IEC 61578:1997 ppdf download – Radiation protection instrumentation – Calibration and verification of the effectivenessof radon compensation for alpha and/or betaaerosol measuring instruments – Test methods.

IEC 61578 is applicable to type test methods which permit calibration and measurement of the effectiveness of radon daughters’ compensation of radioactive aerosol monitors. This standard defines aerosol characteristics used in these tests and applies the following procedures:

— test method permitting the measurement of the response of the monitor relative to alpha and.or beta defined radioactive aerosols:

— test method permitting the measurement of the response of the monitor relative to radon

daughter-defined aerosols:

— test method permitting the measurement of the effectiveness of radon compensation:

— test method permitting the measurement of the response of the monitor relative to a mixture of aerosols constituted by radon daughters and by alpha and/or beta radioactive emitters.

In addition, it specifies the requirements br acceptance.

1.2 Definitions

For the purpose of this International Standard, the following definitions apply.

1.2.1 Geometric standard deviation

Assuming a NORMAL probability density bunchion for the logarithm of the particulate diameters, the geometric standard deviation is equal to the quotient of either the median diameter to the diameter corresponding to 16 % of the cumulative size distribution, or the diameter corresponding to 84 % of the same size distribution to the median diameter. This means that 68 % of the aerosol parliculates have diameters within an interval equal to ±1 geometric standard deviation.

1.2.2 Equilibrium factor of a radon daughters aerosol

The equilibrium factor is equal to the quotient of the actual potential alpha energy of short-lived radon daughters to that which would exist it radon daughters were in equilibrium with radon. Where radon daughters are in equilibrium, the equilibrium factor is equal to 1. otherwIse It is lower than 1.

2 Characteristics

2.1 Radioactive artit,cial aerosols

In the nuclear fuel cycle, workers are exposed to radioactive aerosols. These aerosols are constituted of particulates of various sizes, generally between 0,1 pm and 10 pm 11j. In the case of an accident, this size range can also be observed in the environment 121. The penetration of radioactive particulates Into the respiratory system depends on their aerodynamic diameter, which corresponds to an equivalent diameter of parliculates considered as spherical and of unit density (1 g.cm3). The particulate aerodynamic diameters produced by an aerosol generator for calibration of radioactive artificial aerosol monitors shall then be chosen as a function of their different levels of penetration in the lung system. Depending on the retaining medium, sampling head and tubing used in those monitors, their response is also affected by the particulate sizes, the design of the equipment shall be such as to avoid, as much as possible, this effect.

Radioactive aerosols produced by generators may be characterized by the following parameters:

a) granulometry, i.e. the distribution of the particulate aerodynamic diameters, The activity median aerodynamic diameter (AMAD) and the geometric standard deviation may be used more conveniently to deline this parameter;

b) type of radioactivity i.e. the radiation emitted by the particulates. The generator may produce aerosols emitting alpha (239Pu) and beta-gamma (‘37Cs) as reference radiations;

C) volume activity. i.e. the activity of the aerosol per unit air volume:

d) concentration. i.e. either the number of airborne particulates per unit air volume (m), or the mass of airborne particulates per unit air volume (pg rn-3). In ventilated and filtrated nuclear facilities, the concentration is of the order of 30 whereas it can reach some hundreds of pg.m’3 in a dusty urban environment. As the response of these monitors (especially alpha monitors) for the same particulate size is affected by the mass collected on the retaining medium, the concentration shall be controlled and known with accuracy.

# IEC 61578:1997 ppdf download – Radiation protection instrumentation – Calibration and verification of the effectivenessof radon compensation for alpha and/or betaaerosol measuring instruments – Test methods

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