Trinitite II

Dear Reader,

I have reexamined the gamma spectrum from the trinitite, and I have some news for my loyal readers. What I did was to look at someone else’s gamma spectrum of trinitite and then try to match peaks.

Here is the spectrum

Gamma spectrum of trinitite

What we can now see are two peaks (51.7 and 129.3 keV) which are due to the gamma emissions from plutonium-239. Also we can see a set of three lines due to uranium L lines X-rays.

We might ask why are we seeing uranium x-rays coming from a sample which contains so little uranium. One explanation which I think is very reasonable is that the alpha decay of the plutonium-239 forms uranium-235 which is formed in an electronically excited state. The uranium-235 then undergoes a rearrangement of the electrons to form the X-rays. This has been observed by others during XRF studies on plutonium metal.

This is further evidence that the sample contains the radionuclides which should be expected from the trinitiy test. So now I have managed to prove that the sample contains plutonium.

As the sample also contains americium-241 I think it would be reasonable to next make an attempt to find the lines for neptunium X-rays. These could be a further sign that the sample contains americium. I can not think of any other alpha emitters which will be present in large / moderate or even less than tiny amounts in the trinitite.

I will have to think further about the sample.

Trinitite

Dear Reader,

Recently I purchased off eBay a small lump of trinitite, now I had been warned that a lot of fake trinitite is being offered for sale. So I choose to take the step of examining the sample with gamma ray spectroscopy.

In less than a minute I had been a peak at 668 keV which could either be due to either ²¹⁴Bi (665 keV from the beta branch) or ¹³⁷Cs (662 keV from ^137mBa) was seen. This peak suggested that some radioactivity was present in the sample. I did a quick check at 609 keV. The line at 665 is emitted during a small fraction (1.46) of beta decays of ²¹⁴Bi, while the 609 keV photons are emitted by 46.1 of all decays. As a result it is clear that the sample contains some man made radioactivity.

Next I looked at the low energy end of the spectrum, here is a log log view to allow you to see this part of the spectrum better. I found a strong peak at 66 keV. I suspect that this is 59.5 keV peak for americium, keep in mind that the energy calibration of the detector is a little off. It was over reporting the energy of the ^137mBa, so it is not totally unreasonable for it to over report the energy of the ²⁴¹Am. As americium is associated with plutonium this is a good sign that the rock is a true lump of trinitite.

I then looked for some of the other lines of this americum nuclide, I looked for 99 and 103 keV photons. I found peaks at 99, 101 and 105 keV. This suggests that some peaks were in this expected range. Maybe it could be americium present. At 81 keV we should expect a peak for ¹³³Ba, in our spectrum we see peaks at 81.7, 83.8 and 87.7 keV.

Also at 128 keV the spectrum contains a peak which could be due to the 122 keV line from ¹⁵²Eu.

The spectrum also contains at 1414 keV a line which could be due to the 1408 keV emission from ¹⁵²Eu. Also this nuclide will emit at 964, 444 and 245 keV. In the high energy part of the spectrum we can also see a line at 1466 keV which corresponds to the 1461 keV emission of ⁴⁰K (decaying into ⁴⁰Ar).

In our spectrum we see a line at 969 keV which can be matched with the 964 keV emission of ¹⁵²Eu.

We can go further into the problem, in the range of 400 to 500 keV it is hard to decide if a peak is present. The signal to noise ratio is too bad in this range.

Now if we try again in the range of 200 to 300 keV range, we can see a line at 251 keV which is a possible match to the 245 keV.

The section of the spectrum between 300 and 400 keV shows peaks at 358 and 362 keV one of which could be the 356 keV line for ¹³³Ba.

I think that after seeing this evidence that we can come to the conclusion that the rock sample came from a place where a nuclear fission event occurred, so it is likely to be real trinitite.

We will come back to this later, what I hope to do next is to try to estimate the way in which the efficiency of the detector changes as a function of photon energy. We will try to match the different lines from different radionuclides to the graph.

Thorium fueled reactors

Dear Reader,

It has come to my attention that the thorium based fuel cycle is being discussed in magazines such as “Chemistry World” which is the magazine of the Royal Society of Chemistry. As with all technology it is important that we have a honest and reasonable debate about it.

One attractive thing about the thorium fuel cycle is that it tends to form less of the transuranium elements such as plutonium, one idea for a nuclear fuel would be to make a mixture of thorium and plutonium dioxides. The idea is that the plutonium will provide the seed fuel while new fuel can be made from the thorium. Natural thorium  (²³²Th) can be converted by thermal neutrons into  ²³³Th which will decay via  ²³³Pa into  ²³³U.

In many ways a thermal reactor is better than a fast one, I assume that many of my readers have heard of the term “fast breeder”, the idea of a fast breeder reactor is that it uses fast neutrons to make more fuel than it consumes. Commonly a fast breeder is fueled with a mixture of  ²³⁸U and something fissile such as  ²³⁵U or  ²³⁹Pu. The reason why a fast neutron spectrum is better is that thermal neutrons can cause fission of ²³⁹Pu but the fission to capture ratio for fast neutrons is more favoring fission than capture. The capture (nγ reaction) of neutrons with ²³⁹Pu tends to form a neutron poison (²⁴⁰Pu) which is activated further to form ²⁴¹Pu which undergoes beta decay to form minor actinides such as ²⁴¹Am and even curium. These minor actinides can be a right royal pain. Another problem is that in a thermal reactor the formation of ²³⁶U by the nγ reaction of ²³⁵U can occur, the ²³⁶U is long lived and can be activated further to make short-lived ²³⁷U which can decay into ²³⁷Np. The ²³⁷Np can then form by another capture reaction ²³⁸Np which does a beta decay into the house of horror bugbear isotope of plutonium (²³⁸Pu). It is interesting that while the greens complain about the “evils of plutonium” they never seem to mention the fact that a lot of plutonium formed in power reactors is more alpha active than pure ²³⁹Pu. They seem to be trapped in their thinking by the long half life of the nicest plutonium isotope, ²³⁹Pu is not very radioactive gram for gram when compared with many other things such as radium.

As the ²³⁹Pu undergoes less activation and more fission in a fast reactor it is a logical choice for making and using plutonium, but on the other hand a fast reactor is bad for the thorium based fuel cycle. Here the desired outcome is neutron capture by natural thorium. The intended reactions are the neutron activation of ²³²Th to form ²³³Th (_t½ 22 min) which decays by beta decay to ²³³Pa (_t½ 27 days) which in turn undergoes a beta decay to ²³³U (_t½ 159200 years). While ²³³U can be used for both reactor fuel and bombs, it is interesting to note that it is normally contaminated with some ²³²U. The decay of ²³²U forms high energy gamma emitters which will increase the dose rate near the ²³³U, this could make bomb and fuel fabrication more difficult.

The unwanted reaction in the thorium containing reactor is the n,2n reaction on ²³²Th to form ²³¹Th, the ²³¹Th then does a beta decay to get to long lived ²³¹Pa. The next neutron capture then forms ²³²Pa which decays into ²³²U.

Some of the daughters of ²³²U (²⁰⁸Tl and ²¹²Bi) emit very high energy gamma rays (up to 2.6 MeV) which will be much more troublesome than the gamma rays from ²⁴¹Am which is commonly found in plutonium which has been allowed to age for some years. The majority of the gamma rays from ²⁴¹Am are much lower in energy (60 and 33 keV) are much lower in energy and thus can be shielded against with a lead apron (circa 1 mm Pb) or a sheet of glass attached to a glove box. To attenuate the ²⁰⁸Tl gamma rays a very thick layer of shielding would be required making glovebox work impossible unless the glove box worker is willing to incur a large hand dose and happens to look rather like Mr Tickle of the Mr Men.

The key thing to understand is that a slow or thermal neutron has too little energy to do the n,2n reaction on the natural thorium. While a thermal neutron is able to do the neutron capture which we want. With some luck we can consider some reactor designs which reduce the formation of ²³²U.

More uranium glass

Dear Reader,

I have been in the second hand shops today of Lidköping, I have managed to find some more uranium glass. The glass does glow a nice green / yellow when you expose it to UV light. I will have to make a radiometric examination of the glass to determine if it is uranium glass or some other glass which has similar optical properties.

I think in future I will carry a UV torch in my pocket when I am out and about, here is a photo of the glass under normal light.

Mark’s new uranium glass

Here is a photo when the only light is UV light from my UV torch.

My new uranium glass with UV light, notice it is glowing green

I will examine the glass as soon as possible, then I will post the results of my tests.

SSM and ISA

Dear Reader,

Those of you who live in Sweden may have heard of a body called SSM (StralSakerhetsMyndigheten), this is a state body in Sweden which has the task of protecting people and the environment from the adverse effects of radiation both today and in the future. In common with the now defunct NRPB their task includes X-rays, “Nuclear” radiation (α, β, γ and neutrons), radiowaves (cell phones etc) and UV light.

One of the great problems we as a society is that for the good radiological protection of future generations living far in the future we need to make predictions based on experiments which only last a short time.

One important issue is the formation of organic complexing agents in low and intermediate level radioactive waste. If a substance forms which is able to bind to metals and form water soluble complexes which do not bind to mineral surfaces then the rate at which radioactivity leaks out of a waste store could be increased.

One such compound which has been considered by many people is isosaccharinic acid (ISA) which is formed from cellulose when it is exposed to calcium hydroxide. The cellulose can come in the form of wood, paper or cloth while many cements contain calcium hydroxide.

The classic way to make ISA is to treat lactose with calcium hydroxide, I have done this several times and the mixture soon turns brown and after boiling it down you are rewarded with a dark brown mixture which smells strongly of cooking. By careful filtration of the dark brown mixture a brown solution can be obtained which is then evaporated to a dark solid. This is then extracted with water and recrystalized to give a white solid, due to the insolubility of the calcium salt of the alpha isomer of ISA this is possible. The calcium salt of the beta isomer is water soluble and stays in the mother liquor with a lot of other compounds.

As a result it is relatively easy to obtain alpha ISA, the beta ISA is harder to obtain, so as a result almost all work done on ISA has been done with the alpha isomer. As the properties of the two isomers are not exactly the same it may not be safe to assume that alpha ISA can be used to model a mixture of alpha and beta ISA. Within this project we will explore beta ISA and determine if it poses a special threat in nuclear waste stores.

Now you might wounder why I mention SSM, the reason I mention them is that they are funding this research. One of the ways that SSM protect society is to fund research which allows them to make better predictions about the future. Now my SSM work is about to start, the plan is that I will try to publish papers as well as writing a report for SSM. I also want to bring you some updates about the work here on my blog.

Candlestick II

Dear Reader,

I took my candlestick to work and I quickly found it was radioactive, it was emitting beta particles according to a quick check with a contamination meter. As it was emitting that nice yellow/green light when exposed to UV light and it was emitting beta particles I quickly decided it was genuine uranium glass.

The next step in the characterization of the candle stick was to use gamma spectroscopy on it, now before we get going I would like to point out that gamma spectroscopy is not a press the button and get the result type of machine. For those of you who are proper traditional chemists / scientists you will be aware that for a new type of sample it is very hard with most machines to create a method with a spectrometer where you just put in the sample and press go before getting the final answer.

One of the problems is the issue of self adsorption, for the lower energy gamma lines many of the photons will never escape from a large sample. The ideal sample for gamma spectroscopy would be a tiny spec (a point source) which would be at a well defined distance from the detector.

The candlestick is anything but well defined in distance from the detector and it is far from being a point source. I did not want to melt it down to make a lump with a more simple shape so I decided that we should measure it in its native form.

One of my questions about the candle stick was “is the uranium a depleted uranium, or is it a natural uranium which is likely to predate the nuclear age ?”

I reason that as DU is less valuable than natural uranium it would be the logical uranium to use if you were making a uranium glass candlestick in the 1950s or later. But if it was a more early candlestick then it would be more likely to have a natural isotope signature for its uranium.

We need to consider three uranium isotopes

²³⁸U which is the bulk of natural uranium, this does not have any useful gamma lines but its daughter (²³⁴Th) which emits gamma rays, as the half life of ²³⁴Th is short when compared with the age of the candle stick it can be treated as an extension of the radioactive decay of the parent ²³⁸U. 70% of the ²³⁴Th will decay to the meta stable state of ²³⁴Pa (^234mPa). It is important to note that the ²³⁴Pa (both forms) give a forest of gamma lines (hedgehog spectrum).

Nuclide	Half life	Decay mode	Main gamma lines
238U	4.468 x 109 years	alpha	No gamma
234Th	24.1 days	beta	63.3 (4.8 %), 92.4 (2.8 %) and 92.8 (2.8 %)
234mPa	1.17 minutes	beta	258.3 (0.73 %), Hedgehog spectrum
234Pa	6.7 hours	beta	Hedgehog spectrum

 

If the uranium had been a depleted uranium then I would expect that almost all the ²³⁴U and ²³⁵U would have been removed. As the ²³⁴U has a long half life it serves to block the decay chain of ²³⁸U if the sample is not old on a geological time scale.

I reasoned that by looking for the decay products of ²³⁴U that I could test the hypothesis that the uranium was a prenuclear age natural mixture of isotopes.

This uranium will decay to form a long lived radium (²²⁶Ra) which will then slowly on the timescale of the candlestick’s age decay further.

²³⁴U –> ²³⁰Th –> ²²⁶Ra –> ²²²Rn –> ²¹⁸Po –> ²¹⁴Pb

Nuclide	Half life	Decay mode	Main gamma lines
234U	245500 years	alpha	No gamma
230Th	75380 years	alpha	67.7 (37 %)
226Ra	1600 years	alpha	186 (3.6 %)
222Rn	3.8 days	alpha	No gamma
218Po	3.1 minutes	alpha	No gamma
214Pb	26.8 minutes	beta	242 (7.4 %), 295 (19.3 %), 352 (37.6 %),
214Bi	19.9 minutes	beta	Forest of lines
214Po	0.1643 ms	alpha	No gamma

 

The ²¹⁴Pb will decay by beta emission to form ²¹⁴Bi and then ²¹⁴Po which then decays to form ²¹⁰Pb. As after ²²⁶Ra no nuclide has a half life longer than a few days until you reach ²¹⁰Pb we can treat these decays as extensions of the radium decay if we make a kinetic model of the candlestick.

The fissile ²³⁵U does have a useful gamma emission of its own, this can be used to confirm if the uranium was natural or depleted.

It will decay by alpha emission according to the following mechanism.

Nuclide	Half life	Decay mode	Main gamma lines
235U	703800000 years	alpha	109 (1.5 %), 144 (11 %), 163 (5.1 %), 186 (57 %), 205 (5%),
231Th	25.52 hours	beta	No gamma
231Pa	32760 years	alpha	Forest of lines
227Ac	21.773 years	beta	No gamma
227Th	18.72 days	alpha	Forest of lines

 

I hope to now be able to go through the spectrum and then hunt for lines, I recall that the 186 keV line for ²³⁵U was present. So far I think the uranium is from before the nuclear age.

Microscope and more on the islands of stability

Dear Reader,

I bought a microscope today at Lidl, it was a German microscope (BioLux Bresser). When I get the chance I will try it out and tell you people what I can see. The nice thing is that this microscope has a USB camera which comes with it.

But before I get onto that, here are some pictures of the island of stability which I plotted. I have ploted the neutron and proton numbers on the horizontal scales and on the verical scale the log (base ten) of the half life in seconds. I have ignored all nuclides which have half lives shorter than 1 second.

Here are the pictures.

Radioactive waste from wind power

Dear Reader,

I am sure that many people have told you of the green nature of wind power, it is sold to the public as the ultimate green energy production system. It has reached the point at which it seems like nobody is allowed to say anything bad about wind farms, but we need to keep our wits about ourselves.

Many high tech and green gadgets need rare earths (lanthanides), the name is a bit of a misnomer some of the lanthanides are very common in the earth. But some of them are very rare elements, the worst bit is that the rare ones are the more useful ones. For example the red phosphor in a colour TV is traditionally europium doped yttrium oxide or europium doped yttrium oxysulfide. Europium is a rare lanthanide which often forms compounds which emit red light.

Now with many gadgets such as electric cars and windmills people think they are green because they do not release any pollution during use, it is important to understand that a gadget such as an electric car is not a “zero emissions vehicle” it is an “emissions elsewhere vehicle”. One emission type are those which occur during the use of the machine and the others are those associated with the production and final disposal of the object.

If we ignore the emissions during the building of the gadget and its disposal then a nuclear power plant is perfectly green, it emits next to no pollution during use. It is only during the fuel production, building of the plant and the disposal of the fuel that the releases of pollution occur. It is clear that we must consider the whole lifecycle of the parts of the system.

In the case of the lanthanides it is important to understand that the processing of lanthanide ores produces radioactive waste, the problem is that much of the world’s lanthanides are in thorium rich minerals such as the monazite phosphate minerals. As a result when monazite is processed often radioactive waste is produced.

The nasty thing about natural radioactivity in rocks and minerals (harmless or cute sounding) is that it tends to be alpha emitting and often mobile in the form of radon / radium. On the other hand much of the radioactivity in the back end of the nuclear fuel system (scary sounding reactor waste) is short lived beta / gamma emitting fission products and a little alpha emitting waste. Much of this alpha emitting muck is plutonium, while plutonium might sound like a total nightmare it is important to note that it is very immobile in the form of oxide fuel. Firstly it is very insoluble in water and secondly plutonium absorbs very well onto mineral surfaces. To use some non technical language it sticks like glue to mineral surfaces, thus it will not migrate through soil and rocks with ease. Once the plutonium is buried then it will be locked up in the rocks for many thousands of years.

On the other hand radium and radon can move around in water with ease, these elements will not bind so well to mineral surfaces. The waste from lanthanide ore processing is sometimes codenamed TENORM, this means Technologically Enhanced Naturally Occurring Radioactive Material. This TENORM is a major pain in the oil / gas industry and in the ore processing industry.

The best way to reduce the production of this radioactive waste is to recycle lanthanides, by reusing lanthanides instead of mining ore the volume of radioactive waste will be reduced. If you want to support green devices such as hybrid cars and windmills then it is up to you, but I would urge you to lobby for the valuable metals and other materials to be recycled when these products reach the end of their useful lives. If no sensible recycling method exists then a need exists for more research on recycling, one of the things which I am involved with at Chalmers is the Industrial Materials Recycling section. Here we study the recycling of that which can not be currently recycled.

The health condition of the Fukushima Children in Ginza, Tokyo .

Dear Reader,

I saw this film recently, it makes some claims that the Fukushima reactor accident is making children sick. I think that this film raises some interesting points.

Appeal concerning the health condition of the Fukushima Children in Ginza, Tokyo ..

There is a problem, if the above average level of radiation in Japan is able to make children ill then why is Ramsar in Iran not famous for ill children ? In this place in one year the background radiation dose is normally more than 100 mSv.

In Japan it has been decided that if the dose rate is greater than 20 mSv that people will be relocated, so the people in Ramsar should be more ill than the general public in Japan near the Fukushima reactor accident site.

One of the people in the film had to go for a CT scan, I would like to know if anyone has considered how this is likely to have involved quite a large X-ray dose. While people get concerned about an exposure from a reactor accident, many people do not seem to be as concerned about medical exposure (due mostly to X-ray radiography). This is something which I can never understand.

Also if the children of Fukushima were being exposed to so much radiation that they feel ill as a result (chronic radiation syndrome ?) then I imagine that their blood counts would be rather abnormal. If for argument’s sake they were so strongly exposed then blood samples from them would show signs of radiation exposure.

For a large dose, I would expect cell counts to be abnormal. At lower doses I would expect a much higher number of chromosomal abnormalities per litre of blood. If someone can bring us this type of evidence then I will believe that the children of Fukushima have been exposed to a lot of radiation, but until I am presented with such evidence I will remain very suspicious of the claims of these radiation related illnesses. The thing is that to induce the non cancer effects which appear shortly after a radiation exposure a very large dose is required, and the dose must be above a threshold. Below the threshold the effects can never be seen.

It is a bit like alcohol, humans and drunkenness. To get a person drunk requires alcohol, the more alcohol you feed them the worse the drunkenness becomes. Below the threshold dose it is impossible to get the effect of drunkenness, for example if 200 people take communion at a church and have a tiny sip of wine then non of them will come out of the church as crazed drunks (Unless they were drunks before the service). I hold the view that as a result of Fukushima that no member of the general public has had a radiation dose which is able to cause one of the deterministic effects which appear shortly after the radiation dose is delivered to a human.

Even after the much worse Chernobyl accident no members of the public were stricken with the deterministic effects of radiation (radiation sickness), so I would suggest that my readers take care when they here of claims from Japan about the radiation making children feel ill. We need to have a respect for the truth, part of a respect for the truth is to resist telling lies or making exaggerations even if you think (or know) that the thing you want to warn people against is very bad. One of my roles at Chalmers has been to help supervise research on serious nuclear accidents, I can tell you that serious nuclear accidents are thankfully rare but they can be horrible even without inventing new effects or exaggerating the effects.

Americium II

Dear Reader,

I have chosen to write about americium, I had noticed that no posts entitled americium existed on wordpress. Americium is one of my personal bests in terms of Z (number of protons). The element which the highest Z I have ever seen is plutonium, the highest Z I have been in the same room as is californium while the highest Z I have ever used in an experiment which I did myself is americium.

Americium is a element which can not make up its mind, in some ways it is like a lanthanide. It has a very insoluble fluoride and it extracts with bis-2-ethylhexyl hydrogen phosphate into alkane diluents while on the other hand it thinks it is a transition metal. It is more able to bind to nitrogen donors than a lanthanide and it is isoelectronic with uranium(0).

Uranium(0) complexes of cyclopentadienyl ligands are able to bind to carbon monoxide in a similar way to a transition metal. Thus uranium(o) is like a transition metal.

Also americium(III) is coloured, it is pink in colour while the lanthanides are almost perfectly colourless. The formation of coloured metal cations is very much a transition metal thing. For example copper(II) in water is blue while nickel(II) in water is green. Iron(III) is a funny one, in acidic water it is a pale purple but in water it undergoes hydrolysis to form a dark brown complex.

I may well write some more about americium in the near future.