Re: Radiation Safety System

[tdc@ehssun.lbl.gov (Ted M. de Castro)]

>>Date: Tue, 12 Apr 94 12:01:21 -0500
>>From: "Paul Rossi" <PROSSI@gremlin.iucf.indiana.edu>
>>To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
>>Subject:       Radiation Safety System

>>Especially for those working at Accelerators

>>I'm in the process of redesigning my current radiation system (to 
>>limit personnel access to experimetnal vaults when a proton beam is 
>>in the vault). I'm looking around for some ideas on systems that 
>>others have used. If anyone has one or is familiar with a design I 
>>would highly appreciate your input. Especially the part about "If I 
>>had it to do all over again!"

As accelerator safety officer at LBL there would be no question as to how I 
would require this be done!  The cave/vault would be interlocked and there 
would be a required search and secure procedure (also hardware interlocked) 
required before beam could be brought into the cave.

Also - this is I beleive what is required by the ANSI N43 accelerator 
standard - if not it will be since I'm on that committee too.

In caves with areas that need to be searched and cannot be easily seen from 
the cave entrance we use a KIRK KEY system to force the searcher to "visit" 
the key box locations and turn the key to make-up the interlock.  We do this 
for many areas at the ALS.

We DID have 3 caves with allowed access during beam on conditions because 
these were very low intensity beams.  All but one of these has been 
discontinued.  When they were done there was redundant active 
instrumentation with check sources for a minimum count rate in the cave to 
trip the beam off if levels went beyond expectations.

Basically our policy is that there is NO VALID REASON for such routine 
access to a cave with beam on - EVEN WITH LOW LEVELS.  Such a "need" usually 
means bad experimental planning or bad equipment set-up.  There is NOTHING 
that cannot be remoted!  When the one existing situation is over - there 
will be no more.

We have had situations where we have been concerned about occupancy in a 
cave with beam in an adjacent cave.  This is always considered on an 
individual basis it is always monitored with redundant, failsafed 
instrumentation as mentioned above.

On a one shot basis occupancy can be permitted with low level beams but the 
need must be justified and there with be a Health Physicist present 
monitoring the operation.  Care must be taken to not allow such one shot 
operations to become routine.

If more questions - call and we can chat ..

Ted de Castro
(510) 486-5256