UFC 4-022-01
25 May 2005
mobile and fixed x-ray/gamma-ray inspection systems. Several manufacturers were
consulted to obtain the data used to develop the following guidelines. However, consult
with manufacturers of these systems during the design of an entry control facility to
ensure data concerning operational considerations is current and the best available.
These systems offer the ability to inspect vehicles or containers without removing the
cargo. The equipment typically consists of a transmitter (x-ray or gamma ray) and a
detector on the opposite side of the target vehicle. Gamma ray systems utilize a low-
level, gamma-ray radiation source to generate a beam of gamma rays to penetrate the
object. The detectors on the opposite side then measure the amount of gamma ray
absorption. This data is then translated into an image of the contents of the vehicle or
container. X-ray systems typically utilize electro-mechanical equipment to generate X-
rays to penetrate the object. Detectors on the opposite side then record the x-ray
transmission, which is then translated into an image. The MobileSearch and Shaped
Energy ISO Search systems (discussed below) also include a detector on the
transmission side of the unit that detects the x-ray reflections, which occur from organic
materials, producing a second type of image of the contents.
7-3.3.1 Safety and Regulatory Considerations
Due to the use of gamma or x-ray radiation, there are safety and regulatory
considerations in the use of these systems. The requirements vary depending on the
system. Normally an exclusion zone, an area where personnel are not permitted during
operation of the equipment, is established within and around the inspection equipment.
The region outside of the exclusion zone is considered safe for personnel during
scanning operations. The size of the exclusion zone varies greatly depending on the
type of equipment.
Nuclear Regulatory Commission regulations state that radiation dose limits in Public-
Uncontrolled areas are 2 mR in any hour or 100 mR in any year. Therefore depending
on the characteristics of the source, the frequency of scans, and the expected
occupancies, the exclusion zone can vary. Additionally, a shielding wall can be
constructed to reduce the dose substantially. Some x-ray systems have qualified as a
"cabinet x-ray system" in accordance with FDA regulations or similar standards,
meaning minimal shielding is required and the exclusion zone does not extend outside
of the footprint of the inspection area. In order to qualify for this designation, FDA
regulations require an emission limit of 0.5 mR per hour at 2 in (5 cm) from the surface
of the cabinet. Other regulatory considerations are that systems utilizing radioactive
sources may require operation under a radiation materials license held and
administered by the owner of the equipment (the installation) and a permit for operation
may be required.
7-3.3.2 Mobile Vehicle Inspection Systems (Imaging)
There are several truck-based, mobile large vehicle or container inspection systems
currently available. Two examples are illustrated in Figures 7-1 and 7-2. These
systems utilize a boom type arm to form an inspection tunnel. In no case are the
vehicle operators to remain in the vehicle during a scan. The operator is either to exit
the vehicle or the vehicle is positioned such that the operator is outside the scan area
7-3
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