Answer to Question #6833 Submitted to "Ask the Experts"
Category: Radiation Basics
The following question was answered by an expert in the appropriate field:
What form of radioactive thallium would have been used for poisoning such as in the case of Nikolai Khokhlov? Would it have been thallium-200? Or something else? I have looked all over the Internet and cannot find the answer. Because the effects were so dramatic I thought it couldn't have been thallium-201, but I am not really sure. Also, if you do know, would you also be able to tell me if it emits alpha, beta, or gamma radiation? I assume alpha or beta but again can't find a true answer.
So far as I am aware, following the poisoning of Khokhlov, there was never a positive identification, or at least a public disclosure, of a particular isotope of thallium as the culprit. In fact, many of the symptoms that Khokhlov suffered were consistent with stable thallium poisoning. These included abdominal pain and vomiting, hair loss (in clumps), eye problems, and some mouth and skin rashes and lesions. From what I understand, some additional symptoms that included degradation in the blood-forming system and the immune system led some American consultants to promote the idea that radioactive thallium was likely responsible.
If that were true, the most likely candidate, in my opinion, would have been 204Tl, a species that can be produced readily by neutron activation of stable thallium in a nuclear reactor. Russia's first nuclear reactor was built in 1954, so the technology was presumably available to prepare this isotope in 1957 when Khokhlov was poisoned. Thallium-204 is a pure beta emitter (maximum energy of 0.76 MeV) with a 3.8-year physical half-life. It is possible that stable thallium was treated in a neutron field to produce 204Tl, although almost all the mass of the thallium present after neutron irradiation would still have been stable, with relatively few atoms having been converted to the radioisotope.
Answer posted on 26 September 2007. The information and material posted on this website is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of materials and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Website. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.
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