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Re:
I am using ICRP and IAEA concepts. Each country, accepting the concepts of
these documents should select the way to assure compliance with. In terms of
public, dose constraints for sources within practices are expressed as an
additional annual dose lower than 1 mSv and in principle should be
established on case-by-case, e.g. for a single source of ~0.3mSv, which
could be ~0.1 mSv for the prolonged exposure.
Jose Julio Rozental
joseroze@netvision.net.il
Israel
----- Original Message -----
From: <Jack_Earley@RL.gov>
To: <joseroze@NETVISION.NET.IL>; <radsafe@list.vanderbilt.edu>
Sent: Saturday, February 16, 2002 5:13 PM
Subject: RE:
<<Generally, taken the above into consideration, the constraint varies from
10 to 30% of the dose limit.>>
<<Finally, if the Dose Constraint is exceeded it is necessary taken action
to prevent recurrence, however the dose limit will not be exceeded. In this
case there is not enforcement by the Regulatory Authority. However exceeding
the limit, of coarse it will be also necessary actions however in this case
generally the Regulatory Authority applies enforcement.>>
You seem to be referring to two different approaches, i.e., dose estimates
for a given job, and administrative limits/guidelines that are set to
prevent exceeding dose limits. Dose estimates are based on the time in a
given work area w/ a defined exposure rate. Being high or low by 25 percent
or more, for example, can trigger an investigation to determine why the
estimate was wrong.
Administrative limits, which can be exceeded w/ concurrence from management,
are generally set at 75 to 80 percent of the dose limit. This varies
depending on the levels of management required to be involved.
Jack Earley
Radiological Engineer
-----Original Message-----
From: J. J. Rozental [mailto:joseroze@NETVISION.NET.IL]
Sent: Saturday, February 16, 2002 2:43 AM
To: radsafe@list.vanderbilt.edu
Subject: Re:
Dear colleagues,
Seem to me that some colleagues are making confusion between dose limit and
dose constraint.
If there is not a good understand on dose constraint surely it is necessary
refreshment, because dose constraint is fundamental objective of the
optimization.
Is dose constraint a dose limit – No, constraint should not be confused with
the limit. Dose limit is the dose that an individual could receive from the
whole of the practices to which he/she can be exposed at the present. The
concept of “dose constraint” was explicitly introduced in ICRP 60 within the
context of optimization of protection. This concept, however, is not new and
its introduction corresponds, rather, to an attempt to consolidate and
rationalize a variety of concepts that already existed in previous ICRP
guidance.
A dose constraint is the value of individual dose that is expected not to be
exceeded in the predicted individual dose distribution resulting from the
optimization process. Dose constraints needs to be applied in the planning
of protection in all situations where optimization is involved, as design or
modification of plants, preparation of an operation, or to release of
airborne radioactive effluents to the environment, etc. The dose constraint
may be related to:
A source such a simple small one, a single machine or a big installation;
A set of sources in an installation;
A particular task in connection with a source or set of sources, or a
complete job, such as a specified maintenance task, or a group of operations
in a specific type of industry
Examples, Industrial radiography in urban zone, Use of radioactive tracer in
hydrology, incineration of waste, etc
In each case, those who establish constraints must clearly describe the
relevant source, and the magnitude of the constraint selected should be
appropriate to the purpose in hand
Generally, taken the above into consideration, the constraint varies from 10
to 30% of the dose limit
In the case of public exposure, object of the discussion, what is more
important for member of the public: Dose Constraint or Dose Limit?
According with ICRP, for public exposure the constraints are more important
than the limits, because public can be submitted to sources of other
practices, and the final dose received for the member of the public should
be never higher than de limit.
Example a person living near a nuclear Installation (member of the group
critical) and working in Hospital where practices of nuclear medicine are
authorized.
Finally, if the Dose Constraint is exceeded it is necessary taken action to
prevent recurrence, however the dose limit will not be exceeded. In this
case there is not enforcement by the Regulatory Authority. However exceeding
the limit, of coarse it will be also necessary actions however in this case
generally the Regulatory Authority applies enforcement.
Jose Julio Rozental
joseroze@netvision.net.il
Israel
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