Regulatory Definition Within the DOE of a "Radiation Producing Device"

[David W Lee <lee_david_w@lanl.gov>]

Radsafers Everywhere:

        Perhaps the many radsafers in the non-DOE world could help the DOE
to define what it means by the term it proposes to place into federal law,
but has not yet defined; namely, the term "Radiation Producing Device
(RPD)."  The following background information is provided:

        The present version of Title 10 CFR 835.2 specifies the following
definition of a "Radiological Worker":

        "Radiological Worker is a general employee whose job assignment
involves operation of radiation producing devices OR working with
radioactive materials, OR who is likely to be routinely occupationally
exposed above 0.1 rem (0.001 sievert) per year total effective dose equivalent."

        COMMENT:  In my opinion this existing DOE radiological worker
definition could be considerably improved by replacing the second "OR" with
the word "and."
 
        The major "problem" with this definition is that it declares people
who operate "radiation producing devices" (RPDs) to be "radiological
workers," but the term "radiation producing devices" is NEVER defined.  To
make matters worse, the "Definitions" section of the latest draft of the
proposed amendment to 10 CFR 835 does not contain any definition of an RPD
either.  Thus, one is left to speculate "what does DOE mean by the term
'RPD'"?  From a regulatory standpoint, what things within the DOE world
should be declared to be RPD's and regulated as such and what things should
be explicitly excluded?  DOE's RPD term makes no differentiation between an
"intentional" and an "incidental" x-ray producing device.

        According to the above DOE radiological worker definition, a
secretary could be construed to be a "radiological worker" because he/she
operates a radiation producing device, i.e., a computer video display
terminal (VDT).  Also, any person who operated a DOE-owned TV set, say for
example, during an ES&H training class, would also be a radiological worker
because the TV set produces ionizing radiation incidental to its primary
function.  The same could be said for an operator of an electron microscope
or an electron beam welder.

        Finally, the federal government in 21 CFR 1020.40 permits any member
of the public to buy intentional x-ray producing devices, called "cabinet"
x-ray machines, which are exactly the types of machines that check your
carry-on baggage at airports.  These machines are publicly available without
any sort of "license" or individual dosimetry required, because the
radiation emission standard that each of these machines must meet (less that
0.5 mrem in any one hour at 5 cm (2 inches) from any part of the exterior
surface of the machine) is so low that under any realistic exposure
scenario, a member of the public cannot be considered to realistically
sustain more than 100 mrem in a year.  Yet presently, because these machines
are so called "intentional" x-ray producing devices, the DOE wants them to
be regulated in the DOE work place like other types of intentional x-ray
devices.  All this despite the obvious fact that you or I, as private
citizens, can buy VDT's, TV sets, electron microscopes, gas and electron
beam welders, and cabinet x-ray machines, use them in our own homes if we
wish, and we don't have to regard ourselves as "radiological workers" who by
DOE's definition need to have some sort of Radworker training.  I realize
that some States may regulate these types of devices (registration, etc.),
but States tend to vary in the degree to which they choose to regulate, say,
an electron microscope.

        Based on DOE's latest declaration of its intentions; namely, to
persist with the same definition of a "Radiological Worker" in the upcoming
proposed amendment to 10 CFR 835 as in the present version of 10 CFR 835 and
to coin the term "RPD" into federal law without ever defining it, I think it
is important for us, as contractors within the DOE who will end up being
forced to live with the federal law RPD term, to come up with a definition
of an RPD and to ultimately submit it to DOE for inclusion in the final
amendment of 10 CFR 835.

        Coming up with a comprehensive definition of an RPD is not easy.
Many of us have a clear, gut-level understanding of what IS an RPD, but the
devil is in writing such a definition so as to clearly indicate what should
NOT be regulated as an RPD.

        The x-ray part of my job description puts me in the dubious position
of possibly having the greatest vested interest in clearly defining what an
RPD is and is not.  Accordingly, I am willing to take the lead in trying to
come up with a comprehensive definition of an RPD.  But I would sincerely
appreciate and earnestly solicit any input you and your radsafer colleagues
could provide me.  Please e-mail me direct at the e-mail address listed below.

        To start with, it would be useful to clearly define "what is an
x-ray machine" and "what is an accelerator" since each fall under different
ANSI standards.  But the problem is there are x-ray machines (which produce
x-rays) and there are electron accelerators (which only produce x-rays).  It
would seem logical that those electron accelerators dedicated to producing
x-rays only should fall under the broad definition of an "x-ray machine."  I
would expect that any definition of an "accelerator" to differentiate
between "big" SLAC-type accelerators and those 6--24 MeV electron
accelerators that are used only to produce x-rays.  Fundamentally, any
regulatory definition of an "accelerator" versus an "x-ray machine" hinges
upon whether one chooses to focus upon HOW the x-rays are produced or focus
merely on what comes out of the business end of the machine.

        Within the DOE, there is a lesson to be learned from the past.  DOE
previously defined what it called a "radiation-generating device (RGD) (Nov
94, G-10 Implementation Guide, Radiation-Generating Devices, page 4) which
lumped both intentional and incidental x-ray devices (apples and oranges)
under the same RGD umbrella and included those radioactive sealed sources
that were capable of producing greater than 100 mrem in 1 hour @ 1 foot
(those capable of creating a "High Radiation Area").  Since this RGD
definition included only those sealed sources capable of producing greater
than 100 mrem in 1 hour @ 1 foot, the implicit assumption was that any x-ray
producing device was capable of producing this same dose rate or greater, as
measured in the main, primary x-ray beam.

        The "problem" with this old RGD definition was that it was
essentially keyed to knowing the primary beam dose rate, and it implicitly
assumed that operators of such devices could actually be exposed to dose
rates in excess of 100 mrem in 1 hour @ 1 foot in the primary beam.  But the
issue with industrial x-ray machines is that most are located in shielded
rooms (facilities) the entrance doors to which must be electronically
interlocked.  The very definition and function of an interlock is to PREVENT
ACCESS to the primary x-ray beam when the machine is energized.

        For example, ANSI N43.3 permits an institution to buy a high-power
x-ray machine and install it inside some sort of radiography room.  If the
institution elects to build the facility walls sufficiently thick
(engineered controls) such that the x-ray facility operator is exposed to no
more than 0.5 mrem in any 1 hour at 2 inches from any portion of the
exterior surface of the facility walls when the x-ray system is operated at
its maximum, used operating technique factors, then the entire x-ray
facility can be classed under ANSI N43.3 as an "Exempt Shielded"
installation.  Obviously, the room entrance doors must have interlocks.  And
since operators do not spend their work days with their noses glued to the
exterior surface of any shield wall and since radiation exposure rate varies
inversely as the square of the distance away from the shield, ANSI N43.3
actually permits owners of such facilities NOT to have to provide the
operators with INDIVIDUAL dosimetry due to the virtual impossibility of the
operator of such an installation sustaining greater than 100 mrem in 1 year.

        It is no coincidence the ANSI N43.3 permits owners of "Exempt
Shielded" installations NOT to have to provide operators of such
installations any INDIVIDUAL dosimetry.  The rationale is that if you are
smart enough to spend your money on permanent engineered controls such that
your own people are exposed to no more than 0.5 mrem in any 1 hr @ 2 inches,
then ANSI will give you a break--you won't have to pay big bucks to buy some
sort of external dosimetry service to document a bunch of zero or near zero
quarterly doses.  Further, since "cabinet" x-ray machines are under the same
radiation emission standard, operators of these machines in airports do not
normally wear individual dosimeters.  Thus, when an "Exempt Shielded" or
"cabinet" x-ray facility/machine is operating, each is a radiation emitter
of sorts that is emitting (exposing) operators (humans) to the tune of 0.5
mrem in any 1 hour @ 2 inches from any exterior shielding wall surface.

        How meaningful, or operationally useful is it then to regulate such
a facility with the same degree of ES&H concern as you would a situation
where you had the same high-power x-ray unit being used outdoors in the
parking lot in an "open" (no permanent shielding) configuration?  Yet DOE's
RGD definition treats both x-ray devices the same because the RGD
definition, itself, is keyed to the radiation output capability of the
machine, itself, rather than to recognizing that the same x-ray machine can
be surrounded by differing degrees of radiation shielding/interlocks such
that an "Exempt Shielded" facility becomes of less ES&H concern compared to
the same machine used in an "open" environment.  DOE's old RGD definition in
effect ignores any shielding/interlocks associated with an x-ray machine; it
is oriented only on the machine itself through its focus on primary
radiation beam output. 

        The lesson, in my opinion, is that it does not make much sense to
define an RPD in terms of the radiation output of the machine, itself,
because the action/function of the facility access door interlocks is such
as to prevent any human from having access to the main radiation beam.  It
makes more sense to me to regulate RPD's according to the totality of the
environment in which they are used.  In other words, a high-power x-ray
device surrounded by massive shield walls/interlocks such that it is an
"Exempt Shielded" installation under ANSI N43.3 might ought to be classed as
a "low hazard" type installation due to the totality of all of the
engineered controls compared to a portable x-ray machine used out in the open.

        Perhaps, then, an RPD definition might be based upon the radiation
levels to which the operators are exposed (at the control panel area) during
actual operation of the RPD; RPD Class I might be "low hazard devices due
perhaps to mucho engineered controls," Class IV might be "high hazard
devices due perhaps to the basic lack of engineered controls," (open
installations), etc.  Also, it does not make much sense to me to regulate
certain types of x-ray producing devices in a DOE environment that have been
declared to be inherently safe by the federal government such that you and I
can freely buy them and exercise no further regulation/surveillance over
them, e.g., VDT's, cabinet x-ray systems, TV sets, etc.
   
Standard disclaimer--the above opinions expressed are strictly my own and
not necessarily those of the University of California or of the Department
of Energy.

THANKS.  Regards  


David W. Lee
Radiation Protection Policy
& Programs Analysis Group (ESH-12)
Los Alamos National Laboratory
PO Box 1663, MS K483
Los Alamos, NM  87545
Ph:  (505) 667-8085
FAX: (505) 667-9726