Calibration facility for portable gamma-ray spectrometers
Straz
pod Ralskem, Czech Republic
![](obr/posit1enm.jpg)
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
|
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)
|
0.7
|
1239
(1293)
|
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
|
Higher pipe attenuation for small energies
causes for total counts the apparent concentrations 1.066-times smaller as the values in brackets.
![](obr/stand6_KKm.JPG)
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
![](obr/stand7_KVm.JPG)
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
|
|
|
|
|
KVTh 10
'0,05%'
|
<
0.5
|
40
|
673
|
KVTh 11
'0,05%'
|
<
0.4
|
30
|
468
|
KVTh 12
'0,20%'
|
|
73
|
2135
|
KVTh 13
'0,20%'
|
|
82
|
2097
|
*KVU
14 '0,03%'
|
|
288
|
35
|
KVU 15
'0,03%'
|
|
281
|
37
|
KVU 16
'0,10%'
|
|
982
|
83
|
*KVU
17 '0,10%'
|
|
1054
|
68
|
KVUTh 18
'0,10/0,20'
|
|
1142
|
2040
|
KVUTh 19
'0,10/0,20'
|
|
1155
|
1988
|
(* The rings KVU 14 and KVU 17 were broken in several tiles. Now they are functional only in the configuration with other rings.)
![](obr/KV_dipl1m.jpg)
The response of the 10 cm anomaly layer from two different
total gamma probes
![](obr/deconv1m.jpg)
Calculation of the
reverse filter for automatic interpretation
excel list
|