The requirements for control of access to very high radiation
areas at non-self-shielded irradiators are as follows.
025.01
NON-SELF-SHIELDED
IRRADIATORS. 180 NAC
4-025 applies to licensees or
registrants with sources of radiation in non-self-shielded irradiators. 180 NAC
4-025 does not apply to sources of
radiation that are used in teletherapy, in industrial radiography, or in
completely self-shielded irradiators in which the source of radiation is both
stored and operated within the same shielding radiation barrier and, in the
designed configuration of the irradiator, is always physically inaccessible to
any individual and cannot create high levels of radiation in an area that is
accessible to any individual.
025.02
AREA
CONTROLS. Each area in which there may exist radiation levels in
excess of 5 Gy (500 rad) in 1 hour at 1 meter from a source of radiation that
is used to irradiate materials must meet the following requirements.
025.02(A)
ENTRANCE OR ACCESS
POINT. Each entrance or access point must be equipped with entry
control devices that:
(i) Function
automatically to prevent any individual from inadvertently entering a very high
radiation area;
(ii) Permit
deliberate entry into the area only after a control device is actuated that
causes the radiation level within the area, from the source of radiation, to be
reduced below that at which it would be possible for an individual to receive a
deep dose equivalent in excess of 1 mSv ( 0.1 rem) in 1 hour; and
(iii) Prevent operation of the source of
radiation if it would produce radiation levels in the area that could result in
a deep dose equivalent to an individual in excess of 1 mSv ( 0.1 rem) in 1
hour.
025.02(B)
ADDITIONAL CONTROL DEVICES. Be provided with
additional control devices upon failure of the entry control devices to
function as required by 180 NAC 4-025.02(A):
(i) The radiation level within the area, from
the source of radiation, is reduced below that at which it would be possible
for an individual to receive a deep dose equivalent in excess of 1 mSv ( 0.1
rem) in 1 hour; and
(ii)
Conspicuous visible and audible alarm signals are generated to make an
individual attempting to enter the area aware of the hazard and at least one
other authorized individual, who is physically present, familiar with the
activity, and prepared to render or summon assistance, aware of the failure of
the entry control devices.
025.02(C)
FAILURE OR REMOVAL OF
PHYSICAL RADIATION BARRIERS. The licensee or registrant must
provide control devices so that, upon failure or removal of physical radiation
barriers:
(i) The radiation level from the
source of radiation is reduced below that at which it would be possible for an
individual to receive a deep dose equivalent in excess of 1 mSv ( 0.1 rem) in 1
hour; and
(ii) Conspicuous visible
and audible alarm signals are generated to make potentially affected
individuals aware of the hazard and the licensee or registrant or at least one
other individual, who is familiar with the activity and prepared to render or
summon assistance, aware of the failure or removal of the physical
barrier.
025.02(D)
PERMANENT STRUCTURAL COMPONENTS. Physical radiation
barriers that comprise permanent structural components or walls that have no
credible probability of failure or removal in ordinary circumstances need not
meet the requirements of 180 NAC 4-025.02(C).
025.02(E)
VISIBLE AND AUDIBLE
ALARMS. Each area must be equipped with devices that will
automatically generate conspicuous visible and audible alarm signals to alert
personnel in the area before the source of radiation can be put into operation
and in time for any individual in the area to operate a clearly identified
control device, which must be installed in the area and which can prevent the
source of radiation from being put into operation.
025.02(F)
AREA
CONTROLS. Each area must be controlled by use of such
administrative procedures and such devices as are necessary to ensure that the
area is cleared of personnel prior to each use of the source of
radiation.
025.02(G)
RADIATION MEASUREMENT. Each area must be checked by a radiation
measurement to ensure that, prior to the first individual's entry into the area
after any use of the source of radiation, the radiation level from the source
of radiation in the area is below that at which it would be possible for an
individual to receive a deep dose equivalent in excess of 1 mSv ( 0.1 rem) in 1
hour.
025.02(H)
ENTRY
CONTROL DEVICE TESTING. The entry control devices required in 180
NAC 4-025.02(A), must have been tested for proper functioning:
(i) Testing must be conducted prior to
initial operation with the source of radiation on any day, unless operations
were continued uninterrupted from the previous day;
(ii) Testing must be conducted prior to
resumption of operation of the source of radiation after any unintentional
interruption; and
(iii) The
licensee or registrant must submit and adhere to a schedule for periodic tests
of the entry control and warning systems.
025.02(I)
FUNCTIONING CONTROL
DEVICES. The licensee or registrant must not conduct operations,
other than those necessary to place the source of radiation in safe condition
or to effect repairs on controls, unless control devices are functioning
properly.
025.02(J)
ENTRY AND EXIT PORTALS. Entry and exit portals that are used in
transporting materials to and from the irradiation area, and that are not
intended for use by individuals, must be controlled by such devices and
administrative procedures as are necessary to physically protect and warn
against inadvertent entry by any individual through these portals.
025.03
ALTERNATIVE
SAFETY MEASURES. Registrants or applicants for registrations for
sources of radiation within the scope of 180 NAC 4-025.02 that will be used in
a variety of positions or in locations that make it impracticable to comply
with certain requirements of 180 NAC 4-025.02, may apply to the Department for
approval of alternative safety measures. Alternative safety measures must
provide personnel protection at least equivalent to those specified in 180 NAC
4-025.02. At least one of the alternative measures must include an
entrypreventing interlock control based on a measurement of the radiation that
ensures the absence of high radiation levels before an individual can gain
access to the area where such sources of radiation are used.
025.04
ENTRY CONTROL
DEVICES. The entry control devices required by 180 NAC 4025.02 and
4-025.03 must be established in such a way that no individual will be prevented
from leaving the area.
