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Submitted by Carlo-Maria Castellani, ENEA Radiation Protection Institute
   Commenting as an individual
Document Occupational Intakes of Radionuclides Part 1
 

Comments to ICRP draft report  for consultation  “Occupational Intakes of Radionuclides. Part 1”


 


The document is well organized and provides the review of the biokinetic models applied in internal dosimetry and will be the reference document for their future application for retrospective dosimetric assessments.
My comments are mainly related with the computational tools for retrospective dose assessment.


I present them in ascending line number.


 


Line(s)          Comment or suggestion


757               Change the term “Minimum Detectable Activity” with “Detection Limit” in consideration to be in accordance to standard ISO 28218:2010 (see below).


 


860               Compare the value of breathing rate 1.2 m3/h to that of line 1458 i.e. 1.1. m3/h. Correct the value which is considered to be wrong. 


 


3407             As the unit is “eV” , change the “Mev” in “MeV”


 


Equation in line 1438 and line 1442    Consider the possibility to delete the pathway of ingestion for routine occupational intake, as in routine situation is not allowed to workers to ingest anything in the workplace.


 


Par. 3.4.2 , lines 2921 and following.  For the NCRP wound model, it is acknowledged that ICRP does not recommend any dosimetric models or dose coefficients for retrospective dose calculation, and the connection between the wound and systemic model is left to the reader. However, as the Cs behavior has been presented, displaying the differences between Weak and Particle categories (urine and faeces), it would be useful to have in the text a table with the default categories for the different elements, as reported in NCRP 156 publication, to consider the most probable wound category model to be added to the ICRP systemic model in a specific wound accident.


 


3540-3541 and  3543-3549     For retrospective dose assessment clarify the “iv” option. Specify that the female retention/excretion curves will not be provided as the reference methodology is to use, for the Reference Person, the biokinetics of the male. To my feeling the indication of  “(or female)”  biokinetic, in line 3540, is misleading as this would suggest the presence of female retention/excretion curves to evaluate a “female intake”. I suggest deleting the bracket.


 


Line 4051 and ff. number  (303)         It would be useful, for the sake of clarity, to introduce in the text some examples of the individual-specific parameters that cannot be changed after the definition of the effective dose (dose to a Reference Person not to that specific individual).


 


4090             I suggest to add the reference “IAEA Generic procedures for medical response during a nuclear or radiological emergency – IAEA report EPR-Medical 2005, IAEA, Vienna 2005” where the “RBE-weighted absorbed dose” for deterministic effects is introduced and described (e.g. for iodine in thyroid) and values for internal dose assessment for public are reported (Appendix XII).


 


4397             After the dot list, and for sake of clarity, I suggest to introduce the following equation,


Ik=[M(tk)-SUM(n=1 to k-1)(In* m(tk-taun)]/[m(tk-tauk)]


where In are the intakes already evaluated in the previous k-1 monitoring periods and Ik is the intake to be evaluated in the k-th monitoring interval. The other symbols have the same meaning as those reported in equation (6.7).


 


4446             I suggest to reformulate the sentence in (349) with the following : “In cases involving internal contamination dilution or chelating agents may be used to enhance clearance of the activity from the body, or blocking agents may saturate with stable elements the organ of choice with the aim to reduce committed doses”.


 


4513             I suggest to change “minimum detectable activities” with “detection limits”.


 


Par 6.5.1       I suggest to take care of the ISO document 11929:2010 and the ISO 28218:2010 where application of the Bayesian statistics for the determination of the characteristics limits decision threshold and detection limit are applied, and where the estimation of the best estimate of the measurand with the associated standard uncertainty interval are reported (especially for bioassay measurements in ISO 28218). References are:


- ISO 2010 : Determination of the characteristic limits (decision threshold, detection limit and limits of the confidence interval) for measurements of ionizing radiation —Fundamentals and application ISO 11929:2010 International Organization for Standardization, Geneva, Switzerland


- ISO 2010 : Radiation protection — Performance criteria for radiobioassay ISO 28218:2010 International Organization for Standardization, Geneva, Switzerland


 


(370) and line 4663     Make a reference related to the multimodal nature of the particle size distribution of radioactive aerosols in working environments. 


 


4720             It is not clear the meaning of the “(P)”. Please specify.


 


4978-4980    Specify that those values are related to the Reference Person, should be used in the reference retrospective dose assessment, also for female workers, and are based on sex average committed equivalent doses for organs of both male and female phantoms, as in Equation 1 of par. 3.7 line 3373.


 


4989-4992    Specify that those values are related to Reference Person, based on male biokinetics.


 


4993             I suggest to add and to indicate, near the equilibrium value, also the time at which the equilibrium value is achieved. I suppose that the unit rate of intake (e.g. 1 Bq/d) for the continuous chronic intake is here assumed. Please specify.


 


5012             Where and how to apply the committed equivalent dose coefficients for organs and tissue different between male and female, as the intake for the Reference Person should be calculated on the basis of the male biokinetics? For a female organ dose I have to multiply an intake calculated on the basis of the male biokinetics by a committed equivalent organ dose coefficient calculated for a female? Please specify .


 


5045-5051    Specify that the dose per unit content refers to the Reference Person and is based on the male biokinetics and the dose coefficient based on the weighted sum of sex-averaged committed equivalent doses to organs of both male and female phantoms. This must be in coherence with the “iv” reference retrospective procedure for dose assessment indicated in paragraph 3.7.3 . 


 


5056             Regarding the value of dose per unit content for the “entry through wounds” I would not expect some tabulated values after the statements presented in (207) – lines 2985-2991. Please specify if some dose coefficients, retention or excretion curves,(also in terms of z(t) values) for the wound pathway will be provided in the accompanying CD-ROM.  Surely it would be good to have some z(t) values for dose per daily excretion following different default NCRP 156 category behavior for selected radionuclides. 


 


5083-5087    Specify that the bioassay data for inhalation of aerosols of different median sizes refer to the Reference Person and are derived from male biokinetics. Specify for ingestion, if the bioassay data refer to different fA values for the same element (e.g. for U) and refer to the Reference Person, being derived from male biokinetics.


 


5088             Regarding the quantity “measured activity content per unit dose” to my feeling seems that it can be considered as the activity, at various times after an intake which eventually will deliver a committed effective dose of 1 mSv, that will be present in selected body organs or in the daily excretion. If a 1 mSv effective dose is used , as the definition “0.001/z(t)” gives ground for presuming, the dimension of the quantity should be (Bq) and not (Bq Sv-1) as 10-3 Sv/(Sv/Bq) gives (Bq).


It is worth mentioning that those values refer to the unit (1 mSv) effective dose and should be stressed that those values will be used for a perspective, and not retrospective, dose assessment.