X-Message-Number: 5691
From: Joseph Strout <>
Newsgroups: sci.cryonics
Subject: Re: Cryo-risks
Date: Tue, 30 Jan 1996 08:03:02 -0800
Message-ID: <>

On Jan. 19, Charles P. Schultz wrote:

> "CryoSpan...employs multiply redundant, fail-safe computer monitoring of 
> liquid levels in patient dewars that are situated in reinforced-concrete 
> underground vaults."
> 
> - Is "fail-safe" meant to imply "defect-free"?

I'm not with CryoSpan, but I think it is generally understood that 
fail-safe does not mean defect free.  Rather, it means that the most 
likely modes of failure result in conditions that are still "safe".  In 
the case of an alarm system, it would mean (for example) that the alarm 
goes off if the power is lost or the computer fails, so that somebody can 
come check it out.

> Are these
> reinforced-concrete underground vaults as good as the sometimes-leaky ones 
> used to store nuclear and other hazardous waste? 

Leaks aren't a serious issue in this case; it would just mean a slightly 
faster rate of nitrogen replacement (the leaks would probably be small 
compared to boil-off).  We don't (presumably) need these things to last 
50 thousand years, they will be actively maintained, and if LN does leak 
into the environment, it causes no harm (i.e. it's not hazardous).

> > [Dewars safe from vandalism & natural disaster]
> - What about power outages? Communications cables chewed through by rodents? 
> Faults due to inadequate workmanship, such as coolant leaks?

These are legitimate concerns, but not as worrisome as the natural 
disasters to which the brochure was referring.  If there's a power outage 
or a leak, the patients are perfectly safe for many hours (someone give 
me the exact figure -- I think it's in the range of 12-36 hours).  In 
that time, the company can bring in more LN by truck, in essentially 
whatever quantities are needed to keep the patients submerged.  On the 
other hand, if there were a facility-destroying disaster such as a quake, 
fire, or bomb, then the patients would be almost instantly lost.  So, 
IMHO, the company has quite rightly focussed their efforts on preventing 
*disasterous* failures, and put less effort on the merely annoying ones.

,------------------------------------------------------------------.
|    Joseph J. Strout           Department of Neuroscience, UCSD   |
|               http://www-acs.ucsd.edu/~jstrout/  |
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