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PostPosted: Jan 11, 2017 5:24 am 
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Next Big Future trawled up yet another fusion/fission hybrid, this time with an MSR. With added function of a final air brayton turbine rather than a steam cycle.

http://www.nextbigfuture.com/2017/01/hybrid-fusion-fission-molten-salt.html

An FFH called HMSR, uses what appears to be a single fluid MSR with a shared molten salt blanketed fusor.

There's a dissertation here

http://trace.tennessee.edu/cgi/viewcontent.cgi?article=3111&context=utk_graddiss

and mostly similar material here

http://bp.pppl.gov/pub_report/2016/PPPL-5192%20REPORT.pdf

Seems to use the fusor as a neutron source, perhaps similar in function to an ADSR?


Regardless, this sounds like hunting for a use for an existing Tokamak design (Princeton Plasma Physics Lab being the giveaway here), so an MSR was deemed a possible bedfellow...


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PostPosted: Jan 11, 2017 1:44 pm 
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Sounds to me like it's just a dissertation. A concept with the sole purpose of finishing school.


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PostPosted: Apr 03, 2017 6:50 pm 
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Former Google Vice President Starts a Company Promising Clean and Safe Nuclear Energy

Quote:
Though Cassidy remains an advisor at Google, he has quietly started a new company, Apollo Fusion. On Friday, a website for the firm, which previously consisted only of a definition of the phrase “nuclear fusion,” was updated to include a vision statement that gives a tantalizing peek into Cassidy's plans.

“We're working on revolutionary hybrid reactor technology with fusion power to serve safe, clean, and affordable electricity to everyone,” reads the site. “Apollo Fusion power plants are designed for zero-consequence outcomes to loss of cooling or loss of control scenarios and they cannot melt down.”

The website asserts that Apollo Fusion's reactors will be inexpensive to build, cost competitive with traditional means of generating electricity, and flexible enough to serve both small villages and large cities. It says Cassidy is working with Ben Longmier, the founder of a company called Aether Industries, which made equipment for high-altitude research and was acquired by Apple in 2015. Longmier also has a PhD in plasma physics and advanced degrees in physics and nuclear engineering.


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PostPosted: Apr 04, 2017 8:29 pm 
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I wish these people the best with their fusion-fission hybrid reactors but I have little hope in their success. While I believe that a hybrid reactor design is not very feasible I do believe that people investing in this will bring good things. This is especially true when we see private individuals put their own money behind the effort, they have a motivation for success that no government agency can match.

I doubt that these people from Google will ever bring us a fission-fusion hybrid reactor. I do believe that they can bring us inexpensive and safe nuclear power.

The Department of Energy has been promising energy independence for decades now and with not much to show for it. What we have seen in the development of inexpensive and reduced carbon energy has come largely from private investment, not government subsidy. I now strongly believe that energy independence for the USA will come not from the government but in spite of it.

I do have some hope with the election of Trump as POTUS and his picks for cabinet. We keep hearing about an "all the above" strategy for energy but in practice so many things have been kept from consideration. We may soon see people that will actually consider "all the above" as options for energy. This includes the improbable success of fission-fusion hybrid reactors.

We'll probably see nuclear power advance in the USA over Nancy Pelosi's and Harry Reid's dead bodies. I do not wish them ill but may God forgive me for not shedding a tear when I read their obituaries.

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Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.


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PostPosted: Apr 06, 2017 4:03 am 
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When you wrote "Yet another fusions/fision hybrid," where you referring to mine? http://www.google.com/patents/US20120014491


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PostPosted: Apr 06, 2017 8:32 am 
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Ive thought about using fusors to pump neutrons into cores myself - largely in an attempt to consume tritium produced by a CANDU in a way that can significantly improve fuel economy - and/or provide extra reactivity to allow xenon override without boosters or adjusters.


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PostPosted: Apr 07, 2017 10:40 pm 
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E Ireland wrote:
Ive thought about using fusors to pump neutrons into cores myself - largely in an attempt to consume tritium produced by a CANDU in a way that can significantly improve fuel economy - and/or provide extra reactivity to allow xenon override without boosters or adjusters.


How much tritium is produced in CANDU, or any fission reactor? Is that enough to fuel to make a fusion reactor worth the trouble? Is tritium even a good fuel to use? Or, are you simply suggesting that a fusion reactor is just one means to dispose of tritium?

I did some reading on how fission-fusion hybrid reactors could work and I'm still not convinced of the merits. I will say that a fission-fusion hybrid system does make fusion look a lot more attractive. I say this because fusion is hard, and a way to make it easier is to find a way to deal with one big problem it has, containing neutrons.

Confinement systems for fusion largely rely on the electric/magnetic properties of a plasma. We know how to confine charged particles, but neutrons don't have a charge. One means to deal with this is a choice of fuel that produces as few neutrons as possible under fusion, but this has a cost. Aneutronic fusion requires exotic fuels that are not as reactive as more easily obtained neutron producing fuels. By placing a blanket of material that can capture those neutrons, and do something useful with them, then one problem is solved. Then the problem is making use of those neutrons that were captured.

By using fissionable material to capture the neutrons lost in fusion this can possibly make fuel choices for a fission reactor simpler. Neutron bombardment can turn worthless U-238 into valuable Pu-239, or thorium into U-233. Or maybe Li-6 into Li-7. A fusion reactor does not have to be used to produce electricity or fuel for fission. It's value could be from it's ability to produce neutrons for bombarding all kinds of materials. I remember a Youtube video from Dr. Stephen Boyd where he talked about the chemistry applications of a molten salt reactor, well I believe a lot of that could apply to a fusion reactor too.

Using deuterium as fuel can make the fusion reactor much smaller than what would be required from, as an example, an aneutronic protium-boron reactor. The neutrons released can bombard a molten salt blanket/coolant/target material. This material can carry away the heat produced and run a turbine, not to produce electricity for sale but to minimize energy losses from heat. Any electricity produced would be used to drive the fusion containment. The material soaking up the neutrons could be fission fuel, fission products for disposal, or for producing any of a number of isotopes that have value in medicine and industry.

The example of dealing with xenon can be dealt with, IMHO, with things less complex than a fusion reactor. This is doubly so if we're talking about coupling this fusion reactor with a molten salt reactor. I can see the value in using a fusion reactor in dealing with some problems from fission reactors, and vice versa. What I have trouble seeing is the need to couple the two reactors directly.

We can achieve the same benefits of having both fusion and fission by having them as independent reactors. For example the tritium produced in a CANDU can be collected and shipped to a fusion reactor. The fusion reactor can use the tritium as fuel to bombard thorium, which would be collected and shipped to a CANDU. By tying the two directly, such as sharing the same coolant system, means if one goes down for maintenance then the other must be shut down too.

Perhaps these latest proposals allow for some level of independent operation of the fission and fusion reactors, but that was not apparent from what I've seen. I'm a bit frustrated at their lack of detail in their proposals so far but I do see the need to not give out information to potential competitors.

Again, I wish them success but I'm not convinced that they will find it. Even a failure can teach us a lot, so we will get value from their efforts either way.

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Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.


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PostPosted: Apr 08, 2017 11:33 am 
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Kurt Sellner wrote:
E Ireland wrote:
Ive thought about using fusors to pump neutrons into cores myself - largely in an attempt to consume tritium produced by a CANDU in a way that can significantly improve fuel economy - and/or provide extra reactivity to allow xenon override without boosters or adjusters.


How much tritium is produced in CANDU, or any fission reactor? Is that enough to fuel to make a fusion reactor worth the trouble? Is tritium even a good fuel to use? Or, are you simply suggesting that a fusion reactor is just one means to dispose of tritium?


Tritium is the onyl fuel for which high power fusion seems plausible any time soon. D-T fusion is the best choice for that, and if we are merely using it to pump more reactivity into a core to overcome xenon the fact it makes 14MeV death-ray neutrons is actually a plus as even in depleted fuel their fission probability is close to one.

The concept of using it to overcome xenon override would be to allow the reactor to start up part way through a xenon-poison out without any of the problems with fuel consumption (adjusters significantly reduce fuel economy, producing more waste) or safety (booster rods produce huge thermal powers, indeed they were locked out at Bruce A, partially because calculations showed that if forced cooling to them was lost they would melt down in five seconds) of the other options.

They allow you to add 20-30mk for an hour or less quite feasibly, which is what you need, as the reactor is powered back up it will start to burn away xenon until it reaches a lower power equilibrium. And if power to the cooling pumps is lost then power to the fusors can be cut off and the reactor is subcritical without them.
The fact that there is a net energy loss, even with energy recovery, is largely irrelevant in this situation.


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PostPosted: Apr 08, 2017 3:06 pm 
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The number of atoms of tritium produced per atom of actinide fissioned in a CANDU is very small. So, as a fuel source, it would be rather trivial...


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PostPosted: Apr 08, 2017 4:07 pm 
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E Ireland wrote:
Tritium is the onyl fuel for which high power fusion seems plausible any time soon. D-T fusion is the best choice for that, and if we are merely using it to pump more reactivity into a core to overcome xenon the fact it makes 14MeV death-ray neutrons is actually a plus as even in depleted fuel their fission probability is close to one.


I understand that D-T and T-T fusion are two of the most likely candidates for fusion power of only a handful from which we understand as possible energy and/or neutron sources. I look at the Wiki page on this and I see the list they've made.
https://en.wikipedia.org/wiki/Nuclear_f ... _reactions

From that list none of them will produce more neutrons than what are put in, assuming the tritium is sourced from a fission reactor. The closest there is the T-T fusion which provides 2 neutrons out, which if used to bombard heavy water then one could get close to something sustainable. This means relying on something like a CANDU to make up for the neutrons lost. Which gets to this...

Cyril R wrote:
The number of atoms of tritium produced per atom of actinide fissioned in a CANDU is very small. So, as a fuel source, it would be rather trivial...


So, how do we size the CANDU portion of this fusion-fission hybrid to the fusion portion to reach some kind of sustainable system where neutrons are best utilized? This assumes that heavy water, or some other hydrogen carrying blanket, is used on the fusion side. Using water for cooling and/or moderation is problematic, as evidenced by past nuclear fission accidents.

This gets back to my point, how is a fission-fusion hybrid reactor system better than simply having separate fission and fusion reactors? If we can make a D-T or T-T fusion reactor then we have a market for the tritium created in CANDU and CANDU like reactors. We don't need to marry them together for this to work. They don't even need to be on the same site. Tank up the tritium as it is produced and filtered from the fission reactor, when there is enough to make a shipment worth the effort then bring it to the fusion reactor.

Basically I'm having trouble understanding the advantages of a fusion-fission hybrid system. A big part of this goes back to my earlier expression of frustration on the secrecy on how these people plan to make it work, which is something I do not expect to be resolved any time soon. Another part is just my general ignorance of nuclear power, as I've put in my signature line I do have a background in engineering but I'm no nuclear engineer. This is also is something I do not expect to be resolved any time soon.

Even though I'm no nuclear engineer I can do some algebra. I run some of the numbers on a napkin and they don't add up. It's not that there's a dispute over a few percentage points, there's orders of magnitude mismatches here. Now, I did read some paper somewhere where they tried to resolve at least some of these problems by making the fusion-fission reactor very large. I recall it was something like 5 GWt and 2 GWe. That's huge.

I remember reading about the polywell fusor and looking at some of their math. At the time (and perhaps this continues) the people working on the polywell fusor were getting funds from the US Navy. What I recall was that there was no way a polywell fusor would fit on even the largest of aircraft carriers. The confinement structure would be too large to fit in the hull. They had the goal of making the fusion reaction a net energy producer on it's own so perhaps that is not a fair comparison for a fusion-fission hybrid.

If we assume the fuel for the fusion comes from fission then the fission reactor will have to be quite large compared to the fusion reactor. If we size the fusion reactor in a way to minimize neutron and/or energy losses then it becomes very large compared to the fission reactor, or just simply very large. All of this to solve what seems to be some relatively minor issues inherent to fusion and fission reactors that, with my limited understanding of the problems, could be resolved more easily by other means.

Thanks Cyril R and E Ireland for answering some of my questions, I really appreciate it.

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Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.


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PostPosted: Apr 21, 2017 5:51 pm 
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Cthorm wrote:
Sounds to me like it's just a dissertation. A concept with the sole purpose of finishing school.


Considering that Dr. Woolley died on August 16, 2016, you are likely correct.

Obituary


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