Re: HIGH-TECH SECURITY TOOLS GET A SECOND LOOK

[andrew_mcewan@nrl.moh.govt.nz]

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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