BS/EN 62694-2016 pdf download.Radiation protection instrumentation Backpack-type radiation detector (BRD) for the detection of illicit trafficking of radioactive material.
The gamma-ray background intensity shalt be measured using a pressurized ion chamber or similar environmental radiation measurement device that is calibrated to provide the gamma- ray ambient dose equivalent rate, I(1O). When testing spectrometric BROs the gamma-ray background shall be characterized using a high resolution gamma-ray spectrometer (e.g., high purity germanium (HPGe) detector). The measured spectra shall be recorded, If the BRD is equipped with neutron detectors, the neutron background should be the natural background and should not be artificially modified during testing. The neutron background at the test location shall be measured and recorded.
The evaluation of the BRD shall be performed without the benefit of any radiation shielding against the natural background, except for that shielding that is part of the instrument.
4.8 BRD set up
The BRD shall be set up based on the manufacturer’s specifications including background update mode, if applicable. Once set up for testing, no changes shall be made that could affect the overall response of the BRD. If more than one background update mode is available, testing should be performed in all modes when indicated in the specific clauses under the radiological tests.
When performing the radiological tests in Clause 6, the BRD shall be configured and oriented as it would be used. This may be achieved by using a phantom that would represent the human upper torso. The phantom shall be made of polymethyl methacrylate (PMMA).The phantom dimensions shall be 40 cm wide. 60 cm high and 15 cm thick.
The BRO shall be mounted on a stand or fixture made Out of a material that does not have a large hydrogen content (e.g., foam, plastic). It is recommended to use materials such as aluminium for mounting the BRD to prevent possible additional moderation of the neutron source.
The reference point of the BRD should be marked by the manufacturer. If marking is not provided by the manufacturer, the reference point is defined as the imaginary point where the three mutually orthogonal lines that go through the center of the length. width and thickness of the BRD intersect (see Figure 2).
For static and dynamic tests described in Clause 6, the reference point of the BRD shall be positioned 1,5 m from the floor or ground surface. The centreline of the source shall be at the same height as the reference point of the BRD, 1 .5 m from the floor or ground surface.
For static tests, the distance between the source and the centreline of the BRD shall be between 1 m and 3 m unless otherwise stated.
4.9 Speed of moving sources and integration time for radlonuclide identification
For static tests, the integration time required to perform a radionuclide identification shall be
as specified by the manufacturer or a maximum of 1 mm (whichever is the shortest).
During the static tests, the source shall be removed and placed back in the same location between trials. There shall be a 10 s minimum delay between each trial with the source either positioned at a distance where it does not affect the background surrounding the BRD or shielded during the delay.
For dynamic tests, the source or BRD shall be moved In a configuration that provides no shielding around the source other than that required for the specific test. The source speed shall be 1,2 ms-1 (average walking speed) when tested at a distance of closest approach of 1,5 m, unless otherwise required in a test. If the distance of closest approach, d (expressed in m). is adjusted within 1 m and 3 m then the passage speed, v (expressed In ms—1). shall be adjusted to v = v0 x did0,
where v0 = 1,2 ms1 and d0 = 1,5 m.
During the dynamic tests, there shall be a 10 s minimum delay between each trial with the source either positioned at a distance where it does not affect the background surrounding the BRD or shielded during the delay.
NOTE For all dynamic tests, the source or the BRD can be moved relative to each other.
4.10 RadIation sources
Unless otherwise stated, tests involving the use of gamma radiation shall be carried out using 137Cs for gross count measurements and 241Am together with 60Co for radionuclide identification (see Table 1),
The reference source for neutron radiation is 252Cf. The neutron emission rate of the 252Cf source shall be 20000 s1 (± 20 %) (see Table 1). The unmoderated reference neutron source shall be encapsulated in 1 cm of steel and shielded with 0.5 cm-thick lead in order to attenuate the possible gamma-ray emission from the 252Cf source. The lead shall be placed outside the steel encapsulation. The moderation of the 252Cf is achieved by surrounding the source in the presence of the 1 cm of steel encapsulation and 0,5 cm-thick lead shielding with 4 cm-thick high density polyethylene (I-IDPE) container (e.g., sphere, cylinder, box).
The sources shall be mounted on a stand or fixture made out of a material that does not have a large hydrogen content (e.g., foam, plastic).BS/EN 62694-2016 pdf download.