Re: Mad Cow Implications for Cryos

Date: Wed May 16 2001 - 18:18:46 MDT

Randy Smith wrote:
> So, does anyone know if the prion disease will continue to ravage the brain
> even when submerged in LN2 (or at the proposed, somewhat warmer storage
> conditions)?

You can assume the reaction and diffusion rate to be effectively zero
for all time scales but geological (where chiefest damage mechanism
will be ionising radiation). The vitrified (glass) phase should not
come within the regime when the kinetics of annealing/devitrification
will become noticeable. The real issue is not cracking -- cracking is
much, much preferable to devitrification, the limit is cryofluid
pricing. Current cheapness of LN is largely artefacted of it being a
side product of liquid air fractionation (to obtain oxygen for steel
production). Most developed countries no longer use that process (they use vacuum
electrosteel processes and since recently hydrogen reduction and sintering,
or enrich oxygen by air by means of molecular sieves if they have to), if
they haven't completely outsourced steel production to cheap, environmentally
unregulated places. So LN prices will go up, requiring a switchover to some other
cryogenics method. Both the heat lossage through walls and value of
Joule-Thompson coefficient would indicate that you'd want to stick around
-150 deg C tops, which is still perfectly fine for vitrified tissue. Of
course, you lose the advantage of phase change enthalpy, so you're in
deep shit once the power goes out. Not only have you to use expensive
cryogenics aggregates, and massive air conditioning to keep these happy,
you also have to install failsafe power generators, and rapid contingency
plans, as your safety window is only a few hours (instead of a couple of
weeks) wide. Suddenly, things are becoming expensive, complex, and brittle.
This is certainly going to have an impact on prices, reliability, or both.

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