IEC 61562 pdf download.Radiation protection instrumentation – Portable equipment for measuring specific activity of beta-emitting radionuclides in foodstuffs
1 Scope and object
This International Standard applies to portable instruments used for measuring the specific activity of beta-emitting radionuclides in food/foodstuffs and intended for operation under field conditions. This does not apply to low background laboratory instrumentation requiring highly skilled personnel. The instruments designed for measurement of beta contamination in foodstuffs under field conditions should not require special sample preparation other than machining (cutting, grinding, etc.). These instruments may be used in principle to measure beta emitting surface contamination and other radiation measurements as well, but these applications lie outside the scope of this standard. The same instruments intended for measuring foodstuffs can also be used for the measurement of environmental samples, such as soil, sewage, plant and animal life, etc. These instruments can be used to determine specific beta activity for a wide variety of samples under this standard. The purpose of this standard is to specify the main performance characteristics of instruments intended for measurement of specific activity of beta-emitting radionuclides in foodstuffs, their methods of testing and documentation requirements.
3 Terminology and units
For the purposes of this standard, the general terminology for detection and measurement of ionizing radiation and nuclear instrumentation given in IEC 60050(393) and IEC 60050(394) and the following definitions apply: 3.1 radiation meter instrument intended to measure quantities related to ionizing radiation [IEV 394-02-01] 3.2 specific activity, Bq/kg radioactivity per unit mass [IEV 393-04-13, modified] 3.3 volume activity, Bq/m 3 radioactivity per unit volume [IEV 393-04-14, modified] 3.4 detector efficiency ratio of the number of detected particles to the number of particles of the same type which are incident on the detector in the same time interval [IEV 394-18-21] 3.5 response time (of a measuring assembly) time required after a step variation in the measured quantity for the output signal variation to reach for the first time a given percentage, usually 90 %, of its final value [IEV 394-19-09, modified] 3.6 surface emission rate (of a source) number of particles of a given type above a given energy emerging from the face of the source or its window per unit time [IEV 393-04-92] 3.7 concomitant ionizing radiation ionizing radiation that accompanies the measured radiation but is not an object of measurement and whose influence on the results should be reduced as much as possible For beta-radiation meters operating under field conditions, gamma-radiation is a concomitant radiation. [IEV 393-02-22, modified] 3.8 sensitivity (of a measuring assembly) for a given value of the measured quantity, ratio of the variation of the observed variable to the corresponding variation of the measured quantity [IEV 394-19-07]
4.1 General The following radiation meter types are used for specific activity measurements under field conditions. a) Radiation meters allowing measurements in approximately 2 π geometry Radiation meters with a plane window detector refer to this type. They permit measurement of surface contamination as well. Foodstuff samples for such radiation meters used under field conditions are made planar with a thickness of more than a half absorption thickness for beta-radiation with maximum measured energy, to eliminate the influence of the source thickness on the measurement results. The layer thickness of most consumable foodstuffs is 1 cm to 3 cm.b) Radiation meters for liquid and loose solid samples allowing measurement in approximately 4 π geometry, containing a detector with wrapping surface Liquid sources are poured into a detector cell and may be in close contact with the detector. Loose solid samples may have protective cover packages, cuvettes, etc. Measuring geometry and sample volume in this type of detector are fixed. 4.2 General description of instrument Radiation meters for specific beta-activity measurements in foodstuffs can comprise the following main parts: – detection sub-assembly; – measuring sub-assembly. These parts may be either integrated or realised as separate units. Radiation meters should be provided with a terminal for an external precision pulse generator connection which can be used for instrument adjustment, calibration and test. 4.3 Detection sub-assembly Detection sub-assemblies may be interchangeable. Through the detection sub-assembly connection, the device shall automatically set the appropriate operating mode. Construction of the instrument shall be such that an incorrect detection unit connection is impossible. Detection cell construction should allow quick and simple substitution of one measured sample by another.