[ RadSafe ] Interlock question

[JPreisig at aol.com]

Radsafe,
 
     Look at the CERN health physics website???   Email health physicists 
at CERN???
 
     Good Luck    Joe Preisig
 
 
 
 
 
In a message dated 10/27/2014 5:27:54 P.M. Eastern Daylight Time,  
tdc at xrayted.com writes:

I am  dealing with an x-ray machine interlock design.

Of course it will be  redundant and failsafe and testable - but the 
question has come up  regarding using semiconductor devices in the 
interlock  circuit.

When I was the x-ray safety officer at a national laboratory I  resolved 
that issue by simply not accepting semiconductor devices in  interlock 
circuits - problem solved.

I maintained that when such  included logic circuits that showing that 
its was failsafe with the  failure of any single component could not be 
demonstrated - even  disregarding issues with defining what constituted a  
"component".

Further testing requires that each component be  isolated, exercised and 
tested - and I maintained that is simply not  possible with logic 
circuits.  ie. - just opening the door and  observing that the x-rays 
turn off is most definitely NOT a  test!

Its not as simple anymore.

I have heard however that there  is a euro standard that prohibits the 
use of semiconductor devices in  interlock circuits.  So - I was hoping 
someone here might know IF  that were in fact so - and if so shat that 
standard  is.

Thanks

Ted de  Castro
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