Contamination monitor tests

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Date: 23 May 2012

Time: 17:00

Contamination monitor tests

The range of tests offered is outlined below. Some tests may not be applicable to all types of contamination monitors.

Light leakage test: Scintillation based detectors are exposed to a source of bright light to confirm they are light sealed and ambient light conditions have no effect on the instrument readings
Scale linearity: Checks are carried out to confirm the instrument performs satisfactorily over its entire scale
Detector uniformity: For large area detectors (i.e. detector area >40 cm²), the uniformity of the detection area is confirmed with a very small area source (usually ¹⁴C)
Response to contamination: A range of large area reference sources are available. Each instrument is calibrated against those appropriate for each instruments type. The calibration sources are all constructed in accordance with ISO8769 and comply with the required uncertainties for a class one calibration source. They are constructed to provide a known surface emission rate for each radiation type (e.g. alpha, beta or photon) and energy. They are not designed in any way to replicate what the user might encounter in practice. Their purpose is to provide calibration services with a reliable, well constructed, long lived source with accurately known surface emission rates so that comparisons with manufacturer's type test data may be made. The price of the calibration remains the same for a detector type and is independent of how many sources are used to calibrate a monitor

Range of ISO8769 large area reference sources available at RRPPS

The examples listed are not exhaustive but give an indication of some of the most common radionuclides/monitors encountered at the RRPPS Calibration Service.

Reference source (ISO 8769)	Radiation/energy	Suitable for users using radionuclides	Example monitor
²⁴¹Am	Alpha 5.5 MeV	Alpha emitters	NE AP range of probes Berthold a/b detector
¹⁴C	Beta 156 keV (max.)	Low energy beta emitters: ¹⁴C, ³⁵S, ¹⁴⁷Pm, ³³P	Berthold a/b detector Mini EP15 NE BP range of probes
³⁶Cl	Beta 710 keV (max.)	Medium energy beta emitters: ¹³1I, ¹⁹²I, ²⁰⁴Tl	As above
⁹⁰Sr/Y	Beta 2.27 MeV (max.)	High energy beta emitters: ⁶⁰Co, ³²P, ²³⁸U	As above
⁵⁵Fe	Photon/gamma 5.9 keV (mean)	Very low energy photon emitters: ⁹⁹mTc, X-ray emissions from some display screens	Mini 900 44B Berthold b/g detector NE sodium iodine probes
¹²⁹I with Al filter	Photon/gamma 32 keV (mean)	Low-medium energy photon emitters: ¹²⁵I, ¹²³I, ¹⁰⁹Cd	Mini 44A/B Berthold b/g detector NE sodium iodine probes
⁵⁷Co with stainless steel filter	Photon/gamma 124 keV (mean)	Medium energy photon emitters: ⁵⁷Co, ⁹⁹mTc	As above

Geometry of calibration

The response is normally measured at a source - detector distance of 3mm. When assessing contamination in practice, this distance may not be achievable. Corrections will need to be made to account for this and other factors that are explained in the National Physical Laboratory (NPL) Good Practice Guide GPG30, "Practical Radiation Monitoring".

Links

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Practical Radiation Monitoring (National Physical Laboratory)Practical Radiation Monitoring

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