10.3 TYPES OF RADIOLOGICAL CONTROLS
Radiological controls can be grouped into two broad categories - engineered controls and
administrative controls. Sometimes the two methodologies overlap in their implementation. Consider
how the basic ALARA principles of time, distance, and shielding are implemented through each of
these types of controls.
10.3.1 Engineered Controls
Engineered controls consist of equipment designed to protect personnel from a hazard by
preventing access to enclosures, providing a warning of the hazard or a means to remove the
hazard. These controls may be active or passive.
Examples of engineered controls used at TJNAF include:
|Passive Engineered Controls
|Active Engineered Controls
- Installed shielding
- Walls, gates, or locked doors
- Key controls
- Interlocked monitoring instruments
- Warning indicators or status displays
- Ventilation systems
TJNAF's design incorporates heavy use of shielding. The earth overburden on the beam enclosure
is an obvious example. Structures such as earth berms, and concrete walls are considered
Temporary shielding (e.g. lead or concrete blocks) can only be installed when procedures are used.
Once temporary shielding is installed, it cannot be removed or altered without proper
Temporary shielding will be marked or labeled with wording such as, "Temporary Shielding -
Do Not Remove Without Permission from Radiological Control". This is an example of the
combination of an engineered control (the shielding) and an administrative control (the labeling
and tracking of these structures).
10.3.2 Administrative Controls
10.3.2.1 Configuration Controls
The above example of labeled shielding is known as a configuration control. Elements of the
configuration control program include:
Labeling and inventory of controlled devices
Procedures for change and/or restoration of configuration
Testing to verify proper configuration
Other examples of structures and equipment to be maintained in a specific configuration:
Critical Safety Devices (certain beam monitors, beam stops, or magnets)
Safety interlocks and "crash" switches
Area Radiation Monitors and their detectors
Wiring, interconnects, computers and controllers for the above
10.3.2.2 Radiological Postings
Postings (signs, tags, labels) are used to alert personnel of an existing or potential radiological
hazard and to aid them in minimizing exposures and preventing the spread of contamination.
Radiological postings are the primary means of communicating radiological hazards to workers.
All personnel are required to comply with these postings. Disregard for postings or other
radiological instructions is grounds for disciplinary action.
An area to which access is controlled in order to protect individuals from exposure to radiation
and radioactive materials is known as a Controlled Area. It is a boundary area around other
radiological areas. The TJNAF accelerator site (fenced in area bounded by locked or guarded
access gates) has been designated as a Controlled Area. This means that within this area, you
are likely to see postings for Radiological Areas, or radioactive material or possibly encounter
slightly elevated levels of radiation. By design, a person who spends their entire work year only
in the controlled area is not expected to receive enough radiation dose to require dosimetry (50
Requirements to enter the Controlled Area are:
training in radiological controls (GERT, RWT, or ARM training) -or-
an escort who is trained at least to the GERT level
The security guard at the accelerator site access will check your identification badge to ensure you have had the appropriate training.
You may also find Controlled Areas in:
Locations within the Test Lab (Bldg 58)
Locations within the EEL Building (Bldg 90)
Designated Radioactive Material Storage Areas around the site
RADIOLOGICAL AREAS (or Radiologically Controlled Area)
Areas within the Controlled Area boundary are clearly posted to alert personnel to the presence
of elevated radiation levels and/or radioactive materials. These areas are designated
Radiological Areas. In these areas, radiation levels are high enough that personnel may receive
more than 100 mrem in a year. Radiological Areas contain radiation levels that require
personnel radiation monitoring (dosimetry) for entry. These areas are designated with postings
containing the standard radiological warning symbols and colors together with yellow and
magenta ropes, chains or other boundary indications.
Requirements for unescorted entry:
- TLD badge
- Radiation Worker Training
- Signature on General Access Permit (In beam enclosure)
All Radiological Areas are identified by the following:
- Signs that have the standard
radiation symbol colored magenta
(purple) or black on a yellow
- In the absence of doors or other
physical entry points, yellow and
magenta rope, tape, chains or
markings are used to designate the
boundaries of posted areas.
- All Radiological Area postings will contain the words "Radiologically Controlled Area", or "RCA".
- Personnel dosimetry requirements will also be included on the posting.
Requirements for working in a Radiologically Controlled Area include:
- Practice ALARA - minimize your time in the area
- Do not eat, drink, or smoke in the RCA
- Minimize waste production, and segregate waste according to posted instructions
- Maintain visual and verbal communications with any escorted visitor
- Obey all posted radiological instructions
Typical Locations of Radiological Areas at TJNAF:
- Linac/Arc Service Buildings
- Beam Enclosure (including experimental hall)
- Operating end station roof
- Areas within the EEL and Test Lab
When leaving a Radiological Area:
Make sure you have not left unnecessary waste items in the area
Check to make sure you have your dosimetry (read your SRPD, if one is worn)
Check for personnel contamination monitoring requirements - some areas may require
a contamination check prior to leaving. If monitoring is required, follow the
procedures discussed later in the handout.
Within a Radiologically Controlled Area, various other Radiological Area postings may exist.
These areas are usually defined by specific levels of radiation or contamination which may exist
within. The definitions and requirements for working in these areas follow.
RADIATION AREA - Areas where the whole body radiation dose rates (30 cm. from the
source of radiation) are >5 mrem/hr but <100 mrem/hr. The postings/signs will include
the words "CAUTION RADIATION AREA".
All of the precautions for working in RCA apply. Check the posting to determine if an
RWP is necessary. Notify the RCG when performing activities which might change
radiological conditions, such as moving radioactive materials within the radiation area,
removing items from the area, or disassembling or modifying any activated component.
Know the radiation levels and where to position yourself to minimize your dose.
Only Radiation Workers are permitted in Radiation Areas - no visitors.
Requirements for working include: Don't loiter, practice keeping your exposure ALARA,
read your dosimeter periodically; if unanticipated elevated radiation levels are indicated as
identified by off-scale dosimeter, radiological alarms or other indicators, stop working,
alert others working in the area, immediately exit the area and notify Radiological Control
Requirements for exiting: Read your SRPD or digital dosimeter. Complete the RWP timesheet entry if applicable.
Typical Locations of Radiation Areas at TJNAF:
- Near activated beamline components in the tunnel/end station
- Above unshielded service building penetrations
- Labyrinths/shielded passages near the beam enclosure during beam operation
HIGH RADIATION AREA - Areas where whole body radiation dose rates are >100
mR/hr but less than 5000 mR/hr. The postings/signs will indicate: "CAUTION - HIGH
RADIATION AREA" "TLD, Supplemental Dosimetry and RWP Required For Entry"
High Radiation Areas should remain locked and/or have physical barriers established. If the dose rate in the area exceeds 1 rem/hr, an approved physical access control must be in place. Physical access controls are used for High Ra
diation Areas whenever possible. These physical controls include:
- Locked doors with strictly controlled keys
- Warning devices that inform personnel and supervisors that an entry is being made.
- A device that causes the source of radiation to cease upon personnel entry or that prevents
entry when the source is present.
Requirements for Entry are:
- Level I or II Radiological worker Training.
- An RWP is mandatory for High Radiation Areas.
- SRPD's or digital dosimeters are required. Additional dosimetry may be required - always check the RWP carefully.
- A pre-job briefing is required to enter High Radiation Areas.
Typical Locations of High Radiation Areas at TJNAF:
- Near irradiated high power beam dumps
- Near highly activated portions of beamline
- End station beam dump cooling water buildings
- Interlocked beam enclosure when beam is on
- Near operating RF accelerator cavities
Hot Spot - A spot (usually small) where the dose rate on contact is greater than 100 mrem/hr and at least five times the whole body dose rate.
Typically, Hot Spots will be located on activated portions of beamline and
beamline components. Never handle a Hot Spot without concurrence from
|Summary of Radiation Worker I accessible areas
||Dose Rate Criteria
||< 100 mrem/yr
||'Controlled Area, Training or Escort Required
|> 0.05 mrem/hr
|'Radiologically Controlled Area, (or 'RCA')
Dosimetry Required for Entry'|
||5 mrem/h - 100 mrem/h
||'Caution Radiation Area, TLD Required'|
|High Radiation Area
||0.1 rem/h - 5 rem/h
||'Danger High Radiation Area, RWP Required'|
||> 0.1 rem/h on contact
||'Caution Hot Spot'
RADIOACTIVE MATERIALS AREA - Areas where radioactive materials are stored or
handled. The posting/signs will indicate: "CAUTION - RADIOACTIVE MATERIALS"
The Radioactive Material Area posting is usually accompanied by RCA designation. When
working in areas such as the beam enclosure, items which you remove from a
radioactive system or component must be surveyed and tagged.
Note: Installed beam line components and hardware are not normally tagged as radioactive
material - Always get concurrence from the RCG prior to disassembling such equipment.
The presence of Radioactive Materials does not always signify a
Radiological Area. Radiological Areas are posted based on the potential for
radiation exposure above certain levels. However, in order to maintain
control and accountability of radioactive materials, Controlled Areas are
usually established for storing them. Removal of radioactive items
from these areas requires Radiological Control approval. Sometimes
radioactive materials are stored in non-controlled areas temporarily. This
may be the case when exterior dose rates on an item are so low that it
presents no significant radiological hazard and no need for personnel
dosimetry for working in the area.
When these conditions are met, the container or radioactive item itself are
considered the Controlled Area boundary, and the item must:
Be conspicuously labeled as Radioactive Material, and
Be posted with a Controlled Radioactive Material Tag, which identifies
the custodian of the material, approved storage location, and its radiological
Typical Locations of Radioactive Materials Areas at TJNAF:
- Beam Enclosure
- Areas within EEL and Test Lab
- Designated Radioactive Material Storage Areas within the Site Controlled Area
The following radiological areas are areas that a Level I trained employee cannot enter.
Very High Radiation Area - The postings/signs will indicate: "GRAVE DANGER - VERY HIGH RADIATION AREA" "Special Controls Required for Entry"
Contamination Area - The posting/signs will indicate: "Contamination Area" "RWP Required for Entry"
Radiography Area - The posting will indicate "Radiation Area, Keep Out". Only the radiographic team and associated Radiological Control personnel are
allowed entry to these areas.
Airborne Radioactivity Area - The posting will read "Caution, Airborne Radioactivity Area, RWP Required for Entry"
VIEW EXAMPLE OF RWP
VIEW RWP DOSE TRACKING LOG
VIEW SURVEY MAP
ANSWERS TO UNIT 10 REVIEW QUESTIONS