuclear-waste eating nukes that will do the whole job for 60 years. Again, *backup* a third of a renewable grid for just one week, or nuke the whole grid for 60 years! That’s the economics of renewable storage V nuclear.
Point 2 below
http://thebreakthrough.org/index.php/issues/renewables/the-grid-will-not-be-disrupted

Third, in some places like Germany, Solar PV + STORAGE may not even be much of an energy source!
Nuclear, on the other hand, can have an ERoEI* of about 75 to 100 or more.
(* ERoEI = Energy Return on Energy Invested: or how much energy you actually get after all the energy to build it).
http://bravenewclimate.com/2014/08/22/catch-22-of-energy-storage/

This is why Dr James Hansen supports a waste-eating GenIV reactor called the Integral Fast Reactor.
http://www.thesciencecouncil.com/

Warmair: I have had a look at the figures for renewable energy generated in Europe and compared it with Australia.

So, what were the respective Europe and Australia GWh totals for energy generated from all sources combined?

Max
Fukushima Daiichi is as good as proof anyone could ask for that nuclear is a bad idea. First of all it cost billions to build and now it is going to cost anything up to $100 billion or more to clean up the mess. At this stage some $150 billion dollars has been or will be spent and the power station will never produce power again. An area of around the plant of some 20ks will remain unusable for 100 years or so, and the fishing grounds off the coast are now contaminated. The plant was notorious for fudging the maintenance work and should never have been built where it was. The result of the tsunamis was that all of the nuclear plants in the Japan were closed down and in it is only in recent times that some of the other nuclear plants have been allowed to restart. The result for the Japanese has been severe power shortages and rationing.

How people can promote nuclear and then claim wind and solar are no good because they are intermittent boggles the mind. I also like the way they fail to mention that hydro, tidal, biomass, wave power, and power storage, can make up for most the occasions when insufficient power is available from wind and solar.

Raycom
Total electrical power generated from all sources in 2013 was:-
Europe about 3.10 Million GWh
Australia about 213500 GWh

Of the European totals renewables contributed hydro (12.8 %), wind turbines (7.5 %) and solar power (2.7 %).

Non renewables
Nuclear power plants (26.8 %) and falling
Fossil fuels (49.8 %)

Based on information from here:-
http://ec.europa.eu/eurostat/statistics-explained/index.php/Electricity_production,_consumption_and_market_overview