Occupational Intakes of Radionuclides Part 1 - ICRP

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DRAFT REPORT FOR CONSULTATION
(339) Care must be taken to ensure that the measurement result, M, and m(t) are
comparable; for example, in the case of urinalysis, the bioassay result must be
expressed as the total activity in a 24 hour urine sample at the end of collection (not at
analysis). Alternatively, the tabulated values of ‘Dose per unit content’ for a range of
radionuclides and types of materials should be used. Dose per unit content, z(t), is
given by:
z(t) = e(50) / m(t) (6.3)
(340) If only a single measurement is made, and the contribution of previous intakes
to the measured quantity M is negligible, the committed effective dose E(50),
associated with the intake, I, can be determined by:
E( 50)
M z(
t)
(6.4)
Routine monitoring
(341) For routine monitoring, an intake during the monitoring period is assessed
from the measurement made at the end of the monitoring interval. When the time of
intake is not known (or cannot easily be determined) and a reference evaluation is
being performed (Section 6.2.1), it should be assumed that the intake occurred at the
mid-point of the monitoring interval of T days. For a given measured quantity, M,
obtained at the end of the monitoring interval, the intake is:
M
I
m
T / 2
122
(6.5)
where m(T/2) is the predicted value of the measured quantity for a unit intake
assumed to have occurred at the mid-point of the monitoring interval. The dose
from the intake in the monitoring interval is obtained by multiplying the intake by
the dose coefficient. The assessed dose or intake can be compared with the pro-rata
fraction of the dose limit or of the intake corresponding to that limit, respectively.
Alternatively, the dose or intake can be compared with predetermined investigation
levels.
(342) An intake in a preceding monitoring interval may influence the measurement
result obtained. For a series of measurements in a routine monitoring programme, the
following procedure may be followed:
Determine the magnitude of the intake in the first monitoring interval.
Predict the contribution to each of the subsequent measurements from this
intake.
Subtract the corresponding contributions from all subsequent data if the
contributions are judged to be significant (ISO, 2011)
Repeat above for the next monitoring interval.
(343) Alternatively, using the tables of dose per unit content, for a given measured
quantity M, obtained at the end of the monitoring interval, the mid-point dose E
associated with intake I is:
E M z(T
/ 2)
(6.6)