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Home made nuclear reactor part II

Dear Reader,

I was going to tell you some more about crystals and crystallography but that will have to wait for a while. Instead I am going to tell you some of what I think about garden shed nuclear experiments. In case you have come here hoping to read how to make your own reactor, then I have to apologise and tell you that for a series of reasons (including security reasons and a lack of time/space here) it is not possible for me to give you a how to guide to build a reactor in the space we have today.

The way that David Hahn and the Swede were discovered were very different. David gave himself a fright and then in his panic he attracted the attention of a random policeman, while the Swedish man wrote a letter to SSM asking if it is legal to build nuclear gadgets at home. Before we go any further I would like to stress that almost all nuclear and radioactive activities and equipment are regulated by criminal law in all the countries I have heard of. The IAEA have said publicly that they want the penalty for the illegal possession of some nuclear materials to be as high as murder, so we are dealing with “serious stuff” here!

David Hahn wanted to breed uranium-233 which is fissile from natural thorium-232 which is not fissile but just fertile. Fertile means that an isotope can be converted by a simple nuclear reaction into an isotope which either is (or decays into) a fissile isotope.

What David did was to burn up a large number of gas mantles to obtain thorium oxide; he then cut up a large number of lithium batteries to get the lithium. Then using the lithium he converted the thorium into the metal. I think that this was never needed, many reactors using metal oxides as fuels or as targets for radioisotope production. While neutrons can react with oxygen to form radioisotopes such as nitrogen-16 (by a np reaction) this is normally not a major problem.

David then tried to bombard his thorium with neutrons which were from a homemade neutron source. He used a combination of radium-226 and beryllium. This is a horrible mixture; the radium is properly one of the most radiotoxic isotopes in the world while the beryllium is the most toxic non-radioactive element. It causes a series of horrible diseases including a horrible lung rotting disease!

Radium-226; Properly the nastiest radioisotope in the world!

When David was doing his experiment he noticed that the radioactivity level of the thorium target was increasing, this increase in radioactivity prompted him to get into a bit of a panic. What was likely to be happening was during the pyrochemical processing of the thorium dioxide he would have separated the radium-228 and radium-224 from the thorium. These two radioisotopes would have then started to reappear because of the alpha decay of the thorium-232 and thorium-228.

When I get around to it I will plot some graphs of the radioactivity levels as a function of time in a sample of thorium which has been purified. But that will have to wait for another day.

The Swede was spotted in a different way, he wrote a letter to SSM asking for legal advice regarding his home made reactor. I have read the reactor builder’s blog and he does seem to be having some trouble with some concepts.

I am doubtful that even if he had been left to get on with his experiments that he would ever have managed to get his reactor to work. From the little information I have obtained from his blog it looks like he was trying to build a similar gadget to David’s one. It looks like he wanted to build a subcritical reactor which would be driven by an external neutron source.

He describes how he wanted to dissolve radium in 96% sulphuric acid, I think that this was a bad idea for several reasons. Firstly radium is horrible and radiotoxic, while secondly radium sulphate is very insoluble. One of the classic ways to extract uranium is to boil up uranium ore in sulphuric acid, the uranium dissolves while the radium together with the barium will form an insoluble sulphate. For those of you reading in America sulphate = sulfate, and sulphuric acid = sulfuric acid.

I have written some more about barium and radium sulphate, if you want to read about how it applies to this case then go here.

Then the mixed barium/radium sulphate is dissolved, I think in the interests of public safety I will not tell you how to do it here!

So the choice of reagents for the dissolution of the radium was a poor choice, I have also noticed that an ash tray was close to the cooker. I know that you all know that smoking is a dirty habit but smoking anywhere near radium is a very dirty habit. The problem is that in a radium contaminated environment such as an old uranium mine that the air contains radon-222. This ‘evil creeping death gas’ might be able to diffuse through rocks into caves and houses. But the real villain is the polonium-218 and the other radon daughters. These tend to stick to dust and smoke particles.

If you were to breathe radon contaminated but totally dust free air then it would not be good for you but compared with smoke mixed radon daughters the dust free radon air is positively health giving! What happens with tobacco smoke is that the particles get coated with the radon daughters and then they stick in the lungs. The smoke thus acts like glue to stick these nasty alpha emitters into the lungs. As a result a combination of smoke and radon has a far greater baneful effect on the lungs than the sum total of the two if they are done separately in time and space.

Before you are inclined to feel sorry for the Swede bear in mind that while he did stop to ask if home made reactors were legal, he did not think to ask until he had already started his experiments. I suspect that if a random person in Sweden was to write a letter to SSM asking if it was legal to build a nuclear reactor in the basement, then they would get investigated. But if the person had neither acquired nuclear/radioactive materials nor had started to try to build a reactor then they might at worst get their home searched, but I think that after a stern warning that SSM would send him on their merry way.

I do not quite know what the text of the warning would be but maybe the following might be a good one

The unauthorised construction and use of nuclear reactors in the home is dangerous and may result in a large fine or lengthy imprisonment. I strongly suggest you take up some alternative recreational activity such as …………..

I once had my lab inspected by a team of UN inspectors who wanted to check that I was not doing some undisclosed nuclear activity in my lab. I found the UN inspectors to be a courteous and professional group of men. What they did was to look in my lab at what sort of equipment I had, they wanted to ask me what sort of chemistry I was doing and to take a gamma spectrum to check what sort of radioisotopes were present in my lab (They found nothing as I have next to no radioactivity in the lab).

While I have no experience of being investigated for illegal back street nuclear reactor operation, I suspect that SSM might use similar tools such as the portable gamma spectrometer to check what radioisotopes were present in the man’s flat. I would also expect them to take some samples in the form of wipe samples to allow for different tests to be done later. One option would be to use an alpha/beta scintillation type contamination meter to search the surfaces in the man’s flat for hot spots of activity. When a hot spot is found it would be logical to sample it and then use a more sensitive and selective counting method to evaluate the sample.

12 Responses

  1. [...] he’s done with experiments and will stick with theory instead. [HD.se and Harpers and AP and Mark Foreman] You can keep up with Kelly Hodgkins, the author of this post, on Twitter, Google + or [...]

    • He was Swedish and not Swiss.

      Also bear in mind that potassium iodide pills are not a cureall for all radiological ills and horrible things. Beware of people trying to sell you potassium iodide, it is not needed now in Japan (date now 4th August 2011) as the iodine has decayed away.

  2. [...] færdig med eksperimenter, og vil holde sig til teorien i stedet. [ HD.se og Harpers og AP og Mark Foreman ] Du kan holde op med Kelly Hodgkins, forfatteren af dette indlæg, på Twitter , Google eller [...]

    • I’m blind, so trying to get anywhere in this blog is problematic. I want to ask Mark Foreman a question, not surf about in stupid replies. The question relates to David Han’s using lithium in his attempt to make pure thorium. In the book, it states that the lithium strips boiled with the thorium oxide ash became thorium, and the ash became lithium oxide. Something about this bothers me, chemically. It seems more likely that the oxygen would move to the lithium strips, leaving lithium powder or ‘ash’, and strips of lithium oxide. What am I not ‘seeing’. PS. I use JAWS screen reader on my PC to access and read text on the web. Sometimes, this leave much to be desired. So, if, say, I did put a lithium strip and thorium dioxide ash into an aluminum pouch in cooking oil and heated it, would anything actually happen? That too seems unlikely.

      • I will get back to you as soon as possible, you have asked an interesting question.

        The chemistry which you want to know about is similar to the thermite reaction, I will explain shortly what happens and why it happens.

      • I have written an answer which explains what would happen if you heat lithium metal and thorium dioxide.


        If you were to heat up cooking oil and lithium then it is likely that the ester groups in the oil would react with the lithium metal in an acyloin reaction.

  3. [...] he is done with experiments and will stick with the theory instead. [HD.se and Harpers and AP and Mark Foreman] Tagged:nuclear [...]

  4. This is really interesting, You’re a very professional blogger. I have joined your rss feed and sit up for searching for extra of your fantastic post. Also, I have shared your site in my social networks

  5. Dear Professor Mark Foreman,

    I am actually working on “Atmospheric Dispersion modeling” of radionuclide release from a research reactor during an hypotheticalaccident:
    1/ I am interested on 3 radionuclides only: Cs-137, I-131 and Sr-90 because of their high toxicity
    2/ I need to write the differential equations for fuel isotope changes, for the 3 radioelements, and solve them, using general solution of Bateman equations for nuclear transmutations. But the these serial decay chains are long, and confuse me a bit. How can it be done, taking into account their production and removal rates?
    3/ Then I will try to write a Code in Fortran for the computation and analysis of fuel burnup.
    4/ The activity generated will be now converted to dose and atmospheric dispersion modeling of these radionuclides release will be used based on site-specific meteorological data to calculate the dose downwind a receptor location, after defining initial events of accident occurrence.

    Actually, the point 2/ is the reason of this post and I need your comments/suggestions on it!

    • 1. I would consider more than just I-131, Cs-137 and Sr-90. The other shorter lived iodines may be a greater threat under some conditions than the I-131. Also in power reactor fuel the Cs-134 is important, this is an activation product formed from Cs-133.

      2. Some codes already exist for working out the isotope signature of fuel, look for the ORIGIN and BURNUP codes.

      • Thanks for the reply.
        I saw the existing codes, but actually, I am in a situation where they are not readily available to me. So I thought of solving the problem by calculating the change in isotropic concentrations myself through the application of Bateman type equations and write a small code in Fortran. I saw a similar work done for (U-235, U-236, U-238, Pu-239, Pu-240, Pu-241). Simple in this case because U-235 and U-238 are used as parents. But for the fission products I mentioned (including I-134 and Cs-134, etc.), I wonder if, in the isotopic transmutation equation, I should start with what isotopes as parents, whilst they all are fission products of U-235/U238 parents!
        These are some challenges we face when there is no access to the state-of-the-art technology. I hope you will not mind my asking!

      • Second reply to Jeremie,

        Well I have some things which you might want to consider,

        I know the man who wrote BURNUP, some time ago he told me about some of the features of the code. One of the key problems is that the neutron cross sections for the formation of nuclides by fission and neutron activation change as a function of neutron energy. As a result it is not correct to use a single neutron energy or cross section for each nuclide. What you need to do is to consider each parent nuclide at different neutron energies.

        Also the quaility of the neutron cross section data may have an impact on the quaility of the final results.

        I think that by making the code consider the different neutron energies that the size of the code and the array size will become much larger.

        Also have you considered the fact that a typical reactor is not homogenous, it has fuel pellets in which fast neutrons are formed, these enter the water and slow down before reentering the pellets. How are you going to model how well the moderation works ?

        If you are writing a code for LWR and CANDU systems then I would like to know if you have considered tramp uranium. Due to damaged fuel and the trace of uranium in the water added to the reactor you always have a little bit of fission in the moderator. This will give you a second source of short lived iodines in the fuel under normal operation. In the case of a element which has both long and short lived isotopes it is possible by looking at the isotope signature to work out the age of the element. I suspect that as a LOCA progresses that the age of the iodine in the water could do something odd as a result of this effect.

        I have to confess that I have very little experience of writing such codes, but I wish you luck.

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