IEC 61562:2001 pdf download
IEC 61562:2001 pdf download.Radiation protection instrumentation- Portable equipment for measuring specific activity of beta-emitting radionuclides in foodstuffs.
b) Radiation meters for liquid and loose solid samples allowing measurement in approximately
4 it 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.
4.4 Measurement sub-assembly
The measurement sub-assembly should in general 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 automatically take into account the radiation meter background value:
– to automatically determine the number of counts and display their value;
— to automatically set the appropriate operating mode at the connection of the specific detection subassembly;
— to maintain the power supply condition during monitoring and in case of its breakdown, to switch of f 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/or light alarms when the specific activity level exceeds the preset thresholds.
The device should be provided with visual signalling of radiation meter overload and a 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 quantilies:
— simulators of samples under test for radiation meter background determination;
— tunnels, measuring cups for pouring liquid samples into the detector cell:
— scissors. graters, mills, for grinding or adjusting samples shapes:
— other materials and tools necessary for sample preparation:
— equipments necessary for decontamination:
— checking sources, and special holders for these checking sources to hold the sources at fixed positions with respect to the detector.
4.6 DecontamInation
The instrument design, especially with regard to the detection unit, should be implemented in
such a way that the probability of radioactive contamination is minimized
The materials used for constructing the instrument should possess minimum absorption of contaminalion and allow decontamination by routine means.
5 Main characteristics
5.1 Measured nuclldes
The radiation meter shall, as a minimum, measure the specific activities of these radionuclides:
5.2 Measurement range
The measurement range of the radiation meter for the above radionuclides should have a maximum lower bound of 1 x 102 Bqikg and a minimum upper bound of 1 x 106 Bqfkg, the external gamma dose rate not exceeding 2,5 pGy,h.
NOTE Th. operation manual tot th. radiation meter should specify the time required to pertorm the meaSurmsnts at the lower limit of detection. This value should not include the time for sample preparation and of that for determination of background
5.3 Energy measurement range
The energy measurement range of the instrument shall provide I or the measurement of the nuclides mentioned In 5.1. This range shall be at least from 150 keV to 2300 keV.
5.4 Instrument background
Radiation meter background originates from internal and external sources.
The internal sources consist of electronic noise and radioactivity of contaminated materials of Instrument construction, primarily In the defector sub-assembly. The external sources are naturally occurring radioactive materials and cosmic radiation. Instrument background may depend heavily on the selected energy range of measurement.
