Dose Limits

(Question Posted to ERAD in May 2012)

Who do you define as a member of the public for the onsite MEI?

This question implies that there may be more than one maximally exposed individual (MEI), one on-site and one off-site, when demonstrating compliance with the Public Dose Limit of DOE Order 458.1. Although all potential MEIs should be considered and documented, as well as the calculated doses and pathways considered, the intent of DOE Order 458.1 is in fact to ultimately identify only one MEI, a theoretical individual who could be either on-site or off-site.

The Order defines the MEI as "a hypothetical individual who - because of realistically assumed proximity, activities and living habits - would receive the highest radiation dose, taking into account all pathways, from a given event, process or facility." The Order further states in paragraph 4.e.(1)(a)2 that determination of the representative person or the MEI must include members of the public both on DOE sites outside of controlled areas and off DOE sites. As stated previously, the intent of the Order is to determine only one MEI for compliance calculations. Traditionally, the MEI is located off-site but it is possible for the MEI to be located on-site outside of controlled areas, especially on a large DOE site if the controlled area boundary is not near the site boundary or if members of the public work on DOE sites at locations outside of the controlled area.

Two other definitions from DOE O 458.1 are important in identifying the MEI:

• Member of the Public - an individual who is not a general employee. An individual is not a member of the public during any period in which the individual receives an occupational dose.
• General Employee - an individual who is either a DOE or DOE contractor employee; an employee of a subcontractor; or an individual who performs work for or in conjunction with DOE or utilizes DOE facilities.

It is important to note that general employees are members of the public when they are off-site and off duty. While on duty (assuming they are on-site as well), they would not be considered as the MEI.

So, exactly what type of individual could be determined to be the MEI located on a DOE site outside of controlled areas? Examples include: (1) recreational users (hikers, hunters, etc.), (2) members of the public who transit DOE property on open roads, (3) personnel who have access to DOE property that is outside a perimeter fence line, or (4) workers who utilize leased buildings on DOE property (termed co-located workers) but have no affiliation with DOE operations may be the MEI.

As a further note, a member of the public in a controlled area on-site (e.g. VIP tour visitor) is protected under 10 CFR 835 requirements and should not be used as the MEI.