Thorium Disadvantages
Channel: Thorium Remix
Date: 2017-08-06

Uranium-233 is a fissile isotope of uranium that is bred from thorium-232 as part of the thorium fuel cycle. Uranium-233 was investigated for use in nuclear weapons. Uranium-233 is produced by the neutron irradiation of thorium-232. Thorium-232 absorbs a neutron, becomes thorium-233, then quickly decays into protactinium-233. Protactinium-233 has a half-life of 27 days and before decaying into uranium-233.

This protactinium has a large cross-section and can absorb neutrons needed to sustain fission. Because uranium-233 releases so few neutrons in thermal-spectrum, and because 2 neutrons are needed to sustain a chain reaction, existence of protactinium would stop fission.

Protactinium-233 is a challenge unique to thorium reactors.

Low breeding ratio is a challenge unique to breeder reactors fueled by thorium, which operate in thermal-spectrum.

The 5,000 tpy figure of Thorium assumes a 50,000 tpy Rare Earths facility that primarily utilizes monazite as its feed-stock.

Thorium is a companion element to Monazite.  Monazite runs at +50% REE and about 7% Th.  So if you processed 50,000 tons of monazite you would get about 3,500 tpy of Th.  However, monazite would not be the only feed-stock. You would use many other mineralizations. like apatite running at 3% REE and .002% Th (but with lots of heavy REE).  So it would be a mix and tend toward the 5,000 tpy range.

Thorium Disadvantages listed in this video:
00:00 Solid-fuel thorium reactors fuel utilization ratios similar to PWR.
00:42 Liquid-Fuel in United States licensing is "scary".
02:04 Obama Administration willing to give away MSR know-how.
02:40 PWR seen as "good enough" for long time.
03:00 Licensing restrictions specifically target liquid-fuel.
04:45 NEA OECD evaluated solid-fuel, and liquid-fuel-fast-spectrum only.
20:50 Thermal-spectrum neutrons hitting U233 produce only ~2.3 neutrons.
23:00 Graphite moderator required to sustain fission in MSBR thermal-spectrum.
27:50 Protactinium-233 half-life 27 days.
29:00 Material challenges (MSR is pre-requisite so MSR challenges are Th challenges.)