This thread is nuclear (nuclear power discussion)

Absent from this discussion are the dangers of nuclear weapon proliferation inherent in the present designs of power generation. The pressurized water reactor design was chosen for development in order to generate plutonium for nuclear weapons. That choice was kept secret, and lies, still believed, put out about peaceful use of nuclear technology.

If a large part of the world is to decarbonize using nuclear power, it must not be with technology that produces significant high level waste. Turning that waste into dirty weapons is inevitable, and extraction of plutonium hard to avoid.

This is simply false. PWRā€™s were in part chosen because they are resistant to nuclear proliferation.

There are countries with PWRs that have no nuclear weapons (South Korea, Japan, Taiwan, among many others) while there are countries with nuclear weapons that have no power reactors at all (North Korea, Israel).

Thereā€™s several fairly simple reasons for this.

For starters, PWRā€™s donā€™t produce as much plutonium as reactors designed for WGPu (Weapons-grade plutonium) production and theyā€™re not amenable to online refueling. This latter point creates a considerable problem for a nation state intent on producing WGPu with a power reactor and separating it for weapons production. For one, you cannot expose the fuel to neutron flux beyond a relatively short period or it will turn into RGPu (Reactor-grade plutonium). A fraction of your precious Pu-239 absorbs an extra neutron, turning into Pu-240. That Pu-240 has a tendency to spontaneously fission. So, once you exceed a small percentage of Pu-240 it is no longer useful for weapons.

Additionally, if a power reactor used for energy production begins to shutdown frequently for re-fueling, the IAEA tends to notice.

Further, a power reactor is quite a lot more expensive to build than the kind of reactor used for weapons production. You have to operate them at high pressure (to get the high temperature), high temperature, and include a lot of power conversion equipment that you simply donā€™t need.

Instead, take a look at how the Americans, Soviets, and British produced the bulk (all?) of their weapons-grade material. Windscale used air cooling to blow air through graphite channels with fuel bundles that were continuously being pushed through to the back from the front reactor face. Hanford-B did something similar, but water cooled their reactor. These were relatively simple designs - horizontal fuel channels in what was essentially a large block of graphite - and they had large fuel re-processing facilities co-located to these reactors and generated an absolutely enormous amount of waste in the process.

Regardless, if weā€™re going to criticize nuclear fission for the potential for WGPu proliferation, then the same kind of criticism should be applied to any nuclear fusion projects that use neutronic fusion (which is almost all of them), as the same risks apply (or may be even greater due to the higher neutron energies involved).

Lastly, a nation state can skip the plutonium production thing and just enrich weapons-grade uranium, of which you donā€™t need a reactor for. This is what was done with the ā€˜Little Boyā€™ bomb dropped on Hiroshima.

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IHMO Thatā€™s not the same thing.

I think @r3Dg has it about right,

The plutonium is a bonus, and might be why Thorium was neglected.

But look at Iran for a more efficient breeding system for weapons grade.

There isnā€™t the need to benefit the population like the energy firms do.

Manhattan could well have evolved into a longer running program to improve the yield of weapons grade material, and just kept it all under wraps, much like Iran etcā€¦
The truth would have crept out, but the material would have been gained by then.

More a worry to me, is the actual active use of ā€œdepletedā€ uranium, and other dirty components in otherwise conventional weapons, if you gonna worry about side products.
Very few Nuclear weapons themselves have been used in anger.

its not the Plutonium that is why proliferation becomes a question with Thorium its the U-233. If you refine on site you could in theory remove U-233 while the Thorium is breeding and burning off other fissile fuels.

In reality it seems best to just leave everything in and just wait for decay and burn and only remove the non fissile materials that could poison the reaction.

It is clearly not a 100% fool proof solution as removing the U-232 would require removing the U-233 which could in theory be refined out for weapons production.

The high Gamma radiation makes all of this difficult but not impossible.

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Posted before

Tl;dr we really should consider thorium and molten salt reactors

Thank you for your detailed response.

Iā€™d be interested in seeing the calculations.

Iā€™ve heard of replenishable blankets so there wouldnā€™t be down time associated with changing it out after it degrades; but itā€™d still produce irradiated waste, and I donā€™t think they ever figured out how to do the neutron multiplication with the fancy liquid blankets.

DU is too useful at armor penetration to go away. Itā€™s performance exceeds what itā€™s density implies it should be due to fracture mechanics.
It might be possible to alloy it to decrease itā€™s pyrophoric effects to reduce the amount of oxides it gives off after impact however.

Seems like Japan has realized that having a stable energy supply is important.

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Hereā€™s a plot of Specific Dose Rate (Sv/hr-kg) versus Time after 1 year of irradiating a vacuum vessel. I calculated this using FISPACT. This is in a more compact, high power tokamak based on the ARC design - [1409.3540] ARC: A compact, high-field, fusion nuclear science facility and demonstration power plant with demountable magnets
DoseRate_Level

For reference - Fukushima Daiichi Accident - World Nuclear Association

A radiation survey map of the site made in March 2013 revealed substantial progress: the highest dose rate anywhere on the site was 0.15 mSv/h near units 3 and 4. (Soon after the accident a similar survey put the highest dose rate at 300 mSv/h near rubble lying alongside unit 3.) The majority of the power plant area was at less than 0.01 mSv/h.

That means after 100 years, Inconel 718 would release 1/3 the worst dose rate ever measured at Fukushimaā€¦ And continue to be worse than it was 2 years after the accident for 10,000 years (Inconel 718 sits at around 9E-2 Sv/h-kg for 10,000 yr due to the half-life of Ni, Nb, and Mo isotopes). 316L is an order of magnitude lower than this, but still thatā€™s quite bad. Itā€™s why we are developing Reduced Activation Ferritic Martensitic Steels and Vanadium Alloys to replace Inconel 718 and 316L Stainless Steel near high energy neutrons.

Neutron multiplication isnā€™t the hard part with liquid blankets, thatā€™s achieved by putting in a material with a high (n,2n) cross section, like Pb or Be. The tricky part is separating the tritium from the liquid blanket. Additionally the blanket is a lifetime component cause the depletion of the breeder is actually quite slow.

What you need to replace are the structural materials surrounding the blanket. The blanket tank could maybe be designing for 10 years, depending on the operating temperatures and allowable cost. The vacuum vessel would be hard pressed to last more than 5 years (6 months if you made it out of Inconel 718 due to Helium Embrittlement). This is for a compact Tokamak like ARC, not DEMO.

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Romania might actually be building a plant with SMRs in a few years. This could be the start of something interesting :crossed_fingers:

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In 2020 the US Department of Energy calculated the Levelised Cost of Electricity per MWh for a variety of different sources.

  • Advanced Nuclear came in at $69.39.
  • Onshore Wind came in at $36.93.
  • Geothermal came in at $36.40.
  • Standalone Solar came in at $32.78.

(Not the complete list.)

Given that Solar was already less than half the price of Nuclear back then, and the gap between them has already widened, and will continue to widen over time, how can Nuclear hope to compete in anything resembling a ā€˜freeā€™ market?

Ignoring ā€œtoo cheap to meterā€ Fusion that is not yet a reality and might never be a reality, is there anything on the Fission front that can make Nuclear more competitive? It is viable to run (some types of) Fission reactors at full capacity at night only (and spells of poor weather), then idle them during the day?

Absent some sort of corporate welfare program ā€” justified on the basis of ā€˜energy securityā€™ ā€” I canā€™t see how Nuclear will survive.

There has been a lot of good and interesting technical discussion about Nuclear options so farā€¦ but ā€˜the marketā€™ doesnā€™t care about anything other than money. Iā€™m struggling so see how (traditional baseload 24/7) Nuclear will survive, given the numbers. Any ideas?

How much electricity does solar panels produce during the night?

If itā€™s not viable to ONLY run fission reactors at night, then solar generates the same amount as fission. Your point, therefore, is ā€¦ ?

My pont is both solar and wind are intermittent energy sourcesā€¦ So you always need a backup. Currently we use coal/natural gas for the majority of this. Iā€™d like to see nuclear to take over thisšŸ˜‰

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Itā€™s so stupid. If your pro nuclear your pro both forms thatā€™s the litmus test. Another litmus test is that if you give any sort of crap about climate change you are pro nuclear fission and pro fusion but you want fission to proliferate firstā€¦ If you donā€™t have that opinion I know you have other objectives and motives than say the climate changing

This project is cool but fusion is still a few decades our regardless

Yep, I can get behind Nuclear being the backup for when the sun donā€™t shine and the wind donā€™t blow, but is it viable to operate Fission reactors this way?

Every single output graph for fission reactors that Iā€™ve ever seen has them virtually flatline ā€” producing the same output for months on end. Although adjusting the depth of the rods sounds like a simple enough process, is there some sort of technical reason why it seems like no fission reactor is operated this way?

Like, would dunking them in and out once a day cause thermal cycles that deteriorate the rods at an unacceptably high rate?

Can fission reactors be operated like ā€˜peakersā€™?

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Youā€™re missing the pointā€¦ We donā€™t need solar or wind if we just focus in nuclear power.

Whilst technically true, given that nuclear is already over 2x as expensive as solar/wind, and getting relatively more expensive every year, that is not a realistic future.

In a realistic future, nuclear needs to eke out an existence in the niches that the cheaper forms of energy canā€™t fill. That means a generation pattern less like baseload, and more like peaking. I am wondering if that is actually possible.

How much land are you willing to destroy for solar and wind? The amount of space required to produce the same energy output from a single nuclear power plant Vs solar/wind is probably 100s if not more.

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Source

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