EQUIPMENT FOR IN SITU PERMEABILITY MEASUREMENTS RADON - JOK

The gas permeability of soils is one of the important factors which determine the possible radon sources of any given site. In situ measurements of the gas permeability are therefore needed to estimate the radon risk at specific sites.

The RADON-JOK is a portable equipment, which has been developed for in situ measurements of gas permeability of soils. Its robustness and its simplicity is very practical for easy, quick and at the same time sufficiently exact in situ investigation. The principle of the RADON-JOK equipment consists of air withdrawal by means of negative pressure. Air is pumped from the soil under constant pressure through a specially designed probe with a constant surface of contact between the probe head and the soil. The constant active area is created in the head of the probe (driven into the soil to a measured depth) by the extrusion of the tip by means of the punch wire inside the probe by an exact distance. The special rubber sack, with one or two weights, pumps the air from the soil and allows to perform measurements at very low pressures. The gas permeability is calculated using the known air flow through the probe, which is defined by the known air volume (= 2000 ccm) in the rubber sack (depression of the bottom of the sack between two notches) and by the pumping time measured. The great advantage of RADON-JOK is the possibility to perform measurements independently of any source of energy (electricity, compressed air…).

Using the RADON-JOK system, the feasible range of measured gas permeability (k) is approx. from k = 10-11 m2 to k = 10-14 m2. The maximum detection limit (measured time of 8 s corresponds to k = 1.4 10-11 m2) is determined by the resistance of the equipment, the minimum detection limit depends on the time spent in any given measurement (measured time of 3600 s corresponds to k = 1.7 10-14 m2).

The RADON-JOK equipment (standard supply) includes basic accessories:

1 RADON-JOK equipment proper, 1 transport case, 3 tripod legs, 1 rubber tube 14/2 mm, 5 probes 12/2 mm - length 1,10 m, 2 punch wires, 2 weights, 300 “lost” sharp tips – special type for permeability measurements, 2 simple retractors, 1 distance ring, 1 distance screw, 1 drive in head, 4 penlight batteries, 1 plummet, manual and nomogram.