Something I thought should happen, hoped to happen, actually happened in 2024, some good news.

[NNadir]

Last edited Sun Jan 19, 2025, 10:24 PM - Edit history (1)

There is only one type of existing commercial thermal nuclear reactors that can function as a breeder reactor; this is the Canadian CANDU, type reactor, which uses deuterated water (with an extremely low thermal neutron capture cross section) as a coolant. Forty-Six examples of this type of reactor exist in several countries: In Canada, in India (the second largest share after Canada), as well as in Argentina, China and Romania.

However the only nuclide that cause a CANDU to breed is the uranium isotope ²³³U isotope, which does not occur naturally in isolatable quantities on Earth: It is part of the long extinct ²⁴⁹Cf (²³⁷Np) decay chain. ²³³U however can be made synthetically by the ²³²Th[n, gamma]²³³Th reaction (²³³Th t_1/2 = 22.3 minutes) resulting in two beta decays through ²³³Pa (t_1/2 = 26.975 days) to ²³³U. (A molten salt reactor famously did this in the 1960's, but it was an experimental reactor, although while it operated, for about two years, it produced the world's largest inventory of ²³³U which is, to my knowledge, still available at ORNL.)

I have long thought that because of their very high neutron efficiency, CANDU reactors, which run on unenriched uranium, should use fuel containing some thorium, to increase their "burn-up" (the amount of energy produced per unit of mass) to very high levels. In addition, through a fuel cycle, considerable amounts of fissionable plutonium would be generated, along with fissionable ²³³U. This would make the residual fuel very valuable as after the fuel reaches a subcritical regime because of the accumulation of fission products with high neutron capture cross sections, reprocessing to remove these would leave enriched uranium (with ²³³U) that would be ready for use in other thermal reactors around the world, without the use of physical enrichment processes. This would have the effect of making the fuel useless for nuclear weapons, while increasing the rate at which we can provide new reactors with fuel without mining.

Apparently a commercial organization thought the same thing and in fact, manufactured a fuel to do precisely this which is now being tested.

To wit:

Licensing and testing progress for innovative thorium-based fuel

Days after announcing the start of accelerated irradiation testing and qualification of its patented ANEEL thorium and high-assay low-enriched uranium fuel at Idaho National Laboratory, Clean Core Thorium Energy announced it has completed the first phase of the Canadian nuclear regulator's pre-licensing review process.

ANEEL has been developed for use in pressurised heavy water reactors and Candu reactors (its name is taken from Advanced Nuclear Energy for Enriched Life). The company says it can offer significantly improved performance with existing proven heavy water reactor systems by leveraging thorium's "inherently superior" nuclear, thermal and physical properties while retaining the same external dimensions and configuration design as in currently used natural uranium fuel bundles. It can be used to replace current fuel bundles, without any significant modifications to the reactor, to reduce life-cycle operating costs and waste volumes, increase safety and accident tolerance, and result in additional proliferation resistance, the company claims.

ANEEL is the first thorium-based fuel for Candu reactors to successfully complete the first phase of the Canadian Nuclear Safety Commission (CNSC) pre-licensing process for new fuel designs, Clean Core said...

A CANDU reactor using natural uranium has a burn up of considerably less than 10 GWd/ton. (GWd = Gigawatt-days, a unit of energy that is equal to 86.4 trillion Joules.). This results in large volumes of fuel that is relatively dilute in valuable fission products and actinides like plutonium and thus more challenging to reprocess.

The ANEEL fuel can achieve burnups far higher, more than 600% higher:

...The CCTE-ANEEL-1A irradiation experiment is to begin this month and achieve burnup targets of up to 60 GWd per tonne. As each planned burn-up target is achieved, the test capsules containing irradiated ANEEL pellets will be sent to INL's Materials and Fuels Complex for destructive and non-destructive post-irradiation examination.

"Irradiating homogeneously blended thorium and uranium oxide in ATR is a first-of-a kind experiment for INL and the US DOE,", said Michael Worrall, a nuclear engineer at INL and Principal Investigator for the CCTE-ANEEL-1A experiment. "We are excited to see the potential of the ANEEL fuel technology and what the future of this technology holds."

The ATR is a pressurised water test reactor which operates at very low pressures and temperatures compared to a large commercial nuclear power plant to produce large-volume, high-flux thermal neutron irradiation in a prototype environment. The one-of-a-kind reactor can be used to study the effects of intense neutron and gamma radiation on reactor materials and fuels...

Assuming that the United States does not fall into anarchy under incompetent and ignorant leadership, this offers hope for the future and the rapid scale up of nuclear energy.

Have a nice evening.