Peter Lux

Energy Density of Uranium

I am writing this because it is mentioned in many children’s science books and on the Internet. This is the fact that one kilogram of Uranium can produce millions of times more energy than something like coal (83,140,000 MJ/Kg for Uranium 235 compared with 24MJ/Kg for coal). However this is very misleading.

I will be comparing it to fossil fuels but this does not mean that I am in favour of fossil fuel plants but it is a good comparison to get things in perspective.

Too Much Power

For building a nuclear bomb the enormous amounts of energy are great – you can produce a very big explosion and kill millions of people. However, this is not good in a power plant. You need to ‘burn’ the Uranium a lot slower – in fact some coal and gas power plants produce a lot more power. It is also necessary to be able to remove the heat generated so that you do not get excessive temperatures. There is nothing special about nuclear power – it is just another way of boiling water.

Batch Process

Nuclear power generation is a batch process. With fossil fuel plants the fuel is feed in a bit at a time to be burnt. With nuclear several years supply of fuel is present in the reactor at any one time and is slowly ‘burnt’. This constrains the operating temperature that the plant can run at since too high a temperature will damage the fuel rods. The nuclear reaction isÂ  inherently a batch process since you need a critical mass of fuel to sustain the nuclear reaction. However, the critical mass is still enough to cause a massive nuclear explosion if not controlled carefully.

TheÂ  operating temperature for a gas plant (over 900ÂºC) is much higher than that of a nuclear plant (320ÂºC) which means that a gas plant can have a much greater thermal efficiency2.

Amount of Fuel

What is important is that you need less fuel to produce the same amount of power. However, just taking the energy density of Uranium 235 is very misleading.

The fuel used in a nuclear power plant is only slightly enriched with Uranium 235 (let us say 4%). We could do a calculation on how much energy per kilogram this would produce but there are other factors – e.g. some of the Uranium 238 is converted to plutonium which is then fissioned. So let us take the expected burnup rate for the proposed new reactors – 60 GWdays/ Tonne, which is 60MWdays/Kg or 5,184,000MJ/Kg. This is already a lot lower than the 83,140,000 MJ/Kg which is often quoted.

Now we have to take into account that the Uranium has been enriched from 0.711% U-235 to 4% U-235. So we actually need 7.31Kg of natural uranium to produce this3. So the energy density of natural uranium is 83,140,000/7.31 = 709,166 MJ/Kg.

But we also have to take into account the amount of energy needed for fuel fabrication. Figures vary considerably but let us take 2000MJ/Kg4.

There is also the energy needed to enrich the uranium to 4%. This takes about 7.69 SWU with each SWU requiring 187KWh/SWU4 which is 5177MJ/Kg.

Taking these into account we now have an energy density of 701,988 MJ/Kg.

Unlike coal uranium has to be extracted from an ore. The quality of the ores varies but let us say it is 0.2% which is typical. Therefore the energy density of the ore isÂ 701,988 x 0.2% = 1404 MJ/Kg.

Although this is still a very large amount it is 60,000 times less than the 83,140,000 MJ/Kg we started with. With lower burnup and lower quality ore (say 40GWday/Tonne and 0.02%) then we are down an energy density of 93 MJ/Kg for uranium ore.

The last factor, which is true of any thermal plant, is that only a portion of the thermal energy can be converted into electricity – about 33% for nuclear, 40% for coal and over 55% for modern gas plants. However, the efficiency of energy use can be massively improved by using Combined Heat and Power (CHP)

This is not a full energy analysis. It does not take into account the energy needed to mine the uranium ore, construct the nuclear power plant etc. However, I hope it does put the arguments about the massive energy density of Uranium compared with fossil fuels into perspective.

My workings can be found in this spread sheet

1 Energy Density, Wikipedia (http://en.wikipedia.org/wiki/Energy_density)

2 There are lots of discussion about the ‘Carnot Cycle’ on the web but Feynman gives a very general derivation of the efficiency rather than just for an ideal gas. R Feynman Lectures in Physics Chapter 44 (http://www.feynmanlectures.caltech.edu/I_44.html)

3 See the table at the end of mu post on Uranium Enrichment (http://www.plux.co.uk/uranium-enrichment-formula/)

4 Lenzen, M. (2008) Life cycle energy and greenhouse gas emissions of nuclear
energy: A review. Energy Conversion and Management 49, 2178-2199.(http://www.isa.org.usyd.edu.au/publications/documents/ISA_Nuclear_Report.pdf)

20 Responses to “Energy Density of Uranium”

• This is great info, I am doing some research for my website here http://www.fire2fusion.com/gas-energy/natural-gas-energy-density.html

Thanks

• roberto kersevan says:

@pete

” Many people thought that having a nuclear reactor that contains over 5000T of liquid sodium which burns in air and reacts explosively with water was a bad idea.”

Well, “many people” does not mean much!…
Just to stick with one example to the energy sector…”many people”, for instance, think that having a LNG terminal which deals with billions of cubic meters of explosive gases in a metropolitan area is a bad idea… but in spite of that you can see that one of the most densely populated countries on the planet…

… has tens of such “dangerous” terminals… and at least 3 of them are in the Tokyo bay, literally few hundred meters away from the city’s buildings… just look at Google Earth or this document:

Fig.1.

If you scare people by saying silly things like “plutonium is the most dangerous element/substance on earth” clearly the average un-trained person will believe you…. but the reality is much, much different. Plutonium in a reactor is never in a single or pure isotopic fraction, it is a mix which cannot explode, it is not volatile, it has nowhere to go. Small fires due to the contact of minutes amounts of water/humidity with sodium did happen at Superphenix and other FBR-Na, but none has been serious. Suffice to say that all of the liquid Na of Superphenix has already been extracted by the reactors, inerted, and mixed with a special concrete… and all this will be disposed of by burying the bricks thus obtained, EDF is in advance with the scheduled time for decommissioning the reactor, and the foreseen budget has been more or less respected so far.

The “many people” in the case of Superphenix were politicians, with no knowledge whatsoever in terms of science and technology… in fact during the parliamentary discussions the few elected representatives who spoke in favor of the project were the scientifically literate ones. To me, as a scientist, their voice counts much more than that of the others… anybody who thinks differently next time he/she gets sick should see a plumber instead of an MD… 🙂

Cheers.

• Pete says:

If you scare people by saying silly things like â€œplutonium is the most dangerous element/substance on earthâ€? clearly the average un-trained person will believe you
Just to note that I have not said this anywhere in my blog. Neither have I supported storing large amounts of LNG near populated areas and as I pointed out before I do not support burning biomass at Drax.

• Pete says:

P.S. I could argue that plutonium is the most dangerous element on earth. However, I see as much point in that as arguing which is the prettiest flower in the world.

• Robertok06 says:

Clearly the ‘you’ in my message was not you, Peter… don’t be silly…
… and coming to the toxicity of Pu… make my day, show me a reliable document proving what you claim.

• Pete says:

“Clearly the â€˜youâ€™ in my message was not you”!!!

• Robertok06 says:

@pete

‘â€œClearly the â€˜youâ€™ in my message was not youâ€?!!!’

Exactly, it was not YOU, since, as you have confirmed above, YOU had not said those things about Pu!
… should have used an impersonal ‘if one says…’…

• roberto kersevan says:

@peter lux

“. Why are you trying to attack my argument about the energy density of Uranium by bringing up Drax? I do not written anything supporting burning biomass at Drax in this post or anywhere else on my site â€“ because I do not support it. Again you are trying to misrepresent what I am saying.”

Oh please!… don’t play this!… my comment on Drax was and still is perfectly relevant, because it responds to your statement…

“The way in which we generate energy is changing and there is no place for current nuclear fission reactors.”

… last sentence of your message to which I was replying!… the change in the way “we” (you in the UK in my interpretation) are going to generate energy.

R.

• roberto kersevan says:

@peter lux:

I had this one written before my last one… just to straighten up the record:

You wrote:

“Reprocessing was not originally developed for â€˜once throughâ€™ reactors but for fast breeder reactors (FBRs). However, they have been spectacularly unsuccessful â€“ Dounray in Scotland, Phenix and Super Phenix in France. It was not just the cost but also overcoming the technical difficulties. ”

Actually, I am not too familiar with Dounray’s fast breeder reactor history and performance… but I DO know the history and performance of both Phenix and Superphenix, and their record is, contrary to popular anti-nuclear galore that you seem to agree with, they have been very successful project, leading to big advances in the knowledge of the operation of FBRs and, complemented by many studies about operational emergency/accident scenarios… the French CEA site is full of nice papers and presentations, you just need to understand a bit French, and leave aside popular galore for once.

A quick comprehensive example?

http://www.cea.fr/energie/les-reacteurs-nucleaires-a-caloporteur-sodium/historique-et-bilan-de-fonctionnement-des-rnr-na

Phenix, which you qualify as a “spectacularly unsuccessful” has generated in 35 years, 26 TWh of electricity. Before you jump once again to the wrong conclusions, the low capacity factor has been mainly caused by ADMINISTRATIVE issues which have forced limits on the time the reactor could run. All this is well documented, of course.

Superphenix has also been VERY successful!… exactly the contrary of what you claim!… and the fiasco associated with it was only political, as it was stopped by a litigation lawyer who blackmailed then prime minister Jospin to either cancel the project or have its government fall… once again the “democratic” greens have applied the only measure they are good at… blackmailing… actually, talking about Superphenix, some “greens” even got to the point of shooting a few anti-tank RPGs at it, during its construction… is that also a fiasco attributable to the nuclear industry?

R.

• Pete says:

A more comprehensive review of FBR are given here –
http://fissilematerials.org/library/rr08.pdf
Let us just look at Superphenix. There was a lot of opposition to the FBR from the beginning. Many people thought that having a nuclear reactor that contains over 5000T of liquid sodium which burns in air and reacts explosively with water was a bad idea. On top of this maintenance is rather difficult since you have machinery embedded in sodium metal – you can’t wash it out with water. Also it is difficult to ensure that you always have a negative void coefficient.
The administrative delays were not arbitary but due to safety concerns and worries about the economics of such reactors. The reactor worked for 17 months at about 15% capacity factor. It then broke down and took 10 months to repair. After 13months of debate the nuclear lobby won and it was restarted. It worked for 15 months – at an even lower capacity factor. Then it broke down again and took 8 months to repair. There was then another debate and a public enquiry into the safety and economics. Again the nuclear lobby won and it was allowed to start operating again. It worked for 5 months and then broke down again and took seven months to repair. Amazingly it was then allowed to restart. Again the capacity factor was very low – 7.9%. Eventually it was shut down at the end of 1996.

Pete

• roberto kersevan says:

@pete

Fiction…

” Amazingly it was then allowed to restart. Again the capacity factor was very low â€“ 7.9%. Eventually it was shut down at the end of 1996.”

… and reality:

Electricity production during 1996: 3.45 TWh, i.e. more than 30% capacity factor…. clearly, if finally when it seemed to work politically opportunistic choices led by an idelogically biased group decided to shut it down, it is not the fault of the terribly dangerous “nuclear lobby”… which seems to scare you so much.

” There was then another debate and a public enquiry into the safety and economics.”

you have it completely wrong!… there was only politica debate, nothing else.

Here are the transcripts (in French) of the discussions at the French parliament, on this issue:

… page 55 “Les modalitÃ©s de la dÃ©cision prÃ©cisÃ©es a posteriori”… or how the decisions (to shut down the reactor) were taken a posteriori…

The economics of the project was damaged a lot by the fact that the fuel core installed at the moment it was stopped was more than 50% valid (could have produced a lot more energy), and there was already a complete second fuel load ready (worth 24 TWh, if I remember correctly).

Add to that the fact that the two international partners in the project had rightfully to be refunded (billions of today’s Euros)… so, please, don’t even talk about economics of Superphenix, OK?

There is a rather complete analysis of the costs of all of the nuclear industry in France by the Cour des Comptes, it is even translated in German and English…

page 46:

“SuperphÃ©nix cost â‚¬12 billion2010 over the 1974-1997 period in construction and operation, but its change of “status” from an industrial to a research facility, has made it a special case.
Launched in 1974, this reactor with an industrial output of 1 200 MWe was built at Creys-Malville by NERSA, a dedicated company majority-owned by EDF, with Italian and German partners and without direct involvement by the CEA beyond preliminary studies.
Connected to the grid in January 1986, it was not intended to be used for research purposes but for producing electricity.
However, it operated for only ten months until 1994, until being redirected as a sub-generation research tool at an annual cost of 100 million adjusted Francs, fully borne by EDF,
before being closed in 1997.

Excluding CEA and EDF preliminary studies and also dismantling costs, the Cour des Comptes estimated in its 1996 public report the full cost of SuperphÃ©nix at 60 billion Francs1994, or â‚¬12 billion2010, including â‚¬2.5 billion2010 in financial charges. ”

So… 12 billions, having been stopped by decree several DECADES before it’s due time… should ask the greens to foot the bill! 😉

Anyway, the success of Superphenix resides in the very large amount of knowledge about FBRs that it has generated, and which will be used in the future.

Page 50 or so…

… the real reason the reactor was stopped… political agreement between Lionel Jospin’s Socialist Party and the Greens. That’s history, full stop.

R.

• roberto kersevan says:

… sorry… the last excerpt is taken from here, official site of the french parliament:

• roberto kersevan says:

@peter lux
You are right, these messages are getting too long… in addition to that during the weekend I’ve looked/browsed around your other blog pages and I have discovered that you are someone who’s interested to spew fake information about nuclear technology… anybody who takes for serious and cites the works of people like Chris Busby and Ian Fairlie must clearly have an ideological agenda in front of any real scientific/technological interest. Too bad, indeed.

I should have understood that since the beginning, my fault… just the fact that this blog page, on the energy density of uranium, started with an unsubstantiated “many childrenâ€™s science books and on the Internet”… while it is sufficient to go to the web page of those who represent the nuclear industry, http://www.world-nuclear.org/Nuclear-Basics/ , to find what they have to say on this:

“Did you know…? A single uranium fuel pellet contains as much energy as 480 cubic metres of natural gas, 807 kilos of coal or 149 gallons of oil.”

It is clear that you prefer coal and its deadly emissions to nuclear and its extremely low impact on human health (large accidents included), so good luck with your PV system in sunny Lowestoft, too bad it will never produce any single Wh between sunset and sunrise, 365d/y, and will produce less than 15% of the annual total during the 4 long winter months of November through February…. but in order to beat the nuclear monster a small sacrifice is acceptable, right?

To conclude, your last sentence is:

“The way in which we generate energy is changing and there is no place for current nuclear fission reactors.”

…I agree with you concerning the UK: you clearly are moving from emission-free and cheap nuclear towards trimming down vast swaths of virgin forests in southern USA to burn them in Drax power station!… congratulations to you! 🙂

“Drax will be burning pellets made from up to 15.8 million tonnes of biomass â€“ nearly all of it wood â€“ every year. Since the UKâ€™s total wood production is only 10 million tonnes a year, virtually all of the wood Drax needs will have to be imported.”

It’s the new episode of “medieval ages redux”, where the highest energy density fuel is replaced by… wood!… i.e. the lowest energy density one… what more could one say?

Cheers, and have a nice day.

R.

• Pete says:

” I have discovered that you are someone whoâ€™s interested to spew fake information about nuclear technologyâ€¦ anybody who takes for serious and cites the works of people like Chris Busby and Ian Fairlie”
I have referenced one paper by Ian Fairlie and an article written by Chris Busby. If you have any disagreement with what they state in the paper/article please state what it is – it is not good enough to just say that they are ‘anti-nuclear’. Even worse you seem to be attacking the validity of what I say because I referenced them!
I also mention a report by Chris Busby in another post – I do not reference its results or findings – in fact I was going to write a post which was highly critical of that report but never got around to it. I do not necessarily agree with everything that Chris Busby or Ian Fairlie write. You will also notice that I reference the IAEA, NIA, WNA many times but similarly I do not agree with everything that they say.
started with an unsubstantiated â€œmany childrenâ€™s science books and on the Internet”
To be honest I am not going to substantiate this people can do this for themselves. Your point is irrelevant since I did not say that the World Nuclear Association made this misleading claim.
This post was about how the energy density of Uranium is misleading. Discussion about the viability of photovoltaics and biofuels here is irrelevant. Why are you trying to attack my argument about the energy density of Uranium by bringing up Drax? I do not written anything supporting burning biomass at Drax in this post or anywhere else on my site – because I do not support it. Again you are trying to misrepresent what I am saying.
If you are going to make any future comment then please make keep it relevant and fact based and not personal attacks on myself or anyone else.

• roberto kersevan says:

“However, I hope it does put the arguments about the massive energy density of Uranium compared with fossil fuels into perspective.”

It does put things in a different perspective, but unfortunately it a somewhat wrong perspective.

You forgot to take into account several factors: not only U generates energy during fission, as the generated Pu isotopes contribute to the energy balance; the spent uranium at the end of the cycle in modern reactors still has more than 90% of the original energy density, just to mention a few.
Not the same could be said of coal ashes, or natural gas fumes, after combustion in a fossil fuel plant. There’s no more energy to take out of them…. other than mining for the uranium in coal ashes, of course!

You have also probably overestimated the amount of energy necessary for the complete fuel cycle. You can do a better estimates by looking at an “EPD”, Enrivonmental Product Declaration, for 1 kWh of electricity produced by nuclear. Such a document can be easily found by googling “EPD Vattenfall nuclear”.

Also: U can be fissioned as natural uranium in CANDU-type reactors, so no need to enrich it at (although I’m aware that the heavy-water needed for this type of reactors is an energy-intensive element).

U, and all the actinides etc… could be fissioned in a much safer way using accelerator-driven nuclear transmutation, as already demonstrated in a recent past. It is not done yet only because of political decisions, it could be done tomorrow if chosen so (see testbed experiment on Energy Amplifier at CERN 20 years ago or so). This would also help solving/alleviating the problem of nuclear waste repositories.

Finally, each kWh of electricity produced in a light water reactor generates a total of 0.3milligrams of high-level waste, with no greenhouse gases during production and a total of few grams of CO2/kWh for the upstream and downstream part of the fuel cycle (see EPD data mentioned above)… while each kWh of coal generates several kilos of CO2, not to mention the vast amount of particulates, nitrous oxide, sulfur oxide, heavy metals, ozone precursors, etc…

Cheers,

Roberto Kersevan

Disclaimer: in no way the opinions expressed here by the writer reflect the opinions or position of his employer in matters of nuclear energy.

• Pete says:

Dear Roberto
You obviously have not read my post. You state that:

“not only U generates energy during fission, as the generated Pu isotopes contribute to the energy balance”

However if you had bothered to read my post I clearly state:

“We could do a calculation on how much energy per kilogram this would produce but there are other factors â€“ e.g. some of the Uranium 238 is converted to plutonium which is then fissioned. So let us take the expected burnup rate for the proposed new reactors â€“ 60 GWdays/ Tonne, which is 60MWdays/Kg or 5,184,000MJ/Kg”

Not only does this take into account Pu burnup but also the decay heat production which is small but not insignificant. Also note that I am using a 60MWdays/Kg which is that specified for new reactors such as the EPR and not currently operating nuclear power stations that operate at a lower burnup.
This means that 94-96% of the original energy density remains in the ‘spent’ fuel. With only 35% of that energy being turned into electricity this gives an efficiency of 2.1-1.4% efficiency in turning the energy in the Uranium into electricity – I shall come back to this point later.
You say that:

“You have also probably overestimated the amount of energy necessary for the complete fuel cycle”

I probably didn’t â€“ I have referenced the paper where I get this estimate from. Note that this is from a proper scientific study and not a ‘statement’ by a nuclear power company. If there are problems with their data or analysis I would like to see it. I can not however comment on the Vattenfall arrive at their figure since, as I have said this is a ‘statement’ and not a proper scientific study.

“U can be fissioned as natural uranium in CANDU-type reactors”

This is true but the burnup is a lot lower and so CANDU reactors are less efficient. I looked at what I believe to be the most efficient modern designsâ€“ although none have actually been built successfully yet.

“U, and all the actinides etcâ€¦ could be fissioned in a much safer way using accelerator-driven nuclear transmutation,”

Any nuclear power company could put in a generic design assessment for an Accelerator driven subcritical reactor. The decision is not a political one but the fact that reactors can not be done economically ‘tomorrow’ or even next year or twenty years time if at all. However, I do not see much point in arguing against such ‘pie in the sky’ ideas.
If such ‘waste free’ nuclear fission technology does become possible in the future then we have already wasted that valuable energy source. If such technologies are available in the future then utilising highly radioactive spent fuel â€“ which as you say still has 90% of the theoretically available energy is even further into the future. The ‘best approach’ to spent fuel that the UK government experts can come up with is to bury it â€“ some how at some place and at some time.
New nuclear is not replacing coal â€“ in fact it is replacing very little at the moment â€“ so why are you making that comparison. Are we going to spend another 50 years on a expensive failed technology or get on with decarbonising our energy supply with energy efficiency and renewables.

• roberto kersevan says:

You obviously have not read my post. You state that:
â€œnot only U generates energy during fission, as the generated Pu isotopes contribute to the energy balanceâ€?
However if you had bothered to read my post I clearly state:
———–

Hello:

I did bother to read your post, I simply did not word properly my reply on this point, you are right. I should have referred not to the plutonium generated and burned during the operation of the reactors, which you have done it, but rather the plutonium which is extracted and re-utilized from the spent fuel, the way the French do in La Hague. Clearer now?

“This means that 94-96% of the original energy density remains in the â€˜spentâ€™ fuel. With only 35% of that energy being turned into electricity this gives an efficiency of 2.1-1.4% efficiency in turning the energy in the Uranium into electricity â€“ I shall come back to this point later.”
That’s exactlky what I’ve said!â€¦ you discount the fact that the very last majority of the energy available in the original U batch is not usedâ€¦ but this does NOT, in no way, means that it should be discarded from the point of view of the energy balance!â€¦ if you go at a store and buy a 10 Euro item, pay with 50 Euro bill, and don’t bother to take the 40 Euro cash back does not mean that your item has cost 50 Eurosâ€¦ it is that simple.
The present cost, and the politics/ideology of today’s world, calls for the”once through” cycle, which you call for belowâ€¦ but that has been done by the pajority of nuclear countries only because it is ECONOMICALLY profitable to do so, the day U will cost 400 Euro/kg instead of the 60 it costs now (or wahtever the real price now might be) it will then become easier to separate the different isotopes and re-use them, it will even become profitable to re-use the immense amount (energy-wise) of depleted uranium stored as UF6.

“You say that:
â€œYou have also probably overestimated the amount of energy necessary for the complete fuel cycleâ€?
I probably didnâ€™t â€“ I have referenced the paper where I get this estimate from. Note that this is from a proper scientific study and not a â€˜statementâ€™ by a nuclear power coampany.”
1) The Lenzen study is siply a META-ANALYSIS of all previous studies, not a study by itself! In addition to that it is about, I copy and paste hereâ€¦ “The fuel cycle and reactor technology options chosen are described in detail and justified in the Australian context.”â€¦ hte Australian contextâ€¦ far from the context of , say, France, the USA or Sweden.
2) The Lenzen review cites even NON-scientific studies, like the unrealistic and ridiculous anti-nuclear propaganda of the duo Smith-van Leeuwen.
3) The “statement” from a company, as you call it is a DOCUMENT written following an international ISO standard accepted by all modern industrial conglomeratesâ€¦ so you are saying that when BMW or any other auto-maker makes the “statement” that their new engine model develops 150 HP, as measured according to another ISO standard, we should not believe them, it’s a fake juzst because it is not published in Nature or Science?C’mon!â€¦ before writing such a questionable objection you should have bothered to look at what an Environmental Product Declaration is!â€¦ you can find them for wind, hydro, gas, coal, etcâ€¦ most of them on the same Vattenfall web-siteâ€¦ also those are just “statements” according to you?

“If there are problems with their data or analysis I would like to see it. I can not however comment on the Vattenfall arrive at their figure since, as I have said this is a â€˜statementâ€™ and not a proper scientific study.”
It is a document conceived and based on an internationally accepted industrial standard!â€¦ c’mon! get over it!â€¦ They use the similar documents made by, for instance, the Namibian uranium mine from which most of the swedish uranium comesâ€¦ that also certified by an EPD document.

â€œU can be fissioned as natural uranium in CANDU-type reactorsâ€?
This is true but the burnup is a lot lower and so CANDU reactors are less efficient. I looked at what I believe to be the most efficient modern designsâ€“ although none have actually been built successfully yet.”
Who cares?â€¦ the point was only meant to say that the whole enrichment process is not mandatory, thorium reactors do not need enrichment either, and there is approximately 2x as much Th than U on the earth’s crust. Th-based reactor have been built decades ago, by the way.

“â€œU, and all the actinides etcâ€¦ could be fissioned in a much safer way using accelerator-driven nuclear transmutation,â€?
Any nuclear power company could put in a generic design assessment for an Accelerator driven subcritical reactor. The decision is not a political one but the fact that reactors can not be done economically â€˜tomorrowâ€™ or even next year or twenty years time if at all. However, I do not see much point in arguing against such â€˜pie in the skyâ€™ ideas.””

Are you kidding me or what? I happen to work and have worked for almost 30 years now in the two fields which could do exactly what you claim can’t be done!â€¦ the energy-amplifier concept has been validated at CERN by C. Rubbia’s team 20 years agoâ€¦ if nobody has ever bothered to try it is because there is no POLITICAL will, nothing more. The MYRRHA project in Belgium has been dragging its feet on a similar project just because the geniuses in the EU office deputed to fund research have managed to cut to the bone the money necessary to build itâ€¦ not because of technical issues, a large cyclotron (or linac) and some Pb-Bi euthectic (used by decades on nuclear submarines) are nothing new, it’s only the politics (and the ideology behind it) that prevents it from being done. By the way, without going into the details, I know exactly what I’m talking about, it’s not an uninformed opinion, let me be clear.

“If such â€˜waste freeâ€™ nuclear fission technology does become possible in the future then we have already wasted that valuable energy source.”
Pure nonsense.
1) there is no “waste freee” form of energy, it is simply that nuclear has the lowest amount of waste and impact on the environment
2) according to your reasoning, why do you keep on installing tens of GWp of useless photovoltaics even if their photon-to-current conversion is ridiculously lowâ€¦ why don’t you wait for the 50% efficiency ones to become mass-produced instead of keeping on producing and installing and using for the next 20+ years those of today which have a mere 14-15% efficiency?
See?â€¦ it’s easy to use bogus argument against your favorite technology. Same for wind.

“If such technologies are available in the future then utilising highly radioactive spent fuel â€“ which as you say still has 90% of the theoretically available energy is even further into the future. The â€˜best approachâ€™ to spent fuel that the UK government experts can come up with is to bury it â€“ some how at some place and at some time.”
Wellâ€¦ the “best experts” in the UK could not find a better solution than delivering in the hands of EDF their nuclear futureâ€¦ the “best experts” in the UK have employed massively the graphite-moderated, gas-cooled design, which is certainly one of the worst configurations possibleâ€¦ while the “not-so-best-experts” across the Channel have instead used and profitably run since 30+ years 58 reactors which are basically the same design, light water PWRs.
I suggest you choose some “better” experts to rely on your future energy choices in the UK (if you do live in the UK, as I’ve guessed)â€¦ although when I browse the pages of DECC I must admit that I can’t see the light at the end or your energy/electricity-tunnelâ€¦ you are putting all your eggs in the wind basket which is clearly, already now, the wrong one. The last coup de foudre of the british green intellighentsia isâ€¦ photovoltaicsâ€¦ in sunny UK???? And then you tell me of pies in the sky? Less than 10% capacity factor???

“New nuclear is not replacing coal â€“ in fact it is replacing very little at the moment â€“ so why are you making that comparison.”
Of course it is not!â€¦ the choice now is on heavily, scandalously SUBSIDIZED reneawable source, especially the real pie in the sky PV: 12 billion Euro/year in DE, 6.7 billion Euro/year in ITA, a couple Billion pounds/year in the UKâ€¦ to produce basically NOTHINGâ€¦ only to fatten the check account of savvy investors.
New nuclear IN THE WEST is clearly not replacing muchâ€¦ but neither are new wind or new photovoltaicsâ€¦ judging by THE DATA on Fraunhofer Institut, almost 80 GW of combined wind and PV in Germany produce a tiny fraction of the electricity consumed by Germanyâ€¦ the vast majority is produced by lignite and coalâ€¦ and after the geniuses of the Energiewende decided to stop 8 perfectly functioning reactors in mainland Germany on the pretense that they were unsafe for tsunamisâ€¦ !!!â€¦ the GHG emissions from the electricity sector in Germany have gone UP, in spite of the installation, since March 2011, of more than 20 GW of wind and PV. Better proof based on DATA I couldn’t find.

“Are we going to spend another 50 years on a expensive failed technology or get on with decarbonising our energy supply with energy efficiency and renewables.”
1) I see that you, clearly a scientist, are putting ideological “green” galore in front of reality and DATAâ€¦ try reading this first, and then come up and explain what failure are you EXACTLY talking about?

“Using historical production data, we calculate that global nuclear power has prevented an average of 1.84 million air pollution-related deaths and 64 gigatonnes of CO2-equivalent (GtCO2-eq) greenhouse gas (GHG) emissions that would have resulted from fossil fuel burning. On the basis of global projection data that take into account the effects of the Fukushima accident, we find that nuclear power could additionally prevent an average of 420,000-7.04 million deaths and 80-240 GtCO2-eq emissions due to fossil fuels by midcentury, depending on which fuel it replaces.”

At the same time consider that, study by the GCEP group at Stanford, published on peer-reviewed journal, main author is M. Dale, the 180 GWp of global PV world installations have NOT YET saved a single Wh of energy!â€¦ the balance is still negative, more energy has been used to produce them than the energy generateddâ€¦ and regarding the GHG emissions budget it is even worse, the break-even point is years ahead to come. I am recalling scientific studies, here, not pie in the sky dreams of some scientifically-illiterate green-organisation spokeperson, OK?

2) Talking about costsâ€¦ why is it that Germany (80 GW of wind and PV) and Denmark (more than 50% wind electricity) have the highest costs of electricity? Maybe because the average kWh generated by PV in Germany costs almost 30 Eurocents?â€¦ while nuclear costs 4.5â€¦ and in fact the latter has a cost which is so much lower that the geniuses of Energiewende have decided to tax every gram of enriched uranium inserted in the said reactors at the tune of 130 Euro to fill in the black hole of renewables’ deficit budget?
Or why is it that Italy, the second PV market in EU, obliges its electricity customers to pay 28 cEuro/kWh, that is 6.7 BILLION Euro/year for 20 years just to produce a scant 8% of the electricity it uses? And you’d probably call the 7 billion Euro EPR a “very costly solution”? 🙂

Just yesterday I’ve driven on the A7 highway along the Rhone valley, in France, southboundâ€¦ in a matter of 20 minutes I’ve passed in front of the Cruas-Meysse and Tricastin nuclear power stationsâ€¦ i.e. 2x 4×920 MWe reactors (small ones) which take less than 2 square km of land to produce, combined together, more than 45 TWh of electricity/yearâ€¦ 24h/24, at 55 Euro/MWh costâ€¦ that is more than all of the wind turbines of the UK, or 2x the output of 19 GWp of PV in sunny Italyâ€¦ what more proof do you need and/or want?

To conclude: how can any rational, scientifically-minded person even simply think that the highest specific energy source (baseload and dispatchable), which causes no direct GHG emissions could be replaced by the lowest specific energy source (intermittent and non dispatchable), which by virtue of their intermittency need the support of fossil-fuel-based sources is mind boggling to say the leastâ€¦ it simply proves once more that there is no RATIONAL discourse possible with ideologically-based reasoning. A real pity.

Cheers.

• Pete says:

Again you have either failed to read my post correctly or else you are deliberately misrepresenting what I say. I am not saying that the energy density of Uranium is not 83,140,000 MJ/Kg. In fact I quote this figure at the beginning and use it in my subsequent analysis. What I am saying is that figure is misleading .
â€œ if you go at a store and buy a 10 Euro item, pay with 50 Euro bill, and donâ€™t bother to take the 40 Euro cash back does not mean that your item has cost 50 Eurosâ€¦ it is that simple.â€?
Theoretically using lexical semantic analysis you are correct that the item still cost 10 Euros. However, in reality most people will think, quite correctly, â€œshit I’m 40 Euros downâ€? – that is my point.
The massive inefficiency of current nuclear fission is not a good thing. That over 90% of the theoretically available energy is still present in the spent fuel is not a good thing. You could design a gas power plant that only burnt 10% of the gas, then reprocess the waste gas to extract some of the remaining 90% of the gas, then burn it again at 10% efficiency and then throw it away. It is obvious that this is not a good way of going about it but it is analagous to what the nuclear industry does using current technology.
Reprocessing was not originally developed for ‘once through’ reactors but for fast breeder reactors. However, they have been spectacularly unsuccessful â€“ Dounray in Scotland, Phenix and Super Phenix in France. It was not just the cost but also overcoming the technical difficulties. Reprocessing does reduce the demand for fresh Uranium by 16-25% (although this is much less on an energy balance) but is highly polluting and expensive. The National Academies (Nuclear Wastes: Technologies for Separations and Transmutation) estimate that it would cost \$100billion to reprocess existing spent fuel in the USA â€“ it is not going to happen.
I look at what is really happening now and not taking into account the promises of the nuclear industry of what may happen in the future. You could argue that the energy density of coal is a lot higher because ‘theoretically’ the carbon and hydrogen in it could be burnt in some future fusion reactor â€“ or perhaps we could beam it up to the Star Ship Enterprise and use it in their matter/anti-matter reactors?
First of all I would like to point out that the correction for the enrichment and fabrication that I make are only there for completeness and only make a small percentage change in the final figure.
You are correct in that the Lenzen study is a meta analysis of all previous studies but that does not make it any less valid in fact it makes it a very good place to start. If, as in your analogy BMW state that an engine has 150HP but when someone looks at all other studies they find very different figures then BMW have a lot of explaining to do.
I am afraid that this reply is already getting too long so I am not going to address all your other points individually here – maybe in a future post. However, the idea that there is some global conspiracy against nuclear in favour of renewables seems rather far fetched. In fact what I see is that many governments in China, India, UK, France and USA are giving a lot of support to the nuclear industry but what is in fact happening is that renewables are rapidly outpacing nuclear in adding new capacity. Even in ‘sunny Lowestoft’ you can get 3200KWh per year from rooftop solar and in ten years time they will reach grid parity â€“ that will be well before any new nuclear plant in the UK will be built. The way in which we generate energy is changing and there is no place for current nuclear fission reactors.

• Cyril R. says:

Excellent analysis. To be fair you’d have to do the same for coal and gas, which also come in anything from poor to good quality ores. Especially in the case of gas, the low density must be considered. Natural gas at 1 atmosphere is 0.03 MJ/liter only, so still only 3 MJ/liter at 100 atmospheres. Whereas uranium of course being so dense its volumetric energy density is enormous. Factor of 10 or so greater than water for UO2 fuel.

• Pete says:

Thanks for the comment.
My main point is that the energy density quoted for Uranium is very misleading because U-235 is not mined in its pure state. Although I do not make it obvious I was comparing it with coal since it is also a solid that is mined. However, coal is found in 100% and does not have to be extracted from an ore. This is the reason why I did not take into account the energy used in mining (removing the overburden) since this will be about the same for uranium ore and coal. Uranium still has a very high energy density but not nearly as big as claimed.
It is good point about the energy density of natural gas etc. This is the reason why it is sometimes economic to use gas to create gasoline from tar sands. Methane can also be converted to gasoline by the Fischerâ€“Tropsch process or using ZSM-5 type catalysts.
Calorific value is also not the only factor in the usefulness of a particular energy resource. That is why thermal power plants (which are extremely inefficient) are used to convert fuels to electricity.