Occupational Intakes of Radionuclides Part 1 - ICRP

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DRAFT REPORT FOR CONSULTATION
position where the dosemeter is worn, and E(50) is the committed effective
dose from internal exposure as assessed by:
E ( 50)
e j, inh ( 50)
I j, inh
ej,
ing(
50)
j
j
where ej(50) is the dose coefficient (committed effective dose per unit intake,
Sv Bq -1 ) of a radionuclide, integrated over 50 years after intake by inhalation
(inh) and/or ingestion (ing). The intakes, Ij (Bq), may be for one or a number of
radionuclides.
(60) The dose coefficient for intakes of radionuclides is the fundamental quantity
recommended by ICRP for protection purposes. The Annual Limit on Intake (ALI)
and the Derived Air Concentration (DAC) are derived parameters that can be useful in
the control of exposures.
(61) The ALI was defined in Publication 60 (ICRP, 1991, paragraph S30) as an
intake (in Bq) of a radionuclide in a year which would lead to a committed effective
dose of 20 mSv (0.02 Sv). The average annual limit on intake for workers would thus
be:
ALI
j
0.
02
e ( 50)
j
(62) The DAC is the activity concentration in air (in Bq m -3 ) of the radionuclide
considered which would lead to an intake of an ALI assuming a sex-averaged
breathing rate of 1.1 m 3 h -1 and an annual working time of 2000 h. Then the DAC is
given by:
ALI j
DAC j
2200
(63) ICRP does not now give ALI values because it considers that for compliance
with dose limits it is the total dose from external radiation as well as from intakes of
radionuclides that must be taken into account, as indicated above. It is, however,
noted that the ALI concept can be useful in various practical situations, characterising
the relative hazard of radiation sources to ensure that appropriate administrative
controls are in place. ALI values can be easily calculated using the equations given in
the previous paragraphs.
41
I
j, ing
2.3 Objectives of Monitoring
(64) The purpose of monitoring for internal exposure to radionuclides is to verify
and document that the worker is protected adequately against radiological risks, and
that the protection afforded complies with legal requirements. Two types of
monitoring of internal exposures of workers can be identified: workplace monitoring
and individual monitoring.