Radioactive drone delivery

Dear Reader,

It has come to my attention that someone has been flying a drone in Japan with a radioactive sample on it, the fact that it contains both Cs-134 and Cs-137 suggests to me that it might be something from the Fukushima area. Cs-137 is a sure sign of radioactivity being formed from nuclear fission, while the Cs-134 is an isotope which is strongly associated with nuclear reactors. It is not formed by atom bomb detonations. The activity is likely to be low, the news story lacks a few things.

1. The dose rate of 1 microSv hr-1, at what distance was that measured at ?

2. How much activity was in the sample ?

My first guess was that someone has collected some radioactive muck from the environment near to Fukushima, and they are trying to scare people with it. The one microSv per hour is a very small dose rate, it is about the same as the background in many places in Europe (such as Göteborg, Sweden). A later news article suggests that the person who did it has been arrested by the police and that he did it to protest about the energy policy of Japan.

I would also like to point out that did the 1 microSv per hour include the background where the measurement was made ? This is an important question.

I would also like to suggest that if people want to protest against an energy policy (or another thing which takes their fancy) that they do not use radioactivity or objects which appear to be radioactive to scare or intimidate people. I have no idea what the state will do with Yasuo Yamamoto, but I would like him to grow up and have some more respect for radioactivity.

I know that radioactivity is not quite to everyone’s liking, I would be an idiot if I claimed that everyone loves radioactivity, but regardless of how radiophilic (radiation loving) or radiation averse you are it is wrong to contaminate or threaten to contaminate as part of a protest or as a means of disrupting the lives of others. I hold the view that delivering a “radioactive” sample on a drone in an attempt to get a religious, political, or ideological goal is in the same class of behaviour as sending a letter spiked with fake anthrax. Both acts are serious crimes and should earn the offender a trip to jail.

Zirconium phosphates

Dear Reader,

A while ago I wrote a lot about Prussian blue the wonder solid which captures cesium, the fact that people want to read what I write about Prussian blue made me think about the other inorganic ion exchange solids. One important one is the 2D network of zirconium hydrogen phosphate.

This can be quite simple to make, one synthesis is simply boiling together a zirconyl salt with phosphoric acid. This forms a layered solid which contains hydrogen phosphate groups, the hydrogen phosphate groups can be deprotonated and then cations can bind to the solid. One important person in this field is Abraham Clearfield who has written many papers on the subject of this class of solid. (Brian M. Mosby, Agustín Díaz and Abraham Clearfield, Dalton Trans., 2014, 43, 10328-10339).

Here we can see one of the layers in the solid it is a 2D network of zirconium atoms and hydrogen phosphate groups.

A layer of zirconium hydrogen phosphate

The 2D sheets then make a layered solid with many many layers. Here are some pictures of the layers of the solid.

Three layers of the layered zirconium hydrogen phosphate

When the zirconium phosphate is immersed in a solution of a metal some of the protons in the hydrogen phosphate groups can be replaced with metal ions, for example in the following diagram the layers in a potassium exchanged zirconium hydrogen phosphate can be seen.

One layer of the zirconium phosphate after exchanging with potassium ions

Again the layers can be seen

Three layers of the potassium exchanged zirconium phosphate

We will have a look at some other interesting solids soon,

Cobalt-60 theft in Mexico

Dear Reader,

It has come to my attention that a truck containing a radioactive cargo from a hospital (A used cancer treatment unit) was stolen recently in Mexico. You will be glad to know that the radioactive cargo has been found. A short comment on the case (made at an early time) by the IAEA can be seen here.

Currently it is unknown why the truck and the radioactive cargo was stolen. I do not know if it was a simple truck theft where they wanted the truck, a scrap metal theft or something more sinister such the theft of radioactivity by someone with the intention of causing harm with it (dirty bombers ?).

I hope when I get some time soon to be able to comment further on this case and on cobalt-60 in general. One report claims that circa 3000 curies of cobalt-60 was inside the machine when it was stolen. From my own personal experience I can tell you that this is a large amount of radioactivity, I would expect that the outside of the shielding could feel warm if that amount of radioactivity is inside. The warmth is due to heat being created in the shielding by the absorption of the beta and gamma rays from the cobalt-60, this heat production (decay heat) is perfectly normal.

We can do some fun calculations with decay heat, but I want to save those for later.

The problem with radioactivity units is that two units for activity exist, the old one (curie) was defined as the amount of radioactivity which is equal in terms of decays per unit time as one gram of radium-226. This is a very large amount of radioactivity, one curie is 37,000,000,000 radioactive decay events per second. Or as I would write it 37 x 10⁹ events per second. On the other hand the modern (SI) unit for radioactivity is the Becquerel which is named after the discoverer of radioactivity. This is defined as one radioactive event per second.

The problem with the  Becquerel is that it is very small and for most applications, event things like expressing how much natural radioactivity is in a person, a kilo of earth from my garden [As far as I know there has never been a radioactive soil contamination problem in the town where I live in Sweden] or a packet of coffee) you need to write a large number.

The great problem I see with the curie and the  Becquerel is that both units are very different to each other in size, the  Becquerel can be thought of being like expressing the weight of a car in grams while the curie can be thought of as like expressing the weight of my dog in terms of equivalents of blue whales.

Fukushima water leak

Dear Reader,

It has come to my attention that a tank holding radioactive waste water at Fukushima has been leaking,

The story is that workers found leak from a tank and a puddle of water which was about 9 square meters (1 to 2 cm deep) which had leaked, this was found to be radioactive. This water was contained inside a dyke and had not started to flow into the sea. A second puddle was found outside the dyke (3 square meters and 1 cm deep). This was in the H4 area.

This water was found to be radioactive, it had 46 Bq of Cs-134 per cubic cm, 100 Bq of Cs-137 per cubic cm, 1.2 Bq Co-60 per cubic cm, 1.9 Bq of Mn-54 per cubic cm, 71 Bq of Sb-125 per cubic cm, 80 kBq of total beta activity per cubic cm and it contained 5200 ppm of chloride per litre.

In this area TEPCO workers measured dose rates of 6 mSv per hour in a drainage channel.

TEPCO workers also found a pair of leaks in the H3 area near a tank where the worst dose rate was 100 mSv per hour. Later radioactive water was found in drainage channel B (0.15 Bq of Cs-137 per cubic cm) this is near the H4 area. A set of diagrams of the tank farms and the drainage channels can be seen here.

The cesium level in the water leaking from the tank farms is much lower than the water which is flowing out of the reactor buildings, according to a recent report the water in the central radioactive waste treatment buildings is in the range of 55000 to 28000 Bq of Cs-137 per cubic cm. After the cesium removal plant the water only has 5 or fewer Bq of Cs-137 per cubic cm.

The radioactivity levels suggest one of two things is happening, either the leak is a very new leak which and the radioactivity has not had a chance to percolate out into the drainage channel which flows into the sea. Alternatively the soil is acting as a filter for the radioactivity, this could account for the much lower radioactivity level in the ditch water which is flowing to the sea.

What is needed in the long term are details of how well the soil on the site binds to cesium and also the cesium absorption capacity of the soil. When I know more I will provide you with my thoughts on what is happening. But always bear in mind that when radioactive cesium is a problem clay can often be your best friend.

On of the key parameters needed to understand how well the clay will trap radioactivity is the Kd value, to understand Kd please look at this post about plutonium in spanish soil. Also do bear in mind that not all clays are equally good at catching cesium for details of some different clays please see here.

Mud in Fukushima

Dear Reader,

It has come to my attention that mud at the bottom of swimming pools at Fukushima has been found to contain cesium. A film has appeared on another blog which claims to be a reading of the work of a Masakazu Honda. In this film and the text it points out that the mud at the bottom contains lots of cesium while the film suggests that nothing was noted when the water was tested.

This is perfectly reasonable in terms of chemistry, I have been saying since the accident occurred that the cesium will stick to soil minerals. I would say that it is important to consider both the water in the pools and the mud at the bottom. I think that the best thing might be to use a swimming pool vacuum cleaner to suck out the mud. The mud will then have to be sent away as radioactive waste. It may be best to condition the mud with cement (plus put it into plastic drums) before sending it away as these actions will make a release of radioactive muck less likely during transport.

The cement will not bind the cesium, but it will hold the radioactive soil particles in a solid which will not form mobile dust. The best thing may be to put the waste into a waste store. If this is left for 300 years then the cesium will decay away and the drums will be giant paperweights.

Be careful of two groups of people, one lot to watch out for are the professional doomsayers. They seem to be unable or unwilling to find a real and useful job and then they make their money by scaring the wits out of people. They will tell you that the Fukushima accident has extinguished all hope and that there is nothing which we can do to protect ourselves or clean up our environment. The second lot are those who claim that there is absolutely nothing to worry about and that you should ignore the results of the Fukushima accident. My advice is do not trust either of these “friends”, they are false friends who will lead you into different but equally bad places.

Cesium chemistry in Japanese soils

Dear Reader,

After having spent much of sunday in a fruitless search for a storage box for my garden tools, I get the chance to write to my beloved readers another blog entry. Now all along I had been making the prediction that the cesium would stick like glue to the soil and stay in the top layer. Some workers have examined soil samples and in a paper (Takeshi Fujiwara, Takumi Saito, Yusa Muroya, Hiroyuki Sawahata, Yuji Yamashita, Shinya Nagasaki, Koji Okamoto, Hiroyuki Takahashi, Mitsuru Uesaka, Yosuke Katsumura and Satoru Tanaka, Journal of Environmental Radioactivity, 2012, 113, 37-44) an examination of soil samples from the Fukushima area has been reported. In this paper it has been shown that the cesium is concentrated in the top layer of the soil.

Circa 70 % of the cesium is in the top 2 cm in the soil, while the iodine was more mobile. The good news is that the cesium will not enter ground water, further good news is that plants with deep root systems are unlikely to absorb much cesium. The bad news is that the cesium will be in the right part of the soil to enter grass via its shallow roots and the fact that the cesium is in the upper layers of the soil will increase the external threat due to gamma photons.

It is interesting to note that the Japanese may not worked out a sensible way to store the contaminated soil which is removed during the clean up of land. It has been reported that people are being required to store contaminated soil from cleaning up their own gardens on their own land. I think it would be better if industrial estates were used as places to store the contaminated soil while the government find a place to store the soil for the next 300 years.

I have spoken to my legal advisor about human rights, and my advisor told me that the right to have a safe environment could override the right to object to a waste store in a given town. I hold the view that if the waste stores are sited well away from homes and other places where the general public spend a lot of time, then it is OK to raise the dose rate in the waste store. The waste store should be designed to avoid releasing cesium into the environment and the construction of the waste store should be done in such a way that it does not increase the dose rate at the edge of the site. I think that the reference dose rate for the latter point should be the dose rate at the edge of the site before the clean up is done.

If the dose rate at the edge of the site is 2 microSv per hour, then this will give a person a dose per year of 17.5 mSv which is a big dose for the general public. But if the dose rate at the same spot was 2 microSv per hour before the clean up which generated the waste which will go into the store is conducted then the clean up will have a neutral effect at the edge of the waste store but will have a good effect on the majority of the land.

I may do some calculations on the subject if I get time in the near future.

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.

Different reports on the same subject

Dear Reader,

In recent times we have had the first serious nuclear accident of the internet age, I am not sure why it is the internet age. The ‘ages’ were named after the materials used to make typical tools.

Stone age : Stone axes

Bronze age : Bronze swords made of a Cu / Sn alloy

Iron age : Iron ploughs

Then later the industrial age came, then we had the atomic age, the space age and then the internet age. My big problem is that for the majority of tools which we use in our lives we do not use atomic (nuclear), space or internet tools to do things like open cans of dog food or dig our gardens. For opening pet food cans and tending the vegetable patch I still use tools based on iron (steel).

While a nuclear powered digging machine or a space satellite which zaps the weeds might make life a little more easy (assuming you can afford to buy it) I think we will be sticking with steel spades and can openers for the forseeable future.

But I think that we do need to move onto something else. Recently a series of different reports have been published about the Fukushima event in Japan. Greenpeace have published a report as have the Japanese government and also Jon. M. Schwantes et. al. in the journal Environmental Science and Technology (DOI: 10.1021/es300556m) have published a paper in which they use the isotope signature of the accident to probe the event. In common with many things it is not always possible to make a direct measurement from samples which can be taken by hand, instead other measurements were used.

Now before we get going I will saw that it is impossible to have a single report which deals with a complex event in perfect detail. The problem is that if we examine one aspect of an event in great detail (using a state of the art study which includes as many details as possible) then this report is likely to become very large and close to impossible to read. If we then couple together a series of sections with a similar level of detail on all the different aspects of the event then we will end up with a wall of words which is impossible to comprehend.

Greenpeace have written about a recent Japanese report that

“The lethally high levels of radiation still present in the damaged reactors have prevented committee members from conducting a full analysis. They should be given all the time they need to complete their investigation.”

While the Japanese writers of the big government report stated that their mandate was

1. To investigate the direct and indirect causes of the Tokyo Electric Power Company Fukushima nuclear power plant accident that occurred on March 11, 2011 in conjunction with the Great East Japan Earthquake.

2. To investigate the direct and indirect causes of the damage sustained from the above accident.

3. To investigate and verify the emergency response to both the accident and the consequential damage; to verify the sequence of events and actions taken; to assess the effectiveness of the emergency response.

4. To investigate the history of decisions and approval processes regarding existing nuclear policies and other related matters.

5. To recommend measures to prevent nuclear accidents and any consequential damage based on the findings of the above investigations. The recommendations shall include assessments of essential nuclear policies and the structure of related administrative organizations.

6. To conduct the necessary administrative functions necessary for carrying out the above activities.

I have highlighted in bold the part which interests me most as a chemist, the Japanese panel  also stated that they would not undertake a series of actions which included.

“investigations that would require on-site visits to reactors with dangerous levels of radioactivity.“

My understanding is that they have chosen quite wisely to avoid either waiting for a full examination of the reactor sites (which will take decades) or rushing into a dangerous area to gather data. My view is that samples collected from outside the reactor buildings, eye witnesses from the site, data from those sensors inside the plant which continued to work together with details which can be obtained from undamaged BWR plants. I see the problem of the clash of two cultures.

The scientific and engineering communities are seeking to get the best quality report which is correct, the speed of publication of the report is a secondary factor. In these communities it is better to delay the publication of a report if the delay will allow the quality to be improved. Also the answer has to be traceable, the computational methods used, the persons who did the work, the devices used and the samples used all have to be documented clearly in this type of work.

On the other hand the newspapers and many of the green NGOs (like Greenpeace) are aiming for speed of publication as their highest priority. In these reports the things which were used to produce the final answer are often not as traceable. What is interesting is when both the rapid publication of people like Greenpeace agrees with the slower and more thorough investigation which goes into the official reports. I would say that it is important to avoid being caught by statements by “The findings of both these reports match closely with the Lessons
from Fukushima report released by Greenpeace in February” in a trap where you think that both reports are the same.

The Greenpeace report has some similarities with and some differences from the Japanese government report, but I would say that neither report deals at length with the containment chemistry and the radiochemistry of the accident. I am unsure of what Greenpeace would be hoping for in an extended report which might be written in 20 years time when the insides of the containments have been fully explored. I think that a main part of the final purpose of the examination of the reactor buildings will be to determine what chemical and physical effects occurred during and after the accident.

The Greenpeace report is more dominated by photographs which relate loosely to the event, I am unsure why it is important in a report of 52 pages to include devote ten pages to photographs of things like wrecked buildings with very little explanation of what is going on in the photograph. For example on page 28 a whole page is devoted to a person holding a pair of radiation meters in a field. There are a series of important questions which are not answered in the text such as “what level of radioactivity has the person found in the field”, “what is the testing protocol” and “what is the date of the measurement”. I hold the view that the report should be written in a way to make these things clear rather than forcing the reader to dig deeply in a series of documents for the answers.

The Japanese government report is much more text and far fewer pictures in the main body of the text than the Greenpeace report, towards the end a lot of data is presented in appendix in the form of graphs. These graphs include things like the fraction of the public who were aware at a given time of some key events. While graphs might be less eye catching than photographs, I hold the view that a well labeled graph is a better way to communicate an idea to another person than a photograph which has little if any commentary in the caption.

The problem I see is that if I show 100 people a photograph with very little writing in the caption then a danger exists that each of the 100 people will interpret it in a different way, while in recent years there has been a backlash against science made by people like the postmodernists. Some people value their “feelings” above everything else and express the view that a series of different interpretations of the same evidence are equally valid, I have to disagree. Firstly there is no such thing as an impartial observer (Read the section of the Alan Chalmers book “Whats this thing called science” on induction for more details).

Secondly some interpretations of evidence are deeply wrong, for example if I was photographed by an alien (who has no knowledge of pet ownership) while walking my dog in the forest the aliens might think (based on the photograph) that I am some sort of cruel person who enslaves small white animals and chains them up. While this interpretation might fit the evidence in the photograph it is deeply flawed.

As a result I think that a report which is dominated by photographs which do not have a clear set of captions explaining what is going on is not a good report. But a report which uses the same amount of space for graphs and figures which bear captions which explain all the key points does communicate in a better way with the reader.

The comment that Greenpeace made of “The lethally high levels of radiation still present in the damaged reactors have prevented committee members from conducting a full analysis. They should be given all the time they need to complete their investigation.” suggests to me that Greenpeace want the Japanese government report to be a comprehensive report which deals with all aspects of the event. It might even be understood as Greenpeace suggesting that their report is more comprehensive.

I have read both reports and I can say that some rather important things are missing from both reports. Neither report mentions the transfer of cesium from soil to plants and then to humans via the food supply. I hold a view that this is an important issue, depending on the soil chemistry, the biology of the food production system and what countermeasures are taken the cesium in the diet is either going to be a small issue or a large issue. Also neither report gives a detailed list of the radionuclides released from the reactors and the amounts which were in the cores during the accident.

One of the best reports on this issue is the paper by J.M. Schwantes et. al., this paper uses the relative amounts of the different radionuclides in soil samples taken from Japan to work out what happened inside the cores of the damaged units.

This paper concludes

1. Volatility dictated by temperature and reduction potential dictated the fraction of the radioisotopes which were released.

2. All coolant was likely to have evaporated by the time the containments were vented.

3. The damage to the fuel was extensive.

4. The vast majority of the less volatile elements such as plutonium, niobium and strontium were contained within the reactors.

In the paper it has been calculated that the ratio of released cesium to plutonium from the Fukushima event was 100000 : 3 which suggests that the Fukushima event was far closer to a pure cesium / iodine release than the Chernobyl event was. The cesium to plutonium ratio for Chernboyl was about 10 : 1. I had from an early time made this prediction as the Chernobyl and Fukushima events were very different types of accident. One was a power surge while the other was overheating.

The most interesting thing in this paper is the graph of soil activity / reactor inventory against the oxygen potential of the dominate oxide form. This graph suggests that the more thermodynamically stable the oxide is then the less of the element will be emitted. The good news from this graph is that worst elements (plutonium) will not be emitted. The only problem is that the graph has some points which are a long way from the trend line.

More barium was released than this graph suggests while less ruthenium and silver was released than this simple model suggests. I think that I can explain why less ruthenium was released, the most easy ways to release ruthenium are either as fuel particles (which did not happen at Fukushima) or as ruthenium tetoxide which would not form as the reactors stayed under reducing conditions during the accident.

Clay again

Dear Reader,

Again we are turning out attention to clay, clay is a wonderful substance on which we play tennis on, make pots from and create art with. Clay is also important when cesium gets into our soil. I recently wrote a little on the subject of the clay minerals in the soils in Japan. Here is a useful set of lecture notes on silicate minerals, most clays seem to be silicates.

I have recently read that the soil from Japan holds tightly onto cesium, when soil which was contaminated by the Fukushima event was soaked in 1 M ammonium chloride solution (at 25 oC) only about 20 % of the cesium radioactivity was liberated from the soil. Then when this soil was treated with 1 M acetic acid only about 10 % more of the cesium was liberated from the soil.

It was also found that treatment with 1 milimole per litre sulphuric acid only was able to liberate less than 1 % of the radioactivity while 1 mole per litre sulphuric acid was able to liberate about half the cesium.

These findings suggest it will be hard to wash the cesium out of the soil, but if the soil is washed with ammonium chloride then the remaining cesium will be hard to transfer to plants. I suspect that as time goes on that the amount of cesium which can be transferred to the plants will become less and less as the cesium becomes more and more fixed to the minerals in the soil.

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.