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/ | `------------------------------------------------------------------' Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=5691