Iodine 129, the Elephant in the room.

[formercia]

--snip--

129I decays with a half-life of 15.7 million years, with low-energy beta and gamma emissions, to xenon-129 (129Xe).

129I is one of the 7 long-lived fission products that are produced in significant amounts. Its yield is 0.6576% per fission (U-235). Larger proportions of other iodine isotopes like 131I are produced, but because these all have short half-lives, iodine in cooled spent nuclear fuel consists of about 5/6 129I and 1/6 the only stable iodine isotope, 127I.

Because 129I is long-lived and relatively mobile in the environment, it is of particular importance in long-term management of spent nuclear fuel. In a deep geological repository for unreprocessed used fuel, 129I is likely to be the radionuclide of most potential impact at long times.

--snip--

http://en.wikipedia.org/wiki/Iodine-129

[catbyte]

1. Yikes! And I thought plutonium was bad

with a half life of 24K years. Things aren't looking good on Planet Earth. Mother Earth is going to rise up and kick us all in the ass, as well she should.

:scared:

Diane
Anishnabe in MI

[autorank]

6. GE brings good things to light! n/t

[WestSeattle2]

2. Why in the world are we messing around with this stuff?! The

fact that we are blows my mind. Does anyone know if we have to engage in this risky process in order to have nuclear medicine?

[BobbyBoring]

9. Population Control??

Just askin?

[Igel]

10. Yes.

Without something very much like this we could not have nuclear medicine.

For what it's worth, there are two other isotopes of iodine that they actually use. (I-129 has such a long half-life that it's useless for nuclear medicine. Not nearly radioactive enough.)

I-131 has a half-life of about 8 days. It's what they use in, say, treating thyroid disease. Ihave had two doses to get my Graves disease knocked back on its heels.

I-127 (IIRC, I could have the mass wrong) has a half-life of only a day or so. They use it as a tracer, in absurdly small amounts, to measure iodine uptake in order to calculate the right dose of I-131.

[Name removed]

3. Deleted message

Message removed by moderator. Click here to review the message board rules.

[hootinholler]

4. This would probably do better in GD. k&R n/t

[caraher]

5. The role of half-life is widely misunderstood

On one hand yes, a long-half life means that a given quantity of that nuclide remains radioactive longer than one with a shorter half-life. At the same time, it is much less radioactive for a given number of nuclei.

This is because radioactivity is the number of decays per unit time. So if you put equal numbers of I-129 and I-131 nuclei under your pillow, the I-131 is going to give you a much larger dose of radiation because essentially all the nuclei will decay over the course of a few months whereas almost no I-129 nuclei will.

For the mathematically inclined, radioactivity (decays per unit time, as measured in a suitable unit like Becquerels) is proportional to the number of nuclei divided by the half life. A sample of N I-129 nuclei will be 8 days/15.7 million years as radioactive as the same number of I-131 nuclei; that's a factor of almost a billion less radioactivity.

The radioactivity levels for the two isotopes in this hypothetical sample would become the same after 29.4 I-131 half-lives, or about 235 days. After that, the radioactivity would be dominated by the I-129; but the level would be around one billionth of the original value.

[tahrir]

7. National Academy of Sciences Requires Industry to Ensure Nuke Waste Safety for 1 million years

The NAS report had recommended standards be set for the time of peak risk, which might approach a period of one million years

http://en.wikipedia.org/wiki/Nuclear_Waste_Policy_Act



FYI

[Paradoxical]

8. It's extremely faint in it's radioactivity.

You cannot just look at half-life and expect to understand radioactive decay of the product.