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Ionizing Radiation - Calibration Services
Ordering Calibrations
Services
TheIonizing Radiation Standards
Group develops and maintains Canada's primary measurement standards for
ionizing radiation fields and provides calibrations based on these standards.
The Group works with standards and measurement techniques related to
exposure and air-kerma in low-energy X-ray and 60Co beams,
absorbed dose to water in 60Co beams and in electron and photon
beams from linear accelerators, neutron fluence and dose equivalent, absorbed
dose to tissue in a ß-ray field, and Fricke dosimetry. They also
develop Monte Carlo techniques for the simulation of electron and photon
transport in materials; and they participate in the development of dosimetry
protocols for use in cancer radiotherapy clinics.
 Facilities
Uncertainties
Fees
for Service
Contact:Dr.
Carl Ross
Tel. (613) 993-2715
Facilities
The section is equipped with X-ray generators, two 60Co therapy
units, radioactive sources, three  - ray sources, an Elekta Precise clinical linear accelerator, and a 35
MeV electron linear accelerator.
The X-ray generators provide stable beams of X-rays at constant potentials
from 10 kV to 300 kV. Exposure rates from 100 pA/kg to 60 µA/kg
(about 1 mR/h to 15 R/min) can be selected, covering both protection and
therapeutic levels. 60Co beams are standardized in terms of
exposure, air-kerma, and absorbed dose. 60Co exposure rates
between 400 nA/kg and 300 µA/kg (100 mR/min to 80 R/min) are available.
The electron linear accelerator is a 35 MeV high-current short-pulse
machine. The accelerator can be run up to 50 MeV unloaded and can sustain
an average current of 60 µA at 35 MeV.
A low energy "pretzel" magnet placed between sections makes
available the full electron current at energies between 5 MeV and 12 MeV.
At the end of the accelerator, a conventional 2-magnet steering system
provides electron beams with well-known energies. A variety of targets,
beam flatteners, collimator systems, scattering foil systems, beam current
monitors, and beam steering systems allow a wide variety of clinical accelerator
beams to be simulated. The accelerator can also be run with currents averaging
less than a single electron per pulse. In addition to the provision of
electron and photon beams for dosimetry, the electron linear accelerator
is available to outside users.
The Elekta Precise Linac is a standard clinical radiotherapy machine
with photon beams of 6, 10 and 25 MV and 5 electron beams with energies
between 4 and 22 MeV. The linac delivers clinical dose rates of about
5 Gy/minute.
Uncertainties
The uncertainties quoted in the descriptions below are standard uncertainties,
that is, they are at the one-standard-deviation level. They were obtained
by assuming a normal distribution.
Fees for Service
Ordering Calibrations
Services NEW procedures effective March 23, 2006.
A33-08-00-00
Custom Ionizing Radiation Standards Measurements
or Services
Fee on request. |
Contact
Dr.
Carl Ross for further information |
A33-08-00-01
Handling Fee
$300 |
A charge is levied for any instrument
or radioactive source that is found to be unsuitable for calibration.
The fee covers inspection and return and is based on the work done
prior to the discovery of the fault. |
Determination
of Source Strengths
Instrument
Calibration
Irradiations
in Known Fields
Use
of NRC Irradiation Facilities
Thermoluminescent
Dosimetry (TLD)
| Determination
of Source Strengths (A33-08-01-01 to A33-08-01-04) |
A33-08-01-01
60Co Therapy Source
$2750 |
The
exposure or air-kerma rate from a 60Co therapy source at
the client's location is measured by Council staff using an NRC calibrated
cavity ion chamber. |
A33-08-01-02
Additional 60Co Therapy Source
$365 |
Measurements of the exposure or air-kerma
rate from additional sources will be made at a reduced rate per source
when scheduled for testing at the same time and place as A33-08-01-01. |
A33-08-01-03
Low-Activity 60Co Source
Fee on request |
The
exposure or air-kerma rate from low-activity 60Co sources
is measured at NRC. This service is available by special arrangement
only. |
A33-08-01-04
Radioactive Neutron Source
$2055 |
This service measures the neutron flux
from a radioactive neutron source. NRC no longer maintains a primary
standard for neutron source strength. However, the Council does have
several Am-Be neutron sources whose outputs and half-lives have been
established. Using these sources and well characterized neutron long
counters, the output from a client's neutron source can be established
with a standard uncertainty of about 2% for sources with a spectrum
similar to that of the Am-Be sources. |
| Instrument
Calibration (A33-08-02-01 to A33-08-05-02) |
A33-08-02-01
X-Rays
$1195 |
This
service provides exposure and air-kerma calibration for one quality
of radiation for one instrument and its probe using one instrument
range.
The primary exposure and air-kerma standards at X-ray energies are
two free-air chambers. The smaller of these covers X-rays produced
by accelerating potentials up to 80 kV and the larger one covers X-rays
up to 300 kV. This range of X-ray energies is produced by several
special generators in which both the potential across the X-ray tube
and the anode current are highly stabilized and accurately monitored.
By varying the anode current and distance from the source, calibrations
of instruments can be provided at exposure rates varying by six orders
of magnitude, from therapy exposure rates (60µA/kg (15R/min)) to radiation
protection rates (100 pA/kg (1 mRh)). A variety of beam filtrations
is available and, after discussion with the client, NRC will match
the client's end-use beam quality as accurately as possible during
the calibrations.
The value of the exposure, or related air-kerma, typically has a standard
uncertainty of 0.5% at the higher exposure rates, although the overall
accuracy of the instrument's calibration factor also depends on the
precision of the instrument being calibrated.
NRC exposure standards have been used in various international comparisons
with other national standards laboratories. Agreement with the standards
of NIST (National Institute of Standards and Technology) in the USA
and the Bureau International des Poids et Mesures in France is within
±0.3% . |
A33-08-02-02
Additional X-Rays
$250 |
Calibrations in additional
beam qualities and/or instrument ranges will be performed at a reduced
cost when scheduled at the same time as A33-08-02-01 and for the same
instrument. |
A33-08-03-01
60Co
$1195 |
Exposure
and air-kerma calibrations, or absorbed dose to water calibrations,
are carried out for one instrument and its probe using one instrument
range. The primary exposure standard for gamma-radiation from 60Co
is a carbon-walled cavity ion chamber. Extensive work has been done
concerning the correction factors required for cavity chamber exposure
standards, in particular the point of measurement correction factor
and the wall attenuation and scatter correction factor.
The laboratory has two 60Co teletherapy heads with calibrated
outputs. The older unit produces exposure rates at 1 m of about 20
µA/kg (5 R/min). In conjunction with a precision irradiation timer
designed and built at NRC, this unit can deliver accurately-known
exposures down to less than 25 µC/kg (100 mR). This unit is used primarily
for the calibration of radiation protection instruments. The newer
unit produces an exposure rate at 1 m of about 300 µA/kg (80 R/min),
which is more typical of clinical units and is used primarily for
the calibration of radiation therapy instruments.
For both units, the exposure rates are known with a standard uncertainty
of 0.5% (one standard deviation) although the overall accuracy of
a calibration factor also depends on the precision of the instrument.
The 60Co units at NRC are former therapy units and thus
the spectrum from these units is similar to that used in therapy situations.
Measurements and Monte Carlo simulations done at the Council indicate
that over 25% of the photon fluence in the beams of these machines
consists of scattered photons and these contribute about 15% of the
exposure in the beam.
The 60Co air kerma standard at NRC has been compared to
the standards in several other national standards laboratories, such
as PTB (Physikalisch Technische Bundesanstalt) in Germany and the
Bureau International des Poids et Mesures in France, and found to
agree within 0.2%, although air kerma rates measured using NRC calibrations
are 0.6% larger than those based on calibrations from NIST.
The standard for absorbed dose to water in a 60Co beam
is a sealed water calorimeter. The instrument measures the radiation-induced
temperature rise at a point in a water phantom.
The absorbed dose to water rate is known at 5 cm depth in a water
phantom irradiated by a 10 x 10 cm2 beam, with the surface
of the phantom at 1 m from the source. Based on this knowledge, waterproof
ion chambers can be calibrated directly in terms of absorbed dose
to water by being placed in the water phantom.
The dose rates at the point of calibration are about 8 cGy/min and
60 cGy/min on the two 60Co units discussed above. The standard
uncertainty in the absorbed dose rate is 0.6%.
|
A33-08-03-02
Additional 60Co
$250 |
Calibrations on additional
instrument ranges will be performed at a reduced cost when done at
the same time as A33-08-03-01. |
A33-08-04-01
Neutrons
$1485 |
A
neutron survey meter is calibrated using an Am-Be source of known
output. Using this source, and a knowledge of its spectrum (average
energy 4.4 MeV), NRC can provide calibrations of neutron remmeters
in a field of roughly
20 µSv /h (2 mrem h-1). |
A33-08-05-01
ß-Rays
Fee on request |
Absorbed dose to tissue
calibration of a direct reading ß dosimeter is performed in
fields from 204Tl, 90Sr+90Y, and
147Pm ß sources at a variety of specified distances.
The primary standard for ß-ray absorbed dose is an extrapolation
ion chamber built at NRC following a design developed by PTB in Germany.
With this chamber, the absorbed dose to tissue at a variety of depths
in a tissue equivalent phantom has been determined at a variety of
distances from 204Tl, 90Sr+90Y, and
147Pm ß sources. At the calibration positions, the
mean energies of these ß sources have been determined to be
300 keV, 670 keV, and 70 keV respectively. The dose rates span more
than three orders of magnitude and have been determined with a standard
uncertainty of 2%. The measurements agree well with independent calibrations
carried out on the same set of sources by PTB.
These sources can be used to calibrate radiation protection instrumentation
although great care must be taken in interpreting the results since
calibration factors are very geometry dependent; that is, the calibration
factor usually changes as a function of distance from the ß
source because the ß spectrum changes due to slowing and scattering
in the air.
This calibration service is available by special arrangement only.
Only the 90Sr+90Y calibrations are routinely calibrated. |
A33-08-05-02
Additional ß-Rays
Fee on request |
Additional
distance calibrations for the ß dosimeter used in A33-08-05-01
can be performed at the same time at a reduced rate per distance calibrated.
This service is available by special arrangement only. |
| Irradiations
in Known Fields (A33-08-07-01 to A33-08-07-02) |
A33-08-07-02
Irradiation of Material in 60Co,
beta, and X-Ray Fields
Fee on request |
Material is irradiated to a known dose
or exposure in 60Co and X-ray fields.
The Council's X-ray generators, 60Co teletherapy units,
and  sources used in the
various standards are available for irradiation purposes. NRC also
has a variety of other sources with varying strengths, for example,
a 60Co Gamma-cell with a dose rate of 8 Gy/minute and a
variety of calibrated weak 60Co and radium sources for
calibrating radiation protection instrumentation.
This service is available by special arrangement only. |
| Use
of NRC Irradiation Facilities (A33-08-08-01 & A33-08-10-01) |
A33-08-08-01
35 MeV linear Accelerator
$(/hr) 500 |
The group has
a 35 MeV linear accelerator which provides electron beams with energies
between 5 MeV and 35 MeV with average beam currents up to 60 µA.
This can be used to produce either electron or photon beams in a
wide variety of configurations. The linear accelerator beam is available
on an hourly basis. A minimum of four hours must be reserved. |
A33-08-10-01
Use of 60Co or X-Ray Unitsr
$(/hr) 100 |
The
60Co and X-ray unit facilities at NRC are available on an hourly
basis. A minimum of four hours must be reserved. |
Thermoluminescent Dosimetry (TLD)
Quality Assurance Service (A33-08-11-01 to A33-08-11-04)
60Co Dosimetry
Facilities are available at NRC for quality assurance testing of personal
dosimetry systems, most of which use TLD. The service provided by the
Council involves irradiating a batch of up to 150 TLDs free in air in
a 60Co beam to a known exposure or air-kerma of between 30
µC/kg (1mGy to air) and 30 mC/kg (1 Gy to air). The irradiated dosimeters
are returned to the client dosimetry services which process them and report
their results for the exposure or air-kerma to NRC. NRC compares the dosimetry
service values to the Council's values and reports the results simultaneously
to the Atomic Energy Board of Canada and to the dosimetry services.
A33-08-11-01
$9295 |
This
service covers the first use of the Co facilities in a single
calendar year. |
A33-08-11-02
$447.50 |
Each subsequent use of
the Co facilities in the same calendar year is charged at a
reduced rate per usage. |
X-Ray Dosimetry
Facilities are available for X-Ray dosimetry similar to the 60Co
dosimetry service (A33-08-11-01 and A33-08-11-02) described above. The
radiation procedure is consistent with the requirements outlined in Appendix
H of the Independent Test Specifications for Dosimetry Services: X-radiation,
in the Regulatory Standards S-106(e), Technical and Quality Assurance
Standards for Dosimetry Services, published on March 20, 1998, by the
Atomic Energy Control Board. The procedure is tailored to meet the client's
requirements and the fees are set accordingly. NRC values and the client's
measured values for exposure (air kerma) are sent to the Provincial Radiation
Dosimetry Review Committee.
A33-08-11-03
$9295 |
This
service covers the first use of the X-Ray facilities in a single calendar
year. |
A33-08-11-04
$447.50 |
Each subsequent use of the X-Ray facilities
in the same calendar year is charged at a reduced rate per usage. |
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