Ansewers to Douglas Wise's Questions about MSR/LFTR Technology

In what started out as a discussion of a BNC post on fast reactors, many questions about MSR/LFTR technology were raised. Since i was participating in the discussion, i attempted to answer many of the questions. here are some questions, by Douglas Wise and my responses.

Douglas Wise asked me to

clear a few misunderstandings I may have that relate to IFRs and LFTRs.

on BNC a couple of Days ago. Douglass observed:

I understand that the term LFTR relates to a bewildering array of different designs, having in common molten salt cooling and fuelling and the use of thorium – either mixed or separated from uranium and with continuous reprocessing onsite. If I am correct, do you not think that the multiplicity of designs reduces or enhances the chance of any single one ever getting built?

i responded,

you are correct that there is a whole class of Molten Salt Reactors, which can include both chloride and fluoride salt cooled reactors, single fluid and two fluid reactors. Fluoride reactors can be moderated by graphite, heavy water, by fluoride salts themselves, or even be relatively unmoderated fast neutron reactors. Chloride reactors are fast reactors.
There has been limited research on Chloride Salt fast reactors, despite some notable advantages over metallic sodium. They share on major disadvantage with IFR, the size of the load of fissionable materials required to maintain criticality.

The Two Fluid Le Blanc tube core is the simplest reactor core that will ever be designed.

Douglass also asked,

I also understand that most of the the initial research was conducted at Oak Ridge in the States and was subsequently carried on in Japan with joint funding from the States, Russia and Japan. This project appears to have run out of funding. Given the promise of the technology, as eloquently set out by its supporters, how do you explain that this funding has been allowed to lapse?

I responded,

During the Nixon administration a report was prepared by the AEC to justify the decision to kill the MSBR. Reasons included the argument that the the LWR and the LMFBR were mature technologies, while the MSBR was not. Three Mile Island was to prove the report wrong on the LWR, and the LMFBR was from from mature. in fact far more money was spent on the failed Clinch River Breeder Reactor that would have been required to develop MSBR. The report also argued rather absurdly that the MSBR should not be developed because it needed to be developed. The US Department of Energy has never taken another independent look at Molten Salt Reactor technology, and, as of last year, continues to reference the very flawed WASH-1222 for its MSR evaluation.

The MSR was considered dead until 4 years ago when Kirk Sorensen, David Le Blanc, David Walters, myself, and a few other people who understood the potential of MSRs and thorium started to work to educate people about it. I knew about the MSR because my father was a pioneer development, and did research on it at ORNL for 20 years.

Douglas Wise asked.

You move on in your final paragraph to suggest that “the EFT crowd is likely to produce a two fluid thermal fluoride salts thorium breeder, which does limit choices.” Does this indicate that you have misgivings about their likely final design concept?

My response was,

No, i favor a 2 fluid design.

Douglas asked,

I am also puzzled about your use of the term, “produce”. Does this imply that “the EFT crowd” is in possession of adequate funding to research and develop its preferred design?

My response,

This means that one or more funding sources may be in the offing.

Douglas stated,

If you really believe that an LFTR design can be taken to demonstrator level within a decade given sufficient funding, it may be more sensible for some nations to go directly for this technology and bypass Generation 3.

I responded,

There is a real potential for a uranium fueled, transition MSR, that might well compete with Generation III technology before 2020, with a LFTR emerging after 2020. This depends on investment interest. There may be possible military involvement in a near term MSR project.

Douglas wrote,

I have read that thermal LFTRs may breed less quickly than fast reactors, but this may not be important in the short to medium term, particularly as they require lower start charges.

I responded, High IFR breeding rates are not well documented, there are potential safety issues, enough current American weapons grade fissionable material stockpiles and RGP stockpiles are sufficient to start enough LFTRs to produce nearly 100% of American electricity with LFTRs + starting a number of IFRs.

Douglas asked,

what proportion of its potential economic advantage would be lost if one were to opt for water cooling and steam turbines as opposed to air cooling, gas turbines and a Brayton cycle (using either helium or CO2)?

I responded,

Efficiency with steam turbines up to .40, efficiency with toping and bottoming cycles + Brayton cycle >.50.

Douglas asked,

You talk of a uranium fueled transition MSR as a distinct entity, separate from the LFTR. Is this the chloride fast reactor that you referred to earlier or something else again?

I responded,

Something else, a uranium fuel cycle thermal converter that uses fluoride salt coolant/fuel carriers. The advantage would be that all of the technology for such a reactor was tested during the Molten Salt Reactor Experiment. The cost of a uranium fuel cycle reactor would be low, it would have all of the cost advantages of the LFTR, but without the added expense and complexity of breeding. While not offering sustainable technology, it would be very cost competitive with Light Water Reactors, as well as offering outstanding flexibility, rapid deployment, and outstanding safety.

Doug;as asked,

Am I to understand that plutonium wouldn’t be suitable as a start charge and that this transition reactor wouldn’t produce U233 from thorium?

I responded,

RGP could be used as a start charge, as could U-235 or a combination. The uranium cycle reactor would not be designed to produce U-233 via a thorium fuel cycle.

Douglas stated,

I am also wondering why this transition technology would be more likely to satisfy regulators more quickly than would an LFTR.

i responded, Fewer issues for regulators to consider. And proliferation issues not as complex.

Douglas enquired,

Perhaps ,on reflection, the transition reactor to which you refer is that that has recently been discussed here (molten salt cooled pebble bed as being researched by Prof Peterson?)

I responded,

We are talking about a standard MSR design that would be very similar to the Molten Salt Reactor Experiment, but larger.

Finally Douglas stated,

I am particularly interested in the use of plutonium as a start charge. We have a 100 tonne stockpile of the stuff which has the potential, I would have thought, to be very valuable, despite the fact that several of our nuclear “experts” would like to render it permanently unusable.

I commented,

That 100 tons of RGP could start somewhere between 100 GWs and 200 GWs of MSRs/LFTRs. Not using it to produce energy would be a tragedy.