Assement of radionuclide
concentration in various samples
by gamma spectrometry and LSC
J. Berzins, D.Riekstina, O. Veveris
Institute of Solid State Physics University of Latvia
Dresden 2010
The Laboratory was organized as the group of the
Laboratory of nuclear reactions in 1986 after the
accident in Chernobil NPS with the aim to control via
gamma spectrometry the environment and measure the
radioactivity in foodstof and other samples. Since 1998
the group was reorganized to the Material radioactivity
testing laboratory. The quality assurance system was
implemented in our laboratory since the year 2000.
Different contaminate samples: soils, waters, metal
scrap and various types of samples, irradiated in
the research nuclear reactor, were measured by
gamma spectrometer. The concentrations of radionuclide
were determined using the high resolution HPGe gammaspectrometer type Ortec within the energy range of 502000 keV. For measuring of large radioactive waste
volums in the metal barrel, gamma-spectrometer with NaJ
detector were used. The uncertainty of measurements was
within the range of 3-10%, but the minimal detectable
activity – 0.3 Bq/kg.
The measurements of high tritium activities in reactor basin and
for monitoring contaminate groundwater were carried out with the
liquid scintillation spectrometer Packard TRI-CARB using the
scintillation liquid OptiPhase “HiSafe”3. The measurement time for
H-3 didn’t exceed some hours and uncertainty was less than 2%.
The credibility of obtained results is ensured by the quality
assurance and control. The main requisitions involved in the
quality assurance of the laboratory according to the requirements
of ISO/IEC 17025:2005 are:
1) the use of calibrated equipment only;
2) the regular long-time use of reference materials for the control
of equipment;
3) the regular participation in the interlaboratory intercomparison
exercises, organized by the RISO National Laboratory (Denmark)
and IAEA (Vienna).
Measurements
Free release of reactor materials
Monitoring for potentially contaminated territories
Water quality control
Customer service – J-131 from hospitals
- metal scrap from foreign countries
- samples from illegal radioactive
material transport
HPGe gamma spectrometer
Efficiency of HPGe detectors
ε 4.50E-02
4.00E-02
3.50E-02
3.00E-02
2.50E-02
2.00E-02
1.50E-02
1.00E-02
5.00E-03
0.00E+00
BSI
ORTEC
CANBERRA
E(keV)
0
500
1000
1500
2000
NaJ gamma spectrometer
Liquid scintilator spectrometer
iSOLO equipment for alfa and beta measurements
Methods
For the measurements we use 15 methods.
The most importent are:
•
Determination of the radionuclides concentration by high
resolution gamma-ray spectrometry. T190-1-24-237-2004
•
Water quality – Determination of the activity concentration
of radionuclides by high resolution gamma-ray
spectrometry. LVS ISO 10703:2008.
•
Water quality. Determination of the specific activity of
tritium. Liquid scintilation counting method. LVA ISO
9698:2003.
•
Building materials quality – Determination of the
radionuclides and specific activity of radionuclides in
building materials by gamma-ray spectrometry. LVS ISO
257:2000.
• Our internal quality audit program covers all
requirements of ISO/IEC 17025:2005 standard, but the
main attention is paid to the analysis of results of
laboratory’s
participation
in
intercomparison
measurements, their evaluation, interpretation and
determination of uncertainty sources.
• Since 1999 laboratory is a regular participant in the
interlaboratory intercomparison exercises organized by
the RISO National Laboratory (Denmark) and IAEA
(Vienna). Such nuclides as K-40, Mn-54, Co-57, Co-60,
Zn-65, Cs-134, Cs-137, Eu-152, Ra-226, U-238 and Th232 were analyzed in following intercomparison samples:
soils, sediment, seaweed, aerosol, grass, hay, meat,
dray milk, waters.
Quality assurance
Quality System
Experienced staff
Premises, surroundings
Validated methods
Calibrated equipment
Calibrated standards
Internal audit
Staff training
Participation in intercalibration
Quality control
Use of standard samples
Measurement of background
Analysis in duplicates
Control charts: background,
standard peak stability
Reference materials
Participation of laboratory in the intercomparison exercises
Year
Organizer
Object
Radionuclides
1999
Risoe National laboratory,
Denmark
Sediment, milk, meat,
seaweed, hay
K-40, Mn-54, Co-60,
Cs-137, Ra-226,
Th-232
2000
Risoe National laboratory,
Denmark
Milk, aerosols, soil,
seaweed
K-40, Cs-137, Co60, Mn-54, Ra-226,
Th-232
2002
IAEA, Vienna
Mineral matrix
Mn-54, Co-57, Co60, Cs-134, Cs-137,
Eu-152
2003
Risoe National laboratory,
Denmark
milk, mineral matrix,
seaweed
Cs-137, K-40
20042005
Risoe National laboratory,
Denmark
Sediment, soil,
seaweed
K-40, , Cs-137, U238, Th-232
Soil, grass, water
K-40, Mn-54, Co-60,
Zn-65, Cs-134,
Cs-137
2006
IAEA, Vienna
90,0
Activity, Bq/kg
80,0
70,0
60,0
x1/10
50,0
40,0
30,0
Series1
20,0
Series2
10,0
0,0
Cs-137
Co-60
Mn-54
K-40
Ra-226
Radionuclides
Comparision of reported value with
the weighted mean in seaweed, Risoe
Series 1-reported value; series 2-weighted mean
Figure compares our results with the weighted mean in seaweed. There is
a good agreement between them.
Column diagram of sum of z-scores for results from all radionuclides combined
showing contributions from individual samples (No. 17-Laboratory of Radiation
Physics).
137Cs
content in mushrooms in Latvia (1987)
Bq/kg
250
200
150
100
50
0
1
6
11
16
21
26
31
36
41
46
51
56
61
66
71
76
81
86
91
96
101
106
111
Sample number
Cs-137 radioactivity of soils in the 3 km zone of the Salaspils nuclear
21
reactor
Shut-down medical facility Dubulti
Boring of samples
22
400
350
300
Bq/kg
250
1m
2m
3m
4m
200
150
100
50
0
Bore 1
Bore 2
Bore 3
Bore 4
Pollution with Ra-226 depending on the depth in Dubulti
D(nSv/h)
6000
5000
4000
3000
2000
1000
0
0
2000
4000
6000
8000 A(Bq/kg)
Ra_226 concentration in the waste from Dubulti (in barrels)
Concentration of radionuclides in soils (Salaspils)
B k/kg
1000
100
10
1
1
3
5
7
9
11 13 15
S am pling points
K -40
Th-232
U-238
C s -137
Concentration of radionuclides in soils (Baldone)
Bk/kg
1000
K-40
100
Th-232
U-238
10
Cs-137
1
1 2 3
4 5 6 7 8 9 10 11 12 13
Sampling points
Water analysis
of tritium
Drinking water
Communal water
sources
Ground water
Water in food industry
Pollution monitoring
10000
Bq/L
1000
2B
9V
10V
100
10
1
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
Years (sampling in October)
Tritium concentration in the wells of reactor territory
10000
Bq/L
1000
y 2004
y 2007
y 2009
100
10
1
1
3
5
7
9
11
Months
Tritium concentration in the well 10V of reactor territory
100000
Bq/L
10000
5
8
B3
B4
1000
100
10
1
1997
1999
2001
2003
2005
2007
2009
Years (October)
Tritium concentration in the wells of repository territory
10000
Bq/L
1000
y 2007
y 2009
100
10
1
1
2
3
4
5
6 7 8
Months
9
10 11 12
Tritium concentration in the well B4 of repository territory
Results of tritium detection in Latvia:
Communal water sources – 155 objects
5 Bq/L < T < 10 Bq/L
0,01 Bq/l < α < 0,2 Bq/l
0,1 Bq/l < β < 0,6 Bq/l
Water for food industry – 54 objects
5 Bq/L < T < 10 Bq/L
0,01 Bq/l < α < 0,05 Bq/l
0,1 Bq/l < β < 0,4 Bq/l
Conclusions
The use of gamma and beta spectrometry methods allow:
• establish the pollution level in the territories included in the
monitoring decrease during the last years however
unexpected changes was detected;
• identify and evaluate the wastes of various origin;
• control the quality of drinking water according to the Latvian
Cabinet of Ministers regulations No.235, adopted in 2003,
provision the entry in force of the EU Council Directive
98/83/EC.
Only credible and justified results can be the basis for further
use in any field, thus making it possible to make legitimate
decisions.
Thank
you
your
Thank
youfor
for
yourattention
attention