IEC 60761-5:2002 pdf download

IEC 60761-5:2002 pdf download.Equipment for continuous monitoringof radioactivity in gaseous effluents -Part 5: Specific requirements for tritium monitors.
3 Terms and definitions
For the purpose of this part of IEC 60761, the following definitions apply:
3.1
tritium effluent monitor
equipment designed for the continuous monitoring of tritium in gaseous effluents discharged to the environment
3.2
tritium
unless otherwise stated, tritium”, in this standard, covers tritium in gaseous or vapour forms, whether chemically combined or not
4 Classification of tritium effluent monitors
The equipment may be classified according to the type of measurement as:
— selective monitors, for the selective measurement of one particular form of tritium (gas, tritium oxide or any tritiated compound);
— non-selective monitors, for the overall measurement of tritium in all its forms.
5 Sampling and detection assembly
5.1 Sampling and exhaust pipes
In addition to the general requirements of IEC 60761-1, the following characteristics shall be considered and shall be agreed between manufacturer and purchaser:
— the nature of the materials used, paying particular attention to chemical corrosion, electrostatic effects, memory effects, etc.
— the minimum distance between inlet and outlet to avoid recirculation;
— the prevention of condensation in the pipe by variation of temperature or pressure;
— the ease of decontamination.
5.2 Inlet filter
A filter shall be placed in a filter-holder at the sampling circuit inlet to remove any dust and aerosols from the air. In order to maintain the specified performance of the equipment, such a filter shall not trap, or even temporarily, retain tritium.
All necessary arrangements shall be made to control the pressure drop in the filter. The system should be designed to allow filter change at a given pressure drop to ensure that an intact filter is in place.
5.3 Ease of decontamination
In order to avoid interference with measurements, it is recommended that all necessary arrangements be made to limit the contamination of the detector. In all cases, the detection assembly shall be easy to dismantle, decontaminate and reassemble.
5.4 Collection medium
If the detection assembly includes an absorbent medium, intended to collect a specific chemical form of tritium, its characteristics, efficiency, retention capacity and delay time constant shall be known for the various radioactive gases of significance in the effluent.
The manufacturer shall state how the collection efficiency is influenced by the chemical form of tritium, atmospheric conditions and the presence of chemical products and other gases in sampled air. The manufacturer shall specify the storage conditions of the absorbent medium.
5.5 Check source
Any check source, when not in use, shall not increase the reading of the measurement assembly by more than 10 % of the maximum value of the lowest useful decade of measurement.
5.6 Mr pump
The requirement of clause 11 of IEC 60761-1 is applicable.
5.7 Radiation detector
The manufacturer shall specify the detector characteristics, including the aetector dimensions and sampling volume.
6 Expression of measurements
In accordance with the requirements of clause 9 of IEC 60761-1, the electronic assembly associated with the detector shall provide a reading expressed directly in terms of volumic activity (Bq/m3).
7 Tests performed under standard test conditions.
9 Reference sources
For the determination of the reference response during type tests, the reference source shall be air with a known volumic activity of the particular form of tritium for which the equipment is designed. The reference sources should consist of bottles of pressurized air or gas containing the form of tritium for which the equipment is designed or any other calibrated device generating the appropriate form of tritium.
Some suitable means of producing sources are described in annex A. The conventionally true activity of the gas sources shall be known with an uncertainty better than 7 % (k = 2).
10 Radiation performance tests
These tests are carried out under standard test conditions. If an electronic method of compensation against natural activity is included, all tests of the measuring assembly shall be performed with the compensation circuits in operation, after having been adjusted according to the manufacturer’s instructions.
10.1 Reference response
10.1.1 Requirements
The reference response shall not differ by more than 15 % from the manufacturer’s specifications.
10.1.2 Test method
Circulate air, labelled with a known volumic activity of tritium, through the assembly at a constant flow-rate, for a time sufficient to reach measurement equilibrium. Note the equilibrium reading. Some methods are given as examples in annex A.
10.2 Linearity
The requirements and test methods described in 26.3 of IEC 60761-1 are applicable.
10.3 Response to other chemical forms of tritium
10.3.1 Requirements
If the equipment is designed to measure the activity of a particular chemical form of tritlum, Its response to other chemical forms having an influence on the measurement shall be specified by the manufacturer, and shall be less than 15 % of the response to the form of tritium for which the equipment is designed.