Re: HIGH-TECH SECURITY TOOLS GET A SECOND LOOK

[Ted de Castro <tdc@XRAYTED.COM>]

Math error!



The population dose from the x-rays is NOT a few micro sieverts.  You

must totalized all those "few micro sieverts" among all those passengers

on all those flights and then figure in the rather low probability of

hijack.



THAT is the way the risk/benefit game is played right now.



Still - its NOT a dose issue!  No matter HOW small.



andrew_mcewan@nrl.moh.govt.nz wrote:

> 

> A few points on this topic.  There are two types of x-ray systems that are usable for screening people for weapons and drugs.  Transmission x-ray

> systems can be designed to produce satisfactory images with small radiation doses.  Personnel scanning using such equipment is used to monitor workers

> a daily basis in diamond mines in South Africa.  I don't have good data on the doses received but think cumulated doses amount to several mSv/year.

> Probably single exposures of airline passengers, or those about whom there was some suspicion, at a few microsieverts at most per exposure would not

> be unreasonable on a cost/benefit basis, remembering that the object of radiation protection is "to provide an appropriate standard of protection for

> man without unduly limiting the beneficial practices giving rise to radiation exposure".  The benefits in this situation are avoidance of terrorist

> acts; the (radiological) costs are a few microsieverts, or less than the additional cosmic radiation received in a flight across the continental US.

> 

> The second type of equipment (commented on by Jean Moore) makes use of computer techniques to produce images from lower energy scattered x-rays that

> allow good resolution images of the body surface.  The doses per exposure can be made much lower than for transmission imaging and trivial in

> comparison to the additional cosmic radiation received during a flight.  In principle there would appear to be little argument against the use of such

> equipment.

> 

> I understand the IAEA has been asked for its views on the justification for the use of x-ray screening of passengers at airports.  After a period of

> consultation with its RASSC group the Secretariat replied that it had been unable to reach a consensus view on the matter.  Perhaps after recent

> events a decision will be reached more readily.

> 

>   Andrew McEwan

> 

> _________________________

> Andrew C McEwan PhD

> National Radiation Laboratory

> PO Box 25-099

> Christchurch, New Zealand

> 

> Ph 64 3 366 5059

> Fax 64 3 366 1156

> Andrew_McEwan@nrl.moh.govt.nz

> 

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