Occupational Intakes of Radionuclides Part 1 - ICRP
Occupational Intakes of Radionuclides Part 1 - ICRP
Occupational Intakes of Radionuclides Part 1 - ICRP
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DRAFT REPORT FOR CONSULTATION<br />
be different and 241 Am lung results may underestimate Pu activity in the lung (e.g.<br />
nitrate aerosols).<br />
6.4 Measurements<br />
6.4.1 Data Collection and Processing<br />
(335) Some types <strong>of</strong> measurement data may need processing before use. Examples<br />
include:<br />
Lung. Generally, the combined activity in lungs and thoracic lymph nodes is<br />
referred to as ‘lung’ activity, and it is this quantity that is calculated by internal<br />
dosimetry s<strong>of</strong>tware. Where estimates <strong>of</strong> lung and lymph activity are given<br />
separately, they should be summed. ‘Chest’ measurements may also include<br />
counts from activity in liver and skeleton for radionuclides that concentrate in<br />
these tissues and their contributions will be needed to be subtracted.<br />
Urine and faecal samples collected over periods less than 24 hours should in<br />
general be normalized to an equivalent 24 hour value. This can be achieved by<br />
multiplying by the ratio <strong>of</strong> the reference 24 hour excretion volume or mass to<br />
the volume or mass <strong>of</strong> the sample. The reference volumes, for males and<br />
females respectively, are: for urine 1.6 litres and 1.2 litres; and for faeces 150 g<br />
and 120 g (<strong>ICRP</strong>, 2002a). For urine sampling, another widely used method is<br />
to normalise to the amount <strong>of</strong> creatinine excreted per day; 1.7 g and 1.0 g for<br />
males and females respectively (<strong>ICRP</strong>, 2002a). If the 24 hour sample is less<br />
than 500 ml for urine or less than 60 g for faeces, then it is doubtful that it has<br />
been collected over a full 24 hour period and normalization should be<br />
considered. Collection <strong>of</strong> faecal samples should preferentially cover a period<br />
<strong>of</strong> about three days, as the transit time through the alimentary tract is subject to<br />
large inter (and intra-) subject variations.<br />
(336) For some radionuclides the collection <strong>of</strong> spot samples are sufficient for<br />
routine sampling, e.g. the monitoring <strong>of</strong> intakes <strong>of</strong> tritiated water.<br />
6.4.2 Single Measurements, Acute <strong>Intakes</strong><br />
Special monitoring<br />
(337) For special or task-related monitoring when the time <strong>of</strong> intake is known, the<br />
intake can be estimated from the measured results using the m(t) values given in<br />
subsequent reports <strong>of</strong> this series. An m(t) value is a value <strong>of</strong> a bioassay quantity<br />
measured at time t after a unit intake <strong>of</strong> a specified radionuclide, sometimes known as<br />
a retention or excretion function. If only a single measurement is made, the intake, I,<br />
can be determined from the measured quantity, M, if the contribution <strong>of</strong> previous<br />
intakes to the measured quantity M is negligible.<br />
I <br />
M<br />
mt<br />
121<br />
(6.1)<br />
(338) The intake should be multiplied by the dose coefficient (eij, for pathway i and<br />
radionuclide j) to obtain the committed effective dose E:<br />
E(50) = eij × I (6.2)
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