IEC 61563:2001 pdf download

IEC 61563:2001 pdf download.Radiation protection instrumentation –
Equipment for measuring specific activity of gamma-emitting radionuclides in foodstuffs.
• detection sub-assembly,
• measuring sub-assembly.
These parts may be integrated or function as separate units.
Radiation meters should be provided with facilities for the connection of a precision pulse generator which can be used for instrument adjustment, calibration and test,
4.3 Detection sub-assembly
Detection sub-assemblies may be interchangeable. Where this is so, the appropriate operating mode shall be set by the connection between the detection sub-assembly and measurement sub-assembly.
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.
4.4 Measurement sub-assembly
The measurement sub-assembly in general should provide the following radiation meter functions:
• to convert the measured value information coming from the detection sub-assembly and display it in appropriate units:
• to integrate the background value over time, in order to increase the accuracy of the background measurement:
• to take into account the radiation meter background value automatically:
• to determine the number of counts automatically and display its value;
• to consider the energy range of gamma-rays detected and to convert the indicated counts to specific or volume activities of radionuclides:
• to set the appropriate operating mode automatically at the connection of the specific detection sub-assembly;
• to maintain the power supply condition during monitoring and in case of its breakdown, to switch ofl the display of the radiation meter;
• to accept in digital form coefficients or parameters used for information processing (calibration factors, energy range, alarm thresholds, etc.);
• to activate sound and I or light alarm when the specific activity level exceeds the pre-set thresholds.
The device shall be provided with visual signalling of radiation meter overload and low battery
indicator.
4.5 Complementary equipment
The following complementary equipment may in general be part of the radiation meter system:
• removable cups or insertion pieces for holding and positioning foodstuff samples in sufficient quantities:
Reference volume sources with artificially loaded radioactivity may be produced on the basis of natural foodstuffs and various substitutes, including polymeric compounds. Such sources are equivalent to the monitored media in radionuclide composition and in total mass attenuation coefficient. The sources should be shaped to fit into the detector cavity of the particular radIation meter.
The conventionally true activity value of reference sources shall be determined with a total uncertainty of less than 20 %. Relative source activities used in the same series of measurements should be known with an uncertainty of less than 10 %. If necessary, half-life corrections should be made for these reference sources.
6.6 Checking sources
The checking sources are used for the radiatIon meter operability check, as well as for carrying out the tests for stability and the influence of ambient factos. Solid sealed gamma- sources of appropriate size may be used for these purposes. The radiation meter should be provided to hold the source at a fixed position relative to the detector.
The checking source reading shall be taken after each calibration. This reading is later used when checkin9 the operability of the instrument.
7 RadIation characteristics
7.1 Relative intrinsic error
7.1.1 R.qulr.m.nts
Under standard test conditions the relative intrinsic error of the radiation meter readings shall not exceed 50 % over the whole effective measurement range for any of the nuclides mentioned in 5.1.
7.1.2 Tests
The type and routine tests can be carried out with real natural foodstuff samples whose specific activities have been measured with calibrated laboratory instrumentation.
The type tests shall be performed with at least one instrument from the series and routine tests with each manufactured instrument. If checking sources are to be used for the routine tests, the sensitivity dependence to checking sources in relation to the sensitivity to reference sources of specific activity should be predetermined when conducting type tests.
Tests can be carried out using reference sources together with a pulse generator calibrated with respect to the specific activity of reference sources. The relative intrinsic error should be determined at least at two points of the measurement range with reference sources.
For both types of tests a set of sources is needed.
a) Type tests
Tests shall be carried out at one point of each decade: at the level of 25 % of the least significant decade, 75 % of the most significant one and 50 % of the others.