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 (�.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 (�.1902).
Doses received by all individuals in restricted
areas are occupational doses (�.1003).
Individuals working in or frequenting a restricted
area must be provided training, as appropriate (�.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
(�.1101).
A decision must be made as to whether monitoring is
required (�.1502).
Controlled Area
Controlled areas are not required (�.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 (�.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
. . . ." [�.1003, Ё20.1301 (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
(�.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 (�.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 (�.1003 & �.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 (�.1003).
Effort must be made to achieve doses that are ALARA
(�.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)