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Calibration facility for portable gamma-ray spectrometers
Straz
pod Ralskem, Czech Republic
size of the
room: 22.4 x 12 m
Ground surface standards
Cylindrical concrete pads, diameter 1.9 m, thickness
0.62 m
(zero standard from silicious sand: size 2 x 2 m, thickness
0.8 m)
Density: 1.8 g/cm3
Density of the sand in the zero standard: 1.58 g/cm3
Geometrical correction is 1/0.934 = 1.071 for the detector height 6.3 cm (centre of the NaI(Tl) 76 x 76 mm
scintillation crystal)
Effective concentrations of elements K, U and Th in calibration pads from precise
gamma spectrometry, including change of environment between original and new placement
|
Calibration pad
|
% K
|
ppm U
|
ppm Th
|
|
K - pad PK
|
15.33
|
2.4
|
2.1
|
|
U - pad PU
|
0.24
|
29.2
|
2.4
|
|
Th - pad PTh
|
0.29
|
5.1
|
94.6
|
|
Background
- pad P0
|
0.02
|
0.3
|
0.9
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Besides the spectrometry calibration, the surface standards can be used
for simple test of the total
gamma radiometers.
Well logging standards:
Cylindrical concrete standards, diameter 1.4 m, height 1.2 m
Density of concrete: 1.8 g/cm3
The potassium standard is from powdery
kalium chloride fertiliser (technical
KCl) with density 1.15 g/cm3.
The zero standard from silicious sand: size 1.5 x 1.5 m, height 1.8 m, density of the sand
1.58 g/cm3.
Pipe: Aluminum, outer diameter 90 mm, inner diameter 80 mm
Average concentrations of elements K, U and Th in well logging standards from laboratory analyses in the year 1975
|
Calibration cylinder
|
% K
|
ppm U
|
ppm Th
|
|
K - cylinder KK
|
46.2
|
0.2
|
0.5
|
|
U - cylinder KU
|
0.3
|
1200
|
26
|
|
Th - cylinder KTh
|
0.3
|
61
|
1630
|
|
blank
standard K0
|
0.02
|
0.3
|
0.9
|
Apparent effective concentrations of elements K, U and Th in well
logging standards after the international
intercalibration (IAEA) in the
years 1989 and 2018 including pipe attenuation Al 90/80 for spectrometry tool (the higher
values in brackets on the right side
would be indicated after remove of pipes)
|
Calibration cylinder
|
depth [m]
|
% K
|
ppm U
|
ppm Th
|
|
K - cylinder KK
|
0.5 -
0.7
|
40 (42)
|
0.2
|
0.5
|
|
U - cylinder KU
|
0.5
|
0.3
|
1287
(1344)
|
25
(26)
|
|
0.6
|
1323
(1381)
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|
0.7
|
1239
(1293)
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Th - cylinder KTh
|
0.5
|
0.3
|
59
(61)
|
1529
(1586)
|
|
0.6
|
1445
(1498)
|
|
0.7
|
1441
(1494)
|
|
blank
standard K0
|
0.8 -
1.0
|
0.02
|
0.3
|
0.9
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Higher pipe attenuation for small energies
causes for total counts the apparent concentrations 1.066-times smaller as the values in brackets.
the potassium well logging standard KK after the move
from Bratkovice to Straz pod Ralskem
Layered well logging model:
Cylindrical concrete rings, diameter 0.9 m, height of one ring 0.1 m
Density of concrete: 1.8 g/cm3
Count: 18
Concentration: U 5 - 1155 ppm,
Th 3 - 2135 ppm
Pipe: Aluminium, outer diameter 90 mm, inner diameter 80 mm
the well logging layered model KV
Concentration of elements K, U and Th in the
rings of the layered model KV
|
ring
|
% K
|
ppm U
|
ppm Th
|
|
KVN 1
|
<
0.4
|
5
|
3
|
|
KVN 2
|
<
0.4
|
7
|
3
|
|
KVN 3
|
<
0.4
|
8
|
4
|
|
KVN 4
|
<
0.4
|
6
|
6
|
|
KVN 5
|
<
0.4
|
6
|
3
|
|
KVN 6
|
<
0.4
|
7
|
3
|
|
KVN 7
|
<
0.4
|
7
|
3
|
|
KVN 8
|
<
0.4
|
12
|
3
|
|
|
|
|
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KVTh 10
'0,05%'
|
<
0.5
|
40
|
673
|
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KVTh 11
'0,05%'
|
<
0.4
|
30
|
468
|
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KVTh 12
'0,20%'
|
|
73
|
2135
|
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KVTh 13
'0,20%'
|
|
82
|
2097
|
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*KVU
14 '0,03%'
|
|
288
|
35
|
|
KVU 15
'0,03%'
|
|
281
|
37
|
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KVU 16
'0,10%'
|
|
982
|
83
|
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*KVU
17 '0,10%'
|
|
1054
|
68
|
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KVUTh 18
'0,10/0,20'
|
|
1142
|
2040
|
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KVUTh 19
'0,10/0,20'
|
|
1155
|
1988
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(* The rings KVU 14 and KVU 17 were broken in several tiles. Now they are functional only in the configuration with other rings.)
The response of the 10 cm anomaly layer from two different
total gamma probes
Calculation of the
reverse filter for automatic interpretation
excel list
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