TOPIC 6: Radiation Dose Limits

Let’s explore Radiation Dose Limits.

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The Nuclear Regulatory Commission (NRC) has determined a radiation worker can receive a radiation dose up to 5,000 mrem per year (5 rem/yr)

Even though the individual can receive this dose, the concepts of ALARA still apply. Notice in the following illustrations that some parts of the body are allowed more than 5 rem/yr. That can be confusing, but the 5 rem/yr limit is a whole-body average.

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THE ALARA level is 10% of the annual dose of 5,000 mrem/year which is 500 mrem/yr.  If the ALARA level is exceeded, it is not a violation.

However, it is the responsibility of the RSO to counsel the Authorized User and identify the tasks and work habits that may have contributed to his dose, and then to establish a methodology to reduce this exposure in the future.  This counseling session should be documented and subject to inspection by the regulatory agency.

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At five-year intervals, at the time of the renewal of the license, most agreement states and the Nuclear Regulatory Commission (USNRC) require a Member of the Public (or MOP) study be performed by the licensee to estimate the potential dose to non-occupationally exposed personnel (those are people who are not radiation workers but still work in the building, or the area, where there is a radioactive source).

This study uses survey readings, area monitors, and calculations of worst case scenarios to determine a Member of the Public will remain “safe.”

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All other employees that have not received training and all non-employees fall under the definition of member of the public. A member of the public can receive up to 100 mrem per year from a licensed activity (remember, this does not include the background dose we all receive naturally). Again, the concepts of ALARA still apply, but individual MOP doses are not monitored.

For a Radiation Worker, it is the radiation-monitored employee’s right to know how much exposure they have received. They should be encouraged to review their dose records if they have any concerns. Additionally, it is advisable to provide a dose record to employees on a yearly basis.

It is the responsibility of the radiation safety officer to account for the doses to the radiation workers. If using a third party dosimetry program, they most likely will perform this for you. If not, the RSO is the one that has to do it.