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Contained Source Radiation
Safety Training
Module
5: External Dose Limits
Annual Radiation Dose Limits
As Low As Reasonably Achievable (ALARA)
Declared Pregnant Worker Program
Annual Radiation Dose Limits (top)
The Nuclear Regulatory Commission (NRC)
and the New Jersey Department
of Environmental Protection (NJDEP) have established dose limits
which are based on recommendations from national and international commissions.
The table below lists the limits set by the NRC:
| Organ |
NRC Limit (mrem/year) |
University Investigation Level (mrem) |
Comments |
| Whole Body |
5000 |
100 |
Includes dose from both internal and external sources. The Whole
Body limit applies to exposure of the torso and head when the
radiation
is penetrating enough to irradiate tissues at a depth of 1 cm where
the deeper blood-forming tissues are located. |
| Lens of the Eye |
15,000 |
300 |
The Lens of the Eye limit applies to exposure of the eye to radiation
penetrating enough to irradiate the lens, at a depth of 0.3 cm. |
| Extremities |
50,000 |
1,000 |
The extremities include the arm or leg below the elbow or knee.
The Extremities limit applies to exposure of the extremities when
the radiation is penetrating enough to irradiate tissues at a depth
of 1 cm. |
| Skin |
50,000 |
1,000 |
The Skin limit applies to dose deposited in the skin when the
radiation is penetrating enough to irradiate tissues at a depth
of 0.007 cm. |
| Embryo/Fetus |
500 (for the entire pregnancy) |
50 |
Applies only when a Declaration
of Pregnancy has been submitted. |
| Occupational exposure of a minor |
10% of the limits above |
50 |
Applies to anyone under 18 years of age |
| Member of the general public |
100 |
50 |
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NJDEP Limits
NJDEP limits apply only to workers who use radiation-producing machines
and the few radioactive materials licensed by NJDEP. NJDEP limits do
not differ greatly from NRC limits.
Go to Table of NJDEP dose limits
Investigational Levels
The University has established investigational levels at doses considerably
less than the dose limits. When a worker accumulates during any part
of a year a dose at or above the investigational level, EHS will investigate
to determine causes of the dose and to recommend practices to minimize
radiation exposure in the future.
As Low As Reasonably Achievable (ALARA) (top)
Since the current model of radiation-induced cancer risk assumes that
there is a risk no matter how low the radiation dose, it makes good
sense to minimize radiation exposure. In fact, the University is required
by NRC regulation to keep doses As Low As Reasonably
Achievable (ALARA). This means that the University must work
to keep doses as far below the dose limits as can reasonably be achieved.
To keep doses ALARA, the University has established investigational
dose levels and will investigate any dose exceeding these levels
in an effort to address causes of unnecessary radiation exposure.
In addition there are a variety of practical steps that you can take
while working with contained sources to minimize your radiation exposure.
These steps will be described in detail in the Working
Safely with Contained or Plated Sources module.
Declared Pregnant Worker Program (top)
This section provides a general overview of the Declared Pregnant
Worker Program. More detailed information about the program is available
in
Section 6 of
the Radiation Safety Manual for Laboratory Workers. The NRC’s
Fetal Dose Regulations apply only to a woman who has voluntarily
informed her employer, in
writing,
of her pregnancy and the estimated date of conception. The dose to
the fetus resulting from occupational exposure of a declared pregnant
woman
may not exceed 500 mrem for the entire pregnancy.
Submitting a Declaration of Pregnancy
Any radiation worker who is pregnant or believes that she may be pregnant
should contact EHS. All inquiries will be kept in confidence. EHS will
take the following steps:
- Provide an opportunity to submit a Declaration of Pregnancy. (A
Declaration of Pregnancy form is included in the Radiation Safety
Manual or may be obtained from EHS.
- Provide information concerning risk of fetal radiation exposure.
- Evaluate
the worker’s dose history and
exposure potential.
- Make recommendations for reducing radiation exposure.
- Monitor
the worker’s radiation dose with
regard to worker and fetal dose limits.
For the type of radiation work performed at Princeton University, it
is rarely necessary to recommend reassignment or changes to job duties.
If a written
declaration of pregnancy is not submitted to EHS, then the worker’s
dose continues to be controlled under the normal dose limits for
radiation workers.
Go
to more detailed information about Princeton University's Declared
Pregnant Worker Program
This is the end of the Dose Limit Module, which is the
fifth of the seven Contained Source Radiation Basics training modules. The
next module is the Radiation Monitoring Badge Program module.
Go to Module 6 (Radiation Monitoring
Badge Program)
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