Muons and Fukushima

Dear Reader,

One of the great problems right now is working out where the fuel in the damaged cores and the ponds is, and in what condition the fuel is in. We can take for granted that the fuel which was in units 1, 2 and 3 has been damaged by overheating. But the state of the fuel in the ponds was a bit more of a mystery to us.

After clearing the rubbish out of the pond at unit three it has been possible to inspect the pond, the pond is frankly in a bit of a mess. But the fuel seems to have escaped serious damage. Photographs have been taken of the fuel racks in the pond and it does not look like there has been been any dire melting or explosions in the pond.

I have seen that some samples have been taken from the pond at unit four to allow them to be examined (these were samples of unused fuel which were being stored in the pond at the time of the accident). The work so far suggests that the fuel in the pond is in good condition. This suggests strongly that no nuclear explosion occurred in the pond.

The other great question is the state of the reactors. I saw something interesting recently, it is a sensing system based on cosmic rays (muons). This looks to me like a good method for finding the fuel inside the damaged reactors without having to get up close and personal with the stricken reactors.

Another thing which needs to be done is for society to recover from the accident, I have seen some advice from the IAEA on the subject of remediation of the contaminated land (outside the nuclear reactor park). This document might be of interest to some of my readers. It includes a discussion of the cleaning of different types of areas which include farmland. As I predicted it does include the question of deep ploughing the land.

BNCT a great way to cure cancer

Dear Reader,

Recently I looked into the core of a nuclear reactor for the first time in my life, the closest I had been before then was looking through the door in the inner shielding at the top cap of a defunct reactor which had been shut down decades ago.

I was standing in the operating position above the water pool of a 250 kW reactor which is used for research, training and for treating cancer; the reactor was not running while I was visiting. Apparently in that location the dose rate is about 400 microsievert per hour when the reactor is running, while this dose rate is no where near the level which would cause an injury or death. As the 1970s LD₅₀ dose for radiation was about 3.5 grays, it would take 8750 hours there to reach this dose. The 365 days required to get this dose would mean that the self repair mechanisms in my body would reduce the baneful effect on my body. I do not think that it would make me fall down dead, but within a week or so I would be hitting my yearly limit, so that I would not want to linger in that spot while the reactor is running.

It was an interesting view looking down through a 6 meter pool of water at the core of the reactor; this reactor is a type which is not designed to make electric power. Instead it is designed to make neutrons for radioisotope production, for training and for the treatment of cancer. Almost twenty years ago the reactor was modified to allow it to be used as a neutron source for the treatment of cancer by the boron capture method.

Now I know that some elements in society are very antinuclear but I would ask even the most antinuclear people to stop, read this and think for a while. Frankly I would like it if you shared my point of view but even if you do not come away from reading this with my point of view I accept that people are free to choose what they like to believe.

Now if you have the misfortune to get cancer then one of the treatment methods is radiation, now the problem is that it is best to give the cancer cells one heck of a going over with one almighty dose of radiation while only giving the healthy tissue a very small dose. This is the ideal but sadly with many radiation treatments it is not quite possible to do this.

The most common method seems to be either X-rays or gamma rays delivered from a source outside the patient. The problem with these treatments is that the beam of radiation damages all tissue that it passes through. One solution to try to spare the healthy tissue is to aim beams of radiation into the person from different angles so that the paths of all the different directions converge on the spot where the nasty tumour is. This is not a perfect way of doing things, no matter how good the radiation expert is they will damage some healthy tissue.

The next step up in controlled and localised dose is to implant a source into the person; it is possible to implant a small but intensely radioactive source right at the spot where the cancer is. This can be used to treat a range of different cancers which include cancer of the cervix, breast and prostate. As radiation obeys an inverse square law this treatment is often very good at sparing the healthy tissues.

If you double the distance from the source you make the dose four times lower, while if you triple the distance from the source then the dose is nine times smaller. I hope that you can now see that the effect should be very well localised in one part of the body. With the right choice of photon and beta particle energy you can make the dose even shorter ranged thus allowing you to wipe the smile off the cancer’s ugly face, send it away with its tail between its legs while leaving the vast majority of the person undamaged.

Sounds great doesn’t it! But there is a fly in the ointment. Today for some applications some of the greens are yelling that we need to stop using nuclear reactors. The problem is that for the generation of the radioactive sources often the only thing which will do the job is a nuclear reactor which has been optimised for a high neutron flux. To do this you need to make the core nice and compact and run the reactor with a highly enriched fuel. Here is one of the best arguments for keeping radioisotope production reactors, while they might not fit in with some people’s idea of what is green they do provide an affordable and reliable supply of lifesaving diagnostic and curative medical products.

Now some people might be yelling at the screen that we should ditch the old fashioned radioactive sources for medical use and use modern particle accelerators like LINACs. I would like to point out that the treatment systems based on radioactive sources are simpler and there is much less to go wrong. Using no more than a sheet of graph paper it is possible to predict the strength of a radioactive source on day X, while accelerators are more complex. I am aware of radiotherapy accidents in both Poland and the USA where accelerators have failed to behave as expected. Both cases caused some ugly overexposures of people.

Also to deliver the radiation just where it is needed to some where like the cervix or the prostrate it is not possible to do it with a typical medical accelerator. The way that the LINACs typically work is by whipping up electrons to very high speeds and then slamming them into a metal target. The change in velocity (deceleration) of the electrons cause them to emit very high energy gamma rays. An alternative second method is to use a gadget called a betatron. Both the betatron and the LINAC are suitable as replacements for the cobalt-60 based teletheraphy units which used radioactive sources to make beams of gamma rays, but they are not able to replace the treatments based on radioactive sources which are placed right in the tumours.

Now while brachytherapy is all very well, there is something even better. One of the problems with cancer is the oxygen effect. If tissue is nice and well oxygenated then low LET radiation like gamma and X-rays are good at causing harm. But when the tissue is poorly oxygenated then it has much less effect. While the surface layers of a tumour are often well oxygenated, the core of a tumour is often poorly oxygenated. What can happen is that when a tumour is given a dose of radiation the inner less oxygenated cells survive and then continue to grow thus making the tumour reappear.

But a high LET radiation such as alpha particles still works even if the oxygen content of the tissue is low. If boron is subjected to neutron bombardment then it forms alpha particles which are able to then do immense damage to the cancer while leaving the healthy tissue alone. The reason that this works is that the person is given a dose of a boron containing drug which mainly absorbs into the cancer cells. The drug used in Finland for this treatment is L-para-Boronophenylalanine, this is an amino acid bearing a B(OH)₂ group.

The boron-10 reacts with the neutrons to form alpha particles and lithium-7.

¹⁰B + n → ⁴He + ⁵Li

The helium and lithium-7 ions then damage the cancer cells, as the boron concentration in the healthy cells are low the healthy tissue gets a far lower dose. Here is a picture of the boron compound which is used for the treatment.

A molecule of the amino acid which bears the B(OH)2 group required for the BNCT

Now some of those of you reading this blog might not be the greatest enthusiasts of the nuclear sector, but I would like to caution the “antinuclear brigade” against throwing the baby out with the bath water.

While I am well aware that it is possible to make bombs using some nuclear technology, I would like to point out that Patrick Moore pointed out that the fact that car bombs made with ANFO (Ammonium Nitrate Fuel Oil) are bad. Frankly I have to say I strongly agree that ANFO based car bombs are perfectly horrible.

But he wrote that the fact that you can make a nasty large bomb out of a car, some ammonium nitrate fertilizer and some diesel fuel is not a good reason to ban any of these three items.

I would like to also point out that the nuclear equipment in the form of a radiotherapy reactor is not in a form which is suitable for use as a weapon, I think that the only weapon I had access to at the reactor site were some lead bricks in the radiochemical lab and the bright yellow extra long tongs. I think I can get some weapons which are more suitable for mindless violence from a typical garden centre !

I have to explain something to you, it is possible to use many objects as weapons but the fact that it is possible to employ or adapt an object into a weapon is never a valid reason for banning an object. I will give you an example, in Mr Archer’s prison diary it explains how one person once took a toilet brush, they cut off the bristles and then sharpened it into a sword. The fact that someone managed to adapt a toilet brush into a sword should not be used as an excuse to ban the things !

Alpha decay part II

Dear Reader,

As I sit typing in a railway carriage on the way home sitting near a young lady who is sporting a ”Nuclear power no thanks” badge, I sit here thinking about nuclear processes hopeful that the young lady does not notice what I am typing.

It is interesting to note that one of the physical effects which regulate the reactions which go on inside the red sun of the “Karnkraft nej tak” badge are the electrostatic forces which oppose fusion. The same forces have an effect on the reverse reactions (alpha emission, fission and all the cluster emissions which come between those two extremes).

Now since I had a rather short hair cut recently I can not demonstrate electrostatic attraction using a comb dragged through my hair. I will let you try that at home, also I do not have a cat to rub on a bit of plastic so I can not use that either.

But back to nuclear processes and electrostatics, to a first approximation the atomic nucleus can be treated as a charged sphere. The size is given by the following equation.

R = R_o (A)^0.3333

Where R_o is equal to 1.2 x 10^-15 m, while A is the total number of nucleons (the sum of the number of protons and neutrons) in the nucleus.

So radius of a plutonium-238 nucleus is 7.44 fm, while its daughter (uranium-234) has a nuclear radius of 7.39 fm while an alpha particle has a radius of 1.90 fm. Using these radii we can calculate the energy required to push the alpha particles from plutonium-238 back inside the nucleus.

To do this we need a few more equations from A-level physics.

As the capacitance of a sphere is given by

C = 4 π ε r

Where ε is equal to the permittivity of free space which is 8.854187817620 × 10⁻¹² F m⁻¹ or just 8.85 × 10⁻¹² F m⁻¹

We can use this to estimate the electrostatic energy required to hold an alpha particle on the surface of the uranium-234 nucleus. As soon as the alpha particle is taken out of the nucleus it is no longer being strongly bonded by the very short ranged but very strong attraction between the protons and neutrons in the nucleus (the strong force). So suddenly only the electrostatic forces apply to the system (the weak force and gravity are far far weaker)

This energy (28.5 MeV) is far greater than the decay energy of the plutonium-238 (5.593 MeV), as a result the alpha particle, what has to happen is that the alpha particle must overcome this energy barrier before it can leave the nucleus of the atom. What happens is that by quantum tunneling the alpha particle leaves the nucleus of the atom and then goes on its merry way. Here is a graph of the electrostatic energy in MeV vs the distance from the centre of the nucleus for both the alpha particle and the carbon-12 nucleus.

Electrostatic energy as a function of distance from the centre of the daughter nucleus

When the calculation is repeated for the loss of a carbon-12 nucleus from plutonium-238 to form radium-226 then I have estimated that the energy barrier is 74.5 MeV, while the decay energy is now higher at 22.5 MeV you now have a bigger barrier and some other things also help slow down the release of C-12 nuclei.

I hope to get onto these things later.

Pussy riot and the dose meters

Dear Reader,

The women who are alleged to be part of the punk band in Russia are still in trouble, I saw alleged because the punk band wear masks when then appear in public and at least one of the women who were arrested has claimed that she is not part of the band. I predict that this case will be an interesting one which we should keep an eye on.

A second thing which I have noticed is that a claim has been made that workers at the Fukushima site were told to tamper with their dosemeters to reduce the dose that they recorded. I do not want to sit in judgement on the matter as the full story has not been gathered. I think that guilt by accusation is deeply wrong.

Imagine a world where I could accuse TEPCO, Greenpeace or even you of being “in league with evil aliens from Mars who are planning to poison the school meals in Göteborg with mind distorting drugs” and then these companies or you are then punished based simply because I have made this accusation. Such a world would be a deeply wrong place, and I have to confess that I could not keep a straight face while typing that nonsense about aliens.

If you read the IAEA book (Lessons Learned from Accidents in Industrial Radiography) you will read about the dire actions of the small minority of bad industrial radiographic workers. One common bad behaviour is that some of the radiographic workers remove their dosemeters before they enter a high radiation area to do a source recovery operation, this is a behaviour which is calculated to hide an accident from the radiation protection authorities and also from their supervisor. I wholeheartedly condemn these attempts to sweep accidents under the rug, and I am displeased at the idea that the employers would encourage such a behaviour.

I hope that I am merely being “angry in the abstract” rather than being displeased by a real case of a employer trying to make false measurements.

I worry that in todays climate that some people will say or write anything to blacken the name of some unpopular person. I think that testilying is wrong. For example while Mark Brandon “Chopper” Read has done some rather unspeakable deeds, it would be wrong for me to make a false claim that he murdered ten policemen using a toothpick and a bag of dog treats. Just because someone like Al Capone has done many bad things it does not make dishonesty right.

Dose estimates

Dear Reader,

I have found an interesting document which is on the subject of the atomic bomb tests done years ago down under in Auz. Now before we get going, I do not want to get dragged into a debate regarding the rights / wrongs of nuclear bombs or the moral issues associated with bombs and their testing. What we will be dealing with here is just the reported facts.

A document has been released some time ago by the Australian government which gives estimates of the radiation doses which Australians were exposed to as a result of the bomb tests there.

What is interesting is that the doses are quite low, if the data in the document is true then the vast majority of the Australians were exposed to low doses of radiation. But before we look at the dose estimates lets look at what the current UK limits are.

The 1999 law (1999 Ionising Radiations Regulations) set the following yearly limits

20 mSv Radiation worker

6 mSv Trainees aged between 16 and 18

1 mSv The general public

While the 1980s Ionising Radiations Regulations set the upper limit for a radiation worker at 50 mSv per year.

If we look at table 7.27 in the report from down under we will see the results.

A. 78.9 % of the people involved had doses which were lower than the current UK limit for the general public (1 mSv). I hold the view that this low dose of less than 1 mSv is nothing to worry about.

B. Only about 4 % of people are in the above 20 mSv group, these are doses which would break current UK law for a radiation worker.

C. Very few people (19 people, 0.2 %) are in the above 50 mSv group. These doses are above the yearly limit in the 1990s for radiation workers.

D. About 6.3 % of the people had unknown doses, in some ways this is the most interesting and more worrisome group. Most of these people were in the Royal Australian Air Force.

What would be very interesting is if an alternative set of dose estimates or measurements exist from the same bomb tests. By the way if dose estimates get you angry, do not get mad at either me (I did not make the dose estimates) or someone else but do feel free to point out other dose estimates which you think are more trustworthy.

The horrors of polonium

Dear Reader,

I read recently how it has been suspected that Yasser Arafat may have been murdered using polonium-210. This claim that polonium-210 has been used for another murder made me think for a moment about radium-226 and its daughters. I can tell you that polonium-210 is one of the radioisotopes which most radiation workers love to hate. Polonium-210 and radon-222 are both alpha emitters which are able to diffuse through rubber and plastics. This makes them more mobile than plutonium is. When you write plutonium you have to be careful to understand that not all plutonium is born equal.

Plutonium-239 is a long lived alpha emitter which has a moderate activity per gram (and emits few gamma photons and neutrons), pellets of plutonium dioxide which have been sintered are solids which are clean to handle inside a glove box. I used to work with a nuclear fuel chemist (John Pecket) who used to make plutonium dioxide fuel, MOX and some very werido fuels. He told me how Pu-239 was a nice radioisotope to work with, while plutonium-238 was a nightmare in comparison. Pellets of plutonium-238 dioxide emit so much heat that they tend to glow red hot, they also tend to emit plenty of radioactive dust. He told me that if you place a Pu-238 pellet in a glove box then within days every surface in the box will be crawling with radioactivity. But even plutonium-238 will not pass through a neoprene glove. Thus at least it will stay inside the glove box, the worst radioisotopes I know are alpha emitters which are very mobile.

You can think of low LET radiations (beta / gamma) as being a bit like a goblin with a big stick. This horrible little monster will chase you around the house before trying to hit you with the stick, it can do you some harm but in some ways there is something worse. For alpha imagine a big bath filled with boiling hot jam, while the bath might not be able to chase you, if you fall in then you are going to get a far worse injury. The alpha is very short ranged but if it does get you then it can go a lot more harm than the beta or gamma.

The super mobile alpha emitters are like a evil goblin armed with a steel bucket of boiling hot jam, this evil goblin is also equipped with running shoes or roller blades so it is able to chase you before throwing the boiling hot jam on you. In short this ones combine the some of worst features of alpha and the more long ranged nasties. The only way to stay safe from this wicked goblin is to lock all the windows and doors of the house and keep him sealed outside, with some luck he will die of old age (become weaker when he decays away) before you have to go outside to mow the grass.

OK time to return from analogyland back to reality

With these mobile alpha emitters special extra precautions are needed to keep them contained, for example with polonium-210 some people have been known to put a glove box inside another glove box to increase the thickness of plastic through which the polonium needs to diffuse. Also for radon-222 some people trap the radon on an absorbent material rather than allow it to wander freely around their glove box.

I feel that many members of the general public have a great misunderstanding of what it is like to work with radioactivity.

I have heard of radiochemists being asked “do you glow in the dark”, the short answer is “no”. While the long answer is that is close to impossible to get sufficient contamination on you to make you glow, the only creditable cases I have heard are of some of the radium dial painters who painted their bodies with the radium based glow in the dark paint.

A paper on the legal battle for compensation can be seen here.

I think that the worst aspect of the radium dial industry was the fact that many workers would lick their brush to get a better shape tip. If you look at this document you will see that radium-228 may have been the real villain rather than radium-226. I hold that the pre 1926 two radium dial painting industry could well be the worst part of the radioactivity sector. It is interesting that it appears that only 20 % of the radium which is taken orally is retained in the human body.

Also according to Norris et. al. as cited in this report the human body is quite good at eliminating radium from its self. Some years ago in America as part of a crazy attempt at curing mental patients some people at Elgin state hospital were injected with radium. Using the data from these medical treatments it was possible in the 1950s to work out a mathematical model for the retention of radium in a human. I have rearranged this equation and used a standard bit of maths which allowed me to calculate a biological half life for radium of only 1.33 days.

This value is rather shocking to me, as a chemist I have always been taught and held the view that radium, strontium and lead are calcium mimics which have very long biological half lives because they become part of the bones. I suspect that if radium is injected or swallowed that only part of the radium which enters the blood stream will end up in the bones. While the biological half life of the radium in the bones may be very long, the biological half life of the radium in other parts of the body will be much shorter.

As a result the half life will appear to change if you consider the whole body after a single intake of radium, I suspected that the biological half life will appear to become longer with increasing time after the intake of the radium. Reading more of the report I found that Norris in 1955 published a mathematical equation which predicts how radium is slowly lost from a human. An article in Nature (March 1969, 221, 1059) suggests that the biological half life for radium in humans (long after the intake) is between 10 and 36 years.

The review of radium in humans points out that Dudley in the 1960s suggested an experiment using short lived radiotracers, the experiment was done using humans and it was found that only 20 % of the radium in a mock dial paint was absorbed when it was taken by mouth while only 0.02 % of the thorium in the dial paint was absorbed.

Another interesting point from the review is the fact that if radium-226 sulfate is deposited in the lungs then 25 % of the radon formed can be exhaled, while if radium-226 is deposited in the bones of a person then 60 to 70 % of the radon can be exhaled. This is an interesting difference, which I suspect is due to the difference in the mobility of radon in bone tissue and radium/barium sulfate. I may well get back to this point later.

Update on your new best friend

Dear Reader,

Slightly more than one year ago I wrote about the new best friend of the Japanese people. Rather than a person who will go out and go for a karaoke session with you, drink beer with you or go for a walk in the park with you this new friend is one who can clean up your drinking water and keep your fruit and veg safe. Also this friend can help keep the milk healthy. Now you might ask what sort of super nice person can do all these things, or what sort of imp or kappa is able to do all these things.

The identity of this new friend is a bit more humble sounding, it is the clay in the soil. I have seen a recent paper by Naofumi Kozai, Toshihiko Ohnuki, Makoto Arisaka, Masayuki Watanabe, Fuminori Sakamoto, Shinya Yamasaki and Mingyu Jiang (Journal of Nuclear Science and Technology, 2012, 49(5), pages 473 to 478) in which the cesium behaviour in the soil is reported.

In this paper the soil was examined with X-ray diffraction. This found smectite, mica, hornblende, kaolinite, quartz, orthoclose, cistobalite, feldspar, stishovite, gibbsite, sodalite, olivine and sorosilicate minerals in the soils.

The smectite clay is rather similar to the illite clay which I showed a picture of recently. The two clays are related, I have seen a thesis which explains how the smectite clay transforms into illite clay. For your information the thesis is here. The difference between these two layered clays is in the anionic bread layers between the potassium jam. The smectite and the illite have slightly different layers.

A smectite clay, the oxygens are in orange red, the potassium ions in blue, the aluminium/silicon atoms are in sea green. Note that layers of potassium ions which look like slices of bread.

I think that both the smectite and illite are formed from mica, so I would say that the more mica in the rocks which formed the soil the better when you are considering cesium in soil. The mica is very similar to the two clays, again it is a layered solid.

Many of us know mica, it is a mineral which can be made into thin sheets. We will soon see why it is possible to split mica into thin sheets. It is easy to separate the mica by peeling apart the layers.

Here is a view of a mica (Muscovite) which was studied some time ago. (O.V. Sidorenko, B.B. Zvyagin and S.V. Soboleva, Kristallografiya, 1975, 20, 543-549). Should should see again that the solid is layered, the potassiums (blue) have anionic layers of alumo-magnesium silicate between them. I have shown all the non oxygen atoms in the layers as green.

Mica showing the layers of potassium ions between the anionic layers

The important thing about the mica is that the aluminium atoms are randomly mixed with magnesium and silicon atoms in the two layers. The authors of the paper I am working from expressed the view that one of the types of layers (the middle layer in the trilayer anionic layer) has 20 % magnesium and 80 % aluminium. While the two outer layers of the anionic trilayer have 28.4 % aluminium and 71.6 % silicon. The mica also contains some hydroxyl anions which I have been unable to locate in that solid. I have made a new drawing of the mica which shows the mixed aluminium/silicon and aluminium/magnesium layers in different colours to show you how the solid fits together.

Diagram of mica. The potassium ions are in blue. The mixed aluminium/magnesium sites are in grey. The mixed aluminium/silicon sites are in green. The oxygens are in a rather fetching shade of orange.

It is important to note that the green aluminium/silicon sites have a tetrahedral arrangement of oxygen atoms around the central atoms while the grey mixed magnesium/aluminium sites have a distorted octahedral arrangement of oxygens around the central atoms.

The hornblende clay is a very different mineral, I have looked at the crystal structure and it looks in some ways like a SBA-15 or MCM-41 to me. It has tube like holes which pass in one direction through the clay. These tubes are then filled with sodium and potassium cations. As the clay is so different, I suspect that it may behave differently to the layered clays which I showed you.

The mica based minerals can change the spacing between the anionic layers to suit a new cation which has a larger diameter than the potassium. In this way the larger cesium ions can be held in the solid. But in the case of the hornblende, I do not think it will be so easy to add a larger cation. I think that the holes will get plugged up and blocked by the larger cations.

Here is a view of several unit cells of the hornblende clay, the solid is a little disordered. It has a mixture of sodium (yellow) and potassium (blue) cations in the solid. Also note that it has grey calcium ions in the alumosilicate layers. The aluminiums are purple, the silicons are sea green and the iron atoms in the clay are orange. The oxygen is in a rather fetching orange/red as before.

A view of hornblende clay showing the holes in which the potassium/sodium ions go.

I will try and give you an update soon on the clay and the cesium.

Aftonbladet and chernobyl

Dear Reader,

It has come to my attention that a woman called Natalia Kazmierska has seen fit to comment on the Chernobyl event recently. This has made me think about the way in which the general public think about radiation biology.

I doubt if I will be attending a showing of the film “The Chernobyl Diaries”. Frankly I have better things to do  and I think that watching 28 days later gave me all the frights about zombies that I need for the next decade or so. I would like to point out that regarding radiation it is a case that what “everyone knows” is not right. While the general public expect a large number of mutant babies and deformed wildlife (overgrown rats, dogs with snake heads, snakes with dog’s bodies and what ever else you can imagine), I have to disappoint many people and point out that many of these wild (and far fetched mutants) are impossible.

In an adult mammal (and almost all other warm blooded animals) the cells are already differentiated and it is impossible to change an organ by altering a cell as

1. The organ has many cells

2. It is impossible to change the DNA of all the cells in the organ in the same way using radiation.

If we consider the eye as an example, somewhere in your genome is a genetic code which determines your eye colour. If you want to change your eye colour (and you do not want to use fancy contact lenses) then you would need to change the DNA in all the cells which are currently part of the section of the eye which gives the iris its colour. This is a very tall order which I think is currently impossible.

When you were an unborn baby at an early stage there would have been one eye which would have been destined to become your eye, if you had altered the DNA of this cell then you could alter the eye colour. But unless you also changed the cell which was destined to become your naughty bits (opps I mean reproductive organs) then this mutation can not be passed onto the next generation. So it is not possible to mutate adult humans or even human babies (for the purpose of this bit of biology they already have their organs locked in this way).

I know that newspapers would love to be able to report a “real life mutant associate prof who marks his students work using psychic powers to read student’s minds before writing the results down using a biro held using his tentacles”, but I have to tell you that such a story is totally impossible. If you want to print such a thing then I think other than vanity publication or writing in a novel/comic book your only chance would be to write it for the “Sunday sport“. For those of my readers who do not know, the Sunday sport is a comic like news paper which is packed with wild tales about sexual matters, sport, showbiz gossip and plainly silly things such as world war two bomber found on moon, aliens going on drinking binge in a UK pub and a monkey landing an airplane.

I think that the main reason why radiation is so bad at mutating humans (and most animals) is that the likelihood on inducing a mutation in the reproductive organs which can be passed onto your children is only 1 % per sievert (Sv). It is important to distinguish between a mutation which can be passed onto your children and the case of a child which does not develop normally due to irradiation in utero. Most of the horror pictures which people may have shown you are likely to be either fetuses which were deformed for some reason which is unrelated to radiation or a child which developed in an abnormal way due to the action of some agent such as (alcohol or radiation) on the unborn child.

It is important to bear in mind that the chance of inducing cancer in a human (typical adult over 16 or 18) is also low, it is widely accepted as being at 5 % per sievert, as a dose of about 4 sievert delivered over a short time is likely to send a person to the other side (assuming no specialist medical care) it is very hard to mutate a person’s gametes to enable them to have abnormal children let alone children with superpowers.

For example if we consider the associate prof with two superpowers (mind reading) and the tentacles which he can write with then it should be clear to most of my readers that such differences are a long way removed from what is the norm. I imagine that to get either of these “superpowers” would require a long series of mutations, this long series of mutations would require a large number of genetic changes to occur which are very unlikely to occur in the lifetime of one human. A typical mutation which could occur in a human would be a change in a gene which stops a person making a protein or some other biomolecule which is needed for normal life, this would include hemophilia appearing in a family which never had it before.

An alternative would be for the genetic code for the mutant prof to already be common in the human genome but to have a single gene which switches off this weird stuff. We can quickly discount this as if this was the case then every now and then we would see a person born who could read minds and had the extra limbs. As I have never heard of such a human then either the authorities are doing a good job of hushing it all up or more likely it has never occurred. I hold the view that it is very hard to keep something wild and exciting secret for a long time, a secrete organisation is only as strong as the weakest member so it is likely that a secret organisation will within decades become a publicly known one.

So I think we can discount the likelihood of an associate prof who mind reads and can write using extra organs appearing by mutating a “normal” human.

I would like to point out that the nuclear industry is one of the few which has worked out a method for isolating the worst forms of its waste from humans / the environment until it is no longer a threat. Wastes from other sectors will stay nasty and horrible forever. For example asbestos waste will remain hazardous forever and so will heavy metal waste from electrical batteries (NiCd cells). I would like to suggest that Natalia that she should consider this issue.

I would also like to point out that the worst accidents I can think of in the energy sector have been outside the nuclear industry, for example back in the 1960s a spoil heap at a Welsh coal mine slide down a hill and killed almost every last child in a primary school (Aberfan). If society or Natalia wants to have a debate on the safety of the nuclear sector that is fine by me, but we need to consider the whole of the energy sector rather than cherry picking the parts we want to discuss or be opposed to. I will be blogging on this in greater detail in the near future.

Carbon tetrachloride

Dear Reader,

I saw a chemistry world blog article about carbon tetrachloride so now I feel compelled to write to you about an organic solvent from yesteryear, it is carbon tetrachloride or more correctly tetrachloromethane. This is the substance which sent Margo Jones to the other side when her carpet was dry cleaned with it, it also almost sent a friend of mine to the same place years ago. An old chemist who I know used to mouth pipette everything, one day he mouth pipetted solutions of things in carbon tetrachloride (I think he was measuring distribution ratios) and he told that hours later he started to vomit. He told me that he continued to puke for about three days and he suspects that he had a lucky escape (He recovered and then went onto have a productive life).

Top tip of the day : Never mouth pipette anything !

The thing which interests me most about carbon tetrachloride is the free radical chemistry of this molecule. I strongly suspect that the trichloromethyl radical is a very stable radical which contributes to some of the chemistry of carbon tet. I know many years ago both the Soviets and the Americans built PUREX plants using carbon tetrachloride as the diluent. The nice thing about carbon tet is it gives a very good quality uranium and plutonium product, also it is easy to purify the process solvent to recover pure carbon tet, it is non flammable and the phase separation is easy. But it had a horrible sting in its tail, when you irradiate carbon tetrachloride you form chloride anions. I suspect that the solvated electrons are captured by the LUMO of the carbon tetrachloride and then it splits up to form anionic chloride ions and trichloromethyl radicals. The chloride impurity in the PUREX plants quickly formed aqua regia with the nitric acid used in the PUREX process. The resulting corrosion soon caused both plants to be shut down.

I will get onto the free radical chemistry which occurs in flames later, but an interesting bit of free radical chemistry using carbon tetrachloride is used in the production of cypermethrin. This is a insect killing agent which I have bought at Ica and used to kill creepy crawlies in my house. A key step in the production of cypermethrin is the formation of the cyclopropane ring. The synthesis starts with a pericyclic reaction (Claisen rearrangement) which uses an allylic alcohol and triethyl orthoacetate to form γ,δ unsaturated ester. This ester it then reacted with carbon tetrachloride in a free radical reaction. Treatment with two bases then forms the cyclopropane ring which makes up a key part of the carboxylic acid part of the insect killing agent.

Testilying and the environmental movement

Dear Reader,

Twenty years ago or so the late Dennis Evans told me a story about some cops who thought that they would tell a “white lie” to protect society (I have no idea where this vile story occurred or if Dennis had made it up or not). What happened was these boys in blue raided a drug dealer’s hotel room. They find some packets of cocaine. Then to make sure that the man went away for longer they plant some extra packets of cocaine. I imagine that they wanted to make sure that the judge sent the vile coke dealer away for decades rather than just sending him to HMP holidaycamp for a few years.

The core thesis of the prosecution was that the man was a cocaine dealer who was mixing cocaine with sugar to turn a larger profit and that all the packets had come from a common source. The fact that different packets had different sugar levels made it look like the dealer was mixing purer cocaine with sugar to make a less pure grade.

The police’s expert issued a report on on cocaine content of each packet where he/she lumped all the adulterants together. It is a common habit for people in the illegal drug trade to mix illegal drugs with other materials to increase their profit. So it should not be a total shock for the police to have observed some evidence of such behaviour.

Dennis was contracted as an expert witness for the defence, he retested the cocaine and made a point of measuring the different sugars (glucose, fructose, sucrose etc) in the cocaine batches. He found a purer packet which the police claimed was the parent of the less pure cocaine contained a sugar which did not appear in the less pure packets.

Armed with this information the defence was able to prove that the story that the police were telling was false. They showed that someone (the police) had planted at least one packet in the room. They then suggested to the jury that all the cocaine had been planted in the room. The man then was acquitted on all charges and walked away from the court, I imagine without a stain on his vile character.

While some people might think “I have nothing to do with drugs” and “I am not a policeman” so this story has nothing to do with me. I would say that these people are being very foolish, this is a cautionary tale about telling a “white lie” to get the job done. This is an example of testilying and the vile perils it brings.

It is better to tell the truth about something even if you think by exaggerating that you will be more likely to get the outcome that you want.

Before we go any further I would like to make something clear to those of you who are not regulars here on my blog, I have to agree with the greens, antinuclear lobby or whatever you want to call them or be called yourself (if you are a member of the antinuclear lobby) that the Chernobyl and Fukushima events are horrible. These are events which need to be avoided where possible, and if total avoidance is not possible then these types of events need to be mitigated to eliminate the threat to the general public.

My (or your) revulsion at serious nuclear accidents is not however a license to exaggerate or attempt to use these events to score cheap political points. Frankly those who use these events for selfish ends disgust me just as much as the 19^th century mill owners who thought it was quite reasonable to force young children to work in dangerous factories, clean chimneys or go down the coal mine.

My loathing of serious nuclear accidents is one of the reasons why I devote time and energy doing research on trying to prevent a nuclear accident causing harm to the general public. In order to protect ourselves against reactor accidents we need to understand them, part of the quest to understand them involves a quest for truth and an insight. During this quest I am doing my best to share whatever grains of truth I uncover with others, and also to point out silly ideas when I find them. One of the things which irks me is when people exaggerate the consequences of an event, the fact that an event is horrible is not a license to lie. To me the exaggeration of the event is as wrong as a person falsely claiming that it is less bad than it really is.

It has been claimed that the cesium from the Chernobyl accident causes heart disease in adults and children, the core of the idea is that cesium goes into the heart and that the radioactive cesium then damages the heart. Next the person falls down dead from heart disease or at least becomes in invalid.

We need to ask ourselves if the radioactive cesium is able to damage the heart, some time ago (2008) a Yann Gueguen et. al. published a paper (Cardiovascular Toxicology, 2008, 8(1), 33-40) in which they exposed rats to cesium in their drinking water. The amount of cesium was 150 Bq per day for three months. Now the rats weighed 560 grams, which means that they were drinking 267.85 Bq per kilo. Now if we scale this up to a 75 kilo man then he would have drinking 20 kBq per day. As each year has 365.25 days then this 75 kilo ratman will be drinking 7.338 MBq of cesium each year.

We are making the assumption that the cesium behaviour in rats and humans is the same and that the same dose / activity coefficient should be used for both species.

Based on my ALI as a classified radiation worker which is 1.5 MBq of cesium-137 (oral), the rat man will be drinking 4.9 times the ALI which is based on a 20 mSv dose. So the 75 kilo ratman will get a 97.84 mSv dose from the cesium. So this amount of cesium is a very large amount of cesium.

I hold the view that if a member of the general public is getting a 98 mSv dose from an nuclear accident which happened decades ago that something is deeply wrong. This is a dose which is far in excess of what I am allowed to be exposed to at work. So while this study might be an interesting one it is set at a level of cesium which I think is too high.

I suspect that some differences between rats and humans exist, I have checked and the biological half life of cesium in rats is shorter (11 days) than it is in humans (B. Le Gall et. al., Biochimie, 2006, 88(11), 1837-1841). So rats are able to get rid of cesium from their bodies faster than humans can. The estimates for the biological half life of cesium in humans range from about 1 month to 4 months. If we take the UN’s estimate that biological half life to be 100 days then we can compare rats and humans.

I have done some calculations for rats and humans and based on the difference in the biological half life I think that cesium should be 9.1 times less toxic to a rat than it is to a human. So we should revise down out doses for the “rat man”. If we take this correction factor then the rat man used in this experiment if it had been a human would have had a 10.78 mSv dose (0.8 MBq intake)

Now I think a key part of the reasoning behind “chernobyl heart” is the idea that the cesium goes into the heart, I was looking in the literature at animal studies where the experimental animals were fed cesium-137. I found a second paper (Jean-Marc Bertho et. al., Radiation and Environmental Biophysics, 2010, 49(2), 239-248) where mice were contaminated with cesium-137 (20 kBq per litre) in their drinking water.

This paper stated that human exposure to cesium-137 in contaminated areas is in the range 20 to 2100 Bq per day, which works out as giving a worst case amount of 767 kBq per year. While I think that this amount of cesium is a large amount in the general public’s diet it is well below my ALI (Annual Limit of Intake) and far below the level which I worked out by scaling the rat up to the 75 kilo “rat man”.

The mice were feed the cesium in their diet from the age of four weeks onwards, I looked at the intake of the these mice and the females drank 465 Bq per week and the males drank 507 Bq per week. As the female mice (at 20 weeks) had a weight mass of 23 grams and the male mice had a weight mass of 30 grams we can make a first guess of what human level of exposure we are considering.

The 75 kilo “mouseman” would be getting 1.27 MBq per week while a 65 kilo “mousewoman” would be getting 1.31 MBq of cesium per week. This will work out as 66 MBq per year for the mouseman and 68 MBq per year for the mousewoman. This is a lot of radioactivity.

We are assuming here that the biological half life of cesium in mice is the same as it is in humans and that all other cesium biochemistry and biophysics is the same in both species. Again if we work out the biological half life of cesium in mice it works out being shorter than it is in humans. Using the data from J.M. Llobet et. al., Journal of Environmental Contamination and Toxicology, 1998,61, 289-296 it appears that the biological half life in mice is about 7 days. Thus based on the different biological half-lives the cesium will be 14 times less harmful to mice than men.

So micemen will now be getting an intake of 4.7 MBq per year. This is still a lot of cesium-137 to get in your diet.

Now back to the paper of Bertho, the important thing in this paper is that no clear signs of damage to the mice were seen. Also if you read the paper the radioactive cesium content of the heart (in Bq per gram) is less than the kidneys and the normal muscles of the mice. This paper makes me think that we need to take great care when we consider the possible link between chernboyl cesium and heart disease. This is because the cesium does not seem to be localizing inside the heart in the same way as iodine localizes inside the thyroid.

The next thing to be careful of is the fact that cesium-137 (together with its daughter barium-137m) emits three different forms of radiation. The average beta decay energy of cesium-137 is 188 keV, this is quite a low average beta energy when compared with yttrium-90 (933 keV) and phosphorus-32 (695 keV) but it is about the same as Sr-90 (196 keV). But it is a bit higher than carbon-14 (49 keV). So we can safely assume that some of the beta energy of the cesium which is in the heart will be deposited in the heart.

But 662 keV of the decay energy of the cesium will be in the form of gamma rays, even if the cesium is in the heart then much of this energy will escape from the heart. On average 363 keV of energy will fly away in the form of neutrinos. These are particles which are unlikely to interact with a slab of lead as think as the earth. So I think we are safe to assume that only part of the decay energy of the cesium which is in the heart will be delivered to the heart tissue.

Also bear in mind that the beta and gamma radiation are both low LET (Linear Energy Transfer) radiations. This means that ionization tracks formed by these radiations are long and diffuse, as a result these radiations are less able to damage living tissues. The issue of self repair needs to be considered, the background of radioactivity in a normal human body together with cosmic rays causes all tissue to be subject to ionizing events. The damage from most of these are repaired by the cells.

I think it would be a good idea if those who are making statements supporting the idea that cesium-137 causes cardiac damage to people should address the issues of how much cesium is in the heart and how much of the radioactive decay energy of the cesium is delivered to the heart.

Also they should consider the natural radioactivity (carbon-14 and potassium-40) which is in a normal clean and uncontaminated human body.

Well that is all for now, I will return with more of my thoughts later.