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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

trinitite9

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.

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New SSM project, Lets make banish radiation accidents to science fiction.

Dear Reader,

It has come to my attention, and I imagine many of my readers attention, that radiation accidents feature on a regular basis in science fiction. Many science fiction tales have at their core some form of radiological misadventure for example the incredible hulk and spider man both were “normal” men until they were subjected to a dose of radiation or bitten by a radioactive spider.

I am sure that my readers will be glad to know that governments, university academics and other groups are working towards a world where horrid radiation accidents are only found in science fiction. As part of this effort the Swedish radiation protection authority (SSM) are supporting work in the Nuclear Chemistry unit at Chalmers. In this work the effects of chloride contamination on the release of fission products from fuel and the capture of organic forms of radioactive iodine onto charcoals is being investigated.

The chloride contamination issue became of interest during the Fukushima accident, in this accident sea water was used to cool the stricken nuclear reactors for some time. If the reactors had dried out a second time then nuclear fuel could have been exposed to molten salt. Some of my readers will be aware of the fact that metal chlorides tend to be more volatile than metal oxides. For example copper chloride is more volatile and is able to enter a flame where it generates green light. The effect of dichloromethane on the flame coming from a brass butane torch can be seen in the following film.

It is reasoned that if a similar process is able to increase the mobility of a fission product then a salt addition could increase the threat posed by a reactor accident to the public. Also this study could offer an insight into an accident in a chloride based pyro-reprocessing process using a molten salt such as a NaCl/KCl eutectic.

The other area relates to both sampling and personal/collective protection. One of the methods of measuring radioactive iodine in air is to use a Maypack filter. This is a device through which a large volume of air is sucked. After sucking the air the Maypack is dismantled and the different parts measured for radioactivity. It is possible to determine what chemical form the iodine was in when it reached the Maypack. Aerosols, elemental iodine, HOI and organic iodine all collect in different parts of the device. Methyl iodide is known to react with charcoals which are impregnated with chemcials such as potassium iodide and DABCO. However if an organic form of iodine which is unable to react quickly with KI and DABCO was to enter the charcoal pad in the filter then it could revapourise and be lost from the charcoal pad. As the organic iodine fraction is often a major part of the radioactive iodine released from a nuclear plant this could result in an underestimation of the amount of radioactive iodine released from a plant.

Also if the organic iodine compound is more able to pass through charcoal pads in respirators then it could cause the protection factor of a respiratory to be lower than that predicted by tests using methyl iodide which seems to be the de facto standard alkyl iodide used in nuclear safety experiments. We hope in this project to test the hypothesis that the DABCO loaded charcoal is able to capture all the organic forms of iodine which can form during an accident. This work is of interest to the ISO organization (ISO TC94 SC15 WG2&WG3 PG3 JTG CBRN) as the ISO organization is currently considering a standard for protective clothing for use in the nuclear / radioactivity sector.

Now while nuclear / radiological accidents are clearly not “fun” and are not joking matters, it is important to understand that the nuclear chemistry section at Chalmers is not a “Fun Free Zone” (FFZ). Years ago I read a chemistry laboratory manual which commented “Chemistry should be done while sober but not while somber”. A trip to a chemistry department should not have to be sad and unhappy, even those who toil in the nuclear chemistry section are allowed to share a joke, well that is as long as it is in good taste and on an acceptable subject.

Here are some of the people who work on nuclear accident chemistry eating gazpacho soup, now you might ask what is so funny about gazpacho soup. Well to understand the cultural significance of this soup to me you need to know of Red Dwarf.

Emma on the left and Mark on the right, both are enjoying some soup.

Emma on the left and Mark on the right, both are enjoying some soup.

One classic British comedy which is well known to people of my generation is Red Dwarf which is about the last man left alive in the universe, again in the first episode this sci-fi story features a radiation accident which I would rank being at least. INES level five (based on the death of the whole crew of a spaceship). Maybe it might be an INES level of six based on the large number of deaths.

One of the central figures (Rimmer) who is a rather disagreeable fellow died in the first series before returning as a hologram. His last words were “gazpacho soup” which relates to the event which he credited with ending his career. He sent the cold soup back in disgust in front of the ship’s captain demanding that it be heated up. In fact the pompous, officious and cowardly Rimmer was doomed to failure because of other matters.

He spends many hours with a more laid back man in this science fiction comedy often being the subject of many jokes. For years I was in blissful ignorance thinking that gazpacho soup was something invented by the script writers of Red Dawrf, while as a postdoc on a busniess trip to Spain years ago I saw it on the menu of a restaurant. I then tried it partly out of curiosity and partly as it felt funny to be eating the substance that troubled Rimmer so much.

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.

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