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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:

      In addition, please do not handle radioactive materials or bring any radioactive materials or sources onto the Jefferson Lab property.

Radiological Postings

Upon entering the CEBAF site, you will pass a large sign reading Controlled Area.

After this point, you must be with your escort at all times.  He/she will ensure that you do not go into any areas that are hazardous.

Do NOT enter the following areas, even with an escort:

All areas containing radioactive materials, radiation producing machines, or creating a measurable radiation level are clearly identified by various signs and labels. Each sign has the following characteristics:

Below are some examples of radiological signs at Jefferson Lab:

Yellow and magenta rope is often used to designate the boundaries of radiological areas.

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 an RCA and on radioactive materials, with your escortís direct observation.

If you are given this dosimeter, you may access RCAs with your escort, but you are NOT allowed to handle any radioactive materials or perform any radiological work.  Please do not press any buttons on the electronic dosimeter.

Notify your escort immediately if: 

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 put your potential risk from exposure to radiation into perspective based on the potential number of days of life lost.

Fetal Exposure

An embryo/fetus is especially sensitive to radiation. For radiological workers, limits are established to protect the embryo/fetus from any potential effects which may occur from a significant amount of radiation exposure. Such an exposure could be the result of exposure to external sources of radiation or internal sources of radioactive material. The probability of any effects occurring in the embryo/fetus from occupational exposure is small. For a visitor, the probability is infinitesimally small. In addition, you should know that the children of 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 (liquid gases) that expand greatly when they turn into gas. When this occurs, the cryogens can replace all the local oxygen supply.  Although the probability of death due to such an event is very small (<1 in 10,000,000 per hour), you need to know the danger signs.

If you see a blue strobe light, a white plume, or hear a loud buzzing alarm, quickly leave the area with your escort, making sure not to pass through the plume. If your escort is lost or unconscious, go out the nearest exit, making sure not to pass through the 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.

Safety/Emergency Information

You have a right to know about all the hazards you may encounter while at Jefferson Lab.  If you have further questions, please call the appropriate number.

Radiation Safety

Non-Radiation Safety Issues

Emergency Phone Number