Re: Sealed Source Definition

[Lester.Slaback@nist.gov]

One can find a variety of definitions, depending on the intended purpose.
May I suggest that we establish that purpose before looking for the
applicable definition.  Several possibilities......

1. to determine when infrequent surveillance simply to test containment is
to be the only safety surveillance (as opposed to the surveillance needed
for the use of unsealed/uncontained materials).  In this context a liquid
in a glass vial could certainly be considered a sealed source.
2. to describe a source that can withstand a specified level of
abuse/lack-of-
careful-handling.  DoT's special form might be an example.
3. to describe sources for which one cannot assure knowledgeable
surveillance or cannot presume trained usage.  Some of the regulatory
def's start with this presumption.

The IEC std on sealed sources in fact provides 3 or 4 levels of definition
for sealed sources, reflecting increasing levels of containment.

For the routine, laboratory-type usage I like the definition where "...
the material is contained adequately for its intended usage."

Within a given regulatory framework (NRC,DoE) you can lose flexibility
unless you have provided a specific definition appropriate for your
activities as part of your approved procedures or licensing document.

>     
>     I personally use the definition of sealed source given in Reg Guide 
>     10.11 where it states, "... a sealed source is radioactive material 
>     that is sealed in a protective envelope (capsule), contained in a 
>     foil, or plated on an inactive surface.  The term 'sealed source' or

>     'source' includes the radioactive material and its confining
>barrier, 
>     i.e., the capsule, foil, or plated surface.  The confining barrier
>is 
>     relied on to prevent dispersion of the radioactive material under 
>     normal conditions for use of the source and most accident
>conditions."
>     
>     Kit Weaver

-- 
the above are the personal musing of the author,
and do not represent any past, current, or future
position of NIST, the U.S. Government, or anyone else
who might think that they are in a position of authority.
NBSR Health Physics
NIST
Gaithersburg, MD 20899
301 975-5810
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Lester.Slaback@nist.gov
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