The Nuclear Power Thread

[clancy688]

Seriously, I'm getting impression there that pro nuclear people want to be elite underground (vs convincing anyone that nuclear has future).

And I'm getting the impression that the contra nuclear people want to be elite underground as well, convincing everyone that nuclear power has no future.

scnr

 

[Dmytry]

If only. So far I can't even convince pro-nuclear that Fukushima even in principle could damage nuclear industry big time. They don't see the logical reason why it should, so the idea is that it won't.

 

[Astronuc]

If only. So far I can't even convince pro-nuclear that Fukushima even in principle could damage nuclear industry big time. They don't see the logical reason why it should, so the idea is that it won't.

Sure it will have an effect - and it has.

NRG withdraws from Texan project
http://www.world-nuclear-news.org/NN-NRG_withdraws_from_Texan_project-2004114.html
20 April 2011

Italian government puts brakes on nuclear vote
http://www.world-nuclear-news.org/NP_Italian_government_puts_brakes_on_nuclear_vote_1904112.html
20 April 2011

 

[Dmytry]

In soviets, head of minatom IIRC said something like, science requires sacrifice. After Chernobyl. A great pro-nuclear advocate he was, eh. I think what was really bad about Fukushima, is all the 11th coverage and news exceeding the worst expectations. I really wouldn't bet my money that Japanese won't start phasing out nuclear.
Just for laughs I looked up insurance rates on nuclear power plants. They apparently estimated 1/1000 probability of $300M liability accident per reactor year, that order of magnitude (collecting 400K$/year per reactor, max payment around 300M , that's for liabilities). Then there is
http://en.wikipedia.org/wiki/Price–Anderson_Nuclear_Industries_Indemnity_Act
It would seem to me that economically speaking, nobody's - not owners either - are trusting those immensely low risk figures that have been circulating (1 in 30 000 core-years etc), nobody's willing to bet a lot of money that those figures are correct.
I really dunno, if a nuclear plant is to be constructed near my house - why exactly should I trust it more than an insurance firm would? Which gives it 1% probability of serious accident in 10 years for single reactor, which in my book is a little on the not so nice side to be honest. Sure I'd rather live next to NPP than to coal fired plant, but i'd even rather have my own solar panel and energy storage, even if it costs a lot more. And I'd definitely invest in radiation monitor that is on 24/7 . 1% per 10 years is not very good neighbourhood.

 

[edpell]

LFTR (liquid fluoride thorium [nuclear] reactor) looks like a good solution to our energy needs. Lots of info at www.energyfromthorium.com An initial charge of U233 is used to breed U233 from a thorium blanket and produce energy.

It produces much less waste and the waste is shorter lived. It uses only room pressure unlike LWR that use high temperature water under high pressure to keep it from flashing to high pressure, high temperature steam (hence the need for the large thick pressure dome in case of failure not needed with liquid thorium fluoride/liquid uranium fluoride).

This type of reactor was run at Oak Ridge in the 1960s and is under development in France and China currently. Once they have a large source of electricity they can make synthetic methanol and dimethyl ether for transportation fuels.

 

[Astronuc]

Non-proprietary presentation to NRC by GEH/GNF on current technology developments.
http://pbadupws.nrc.gov/docs/ML1027/ML102700236.pdf (~24 MB file, so use save target as)

 

[zapperzero]

LFTR.

Liquid uranium fluoride. 800 degrees Celsius or even more, for process heat applications. No containment. Heat exchanger where water is separated from molten fluoride salt by just the thickness of a steel pipe, that's supposed to last decades, without embrittling from either fluorine or neutrons.

A radioactive fuel re-processing plant that deals with molten fluoride salts, next to every reactor. Plutonium, produced and separated on an ongoing basis.

If the thought of all this doesn't send a chill up your spine, I don't know what will.
There is a reason why those reactors never got past technology demonstrator phase. The knowledge needed to make them reliable just wasn't there. It still isn't.

 

[zapperzero]

No business is going to artificially inflate the price of their nuclear supply so no one can afford it - lose customers, which lowers demand - which means they have no reason to build new coal plants - would you spend billions when there's no money coming into cover it and no demand there?

http://en.wikipedia.org/wiki/Enron#California.27s_deregulation_and_subsequent_energy_crisis

An energy producer artificially inflating price and thus driving demand destruction. The price point where maximum profit ratio is found is never the point at which the most units of a certain product could be sold.

EDIT: that's partly because nothing in the energy markets really is a fungible commodity, electricity least of all.

 

[mheslep]

EDIT: that's partly because nothing in the energy markets really is a fungible commodity, electricity least of all.

? Nearly the opposite is true, as most fuels are close to being commodities especially in raw form, less so the as they are processed, modified, and blended to meet the regulations of particular local markets.

 

[mheslep]

Liquid uranium fluoride. 800 degrees Celsius or even more, for process heat applications.

I speculate that most engineers would rather deal with a high temperature, low pressure system than a lower temperature, high pressure (153 atm for a light water PWR) system.

No containment. Heat exchanger where water is separated from molten fluoride salt by just the thickness of a steel pipe, that's supposed to last decades, without embrittling from either fluorine or neutrons.

A radioactive fuel re-processing plant that deals with molten fluoride salts, next to every reactor. Plutonium, produced and separated on an ongoing basis.

Reprocessing from the spent fuel of a U235 light water reactor produces Pu upon re-processing, not so for Th based LFTR (in significant amounts).

...
There is a reason why those reactors never got past technology demonstrator phase.

Yes, and that's well known to be the need for an infrastructure that lent itself to making weapons grade material, not reliability. http://www.wired.com/magazine/2009/12/ff_new_nukes/all/1"

Uranium reactors had already been established, and Hyman Rickover, de facto head of the US nuclear program, wanted the plutonium from uranium-powered nuclear plants to make bombs. Increasingly shunted aside, Weinberg was finally forced out in 1973.

 

[zapperzero]

? Nearly the opposite is true, as most fuels are close to being commodities especially in raw form, less so the as they are processed, modified, and blended to meet the regulations of particular local markets.

Fuels are rarely if ever blended. There's sweet crude, light crude, heavy crude, sour crude... quality differences which are reflected in the price and sometimes transferred to the end-products. Gasoline from made from Lybian oil has less sulfur than that from Saudi oil.

Refineries are generally optimized to deal with a certain type of oil. Re-equipping one is complicated and expensive.

Availability is another issue. Transport issues mean that crude from the Middle East does NOT have the same price all over the world. Some places, it may simply be unavailable. When you see talk of "oil prices" on CNN, they are generally speaking of the WTI index, which is just that, an index value from a local market, describing the price of a notional barrel of oil of a given known quality. WTI crude does not exist.

All physical deliveries are priced against a given index, with prices modified to reflect delivery date and quality of delivered product.

As for electricity, the constraints the grid imposes (huge transport losses, frequencies etc), plus the infinitesimal amounts of storage available, mean that price varies wildly across the "global market". In fact, there is no global electricity market, so it's not a commodity.

 

[zapperzero]

I speculate that most engineers would rather deal with a high temperature, low pressure system than a lower temperature, high pressure (153 atm for a light water PWR) system.

Reprocessing from the spent fuel of a U235 light water reactor produces Pu upon re-processing, not so for Th based LFTR (in significant amounts).

You speculate. You are also conveniently glossing over the corrosion issue.
What do you mean when you say a LFTR does not produce plutonium in significant amounts? It does. Separating it as it is being produced is trivial.

 

[mheslep]

You speculate. You are also conveniently glossing over the corrosion issue.

I only know my own preference as an engineer when given the choice: low pressure, high temp, even with high corrosiveness, over a high pressure steam system that must be contained in the event of failure.

What do you mean when you say a LFTR does not produce plutonium in significant amounts? It does.

The Pu production pathways are secondary and low probability in a Thorium reactor as opposed to primary in U235/U238. And yes, though any amount of Pu produced has to be addressed, in comparison to the load produced and stockpiled in dry casks daily by existing light water U235/U238 reactors, the amount of Pu produced per GW-day is not significant in Th reactors.

Th - U233 reactor
\mathrm{^{1}_{0}n}+{}_{\ 90}^{232}\mathrm{Th}\rightarrow {}_{\ 90}^{233} \mathrm{Th} \xrightarrow{\beta^-} {}_{\ 91}^{233}\mathrm{Pa} \xrightarrow{\beta^-} {}_{\ 92}^{233} \mathrm{U } +\ ^{1}_{0}n\ \longrightarrow \mathrm{fission}

U235/U238 Reactor
\mathrm{^{238}_{\ 92}U\ +\ ^{1}_{0}n\ \longrightarrow \ ^{239}_{\ 92}U\ \xrightarrow[23.5 \ min]{\beta^-} \ ^{239}_{\ 93}Np\ \xrightarrow[2.3565 \ d]{\beta^-} \ ^{239}_{\ 94}Pu}

The Pu path in a Th - U233 reactor is a rare event, requiring five neutron captures. Along the way fission is much more likely than capture (U233 90%,U235 85%) or the capture cross section is low (U236):

\mathrm{^{233}_{\ 92}U\ +\ ^{1}_{0}n\ \longrightarrow ^{234}_{\ 92}U\ +\ ^{1}_{0}n\ \longrightarrow ^{235}_{\ 92}U\ +\ ^{1}_{0}n\ \longrightarrow ^{236}_{\ 92}U\ +\ ^{1}_{0}n\ \longrightarrow \ ^{237}_{\ 93}NP\ +^{1}_{0}n\ \longrightarrow ^{238}_{\ 93}Np\ \xrightarrow{\beta^-} \ ^{238}_{\ 94}Pu}

Furthermore, unlike a solid fuel reactor, a liquid/molten reactor enables the possibility that the Np237 is continually removed, further shutting off the Pu pathway.

http://www-pub.iaea.org/mtcd/publications/pdf/te_1450_web.pdf

In 232Th–233U fuel cycle, much lesser quantity of plutonium and long-lived Minor Actinides (MA: Np,Am and Cm) are formed as compared to the 238U–239Pu fuel cycle, thereby minimizing toxicity and decay heat problems.

 

[zapperzero]

And yes, though any amount of Pu produced has to be addressed, in comparison to the load produced and stockpiled in dry casks daily by existing light water U235/U238 reactors, the amount of Pu produced per GW-day is not significant in Th reactors.The Pu path in a Th - U233 reactor is a rare event, requiring five neutron captures. Along the way fission is much more likely than capture (U233 90%,U235 85%) or the capture cross section is low (U236):

\mathrm{^{233}_{\ 92}U\ +\ ^{1}_{0}n\ \longrightarrow ^{234}_{\ 92}U\ +\ ^{1}_{0}n\ \longrightarrow ^{235}_{\ 92}U\ +\ ^{1}_{0}n\ \longrightarrow ^{236}_{\ 92}U\ +\ ^{1}_{0}n\ \longrightarrow \ ^{237}_{\ 93}NP\ +^{1}_{0}n\ \longrightarrow ^{238}_{\ 93}Np\ \xrightarrow{\beta^-} \ ^{238}_{\ 94}Pu}

Furthermore, unlike a solid fuel reactor, a liquid/molten reactor enables the possibility that the Np237 is continually removed, further shutting off the Pu pathway.

http://www-pub.iaea.org/mtcd/publications/pdf/te_1450_web.pdf

Citation right back atcha.

http://www.energystorm.us/Management_Of_Super_grade_Plutonium_In_Spent_Nuclear_Fuel-r49699.html

Says there plutonium is NOT an insignificant concern. Incidentally, the fuel-blanket design of EBR-II is the one the Indians are aiming for. I wonder why? No, actually I don't.

Don't want supergrade Plutonium? Well, I guess you could just separate U-235, make stupid boring simple A-bombs and call it a day. From what I can tell from your fancy equations, it self-accumulates in the fuel in far greater quantities than U-236, while U-234 to U-235 is a relatively high-probability event (100 barns thermal, 700 barns full-spectrum so again it matters a lot what reactor design you use).

 

[mheslep]

Citation right back atcha.

http://www.energystorm.us/Management_Of_Super_grade_Plutonium_In_Spent_Nuclear_Fuel-r49699.html

Says there plutonium is NOT an insignificant concern. Incidentally, the fuel-blanket design of EBR-II is the one the Indians are aiming for. I wonder why? No, actually I don't.

At the moment I'm only interested in the discussion of the month which began https://www.physicsforums.com/showpost.php?p=3294391&postcount=335": thorium based thermal reactors, and for which I've shown above plutonium is not significantly produced. The EBR mentioned in your reference is a highly enriched uranium fast spectrum breeder reactor; of course it produces plutonium.

Don't want supergrade Plutonium? Well, I guess you could just separate U-235, make stupid boring simple A-bombs and call it a day. From what I can tell from your fancy equations, it self-accumulates in the fuel in far greater quantities than U-236, while U-234 to U-235 is a relatively high-probability event (100 barns thermal, 700 barns full-spectrum so again it matters a lot what reactor design you use).

No, U-235 doesn't accumulate, in a reactor it primarily fissions, or decays, or becomes U236. And no 235 can not be chemically separated from the four other isotopes of Uranium. U233 is the primary fission fuel for this kind of reactor, and theoretically it could be used to make a weapon, though it appears extraordinarily difficult to do because of the gamma emissions from the inevitable U232 impurities and its decay chain.

 

[zapperzero]

Ok, thorium-based. Which design are we talking about, exactly? I'd hate to make the same mistake twice.

Your argument re chemical separation is a straw man. I never said it's possible with chemicals, just possible. Of course isotope separation is hard, but it's no harder or easier than it is for uranium obtained from other sources.

Now, for the accumulation. Take a thorium-based design of your choice. How much U-235 is there, per unit mass, in the fuel, after six months of operation? How much Pu-238?

 

[mheslep]

Ok, thorium-based. Which design are we talking about, exactly? I'd hate to make the same mistake twice.

Well some modern variant of the original Thorium molten salt reactor as built at Oak Ridge
http://en.wikipedia.org/wiki/Molten...tional_Laboratory_Molten_Salt_Breeder_Reactor

Your argument re chemical separation is a straw man. I never said it's possible with chemicals, just possible. Of course isotope separation is hard, but it's no harder or easier than it is for uranium obtained from other sources.

Now, for the accumulation. Take a thorium-based design of your choice. How much U-235 is there, per unit mass, in the fuel, after six months of operation? How much Pu-238?

Interesting question, let me crunch that one ...

 

[chrisbaird]

I don't think that's sappy at all. But, in the time it would take to design, license, and build a few nukers, (Add extra time to deal with the courts while every anti-nuke protester in the country trys to stop construction.) the photovoltaic industry could provide a better solution. As demand grows the technology improves and the cost comes down. Lots of good paying jobs are created. There's really no reason why there couldn't be 2 or 3 kilowatts of PV cells on 2 million roofs through the sun belt in just 2 years.
Just a thought.

If you do the math, solar energy is not viable on the large-scale. No matter how amazing your photovoltaics are, there is simply not enough solar energy incident on the surface of the US to run the country without bull-dozing large swaths of land. I think its crazy how some environmentalists love solar, but if it were to be implemented on a large scale would require the destruction of large amounts of wilderness.

 

[mheslep]

If you do the math, solar energy is not viable on the large-scale. No matter how amazing your photovoltaics are, there is simply not enough solar energy incident on the surface of the US to run the country without bull-dozing large swaths of land. I think its crazy how some environmentalists love solar, but if it were to be implemented on a large scale would require the destruction of large amounts of wilderness.

That's misinformation. Current technology 20% efficient PV could capture enough sunlight to power the entire US electrical load (~1000GWe capacity) with an PV area of ~30,000 sq km (100mi by 100mi). http://www.miller-mccune.com/business-economics/leasing-america-s-rooftops-for-solar-energy-3987/" That portion at least requires bull-dozing nothing at all.

The problem with solar PV power lies in the distribution of that power, how to store it for use when the sun's not available, and, most of all, cost in comparison to other sources. The problems do not include a lack of solar energy incident on US geography. Edit: See for example
http://www.landartgenerator.org/blagi/wp-content/uploads/2009/08/AreaRequired1000.jpg

 

[Ivan Seeking]

That's misinformation. Current technology 20% efficient PV could capture enough sunlight to power the entire US (~1000GWe capacity) with an PV area of ~30,000 sq km (100mi by 100mi). The problem lies in distribution of that power, how to store it for use when the sun's not available, and, most of all, cost in comparison to other sources. The problems do not include a lack of solar energy incident on US geography.

Given that it tends to be less centralized, it seems that distribution is less a problem for solar than nuclear power.

 

[zapperzero]

Well some modern variant of the original Thorium molten salt reactor as built at Oak Ridge
http://en.wikipedia.org/wiki/Molten...tional_Laboratory_Molten_Salt_Breeder_Reactor

An interesting read. Would your modern variant also include a neutron-generating core of U-235? Again, what design are we talking about, here?

I liked the references best. Here's one:
http://www.nap.edu/catalog.php?record_id=5538
It's a study on disposal issues. One of the issues discussed is that UF6 may have outgassed from the cold salts mixture. Another is a chemical method for the removal of Plutonium.

 

[mheslep]

An interesting read. Would your modern variant also include a neutron-generating core of U-235? Again, what design are we talking about, here?...

Some kind of neutron source, perhaps a fissionable material like low enriched Uranium, is needed to start a Thorium reactor. The source starts the process of breeding Thorium into U233, but once started the source is soon burned up and no longer needed.

 

[Borek]

Some kind of neutron source, perhaps a fissionable material like low enriched Uranium, is needed to start a Thorium reactor. The source starts the process of breeding Thorium into U233, but once started the source is soon burned up and no longer needed.

Don't you need a neutron source to start uranium reactor as well? Or at least to start it in a reasonable time?

 

[Joe Neubarth]

Don't you need a neutron source to start uranium reactor as well? Or at least to start it in a reasonable time?

In tons of Uranium, there is always a neutron source.

 

[Astronuc]

Don't you need a neutron source to start uranium reactor as well? Or at least to start it in a reasonable time?

In a core of fresh fuel, as is the case in the first cycle, and usually in the second cycle, where the max burnup is low, yes one uses startup sources to provide sufficient neutrons to the detection systems.

In fresh or first cycles cores, there are primary neutron sources, e.g., PuBe, RaBe, AmBe or more commonly these days Cf(252)Be, that use (α,n) reactions, in which an alpha from Pu, Ra, Am or Cf fuses with the Be nucleus to form an excited C¹³, which then emits a neutron and becomes a C¹² nucleus.
http://en.wikipedia.org/wiki/Startup_neutron_source

The added benefit of Cm is spontaneous fission.

After at least 3 annual cycles, or 2 18-mo or 24-mo cycles, there is sufficient TU elements, or radioisotopes of Pu, Am, Cm to have sufficient spontaneous fissions to produce the necessary neutron activity to monitor the approach to criticality.

Otherwise there is a secondary source of neutrons (Sb-Be) which uses activation of Sb-123 to produce Sb-124, which decays to Te-124, and in the process a 1.7 MeV gamma is emitted which induces photoneutron emission. The secondary source produces neutrons during the second and third cycles of a young reactor, until there is sufficient TU inventory.

In tons of Uranium, there is always a neutron source.

A core of fresh U has very little neutron activity. So a neutron source is added.

One of the objectives is to ensure that a prompt criticality (or rather prompt supercriticality) will not occur.

 

[mheslep]

Don't you need a neutron source to start uranium reactor as well? Or at least to start it in a reasonable time?

I expect a neutron source such as described by Astronuc would also be required to 'ignite' the enriched uranium starter mix-in in a thorium reactor. The thorium reactor differs at startup from a uranium reactor in that it has no fissionable fuel at time zero, requiring a high neutron flux for some time to breed the sufficient thorium into fissionable U-233.

 

[zapperzero]

I expect a neutron source such as described by Astronuc would also be required to 'ignite' the enriched uranium starter mix-in in a thorium reactor. The thorium reactor differs at startup from a uranium reactor in that it has no fissionable fuel at time zero, requiring a dense neutron flux for some time to breed the sufficient thorium into fissionable U-233.

The Oak Ridge experiment was run to test (among other things) the feasibility of a mixed U-Pu core as a neutron source for a thorium breeder reactor. I should add, perhaps, that this means the actual breeding and separation process was never tested there.

 

[zapperzero]

Indian documentary about their thorium AHWR experiment. It is being run on a mix of PuO2/ThO2 and UO2/ThO2 elements.

 

[mheslep]

In a core of fresh fuel, as is the case in the first cycle, and usually in the second cycle, where the max burnup is low, yes one uses startup sources to provide sufficient neutrons to the detection systems.

In fresh or first cycles cores, there are primary neutron sources, e.g., PuBe, RaBe, AmBe or more commonly these days Cf(252)Be, that use (α,n) reactions, in which an alpha from Pu, Ra, Am or Cf fuses with the Be nucleus to form an excited C¹³, which then emits a neutron and becomes a C¹² nucleus.
http://en.wikipedia.org/wiki/Startup_neutron_source

The added benefit of Cm is spontaneous fission.

After at least 3 annual cycles, or 2 18-mo or 24-mo cycles, there is sufficient TU elements, or radioisotopes of Pu, Am, Cm to have sufficient spontaneous fissions to produce the necessary neutron activity to monitor the approach to criticality.

Otherwise there is a secondary source of neutrons (Sb-Be) which uses activation of Sb-123 to produce Sb-124, which decays to Te-124, and in the process a 1.7 MeV gamma is emitted which induces photoneutron emission. The secondary source produces neutrons during the second and third cycles of a young reactor, until there is sufficient TU inventory.

Astronuc - I'm curious as to why neutron generators using fusion of D or T targets via acceleration are not considered for fission reactor startup. It seems there would be a large advantage in being able to control or stop neutron generation during installation in the reactor by the flip of switch (the accelerator voltage), likewise with transportation issues.
http://en.wikipedia.org/wiki/Neutron_generator

 

[zapperzero]

Astronuc - I'm curious as to why neutron generators using fusion of D or T targets via acceleration are not considered for fission reactor startup. It seems there would be a large advantage in being able to control or stop neutron generation during installation in the reactor by the flip of switch (the accelerator voltage), likewise with transportation issues.
http://en.wikipedia.org/wiki/Neutron_generator

Where would you put your accelerator? And then? Wave it around like a flashlight?
What would you do with it after the chain reaction starts?