Introduction
VF1807090083 EN revision 11
1.3. Terms and definitions
A quotient of the mean number of spontaneous nuclear transitions from an energy state
in an amount of radionuclide in a time interval. The unit is [Bq].
Value (threshold) that is preset inside the instrument. If this value is exceeded, the alarm
will be activated. Both the acoustic and visual alarms can be activated. The units are
usually [cps, Bq, (Bq∙cm
-2
), Gy/h, Sv/h].
Radiation field in which the instrument should operate, and which involves both the
natural background and the radiation caused by other sources that can be present in the
vicinity of the instrument. The following units, depending on the instrument type, are
usually used [cps, Bq, (Bq∙cm
-2
), Gy/h, Sv/h].
Certified Reference
Material (CRM)
Material provided with a certificate whose one or more properties are sufficiently
homogeneous and determined at a sufficient level for calibrating an appropriate
instrument. These properties are certified by a procedure that determines traceability on
the precise implementation of the unit in which the value of properties are described, and
each certificated value is accompanied by an uncertainty at a given confidence level.
Coefficient of the error
of the first kind (Type I
error)
Determines the probability that the true activity of the sample measured is zero, and
the instrument indicates contamination.
Coefficient of the error
of the second kind
(Type II error)
Determines the probability that the true activity of the sample measured is greater than
zero, and the instrument indicates no contamination (clean).
Instrument intended for the measurement and evaluation of surface contamination that
contains visual indication and acoustic signalization of count rate. The acoustic
signalization can be switched off.
Instrument intended for the measurement and evaluation of surface contamination,
and additionally to the visual indication and acoustic signalization of the count rate,
the instrument is provided with acoustic signalization of exceeding the preset
contamination level (threshold).
Count per second;
Count rate
Number of counts per time unit. The units are usually [cps, cpm].
Critical value of the statistical test for making a decision if the measured count rate of
a potentially contaminated person is at the background level, or the measured count rate
is higher than the background. The unit is [cps].
The mean count rate for which the probability that the net count rate measured is lower
than the decision level is just equal to beta. The beta parameter means the coefficient
of a type II error. The unit is [cps].
Direct measurement of
surface contamination
Surface activity measurement by means of a contamination meter/monitor.
Effective measurement
range
Range of the quantity measured in which operating values of the meter or the monitor
meet the requirements of valid standards for the given type of instrument.
Ratio of the corrected count rate of the measuring instrument to the surface emission.
The unit is usually [%].
Indirect evaluation of
surface contamination
Assessment of removable contamination by means of wipe (smear, swab) test samples.
The electric component that is able to detect very low intensity light signals. When a
photon impacts on the sensitive photocathode, electrons are emitted due to the
photoelectric effect, which are gradually magnified by electric voltage among the individual
electrodes (i.e. dynodes). The accelerated electrons that impact on the dynodes emit a
high number of electrons (the secondary emission), which results in the magnified electron
flux that impacts on the anode. PMTs are mainly used in scintillation detectors.
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