How Everything Works
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Question 793

Radioactive elements' half-lives are fixed and they decay at a constant rate. Their decay rates have been determined thanks in part to our nuclear weapons research. Under what circumstances can a radioactive element have its decay rate changed? Can the element's radioactivity be destroyed (cancelled) by applying high temperatures? If so, how high would the temperature have to go to achieve this? — RD, Humble, TX
Since radioactivity is a feature of atomic nuclei, the only way to alter radioactivity is to alter atomic nuclei. But there aren't many ways to change atomic nuclei. Of various atomic and subatomic particles, only a neutron can enter a nucleus easily and cause it to rearrange. However, it's more common for a neutron to increase radioactivity than to destroy it, so that's not a good approach. Furthermore, the only practical way to obtain neutrons is with radioactivity.

Heating a collection of nuclei can cause them to collide and rearrange. However, this process is also fraught with problems. The products of the fusion and fission events that occur when nuclei collide will probably be radioactive themselves, so that it's unlikely that heating radioactive materials will make them less radioactive. Instead, it's likely that heating radioactive materials will make them more radioactive. Furthermore, the temperatures at which nuclei will begin to collide are extraordinarily high. Even the smallest nuclei repel one another fiercely so that they need temperatures of 100 million degrees C or more to begin colliding effectively. Larger nuclei, such as those common in nuclear wastes, won't collide until their temperatures exceed 1 billion degrees C. The only way to reach these temperatures is with nuclear weapons and they certainly don't reduce the radioactivity of nearby materials. In short, the only way to get rid of radioactivity is by waiting patiently.


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