An up-to-date radon-thoron discriminative detector has been developed for conducting a large scale survey. Comparing with our previous detector, some functional problems have been solved. The lowest and highest detection limits of the detector were estimated to be around 5 and 1000Bqm3 for radon, and 15 and 1000Bqm3 for thoron, respectively, with a 6month exposure and several theoretical assumptions. Small indoor survey were carried out in Japan and in Hungary using the present detector. The presence of thoron was demonstrated in any indoor surveys by the two results. Since any measurements without discrimination of radon isotopes will result in different risk estimates from actual situations, a special attention should be paid to thoron and its concentration should be accordingly measured as well as the radon concentration.

1.
T.
Iida
,
Q.
Guo
, and
M.
Ikebe
,
Health Phys.
69
,
508
(
1995
).
2.
S.
Tokonami
,
H.
Yonehara
,
W.
Zhuo
,
Q.
Sun
,
T.
Sanada
, and
Y.
Yamada
,
Proceedings of the Ninth International Conference on Indoor Air Quality and Climate
, Monterey, California, June 30–July 5,
2002
.
3.
K.
Fujimoto
,
S.
Kobayashi
,
M.
Uchiyama
,
M.
Doi
, and
Y.
Nakamura
,
Jpn. J. Health Phys.
32
,
41
(
1997
) (in Japanese).
4.
T.
Sanada
,
K.
Fujimoto
,
K.
Miyano
,
M.
Doi
,
S.
Tokonami
,
M.
Uesugi
, and
Y.
Takata
,
J. Environ. Radioact.
45
,
129
(
1999
).
5.
M.
Doi
,
K.
Fujimoto
,
S.
Kobayashi
, and
H.
Yonehara
,
Health Phys.
66
,
43
(
1994
).
6.
M.
Doi
and
S.
Kobayashi
,
Health Phys.
66
,
274
(
1994
).
7.
J.
Ma
,
H.
Yonehara
,
T.
Aoyama
,
M.
Doi
,
S.
Kobayashi
, and
M.
Sakanoue
,
Health Phys.
72
,
86
(
1997
).
8.
S.
Tokonami
 et al,
Radiat. Res.
162
,
390
(
2004
).
9.
W.
Zhuo
,
S.
Tokonami
,
H.
Yonehara
, and
Y.
Yamada
,
Rev. Sci. Instrum.
73
,
2877
(
2002
).
10.
International Committee of Radiological Protection, ICRP Publication No. 65,
1993
.
11.
Y.
Yamada
,
J. Health Sci.
49
,
6
(
2003
).
12.
H.
Ichitsubo
,
Y.
Yamada
,
M.
Shimo
, and
A.
Koizumi
,
J. Aerosol Sci.
35
,
217
(
2004
).
13.
Y.
Ishimori
,
T.
Ishikawa
, and
S.
Tokonami
,
Jpn. J. Health Phys.
39
,
263
(
2004
).
14.
S.
Tokonami
,
M.
Yang
, and
T.
Sanada
,
Health Phys.
80
,
612
(
2001
).
15.
S.
Tokonami
,
M.
Yang
,
H.
Yonehara
, and
Y.
Yamada
,
Rev. Sci. Instrum.
73
,
69
(
2002
).
16.
S.
Tokonami
,
W.
Zhuo
,
H.
Ryuo
,
H.
Yonehara
,
Y.
Yamada
, and
M.
Shimo
,
Radiat. Prot. Dosim.
103
,
69
(
2003
).
17.
Y.
Kobayashi
,
S.
Tokonami
,
H.
Takahashi
,
W.
Zhuo
, and
H.
Yonehara
,
Proceedings of the Sixth International Conference on High Levels of Natural Radiation and Radon Areas, Elsevier International Congress Series
,
2005
, Vol.
1276
, p.
281
.
18.
M.
Urban
and
E.
Piesch
,
Radiat. Prot. Dosim.
1
,
97
(
1981
).
19.
M. D.
Pearson
and
R. R.
Spangler
,
Health Phys.
60
,
697
(
1991
).
20.
S.
Tokonami
,
Proceedings of the Sixth International Conference on High Levels of Natural Radiation and Radon Areas, Elsevier International Congress Series
,
2005
, Vol.
1276
, p.
151
.
21.
M.
Doi
and
S.
Kobayashi
,
Jpn. J. Health Phys.
29
,
155
(
1994
).
22.
L. A.
Currie
,
Anal. Chem.
40
,
586
(
1968
).
You do not currently have access to this content.