Operating Manual

Figure 14-5 shows an S-chan-
nel container with a flexible
(metal) hose and cable in rol-
led up (transport) position.
Figure 15-5 shows a more
recent (2006) S-channel
Selenium75 container with
operation hoses and pigtail.
Selenium75 radio-isotope is
becoming popular since new
production (enrichment)
methods resulted in a much
better k-factor. Thus for a cer-
tain activity (source strength)
a much smaller source size (focus) is achieved. This results in a better/sharper image qua-
lity than could be achieved with the old Selenium75 production method.
Due to its average energy level of 320 kV, Selenium75 increasingly replaces X-ray
equipment for a thickness range from 5 mm to 30 mm of steel. This eliminates the need for
electric power, very attractive in the field for reasons of electrical safety and more
convenient at remote- or work locations with difficult access (high, deep, offshore,
refineries, etc). Last but not least, a Selenium container is of much lower weigth than
needed for an Iridium192 container with the same source strength.
To enable radiography on work sites with (many) people in the vicinity, for example on
offshore installations or in assembly halls, containers with rotating cylinders
and collimators were developed so that only the beam of radiation required for the
radiograph is emitted.
The remainder of radiation is absorbed by the collimator material which allows people to
work safely at a distance of a few metres while radiography is in progress. Such containers
with collimators are known by the name of “CARE” (Confined Area Radiation Equipment)
or “LORA” (Low Radiation) equipment.
4948
Fig. 14-5. S-channel container with the flexible cable and deployment mechanism.
Fig. 15-5. S-channel container for Selenium75 with pigtail (at right) and operating hoses (at left)
Fig. 16a-5. Gamma container with collimator
on a circumferential weld in a pipe
handle
tungsten container
rotating cylinder
source
Collimator
base
pipe and weld
film
lead shielding
boundaries of the beam of radiation
Fig. 16b-5. Cross-section of CARE/LORA container on the pipe
Without collimating the minimum safety distance is considerably more than 10 metres (in
all directions!).
Such containers with collimators are particularly suitable for frequent and
identical repetitive NDT work, for example radiographic testing of welds in pipes of
< 300 mm diameter.
Figure 16a-5 shows such a special container with collimator set up for a double wall
radiograph. The cross-section drawing of figure 16b-5 shows the boundaries of the beam of
radiation. For bigger focus-to-film distances, longer collimators are used to restrict the
beam of radiation.
This type of container is suitable for Iridium sources up to 1000 GBq and weighs “only”
approx. 20 kg. A similar system (Saferad) with a weight of up to 15 kg exists, using
Selenium75, which almost eliminates the usual disruption to construction, maintenance
and process operations in the vicinity of the exposure.
5.7 Checking for container leakage
A sealed radioactive source (capsule) might start to leak and become an open source as a
result of corrosion, mechanical damage, chemical reactions, fire, explosion etc.
Regular mandatory “wipe-tests” by specialists serve to detect leakage at an early stage.
measuring tape weld
lead