RADONIC 01 – continual radon monitor with a very fast response

MEASURING DIVOCE FOR MONITORING OF FAST VARIATIONS OF THE RADON CONCENTRATION IN THE AIR

Unique detection characteristic of the device

RADONIC 01 is a continuous radon monitor based on an ionization chamber detector operating in the current mode. The substantial characteristic feature of the detection principle is a very fast response. For these technical and principal reasons, the device provides very fast radon concentration measurements (the first information is displayed in five minutes).

Instrument applications

• Standard monitoring of long-term (several weeks) variations of radon concentration
• Monitoring and analysis of dynamic effects characterized by fast changes of radon
• Assessment of instantaneous values of radon concentration
• Radon transport and distribution monitoring (mapping of radon concentration) – useful for a building quality inspection

Detector properties and detection principle

Continuous radon monitor RADONIC 01 is based on a cylindrical ionization chamber of the inner volume of  8,4 l. A chamber case is an aluminium pressed piece with sheet metal thickness of 1 mm. The lower case of the detector is closed by a demountable cover with an input ventilation unit and an electrostatic filter. The axial collecting electrode is fastened in the upper part of the chamber. The collecting electrode passes through a teflon insulator impressed in a metal tube, operating as a protective electrode. The described set is fastened in an insulating bushing, placed in a center of the upper part of the detector. A direct operating voltage of the detector is 150 V. The output ventilator, providing an intensive ventilation of a susceptible volume of the detector, is located in the upper part of the device. The electrostatic filter consists of two insulating metal grids. The input grid with operating direct voltage 1000 V is protected by a fine glass fiber filter providing a radon decay products suppression. The second grid is grounded. The radon monitor RADONIC01 operates in an active mode, the external air is sucked by the input ventilator and then passes through the set of filters into the detection volume of the device. The filtration unit provides a dust suppression and an effective radon progeny capture. The external air is used as an operating detection gas inside the ionization chamber. The detector operates in a non-saturated mode of a volt-ampere characteristic. The operating voltage between electrodes of the chamber is 150 V. The electric current sensitivity of the detector using the working voltage 150 V is 85% of the saturated state sensitivity. The ionization current is amplified and then electronically and statistically processed. Processed results are subsequently displayed and stored in the memory. Basic measuring functions are set-up from the control panel. The measuring device communicates with PC by a standard serial communication interface RS232, used for data transfer and for entering the calibration constant and other operating instructions. RADONIC 01 is also equipped by an internal temperature sensor, and it can be optionally provided by relative humidity and pressure difference probes. Both operating ventilators (input and output) provide such an effective air-exchange of the ionization chamber detection volume that the substantial part of the radon progeny (principally 218Po), born in the detector by radon decay, is removed from the detection volume and the radon daughter products deposition is thus effectively suppressed. The construction of the detection system provides to measure the radon concentration itself, only insignificantly affected by signal from radon decay products. The air-exchange of the ionization chamber fulfills a condition:

Q/V >> λPo = 0,23 min-1,

where Q [m3.min-1] is the air flow through the ventilators inside the chamber, V [m3] is the chamber detection volume and λPo is the decay constant of 218Po [0,227 min-1].

Real time variations of radon concentrations are insignificantly influenced by „the memory effect“, caused by radon decay products.

Technical parameters of the radon monitor RADONIC 01
Basic parameters
Operating voltage of the detector                                                      150 V
Concentrations measuring range                                                       50 – 12 000 Bq·m-3
Current sensitivity of the chamber for a unit radon concentration      3 10-16  A.Bq-1.m3
Current sensitivity for the dose rate of external gamma radiation     222 Bq.m-3/mGy.h-1
Concentration resolution                                                                    2 Bq.m-3
Detection volume                                                                                8,4 l
Minimal effective air-exchange coefficient of the susceptible
 ionization chamber volume                                                                30 h-1
Operating conditions
External temperature                                                                         0 -  45°C
Relative air humidity                                                                           10 - 95%
Atmospheric air pressure                                                                   60 - 106 kPa
Equilibrium factor between radon concentration and equivalent
 radon concentration                                                                          0,2 - 0,7
Storing and transport condition                                                         -25 - +55 °C
Battery power                                                              built-in accumulator
                                                                                    12 V/500 m adapter
Weight                                                                                                4 500 g
Radon monitor dimensions                                                                 270 x 270 x 520 mm

Additional connection inputs for auxiliary sensors of temperature, pressure difference, relative humidity etc. are available.