More on the subject of clay and cesium

Dear Reader,

It has come to my attention that only a small fraction of the debris created by the tidal wave in Japan has been disposed of. A report from Japan indicates that only 6 % of the waste has been disposed of, part of the problem it that due to concerns that the debris is radioactive the disposal actions (land filling and incineration) has not been done.

I hold the view that the national government in Japan needs to devise a safe, environmentally acceptable and cheap plan for dealing with the waste. Then it should impose the solution using national law, my worry is that if consent needs to be obtained from each municipality then it is likely that nothing will ever happen. If the Japanese do nothing then after 300 years the waste will be almost totally non radioactive (regardless of the radioactivity in it today) but I do not think that they can wait 300 years for the problem to go away on its own.

I think that the debris should be sorted according to its radioactivity, the debris below 400 Bq per kilo should be treated as non radioactive waste. I hold the view that if the waste is slightly over 400 Bq per kilo but bulk of the additional radioactivity is due to short lived radioisotopes then the waste should be either be allowed to stand for some time before being burnt in a normal incineration plant or it should be land filled.

I think that the contaminated top soil from schools, residential areas and commercial areas (shopping areas) is an important thing to deal with. While in the ideal world it would be best if this decontamination waste was either made to vanish into thin air by a magic genie but in the world we are stuck with someone needs to do something with the soil. While a good quality hazardous waste landfill would be the best place to put contaminated soil, I think that for low level beta active decontamination waste it is better to put it in an ordinary landfill rather than leaving this waste at the site it was dug up from.

If the waste is a lot more than 400 Bq per kilo then it needs to be managed as radioactive waste. One option is to land fill it. The land fill must be equipped with a barrier layer to prevent the radioactivity leaking out of the landfill. If it is cesium then one of the best barrier layers is clay. The cesium will bind to clay, I have found in the literature a crystal structure of a cesium exchanged clay. (D. Gournis, A. Lappas, M. A. Karakassides, D. Többens and A. Moukarika, Phys. Chem. Minerals, 2008, 35, 49-58).

The clay is a layered solid, it has an set of anionic layers of aluminium, oxygen and silicon. These layers are like slices of bread, and the cationic cesium ions go between the slices of “bread” to form layers. I think that the strong binding of clay to cesium will slow the movement of cesium in the barrier layer so that the cesium will decay by the time it escapes from the landfill.

Here is a picture of the clay with the cesium in it. Aluminium is green, oxygen is orange, silicon is purple and the cesium is blue.

 

The clay with cesium cations in it.

 

If the waste is very radioactive then it may be best to put it into drums, add some cement to make the waste into a hard block (less dust and no chance of a liquid spill). The steel drum will then improve the safety of the transport of the waste to the landfill and it will give some decades of additional containment. If the waste is only cesium-137 then assuming that we choose the right drum then it could last for several half lives. A carbon steel is normally passive if it is in contact with cement so we will not get much corrosion on the inside of the drums. If the outside of the drums are painted or better still galvenised then the drums will be very long lasting.

Now whatever the extreme greens say what you need to do is to isolate the waste from humans for a finite time, they hard part is making a choice of how low the threat has to be at the time when you lose the ability to contain the waste. Once the experts work out how much much activity the dump can release per day without breaching the limit then we can work out a design for the land fill.

For example if our release limit is 1 kBq per day and we know that the dump will release 1 % of its contents per year after the barrier has failed. Then if the dump starts with 1 GBq of activity then we can work out how long the dump must contain the waste.

1 kBq per day works out as 365.25 kBq per year.

So if the dump must not start to leak until the total activity is 36525 KBq (or 36.525 MBq).

So the waste must decay by a factor of 27.379 before it starts to leak.

As A = Ao exp -λt

We can work of how long t has to be, if the half life is 1 year, then λ will be 0.693 year^-1

exp -λt must be equal to 0.03652 at the time when leaking can start.

So we start with

exp -λt = 0.03652

-λt = ln (0.03652)

-t = ln (0.03652) / λ

t = ln (0.03652) / -λ = -3.3098 / (-1 x 0.693 year ^-1)

t = -3.3098 / – 0.693 year ^-1 = 4.77 years

So if we can build a waste store which will not leak for five years then we can be sure that not release too much radioactivity per day. I choose a half life of one year to make the maths easy but the same ideas can be used with real waste dumps.

Radiation and your heart

Dear Reader

Well a lot has been written about cardiac damage and radiation, I keep seeing the claim that the Fukushima / chernobyl fallout is giving people heart attacks. I would like to point out that the best evidence I have seen for cardiac damage was in a very special group.

It was women who have been treated with radiation for breast cancer (See Paul McGale et. al. in Radiotherapy and Oncology, 2011, 100(2), 167-175). While Women treated in the left breast have in the past sometimes suffered some cardiac damage while those treated for cancer in the right breast do not get damaged hearts. In the paper I cited the women with left hand breast cancer were getting doses of about 6 Gy while the women with cancer in the right hand breast were getting cardiac doses of about 3 Gy.

This paper suggests to me that the heart can tolerate doses in the 1 Gy range, I think it is impossible for a member of the public in Japan to either get a 1 Gy dose in a year from external gamma rays from the Fukushima event or from internal exposure to cesium.

As a result I think that the cesium radioactivity from the Fukushima event does not pose a threat to the cardiac health of the Japanese population. I think that many of the claims which are made in Japan and the former Soviet union that radioactive cesium is killing people’s hearts are deeply wrong.

While the stress of a nuclear accident might increase the rate of heart attacks and the dire social conditions / diet in some parts of the Ukraine might lead to heart disease I think that rushing to blame every ill on Chernobyl or Fukushima is deeply wrong. It is a childish and stupid response to what is a very real problem which will either do no good or it will do a lot of harm.

One worry is the “worried well” who will divert scant resources away from where they are needed.

Another worry I have is that people will take a view that they are already doomed so then they no longer care about their wellbeing. The UN have made a statement which included some answers to long running and important questions. Which included.

“Q: Did the trauma of rapid relocation cause persistent psychological or mental health problems?

A: Stress symptoms, depression, anxiety and medically unexplained physical symptoms have been reported, including self-perceived poor health. The designation of the affected population as “victims” rather than “survivors” has led them to perceive themselves as helpless, weak and lacking control over their future. This, in turn, has led either to over cautious behavior and exaggerated health concerns, or to reckless conduct, such as consumption of mushrooms, berries and game from areas still designated as highly contaminated, overuse of alcohol and tobacco, and unprotected promiscuous sexual activity.”

My understanding is that if you put a population under dire stress, imagine that me and my friends had been shipped off to deal with the Fukushima then if the stress was not managed then a series of mental health effects might occur as a result of the intense stress.

Person A might turn to drink, by picking up the bottle. He might use the booze to blot out what he perceives as the horrible reality. Ten years later he becomes a drink driver and then he runs down a little old lady / young mum plus pram / a whole line of nuns / (insert some other shock horror outcome for a drunk driver).

Person B might start to smoke again after having abstained from smoking for decades. Now if he assumes he will get lung cancer from radioactive dust he might think what is the harm in having a smoke.

Person C might find solace during the event by having sex with person D. I expect that when C’s wife and D’s husband discover this then C will end up being thrown out of the house by his wife. This wild filng of C and D will be likely to lead to a series of divorces which is a form of social harm.

Person E might start to over eat as a result of the stress of the event, he might even get a taste for puffer fish and then falls down dead when one day in his stressed out state he prepares the fish in the wrong way.

I would like to point out that sometimes a moment of intense stress does have a good effect in a person, for example one lady I know did “see the light”, find religion and she then put her life in order. She has told me that as a result of seeing the light she is a happier person who has a better quality of life. So perhaps person F who had been a heavy drinking nihilistic womanizer might after a week in the highly radioactive environment reexamines his life and then become a good man and a piller of his society. He might then become a priest / monk / good husband / (insert some other good type of man) and then make a positive contribution to society.

This is a good blog entry on risk which you might want to read.

The big earthquake one year on

Dear Reader,

We are coming up to the first anniversary of the Fukushima accident which was provoked by a big earthquake. Now as ever it is important to avoid going to one extreme or another. When we get sick a spoon full of medicine might make us feel better but that fact is not a license to drink the whole bottle in one go !

While I am very strongly in favour of improving safety standards in the nuclear industry and I am sure that some important lessons can be learnt from the Fukushima event, but we should not close down the whole nuclear industry just because of this accident. I always do point out that the burning of coal does release a vast amount of radioactivity into the air.

The majority of radioisotopes from nuclear power plants are short lived beta emitters which tend to go away quickly, the radioactivity in coal tends to be long lived alpha activity. As the alpha emitters tend to be so much more toxic and as they are long lived this is a nasty menace which people tend to forget about. So do not allow anyone to talk you into switching to coal as a way to close down scary looking nuclear plants.

Now on the subject of radioactivity, it is important to bear in mind that wind farms need neodymium for the magnets. The extraction of this metal often requires it to be extracted from monazite which is a radioactive mineral. So before anyone trys to sell you the idea of clean green wind power as an alternative to nuclear power then ask where the neodymium for the magnets comes from. The great problem with “greenness” is that you need to look at the whole life cycle of the object or the system, you also need to look at where the materials required for a device come from as well as what waste the device forms and how you are going to dispose of the device when it is no longer wanted.

I worry that unless the right degree of care is taken with the ore processing that the extraction of the neodymium will create large amounts of radioactive waste which might not be managed in a safe, environmentally sound or reasonable way.

But lets think for a moment about the radioactivity from the Fukushima accident, in common with chernobyl after the short lived iodines the most important radioisotope is Cs-137. This is a medium to long lived isotope which contributes to much of the dose which members of the public will get in the medium and long term after the accident. I saw a paper in the literature by J. Jandl, J. Novosad, J. Francová and H. Procházka, Veterniarni Medicina (Praha), 1989, 34(8), 485 to 490 which is on the subject of cesium removal from deer meat. What these Czech workers did was to pickle meat, by ion exchange the cesium came out of the meat and was lost into the pickling liquid. As only the meat and not the pickling liquid is consumed by humans this offers a method for the decontamination of meat.

The same idea has been written about by some Germans (R. Wahl and E. Kallee) in Nature, 1986, 323, 208. These workers reported that after five days 95 % of the cesium had been lost from the meat. They also reported that the meat tasted very good. So based on this work I would like to suggest that we should consider treating some foods after gathering them to lower their radioactivity content and thus make them fit for human consumption.

Depressing film

Dear Reader,

Me and my wife have been watching some disaster films recently, last night we choose to watch “On the Beach” which is a ‘oh so not so joyous film‘ about the end of the human race. The human race is snuffed in the film (and in the novel) out by very intense fallout from a nuclear war.

This made me think about it for a moment, several things were wrong with the physics and the chemistry of the film.

1. The fallout takes many weeks to arrive in Auz, looking at a paper on bomb fallout by some workers from Kyoto, Kanazawa and Hiroshima Universities it is clear that the fallout will be more than 200 times less radioactive gram for gram after ten days than it would have been 2 hours after it was deposited as ‘heavy’ local fallout very close to the bomb detonation.

So by the time that the fallout would have got down under it would have lost much of its strength. In the book on the beach it took much more than ten days for the fallout to arrive in Auz. This means that the reduction in the radioactivity due to simple decay would be even larger.

I had taken a very simple view that no chemical separation would have occurred during the transport of the radioactivity from the bomb detonation to Auz.

2. Around about 10 to 100 days after detonation the majority of the gamma dose will be due to Te-132/I-132, Ba-140 / La-140, Zr-95 / Nb-95, Ru-103 and I-131. While the iodine (I) and tellurium (Te) are very mobile the barium (Ba) and zirconium are less mobile. A good rule of thumb is that the chemical form of an isotope twenty seconds after the detonation will determine how the isotope behaves.

100 % of the zirconium-95 will be in the form of yttrium-95 (half life ten minutes) at twenty seconds after detonation. The yttrium is very non volatile and is likely to be in the form of an solid oxide at that point. I suspect that it will be very likely to become part of the larger particles from things like soil which will fall to earth more quickly. As a result the local fallout close to the bomb will be enriched in zirconium-95 while the distant fallout will have less of this isotope.

The barium-140 will be formed from cesium-140 (half life one minute) which will be the form of this isobar twenty seconds after the detonation. The cesium is only a semi volatile so about 30 % will be in a solid form.

The ruthenium-103 (Ru) is formed by the decay of molybedum-103 (Mo), as the Mo-103 has a half life of seventy seconds it will dictate much of the behaviour of the Ru-103.  The boiling point of MoO3 is about 1160 oC which is lower than that of ZrO2 and Y2O3 (both about 4300 oC) and higher than what I would expect for of Cs2O. So as a result I much of the ruthenium-103 to be lost into solid particles. So the enrichment process may tend to deposit it in the local fallout.

Now according to the graphs published by Japanese workers if all the involatile forms of the radioisotopes are lost from the fallout then the dose absorbed over the ten to one hundred days the will be only three quarters of the dose which would have been suffered if no chemical fractionation had occurred.

Both of these effects would tend to protect the population down under by lowering their dose, I hold the view that a nuclear war would be a horrible event. But I do not think that a total extermination of mankind by fallout would be a certainty.

Cesium and heart disease

Dear Reader,

It has come to my attention that a hot debate was erupted involving anti-contamination pills and radioisotope tests being offered for use in Japan. You can read some of this story on the guardian’s web site.

Here are my thoughts on the matter.

It is claimed that cesium will cause cardiac damage in children. I would like to consider the physics and chemistry of this for a moment.

1. The physics,

Cesium-137 is a beta emitter with a decay energy of 1176 keV. I emits electrons with an average energy of 174 keV (max energy of 514 keV). So I assume that about 340 keV of the energy will be lost when the neutrino flys away. As neutrinos fly through thick lead sheets they will not interact with human tissue.

Of each decay 662 keV is lost when the excited barium (^137mBa) de-excites by emitting a 662 keV photon. Most of these photons will be able to escape from the heart which leaves typically only the short ranged beta behind. This beta has an average energy of 174 keV per decay. This energy is part way between the low energy beta of ¹⁴C which does not pass very far into a human body (typically very few beta particles would pass through a glass jam jar) and the high energy beta of ³²P which needs thick plastic blocks to stop the radiation. So I would expect only a small fraction of energy to be deposited in the heart even if the heart absorbed all the cesium in the human body. So cesium-137 is not likely to be a radioisotope which can selective give the heart a radiation dose. If the cesium is able to damage the heart then I would also expect to see some effects in the lungs and other parts of the body.

2. The chemistry

At high doses stable cesium can cause heart rhythm abnormalities, it requires an intake of grams per day to do this. I doubt if anyone in Japan has had such a large uptake of cesium from the Fukushima accident as one which would cause the same chemical effects as have been seen in people who have swallowed large amounts of cesium salts in an attempt to cure their cancers.

The fission yields of the cesium isotopes made in a reactor is listed below in this table. I have used data for ²³⁵U with thermal neutrons for the table.

Cesium isotope	Fission yield
133 (stable)	0.06702
134 (2.06 year half life)	Zero
135 (2300000 year half life)	0.06533
136 (13 days)	Zero
137 (30 years)	0.06286

Now if we make things simple by ignoring the activation of ¹³³Cs to form ¹³⁴Cs we can make a simple estimate of the radioactivity of a gram of fission product cesium. A gram of reactor cesium will be roughly 33 % (w/w) cesium-137.

As the activity is given by the equation

A = Nλ = λmN_a/ (atomic mass)

As the half life of cesium-137 is 946728000 seconds, then the decay constant (λ) will be 7,322 x 10^-10 s^-1, and as N_a (number of atoms in a mole) is 6.02214179 × 10²³ then we can estimate the radioactivity per gram of fission cesium.

A = 7.322 x 10^-10  s^-1 x 0.333 g x 6.02214179 × 10²³ atoms mole^-1/ 137 g mole^-1 = 1.07 TBq

Now I have to tell you that 1.07 TBq of Cs-137 is a lot of radioactivity, in old units this is about 29 curies. Now when I go to ye olde manual of all things radioactive (the 1966 radiochemical manual published in the UK) it states that at one meter from 1 curie of cesium-137 the dose rate will be 0.32 rads per hour.

Now if we were to stay at one meter from 29 curies of cesium-137 then in one hour we would get a very noticeable dose of 9.3 rads per hour. This in modern units would work out as 93 mGy per hour. In one week a person walking around with a whole gram of reactor cesium one meter from their body would get a dose of 16 grays (likely to be a fatal case of ARS). Now as it takes a daily dose of about grams of cesium to cause heart problems, so I think that it will be impossible to reach this level of chemical contamination without dropping dead of the normal acute radiation illness. So far in Japan there have been no reports of anyone displaying the symptoms of ARS, not even in the team of people who were working on the reactors during the worst parts of the accident.

So I think it is safe to rule out heart disease induced by a normal chemical toxicity of the cesium from the Chernobyl or Fukushima. What those who claim that radioactive cesium damages the hearts of children need to do is to show a different mechanism to show how this cesium damages the hearts of children.

I have seen a paper in which it proves that an acute or semi-acute large dose of gamma rays (circa 5 gray) can induce heart disease in women, I suspect that the exposure level of both workers and members of the general public in Japan is far too low to see these effects. The limit for gamma rays for children in Japan has been set at milligrays per year. I also hold the view that if I was to get a moderate dose to my heart each year (how about 500 mGy) that the self repair processes would fix all the damage and that my heart would remain healthy. I may write another day more about gamma rays and heart disease.

My thoughts on the claims that cesium-137 has caused heart trouble in people is that a degree of common sense is needed, if you are shown data from the Ukraine then always ask if poor diet and other social conditions which relate to the fall of the soviet union have been taken into account. While a possible link between radiation and heart disease in nuclear workers has been reported by some workers, the link between low levels of radiation and heart disease has not been clearly shown to exist. The typical health effect seen in radiation workers who have been over exposed at work is cancer and not heart disease. I think that it be better to looking at the relationship between cancer and low levels of radiation.

Cesium and cardiac effects

Dear Reader,

I am aware that some people from the antinuclear lobby have started to ask the question of “does radioactive cesium damage the heart ?”. I hold the view that in science a question which is testable is a good thing to have. I hold the view that a true scientist tests a hypothesis (fancy term for a theory) in an experiment using a research question.

To my mind the research question which these people who are opposed to nuclear power have raised up is “Does radioactive cesium damage the heart ?”. This is an interesting question but I must warn my readers that very little has been written on the subject. It has been shown in goats by M. Kaikkonen et. al. (Acta Physiologica Scandinavica, 2005, volume 183, pages 321-332) that cesium tends to concentrate in the kidneys (x 50 plasma concentration), urine (x 5 to 28 plasma concentration), salivary gland (x 11 plasma concentration), cardiac muscle (x 7 plasma concentration) and small intestine (x 6 plasma concentration). The fact that the cesium concentration in the urine / kidney is higher than it is in the plasma of the animal suggests that the goats will lose a lot of the free cesium in them via the urine and that it might be a better idea to look for kidney damage in humans who have been exposed to radioactive cesium.

I hold the view that anyone who wants to prove that radioactive cesium damages the heart needs to do the following.

1. Prove that Cs-137 (or Cs-134) in the diet of animals causes some harmful change to the heart, use two groups of animals one fed radioactive cesium and the other group fed no radioactive cesium.

2. Prove that the effect of the radioactive cesium is not due to a toxic effect exerted by normal stable cesium. I know that a sudden change in the plasma concentration of potassium will cause a heart attack in humans. Part of the lethal injection which the americans use to kill convicts is an injection of potassium chloride. So as potassium cations have an effect we can not rule out that cesium will have an effect.

3. Prove that the effects of internal exposure to radioactive cesium is more harmful to the hearts of the experimental animals than external exposure to the gamma rays from cesium-137. I am sure that at very high doses of external gamma rays that it is possible to damage the heart (or any other organ for that matter).

But lets think about point two for a moment, stable cesium has been used for some time in some alternative cancer treatments. Petr Melnikov and Lourdes Zélia Zanoni have written a review paper on the subject of the toxic effects of stable cesium. This paper had the title “Clinical Effects of Cesium Intake” and was published in Biological Trace Element Research (2010, volume 135, pages 1 to 9). The authors of the paper state that cesium salts do not cure cancer, they also do warn that large amounts of (nonradioactive) cesium salts do cause the heart to behave in an abnormal way. I would like to suggest that anyone considering treating themselves for radioactive cesium contamination should not try to flush the radioactive cesium out of them with stable cesium, instead I would suggest that you use prussian blue to greatly increase the rate at which cesium is lost from the gut.

A friend of mine used to work on cesium in farmyard animals, the work done years ago indicates that small doses of cesium in the diet do not work well as a means of flushing out the cesium from pigs. So if it fails to work on pigs then the use of stable cesium in humans is unlikely to work.

Hot particles

Dear Reader,

I have been thinking about hot particles, these were the irksome little specs of radioactive stuff which were released by theChernobylaccident. When one of my readers (My brother) asked me if the ruthenium would enter the metabolism of humans it made me think.

I have come to the conclusion that some of the particles may be hard to digest, as a result it may well be hard to liberate the ruthenium from the particles. Now if you are getting very happy and complacent thinking that if the particles can not be digested then the radioactivity does not pose a threat to the public then think again.

With non radioactive toxic metals if they are in insoluble forms then they tend to be less toxic, this is because the dust will not dissolve in your lungs and thus poison you. Instead you hope that the dust will be slowly lost out of the lungs by the mini-oars which sweep dust out of your lungs.

The dust then passes up into your mouth and then is swallowed together with the mucus; it then passes into the digestive system. If the dust is insoluble in the gastric juices (I assume that if it survives the gastric juices then it will survive the more alkaline environment in the gut) then it will then pass out the other end of you in the poo.

A more soluble metal containing dust such as cadmium oxide or aerosol such as droplets of chromate will either dissolve in the lungs or the digestive system thus giving you a dose of metals.

It is important to note that cigarette smoke contains cadmium oxide particles, if I recall correctly metal foundry workers who are exposed to cadmium fumes tend to suffer from more lung cancer than the general population. This cadmium in cigarette smoke is yet another reason to either not smoke in the first place or to give up the vile habit.

But I guess you did not come here to be reminded of the evils of smoking so back to the topic of interest.

In the case of radioactive particles (and asbestos) the dust is able to exert a malign influence on your lungs without needing to dissolve. The radioactive hot particles emit radiation which damages the lung tissue as long as the particles are in the lungs, if the particles are soluble then they tend to dissolve. The soluble radioactive metals then enter the rest of the body; with some luck the body will then excrete the metals in either urine or poo. So the body is more able to dispose of the metals.

In the case of the insoluble dusts if they are of the wrong particle size then they can be very hard to clear out of the lungs, as a result they can stay in the lungs for years still exerting their malign influence. The worst offender would be an insoluble actinide oxide such as plutonium dioxide; this could sit in the lungs and carry on delivering alpha particles to your cells for many years.

Uranium is likely not to be quite so troublesome, when a DU bullet is used to shoot a tank it tends to ignite on impact which forms uranium oxides. I have been told that one of the signs to look for when trying to tell if a tank was taken out by a DU bullet is a yellow stain around the bullet hole. Many uranium(VI) compounds are yellow or orange in colour.

If uranium metal is burnt in air, I think it is likely to form U₃O₈ this can be regarded as a mixed U(IV)/U(VI) oxide. A crude way of thinking of it is as UO₃.UO₃.UO₂, it so happens that uranium(VI) oxide dissolves very well in water which contains carbonates. As it so happens that the human body generates carbon dioxide (which forms carbonates when it dissolves in water) then it is likely that uranium(VI) will be soluble in many body fluids as the anionic carbonate complex [UO₂(CO₃)₃]^4-, as a result I suspect that small uranium oxide particles will slowly dissolve if they enter a human. While the plutonium dioxide particles will be likely to never dissolve.

It is also important to bear in mind that the surface of uranium dioxide reacts with the oxygen of the air to form uranium trioxide; this process should help speed up the dissolving of uranium oxide if it is left out in the rain.

If you want to read more about radioactive particles then see F.J. Sandalls, M.G. Segal and N. Victorova, Journal of Environmental Radioactivity, 1993, volume 18, pages 5-22.

Silver and tellurium at Fukushima

Dear Reader,

I have been a little quiet recently as I have had a bit of writers block. I was not sure quite what you wanted to read, life would be better if my loyal readers would write in and say what they want to read more about but today my thoughts wandered onto the subject of silver chemistry.

Those of you who have been paying close attention to the Fukushima event will recall that some radioactive silver has been released by the accident, but to date no ruthenium has been released by the accident.

The boiling point of silver is about 2200 ^oC, while ruthenium metal has a melting point of about 4200 ^oC. As a result of this difference in a reducing environment the silver will boil out of the reactor and form aerosol particles at a much lower temperature than the ruthenium. But under oxidizing conditions (if air gets to the hot fuel) the ruthenium metal will be converted to ruthenium tetroxide (RuO₄) which is very volatile. It will enter the air even at room temperature.

What the RuO₄ will do is to coat the surfaces of dust particles which are formed from things like steel to form ruthenium rich hot particles which will then escape from the plant. The silver can not form a volatile oxide, above about 300 ^oC silver oxide will decompose to oxygen and silver metal.

These facts which we have from the radioisotope signature suggest to me that the fuel was at least 2200 ^oC but it was not exposed to air while it was hot. If we look at page 18 of the following set of slides, then you will see an Ellingham diagram which explains how tellurium is more noble than uranium. The lower down the diagram the more able an element is to react with oxygen, if the line for an oxide is higher than the yellow line for uranium dioxide then the element is likely to be in the zero valent state (elemental form).

Tellurium dioxide has a boiling point of 1245 °C, while tellurium has a boiling point of 988 °C. If the tellurium is in the form of the element then it will be able to diffuse and boil out of the fuel at a relatively low temperature. A paper was written by S.G. Prussin, D.R. Olander, W.K. Lau  and L. Hansson, Journal of Nuclear Materials, 1988, volume 154, pages 25 to 37 which is all about how the tellurium, iodine and other fission products can diffuse out of hot fuel.

Swearing french man

Dear Reader,

Here is a film by a foul mouthed man (he swears way too much).

I am not sure exactly what is motivating the person, he has put up a film of a man with a french accent who is angry about the Fukushima accident.

1. The person is upset about some workers getting doses in the range of 600 to 700 mSv. Now I hold the view that these doses are high when compared with normal occupational doses. Under the Swedish rules these doses represent 30 to 35 years of exposure at the highest normal occupational exposure limits (20 mSv per year). But the good news is that these doses are too low to cause the short term effects which the general public know as “radiation sickness”.

2. The man is upset about strontium appearing in ground water, I hold the view that the appearance of strontium in the from under the reactor building is bad. But the man is upset that an acceptable level of strontium in drinking water exists. The problem is that many things can be measured at levels at which they cause no ill effect or are very unlikely to cause an ill effect.

Let me give you an example, alcohol. We all know that trying to drive a car when you have alcohol in your body is a very bad idea. Drunken driving leads to all manner of adverse outcomes, the great problem is that normal people drink alcohol and then think that they can drive better than Jackie Stewart, Stirling Moss or some other star of motor racing.

In fact these people after drinking are often driving worse than Mr Bean. As a result all manner of horrible accidents tend to occur when drivers have been drinking. Quite wisely governments from around the world have set laws which are designed to curb this vile menace. One part of this legal response are the limits for alcohol in blood which define who is sober and who is not. Here we have a series of limits, now if you sniff the bar maid’s apron you will get a tiny amount of alcohol in your body.

Imagine that we made a new super high tech blood alcohol meter which can measure even the smallest trace of alcohol. Now we take the man who sniffed the barmaid’s apron, and then we find he has a tiny trace of alcohol in him. Even if we can now measure it, it does not mean that he is now condemned to have a drunken car wreck or that you should go to jail for drinking and driving. All that it means is that we have a limit of detection which is lower than the legal limit. In the same way for radioactivity in drinking water it is possible to measure very low levels which are smaller than the legal limit. Just because we can detect it, does not mean that it is a threat.

3. The man needs to clean out his mouth and stop swearing. I can suggest several cures for people who swear too much.

4. He is right that strontium can accumulate in bone and cause serious diseases. This accumulation in bone is likely to be the reason behind the fact that the exposure limits for strontium are so much lower than many other beta emitters. If you look at the data for cesium-137 (beta/gamma) then you will find that the annual limits are much higher. This is because cesium does not stay in the body nearly as long as strontium does. Also strontium goes into one of the more sensitive parts of the body.

5. The discovery of strontium in the ground water under the reactor is a very different matter to the discovery of strontium in the drinking water supply. If strontium does appear in the drinking water system then it can be removed, if the drinking water was to be passed through a zeolite water softener then much of the strontium would be removed at the same time as the calcium is removed from the water.

6. The man is getting upset about plutonium, I would like to point out that the accident in Japan has released very little plutonium. The cesium and iodine released by the accident are far greater threats to the general public than the plutonium is.

7. The man seems to be making some jokes which are in very poor taste about radioactivity in the environment. He also seems to have a problem with the IAEA ! Making threats to force feed people radioactive water is the height of bad taste.

Gamma spectrum of Fukushima soil

Dear Reader,

In case you want to look at a gamma spectrum for the soil from about 20 km from the Fukushima site then I suggest you look at the paper published by Keiko Tagami, Shigeo Uchida, Yukio Uchihori, Nobuyoshi Ishii, Hisashi Kitamura and Yoshiyuki Shirakawa, Science of the Total Environment, 2011, volume 409, pages 4885 to 4888.

The paper concludes that the only isotopes released from the plant were noble gases and volatile elements such as I, Te and Cs. The isotopes detected in large amounts were I-131, Te-129m, Cs-134, Cs-136 and Cs-137. Very small traces of Nb-95, Ag-110m and La-140 were detected but these levels were too low for measurement.

No Zr-95, Ru-103 or Ru-106 was detected which suggests that it is very unlikely that a large scale release of plutonium has occurred. If anyone suggests to you that plutonium has been released in large amounts then bear in mind that Zr-95 is a good mimic for plutonium in nuclear fuel. It forms a dioxide and a Perovskite SrZrO3 both of which are very similar to the plutonium dioxide in their boiling points and water solubilities. If a large scale plutonium release was to occur from a nuclear power plant accident then I would expect zirconium-95 to be found in the same places as the plutonium. The zirconium-95 is much more easy to find as it is a strong gamma emitter while plutonium is only a weak gamma emitter.