| 摘要 |
FIELD: physics. ^ SUBSTANCE: total number of pulses of beta- and gamma-radiation from radon decay products is measured, where the radon is inside the accumulation chamber of a beta- or gamma counter whose sensitive surface is placed such that beta-radiation of soil radionuclides does not fall on it, and the base of the accumulation chamber is closed by a filter which filters out thoron from the ground. Before measurement, the chamber is ventilated for not less than 15 minutes and background measurements are taken for a time t1 not less than 5 minutes with the chamber open. The chamber is closed and for a period of time t2 ranging from 40 to 80 minutes, the number of pulses of beta- and gamma-radiation is measured. Radon flux density is then determined using the expression , where q is radon flux density from the ground surface, Bq m-2 s-1; N is the measured total number of pulses over time t2, pulses; Nf is the measured background value of the number of pulses over time t1, pulses; is a compensation factor, pulses s-1 Bq-1; S is the surface area of the base of the accumulation chamber, m2; is the decay constant of radon, s-1; t1 is the time for measuring the background, s; t2 is the time for accumulation of radon, s. ^ EFFECT: measuring radon flux density from the ground surface based on beta- and gamma-radiation which is suitable for use when conducting prolonged continuous measurements without participation of an operator. |
