Paranoid fixations of anti-nukes

Nothing suggests mental illness more than the tortured reasoning used by anti-nuclear activists to attempt to justify their positions.  Often they fixate on particular claims which turn out to be utterly ludicrous after even shallow examination.  One of these is the argon-41 chromosome-damage "theory" currently being flogged by BasG (Bas Gresnigt) over at Atomic Insights.  This short-lived isotope (half-life 106 minutes, beta-decaying to stable potassium) is a noble gas, and disperses rapidly in air by diffusion and turbulent mixing.  The "researchers" who tortured their data to make it confess the crimes of ⁴¹Ar got it to sign a statement amounting to this:

1. Spent nuclear fuel emits neutrons due to spontaneous fission.
2. The neutrons escape into the air and run into ⁴⁰Ar atoms, forming radioactive ⁴¹Ar .
3. ⁴¹Ar ionizes due to recoil from the neutron capture.
4. The ion is attracted to dust and water particles, keeping it close to the ground after formation.
5. Because of this, the effects of ⁴¹Ar are most strongly felt upwards of 20 km from its point of formation, rather than immediately next to it.
6. The measurable effect is an increase in the male-female sex ratio at birth, because the X chromosome has more DNA than the Y chromosome and is more susceptible to damage.

Got that?  I lost 5 IQ points just from reading the crap required to write that summary, so I'm not going to repeat it.  Oh, the "researchers" conveniently left out the mechanism by which ⁴¹Ar singles out the sex chromosomes for damage, rather than causing mutations and consequent birth defects all over the genome.  It's just one of the ways that ⁴¹Ar is evil, I guess. 

Back in reality, things are just a little bit different.

Argon is only a trace constituent of air.  Nitrogen is 78% of air by volume, while all isotopes of argon are only 0.93%.  Further, each molecule of nitrogen has two atoms while argon has but one.  Last, the thermal neutron capture cross-section of nitrogen is 1.91 barns, while argon's is only 0.675 barns.  The upshot is that a free neutron in air is about 470 times as likely to be soaked up by a nitrogen atom (forming stable ¹⁵N ¹⁴C by the (n,p) reaction) than by ⁴⁰Ar.  My understanding is that even that's not terribly likely, and the most common fate of neutrons in air is beta-decay to hydrogen (half-life ~11 minutes).

But let's follow this to the end.  ⁴⁰Ar plus a free neutron have a total mass of 40.9710480385 AMU.  ⁴¹Ar masses 40.9645006 AMU, for a difference of 0.0065474385 AMU or on the order of 6 MeV.  This will be released as a gamma ray.  This is certainly enough to ionize an atom... but is it likely to stay that way?  The ionization energy of argon is 15.7 electron-volts (eV).  The ionization energies of both nitrogen and oxygen are less than that, so at the first collision with an oxygen or nitrogen molecule the newly-formed ⁴¹Ar⁺ ion is going to steal an electron and not be an ion any more.  That will take on the order of picoseconds.

Last is the issue of location of the decay.  The typical human contains enough potassium that the beta decay of ⁴⁰K occurs around 4000 times per second; against this background of beta decays, you'd have to have a huge effect from ⁴¹Ar to measure something.  But even if an atom of ⁴¹Ar was able to stay ionized, attach to a dust particle or water droplet, and stick around near a human, what is the likelihood that it could be ingested and migrate to the gonads before it decayed?  Roughly zero.

The funniest thing about this ⁴¹Ar "theory" is that there are actually people who take it seriously.  So who's pushing this nonsense?  There are two basic possibilities here, not necessarily mutually exclusive:  either they are objectively deluded (crazy), or they want you to be.  The latter want to panic you into following their agenda, which you wouldn't do by pursuing your own interests.  And that, my friends, is evil.

Note:  Corrected the results of neutron capture in nitrogen, H/T rrmeyer.

Edit:  corrected notation.  ¶ 10/11/2015 01:39:00 PM