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Privacy and Security Notice

Visitor Radiological Safety Guides

Welcome to Jefferson Lab

We hope your visit with us is both safe and enjoyable. Most of the areas you visit at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) will not expose you to radiation above normal background levels. However, you may be exposed to radiation if you enter a Radiologically Controlled Area (RCA) or handle radioactive material.

Some of the areas where you may encounter radiation are listed below. Briefly passing by or through these areas will not expose you to measurable radiation if you respect the designated boundaries as posted.

Possible Radiation Exposure Areas:

Radiation Safety Guidelines:

To minimize your exposure to radiation while at Jefferson Lab, simply follow these three guidelines:

Radiological Postings

All Radiologically Controlled Areas (RCAs) and Radioactive Material Areas (RMAs) are clearly identified by various signs and labels. Each radiological sign has the following characteristics:

Below are some examples of radiological signs at Jefferson Lab:

Yellow and magenta rope is also used to designate the boundaries of radiological areas. Any special requirements will be listed on the sign.

Individual items stored within a designated RCA do not need to be labeled as radioactive. It is important to consider all items within an RCA boundary as radioactive. Do not remove anything without specific permission from the Radiation Control            Department.  Radioactive material which is transported or stored outside an RCA must be controlled through the Jefferson      Lab Radiation Control Department's inventory system and must be appropriately labeled.


A dosimeter is a device which monitors the amount of radiation to which you are exposed. The areas into which you may enter are routinely monitored, and are not expected to expose you to any measurable radiation.


If you are given this dosimeter, you are being monitored for an official record. You must still be escorted, but you are allowed to work in a RCA and on radioactive materials, with your escortís direct observation.


Please do not press the button on the electronic dosimeter.


You will not be allowed to perform radiological work while wearing only one of these dosimeters.

Your Risks

Acceptance of a risk is a highly personal matter. It requires a good deal of informed judgment. The risks associated with occupational radiation doses are considered acceptable as compared to other occupational risks by virtually all the scientific groups who have studied them. The following chart may help you put the potential risk of radiation into perspective when compared to other occupations and daily activities.

Activity Estimated Living Days Lost
Smoking 20 cigarettes a day 6 years
Overweight by 15% 2 years
Alcohol consumption (U.S. average) 1 year
Occupational radiation dose (1 rem/y), from age 18-65 (47 rem total) 51 days
All natural hazards (earthquakes, lightning, flood) 7 days
Medical radiation 6 days
*Note: The "life expectancy lost" value is determined from data on percentage of deaths due to the risk factor weighted by the average age at death. Since radiation related deaths are calculated values, they are based on the assumption of cancer as the cause of death, with the associated average age of death from cancer victims.

Fetal Exposure

An embryo/fetus is especially sensitive to radiation. Limits are established to protect the embryo/fetus from any potential effects which may occur from a significant amount of radiation. This radiation exposure may be the result of exposure to external sources of radiation or internal sources of radioactive material. At current occupational dose limits, the actual probability of any effects occurring in the embryo/fetus from occupational exposure is small. As a visitor, the probability is infinitesimally small. There are no known heritable effects - i.e., occupationally exposed personnel have no known increase in birth defect rates.

ODH Briefing

Some areas that you may enter are classified as Oxygen Deficiency Hazards (ODH).  They may contain cryogens, or liquid gases, that expand greatly when they turn into gas.  These cryogens can replace all the local oxygen if this happens.  Although the probability of death due to this happening is very small (<1 in 10,000,000 per hour), you need to know the following danger signs:

If any of these occur, we ask that you quickly leave the area with your escort, making sure not to pass through any plume. If your escort is lost or unconscious, go out the nearest exit, making sure not to pass through any plume - do not try to remove any unconscious people from the area. Go to the nearest phone and dial 911 or 5822.

Do not enter ODH-2, ODH-3, or ODH-4 areas, even with an escort.