Physical Insights

An independent scientist’s observations on society, technology, energy, science and the environment. “Modern science has been a voyage into the unknown, with a lesson in humility waiting at every stop. Many passengers would rather have stayed home.” – Carl Sagan

Archive for the ‘Chernobyl’ Category

Helen Caldicott and the fine art of making up nonsense.

with 7 comments

Here’s a particularly egregious and scientifically vapid (as you’d expect, of course) interview with Helen Caldicott… recorded recently on some kind of “environmentalist” podcast.

Now… I could write a comprehensive technical deconstruction and debunking of essentially the whole lot… but I’m only one person, with a finite amount of time.

I’ll get started, just for now, by taking a look at just one particular sentence of nonsense from Caldicott.

Ask questions. Seek the evidence. Ask everybody questions, and never take anybody’s word for it. Are factual statements backed up by evidence? Are quantitative statements backed up by measurements, calculations, or derivations? Can those measurements or derivations be described and reproduced? Read everything you possibly can, and you decide.

Do people like Caldicott have the right idea? Or do people like George Monbiot have the right idea – that beneath the FUD, rhetoric and hysteria, these people have absolutely no real evidence, facts, knowledge or technical literacy at all?

HC: “Well it won’t recover. These accidents go on forever because plutonium’s half-life is 24,400 years. It lasts for half a million years. Thirty tons of plutonium got out at Chernobyl.”

Thirty tons of plutonium “got out” at Chernobyl!?

Personally, that reads many thousands of counts per minute on my baloney detector.

Let’s follow Dr. Caldicott’s favourite piece of advice… let’s read her book. Surely, just like all of Caldicott’s other “references” usually are, it’s got to be “in my book”, right?

“Plutonium is so carcinogenic that the half-ton of plutonium released from the Chernobyl meltdown is theoretically enough to kill everyone on Earth with lung cancer 1100 times, if it were to be uniformly distributed into the lungs of every human being.”

(From Nuclear Power is Not The Answer).

Hmmmm. Curious. It looks like we’ve gone from “a half-ton” in the book to “thirty tons” in this recent interview. Well, so much for “you should read my book… it’s all in the book!”

(By the way… that “kill everyone on Earth with lung cancer 1100 times…” bit is complete baloney. But that’s a story for another day.)

Reactor-grade plutonium typically consists of approximately 1.3% 238Pu, which has a half-life of 87.7 years and a specific activity of 634 GBq/g, 56.7% 239Pu, which has a half-life of 24,110 years and a commensurately far smaller specific activity of 2.3 GBq/g, 23.2% of 240Pu, with a half-life of
6564 years and a specific activity of 8.40 GBq/g, 13.9 % of 241Pu, with a half-life of 14.35 years and a specific activity of 3.84 TBq/g, and 4.9% of 242Pu, with a half-life of 373,300 years and a specific activity of 145 MBq/g.

Taking the weighted sum of all the above, we find that the overall specific activity of reactor-grade plutonium is 545.3 GBq/g, predominantly due to the 241Pu and the 238Pu content.

(Reactor-grade plutonium is considerably more radioactive than weapons-grade plutonium, due to the presence of substantial concentrations of these relatively unstable, high-activity plutonium nuclides. Weapons-grade plutonium is almost entirely 239Pu, which despite being a good fissile fuel, is more stable and less radioactive. The radiological heat output of 238Pu, gamma-radiation (from the 241Am daughter of 241Pu) and the high rate of neutron emission from the spontaneous fission of 240Pu all make these nuclides extremely deleterious and undesirable in nuclear weapon design and engineering.)

The best value determined based on the available data for the quantity of plutonium (a reactor-grade cocktail of different plutonium nuclides) released at Chernobyl is, as published in the reports of the Chernobyl Forum, 3 PBq (3×1015 Bq).

The approximate total mass, based on the best available data, of plutonium released into the environment at Chernobyl is 3 PBq divided by 545.3 GBq/g.

As the British physicist David Mackay put it, I’m not trying to be pro-nuclear. I’m just pro-arithmetic.

It’s 5.5 kilograms.

Incidentally, that’s a very small amount of plutonium compared to the amount of plutonium that has been dispersed around the environment from half a century of nuclear weapons testing. 5.5 kilograms of plutonium is, approximately, the amount of plutonium in the pit of a single nuclear weapon. A single zero-yield “fizzle” of a nuclear weapon with no fission, or a zero-yield one-point-implosion safety test, or the accidental HE explosion (without proper implosion of the primary, as in the Palomares and Thule accidents) of a single nuclear weapon will disperse a roughly comparable mass of plutonium into the environment. (But less radioactivity, since weapons-grade Pu is less radioactive than reactor-grade Pu.)

So, Caldicott has gone from exaggerating the true number by a factor of approximately 100 to exaggerating the true number by a factor of approximately 6000.

Anyway… let’s just step back a minute. 30 tons of plutonium released at Chernobyl? Let’s apply what scientists, engineers and technologists sometimes refer to as the “reasonableness test” or the “smell test”. Can you quickly “smell” the data and determine if it is roughly plausible or not?

The total mass of uranium dioxide fuel in the fuel assemblies of a fully fueled RBMK reactor is about 180 tonnes. That’s about 159 tonnes of uranium, if you take off the mass of the oxygen in the uranium dioxide. When LEU fuel is irradiated at a typical burnup in a nuclear power reactor, about one percent of the mass of the original uranium ends up as transuranic actinides, mostly plutonium, by the time the fuel is removed. So, that’s a total plutonium inventory in the Chernobyl reactor of approximately 1.6 tonnes.

So, if we make a conservative, pessimistic and entirely unrealistic assumption that 100% of the plutonium inventory in the nuclear fuel was entirely vaporised and released into the environment during the Chernobyl accident, that would be 1.6 tonnes of plutonium released to the environment. (In reality, that fraction was something more like 0.34% of the total inventory of plutonium within the irradiated uranium dioxide fuel.)

So, does “thirty tons” pass the smell test? Not by a long shot.

Written by Luke Weston

April 23, 2011 at 6:47 am

The battle for Chernobyl.

with 18 comments

Last month I got into a discussion with some people about the Chernobyl disaster, following the 22nd anniversary of the catastrophic Soviet reactor accident, and this documentary film was mentioned:

The Battle for Chernobyl.

To put it lightly, this film is an astonishing bunch of rhetorical baloney.

I’m not trying to downplay the public health consequences of the Chernobyl accident – but I’m downplaying the inaccurate or false claims made by certain groups, as distinct from the body of evidence of real, documented and substantiated (and very significant impacts).

Despite the known public health impacts, some people continue to make claims that are either just not true or are completely unsubstantiated – for example any claim that there are children, today, with an increased incidence of thyroid cancer, which just isn’t true – any children who were exposed to the short-lived iodine-131 source term in 1986 are adults today, 22 years later, and the iodine-131 decayed away quickly, within months.

Now, to look at the video:

From the gaping hole, a spray of fire, charged with radioactive particles in fusion, sprays a thousand meters into the sky.

Right from the outset, it’s completely obvious that for the next hour and a bit, science is tossed aside, and rhetoric is the first and only order of affairs.

The radioactive fallout is going to be 100 times greater than the combined power of the two atomic bombs dropped on Hiroshima and Nagasaki.

Some simplistic comments have often been made in which the radioactive release of the Chernobyl event is claimed to be 300 or 400 times that of the bomb dropped on Hiroshima. However, in sensible terms of radiological impacts, the two events can not be simply compared with a number suggesting that one was x times larger than the other.

Radioecology after Chernobyl – some good literature.

The total combined energy yield of both of the nuclear weapons used in Japan was about 35 kilotons of TNT equivalent – or about 41 gigawatt-hours. The Chernobyl Unit 4 reactor, with a thermal power output of about 3 gigawatts, produced that same amount of energy, and created about the same amount of fission-product activity, every 13.6 hours or thereabouts. Given that a nuclear power reactor contains fuel that has provided that kind of power output for perhaps as long as several years, of course there’s a larger inventory of radioactivity contained in the reactor fuel.

Iodine tablets swallowed to counteract the effects of radioactivity.

Iodine prophylaxis only prevents the body from uptaking iodine from the environment – which might be contaminated by radioactive iodine-131. It in no way “counteracts the effects of radioactivity”.

“The radiation level above the reactor is over 3500 R, almost nine times the lethal dose.”

3500 R over what length of time? The strength of an ionising “radiation field” in such a situation can only sensibly be expressed as roentgens (or sieverts or similar unit) per hour (or per unit of time).

0:36:40

If over six hundred pilots were “fatally contaminated with radiation”and killed, and this is known to be true, why have the Chernobyl Forum, the IAEA, the WHO, the UNDP, the UNSCEAR, Russian or Ukrainian governments never mentioned it? Can it be proven to be true, before the international community, by these people?

0:37:08

Why does none of this film show any artefacts on the film resulting from radiation damage?

0:38:20

The infamous “elephant’s foot” “magma” doesn’t look “white-hot” at this stage, although that’s how it’s described.

0:43:45

Again, the level of radioactivity is implied to be so very high – and it was high – yet it was not high enough to leave artefacts on the camera film. I don’t know exactly what sort of radiation dose is required to effect a piece of photochemical film (Remember that stuff, that was used before digital photography?), but I really expect it to show some damage under these conditions.

0:44:45

If you’ve got documentary evidence of these lives lost as a direct result of the disaster, that don’t appear in any of the UN’s findings, then I’m sure the UN would love to hear about it.

0:52:30

Oh dear – it’s “imagined” health physics, romanticised Hollywood fiction style.

“It finds a way in, and knocks you out”.

1:03:00 or thereabouts:

7000 R/hr – and still no effect on the video camera film. I wonder how strong the ionising radiation field needs to be to affect it?

1:12:30 -

“…The visit stirs up painful memories. He was fatally exposed to radiation during the seven months he spent covering the battle. Since then, he’s had to be hospitalised for over two months each year.”

He was fatally exposed to radiation? Oh, really? So you’re reanimated a dead man to interview for the program?

Chernobyl showed us the true nature of nuclear energy in human hands

No, Chernobyl showed us the potential for folly associated with the Soviet way of doing things back then. Keep in mind that the non-Soviet world has never even come remotely close to experiencing such an accident.

1:31:20:

“Inside, there are 100 kilograms of plutonium.

One microgram is a lethal dose for a human being. That means there is enough plutonium to poison 100 million people.”

Even assuming that “one microgram of plutonium is a lethal dose for a human being”, which it isn’t, I expect that somebody who is really a nuclear physicist should know how to count, and not allow such a glaring error of arithmetic to go uncorrected.

“The half-life of plutonium is 245,000 years.”

In order of descending half-life:

Pu-244: 80 million years

Pu-242: 373,300 years

Pu-239: 24,100 years

Pu-240: 6564 years

Pu-238: 87.7 years

Pu-241: 14.35 years

Pu-236: 2.858 years

The nuclides bolded are the most common ones. I don’t know about you, but Iexpect someone who is a nuclear physicist to get that right, and not just pull some nonsense number out of thin air! Again, not one of these plutonium nuclides has the half-life claimed in the film. What’s more, no credible nuclear physicist would state that “the half-life of plutonium is such-and-such” without specifying which nuclide he was talking about.

But wait – if you’ve watched the video, there are a couple more scenes that you almost certainly haven’t overlooked:

“Yet, it is thanks to these men that the worst was avoided. A second explosion, ten times more powerful than Hiroshima, which would have wiped out half of Europe.”

Yes, you heard that correctly. They claim that a  150 kiloton nuclear detonation could have happened. See below, for what I think of that.

0:34:00 – 0:35:00

The ensuing chain reaction could set off an explosion, comparable to a gigantic atomic bomb.

“Our experts studied the possibility, and concluded that the explosion would have had a force of three to five megatons. Minsk, which is 320 kilometres from Chernobyl, would have been razed, and Europe rendered uninhabitable.”

A 3 to 5 megaton nuclear detonation.

I apologise for putting this bluntly, but there’s only one thing I can say to that. What complete and utter bullshit.

They trump out the nuclear weapon explosion stock footage and everything. This is quite possibly the most blatantly shameless, ridiculous, completely falsifiable and utterly ridiculous example of shameless and absurd anti-nuclear-power propaganda I have ever seen.

Written by Luke Weston

May 8, 2008 at 3:27 pm

Anti-Nuclear Quote of the Day.

with 8 comments

Doctors now estimate that about 160,000 children below the age of seven living in the Ukraine in radioactively contaminated areas are at risk of developing thyroid cancer from radioactive iodine 131.

No, there are no children in the Ukraine below the age of seven who are at an elevated risk of developing thyroid cancer due to the Chernobyl accident. In fact, there are no people in the Ukraine, or Belarus, below 19 or so years of age who are at any increased risk of developing thyroid cancer due to the Chernobyl accident.

Why? Because they were never exposed to any radioactive iodine-131 source term.

I-131 has a short half-life: 8 days.

The Chernobyl Forum puts the release of I-131 from Chernobyl at 1.8 EBq – that’s 1.8 x 10^18 Bq; a hell of a lot of radioactivity. Because of what happened to Chernobyl Unit 4, and because Iodine is so volatile and reactive, that represents nearly the entire amount of I-131 in the nuclear fuel.

1 year after the disaster, 0nly 0.88 microcuries of I-131 remained in the environment, undecayed. (I-131 has a specific activity of 1.2 * 10^5 Ci/g).

After 1.83 years – one year and 10 months – there is a 90% chance that there is not one single I-131 atom left undecayed. This is all rather straightforward to calculate – I won’t bore you all with it, unless somebody wants to challenge my calculations – feel free.

There are no children being exposed to I-131 from Chernobyl today. The only people with an increased risk of thyroid cancer are those who were there in 1986-1987, during and immediately after the accident, when the I-131 was present.

Written by Luke Weston

January 21, 2008 at 8:55 am

Climate of Hope – an anti-nuclear look at nuclear energy, energy systems and climate change.

with 6 comments

http://www.engagemedia.org/Members/scottludlam/videos/climateofhope.mov/download

(168Mb video download, running time approximately 30 minutes)

This is a documentary video produced by the Anti-Nuclear Alliance of Western Australia – whilst they clearly make some statements that I contend, for the most part, the video is well produced, and the graphics and so forth are very well made.

This video starts off looking promising serves as a good factual primer on the science of the nuclear fuel cycle, energy generation, and the issue of fossil fuels and artificial forcing of the greenhouse effect. One starts to think, upon watching the first 5-10 minutes, that this is a good unbiased piece, with the film focussed on statistics and factual scientific and historical discussion, with none of the emotionally manipulative rubbish that anti-nuclear-power groups often produce.

It’s worth watching, anyway.

Now, a rebuttal of the parts I think deserve a rebuttal. Suffice to say, there’s a lot, and once I get ranting, it can be difficult to stop.

I’m sure you’ve all heard all this before – this is preaching to the converted. But I needed to get it off my chest – again.

200 tons of U3O8 is about the appropriate amount of Uranium required to fuel a nuclear power reactor for one GW-year. Assuming 0.15% U3O8 in the ore, then 133,200 tons of ore must be processed to support one GW-year of reactor operation, so, these numbers are OK.

It is claimed that the Olympic Dam mine in South Australia consumes 33 megalitres of water a day. I don’t have a reference for this data in front of me, so I’ll take their word for it.

However, since we’re talking about the nuclear fuel cycle, it must be remembered that Olympic Dam is predominantly a copper mining operation, producing about 220,000 tons of copper annually, along with a relatively minor amount of uranium, about 4500 tons of U3O8.

The other elements present in the orebody at Olympic Dam – uranium, silver and gold – are combined together in the orebody, with the uranium extracted during the processing of copper ore – essentially, a byproduct of copper production. Silver and gold, along with selenium and tellurium in small quantities, are extracted from the “anode slime” produced in the electrolytic refining of copper. Thus, even if the Uranium was not being extracted and marketed, the same amount of ore is still being mined out of the ground.

Now, I’m not an expert on mineral extraction and mining operations, but I will make the rough assumption that the production of one ton of copper metal consumes the same amount of water as the production of one ton of Uranium oxide. Therefore, we infer that Uranium production at Olympic Dam consumes 2% of the total amount of water, or 660,000 litres per day, or 53.5 kilolitres of water per metric ton of uranium oxide produced.

If 200 tons of Uranium Oxide is fuel for a 1 GW nuclear power reactor for one year, and that reactor operates with an 80% capacity factor, then the mining and milling of Uranium at Olympic Dam, then, consumes 1.53 megalitres of water per TWh of electricity produced from that uranium.

For comparison, the mining of coal consumes about 200 litres of fresh water per ton of coal produced. Given that a typical coal-fired power station consumes about 0.5 metric tons of coal to produce 1 MWh of electricity, the mining of coal for electricity generation consumes 100 megalitres of water per TWh of electricity production.

Considering ore with a uranium oxide concentration of 0.15%, as above, 133,200 tons of ore needs to be mined to operate a typical, current technology, 1 GW LWR for one year. A 1 GW reactor operating for one year with a capacity factor of 80% produces 7 TWh of electrical energy – hence, 19 tons of ore mined per GWh. For comparison, again, 500 metric tons of coal needs to be mined and burned to generate the same amount of electricity.

Given that once used nuclear fuel is removed from a typical current reactor, a full 96% of the fuel material, by mass, is Uranium, completely unchanged from when it went into the reactor, and a further 1% of the fuel is good nuclear fuel in the form of plutonium, strictly speaking, if this uranium is recycled and used efficiently, then only 3% of current uranium fuel consumption is needed – 570 metric tons of uranium ore mined per TWh, as contrasted with 500,000 metric tons of coal per TWh.

The “tailings” from Uranium mining contain the radioactive daughter products of Uranium-238 – Thorium-234, Protactinium-234, Uranium-234, Thorium-230, Radium-226, Radon-222, Polonium-218, Astatine-218, Radon-218, Lead-214, Bismuth-214, Polonium-214, Thallium-210, Lead-210, Bismuth-210, Polonium-210 and Thallium-206.

Of these 17 radionuclides, only five have significantly long half-lives – U-234, Th-230, Ra-226, Pb-210 and Po-210. The remainder have half-lives of between 24 days for Th-234, down to 1.5 seconds for At-218, and 164 microseconds, for Po-214.

Must the tailings from Uranium mining be isolated from the environment for “tens of thousands of years”? Well, the half-life of U-234 is 245,500 years, and the half-life of Th-230 is 75,380 years. However, these half-lives are dwarfed by the half-life of Uranium-238 itself, with a half-life of 4.47 billion years, created in supernovae, billions of years ago.

There is no nuclear transformation of these tailings during uranium extraction – all these daughter products are produced in exactly the same quantities that they were all originally present in, in the original uranium bearing rock.

As such, these radioactive minerals can simply be put back in the original mine, and sealed up with the rock that was originally extracted in the mining operation. Since this is where all these radioactive minerals came from in the first place, the same nuclides, in the same quantities, it is hard to believe that such practice is somehow unsafe or ineffective.

Now, we have the claim that uranium enrichment is a key technology for nuclear proliferation. Uranium must be enriched up to a very high concentration of U-235 for use in a nuclear weapon, and uranium enrichment plants, especially those capable of producing weapons grade material, are very large scale industrial facilities, taking up great volumes of space and consuming a significant amount of energy themselves – they are not easy to hide. The great difficulty involved in the enrichment of uranium, especially to very high levels, is the main reason why plutonium is greatly preferred as the basis for nuclear explosives. Uranium enrichment plants employed in the civilian nuclear fuel cycle can be subject to inspection by the International Atomic Energy Agency, where the nations using them are signatories to the NPT, and international schemes such as the Global Nuclear Energy Partnership can allow nations access to nuclear fuel technology whilst controlling the widespread employment of potentially proliferation-sensitive technologies.

Now, we have the big scary looking list of radionuclides, and accompanying half-lives.

Let’s see – Selenium-79, Zirconium-93, Strontium-90 and so forth. OK, these are reasonably long lived fission products – they comprise the 3% by mass of the used fuel that is not usable as recycled fuel. Some of these materials are valuable, and have potentially important and economical industrial applications, however, it is unlikely that world production of such materials in nuclear reactors will all be consumed, meaning that a significant portion constitutes radioactive waste which needs to be disposed of – most likely, in a deep geological repository.

Rubidium-87 has an extremely long half-life – 49 billion years – meaning that, like Uranium-238 and U-235, it is abundant on Earth, as a cosmogenic nuclide created in supernovae, and comprising 28% of all Rubidium occurring in nature. Similarly, Potassium-40 is a naturally abundant, cosmogenic, primordial radionuclide, which is not created artificially in reactors.

Krypton-83, with a half-life of 10 years… and Calcium-42, claimed to have a half-life of 14,000 years… now just wait one minute. These nuclides are stable – non-radioactive. Whilst I can see how it might be possible to get Kr-83 confused with Kr-85 – a fission product with a half-life of 10.78 years – there are no radioactive nuclides of calcium with a half-life of anything close to that figure. Anyway, Ca-42 is not a fission product. Yttrium-90 is the decay product of Sr-90, with a half-life of only 64 hours.
We see Cobalt-60, Iron-55 and Nickel-63 and Nickel-59 – whilst these themselves are not fission products, they are produced as neutron activation products in the steel and metal structures of the intra-reactor assemblies and reactor vessel – only becoming significant in the form of the intermediate-level waste stream produced during decommissioning of the power reactor. Whilst small amounts of Carbon-14 and Tritium are produced in the cooling water and similar during reactor operation, Beryllium-10 is quite uncommon.

Whilst it is claimed that used nuclear fuel needs to be isolated from people and the environment for hundreds of thousands of years, the radioactive fission products that make up the waste component of the used nuclear fuel – only 3% by mass, remember – will remain significantly radioactive for only 300-500 years.

The film claims that in time, the waste “will escape” even the best engineered containment, and that it is not clear if deep geological disposal of radioactive waste will be possible in practice – however, the process of radioactive decay is absolutely immutable, and the waste only needs to be isolated from the environment for perhaps 500 years, until it is no more radioactive from the uranium ore whence it came – assuming the actinides present are consumed via sensible recycling of the fuel.

Observation of the two-billion year old natural nuclear fission reactors at Oklo provides conclusive empirical evidence that a geological repository is capable of isolating these radioactive waste products from the environment over timescales up to billions of years – amply sufficient for even the longest lived nuclides to completely decay. When the operation of the sixteen nuclear reactors at Oklo was over, nature showed that it could effectively contain the radioactive wastes created by the reactions. It is clear, from this observation of the physical characteristics of nature, that it is possible to isolate such radioactive materials from the environment over the time scale required.

Sweden’s SKB – amongst other such efforts around the world -is engineering a permanent, deep underground, repository for radioactive waste, that requires no monitoring by future generations.The spent nuclear fuel will not be reprocessed, but the used fuel assemblies will be encapsulated in copper. The copper canisters will then be deposited in the bedrock, embedded in bentonite clay, at a depth of 500 metres.

 

The KBS-3 method used by SKB calls for the spent nuclear fuel to be encapsulated in copper. The copper canisters will then be deposited in the bedrock, embedded in clay, at a depth of about 500 metres. When deposition is finished the tunnels and rock caverns will be sealed.

SKB has chosen to build the repository using materials that are present naturally in the earth’s crust. By studying nature we can find out how copper, bentonite clay, rock and uranium dioxide behave both under different conditions and over different periods of time. By studying the radioactive byproducts of nuclear fission at Oklo, ancient natural cement in Jordan, natural copper in southern England, bentonite clay in Italy, concentrated Uranium deposits in Canada, and so forth, scientists understand the properties of these materials and phenomena that can occur over geologically long spans of time – longer than completely manmade experiments can cover. Analogues are often used to test models, which are in turn used to calculate the solubility of radionuclides in the groundwater.

The fuel will be placed in leaktight copper canisters with a cast iron insert. The canisters will then be transported down to a deep repository consisting of a system of horizontal tunnels at a depth of 400–700 metres in the bedrock.

The tunnels will be about 250 metres long and spaced at a distance of about 40 metres from each other. On the floor of the tunnels, deposition holes will be spaced at intervals of about 6 metres. The copper canisters will be deposited in the deposition holes and surrounded by a buffer of bentonite. When deposition is finished, the tunnels and shafts will be filled with a mixture of crushed rock and bentonite.

The leaktight copper canister will keep the spent fuel completely contained. The buffer of bentonite clay will protect the canister against corrosion attack and rock movements. If a crack should form in one of the canisters, the buffer and intact parts of the canister will prevent water from entering the canister. The buffer will also prevent radionuclides from leaving the canister. The rock will provide an environment where the function of the engineered barriers is preserved for very long periods of time. The rock and the great depth of the repository will keep the spent fuel isolated from man and the environment.

The copper canister that will surround the spent nuclear fuel is nearly five metres long and has a diameter of just over one metre. It weighs between 25 and 27 tonnes when filled with fuel. The outer shell consists of thick copper, and inside is an insert of nodular iron (a kind of cast iron) to provide sufficiently high mechanical strength.

As long as the canister is intact, no radionuclides can escape into the environment. Corrosion and mechanical forces due to movements in the rock are events that could lead to the breach of a canister. The canister is therefore made of materials that are designed to withstand such events. The canister is also designed to withstand major earthquakes following a future ice age.

Before the buffer is lowered into the deposition hole, the hole will be lined with blocks and rings so that a layer is formed between the inner walls of the hole and the canister. This layer is called the buffer, since its purpose is to dampen both mechanical and chemical changes in the rock.

The buffer consists of bentonite clay. It has three functions in the repository: to prevent corrosive substances from reaching the canister, to protect the canister from minor movements and to retard any radionuclides that might escape from a leaking canister.

The purpose of the rock is to isolate the waste. It is also supposed to provide a stable chemical environment for the canister and the buffer and protect them from whatever happens on the ground surface.

The groundwater moves in different ways in the rock’s fracture system. If radionuclides are dissolved in the water, they will accompany the movements of the water. The flow rate of the water varies both between different fractures and within a fracture, but is generally very low.

Virtually all radionuclides in the spent nuclear fuel can adhere to fracture surfaces, fracture minerals and the micropores inside the rock. Only iodine-129 and carbon-14 are somewhat mobile.

 

 

 

 

 

Reprocessing plants are not operated with the primary goal of separating plutonium from nuclear fuel – in a specifically plutonium-oriented fuel cycle, this may be the case; however, at present, the worthiness of reprocessing of used nuclear fuel comes primarily from recycling the uranium which makes up 96% of the fuel.

Even if no plutonium is extracted or recycled, recovering this uranium alone makes a vast difference to the long-term sustainability of the nuclear fuel cycle.

It is claimed that no commercially successful plutonium “breeder” reactor has ever been built – however:

* The BN-600 fast breeder reactor in Russia generates 600 MW of electricity, and has been in operation since 1980.

* The BN-350 in Kazakhstan first generated electricity in 1973, producing 150 MW, as well as 120 million litres of fresh water per day via desalination using the reactor’s heat. Whilst the project lifetime of the reactor officially finished in 1993, it continued to operate at reduced capacity until 1999 – a lifetime of 26 years.

* The Dounreay Fast Reactor in Scotland came online in November, 1959, producing an electrical output of 14 MW. The reactor was taken offline for decommissioning in 1977.

* The 233 MWe Phénix fast breeder reactor in France first supplied electricity to the grid in 1973 – it continues to operate to this day, with decommissioning expected possibly in around 2014.

* The 1242 MWe Superphénix fast breeder reactor, a full-scale nuclear power plant, completed construction in 1981 and was closed as a commercial plant in 1996.

* The Monju nuclear power plant in Japan, a sodium-cooled, MOX-fuelled fast breeder reactor, first acheived criticality in April 1994, and generates 280 MW of electricity. Whilst it was closed down for maintenance in 1995 following a sodium leak from the secondary coolant circuit, it is expected to be re-opened next year, and Japan has plans to construct more fast breeder reactors in the future.

It is claimed that major expansion of civilian nuclear energy will greatly increase the amount of nuclear material in circulation in the world – as though the “nuclear material” associated with nuclear power and nuclear weapons is the same thing!

The plutonium produced in power reactors is not weapons grade plutonium, and using such plutonium in a nuclear weapon is very difficult, and requires significant experience and knowledge in nuclear weapons physics – such technology is significantly harder to master than the already very difficult task of designing a nuclear weapon using plutonium.

It is claimed that he cleanup bill for a number of civilian and military nuclear facilities in the United Kingdom is estimated at more than 90 billion pounds – the nuclear weapons programs of the world’s nuclear weapons states, the Manhattan Project, and the Cold War arms race between the United States and the Soviet Union left a very significant legacy of radioactive wastes that were created and stockpiled, with little long-term attention to their safe disposal. Many of these wastes are not in forms which are easily managed, and cleaning them up will take much time and money.

But this is nothing to do with nuclear power – who estimates this cleanup bill, and how much of this cost is the nuclear energy industry responsible for? In the United States, and in other nations using nuclear power, the cost of final decommissioning and waste disposal is factored into the cost of marketed nuclear electricity.

It is claimed that “every stage in the nuclear fuel chain produces radioactive materials” – this is far from correct. It is only the operation of the nuclear reactor itself that “produces radioactive materials” – the radioactivity associated with uranium fuel production, uranium mining and mine tailings is all radioactivity that was originally, naturally present in the ground, and the radioactivity associated with used nuclear fuel and reprocessing wastes is radioactivity that was created in the reactor, along with the radioactivity of naturally occurring uranium.

Yes, exposure to high doses of ionising radiation can cause cancer, teratogenesis, and other deleterious effects on health. This is recognised by everybody – but these high doses of ionising radiation are not relevant to the context of the operation of nuclear power plants.

It is claimed that plant operators at Three Mile Island “fought to keep the reactor core from exploding” – this is simply ridiculous. A reactor core can not, does not, and will not explode – by what physical mechanism can it explode?

The small hydrogen explosion and hydrogen burn that occured within the reactor containment building had no significant engineering consequences – and there was never any danger of the overpressure from such a phenomenon breaching the containment vessel.

It is claimed that “operators released several hundred tons of radioactive gas” into the air, in order to prevent such explosion of the reactor.

It is estimated that a maximum of 13 million curies (480 petabecquerels) of radioactive noble gases were released in the course of the Three Mile Island event.

The noble gas – Krypton and Xenon – nuclides which are produced as fission products with any significantly large yield and which are radioactive, with a half-life so long as to be significant are Kr-85 (approx. 10 years), Kr-88 (2.8 hours), Xe-133 (5.24 days) and Xe-135 (9 hours).

If we assume the entire quantity of radioactive gas vented at TMI was the least radioactive of all the above, Kr-85, then the 13 MCi of radioactivity released corresponds to only 31 kilograms. So, not quite several hundred tons.

The average radiation dose to people living within ten miles of the plant was eight millirem, and no more than 100 millirem to any single individual. Eight millirem is about equal to a chest X-ray, and 100 millirem is about a third of the average background level of radiation received by US residents in a year.

Not a single person was injured, made ill or killed as a result of the Three Mile Island accident – and this is usually regarded as the worst nuclear reactor accident in history, outside the Soviet Union during the Cold War.

The Chernobyl No. 4 reactor experienced a massive power excursion, resulting
in a steam explosion, exposure of the reactor core and ensuing oxidation in
the extremely hot graphite moderator – nuclear grade graphite does not ignite
and burn per se, contrary to popular belief – resulting in a massive release of
radioactive material into the air. The reactor did not experience a “meltdown”.

Quantifying the effects of this event has proven to be difficult due to both
the widespread geographical influence of the radioactive contamination and the long time-scales involved in observing the potential long-term epidemiological consequences of exposure to high doses of ionising radiation.

The reactor was of a fundamentally flawed and unsafe design, and had had all safety systems shut off during a dangerous and unauthorized experiment.

On April 25, 1986, Chernobyl Reactor 4 was scheduled to be shut down for
maintenance. It had been decided to use this occasion as an opportunity to
test the ability of the reactor’s turbine generator to generate sufficient electricity to power the reactor’s water pumps, essential for safety systems, in the event of a loss of connectivity external electric power grid. The RBMK (Reaktor Bolshoy Moshchnosti Kanalniy) reactor requires water to be continuously circulated through the core, as long as the nuclear fuel is present.

A pair of diesel generators are normally used as a source of standby power, but these do not activate instantaneously. The reactor was, therefore, to be used to spin up the turbine, at which point the turbine would be disconnected from the reactor and allowed to spin under its own angular momentum, and the aim of the test was to determine whether the turbines running down could power the pumps while the generators were starting up.

The test was successfully carried out previously on another unit (with all safety provisions active) with negative results: the turbines did not generate sufficient power, but additional improvements were made to the turbines, prompting the need for a second test. As conditions to run this test were prepared, and the reactor electricity output had been gradually reduced to 50%, a regional power station unexpectedly went offline, meaning that the reduction in energy output needed to be postponed in order to supply demand on the electricity grid. The safety test was then left to be run by the night shift crew who would be working Reactor 4 that night. The power output of Reactor 4 was to be reduced from its nominal 3.2 GW thermal to 0.7 − 1.0GWth in order to conduct the test at the prescribed lower level of
power. However, the new crew were unaware of the prior postponement of the reactor slowdown, and followed the original test protocol.

The 135-Xe buildup in the reactor core makes it dangerous to attempt to operate the reactor a few hours after it has been shut down, without great care and understanding of reactor operation. Starting a reactor in a high-Xe condition requires pulling the control rods out of the core much farther than normal, to compensate for the nuclear ‘poisoning’ by 135-Xe. But if the reactor does achieve criticality, then the neutron flux in the core will become quite high and the 135Xe will be rapidly consumed by neutron-induced transmutation – this has the same effect as very rapidly removing a great quantity of reactivity control from the core, and can cause the reaction to grow too rapidly, with the potential to achieve prompt criticality. For this to be attempted in any reactor is a massive lapse in judgment on the part of the operators, and is indicative of extremely bad operator training, lack of safety culture and awareness, and a lack of design features which should make such a procedure impossible, or mitigate its risks.

All these factors were present at Chernobyl.

Nuclear physicists and engineers – most notably Edward Teller – discovered such safety concerns in the context of the early graphite-moderated reactors built at the Hanford site in the US for plutonium production for the Manhattan project, some 40 years before the Chernobyl accident. The early scaled-up graphite moderated nuclear piles at Hanford were arguably the closest the Western world has ever come to building a Chernobyl RBMK style reactor.
Nuclear poisoning due to 135Xe was first discovered in these first such reactors. Teller and his colleagues quickly discovered and pointed out the potential safety concerns associated with graphite-moderated water-cooled reactors having a positive void coefficient. As a result of his team’s persistent voicing of safety concerns over such reactor designs, Teller, most infamous for his tireless advocacy of a strong nuclear arms program and continued argument testing and development of nuclear weapons, in fact became known as “the reactor opposer” around this era, and the graphite-moderated design was never used again in the United States, aside from the nine original military reactors at the Hanford site.

It is exactly this situation which played a large part in the Chernobyl accident: about eight hours after the scheduled maintenance shutdown, workers tried to
bring the reactor to a zero power critical condition to carry out the turbine test, but because the core was loaded with 135Xe from the previous day’s operation, the reactor power output could not be increased above 30 MWt, approximately 5% of what was expected. The operators believed that the rapid fall in output was due to malfunctioning of one of the automatic power regulators, not because of fission poisoning.

In order to increase the reactivity of the reactor, automatic control rods were pulled out of the reactor beyond what is allowed under safety regulations.

Despite this breach, the reactor’s power only increased to 200MW, still less than a third of the minimum required for the experiment. Despite this, the reactor crew’s insufficiently trained and inexperienced management chose to continue the experiment. As part of the experiment, the water pumps that were to be driven by the turbine generator were turned on; increasing the water flow beyond what is specified by safety regulations. Since water absorbs neutrons, this further increase in the water flow necessitated the removal of the manual control rods, producing a very precarious operating situation where coolant water and nuclear poisons were substituting the role of most of the control rods of the reactor.

The unstable state of the reactor was not reflected in any way on the control panel, and it did not appear that anyone in the reactor crew was fully aware of any danger. Electricity to the water pumps was shut off and, as the momentum of the turbine generator drove them, the water flow rate decreased, decreasing the absorption of neutrons by the coolant. The turbine was disconnected from the reactor, increasing the level of steam in the reactor core. As the coolant heated, pockets of steam formed voids in the coolant lines.

The operators were careless and violated plant procedures, partly due to their
lack of knowledge of the reactor’s design, and lack of experience and training.
Several procedural irregularities also contributed to cause the accident. One
was insufficient communication between the safety officers and the operators in
charge of an experiment being run that night. The operators switched off many
of the safety systems, which was generally prohibited by the plant’s published
technical guidelines.

To reduce costs, and because of its large size, the reactor had been constructed
with no containment vessel, and only a large concrete biological shield atop the
reactor, primarily designed for radiation protection for plant personnel whilst
working atop the reactor. This allowed the radioactive contaminants to escape
unchecked into the atmosphere after the steam explosion burst the primary
pressure vessel, and the graphite core started to “burn” – not catching fire, but
oxidising as it was heated to great temperatures, facilitating the dispersal of
radioactive material into the atmosphere.

The Chernobyl disaster has absolutely no relevance what so ever to the question
of how much radioactivity could conceivably escape from the reactor, reactor
vessel and containment structure into the environment in the event of a
nuclear accident involving today’s civilian light water reactors, since the Chernobyl
RBMK reactor didn’t have a containment structure at all, amongst many
reasons.
Given that the factors that contributed to the Chernobyl disaster have absolutely
no relevance whatsoever to the issue of nuclear energy, today, in the
Western world, by rights, on a rational, factual basis, the disastrous medical
consequences of the disaster have no bearing on the nuclear energy industry in
the United States or elsewhere.

Now, we have the claim that the Forsmark Nuclear Power Plant in Sweden “came within half an hour of a meltdown” in 2006.

On 25 July 2006, one reactor was shut down after an electrical fault. According to the Swedish Nuclear Power Inspection authority, SKI, the incident was rated 2 on the International Nuclear Event Scale.

According to Lars-Olov Höglund, a former construction chief at Vattenfall, it is the most serious nuclear incident in the world since the Chernobyl disaster and it was pure luck that prevented a meltdown.

Both SKI and the safety chief of Forsmark power plant disagree with that opinion and state that the incident was serious but the description provided by Höglund was incorrect and there was no risk of a meltdown.

The media hype in Sweden started with the “independent nuclear expert” Lars Olov Hoeglund stating that this was the “most dangerous event since Chernobyl” and “only luck saved Forsmark from a total meltdown”.

Originally titled “former construction manager” in media reports, Hoeglund has been promoted to “plant manager” and “CEO” of Forsmark in American and English media, and even head of the Swedish Nuclear Inspectorate in German media reports.

In reality, he was never employed by Forsmark. He was “construction manager” for some years at a Vattenfall mechanical engineering department.

He did spend some years at the Forsmark site as a constractor, but only at the waste storage and disposal facility, unconnected with the nuclear power plant.

Maybe more importantly, he has for years been locked in legal conflict with Forsmark (as well as Ringhals NPP), regarding some jobs that his consultancy tendered on but did not get selected for. Apart from this, he has, through legal appeals in environmental courts, delayed a number of projects at both Ringhals and Forsmark.

His claims regarding the shutdown at Forsmark in 2006 have never been substantiated by any credible source.

Regarding the “near miss” at Davis-Besse in the US in 2002, a breach in the Davis-Besse reactor’s corroded pressure vessel head would have
contaminated the reactor’s containment building with reactor coolant from the primary loop. All the radioactivity in such coolant would be contained within
the containment vessel. Emergency procedures would have protected the reactor from core damage, as with any Loss of Coolant Accident. Even the worst
possible situation in this case, a loss of reactor coolant, is far from being a “major catastrophe”, although it is a serious reactor incident. Since the carbon
steel reactor vessel is lined on the inside with a further inch of stainless steel, the corrosion of the outer carbon steel part of the reactor head, caused by a small,
persistent leak of boric acid, could not have completely breached the integrity of the pressure vessel, as stainless steel could not be corroded at all in such a way.

If the vessel was breached, in such a near-impossible manner, then the plant would be shut down, and would be offline for some time. The reactor may have even been, in the worst-case scenario, written off. But no radioactivity would possibly be released into the environment, thanks to the containment vessel.

It is claimed that under the Global Nuclear Energy Partnership, Australia is being promoted as the site for disposal of the world’s nuclear waste, and that sites are being selected for such.

There is simply no credible evidence what so ever that this is a widely promoted ideology, and especially not that it is widely accepted.

It would be kind of like thinking that Saudi Arabia has some kind of obligation to take the world’s production of carbon dioxide, for geosequestration, because they’re one of the leading producers of oil, wouldn’t it?

As the DOE themselves put it, The Global Nuclear Energy Partnership has four main goals. First, reduce America’s dependence on foreign sources of fossil fuels and encourage economic growth. Second, recycle nuclear fuel using new proliferation-resistant technologies to recover more energy and reduce waste. Third, encourage prosperity growth and clean development around the world. And fourth, utilize the latest technologies to reduce the risk of nuclear proliferation worldwide.

Through GNEP, the United States will work with other nations possessing advanced nuclear technologies to develop new proliferation-resistant recycling technologies in order to produce more energy, reduce waste and minimize proliferation concerns. Additionally, the partner nations will develop a fuel services program to provide nuclear fuel to developing nations allowing them to enjoy the benefits of abundant sources of clean, safe nuclear energy in a cost effective manner in exchange for their commitment to forgo enrichment and reprocessing activities, also alleviating proliferation concerns.

The nuclear fuel cycle is not heavily dependant on cheap fossil fuels – certainly not any more dependant on fossil fuels than the production of fossil fuels themselves, or the use of solar, wind, or other energy systems, and the life-cycles associated with them.

The idea that whole-of-life-cycle analysis can demonstrate that nuclear energy
is unsustainable, both on an energy intensity basis and a greenhouse gas intensity
basis, is based on a very limited set of highly dubious science, which has
been widely rebutted, and found to be irreconcilable with the body of scientific
literature established relating to the energy and greenhouse gas intensities of
the nuclear fuel cycle. This will be discussed in greater detail in a later section.
It should not be unreasonable to believe that one day, we can as a society dispense
with fossil fuels entirely, and use clean wind, nuclear and solar-generated
electricity to supply the energy inputs associated with mining and processing
raw materials such as Uranium, Aluminum or Silicon, and the construction of
energy infrastructure, with electricity, and advanced thermochemical processes
used to generate Hydrogen, as transport fuels, thus leading to solar, nuclear or
wind-based energy generation which truly does not produce any greenhouse gas
emissions at all.

The Rossing Mine in Namibia has a Uranium concentration in the ore of about
350 ppm, and produced 3037 tonnes of Uranium in 2004, which is sufficient
for about 15 GW-Yr of electricity with current fuel cycle and power reactor
technology. The energy used to mine and mill this Uranium is about 30 MW-yr,
thus corresponding to an energy gain of about 500.

Extrapolating this, for a Uranium mine to produce no net energy gain, it would
be required to have a Uranium concentration in the ore of no more than about
0.7 ppm. Given that the average concentration of Uranium in the Earth’s crust
is 1-3 ppm, one can expect that the majority of exploitable Uranium reserves
can reasonably be expected to produce a non-trivial energy gain, even utilizing current reactor technologies and current, inefficient 235U based nuclear fuel
cycles.

As I mentioned above, the energy inputs that go into the nuclear fuel cycle don’t
implicitly need to come from polluting, unsustainable fossil fuels. As the rest
of society moves away from fossil fuels to an energy mix of solar, wind, nuclear,
hydroelectric and other sustainable energy sources, so will the mining industry.
In fact, Australian hot fractured rock geothermal energy company PetraTherm
recently signed a memorandum of understanding to supply geothermal electricity
to South Australia’s Beverley Uranium mine by late 2009.

The EURODIF Uranium enrichment plant in Pierrelatte, France receives its entire energy supply from the nearby large Tricastin Nuclear Power Plant, on the same site – no indirect greenhouse gas emissions here, either.

To consider another example, the United States Enrichment Corporation’s Uranium
enrichment plant near Paducah, Kentucky operates using electricity – a
significant amount, about 3 GW at peak operation capacity – generated by the
Tennessee Valley Authority, and supplied via the normal electricity grid. The
TVA supplies energy to the electricity grid using a diverse mix of energy sources
– 11 fossil-fuel plants, six combustion turbine plants, five nuclear reactors and
twenty-nine hydroelectric dams. In 2006, 35% of TVA’s generation capacity -
which we can assume corresponds to 35% of the energy supplied to the Paducah
enrichment plant – was provided by these non-greenhouse intensive hydroelectric
and nuclear generation technologies.

There are a number of publications by Storm van Leeuwen and Smith (hereafter,
SLS) that have received considerable attention because of these authors critical
attitude regarding nuclear power.

There have been scientific counter arguments and rebuttals to their work published
by the World Nuclear Association, with a rebuttal by SLS, and by physicists
from the University of Melbourne, with a rebuttal by SLS, a response by
the authors; a second rebuttal, and a second response. The ISA report mentioned
above is also particularly critical of the work of van Leeuwen and Smith.
The arguments put forward in some of these exchanges are nothing new.

The study of Storm van Leeuwen and Smith neither states energy nor greenhouse
gas intensities, but instead presents temporal profiles showing break-even points
with gas-fired power plants. ISA, therefore, have therefore extracted all energy
coefficients from the study and applied them to a hypothetical nuclear fuel cycle
in Australia. For ores of 0.15% grade, they obtain energy and greenhouse gas
intensities of 0.66 kWhth/kWhe and 212 g CO2e/kWhe, respectively. If such
rich ores are assumed, the construction and decommissioning of the power plant
are the main contributions to energy and greenhouse gas emissions.

If lean ores are assumed (0.01% U), the situation changes drastically: Mining,
milling, and the clean-up of the mine site become the main components of the
total energy and greenhouse gas intensities. The energy and greenhouse gas
intensities are 1.63 kWhth/kWhe and 527 g CO2e/kWhe, respectively.
From a review of the literature concerning the energy intensity, sustainability
and greenhouse gas emissions intensity of nuclear energy over the whole of life
cycle, one notes that there is considerable agreement between numerous different
bodies of work, such as Vattenfall’s environmental product declarations, the
work of the University of Sydney ISA group, the World Nuclear Association,
and independent physicists from the University of Melbourne, just to name a
few, and they all demonstrate findings which are for the most part completely
inconsistent with the work of van Leeuwen and Smith.

Although the greenhouse gas emissions from the nuclear fuel cycle, even with low-grade Uranium ores, remain in the same order of magnitude as other sustainable non-fossil energy sources, this still ignores the point, as previously made, that the nuclear fuel cycle does not implicitly require fossil fuel generated energy to supply these energy inputs – although at present the nuclear fuel cycle
generates a comparatively tiny amount of greenhouse gases, just as does wind,
solar or hydroelectric energy – as clean non-fossil energy sources are developed
further in the future, this will change, and all energy generation will potentially be one hundred percent GHG emission free.

Sure, geothermal and hydro are baseload sources of electrical generation – hydroelectricity, along with nuclear, is one of the largest sources of clean electricity in the world. But if you don’t have the right geology in the right places, if you don’t have the rivers and water resources to play with, then hydro and geothermal are of limited use. Cogeneration – combined heat and power – is usually realised using natural gas, and whilst it realises an increase in the overall efficiency of energy conversion, you’re still burning a greenhouse intensive fossil fuel!

Follow

Get every new post delivered to your Inbox.

Join 75 other followers