I hear that Radioactivty is both a Spontaneous and Random Process, what do the two terms mean? Is there a difference? Can we therefore make the radioactive isotopes non-radioactive by chemical reactions etc.?
Yes, radioactivity is both a random and spontaneous process. Let us explain what it first means to say that it is a "random" process and then talk about the "spontaneous part.
Random Process:
By random, we mean that for a sample of radioactive isotopes, we do not know at an instant of time which one will decay. It also means that when we select a particular atom, we do not know when it will precisely decay.
What is however associated with this process is a probability of decay and that is manifested as what is known as half-life of the sample.
Beyond the scientific community, it is a common misconception that the half-life of a sample determines the time it takes for it to become non-radioactive.
This is not true, it is only the time taken for it to decay to half its initial activity. (by layman terms that may be the amount of radiation emitted per unit time.)
In the case of nuclear waste from nuclear fission power plants, it becomes rather complicated, as the waste product consists of many radioactive isotopes, some ranging to short half lives ( e.g. Iodine-131 ~ 8days) to extremely long half lives ( Tc-99 ~ 220,000 years and I-129 ~ 17 million years).
There are problems in dealing with the shorter half lives radioactive isotopes and longer radioactive isotopes. In general, the short-lived ones though having a short half live decays rapidly, also emits alot of radiation and that tends to generate alot of energy. This is why in the case of the nuclear accident at Japan, though there are some spent (used fuel ) continuous cooling is needed to bring the temperature down.
For the case of the isotopes with long half-lives, the activity is smaller but the impact is for a longer period of time, with half lives of 220, 00 years and even million years, this means the radioactive substance will still be emitting radiation many, many years after we have gone. Proper disposal and storage of these waste will therefore be needed as well.
Spontaneous Process:
Understanding the spontaneity part will also help understand why we cannot just destroy or hasten or slow down the radioactivity of the radioactive isotopes. Radioactivity comes about because the isotopes are energetically unstable and they try to achieve stability by emitting radiation. It is termed a spontaneous process, as its activity (decay) is unaffected by external pressures, temperatures or any chemical processes. You need time to just let it decay and to come to a stable state.
This is why we also cannot just add chemicals, heat the spent fuel and to treat it to make it safe. You need proper containment procedures to keep it away from possible risks of contamination.
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| Officials in protective gear check for signs of radiation on children who are from the evacuation area near the Fukushima Daini nuclear plant in Koriyama, March 13, 2011. Japanese Chief Cabinet Secretary Yukio Edano confirmed on Saturday there has been an explosion and radiation leakage at Tokyo Electric Power Co's (TEPCO) Fukushima Daiichi nuclear power plant. The biggest earthquake to hit Japan on record struck the northeast coast on Friday, triggering a 10-metre tsunami that swept away everything in its path, including houses, ships, cars and farm buildings on fire. (Kim Kyung-Hoon/REUTERS) |
Other Relevant Links:
(1) On Nuclear Physics Part I : What is Radiation? Does a person continue to radiate radiation after he has been irradiated?
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