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Submitted by Jun-Ichiro Tada, Task Force of the Coterie of Radiation Protection (Hoshasen Bogo Kenkyukai)
   Commenting on behalf of the organisation
Document 2005 ICRP Recommendation
 
I. Comments from the Task Force

1. Relation between dose constraints and dose limits

The relation is not clear enough. It seems ICRP’s measure to protect men from undesired effects associated with radiation exposure that occupational exposures be controlled through so-called radiation monitoring of space where they possibly access and through so-called individual dose monitoring, and exposures to members of the public be controlled through the monitoring of space. The monitoring of received dose is of individual-related approach and the monitoring of space source-related approach. It should be stated that “limits” are for monitoring of individual doses and “constraints” for designing and monitoring of radiation levels in space

We think the Figure 2 in the draft is not adequate for conveying the idea of ICRP to the people and in addition we think there is some room to brush-up the idea itself. So, we propose a new scheme instead as shown below.

..........Table 1. Limits and Constraints of Dose as Means for Exposure Control
......................................Measure for Space Safety Control..........Measure for Received Risk Control
Type of Exposure...........Dose Constraints....................................Dose Limits
...upon discretion................--.............................................................avoid severe effect
...emergency exposure.......--..............................................................[category DA]
...controlled exposure.........[category CA]...........................................[category DB]
...uncontrolled exposure.....[category CB]...........................................--
...from exempt or
.....“clearanced” source......[category CC]...........................................--


2. Proposed values for the maximum dose constraints and dose limits

We believe values proposed are too low for the indicated purposes. Our counter proposals, avoiding drastic discontinuity, are as follows:

...........Table 2. Proposed Values of maximum dose constraints and limits
Category...Values of maximum dose constraints and limits
DA.............500 mSv of effective dose per 1 year
DB.............50 mSv of effective dose per 1 year
CA.............1.0 mSv of effective dose per 1 week (no more than 50 mSv per 1 year)
CB.............0.1 mSv of effective dose per 1 week (no more than 5 mSv per 1 year)
CC.............0.01 mSv of effective dose per 1 week (no more than 0.5 mSv per 1 year)

Our proposal is to replace the figures {100, 20, 1, 0.01} [mSv/a] shown in the draft as the maximum dose constraints by new ones {500, 50, 5, 0.5} [mSv/a] with proposals of using “dose limits” for controlling criteria of individual dose and “dose constraints” for controlling criteria of spatial dose. As the time span for setting controlling criteria of spatial dose, 1 week is adopted, since 1 year is too long for treating shooting-star outside visitors.

It is human rights to avoid risk and to pursue benefit. Too low dose limits infringes the right to the pursuit of benefit. Risk to individuals should be left to individual’s discretion, as far as he has enough knowledge and means to control the risk, upon premise that no nuisance is given to any third person. On the other hand, it is desirable to restrict to use the right to pursuit of benefit, from paternalistic view point. Apparently the proposed value of 20 mSv/a as the maximum of dose constraints for occupational exposure is too low.

3. Changes in concepts of quantities

In ICRP system, weighted doses are introduced and used. In the draft, it is proposed to change values of weighting factors. From academic view point, this means change of the quantity.

In case you insist to use the old name to a new quantity, it is to be proposed to state the quantity as, for example, “effective dose 1990”, “effective dose 2005” and so on with abbreviation of E90, E05 and so forth.

II. Specific Comments from Members of the Task Force

1. Need for cancer-risk independent logic in delivering restriction values [Tada, JunIchiro]

Whether a cancer is fatal or not depends on the level of available medical care and the art in medicine is daily progressing. Thus the risk of low-level radiation exposure will be reduced according to the improvement of cancer curability. Consequently, the logic that delivers dose restriction values from fatal cancer induction risk brings instability into the system of radiation protection. Another logic independent of the state of art in medicine is necessary to determine the restriction values.

2. Upon a single dose-effect relation [Katoh, Kazuaki]

In the draft, plural relations between dose and effect, as in the current system. System constructed on a single relation is desirable.

3. Concept of “a single source” [Katoh, Kazuaki]

It is very difficult to apply the concept of “a single source” to practices. So, we propose to replace the expression “a single source” by “an control of exposure made by a single RSO (=Radiation Safety Officer, or equivalent) ”.

4. Relation between ICRP and ICRU [Katoh, Kazuaki]

In OECD-NEA Symposium held in Tokyo 2004, Professor Roger Clarke, Chairman of ICRP, told ICRP is still under ICR

As is well known, the system of radiation protection consists of two sub-system of system of radiation dosimetry and system of dose limitation. Hence, ICR founded two bodies of ICRU and ICRP. The roles of these two bodies were very clear in the beginning. But they began to invade the other’s territories each other. [The expression “radiation protection” is used to include “radiological protection”. In active radiation protection, protection of materials is also important.]

The issues of quantities and units are not subjects to be closed in any specific field as radiological protection. ICR should pay attention to this problem

5. Relation between ICRP and IAEA, WHO, etc. [Katoh, Kazuaki]

Professor Clarke also mentioned in Tokyo NEA Symposium that ICRP cannot consider the efforts devoted to make international consensus yielding e.g. BSS. This sounds ICRP degraded to a subordinate to these international organizations.

ICRP has been understood as an independent organization and it has kept its authority through its outcomes. If it changes its stance, they claim the way of operating the body, for example, the way of selecting members of the main commission as well as committees.

6. Change of name of the quantity, “ equivalent dose” [Katoh, Kazuaki]

As far as effective dose does not exceed the controlling criteria, deterministic effects are prevented in most cases. This was proved by the experiences in the past half century. Therefore, we propose to use only one quantity for the system of radiation protection. We give the name “protection dose” to this quantity tentatively. The effective dose in the current system can be used as this quantity but it had better be defined as a weighted particle fluence from metrological point of view.

Deterministic effects in present ICRP terminology are subject in case of accident or failure of safety control, and the main concern is of medical care, where information of absorbed dose and quality of radiation are needed.

In addition, so-called deterministic effects are not necessarily accumulative and not necessarily adequate to give controlling criteria in unit of dose per long term as one year in parallel with those to the stochastic effect.