Quote:
Originally Posted by wodin
There are seven long lived fission products:
Technetium-99 halflife 211,000 years
Tin-126 halflife 230,000 years
Selenium-79 halflife 295,000 years.
93zirconium halflife 1,530,000 years,
Caesium-135 halflife 2,300,000 years
Palladium-107 halflife 6,500,000 years)
Iodine-129 halflife 15,700,000 years
There are also a number of radioactive isotopes created by neutron abortion, most notably several isotopes of plutonium including the nuclear weapons fuel PU239.
Neutrons are most readily attenuated by hydrogenous materials (stuff with a lot of hydrogen) like water or plastic. That is because a neutrons atomic mass is nearly the same as the hydrogen nucleus (proton) and hydrogen nuclei have a relatively cross section for scattering. Once the neutron reaches thermal equilibrium, it can be readily absorbed by something with a high cross section for absorption. Usually boron because it is cheap and plentiful.
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All of which are either Beta or Gamma producers, not neutron producers, so no tertiary radiation products. (Due to neutron absorption - i.e. no neutrons)
Excluding TC-99, Most of the rest are low yield products. TC-99 and I-129 can be "cooked" in a reactor to capture further neutrons and convert into less hazardous products.
One aspect of slow decay radioactives is just that - slow. Which means the give off very little radiation over time. For example. I-129, with a halflife of 15,700,000 years. That means that only 1 atom out of 15,700,000 will issue a beta/gamma event in a year. Radioactive - yes, but not very. it is also produced naturally in uranium ores.
Plutonium is both radioactively toxic (a nasty neutron producer that causes secondary radiation products) as well as being extremely chemically toxic. Much, much worse that the other 7 listed...