Underground Radiolab - Pieter van Beek, Marc Souhaut, Thomas Zambardi LAboratoire de mesure des FAibles RAdioactivités
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Underground Radiolab
LAboratoire de mesure des FAibles RAdioactivités
Tunnel EDF of Ferrières-sur-Ariège - Establishment of the University of Toulouse
Pieter van Beek, Marc Souhaut, Thomas Zambardi
- LAFARA : created in 2007 - Tunnel EDF of Ferrières (100 km from Toulouse) - 85 m thick rock cover (natural shield protecting against cosmic rays) - 5 last-gen gamma spectrometers - The lab is fully remotely controlled from Toulouse - Member of European CELLAR network, National network Becquerel and Regional PANGEE OMP Platform
French Authority of Nuclear Safety
Quality managment system certifications
International normative reference
ISO/CEI-17025
TYPE MATRIX CATEGORY REF. VALIDITY
1 Water Radium-226 & daughters 1_11 31/12/2024
1 Water Radium-228 & daughters 1_12 31/12/2024
1 Water Weight uranium 1_17 31/12/2024
2 Soils Gamma emitters > 100 keV 2_01 30/06/2026
2 Soils Gamma emitters < 100 keV 2_02 30/06/2026
2 Soils Radium-226 & daughters 2_11 30/06/2025
2 Soils Radium-228 & daughters 2_12 30/06/2025
LAFARA certified by ASN
2 Soils Weight uranium 2_17 30/06/2025
(French Authority of Nuclear Safety) 5 Gas Gamma emitters > 100 keV 5_01 30/06/2022 (R)
5 Gas Gamma emitters < 100 keV 5_02 30/06/2022 (R)
5 Gas Gazeous halogens 5_14 30/06/2022 (R)
3 Biological Radium-226 & daughters 3_11 WIP
3 Biological Radium-228 & daughters 3_12 WIP
3 Biological Weight uranium 3_17 WIP
Radiolab Analysis of radioactivity in all types of materials by gamma spectrometry Expertise in Environmental studies
Fields of application
Academic research Earth sciences, Oceanography, Cosmochemistry...
Medical Zr –Al ceramic prostheses, nuclear medicine
Building Building materials, paints
Cosmetics Minerals
Environment Soils, water, air
Food industry food
Aeronautics & space Embedded materials & recycling
Fraud control Origin of products (wood, mushrooms);
age (spirits), Luxury (counterfeit)
Nuclear instruments Material selection & optimization
238U Series 232Th Series 235U Series
238U 232Th 235U
4.5 109 a 1.4 1010 a 7.04 108 a
234Th 228Ra 231Pa
24.1 d 5.75 a 32500 a
234U 228Th 227Ac
2.5 105 a 1.91 a 21.8 a
230Th 224Ra 227Th
75200 a 3.66 d 18.7 d
226Ra 208Pb 223Ra
1602 a 11.4 d
222Rn 207Pb
3.83 d Naturals radioactives series
238U, 232Th, 235U
210Pb
22.3 a
210Po
138 d + cosmonuclides (14C etc…)
+ artificial radioelements (I-131, Am-241, Cs-137…)
206Pb
Geoscience applications :
Studies of Oceanography - Climat - Hydrology
Ocean circulation
Radium-226
Le Roy et al., 2018
ANR GEOVIDE
(2014-18, PI: G Sarthou, P. Lherminier)
Geoscience applications :
Studies of Oceanography - Climat - Hydrology
Ocean circulation Submarine Groundwater Discharge
Radium-226
Radium-228
228Ra
(dpm 100L-1)
Le Roy et al., 2018
ANR MED-SGD
(2016-21, PI: P. van Beek)
ANR GEOVIDE = Source of pollutants
(2014-18, PI: G Sarthou, P. Lherminier)
Datation of soils
Tchernobyl accident
= 1986
Atmospheric nuclear tests
Thiebault et al., 2017 = 1963
Thiebault et al., 2017
LEGOS, GET, ECOLAB, GEODE, CEFREM,
MIO, BRGM, ENS Lyon, Univ. Leeds
Datation des sédiments Environmental monitoring
Detection of the “radioactive cloud” of
Fukushima at the top of the Pic du Midi in 2011
I-131, Cs-137, Cs-134
Tchernobyl accident
= 1986
Atmospheric nuclear tests
Thiebault et al., 2017 = 1963
Thiebault et al., 2017
LEGOS, GET, ECOLAB, GEODE, CEFREM,
MIO, BRGM, ENS Lyon, Univ. Leeds
Perspective : Barrages EDFEquipments
5 last-gen gamma spectrometers
Ultra-sensitive HPGe detectors
3 well-type SAGe-Well®
2 planar-type
Cooling by electric cryo-generators
CryoPulse-5®+ (no liquid nitrogen required)
Robotic automated sampler
Lead Casltes VLA of 24 cm and underground
environment
Reduction of cosmic radiation
Reduction of background noise
Great analytical capacity
Remote management (piloting and
monitoring)Instruments of theLAFARA
5 low background gamma detectors
- 3 SAGe-Well type (Canberra-Mirion Lingolsheim) : 2 units Ø21 mm & 1 unit Ø32 mm
- 2 planar-type (1 coaxial Canberra-Mirion Lingolsheim et 1 Semi-Planar ORTEC-AMETEK)
- Since 2017, all LAFARA detectors are electrically cooled (no more nitrogen)
LAFARA detector model (here Latest generation LYNX (Canberra-Mirion)
well type) with electric cooling analog electronics in network, CP5-CO
and BIP-E cryogenerator controller for
management in autosampler mode.Background noise
from LAFARA
Lead Castle around the
EDF tunnel entrance (Ferrières- detectors
sur-Ariège - 100 km from
Toulouse)
LAFARA 2017
0,016 counts s-1 kg-1
(85 m of rock/ 200 m water equivalent)Reminder on interactions with matter
Detector calibration
A/ Energy calibration = Relationship between channels and peak energy
Determine the Canal-Energy correspondence
Number of channels selection (4000, 8000 or 16000) Energy is linearly related to the channels
(y=ax+b)
Energy range selection
Number of channels selection
Trade-off between peak analysis and peak detection
Peak analysis
Correct peak adjustment requires a certain number of
channels per peak. The more channels per peak, the better
the fit will be.
Peak detection
APEX gamma software keV-Channel
An ideal case would be having the whole counts in one
relationship (MIRION-CANBERRA)
channel. The less (channel) = the best (detection)Detector calibration
A/ Energy calibration = Relationship between channels and peak energy
Allows the identification of peaks
counts
Element Periode Energie Emission
keV % 1600 214Pb
228Ac 352 keV
1400 338.4 keV
Pb-210 22.26 a 46,5 4,05
Am-241 432,2 59,54 35,9
1200
Th234 24.1 d 63,29 3,812
Th234 24.1 d 92,38
5,58
Th234 24.1 d 92,8 1000 212Pb
214Pb
U235 7.038E+8 a 143,764 10,96 238.6 keV
295.2 keV
U236 7.038E+8 a 163,36 5,08 800 => 224Ra, 228Th
U237 7.038E+8 a 205,31 5,01
Ra-226 1602 a 186,21 3,59 600
U235 7.038E+8 a 185,71 57,2 226Ra
Pb-212 10.643 h 238,63 44,646 400 185.9 keV 214Pb 241.9 keV
Ra-223 11.434 d 269,43 13,6 200
Pb-214 26.8 min. 295,21 19,247
0
100,0 150,0 200,0 250,0 300,0 350,0 400,0 keV
Energy calibration is used to define
the final position of the peaks in the 223Ra + 228Ac : 270.3 keV
spectrum (Gain and Offset) + 219Rn : 271.2 keV
269.6 keVDetector calibration
B/ Performance calibration : use of a standard source (IAEA or LEA)
Absolute return
If the reference is the number of radiations emitted by the source
{
Nd
EffAbs = avec Nd Number of hits observed in the detector per sec.
N is Ni Nb of shots emitted per sec by the source
The absolute return depends on:
geometry (distance, container, etc.)
the intrinsic efficiency of the detector for a given energy
The "geometry" is defined by:
the distance between the source and the sample
the shape of the sample (spatial distribution)
the density of the sample (self-absorption)Detector calibration
B/ Performance calibration = Detection efficiency is a function of energy
Element Periode Energie Emission
keV % % émission
Pb-210 22.26 a 46,5 4,05
Am-241 432,2 59,54 35,9
Detector efficiency Th234 24.1 d 63,29 3,812 Reyss et al., 1995
Th234 24.1 d 92,38
5,58
Th234 24.1 d 92,8
U235 7.038E+8 a 143,764 10,96
U236 7.038E+8 a 163,36 5,08
U237 7.038E+8 a 205,31 5,01
Ra-226 1602 a 186,21 3,59
U235 7.038E+8 a 185,71 57,2
Pb-212 10.643 h 238,63 44,646
Ra-223 11.434 d 269,43 13,6
Pb-214 26.8 min. 295,21 19,247
The efficiency of the detector varies as a The efficiency of the detector
function of the energy varies as a function of the size
germanium crystalDetector calibration boxes
B/ Detector efficiency
12cc
61cc
- Analysis of standards in the same geometry 3cc
- Relationship: number of pulses detected activity 1cc
214Pb Sample geometry for planar type detector
352 keV
214Pb
295.2 keV
Nb of counts at 295.2 keV:
214Pb 241.9 keV
X counts 4980 Bq kg-1 x Y kg
analysed
Relationship to apply
for samples:
Example : RGU1 standard Number of hits detected => Activity
(4980 Bq kg-1)Correction of continuum and background noise
269.6 keV
1000
Continuum
Counts
Continuum 100 (right)
(left)
10
262 270 278
Energy (keV)
- Correction of continuum : Raw Peak - (continuum right + continuum left) / 2 = Net Peak
- Correction of background noise: Number of counts without sample (cpm)
(to be subtracted from the net peak)
+ Detection efficiency => quantification of activity in Bq or dpm
(per kg or per L of sample)Use of 210Pb deposited in the sediment to estimate
sedimentation rates
Ocean
226Ra 210Pb 210Pb =
excess
Retiré de 210Pb – (210Pb-226Ra)
son père total
supported
Sediment
226Ra 210Pb 210Pb
210Pb (Bq kg-1) Ln (210Pb)
0 0
10 10
Exponential fit Exponential fit
Depth (cm)
Depth (cm)
20 A = A0 e-λt 20 ln A = -λt + ln A0 with t = z / S :
m : slope ln A = -λz / S + ln A0
30 30 m = λ/ S
S = λ/ m
with λ = ln 2 / T 1/2
S usually in cm y-1 or mm y-1Thiebault et al., Anthopocene, 2017
Practical work: Study of a sample of marine sediment core
off New Zealand
- Visit of the LAFARA platform website
- Remote connection with LAFARA instruments
- Presentation of the APEX-gamma software (Mirion-Canberra)
- Energy calibration: identification of peaks
- Efficiency calibration: quantification of activities
- Analysis of gamma spectra of core samples
- Determine the activity in excess 210Pb
- Determine a sedimentation rate
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