RADIATION PROTECTION
SURVEYS
The radiation protection survey is an onsite evaluation of the x-ray facility performed by
or under the direction of a qualified expert. It is typically performed after the facility is
completed, although some components may be conducted prior to the completion of
construction
The purpose of a radiation protection survey is to identify higher-than-normal doses of radiation in
medical environments, labs, and anywhere radiation-emitting machines or radioactive materials (RAM)
are used. They are required by state and federal regulations to be performed regularly to ensure the
safety of technicians, technologists, nurses, doctors, researchers, and patients.
an inspection to verify that barriers are properly placed, contiguous and free of voids or
defects; and
an evaluation of shielding adequacy to verify that barriers adequately attenuate exposures
in nearby occupied areas to the relevant shielding design goal divided by the appropriate
occupancy factor
What is a radiation protection survey?
Radiation protection surveys are a way to directly measure radiation levels and identify
potential leakage through breaks or voids in shielding.
Surveys are performed on:
• Diagnostic fluoroscopic and radiographic equipment
• Non-medical industrial equipment such as those found in veterinary offices
• CT and CBCT machines
• Particle accelerators
• Irradiators
• Bone mineral densitometers
• Cabinet x-ray machines
• Areas that use sealed sources of RAM
• Packages containing RAM
THE DIFFERENT TYPES OF RADIATION SURVEYS
RADIATION EMITTING DEVICE SURVEY
X-ray machines and other radiation-emitting devices require regular surveys to be performed to confirm
that the machine is operating as expected. Radiation producing machines are surveyed for:
• Timer accuracy
• Radiation output
• Focal spot size
• kVp and mA
• Beam limitation accuracy
• Filtration
• Skin entrance exposure / rate of exposure
• Scatter radiation measurements
• Photo-timer operation
• Proper signage, labels, and postings
If high or unexpected dose rates are measured during a survey, the machine should be turned off and
undergo appropriate maintenance.
AREA SURVEY
Area surveys are required anywhere a radiation device is in use and the
potential for receiving a higher-than-normal radiation dose is present. These
surveys are typically measured in milliRoentgen per hour (mR/hr). The Roentgen
is a measure of the amount of ionization in the air from the radiation.
Anytime you have an area survey performed, you are required to keep the
official records of the survey results for 3 years
CONTAMINATION WIPE TEST
A contamination wipe test, also known as an indirect or swipe survey, is used to identify radioactive
material contamination on surfaces, equipment, and clothing such as those found in a lab. This type of
survey can identify non-fixed radiation left behind from radioactive solids, liquids, or gasses.
Wipe tests are recommended to be
performed frequently, especially if you are a
HAZMAT employee that receives or ships
RAM packages. A wipe test involves wiping at
least 300cm2 of the package’s surfaces using
an absorbent material. Afterward, the
activity on the swipe is measured assuming a
removal efficiency of 0.1 unless the actual
efficiency is known
Users in lab settings typically survey their work areas after an experiment or when a minor spill is
suspected.
RADIOACTIVE SEALED SOURCE
A radioactive sealed source is a source of special form RAM that has been
contained or encapsulated to prevent contamination. These sources can only be
opened by destruction. Semi-annual surveys of these sources are required to
check for leakage.
BIOASSAY SURVEY
Internal exposure monitoring, or a bioassay survey, is performed on individuals
that use unsealed radioactive materials. The survey estimates the internal organ
dose to determine if any RAM has entered the body. It can also help determine
if RAM is present in the air.
Bioassay surveys are performed by analyzing blood, tissue, or urine samples or
by carefully monitoring the presence and/or quality of isotopes present in the
organ of concern.
How often do I need to have a survey
performed?
The frequency of a radiation protection survey depends on several factors, most of which depend on
different state and federal regulations.
• When a new or used x-ray equipment is installed
• When existing x-ray equipment has been moved
• If shielding has been modified
• After the equipment has undergone significant repairs
• If a potential problem is indicated
Who performs these surveys?
In general, surveys on radiation-producing equipment are conducted by health physicists and
medical physicists.
Is special equipment required for a survey?
Special equipment is required to detect ionizing radiation. Most equipment is hand-held
measurement instruments called survey meters. This equipment is required to be calibrated annually
to maintain accuracy and to ensure that reliable measurements are recorded.
Survey meters consist of:
• A probe which produces electrical signals when it is exposed to radiation
• A control panel readout with an electronic meter that gauges the amount of radiation exposure
• A speaker which provides an audible indication of the radiation exposure
There are several different kinds of survey meters physicists use to perform radiation surveys.
Geiger-Mueller Pancake Probe
One of the more commonly used survey meters is the
Geiger-Mueller Pancake Detector. Although there is
no “universal” radiation detector, the G-M Pancake
Probe comes pretty close. This is because the probe
can detect alpha, beta, and gamma radiation,
although they are generally used for detecting Beta
Emitters. These probes come in a variety of models
and configurations.
G-M Pancake Probes are frequently used to detect C-14, Ca-45, P-32, P-33, and
S-35.
Scintillation Survey Meter
A scintillation survey meter is used to detect low-
energy Gamma Emitters and x-rays. The
scintillator, or sensor, is made of a transparent
crystal or liquid which shines when it interacts with
ionizing radiation. The scintillator is attached to a
photosensor like a photomultiplier tube which
detects the generated light.
This survey meter detects I-125 and Cr-51. They
are an ideal equipment choice for surveying
electron microscopes and x-ray diffractometers.
Pressurized/ Non Pressurized Ion Chambers
– Modes
• Rate
• Integrate
• Freeze
– Measures exposure in air
– Appropriate for radiation scatter surveys –
Consider energy response
– Consider response time of survey instruments
when setting exposure techniques
– Meter must be calibrated and capable of
measuring the range
Solid State
Solid State
• Energy compensated silicon diode array
• Best used for radiation scatter surveys
• Consider energy response
• Meter must be calibrated
Shielding Integrity
Shielding Integrity Survey
– Verify that the installed lead and facility layout meets the shielding plan
requirements
– Check for voids and consistency
– Best done prior to equipment installation
– Determine lead equivalence
Shielding Integrity
Shielding Integrity Methods
– Core samples
– Visual check during construction
– Portable X-Ray unit
– Radioactive source, i.e. Tc-99m, F-18
Shielding Integrity
Shielding Integrity- Core Samples
• Validates lead thickness
• Need to shield over holes created
• Does not account for lead flow
• Does not validate for voids
• Does not validate lead wrapping
• Does not easily validate installed lead height
Shielding Integrity-Visual
Check
Check Penetrations
Check to 7’ Check lead thickness
Check Doors
Shielding Integrity-Visual
Check
Screws/Nails Check lead wrapping
Covered
RADIATION SCATTER SURVEY
The purpose is to determine that the existing barriers provide sufficient protection to meet
regulatory exposure limits.
Also verify that the equipment and facility layout agrees with the shielding design
END OF
DISCUSSION
