Re:

["J. J. Rozental" <joseroze@NETVISION.NET.IL>]

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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