Fission news(I know blasphemy )

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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KitemanSA
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Re: Fission news(I know blasphemy )

Postby KitemanSA » Thu Feb 09, 2017 6:59 am

Here is what you do with "Nuclear Waste"
First BURN IT,
then BURY IT!
As it happens, the waste everyone keeps fretting about (called Spent Nuclear Fuel (SNF) but which I like to call Lightly Used Fission Fuel (LUFF)) is actually about 97% perfectly good UNspent fuel and only about 3% real waste. The UNspent fuel should be extracted and used in any of the GEN IV+ designs that can consume it. The rest, the real waste, will then be as safe as the dirt it came from in about 300 years. The LUFF can be safely stored in dry casks until the UNspent fuel can be burned in one of those GEN IV+ reactors. The waste can then be encapsulated in some sort of container that will last for 300 years and I would then cement the capsules into the bottom of the mine it came out of (or any other suitable place) and bury it there.

raelik
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Re: Fission news(I know blasphemy )

Postby raelik » Thu Feb 16, 2017 8:48 pm

Carl White wrote:
D Tibbets wrote:Replacing the primary loop every 4 years sounds very expensive- working underground, ripping out radioactive tubes that carried the decay product contaminated pipes that formed the primary cooling loop, would be time consuming and expensive and require up to many thousand of years of safe storage.


Why not build redundantly then? Five sets of tubes, switch to the next set every few years. Sure, it increases the cost to build, but lowers the lifetime cost of the reactor.


As per the design, each Power Module is composed of a pair of Cans, with only one active at a time. When the moderator needs to be replaced, the fuel is transferred into the passive can. The now-cooling Can remains in the module for a few years to let most of the residual heat dissipate, and is then replaced with a new Can. Another year after that, the active can will need replacing, so the cycle begins again: transfer fuel, wait 3 years, replace old Can, wait another year.

D Tibbets
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Re: Fission news(I know blasphemy )

Postby D Tibbets » Fri Feb 17, 2017 1:02 am

I, from my distant perspective, would not agree that regulation has sunk the fission nuclear industry. The obvious radiation problems, engieneering lies and multiple dire failures has. The management that has caused directly the most severe accidents has not helped either. A better perspective of what is possible may be in the Navy nuclear program. Much more tightly controlled, thanks in part to the uncompromising culture emplaced by Admiral Ricktover (sp?). The Navy may also have suppressed some information. Certainly the Russian Navy has an apparently less stellar record. The prior engineering and management failures have earned an appropriate suspicion concerning claims. New technology with very clear advantages and resistance to failure modes is critical.Vast improvements on what goes on when things are working is needed; as is, of course, much less dire failure modes.

This is where fusion has a large advantage. There is only a tiny amount of potential fuel in the reactor at anytime. Neutron activation is still very important (except for P-11B (where it is only mildly of concern). Fusion reactors might still produce spectacular failures- primarily in very large machines like low Beta tokamacks with their huge superconducting magnets. An uncontrolled quench could lead to a impressive explosion. Cleanup would be trivial compared to a typical fission plant reactor explosion, But, scattering reactor parts, including radioactive parts and tritium is possible. The financial costs would still be high in this case and the public may also be scared. Smaller reactors that are economical is important not only for building and operational concerns, but also for the impact of any failures real or perceived.

Dan Tibbets
To error is human... and I'm very human.

KitemanSA
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Re: Fission news(I know blasphemy )

Postby KitemanSA » Sat Feb 18, 2017 9:10 am

The issue is, Dan, that the "obvious radiation problems" are part and parcel of those regulatory burdens that stem from a basic lie. That lie results in ALARA (As Low As REASONABLY Achievable) being implemeted as "As Low As Ridiculously Achievable). That costs BIG money.

KitemanSA
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Re: Fission news(I know blasphemy )

Postby KitemanSA » Sat Feb 18, 2017 9:15 am

Dan,
Your point about a "tiny amount of fuel" needed for fusion also applies to Liquid Fluoride Thorium Reactors (LFTRs). They only need as much fissile material as required to achieve criticality because the reactor can be continuously refueled. Don't refuel and the reactor stops.

D Tibbets
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Re: Fission news(I know blasphemy )

Postby D Tibbets » Mon Feb 20, 2017 12:55 pm

KitemanSA wrote:Dan,
Your point about a "tiny amount of fuel" needed for fusion also applies to Liquid Fluoride Thorium Reactors (LFTRs). They only need as much fissile material as required to achieve criticality because the reactor can be continuously refueled. Don't refuel and the reactor stops.


Good point if assume that the fission reactor gets most of its useful output by manipulating and harvesting the heat from the actinide series decay products. If most of the useful energy is from the fission of the parent uranium, plutonium or thorium, then the decay products would build up just as with a conventional fission reactor. The reactor would need to handle the daughter products, neutron conversion directly. Collecting the products and processing them in a subsequent step partially does the same, but large intermediate stock piles, etc would be generated. A complex process that would present multiple potential failure points where highly radioactive liquids or gasses could be released.
The difference with fusion (except for tritium handling) is that the induced radiation is mostly in solid materials (I think). It is easy to handle a bunch of radioactive pipes for a few years to decades. Careful selection of materials from a neutron activation perspective is important for both fusion and fission , but I think much more relevant for fusion as this is the sink for most of the time relevant radioactive concerns.

Certainly fusion can produce radioactive concerns too. Especially if choices are made for this purpose. The neutron source from D-T or D-D fusion can breed almost any isotope you desire. The ease of producing weapon grade plutonium, etc becomes (in working smaller reactors) much more of a proliferation problem.

Dan Tibbets
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D Tibbets
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Re: Fission news(I know blasphemy )

Postby D Tibbets » Mon Feb 20, 2017 1:35 pm

KitemanSA wrote:Dan,
Your point about a "tiny amount of fuel" needed for fusion also applies to Liquid Fluoride Thorium Reactors (LFTRs). They only need as much fissile material as required to achieve criticality because the reactor can be continuously refueled. Don't refuel and the reactor stops.



this could stop the fission promply, but this is nothing new. Even without molten salt approach, fuel rods have been developed and tested that expand as they heat to the point that this passive process will reduce fission below criticallity even if mechanical devices such as control rods fail. The problem is and remains the radioactive decay products that have been produced. Their heat production is due to radioactive decay, not fission. You cannot change the half lives (ignoring rapidly applied neutron transmutations- which would require the ongoing neutron source from fission or fusion). The continued heating from the radioactive decay after there is a coolant failure is what has caused the major accidents. That and some exceedingly stupid management/ tests. If a salt reactor can passively dump this soup of heating fluid into a larger volume with adequate passive cooling capacity, then this runaway meltdown can be avoided despite multiple point failures. The harvesting of a significant amount of power from these native or transmuted decay products can change the dynamics some, but the proof against meltdown is still the number one priority.

To repeat my understanding of the process-the decay products contibute adout 10% of the heating in an active 'mature' fuel rod. If the fission is stopped, 90 percent of the heating stops promply, but that still leaves ~10 %. If a plant is producing 1 GW thermally, at shutdown it would still be producing ~ 100 MW of heat. That is a lot of heat to manage if your cooling system has failed. The decay products decay with a bunch of half lives which results is a rule of ~ 10/7. For every seven fold interval of time the radiation decreases ~ 10 fold. This also has consequences for nuclear bomb fallout. At ~ 1 hour after shut down, perhaps ~ 100 MW of heat is being produced. This drops to ~ 10 MW at 7 hours, ~1 MW at 2 days, 100 KW at 2 weeks, 10 KW at ~ 4.5 months, etc. This is why fuel rods have to be actively cooled for several days. After that a swimming pool of water may be adequate. A few months later and a small tank may be enough, and after several years the waste may be stored in concrete and steel barrels.My understanding of a liquid salt reactor failsafe is that a plug in the bottom of the reactor vessel will melt as the liquid salt medium heats, and the core fluid containing any radioactive elements drains into a relatively large swimming pool that can passively cool the sludge. If the salt eventually cools and solidifies the cleanup or entombment of the 'Contained Spill' is probably much easier. But a salt suggests a high water solubility so keeping the solidified sludge dry is critical. What you do to this radioactive medium to convert or extract radioactive products is not directly related to the spill concern. The exception, as I have said is if the neutron manipulation occurs in realtime as the reactor is running. Here the more efficient recovery of heat energy with conversion to useful heat or electricity allows for small feed rates of the parent fissile material, and thus small scales as to the amount of fissile and to a degree radioactive decay fuel in the reactor at any time.

Dan Tibbets
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KitemanSA
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Re: Fission news(I know blasphemy )

Postby KitemanSA » Tue Feb 21, 2017 1:46 am

When you have Molten Salt Reactor, you can have a continuous fission product removal system too. You almost need one to get to true breeding level with a Liquid Fluoride Thorium Reactor (LFTR). With such a FP removal system, they don't build up and they don't present a problem.

But even if you leave the products mostly in, the therml mass of the system can be o high that decay heat is not an issue.

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Re: Fission news(I know blasphemy )

Postby D Tibbets » Tue Feb 21, 2017 2:47 am

KitemanSA wrote:When you have Molten Salt Reactor, you can have a continuous fission product removal system too. You almost need one to get to true breeding level with a Liquid Fluoride Thorium Reactor (LFTR). With such a FP removal system, they don't build up and they don't present a problem.

But even if you leave the products mostly in, the therml mass of the system can be o high that decay heat is not an issue.


Good point. I had not appreciated that a liquid fuel mixture could be filtered, differentially centrifuged, etc. in real time. Something which you could not do with a solid fuel rod. This would allow the real time manipulation of the fuel composition. It does introduce another source of leaking though. The equipment that has radioactive material flowing through it could break down or leak. It changes the picture somewhat but introduces some additional pathways that needs to be carefully controlled. Meltdown may become much less of a problem or possibility, but radioactive leaking is still an issue, though it may be orders of magnitude less than in a full meltdown or even a partial meltdown.

A supposition is that a possibility of a containment building failure may be much less also.. In one of the Japanese tsunami reactors, after coolent failure and shutdown. The residual heating in the reactor vessel resulted in the zirconium coated fuel rods reacting chemically with the hotter water with hydrogen being produced. This lead to a hydrogen explosion in the reactor containment vessel/ building that demolished it. A liquid salt reactor may avoid zirconium or other highly chemically reactive elements that compounds the problems once nominal conditions are lost. That and the suppression of runaway heat by the passive dumping of the heating reactants into a larger thermal mass reservoir with associated greater passive heat loss mechanisms- radiation and conduction- convection being mostly lost with coolant flow interruption.

dan Tibbets
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RERT
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Re: Fission news(I know blasphemy )

Postby RERT » Tue Feb 21, 2017 12:05 pm

The Thorcon reactor (root post) design has a plug at the low point of the primary fuel flow circuit, i.e. the flow of fission reactant. They say that if the flow overheats, the plug melts, and the reactant flows into a tub below called the 'Fuelsalt Drain Tank' (FDT). They make a point of saying that the operators cannot disable this feature. In the FDT the reaction is then expected to stop immediately because of lack of moderator, and the FDT is passively cooled to a safe shutdown. One would have to guess that they were serious enough to have included heating from waste decay in their calculations of passive cooling requirements.

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Re: Fission news(I know blasphemy )

Postby paperburn1 » Wed Feb 22, 2017 1:33 pm

The only real main advantage I see from the thorium reactors that are liquid-based is an things go bad they are relatively easy to contain and control. There will still be huge cost associated with cleanup but I unlike the Fukushima event cleanup can occur at the plants operators leisure rather than dictated by necessity. I think if going to have a nuclear proliferation of reactors that the safeguards or style of reactors, mandatory because let's face it when things go bad in a boiling point reactor, things go bad a boiling point reactor.
I am not a nuclear physicist, but play one on the internet.

hanelyp
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Re: Fission news(I know blasphemy )

Postby hanelyp » Wed Feb 22, 2017 6:30 pm

There's a very simple design feature possible with molten core reactors, where if the cooling system fails the fuel automatically drains into a pan where the then subcritical mass has plenty of surface area to passively cool and remain at safe temperatures.

As for fission products, whether you remove them or leave them in the fuel, the heat they generate has to be removed. The particular fission products you'd most want to remove are fission poisons, the most prominent one being the noble gas Xenon, which is relatively easy to remove from molten fuel.
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RERT
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Re: Fission news(I know blasphemy )

Postby RERT » Thu Feb 23, 2017 9:20 am

https://wattsupwiththat.com/2017/02/22/fear-of-nuclear-part-2/

A bunch of stuff I didn't know about the "linear no threshold" (LNT) hypothesis on radiation induced cancer, and how experts disagree. Also very interesting datapoint a on the lack of excess cancers due to higher background radiation, and a surprise from Taiwan on the benefits of low radiation levels (!?).

KitemanSA
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Re: Fission news(I know blasphemy )

Postby KitemanSA » Thu Feb 23, 2017 8:56 pm

RERT wrote:https://wattsupwiththat.com/2017/02/22/fear-of-nuclear-part-2/

A bunch of stuff I didn't know about the "linear no threshold" (LNT) hypothesis on radiation induced cancer, and how experts disagree. Also very interesting datapoint a on the lack of excess cancers due to higher background radiation, and a surprise from Taiwan on the benefits of low radiation levels (!?).

RE: LNT, check out:
http://radiationeffects.org
http://dose-response.org
and http://X-LNT.org

KitemanSA
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Re: Fission news(I know blasphemy )

Postby KitemanSA » Thu Feb 23, 2017 9:07 pm

paperburn1 wrote:...There will still be huge cost associated with cleanup ...

Seems highly unlikely since any leakage would either freeze on the leak, plugging it, or drip to the floor where it would freeze and be easily chipped and swept then hit with the nuclear equivalent of a Stanley Steemer.


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