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Daily Snail Scare Story ?

Dear Reader,

I was interested to see an article about nuclear bombs in the Daily Mail which mentioned the loss of a Mark 15 nuclear bomb by the USAF (Tybee Island B-47 crash). This was a hydrogen bomb which was intended to use a fission primary to trigger a fusion secondary. The neutrons from the fusion stage were intended to cause fission of high enriched uranium surrounding the secondary thus releasing the majority of the energy in this bomb design.

Now as the exact details of the bomb design are not in the public domain I will have to make some educated guesses. If we assume that the primary is a plutonium fission bomb then after having been at the bottom of the sea since 1958 then there are some things which will make a nuclear detonation less likely now.

If we assume that the bomb was of the same type as the plutonium bomb used in world war two, then the neutron trigger based on beryllium and polonium-210 will no longer be able to work. The bomb if triggers would not generate the neutron pulse at the right moment to power up the primary. Thus the bomb would not give a high fission yield, it might fizzle but it would never be able to detonate at full yield. With a defective primary I think that the secondary (fusion) stage will fail to go off.

If we were to be dealing with a fusion boosted primary stage then as 58 years have passed, as 4.7 half lives have passed then almost all the tritium in the bomb will have decayed. This would reduce the chance that the bomb would be able to function. Better still unless the bomb has been designed to make a helium / hydrogen separation in the final moments the helium-3 formed by the decay of the tritium will act as a neutron poison. This will have the opposite effect to the fusion boosting of the D-T reaction. So again this will make the bomb less able to function.

Also if we were dealing with a bomb which used an electrostatic D-T neutron generator tube, then the reduction in the amount of tritium in the tube would reduce its ability to generate neutrons. A bomb using this method would be a very advanced bomb design. I am not sure if a 1950s designer would have been able to use this option. My calculations suggest that about 4 % of the tritium would be left. This could have a large effect on the ability of the D-T fusion tube to generate a neutron pulse.

I would also like to point out that to cause a implosion  a very well timed electrical command has to be delivered to the detonators. This is something which would be hard to do by chance, also in the decades since the bomb was lost the chemical explosives will have aged, this may alter their properties and thus reduce the chance of the implosion crushing the plutonium pit to take the fuel into a super prompt critical state.

I also reason that if tritium was added to the secondary fuel to help start up the secondary then the decay of the tritium which was present would also help render the bomb less dangerous.

Another reason why the bomb might fail to detonate with a nuclear detonation would be if the plutonium pit was missing or defective. According to the pilot the bomb he signed for the bomb did not have a vital plutonium part inside it. This lack of plutonium would be able to prevent the bomb operating.

While without seeing the bomb design and knowing the exact state of it right now, I think that the bomb is not very likely to explode without some form of human intervention. For the Daily Mail to print an article claiming that this bomb could create a vast tidal wave which could wipe out Savannah is in my view an unreasonable claim unless the Daily Mail can argue a good case that this bomb is still viable.

I think that the Daily Mail may well be publishing an alarmist article.

Ammonia leak

Dear Reader,

It has come to my attention that an ammonia leak has occurred in the UK at a beer factory. This site was the Carlsberg brewery in Northampton.

Some of my readers might want to ask what is ammonia, well ammonia is the most simple hydride of nitrogen. It is a molecule with a sp3 hybridized nitrogen. The nitrogen has a trigonal based pyramidal geometry.

The three hydrogen atoms are at the bottom (base) of the pyramid while the nitrogen lone pair is at the very top of the pyramid.

DNPH (Brady’s reagent)

Dear Reader,

It has come to my attention that at a series of schools Brady’s reagent (2,4-dinitrophenyl hydrazine) has been stored incorrectly, this is an orange solid which should be stored wet with water to prevent explosions.

2,4-DNPH is a very useful reagent which is used to convert aldehydes and ketones into yellow crystalline derivatives. The nitro groups on the benzene ring help make these compounds nice and crystalline. As a student I recall the many hours we spent making and purifying DNPH derivatives when I was an undergraduate at Imperial College. I recall once having to make a derivative and then recrystallize it to a constant melting point.

The great problem appears that some years ago the use of DNPH in schools was scrapped, then old bottles of this compound were left to gather dust and dry out. These bottles were later found and then as a result the police and even the military have been called out to dispose of them.

Some of you might wounder what 2,4-DNPH looks like, here is a picture of the compound. N. Okabe, T. Nakamura and H. Fukuda in Acta Crystallogr.,Sect.C:Cryst.Struct.Commun. volume 49, page 1678 reported the crystal structure of this compound in 1993. Here we can see a picture of the molecule.

bradysreagent

The molecular structure of Brady’s reagent

Now lets look at it, the nitrogen with only one hydrogen has a trigonal planar geometry while the other nitrogen bearing hydrogens (white balls) has a distorted trigonal based pyramid geometry. This is an important difference, the trigonal flat nitrogen is likely to be sp2 hybridised. The lone pair on it is clearly part of the extended pi system formed by the benzene ring and the nitro groups (groups made of orange [oxygen atoms] and blue balls [nitrogen atoms]). The black balls are carbons while the white tiny ones are hydrogens.

The other hydrazine nitrogen looks to me like it is sp3 hybridised.

Nuclear panic

Dear Reader,

It has come to my attention that in Austria a series of schools were evacuated following the discovery of a “hot rock”, a person named Thomas Neff found a rock with a GM (geiger) counter which was emitting what he regarded as a lot of radiation. It has been reported that this rock was a lump of uranium.

Now I am trying to find out what is happening, Thomas Neff does seem rather hard to find, I have found that a person with this name works at MIT. I have also noticed that another person with this name exists in Germany. It appears that the name Thomas Neff may be a very common name, which can result in confusion.

If any of my readers can put me in touch with the right Thomas Neff, I would be glad to discuss with him the facts of this case.

Now I thought the estimate of 210 mSv per year was rather high, now we should consider how much radium-226 is required to deliver this dose. I have chosen this radionuclide as it is the daughter of uranium which will deliver (with its daughters) the vast majority of the gamma dose from uranium ores.

210 mSv per year is 5.75 microSv per day. Which will work out as 24 microSv per hour.

As one curie of radium-226 and its daughters will deliver 0.79 rads per hour at one meter, this will be 7.9 mGy per hour. Now we can calculate that to get a dose rate of 24 microGy per hour will require 329 times less radioactivity at a distance of 1 meter.

As the half life of uranium-238 is 4.468×109 years, then 3.04 mg of radium will exist in 8830 grams of uranium.

This is because after a long time the rate of decay of the radium (half life of 1620 years) will be equal to the rate of the decay of the uranium. For every Bq (disintegration per second) of uranium-238 there will be 1 Bq of radium-226.

I think that such a lump of uranium ore is rather difficult to obtain. Also the self adsorption of radiation by the ore will greatly reduce the dose per hour near to it. I think that this is a rather unlikely rock.

Now if we consider the idea of a rock which is kept at a distance of 20 cm in a band and that the 210 mSv dose per year is a hand dose then 25 times less uranium ore is needed. This will still be 353.2 grams of uranium. This is a lot of uranium, it is a bit more like a paperweight than a stone which I expect to be displayed in a school.

I am trying to get hold of the people who did the radiometric measurements on the uranium stone, right now it looks like it would be difficult to get this radiation level from natural uranium. If I get more information I will give you an update. Bye for now.

Gd in wastewater from MRI

The article about gadolinium contrast agents (Anthony King) reminded me of the case of Harold McCluskey who after an accident at Hanford absorbed a large amount of americium and was treated with DTPA. This case from the 1970s is interesting to compare to the contemporary gadolinium cases. One common Gd contrast agent is the Gd complex of DTPA which is known as gadopentetate. 

While many of the documents regarding gadolinium I have read have concentrated on bone and brain, I know that after a large intake of americium that it is important to prevent the americium depositing into both the liver and the bones. It would be interesting to find out if any studies on Gd in the liver have been conducted. While americium will deliver a dose of alpha radiation to the liver the action of the gadolinium will be purely chemical, this change of element and properties may alter the list of organs which are of interest after an intake of Gd.

I saw an interesting paper by F.G. Shellock and E. Kanal which included the idea of zinc displacing the gadolinium from things like diethylenetriaminepentacetate (DTPA), others have worked further on this issue. I know that after an intake of either americium or plutonium into a cut that the treatment is injections of calcium diethylenetriaminepentacetate in the first days, after a while it is normal to change to zinc diethylenetriaminepentacetate as treatment with the calcium salt tends to strip zinc out of the person.

One interesting thing, the chemistry world article considered in a very shallow way the form of the gadolinium. As the gadolinium in the DTPA complex will tend to exchange with zinc the gadolinium will be released from the ligand. When I checked the f1 value for gadolinium is very low (0.0005) when I checked a ICRP document (ICRP PUBLICATION 119 Compendium of Dose Coefficients based on ICRP Publication 60). The F1 value is the fraction of an element which will be absorbed into the blood stream if it is swallowed. It is a measure of how bioavailable an element is. It is important to understand that some variation of F1 fraction will occur from person to person and it will also change when the chemical form of an element is altered. But it is an important thing to be aware of.

For example the F1 value for cesium is 1.0, for copper and zinc is 0.5 while the value for gallium is 0.001. The value for the elements which form the more highly charged ions tends to be lower. If we consider the series cesium (F1 =1), barium (F1 = 0.2) and lanthanum (F1 = 0.0005) we can see that F1 decreases as the charge of the cation increases. There are some elements which buck the trend such as germanium (F1 = 1.0) but in general the elements which form highly charged cations are poorly absorbed by humans. In particular plutonium (F1 = 0.0005) is very poorly absorbed by adults. For small children the F1 value is slightly larger at 0.005).

As a result I do not expect the gadolinium to pass into humans as a result of eating fish or other things which live in the water.

What is chlorine

Dear Reader,

After the recent event in Kansas, some of my readers might want to know what chlorine is. Well chlorine is one of the elements of the periodic table, it is a green / yellow corrosive gas but like many things the form of it controls how good / bad it is for you.

In the form of the element it is toxic to all lifeforms, but in the form of common salt (table salt) which has the chemical name “Sodium Chloride” it is a vital substance required by people in their food (in moderation) and for many household and industrial processes.

Before you get too concerned by the fact that chlorine is toxic to all forms of life, consider for a moment how you would rather not have live germs in your drinking water, a small amount of chlorine added to drinking water will kill the nasty germs. The small amount of chlorine in the tap water is not dangerous to people but please take care when you add water to your fish tank to treat it with a chlorine neutralizer. For many substances a human, plant or animal can tolerate a small amount each day. For example if I was to drink a tea spoon of gin each lunch time then it would have no adverse effect on my health. even if I continued in this habit for the whole of my life. On the otherhand if I saved all my lunch time gin up for several years and then drink it in one afternoon then I would be a very bad way.

I know in the past some people have regarded chlorine as the devil’s element, I think that this is rather silly and unscientific. <Sarcasm>Anyway I thought that the devil’s element was sulfur </Sarcasm>. But seriously if anyone tells you that chlorine is the devils element and must be banned you should reject this statement, I always used to say I will take that idea with a pinch of salt.

Chlorine is needed for a wide range of industrial and household products but sadly in recent years it seems to have become a bug bear for the environmental movement. For example Greenpeace have wasted a lot of effort and time going on and one about the evils of PVC. They seem to hate the stuff. You might be interested to know that some of their horror stories about PVC and chlorine chemicals have been debunked by the chlorophiles.

I hold the view that PVC is a very useful plastic, it is very good and safe in many applications and normally it is some of the additives which are the real problem.

For example PVC water pipes and uPVC window frames are perfectly safe, but on the other hand I would not want to store a fatty food in a container made from some grades of soft PVC. This is because I would rather not ingest some of the additives such as some of the pthalates in my food.

It is interesting that in recent times people have become scared of plastic food containers, for example on Mumsnet there is a recent thread about this topic. Now I would say we need to be careful about “all vs some“. While some grades of plastic are not safe for food containers, for example I would never buy a olive oil processing machine in which the oil was heated in an ABS container which contained small molecule flame retardants, I would be perfectly happy with a olive oil machine which used polypropylene instead. This is becuase polypropylene is a polymer which is normally free of the hazardous additives.

Other plastics which should be very food safe will include polyethyene, PET and polylactic acid.

Chlorine accident in Kansas

Dear Reader,

It has come to my attention that an accident has occurred in Kansas in the USA at a distillery (MGP ingredients) which makes alcoholic liquors according to CBS. Now some of you might be asking what is chlorine, what is sodium hypochlorite and what is happening.

Now some of the reports are rather alarming, for example at Reuters the gas cloud was described as being like mustard gas. Now this is a rather alarming and odd statement. Mustard gas and other strong alkylation agents such as trimethylsilyl diazomethane do not strongly irritate the lungs or other parts of the body at the time of exposure, they tend to cause effects hours after exposure. The idea of mustard gas as a chemical weapon is that it gives no strong warning signs to a person, so that they can absorb a dangerous amount and then later the effects start. Thus by the time anyone notices any symptoms it is too late to take action to prevent damage by ending the exposure.

Here is a diagram of sulfur mustard which is the original mustard gas used in world war one. There are some related mustard gases but this is the original and most common one. Its NATO code is HD.

sulfurmustard

Chlorine is a substance which will irritate the eyes, lungs, mouth and other organs at the time of exposure. Chlorine is a general tissue wrecker which can cause serious lung injuries which can result in death. But the way that it acts is very different to mustard gas. Mustard gas is an alkylation agent which can crosslink DNA, proteins and other biomolecules. I also hold the view that chlorine gas has far less potential to act as a carcinogen (cancer forming agent) on humans.

Now what is sodium hypochlorite, it is commonly sold as a dilute solution for use in the home for cleaning toilets. It is known as chlorine bleach. The substance is made by the reaction of chlorine gas with cold dilute sodium hydroxide solution according to the following equation.

Cl2 + 2NaOH → NaCl + NaOCl

When chlorine gas is bubbled into water then it reacts in a reversible reaction which is shown below.

Cl2 + H2O → HCl + HOCl

The HCl is a strong acid (hydrochloric acid) and the HOCl is a weak acid (hypochlorous acid). So by using a sodium hydroxide solution the forwards reaction is favoured as the acids lose their protons in deprotonation reactions forming the two salts (sodium chloride and sodium hypochlorite).

Now when the sodium hypochlorite solution was mixed with sulfuric acid then the sodium hypochlorite was converted into the free acid again. This would have formed HOCl which is able to react with the chloride anions present in the bleach to form the chlorine gas which escaped from the plant. There are other things which one should not do with chlorine bleach other than mixing it with acid, maybe another day we can discuss these things.

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