Re: FW: ICRP Discussion paper

[andrew_mcewan@nrl.moh.govt.nz]

Hi Nick

Your post to ARPS does not appear to have reached me.

Nick Tsurikov wrote
"Now, let's have a look on Table 2 on page 17.  What it's saying to me that
if the dose for a worker in a 'practice' is 9.95 mSv/year - I do not need to
do anything at all - "no further action"...  And if the dose in a practice
is about 95 mSv/year I will need to either "plan to reduce the dose" or
"consider reducing the dose"...
IS THIS WHAT I THINK IT IS? DOES ICRP PLANNING TO INTRODUCE A KIND OF AN
EFFECTIVE "THERSHOLD"...?"

Table 2 of Roger Clarke's discussion paper has a tentative scheme of action banding at different levels ot total annual dose.  The actions are divided
into those arising from "optional" sources and those arising from "unavoidable" sources.  It was pointed out at the October 2000 ICRP meeting that
these distinctions are those in existing ICRP publications of "practices" and "interventions".  For interventions ICRP Publication 82 proposes that
intervention is unlikely to be justified below a generic level of about 10 mSv per year, i.e. if the natural BG rate is of this order no-one is likely
to feel the need to get up and move house.   However, for public exposures from unavoidable sources the possibility of cost-effective (using cost in
its widest sense) should still be explored.  Hence the entry of "consider reducing the dose" for public unavoidable exposures.  In the case of workers
where the exposures are unavoidable (e.g. aircrew, miners) the annual doses are well below the dose limit for workers and it is not practicable to
reduce them.  It may be noted that the banding (Band 4) is for doses in the range 1-10 mSv, and clearly more attention would be given to doses at the
higher end of the range.

In the case of practices, which are additional doses arising from intended activities, doses to the public should be reduced, hence the entry "reduce
the dose".  For workers exposed in practices the principle of ALARA would dictate that exploration of cost-effective reductions in dose should be
explored.  It was noted at the ICRP meeting that the entry "no further action" was in this case incorrect.

The discussion paper has perhaps gained a life wider than its original intention.  It was used by Roger Clarke as a discussion basis to introduce his
perception of areas of the ICRP Recommendations which should be revisited  with a view to developing new Recommendations in around 4-5 years.   Task
Groups of the incoming Committees will be established to work through these issues.  It would be inappropriate to read too much into the meeting
discussion paper or view it as an indicator of what will appear in new Recommendations.

Andrew McEwan

_________________________
Andrew C McEwan PhD
National Radiation Laboratory
PO Box 25-099
Christchurch, New Zealand

Ph 64 3 366 5059
Fax 64 3 366 1156
Andrew_McEwan@nrl.moh.govt.nz


************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html