United States Nuclear Regulatory Commission - Protecting People and the Environment

U.S. Nuclear Regulatory Commission

Question 26 (a): There has been some confusion about the

revised Part 20 requirements with respect to controlled

areas and when individuals are receiving a public or an

occupational dose. Before asking questions involving

specific exposure scenarios (in parts b, c, and d of this

question), does the NRC staff have any general guidance on

these topics?



Answer: Anyone attempting to answer questions about which

dose limits apply in a particular situation should be

familiar with the requirements of 10 CFR 20.1201, 10 CFR

20.1207, 10 CFR 20.1208, and 10 CFR 20.1301, and with the

definitions of the following terms in 10 CFR 20.1003:

occupational dose, public dose, member of the public,

restricted area, controlled area, and unrestricted area.



Occupational Dose vs. Public Dose



By definition, and with the exceptions given in the

definitions of "occupational dose", any dose received by

any individual in a "restricted area" is an "occupational

dose." No one in a restricted area is a "member of the

public." Outside "restricted areas" (i.e., in "controlled

areas" or in "unrestricted areas"), whether the dose to an

individual is an "occupational dose" or a "public dose"

depends on whether the dose received by the individual is

(as specified in the definition of "occupational dose") a

dose received "in the course of employment in which the

individual's assigned duties involve exposure to radiation

and to radioactive material from licensed and unlicensed

sources of radiation, whether in the possession of the

licensee or other person." In other words, outside

"restricted areas", whether the dose to an individual is an

"occupational dose" or a "public dose" (and whether the

occupational dose limits or the public dose limits apply to

the individual) depends on what the individual is doing and

not on what area (controlled or unrestricted area) the

individual is in when the dose is received.



Different understandings of the meaning of the second part

of the definition of "occupational dose" (which begins ". .

. or in the course of employment . . .") has been a source

of much of the confusion with respect to applicable dose

limits. Generally, this part of the definition does not

mean that any dose received by an individual while working,

regardless of the type of work, is an "occupational dose."

Doses received by an individual while working outside a

restricted area (in a controlled or unrestricted area)

usually would be categorized as public dose when the dose

received is within the public dose limit (and is not likely

to exceed that limit) and the work being done is not

closely connected (i.e., is only casually connected) to the

licensed activity.



Licensee Discretion



The regulations (revised Part 20) allow licensees a certain

amount of discretion in developing a radiation protection

program that is suitable and practical to implement at the

licensee's location and for the licensee's particular set

of working conditions. For example, licensees are permitted

by the regulations to select the boundaries for restricted

areas and controlled areas. (Because licensees are not

required by 10 CFR Part 20 to have controlled areas they

may choose whether or not to have controlled areas.) When

an individual is to work in a controlled area or an

unrestricted area, the licensee should evaluate the

individual's assigned duties and determine whether a dose

would be categorized as a public dose or an occupational

dose in accordance with the definitions of these terms in

10 CFR 20.1003.



The following criteria that include both regulatory

requirements and basic radiation protection philosophy will

be used in the NRC inspection program.



Restricted Area



When an area satisfies both the definition of a

restricted area in Part 20 and the definition of a

protected area in Part 73, it is considered to be a

restricted area for purposes of compliance with 10 CFR Part

20.



Boundaries of restricted areas may be selected by

licensees but being selected, they should be documented

(recorded) (good practice).



Access to restricted areas must be controlled,

e.g., by barriers, signs, or guards (§20.1003). Note:

Areas that can have personnel access controlled but that

are not being controlled (e.g., because the radiation

source has been removed) are not restricted areas.



Posting of a restricted area as a restricted area

is not required although other posting may be required

within the area (§20.1902).



Doses received by all individuals in restricted

areas are occupational doses (§20.1003).



Individuals working in or frequenting a restricted

area must be provided training, as appropriate (§19.12).



Individuals entering a restricted area must be

informed that they are subject to occupational dose limits.



Effort must be made to maintain all doses ALARA

(§20.1101).



A decision must be made as to whether monitoring is

required (§20.1502).



Controlled Area



Controlled areas are not required (§20.1003).



As indicated in the preceding section, an area that

satisfies both the definition of a restricted area and the

definition of a controlled area is considered to be a

restricted area for purposes of compliance with 10 CFR Part

20.



Boundaries of controlled areas may be selected by

licensees but should be documented (recorded) (good

practice).



Posting of a controlled area as a controlled area

is not required (§20.1902).



Doses received in controlled areas may be occupational

doses or public doses. Generally doses will be public doses

except when the licensee determines that an individual

receives exposure to radiation "in the course of employment

. . . ." [§20.1003, §§20.1301 (b)].



Doses are to be categorized as public doses (i.e., public

dose limits apply) whenever reasonable and practical (good

practice) (except for occupational doses).



In determining whether an individual in a controlled area

is to be categorized as an individual who receives an

occupational dose or as a member of the general public, the

more difficult decisions concern individuals who may be

occasionally exposed or whose assigned duties are not

closely connected to the licensed activity. Such

individuals include messengers, delivery men and women,

custodial workers, secretaries, clerical workers, hospital

volunteers, etc. Usually, such individuals are considered

to be members of the public and the doses they receive are

well within the limits for members of the public. However,

if the assigned duties of these individuals are closely and

frequently connected to the licensed activity, and their

doses may approach or exceed the limits for members of the

public, the doses such individuals receive are better

treated as occupational doses. Only when doses are to be

categorized as occupational doses (i.e., occupational dose

limits apply) do the following conditions apply: - A

decision must be made as to whether monitoring is required

(§20.1502).



- The licensee should have the ability to exercise positive

control over the individual's activities in the controlled

area.



- The licensee should provide appropriate

instructions.



- The licensee should inform the individual that he/she is

subject to occupational dose limits rather than public dose

limits (§19.12-this is an implied requirement).



Individual Members of the Public



Individuals in controlled areas and unrestricted areas are

members of the public unless they are receiving an

occupational dose (§20.1003 & §20.1301). Licensees should

apply lower dose limits (public dose limits) to non-workers

whenever possible and reasonable (good practice). An

individual is not a member of the public when they enter a

restricted area (§20.1003).

Effort must be made to achieve doses that are ALARA

(§20.1101).



Question 26 (b): Do occupational dose limits or public

dose limits apply to the doses received by the individuals

described in the following scenarios for nuclear power

plants?



1. Assume an individual employed by a licensee working at

a two-unit site (one nuclear plant and one fossil plant) is

permanently employed at the fossil plant, which is inside

the nuclear plant's controlled area. The individual does

not enter any restricted areas. What dose limits apply to

that individual while working at the fossil plant?



2. What dose limits apply to a pregnant taxi driver while

she is picking up and discharging passengers within the

controlled area (outside the restricted area) of a nuclear

power plant?



3. What dose limits apply (a) to construction workers who

are building a second nuclear power plant within the

controlled area (outside the restricted area) of the first

nuclear power plant at that site and (b) to secretaries in

the administrative building within the controlled area

(outside the restricted area)?



Answer: For scenarios #1, 2, and 3, the dose limits for

members of the public apply. However, if turbine shine

from the nuclear plant is such that the individuals in

scenarios #1 (fossil plant workers) and #3 (construction

workers and secretaries) are likely to exceed the dose

limits for members of the public, the licensee should

consider the individual doses to be occupational doses and

meet the requirements for individuals who receive

occupational doses.



Question 26 (c): Do occupational dose limits or public

dose limits apply to the doses received by the individuals

described in the following scenarios for a hospital?



A hospital has defined a controlled area as all areas

within the main building. These areas can only be accessed

by doors which open to the outside environment. In

addition, they have designated the hot lab as a restricted

area. The hot lab can only be accessed through the nuclear

medicine department.



1. Individual A is a maintenance worker. He is employed

by the hospital and has been assigned to repair ventilation

ducts in the nuclear medicine (NM) department. The job

must be performed during normal work hours; patient

procedures will not be rescheduled. The ducts are not used

to ventilate the hot lab.



2. Individual B is an emergency room nurse employed by the

hospital. On frequent occasions she accompanies patients

to the nuclear medicine department for emergency lung scans.



3. Individual C is not employed by the hospital but visits

the hospital on a weekly basis for the purpose of

performing preventive maintenance on the gamma cameras. He

frequently observes the nuclear medicine technologist

during patient studies to verify equipment operation.



4. Individual D is employed by the hospital as a

caretaker. During the summer he routinely cuts the grass

outside the hospital. Note: The hot lab has at least one

outside wall.



Answer: Occupational dose limits apply to individuals B

(emergency room nurse) and C (who maintains gamma cameras).

The assigned duties of individuals B and C are closely and

frequently connected to the licensed activities. Limits

for members of the public apply to Individuals A (who

repairs a ventilation duct) and D (caretaker who cuts

grass). The assigned duties of Individuals A and D are

only remotely (and, in the case of Individual A,

infrequently), connected to the licensed activity and it is

reasonable and practical to apply the public dose limits.



Question 26 (d): Do occupational doses limits or public

dose limits apply to the doses received by the individuals

described in the following scenarios for a radiography

company?



A large radiography company performs radiography both in

the field and in a hot cell within its plant. The hot cell

is located in the delivery bay. The company shares its

physical plant with an affiliated company. UPS deliveries

for both companies come to the same bay area. The

radiography company has defined its restricted area to be

the hot cell and its controlled area to be the delivery bay.



1. Individual E is a secretary employed by the radiography

company. Her desk, where she performs all administrative

assignments, is located in the delivery bay, adjacent to

the hot cell.



2. Individual F is a data entry clerk at the affiliated

company. He is employed by a temporary agency on a

12-month assignment. He is responsible for picking up all

UPS shipments (within the controlled area).



3. Individual G is a co-worker of Individual E. He

frequently enters Individual E's office to use the

telephone to make personal calls during the course of a

normal work day.



Answer: Individual E (secretary): Assuming that the

secretary's location near a hot cell is essential, the

occupational dose limits apply.



Individual F (clerk): Limits for the general public apply.

There is only a casual connection between the individual's

assigned duties and the licensed activity that results in

the individual's exposure.



Individual G (co-worker): This individual is subject to

the dose limits for a member of the general public. He has

not entered a restricted area and his assigned duties do

not involve exposure to radiation and to radioactive

material from licensed and unlicensed sources of radiation.

(Reference: 10 CFR 20.1003)









Page Last Reviewed/Updated Thursday, March 29, 2012