Radon (Rn) contents in spring water of Misasa spa, Sekigane spa, Togo spa and Ikeda spa were determined using a liquid scintillation counter. The contents were counted by appling the integral counting method with a liquid scintillation counter 3 hours and 10 minutes after extraction with toluene scintillator solution (PPO 4.0g and POPOP 100mg in 1000m
l toluene solution) from spring water.
The results obtained by this method showed a good correlation with that of IM-fontactoscopy (γ=0.995) or of an ionization chamber equipped with vibrating reed electrometry (γ=0.984) on the determination of Rn in spring water.
Rn contents in 60 samples of Misasa spring water were ranged from 1.35 to 686.
87
×10
-10Ci/
l (0.37-188.89 M.
E
.). Rn contents were shown to be above 20×10
-10Ci/
l (above 5.5 M.
E
., discriminating point of spring water from plain water in Rn contents) in 54 of 60 samples (90%), above 30×10
-10Ci/
l (above
8
.25 M.
E
., discriminating point of spring water for medical treatment from plain water in Rn contents) in 46 of 60 samples (77%) and above 181.
8
×10
-10Ci/
l (above 50 M.
E
., strong radioactive spring water in Rn contents) in 15 of 60 samples (25%), respectively.
Rn contents in spring water of Sekigane spa (15 samples), Togo spa (16 samples) and Ikeda spa (5 samples) were ranged from
22
.71 to 157.19×10-
10Ci/
l (6.25-43.23 M.
E
.), 0.43 to 38.68×10-
10Ci/
l (0.12-10.64 M.
E
.) and 407.4 to 7695.1×10-
10Ci/
l (112.0-2116.2 M.
E
.), respectively.
In Misasa spa, the mean value of Rn contents in
8
samples of ground water was 14.65×10-
10Ci/
l (4.03 M.
E
.) with a ranged from 2.64 to 32.13×10-
10Ci/
l (0.73-
8
.84 M.
E
.).
Rn contents in 10 samples of surface water (Mitoku river) were ranged from 0.39 to 3.18×10-
10Ci/
l (0.11-0.
87
M.
E
.). Rn contents in surface water of the Mitoku river was the highest around the center of Misasa spa area.
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