SIGMA projetor - Manual (Page 71)

EMERGENCIES AND PERSONNEL SAFETY
7.2
Access to Restricted Areas
The site where radiography is performed must be separated from other work areas by as much distance
as possible. If applicable, check for occupation of the areas above and below the radiography site.
Clearly defined boundaries must be set up and warning signs displayed to provide warning and prevent
access to the radiography site by unauthorized personnel before any exposure begins.
No one should enter the boundary marking a ‘Restricted Area’ or ‘Controlled Area’ without a film badge or
TLD, direct reading pocket dosimeter (or electronic pocket dosimeter) and alarm ratemeter (if required).
A pocket ‘chirper’ alarm is required in some countries to provide radiography personnel with an immediate
audible warning of a high radiation intensity.
United States Regulations
‘High Radiation Area’ signs must be posted where a dose of 1 mSv (100 mRem) could be received in any
one hour. The radiographers must provide continuous direct surveillance of the area or when a
permanent installation is used, the entrance must be equipped with door interlocks, audible and visual
warnings.
‘Radiation Area’ signs must be posted where dose of 5 µSv (5 mRem) could be received in any one hour.
‘Restricted Area’ must be identified and posted where a dose of 20 µSv (2 mRem) could be
received in any one hour or 1 mSv (100 mRem) in one year.
In practice, the ‘Radiation Area’ and ‘Restricted Area’ are combined and identified by the use of a rope
barrier. The area is posted with the ‘Radiation Area’ signs where the maximum dose will not exceed 20
µSv (2 mR) in any one hour or 1 mSv (100 mRem) in a year. The practice of using the ‘Radiation Area’
sign at the ‘Restricted Area’ boundary clearly defines why the area has been restricted. Additionally, the
trefoil (radiation) symbol provides a visual warning for those individuals who cannot read.
During a radiographic exposure, a calibrated and operable survey meter must be used to confirm the
dose rate at the ‘Restricted Area’ boundary and adjusted if the dose rate exceeds the limit of 20 µSv (2
mRem) in one hour.
During the radiographic exposure, the radiographers must maintain continuous direct surveillance of the
‘High Radiation Area’ in addition to ensuring that no one enters their posted ‘Restricted Area’.
EU Regulations
A ‘Controlled Area’ must be marked with a barrier at a distance where the radiation intensity will not
exceed 7.5 µSv/hr (0.75 mR/hr). The boundary dose rates must be noted and the record kept for 2 years.
During radiographic operations, only classified radiation workers are allowed inside this area.
A ‘Supervised Area’ is defined as the area where the boundary dose rate limit must not exceed 2.5 µSv/hr
(0.25 mR/hr). No barriers or notices are required here, but the radiographer must be vigilant to ensure
that personnel in this area do not enter the ‘Controlled Area’.
Personnel Monitoring
All personnel who enter a ‘Restricted’ or ‘Controlled’ area or are present during radiographic operations
are required to wear the appropriate personnel monitoring devices as required by the regulatory
jurisdiction. These devices can include; film badges; thermoluminescent dosimeters (TLD); optically
stimulated luminescence badges; direct reading pocket dosimeters; electronic pocket dosimeters; alarm
ratemeters; and audible alarms. Calibrated and operable survey meters must be used to determine
radiation levels when conducting radiographic operations.