| 3. Underground fasilities in the world |
In radiation and gamma ray measurements, it is important to reduce the
background noise of detectors and activation of shielding materials derived from secondary cosmic-ray components (muons and neutrons). It
is difficult to reduce these components by conventional shielding at aboveground.
The intensity of secondary cosmic-ray components decreases with the depth of overburden at the underground fasility.(Refer to Figure 4.1)
|
for measurements of physical phenomena
There are many facilities in the world located 100 - 1500 m below ground
for measurements of rare physical phenomena.
In Japan, these
are the Cosmic Ray Research Institute, which is an inter-university facility of
the University of Tokyo that runs the Super-Kamiokande Experiment in the
Kamioka Observatory (a former mine 1000 m below ground (2700 mwe)) and the Oto Cosmo
Observatory (the underground laboratory of Osaka University located in
Oto-mura; 500 m below ground). |
for low level radioactivity measurements
There are some underground laboratories worldwide for low level radioactivity
measurements as shown in Table 3.1. In Japan, they are OUL and the Cosmic
Ray Research Institute which has a facility at the Kashiwa, Chiba branch
campus of the University of Tokyo (20 m below ground). In OUL, the use of 17 detectors is exceptional and all detectors provide
excellent bacground condition, stability and counting efficiency. |
|
Table 3.1. Underground laboratories and detectors for low level radioactivity
measurements.
|
|
|
Lab.
|
Loc.,
Country
|
Depth
(m)
|
mwe
|
HPGe Relative Eff%,
Detector type
(C:
coaxial, W: well, P: planar)
|
BG(d-1
kg-1),
0.04-2.7MeV,
(veto BG)
|
|
CELLAR
|
IRMM
|
Geel,
Belgium
|
223
|
500
|
C(60%,
106%, 50% ),
P(8%)
|
260,
357, 1894,
1317
|
|
Max-Planck
Inst.
|
Heidelberg,
Germany
|
15
|
25
|
C(22%,
31%, 37%),
W(17%)
|
2971,
2949
4052
|
|
VKTA
|
Dresden,
Germany
|
47
|
110
|
C(30%,
41%),
W(30%)
|
9713,
17285,
3870
|
|
LSCE
|
Frejus
Tunnel, France
|
1750
|
4800
|
W(215cc,
427cc, 910cc)
|
707,
301, 186
|
|
INFN-LNGS
|
Gran
Sasso, Italy
|
1400
|
3800
|
C(120%,
100%)
|
87,
30
|
|
IAEA-MEL
|
Monte
Carlo, Monaco
|
14
|
35
|
C(100%,
170%),
W(150%, 200%)
|
8136,
6096 (1368,840),
5400, 6960(1632,1008)
|
|
ARCS
|
Seibersdorf,
Austria
|
0
|
|
P(55%,
55%)
|
129600(9242)
|
|
PTB
|
Braunschweig,
Germany
|
925
|
2100
|
88%,
94.5%
|
1135,
278
|
|
Univ.
Iceland
|
Reykjavik,
Iceland
|
165
|
300
|
NaI(Tl)
|
|
|
OUL
|
Ogoya Underground Lab.
|
Komatsu, Japan
|
135
|
270
|
C(94%),
W(73%, 71%, 71%, 71%, 65%, 56%, 56%, 56%, 50%, 37%, 36%),
P(18%, 34%, 34%, 22%, 22%, 18%)
|
788,
1451, 1181, 1800, 2505, 1887, 1961, 2471, 1732, 1591,1945,
2286, 1333, 1216, 2714
|
CELLAR: Collaboration of European Low-level underground LAboRatories
(2003)
|
|
|
