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Radiation Dosimetry
A well-functioning dosimetry program is essential for
a safe operation and for compliance with applicable federal
and state regulations. The University radiation dosimetry
program is described in detail in Procedures 3.1/3.1.1.
 Classification of Dosimeters: There are four methods
of radiation dosimetry at the University as follows:
- External dosimeters (whole body) are used to measure
deep dose equivalent expressed in units of rem or
Sv.
- External dosimeters such as ring dosimeters are used
in cases where external exposure to hands or other
specific organs are likely to exceed whole body exposure.
- The internal dosimetry (bioassay) program covers
a potential intake of radionuclides.
- Direct reading external dosimeters are used for short
term exposure at high radiation areas.
Classification of Individuals Addressed by the Dosimetry
Program: The large majority of employees and
students at the University are not exposed to ionizing
radiation
and thus, are not covered by the dosimetry program.
The remainder of individuals is classified into three
groups as follows:
Required to wear dosimeters:
- Adults who are likely to receive an
annual effective dose equivalent of 100 mrem (1
mSv) - included is
the committed effective dose equivalent of internally
deposited radionuclides
- Minors or pregnant women who are likely to receive
an annual dose equivalent of 50 mrem (0.5 mSv)
May request a dosimeter:
- Adults who are likely to receive a
radiation exposure, but their annual exposure is
likely to be less than
an effective dose equivalent of 100 mrem (1mSv)
- Minors and pregnant women who work in the vicinity
of a radiation source, but are unlikely to receive
an annual dose equivalent of 50 mrem (0.5mSv)
Assessment Process: It is recognized that a great
deal of judgment is required to place an individual in
a group and to apply a specific method
of monitoring. These decisions are made by the Radiation
Safety Officer as recommended by the Radiation Safety
Committee based on the following criteria:
- Exposure history of individual and similar workers
- Work habits
- Nature of the work
- Quantity of radioactive materials
and/or strength of radiation source
- Other relevant parameters
The placement of an individual is reassessed as needed
by the Radiation Safety Committee as recommended by the
Radiation Safety Officer.
Pregnant
Workers:
University policy relies upon the ALARA principle,
thus reducing the necessity for a special policy for
pregnant women. However, there is a recognition that
a pregnant worker may require specific information to
make an informed decision. The Fetal Protection Program
is described in detail in Procedure 1.4.
- To be considered under the Pregnant Worker policy,
a woman must declare her pregnancy in writing and
provide other relevant information , e.g., approximate
date of conception or delivery.
- EHS will provide counselling if desired.
- The worker will be assigned a monthly
fetal monitoring dosimeter.
- In the event of elevated edposures, the RSO may seek
reassignment of duties.
- Please
read the following: "INSTRUCTION
CONCERNING PRENATAL RADIATION EXPOSURE". Adobe
PDF document.
Exposure Reports: The Radiation Safety Officer
reviews exposures on a regular basis. Subsequently, high
or unusual exposures are reported to the Radiation
Safety Committee. All monitored individuals included
receive an annual exposure report.
Enforcement of External Dosimetry Program:
External dosimeters will be provided to required
individuals on an appropriate basis i.e., monthly
or quarterly. All
individuals in
this group are required to promptly return the dosimeters.
A delay by more than one month in returning the dosimeter
without a written explanation may be considered a violation
of University policy and may lead to the revocation of
authorization to use radioactive materials or a monetary
penalty.
Individuals that are assigned dosimeters due to voluntary
request are required to comply with all policies
governing monitored individuals. This
group is also expected to return the dosimeter promptly.
Failure
to return a dosimeter by more than one month may be considered
a violation of University policy.
Internal Dosimetry Program:
- Applies to anyone utilizing 1 mCi or more of unsealed radioiodine or 100 mCi or more of unsealed tritium.
- Applies to anyone involved in an accident or
spill who become personally contaminated.
Enforcement of Internal Dosimetry Program: The
method and the frequency of bioassay depends upon the
nature including the half-life of the radionuclide of
concern. Once the frequency of bioassay is established,
the enforcement follows the external dosimetry enforcement
by replacing the month with the appropriate interval
(e.g. 14 days). |
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