BS IEC 61577-3:2011 pdf – Radiation protection instrumentation -Radonand radon decay productmeasuring instruments Part 3: Specific requirements for radondecay product measuring instruments.
In the case where an air filter is applied for aerosol retention and sampling of airborne radionuclides, a high-efficiency particle filter (HEPA) should be applied. The manufacturer shall state the type of the filter.
Access to the filter shall be designed so as to permit fast and easy remova[ Attention shall be given to the air seal around the filter so as to minimize leakage between the filter and the filter holder, Warning shall be given that the pressure drop is such that a filter change is necessary. The design shall enable the filter to be changed easily without damage.
The air pump shall be placed downstream from a filter or any other sampling unit, and shall be able to withstand the variations of pressure induced by operation conditions, filter types, and atmospheric dust-mass blockage. The pump shall be capable of continuous operation between scheduled maintenance operations
The range of acceptable flow-rates shall be stated by the manufacturer. If the measurements are influenced by flow-rate, a flow-rate control device shall be provided that has a flow-rate adiustment range sufficient to allow for variation in the intrinsic characterIstics of the air pump and any filters used. If the flow-rate is to be measured and indicated, the pressure and the temperature at which the flow-rate meter is calibrated and at which the flow-rate is expressed shall be provided.
5.2 RadIation detection assembly
The radiation detection assembly produces an electrical signal related to the radiation emitted by the sampled radon decay products incident on the detector, The efficiency of detection shall be optimized.
Contamination of the detector may increase the background. Precautions shall be taken for the protection against contamination, when the instrument is not in use. Wherever possible, the radiation-detector window should be protected by a removable thin screen, or a rugged solid-state detector should be used.
NOTE The contamination can be caused by:
– deposition of airborne decay productS.
— recoil ot sampled decay products
5.3 Data processing and recording
This assembly comprises functional units for acquiring and processing signals supplied by the detector,
The manufacturer shall publish the relevant measurement principles and procedures used to produce the measurement result and its uncertainhies The detail of information shall facilitate the verification of measurement results by the purchaser.
The electronic data recording system shall have the capacity sufficient for recording all measurement data, including the spectrometry data generated during a long autonomous data-acquisition period. The data shall be retained on a media that ensures the protection and availability of the data, especially In the event of malfunction and interruption of operation or failure of power supply. The manufacturer shall specify the capacity of the data recording system.
5.4 Measurement display
The display shall be easily readable in different ambient condit.ons The measurement units shall be clearly marked on the display. If needed by the measurement method, the indication of the flow-rate, the atmospheric air pressure and the ambient temperature shall be provided.
The display shall show one or more of the following quantities
the activity concentration of radon decay products;- the potential alpha energy concentration or exposure;-the equilibrium equivalent radon concentration.
The quantities shall be given in combined Sl-units.Appropriate submultiples should be used.The display should show the uncertainty of the measurement.
The result of a measurement shall contain both the measured value of the measurand and theuncertainty associated with that measured value.The uncertainty given should be based onthe requirements of the ISO/IEC Guide 98-3 to the expression of uncertainty in measurement.
Data outputs should be provided permitting remote indications and the use of one or more ofthe following devices:
– display;
– data recorder;printer;
– computer;
– or other devices via data port.