AW: [ RadSafe ] False alarms: was: NYC permitting of detectors, Grand Canyon

Franz Schönhofer franz.schoenhofer at
Mon Feb 11 16:43:28 CST 2008


I really appreciate your very clear, simple and convincing calculation -
with one exception: Your hypothetical assumption of one nuclear WMD (nuclear
bomb) per day moved around in NY-City, which would mean that since Sept. 11
many thousands of nuclear bombs would have to be transported in NYC!!! Are
there enough bombs available on the black market? So the relative number of
false alarms (percentage) would actually approach infinity even under your
partly theoretical assumptions. 

All the infrastructure you mentioned (in man-hours, which is of course not
politically correct - shouldn't it be person-hours?.....) is another
interesting question. 

Sorry, my answer was delayed, because there was a very interesting and
beautiful film on TV about the Grand Canyon - I have been there several
times, partly together with my family. Last October I had not enough time
for another visit because I spent about three weeks in the more eastern
parts of the South-West. So much from an "anti-US European"!

Best regards,


Franz Schoenhofer, PhD
MinRat i.R.
Habicherg. 31/7
A-1160 Wien/Vienna

-----Ursprüngliche Nachricht-----
Von: radsafe-bounces at [mailto:radsafe-bounces at] Im Auftrag
von Clayton Bradt
Gesendet: Montag, 11. Februar 2008 13:28
An: radsafe at
Betreff: [ RadSafe ] False alarms: was: NYC permitting of detectors

Steve Dapra wrote:

"I do not know how many false alarms 
have been answered..."

If a True Positive is taken to be 
detection of a WMD, then we know that 
all of the alarms have been false.  
Since on any given day there are about 
10,000 people in NYC that have had a 
nuclear medicine procedure within the 
past ten days (20,000,000 nuc med 
studies per year in the US prorated to 
population of NYC) and therefore likely 
to set off a police pager, if we assume 
one radioactive WMD plying NYC streets 
daily - then the positive predictive 
value of a positive detect by a police 
pager is about 1/10,000.  For every 
10,000 false alarms each day, there 
would be one True Positive.  That's 170 
man-hours daily just resolving false 
alarms - if we assume just one minute 
is required to resolve each false 

The number of false alarms generated 
by the police themselves is 
overwhelming.  A few additional ones 
from civilians would be 
inconsequential, even if they were 
reported to NYPD.  

The irony is that the civilians using 
radiation detectors are in general far 
more knowlegable in health physics than 
the cops carrying pagers, and so 
unlikely to mistake a false positive 
for a WMD.

Clayton Bradt
dutchbradt at
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