Introduction toISO-FOOD

Prof Milena Horvat

Dr David HeathERA Chair holder

ISO-FOOD Summer School Radionuclides in FoodJune 6-10, 2016Jožef Stefan Institute, Department of Environmental Sciences, Ljubljana, Slovenia

1949 – Institute of Physics1959 – Jožef Stefan Nuclear Institute1966 – Triga Mark II research reactor1969 – Jožef Stefan Institute

Jožef Stefan 1835 – 1893

19th century physicist, Stefan-Boltzmann law of black-body radiation

j = σT4

Sun's surface (5,430 °C)

(5,504 °C)

Jožef Stefan Institute

• Premier research institution

• 800 staff (app. 400 Ph.D)

• 28 Research Departments• 12 Research Centres• 4 Centres of Excellence

• Applied and basic research

• production and control technologies• communication and computer

technologies• biotechnologies• new materials• environmental technologies• nanotechnologies• Reactor/nuclear engineering

• 248 International Projects (98 EU) (2015)

Fundamental and applied research

natural sciences, physical sciences and engineering

Jožef Stefan Institute

Department of Environmental Sciences

Dept. of Environmental Sciences

Radiochemistry

Radioecology

25 research staff

6 technical and admin staff

18 PhD students

In 2015 opening of the 1100 m2

of new and 800 m2 of renewed laboratory space with new equipment (6.7 mioEUR)

• Clean laboratories and laboratories for radiochemistry (3000m2 laboratory space, 800 m2 office space)

• Isotope ratio mass spectrometry

EA-IRMS, DI-IRMS, Py-IRMS, GC-C-IRMS, MC-ICP-MS

• Mass spectrometryUPLC-qTOF-MS/MS, GC(IT)MS, GC-MSD, LC-MS/MS, GC-MS/MS, ICP-MS, ICP-MS QQQ, LA-ICP-MS, LC-ICP-MS, GC-ICP-MS, SP-ICP-MS,

• SpectrophotometryHG-AFS, CV-AFS

• Nuclear methodsTRIGA MARK II nuclear reactor, alpha, beta and gamma counting, NAA

• Access to equipment: JSI departments & infrastructure (microscopy, NMR centre)

Infrastructure and equipment

Environment, health and food related projects

The name given to the EU project (FP7) designed to establish the “ERA Chair for isotope techniques in food safety, quality and traceability” (2014)

ERA Chairs are a new EU measure aimed at bridging the research and innovation divide in Europe (RIS3)

“niche areas of competitive strength“

“Unlocking the capacities of the JSI for food research”

5 year EU funded project (2014-2019)

National, EU projects and collaboration with international partners, Industry

What is the ERA Chair ISO-FOOD?

PC, Chair holder , FTO

Scientific Executive Committee

Post-docs and PhDs

Dept. of Environ. Sciences + others

Stakeholders

Who’s involved?

JSIPS

Our vision… To become a recognized research and education centre

in isotope and chemical techniques in food (+feed) research

Create (Research) & transfer knowledge (Educate)

Unlock capacity of the JSI

Multi- and interdisciplinary ERA Chair

Critical mass of Knowledge and resources

Excellence in research and education

New and innovative isotopic and chemical analyses for food safety, quality and traceability

Our mission…

What do we do?

Metrology Support

Organic contaminants

Elementspeciation and fractionation

Where is our research focus?

• Doctoral course (JSIPS)

• Interlaboratory comparison exercises

• Stakeholder Events (open days etc., public lectures, brochure)

• ISO-FOOD Conference

• Method Accreditation

• Metrology• Food authenticity and traceability• Nanoparticles in food• Isotopic techniques in food characterization• Radionuclides in food• Element speciation in food analysis

Other…

Transfer knowledge (education)

Education and Outreach

• Exploratory Workshops,

• Training Events, Summer Schools

• Scientific papers

Thank you for your attention

Have a great Workshop!

www.isofood.eu

Thank you for your attention

Have a great Workshop!

www.isofood.eu

Thank you for your attention

www.isofood.eu

Our research focus spans the entire Food Supply Chain

ISO-FOOD Summer School

Radionuclides in food

June 6-10, 2016, Ljubljana

Ljudmila Benedik

EU Legislation

Radionuclides in

food and water

Ljudmila Benedik

Euratom Treaty

The task of the community

Article 2:

In order to perform its task, the Community shall,

as provided for in this Treaty:

a) …

b) establish uniform safety standards to protect

the health of workers and of the general public

and ensure that they are applied

c) … etc

Chapter III:

Health and Safety

Article 30 - basic standards

Article 31 - group of experts

Article 34 - dangerous experiments

Article 35/36 - environmental monitoring

Article 37 - plans to release

radioactive waste

Article 38 - recommendations on the

level of radioactivity

Article 30 of Euratom Treaty

Basic standards shall be laid down within the Community for the protection of the health of workers and the general public against the dangers arising from ionization radiation

“basic standards” means:

Maximum permissible doses compatible with adequate safety;

Maximum permissible levels of exposure and contamination;

The fundamental principles governing the health surveillance of workers.

Article 38 of Euratom Treaty

The Commission shall make recommendations to the Member States with regard to the level of radioactivity in the air, water and soil.

In cases of urgency, the Commission shall issue a directive requiring the Member State concerned to take … all necessary measures to prevent infringement of the basic standards and to ensure compliance with regulations.

Should the State fail to comply within the period laid down, the Commission or any Member State may forthwith, …, bring the matter before the Court of Justice

EURATOM

Basis Safety Standards

European radiation protection legislation

ensure the highest possible protection of

workers, members of the public and

patients against the dangers arising from exposure to ionising radiation

First Directive adopted in 1959

Amended in 1962, 1966, 1976, 1980, 1984,

1996

Latest in 2013

Basic Safety Standards

Council Directive 2013/59/Euratom laying down basic safety standards for protection against the dangers arising from exposure to ionizing radiation

(OJ L13, 17.01.2014, p. 1-73)

Supplementary

Drinking water quality

Food and feed – maximum permissible contamination levels after a nuclear accident

EU Regulation

Radioactive contamination

Maximum level of radioactive contamination in foodstuffs

Arrangements for agricultural import following Chernobyl accident

Arrangements for exporting foodstuffs and feedingstuffs following a nuclear accident

Early exchange of information in the event of a radiological emergency

http://europa.eu/legislation_summaries/food_safety/contamination_environmental_factors/index_en.htm

Overview of EU radiation

protection legislation

https://ec.europa.eu/energy/node/1219

Drinking water

Contamination of foodstuffs and feedingstuffs

Post Chernobyl

Future accidents

Drinking water

Council Directive of 15 July 1980 relating to

the quality of water intended for human

consumption (OJ, L. 229, 30.8.1980, 11-29, 1980).

radioactivity

uraniumno mentioned

Drinking water

Council Directive 98/83/EC of 3 November. The quality of water intended for human consumption (OJ L. 330, 5.12.1998,. 32-54, 1998).

the reference dose level of the committed annual effective dose due to drinking water consumption is 0.1 mSv

the total indicative dose must be evaluated excluding tritium, 40K, 14C, radon and its decay products, but including all other radionuclides of the natural decay chains

2001/928/EURATOM

Commission Recommendation of 20

December on the protection of the public

against exposure to radon in drinking

water supplies. (OJ, L.344, 28.12.2001,. 85-88, 2001)

Radon > 1000 Bq/L

Pb-210 0.2 Bq/L

Po-210 0.1 Bq/L

COUNCIL DIRECTIVE

2013/51/EURATOM

COUNCIL DIRECTIVE 2013/51/EURATOM of

22 October 2013 (OJ. L.296/12-21, 7.11.2013)

laying down requirements for the protection

of the health of the general public with

regard to radioactive substances in water

intended for human consumption

Define reference values for each single, the most

common natural and man-made radionuclides

COUNCIL DIRECTIVE

2013/51/EURATOM

Define reference values for each single, the most

common natural and man-made radionuclides

If the gross alpha activity exceeds 0,1 Bq/L

If the gross beta activity exceeds 1,0 Bq/L

2013/51/EURATOM

Origin Nuclide Derived concentration

(Bq/L)

Natural

From uranium

and thorium

decay

chains

U-238 3,0

U-234 2,8

Ra-226 0,5

Ra-228 0,2

Pb-210 0,2

Po-210 0,1

2013/51/EURATOM

Origin Nuclide Derived concentration

(Bq/L)

Artificial

Fission and

activation

products

C-14 240

Sr-90 4,9

Pu-239/Pu-240 0,6

Am-241 0,7

Co-60 40

Cs-134 7,2

Cs-137 11

I-131 6,2

WHO Guidelines for Drinking-water Quality

http://apps.who.int/iris/bitstream/10665/44584/1/9789241548151_eng.pdf

Chapter 9: Radiological Aspect

Recommended screening level for gross

alpha and beta activities

Guidance levels for natural and man-made

radionuclides

Derived concentrations for

radioactivity in water in Bq/L

Nuclide EU (2013) WHO (2011)

U-238 3,0 10

U-234 2,8 1

Ra-226 0,5 1

Ra-228 0,2 0,1

Pb-210 0,2 0,1

Po-210 0,1 0,1

Th-232 1

Th-228 1

Th-230 1

Derived concentrations for

radioactivity in water in Bq/L

Nuclide EU (2013) WHO (2011)

H-3 < 1000 10000

C-14 240 100

Sr-90 4,9 10

I-131 6,2 10

Cs-134 7,2 10

Cs-137 11 10

Pu-239 0,6 1

Am-241 0,7 1

EU (2013) WHO (2011)

Recommended dose level

of commited annual

effective dose due to water

consumption

0,1 mSv 0,1 mSv

Gross alpha activity 0,1Bq/L 0,5 Bq/L

Gross beta activity 1,0 Bq/L 1,0 Bq/L

COUNCIL REGULATION

No 3954/87

laying down maximum permitted levels of

radioactive contamination of foodstuffs

and of feedingstuffs following a nuclear

accident or any other case of radiological

emergency (OJ, L 371, 20.12.1987).

COUNCIL REGULATION

2016/52/EURATOM

COUNCIL REGULATION (Euratom) 2016/52

of 15 January 2016 (OJ, L 13/2-11, 20.1.2016)

laying down maximum permitted levels of

radioactive contamination of food and

feed following a nuclear accident or any

other case of radiological emergency

MAXIMUM PERMITTED LEVELS OF

RADIOACTIVE CONTAMINATION OF FOOD

Isotope group Infant

food

(Bq/kg)

Dairy

produce

(Bq/kg)

Other food

(except minor

food) (Bq/kg)

Liquid food

(Bq/kg)

Σ isotopes of Sr,

Sr-9075 125 750 125

Σ isotopes of I

I-131150 500 2000 500

Σ isotopes of

alpha emitters,

Pu-239,Am-2411 20 80 20

Σ other nuclides

t1/2 > 10 d,

Cs-134, Cs-137400 1000 1250 1000

C-14, H-3 and K-40 are not included

Why determination of

radionuclides?

the dose coefficients are always related to specific radionuclides. U-238 and Th-232 decay series nuclides have the highest values of dose coefficients.

Radiotoxicity210Po > 228Ra > 210Pb > 226Ra > 234U > 238U > 224Ra > 235U

Chemical toxicity Uranium as toxic heavy metal

WHO (2011): 30 µg/L (1998: 2 µg/L; 2004: 15 µg/L)

USA (EPA 2000): 20 µg/L

Germany (2006): 2 µg/L (mineral water)

1 µg U = 12.4 mBq

Effective dose coefficientsEffective dose coefficient (µSv Bq-1)

(96/29/EURATOM)

Radionuclide Adults Children (7–12 y)Infants

(0-1 y) (1–2 y)

238U 0.045 0.068 0,34 0.120

234U 0.049 0.074 0,37 0.130

228Ra 0.690 3.900 30,0 5.700

226Ra 0.280 0.800 4,70 0.960

210Pb 0.690 1.900 8,40 3.600

210Po 1.200 2.600 26.0 8.800

239 Pu

241Am

0,250

0,200

0,270

0,220

4,20 0,420

3,70 0,370

(Litre y-1) (WHO) 750 350 150

Metrology in (Radio)Chemistry

Ljudmila Benedik

Metrology

METROLOGY = Science of Measurement

Understanding

the measurement procedure

Measurement

measurement is a ratio of an

“unknown” to a “known” quantity

To determine:

- The dimension

- The quantity

- The capacity of something

- …

Importance of measurement

Economic industry

commerce

Governments law regulation and implementation

health and safety

environment protection

science / research

military services navigation

Social communications

Analytical data

Expressed according to recognised units

Comparable between laboratories

Comparable over time

User(s) must be provided with clear

information regarding their significance

Meter convention

Diplomatic treaty

Paris, May 20, 1875

SI metric system

Seven base units

Common system of units

International uniformity in measurement

Harmonized legislation

Metric System (SI)

Mass kilogram (kg)

Length meter (m)

Time second (s)

Temperature kelvin (K)

Electric current ampere (A)

Amount of substance mole (mol)

Luminous Intensity candela (cd)

Metric System (SI)

All other units are derived from primary seven Density: kilogram per cubic metre kg/m3

Speed: metre per second (m/s)

Concentration: mol per cubic metre (mol/m3) gram per kilogram (g/kg)

Volume: 1000 L = 1 m3

Surface, pressure, viscosity, etc.

Ionising radiation & radioactivity: 1 Bq = decay per second

Derived units

http://www.physics.nist.gov/cuu/Units/SIdiagram.html

Importance of common

system of units

On September 23,1999, the Mars Climate

Orbiter burned out completely

(Report on the loss of NASA’s Mars Orbiter spacecraft)

“Mission specifications called for using metric units, but the Lockheed group sent navigation information in English units. The mix-up meant that Lockheed engineers modelled navigation with pounds force (the English unit for measuring thruster impulse) while JPL did its calculations in newtons (the metric measurement). One pound force is equivalent to 4.45 newtons.”

What is measurement

Any measurement is the establishment of

a RATIO of an unknown to a known

quantity

defining the agreed unit

expressed in the same unit

Metrology in physics

Often relies on direct measurements

Mainly Sample-independent Temperature, length, mass, …

Measurement = comparing a quantity

E.g. mass relate to kg

Major impact: calibration of equipment

Metrology in chemistry

A lot of various factors affect the quality

of results

Strongly Sample-dependent

Determination of radionuclide in…

food

water

soil

...

Metrology in (radio)chemistry

Measurement = comparing a quantity of analyte

E.g. Radionuclide(s) in food relate to Bq/kg

U, Th in food, water mg/kg, mg/L

Major impacts sampling

Sample preparation

Sample dissolution

Calibration solutions

Equipment calibration

…

Metrology in chemistry

Metrology includes all aspects both theoretical and practical with reference to measurements whatever their uncertainty, and in whatever fields of science or technology they occur.

VIM – International

Vocabulary in Metrology

http://www.bipm.org/en/publications/guides/vim.html

Unified terminology

Metrology in chemistry

Basic glossary according to VIM

Measurement determining a value of a quantity

Measurand what you try to measure

Analyte the compound, species you measure

Model equation to use for calculation

Measurement in chemistry

Sample preparation in the lab

Sub-sampling, dissolution, preconcentration,

separation, dilution, …

Calibration

Measurement

Data evaluation

Result reporting

Aspects of metrology

Analytical measurements need to be

comparable in time and space

Traceability is the best way to achieve this

Traceability

Comparisons to nationally or

internationally accepted values

Definition of Traceability

Traceability is defined as the property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties.

(VIM)

Definition of Uncertainty

(VIM)

“a parameter associated with the result of

a measurement, that characterizes the

dispersion of the values that could

reasonably be attributed to the

measurand”

RESULT = VALUE ± UNCERTAINTY

Metrology Concepts

Uncertainty

Value assigned to a measurement result that characterizes

how well it is known/unknown

Measurement

result Potential Value

Interval

around the

measurement

result

Steps of evaluation of

uncertainty

Specify the measurand

Specify the measurement procedure

Specify a model equation and input quantities

Identify the sources of uncertainty

Quantify the uncertainty components

Calculate the combine standard uncertainty

Calculate the expanded uncertainty

Uncertainty components

Type AEvaluated from the statistical distribution of the results of series of measurements and characterised by standard deviations Derived from repeated measurements

Quality control material

Duplicate analysis of samples

Normal distribution

Standard uncertainty = standard deviation

In nuclear measurements:

Standard uncertainty = areaPeak

Uncertainty components

Type BCharacterised by standard deviations, evaluated from assumed probability distributions based upon Previous measurement data

Professional opinion

Manufacturer’s data

Uncertainties assigned to reference material

Type B Triangular distribution

20

Volume of the sample

Type B Rectangular distribution

21

The value is between the limitsa- … a+

Standard uncertainty = 3

001.0

Type B - Certificates

Definitions

Accuracy

Closeness of agreement of a measured

value (or series of values) with the known

“true” value of a quantity (accepted

reference value).

Definitions

Reproducibility (Precision)

Closeness of agreement between a series of

measured values for the same quantity. The true

value of the quantity may be unknown or not

considered.

Test results are obtained with the same method

on identical test items in different laboratories

with different operators using different

equipment

Definitions

Repeatability

Independent test results are obtained with

the same method on identical test items in

the same laboratory by the same operator

using the same the same equipment with

short intervals of time

Definitions Specificity

Response of a single analyte, not affected by possible interferences

SensitivityMinimal significant variation of a measurement result

Linearity Capacity of obtaining in a given interval, results that are directly proportional to the analyteconcentration

Definitions

Limit of detection

Smallest quantity of analyte that may de

detected but not quantified

Limit of determination

Expression of the smallest amount of analyte

which may be quantified

Quality control

Trueness

Closeness of agreement between the results of measurement and the true value of the measured value

Precision

Closeness of agreement between results of measurement of a same substance applying the same experimental procedure several times in the same conditions

Accuracy vs Precision

From Basic Laboratory Methods for Biotechnology: Textbook and Laboratory Reference, Seidman and

Moore, 2000

a) Good repeatability / poor accuracy

b) Poor repeatability / good accuracy

c) Poor repeatability / poor accuracy

d) Good repeatability / good accuracy

Quality control

Reference material

Material or substance one or more of

whose property values are sufficiently

homogeneous and well established to be

used for the calibration of an apparatus,

the assessment of a measurement method,

or for assigning values to materials

(ISO Guide 30)

Quality control

Certified Reference Material

A reference material, accompanied by a certificate, one or more of whose property values are certified by a procedure which establishes traceability to an accurate realisation of the unit in which the property value are expressed, and for which each certified value is accompanied by an uncertainty at a stated level of confidence

(ISO Guide 30)

Quality control

Control charts

Graphical mean to evaluate the

reproducibility of a method

Interlaboratory testing

Several laboratories analyse one or several

identical samples

References

International Organization for Standardization. ISO/IEC 17025:2005 General

requirements for the competence of testing and calibration laboratories. 2nd ed.

Geneva: International Organization for Standardization; 2005

Harmonized guidelines for single-laboratory validation of methods of analysis (IUPAC Technical Report, 2002)

The Fitness for purpose of Analytical Methods, Eurachem Guide, 1998

In-House Method Validation—A Guide for Chemical Laboratories, LGC, UK, 2003.

JCGM 200:2012, International Vocabulary of Metrology - Basic and general concepts and associated terms (VIM)

Eurachem CITAC guide CG4, Quantifying Uncertainty in Analytical Measurements,

Second addition, 2000, www.eurachem.org

Vetter, T.W., National institute of Standards and Technology (NIST). Quantifying

measurement uncertainty in analytical chemistry – A simplified practical approach

(Kragten), proceedings of measurement Science Conference 2001, Session V-B,

Anheim, 2001, www.p2pays.org/ref/18/17628.pdf

Quality Assurance in Analytical Chemistry, Training and Teaching, Eds.

B.W.Wenclawiak, M. Koch, E. Hadjicostas; Springer-Verlag Berlin Haidelberg 2003.

Joint Research Centrethe European Commission's

in-house science service

Traceability to

the becquerel

Stefaan Pommé

2

Slides 3 to end are the intellectual property of Stefaan Pommé (European Commission, Joint

Research Centre)

“Unauthorised reproduction constitutes a copyright infringement and may lead to

prosecution or civil proceedings“

Copyright notice

3

Joint Research Centre (JRC)

The European Commission’s Research-Based

Policy Support Organisation

www.jrc.ec.europa.eu

4

Joint Research Centre

Geel (B)

Petten (Nl)

Karlsruhe (D)

Ispra (I)

Sevilla (S)

Centres in 5 Member States – 3000 staff

Research areas:

– Growth & Innovation

– Energy, Transport & Climate

– Sustainable Resources

– Space, Security & Migration

– Health, Consumer & Reference Materials

– Nuclear Safety & Security

5

ART 8 EURATOM TREATY

ensure that a uniform nuclear terminology and a standard system of measurements are established.

=> Establish the becquerel

The Joint Centre shall include:

… a bureau of standards specialising in nuclear measurements

for isotope analysis and absolute measurements of radiation

and neutron absorption

6

The Radionuclide Metrology Team

7

Major competences

Standardisation of activity

Measurement of nuclear decay data

Characterisation of reference materials

Organisation of proficiency tests

Technical standards

8

9

Radionuclide

Metrology

Sector

To establish a common measurement system for

radioactivity

10

HEALTH FOOD INDUSTRY RESEARCH ENVIRONMENT

GLOBALHARMONIZATION

STANDARDIZATION

TRACEABILIT

Y

NATIONALSTANDARDS

E Q U I V A L E N C E

KEYCOMPARISONS

Becquerel

The NEED for a REFERENCE

11

Establishing the becquerel

SIR

reference value~ 60 Radionuclides

becquerel

BIPM, Sèvres (F)

12

Realisation of SI-unit Bq

“Direct” measurement of the number of spontaneous transitionsof a radionuclide in a time interval

= primary standardisation= realisation of the Becquerel [s-1]

Primary standard= directly measured source + Activity + Uncertainty

Secondary standard=> source with activity determined by relative measurement to primary standard

13

Primary → Secondary → End user

Secondary standard in

solution measured by

relative method in

ionisation chamber

Apply a drop of this

solution in a calibration

source for the end user

14

International collaboration

14

The RESPONSIBILITY for the REFERENCE

The realisation of the Becquerel is DIFFICULT• ~100 radionuclides:

− different decay schemes− different measurement techniques

National Metrology Institutes have to COLLABORATE• Only a few labs in the world can standardise

most radionuclides• We need redundancy of measurement methods

15

A multitude of decay types

15

decayingradionuclide

ZA , T1/2 T1/2 :- short- medium- long

Z’A’ , T1/2 or stable

decay scheme:- complex - simple

type of decay:- b- : pure or with g-rays- b+ (+ annihilation)- a-decay- electron capture

(X-rays, Auger e-)

g-rayor conversionelectron?

multiple branching?mix of decay types?

solid? volatile? gaseous?

ns level or delayed state?

16

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PERFORMS SIPERFORMS SI--TRACEABLE RADIOACTIVITY MEASUREMENTS TRACEABLE RADIOACTIVITY MEASUREMENTS AT THE HIGHEST LEVEL OF ACCURACYAT THE HIGHEST LEVEL OF ACCURACY

SUPPORTS INTERNATIONAL METROLOGY ORGANISATIONSSUPPORTS INTERNATIONAL METROLOGY ORGANISATIONS

HAS THE HIGHEST NUMBER OF INDEPENDENT HAS THE HIGHEST NUMBER OF INDEPENDENT STANDARDISATION METHODS WORLDSTANDARDISATION METHODS WORLD--WIDEWIDE

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Scale: 0.4 : 1

20.0

0

92.0

0

10.0

0

1.00

51

53

23

41

42

33

46

47

50

45

14.0

0

Ø

28

419.

50425.

50

233.00

238.00Ø

Ø

125.

00

286.

50

Ø

43

44

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27

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36

29

24.0

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18.0

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15.0

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6.50

6.00

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31

32

18.0

0

10.0

0

6.00

5.00

19.00

180.00

40.00

140.00

300.00

108.

00

6.50

84.5

0

15.0

0

17.00Ø

25.00Ø

48

2340

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39

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0

226.

50

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376.00

380.00

PERFORMS SIPERFORMS SI--TRACEABLE RADIOACTIVITY MEASUREMENTS TRACEABLE RADIOACTIVITY MEASUREMENTS AT THE HIGHEST LEVEL OF ACCURACYAT THE HIGHEST LEVEL OF ACCURACY

SUPPORTS INTERNATIONAL METROLOGY ORGANISATIONSSUPPORTS INTERNATIONAL METROLOGY ORGANISATIONS

HAS THE HIGHEST NUMBER OF INDEPENDENT HAS THE HIGHEST NUMBER OF INDEPENDENT STANDARDISATION METHODS WORLDSTANDARDISATION METHODS WORLD--WIDEWIDE

PERFORMS SIPERFORMS SI--TRACEABLE RADIOACTIVITY MEASUREMENTS TRACEABLE RADIOACTIVITY MEASUREMENTS AT THE HIGHEST LEVEL OF ACCURACYAT THE HIGHEST LEVEL OF ACCURACY

SUPPORTS INTERNATIONAL METROLOGY ORGANISATIONSSUPPORTS INTERNATIONAL METROLOGY ORGANISATIONS

HAS THE HIGHEST NUMBER OF INDEPENDENT HAS THE HIGHEST NUMBER OF INDEPENDENT STANDARDISATION METHODS WORLDSTANDARDISATION METHODS WORLD--WIDEWIDE

Primary Standardisation

17

Special Issue on Radionuclide Metrology

Metrologia 44 (2007) S17-S26

18

Special Issue on Uncertainty

Metrologia 52 (2015)

• Detailed uncertainty analysis

for techniques underpinning

SI-unit becquerel

19

'Primary' methods

“Transitions” are measured through the emitted radiation (X, g, a, e-, e+)

Different physical detection principles and devices are used, depending on the radionuclide.

Counting efficiency should be • ≈100% with small corrections

− high-geometry (4p) methods• <100%, but calculated with low uncertainty

− coincidence counting− defined solid angle counting

The ‘ideal’ primary method is accurate, precise, under statistical control, independent of decay scheme parameters and not based on calibrations with other radioactivity standards

20

HIGH EFFICIENCY COUNTING

21

4p-g counting

source

capoptical coupling

lead shield

detector crystal

photo-multiplier

b+

b-

X-raywell-suited forcomplex decaysefficiency ≈ 100%

22

CsI(Tl) sandwich spectrometer

PMtube

Source

CsI

photon, electron, alpha

23

Proportional gas counter

particle emitters(beta, alpha)

24

Fast source drying to reduce

self-absorption in the sources

crystals

25

Liquid Scintillation Spectrometry

0

5000

10000

15000

20000

25000

30000

0 200 400 600 800 1000

Cou

nts

Energy (keV)photo PTB

26

COUNTING AT A DEFINED SMALL SOLID ANGLE

27

Preamp

10 cm

Alpha counting @ defined solid angle

Assumptions :

- one particle is emitted per transition

- emitted isotropically, along straight line

- is counted when reaching detector

- geometry is extremely well defined

Counting efficiency :

- detector efficiency = unity

- geometrical efficiency = solid angle / 4p

28

COINCIDENCE COUNTING

29

11

b

g

beta detector

gamma detector

Measure count rates in each detector along with “coincidence” rate.

Nb = A eb Ng = A egNc = A eb eg

coinc

cNNN

A γβ=

Coincidence counting

30

ppcNaI6”x6”

well

coinc.

*

source

Nc

Ng

Nb

PPC = Pressurised Proportional Counter

Coincidence counting set-up

31

Radionuclides

32

Key comparison Ir-192

five methods!

3333

CONFIDENCE IN MEASUREMENTS®

ISO-FOOD Summer School Radionuclides in food 6th – 10th June 2016, Ljubljana, Slovenia

An introduction to ISO/IEC 17025 standardPolona Vreča

ContentWhat is ISO/IEC 17025?For whom is ISO/IEC 17025 applicable? What for is ISO/IEC 17025 used? What for is ISO/IEC 17025 not used?What is accreditation?What are the requirements of ISO/IEC

17025?

ContentHow to approach in practice? Implementation of ISO/IEC 17025 standard at

the Department of Environmental Sciences

What is ISO/IEC 17025? An international standard »General requirements

for the competence of testing and calibration laboratories«

First edition in 1999, last 2005 with corrections in 2006

Replaced ISO/IEC Guide 25 and EN 45001 Laboratories that comply with ISO/IEC17025 also

operate in accordance with ISO 9001 (but 17025 does NOT replace the 9001)

What is ISO/IEC 17025?A standard that: specifies the general requirements for the

competence to carry out tests and/or calibrations, including sampling,

covers testing and calibration performed using:• standard methods, • non-standard methods, or• laboratory-developed methods.

For whom is ISO/IEC 17025 applicable? All organizations performing tests

and/or calibrations.

All laboratories regardless of: the number of personnel, or the extent of the scope of testing and/or

calibration activities.

For whom is ISO/IEC 17025 applicable? National accreditation

bodies that recognize the competence of testing/calibration laboratories as a basis for accreditation.

What for is ISO/IEC 17025 used? In laboratory to develop a management

system for: quality, administrative and technical operations.

For confirming or recognizing the competence of laboratories by laboratory customers, regulatory authorities and accreditation bodies.

Note: ‘Management system’ means quality, administrative and technical systems that govern the operation of a laboratory.

What for is ISO/IEC 17025 not used?Not used as the basis for certification

of laboratories.

Not covering compliance with regulatory and safety requirements on the operation of laboratories.

What is accreditation?Regulation (EC) No 765/2008 definition:

‘accreditation’ shall mean ‘an attestation by a national accreditation body that a conformity assessment body meets the requirements set by harmonised standards and, where applicable, any additional requirements including those set out in relevant sectoral schemes, to carry out a specific conformity assessment activity’

What is accreditation?A formal recognition that a laboratory is

competent to carry out specific tests or calibrations or types of tests or calibrations.

A process during which an accrediting body reviews and approves a laboratory management system.

Laboratory is accredited for specific test methods or calibrations.

Why is accreditation important?For laboratory as confirmation of good

work.For customer to select appropriate

laboratory with appropriate scope of accreditation.

As formal recognition of results.For international recognition of results.

What are the requirements of ISO/IEC 17025?To define a management

system (implement, perform and maintain MS), appropriate to the scope of activities in the laboratory.

What are the requirements of ISO/IEC 17025?To demonstrate the operation of

management system, to fulfil the: Management requirements Technical requirements

Requirements of 17025 standard

Management requirements

Organization

Review of requests, tenders

& contracts

Document control

Management system

Service for customer

Purchasing services & suppliers

Subcontracting

Requirements of 17025 standard

Technical requirements

Equipment

Personnel

Accommodation & environmental

conditions

Handling with samples

Sampling

Requirements of 17025 standard

Technical requirements

Personnel

Measurement traceability

Test & calibration methods, validation

Quality assurance(CRMs, PTs,…)

Reporting the results

Requirements of 17025 standard

Management requirements

Complains, nonconformities &

improvements

Management reviews

Internal audits

Control of records

Corrective & preventive

actions

Requirements of ISO/IEC 17025Management requirements – primarily

related to the operation and effectiveness of the management system within the laboratory

Technical requirements – include factors which determine the correctness and reliability of the tests and calibrations performed in laboratory

How to approach in practice?Obtaina copy

of standard

Team leader&

Members

(include support of senior management)

ReviewEducationTraining

Preparation steps

DocumentsProcedures

Forms

Quality manual

IdentificationMethods

ScopeImplementation

steps Plan

Write the procedures

How to approach in practice?

17025 implemented

ImprovementCommunication

EducationTraining

ControlAudit

Corrective actions

RecordsImplementation steps

Implement management system(procedures)

How to approach in practice? Perform controls and audits to ensure functioning

of management system.

Examine

Communicate

Follow-up

How to approach in practice?

External audit

Confirmation of MS (accreditation)

Post–accreditation steps

Implementation of ISO/IEC 17025 at the Department of Environmental Sciences (O-2)

2001: beginning of project ʻAccreditation at O-2ʼ 2002–2007: training, meetings, preparation of

documentation, responsibilities 2007:

Identification of 7 methods for accreditation, Final preparation of documentation, Implementation of Management System according

to ISO/IEC 17025 at O-2.

Implementation of ISO/IEC 17025 at O-2 October 2007: Application for accreditation of 7

methods to the Slovenian accreditation (SA). Methods included in the accreditation process

were: Determination of strontium by beta counting

Determination of tritium by liquid scintillation counting

Determination of 14C in alkaline solution

Determining elemental composition of environmental samples using k0-INAA

Determination of mercury in water Determination of elements in water by ICP-MS Determination of organotin compounds in water with gas

chromatography

Implementation of ISO/IEC 17025 at O-2

2008: Initial assessment of SA In June 2009 accreditation according to

SIST EN ISO/IEC 17025 by the Slovenian accreditation (SA),

accreditation certificate LP-090

Implementation of ISO/IEC 17025 at O-2 Since January 2012 only 4 methods are in the

scope of accreditation: Testing fields with reference to the type of test:

• Chemistry • Radiochemistry

Testing fields with reference to the type of test item:• Environment and samples from the environment• Foodstuffs• Feedstuffs• Biological samples

Implementation of ISO/IEC 17025 at O-2 Participation in Slovenian metrology system – cooperation with

Metrology Institute of the Republic of Slovenia (MIRS)

Until 2008 holder of national reference standard in the field of amount of substance: sediment, sewage sludge, soil samples: elements and their species (As, Cd, Co, Cr, Cu, Hg, Ni, Mn, Pb, Zn) VOCs (PAHs, PCBs, flame retardants, PPCP)

Provision of: Traceability to the international level Expert advice through individual training and workshops Organization of proficiency testing Assistance of the accreditation body in the area of the use and

selection of RMs and PTs Participation in international programs/activities

Implementation of ISO/IEC 17025 at O-2 In 2009 confirmation of quality management

system at European Association of National Metrology Institutes Technical Committee for Quality (EURAMET TC-Q)

Implementation of ISO/IEC 17025 at O-2 Cooperation with MIRS as designated institute

Since 2010 holder of national measurement standard in the field of Amount of substance: Soil (including

sediments, soils, ores and particulates)

Since 2015 holder of national measurement standard in the field of Amount of Substance: Trace Elements in

Organic and Inorganic matrices

Possibility to cooperate with: EURAMET and EMRP (European Metrology Research

Programme) Other designated institutes in the metrology system …

2007 vs 2016 Personnel: 16 coworkers 7 methods

Personnel: 7 coworkers 4 methods

2007 vs 2016 Quality manual of O-2 Operational procedures

(14) Standard working

instructions (7) Technical procedures (6) Forms – basic (32) Forms, working books

(no code)

Quality manual of O-2 Operational procedures (11) Standard working instructions

(4 + 3) Technical procedures (14 + 3) Forms – basic (51) Forms, working books (for

accredited methods (73) and other methods (14)

Strengths and opportunities Managing system and constant improvements –

saving funds, new investments Increased confidence in the results – new

possibilities Ensuring the traceability of the measurement

results in time and space – well documented entire process

Formal recognition of competence to perform certain activities – the opportunity to participate in various projects, including national monitorings

…

Weaknesses and threats

Control?

Costs?

Documentation?

…

References ISO/IEC 17025:2005, General requirements for

the competence of testing and calibration laboratories

http://www.iso.org/iso/home.htm REGULATION (EC) no 765/2008 OF THE

EUROPEAN PARLIAMENT AND OF THE COUNCIL of 9 July 2008 setting out the requirements for accreditation and market surveillance relating to the marketing of products and repealing Regulation (EEC) No 339/93

Internet: Google images

More information International Organization for Standardization

(ISO) and the International ElectrotechnicalCommission (IEC)

European accreditation (EA) National accreditation bodies European Association of National Metrology

Institutes (EURAMET) National Metrology Institutes …

Decisions in hands of management!

Success with the support of the entire team!

Practical

gamma-ray

spectrometry

Borut Smodiš

Department of Environmental

Sciences

Reactor Infrastructure Centre

Contents

Properties of radionuclides, gamma-ray

emission

Interactions of gamma emitters with

matter

Detection of gamma emitters, Ge

detectors, gamma-ray spectra

Gamma-spectrometry systems

Practical gamma spectrometric

measurement

Atomic Model

1

100.000

Activity and Decay

Radioactivity: the phenomenon that

unstable nuclides emit, spontaneously,

particles or highly energetic

electromagnetic radiation during their

transition to a more stable state

Synonyms: nuclear mutation, nuclear

decay, nuclear transformation,

disintegration

The nuclide decays to a lower energetic

state

Activity

Activity A of a radioactive substance with N

radioactive atoms is defined as the number

of spontaneous nuclear mutations per

second:

A = – dN/dt

Ionising RadiationIonising radiation Non-ionising

radiation

X-Rays

light

heat

micro-wave

radio-waves

TV-waves

Decay Law

Radioactive decay is a statistical

phenomenon: one cannot predict when a

nucleus will decay.

Half-life: T1/2 is the time in which half of the

number of radioactive nuclei has

decayed.

An instable nuclide can decay in different

ways. Some nuclides decay by one

process, others by multiple processes.

Information on the decay mode can be

found in tabulations and on the chart of

nuclides.

Radioactive Decay Modes

α – particles decay

β- particles decay

β+ particles decay

Electron capture (EC)

y – rays emission

Isomeric transition

Internal conversion

Spontaneous fission

Additional decay processes: X-rays and

Auger electrons

Delayed neutrons

Decay Series

Decay Series

Decay and Types

Decay mode Symbol Ionising radiation Spectrum Other possible

radiation

Competing

decay

-decay 4He-nucleus()

+recoil nucleus

mono-energetic I

--decay

- electron (

-) poly-energetic to

E,max

I

+-decay

+ positron(

+)+2

annihilation quants

poly-energetic to

E,max

I EC

electron-

capture EC, I, X-radiation,

Auger-electron

+

isomeric

transition I, IT -radiation mono-energetic I IC

internal

conversion

IC conversion-electron mono-energetic I, X-radiation,

Auger-electron

I

Spontaneous

fission

SF Daughter atoms +

neutrons

poly-energetic I, -,

Gamma Decay

Upon decay the nucleus will often be left

in an excited state. It quickly releases its

energy in the form of gamma rays

Drops in a sequence of well defined

energy levels

- 100%

γ decay – pure γ-ray emission

Change in the energy level of the nucleus to a lower state, resulting in the emission of γ photon. This can occur following the emission of α or β particle from radioactive decay. When the half-life of the excited state is long enough to be measured (ms or more) the γ decay is described as an isomeric transition (IT).

56

1 37Ba

5 6

13 7Ba

foton

*

γ decay – Internal conversion

(IC)

The excited nucleus deexcites by transferring its energy to an orbital electron, which is then ejected from the atom. No γ ray is emitted. The IC electrons are monoenergetic. As EC decay results in a vacancy in an atomic orbital, the processes of X-ray emission and Auger electron emission will also occur.E* → E + IC electrons + X rays + Auger electrons

γ decay – Pair production (PP)

Energy of the transition is

used to create an

electron-positron pair

and then eject the pair

from the nucleus. The

total kinetic energy

given to the pair is equal

to the difference

between the transition

energy and the 1.02

MeV needed to create

the pair.

Interactions with MatterEnergy absorption of non-charged radiation

(γ and X-rays) in matter comprises:

INTERACTION OF X- AND γ- RAYS

scattering absorption

inelastic scattering

elastic scattering excitation compton effect photo effect pair production

Interactions

with Matter

Scattering and

Absorption

only absorption

only scattering

scattering plus absorption

Photoelectric Effect

elektrone

vpadni

foton

-

incident photon γ

electron

Compton Scaterring

comptonskielektron

sipanikvant

vpadni

kvant

e-

incident photon γ

scatteredphoton γ

comptonelectron

Pair Production

e-

e+

vpadni foton incident photon γ

Interactions with Matter Photoelectric effect is dominant

process at low energies and

high Z

Compton scattering is

dominant process at

intermediate photon energies,

in particular at low Z

Pair production requires high

energy photons (> 1.02 MeV)

Specific Interactions of

Photons with Ge Detector Photoelectric absorption

Pair production/annihilation

Compton effect

Escape effect

Single escape phenomenon

Double escape

phenomenon

Compton effect:

backscattering with loss of

diffused photon

External Compton effect:

detection of diffused photon

External Compton effect:

backscattering

Compton effect with partial

recovery of the full energy

X-fluorescence of the

surrounding walls

Detection of the electrons

emitted by the source

Detection of the 511 keV

radiation: pair production

inside the protection housing

(if Eγ > 1022keV)

Influence of Surrounding

materials to Detector Response

Shape of the 137Cs γ-ray

Spectrum

Shape of the 60Co γ-ray

Spectrum with All Interactions

Closed-End Coaxial Ge

Detector

p–type Gen – contact (~300 m)

Closed-End Coaxial Germanium Detector

Closed-End Coaxial Ge

Detector

n–type Ge

n - contact

Closed-End Coaxial Germanium Detector

p – contact (~0.3 m)

Open-End Coaxial Ge

Detector

p–type Ge

n - contact

Open-End Coaxial Germanium Detector

Well Ge Detector

n – contact (~300 m)

Well Germanium Detector

Source

p–type Ge

Different types of Ge detectors

Decisions for Choosing of

Detector

Money

Energy range

Efficiency and resolution needs

Operating environment

Field vs. Laboratory

Neutron radiation field

Turn around time

Number of samples

Serviceability

Decisions for Choosing of

Detector

~80 keV – 3 MeV: P-type coaxial detector

10 keV – 3 MeV: N-type beryllium or

carbon fiber window

Carbon fiber has 70% transmission at 10

keV

Beryllium has 23% higher transmission at 10

keV, but is toxic and fragile

Decisions for Choosing of

Detector

Map out your needs

Low energy

High energy

All energies

Shielding of natural occuring radioactivity

Types of samples

Simple or complex spectra

High resolution 1.85 keV FWHM or better

Block Diagram of

Conventional γ- Spectrometry

System

More Electronic

Manipulations

Digital Signal Processing: One

Big BLACK Box

Digital Signal Processing:

What is it?

Digital signal processing (DSP) is the

mathematical manipulation of an

information signal to modify or improve it

in some way. It is characterized by the

representation of discrete time, discrete

frequency, or other discrete domain

signals by a sequence of numbers or

symbols and the processing of these

signals (wikipedia)

DSP vs Analog

Better temperature stability because, once the pulseis digitised, all of the subsequent operations are temperature independent.

Higher throughput, because the digitisation andfiltering processes can be made faster than thealternative conventional ADC systems.

Improved resolution stability at high count rates.

Analog systems are notorious for degraded resolutionat high count rates.

Digital systems offer much less resolution loss.

Improved peak position stability. There is much lesspeak shift as count rate is increased in a digitalsystem than in an analogue one.

Detection of Radiation

Operating characteristics of detectors:

Efficiency (ε): number of radiations

actually detected out of the number

emitted by the source.

Energy resolution (R): ability of the

detector to discriminate two radiations of

different energies.

Dead time or resolving time (τ): amount of

time needed before a detector can

recover from one incoming radiation and

respond to the next.

Practical γ-ray Spectrometry

Sample preparation:

Representative

Homogeneous

Appropriate geometry for the selected

detector

Practical γ-ray Spectrometry

Detector energy calibration:

By measurement of a set of radionuclides

with known γ-lines. Then, an energy

calibration curve relating the energy E to

the analyser channel C can be represented

by a simple polynomial form:

E = a0 + a1C + a2C2

Where a0, a1 and a2 are parameters

determined by a numerical fit to the data.

Practical γ-ray Spectrometry

Full-energy photopeak efficiency curve (εp):

Using calibrated sources with known γ-ray emissionrates and activity values, metrologically traceableto Bq. The curve is more difficult to construct andthere are several ways for doing it:

Single γ-ray emitting radionuclides;

Point sources;

Extended sources

Problem: corrections are needed for truecoincidence effects. This requires insight in thefraction of the emitted photons ending in thephotopeak and the fraction ending by scatteringin the rest of the spectrum: the peak-to-total (p/T) curve.

Practical γ-ray Spectrometry

Full-energy photopeak efficiency curve (εp):

One source:

Advantage: simple;

Dissadvantage: do not always fully cover entire

energy range; inter/extrapolation disputable in 80 –

150 keV range.

Multiple (3 – 5) sources:

Advantage: better coverage of all energy ranges;

Disadvantage: more cumbersome, problems with

non-matching parts.

Practical γ-ray Spectrometry

Full-energy photopeak efficiency curve (εp):

Measure the detector‘s response using one or

more sources emitting multiple γ-rays and of

which the relative intensity ratios are well known.

Several sources can be used to measure the

response at different ranges of the energy interval.

Merge the shapes of these individual response

functions into one curve, scaled at an arbitrary

point to an arbitrary value.

Practical γ-ray Spectrometry

Full-energy photopeak efficiency curve (εp);

an example:Point sources at reference distance (20 cm): 241Am, 133Ba, 207Bi, 109Cd, 57Co, 60Co, 51Cr, 137Cs, 152Eu, 54Mn, 22Na, 226Ra, 85Sr. Fitting curve:

nnp EaEaEaEaa log...loglogloglog 33

2210

Practical γ-ray Spectrometry

Full-energy photopeak efficiency curve (εp):

The most simple approach is to use a homogeneous spiked standard of the same geometry and similar density as the sample.

standard sample

Practical γ-ray Spectrometry

Full-energy photopeak efficiency curve (εp):

Modelling:

Requires details on the construction of the detectorand cryostat;

Weakest link: estimation of the dead layer in the Gedetector;

Commercially available software available forestimation of detector photopeak efficiency;

Detector must be pre-calibrated at and by thedetector manufacturer immediately followingmanufacturing.

Practical γ-ray Spectrometry

Coincidence effects:

They occur when counting radionuclides

decaying by γ-rays in cascade and by detector

systems with relatively high photoopeak

efficiency.

Corrections are required for high accuracy

measurements at the metrological level, for

radionuclide activity determination and

measurement of photon emission intensities;

They should also be taken into account in low-

level measurements due to the close source-

detector geometry;

Summing-out, summing-in vs. Random summing.

Practical γ-ray Spectrometry

Coincidence effects:

Ample routines have been developed forsoftware corrections. Some may be commerciallyavailable; see, e.g., T. Vidmar et al., Appl. Radiat. Isotop. 87 (2014) 336-341;

Measurement of the p/T curve using e.g. 65Zn or137Cs:

Measure the background spectrum: estimate thetotal No. Of counts between e.g. 100 keV and 2 MeV: N(t)b;

Measur the source. Estimate the total No. Of countsbetween 100 keV and 2 Mev: N(t)s;

Estimate the net peak area of e.g. 662 keV γ-ray: N(662)s;

Calculate the p/T ratio for the 662 keV photons:

p/T (662) = N(662)s – (N(t)s – N(t)b)

Practical γ-ray Spectrometry

Self-attenuation:

Photons with low or moderate energy which are in

the matrix that has a significant amount of high-Z

material and/or an appreciable amount of mass

can be severely attenuated;

This can lead to serious underestimating the

activity concentrations of the radionuclide to be

determined in a sample.

Practical γ-ray Spectrometry

Experimental evaluation of self-attenuation:

Fill a container of the sample to be evaluated;

Choose an appropriate point source for determining

self attenuation coefficients. A good source will contain

a spectrum of strong γ-ray emissions across a wide

energy range;

Sources such as 152Eu can meet this requirement.

However, have in mind that the low energy regime is

the region of greatest change in the self-attenuation;

Place source(s) on top of the sample container. Count

for backgrount, sample-detector, sample-source-

detector and source-detector for a container.

The geometric positioning should remain unchanged

between the counting of the filled and empzy

containers.

Practical γ-ray Spectrometry

Experimental evaluation of self-attenuation:

A total of 4 spectra are required to calculate the

self-attenuation correction factor: (1) sample

material, (2) point source mounted on top of a

container with a sample, (3) point source

mounted on top of the empty container, (4)

background with an empty container and no

point source;

The final result are correction factors distributed

across the energies of the peaks;

Practical γ-ray Spectrometry

Experimental evaluation of self-attenuation:

There are also other methodologies for calculating

self-attenuation factors.

0

0,2

0,4

0,6

0,8

1

1,2

-400 100 600 1100 1600

1/F

att

E (keV)

Practical γ-ray Spectrometry

Measurement: typically one or more days;

„spectrum accumulation“;

Spectrum analysis;

Calculation of activity concentrations.

Practical γ-ray Spectrometry

Spectrum analysis: Identification of

characteristic photopeaks (by using

radionuclide libraries and decay schemes) and

determination of peak areas.

Practical γ-ray Spectrometry

Thank you for your attention!

Joint Research Centrethe European Commission's

in-house science service

Statistics &

Uncertainty

Stefaan Pommé

2

Slides 3 to end are the intellectual property of Stefaan Pommé (European Commission, Joint

Research Centre)

“Unauthorised reproduction constitutes a copyright infringement and may lead to

prosecution or civil proceedings“

Copyright notice

Definitions

MeasurandError

UncertaintyAccuracy

4

The quantity that we measure

= the MEASURAND

• Important to

• - define accurately measurand + unit

• e.g. Activity of Co-60 in a sample expressed in Bq

• - use appropriate method traceable to unit

• e.g. HPGe detector calibrated with standard sources

Measurand

5

The difference between the

value of the measurand (true value)

and the measurement result

= the ERROR

• - the error cannot be known exactly

• - random and systematic errors occur

Error

6

The estimated dispersion of the values

attributed to the measurand (due to

potential errors in the measurement)

= the UNCERTAINTY

• - good metrology requires realistic uncertainty analysis that cover all sources of error

• - standard uncertainty = expressed as standard deviation

Uncertainty

7

Measure of random uncertainty

= PRECISION

Measure of systematic bias

= TRUENESS

Accuracy

8

finding an accurate estimate of the measurand

identifying / quantifying all sources of uncertainty

provide safe confidence intervals for the value

The challenges of metrology

9

Unawareness of Bias=> Underestimation of Uncertainty

solutions:

- better understanding of measurement= 'metrology'

- compare with complementary methods= 'redundancy'

Reference value

bias

Remedies against errors?

10 Metrologia 52 (2015)

• Detailed uncertainty analysis

for techniques underpinning

SI-unit becquerel

Special Issue on Uncertainty

Convenient properties

Standard uncertainty

12

dark shade = xi ± ui

xi xi xi

• A measure for the width of the probability distribution

Definition: standard deviation

13

What is the standard uncertainty for data of

which upper and lower limits of the error

are stated ±a without confidence level?

All values equally possible: rectangular

Extreme values less possible: triangular

Distribution DivisorRectangular s = a / √3Triangular s = a / √6Normal (k=2) s = U / 2

Divisors

14

Expanded uncertainty U=ku, with coverage factor k (CL=p)

To express a statement of confidence

Normal distribution: Probability that true value Y=y±U is 95% (k≈2) or 99% (k≈3)

What if not Normal? t-distribution

Expanded uncertainty

Convenient use of standard deviation

Uncertainty propagation

16

Uncertainty propagation from x to y

Partial derivatives of f with respect to Xi at Xi=xi, ∂f/∂xi, also called sensitivity coefficients ci. How would y be influenced by small changes in xi ?

ciu(xi) useful to assess contributions from input quantities to uc(y) .

u(xi) is standard uncertainty associated with xi

u(xi, xj) is estimated covariance associated with xi and xj

)x,x(ux

f

x

f2)x(u

x

f)y(u ji

j

1N

1i

N

1ij ii

2

2N

1i i

2c

functional dependence y=f(x)

17

)()(

)()(

0)(

XccX

XcX

c

ss

ss

s

• => no uncertainty

• => no added uncertainty

• => same relative uncertainty

Propagation of constant c

18

Sum of independent variables X and Y

=> quadratic(!) sum

sum of 'variances'

Typically dominated by the largest uncertainty!

)()()( 222 YXYX sss

0),COV( YX

Propagation of a sum

19

Sum of two dependent variables X and Y

=> covariance

Difference of X and Y

),(2)()()( 2222 YXYXYX ssss

)(E)(E)(E),COV(),(

)(E)(E)(ARV)(

2

222

YXXYYXYX

XXXX

s

s

),(2)()()( 2222 YXYXYX ssss

Propagation of a sum

20

Linear combinations

Arithmetic mean of independent samples of X

ji

jijii

iii

ii XXaaXaXa ),(2)()( 2222 sss

n

XX

)()(

ss

)(1

)(1

)( 22

2

2 XN

XNN

X

i

ii

i

sss

assuming uncorrelated uncertainties

Uncertainty of a mean

21

However, attention if uncertainty is caused by a

'systematic' effect => all X-values correlated

• Uncorrelated uncertainties:(uncertainty due to 'random' error)

• Fully correlated uncertainties: (uncertainty due to 'systematic' error)

n

XX

)()(

ss

)()( XX ss

Uncertainty of a mean

22

Product of two variables X and Y

Multiplication/ division:

use relative standard uncertainty

)E()E(

),(2

)(E

)(

)(E

)(

)(E

)( 2

2

2

2

2

2

2

YX

YX

Y

Y

X

X

XY

XY ssss

Propagation of a product

23

Ratio of a constant c and variables X and Y

division => minus covariance

constant does not change relative uncertainty

relative uncertainty independent of units

Propagation of division

)E()E(

),(2

)(E

)(

)(E

)(

)/(E

)/( 2

2

2

2

2

2

2

YX

YX

Y

Y

X

X

YcX

YcX ssss

24

All these propagation properties of the

standard uncertainty

are independent of the statistical distributionsof the variables

are independent of our knowledge of these distributions

make our results directly usable by others

= Mega-Super-Cool

IMPORTANT ADVANTAGES

25

How many digits are significant?

Rounding of numbers

26

d = 50 m

d = 50 m ± 0.3 m

d = 50.123456 m ± 0.12 m

d = 50 m ± 10 cm

d = 50.123456 m ± 0.123456 m

Does this make sense?

27

An experiment is repeated n times. The data are normally

distributed with a standard deviation s. The corresponding

variance of a sample standard deviation is s2/2n.

Calculate the relative variation of the sample standard deviation;

this is the ratio of its standard error to its mean:

n2

1

n2

2

ss

Uncertainty on uncertainty

28

n2

1

n2

2

ss

Use this equation to decide on the number of significant digits

in the following examples and round the result properly:

Mean st dev mean n unc. on unc. unc result

1.1934 0.0245 8 25% 0.03 1.19

1100.4 123.12 50 10% 0.13 E3 1.10 E3

523.45 9.9123 5000 1% 10.0 523.5

Rounding

29

Assuming (at least) 10% uncertainty on the uncertainty, mention only 1 digit, ormaxium 2 digits for small numbers

1, 10, 11, 12, …192, 20, 21, 22, … 2634…9

Rounding should be performed only at the very end of the process (to avoid rounding errors)The final uncertainty is preferably rounded up.

1 or 2 digits

1 digit

Rounding: rule of thumb

30

d = 12.3456 m ± 0.03923 m 12.35 (4) m

t = 0.023456 s ± 1.622 10-3 s 23.5 (17) 10-3 s0.0235 (17) s23.5 (17) ms

m = 7.35 1022 kg ± 2.7 1020 kg 7.35 (3) 1022 kg

Examples

3131

Results expressed in SI-units, rounded to the right

significant number.

Uncertainty expressed as standard uncertainty or

expanded uncertainty with level of confidence.

Conclusions

Radiochemical analytical techniquesLjudmila BenedikBorut SmodišMarko ŠtrokMiha Trdin

Determination of radionuclides

Determination of radionuclides may be

performed by two approaches:

Radiometric measurement

(characteristic radiation)

Mass measurement

(number of atoms)

Radiometric measurement

Gamma-ray spectrometry

Beta counting

Alpha-particle spectrometry

Liquid scintillation technique

Mass measurement

ICP-MS (inductively coupled plasma MS)

AMS (accelerator mas spectrometry)

TIMS (thermal ionisation MS)

RIMS (resonance ionisation MS)

SIMS (secondary ion MS)

NAA (neutron activation Analysis)

INAA (Instrumental NAA)

RNAA (radiochemical NAA)

Radiochemical analysis

Radiochemistry

= the chemistry of radioactive substance(s)

= separation of radionuclide(s)

Radiochemistry

Isolation of the analysed radionuclide

chemically and radiochemically from the

sample and its components

The radionuclide of interest is isolated in high

yield and with high purity

The radionuclide of interest should be

detected with as high efficiency as possible,

considering also background

Procedure should be applicable to a vide

range of material types and radionuclides

concentrations

Radiochemical procedures

Pre-treatment

to remove organic constituents and convert

samples into inorganic form

dry ashing (300 – 650 °C) – loses

Radiochemical procedures

Solubilisation

a) wet ashing (mineral acids + oxidants)

Total dissolution: treatment with mineral acids

(e.g. HNO3, HClO4, HF; H2SO4, HCl)

Radiochemical procedures

Solubilization

Total dissolution:

b) fusion with a suitable flux

c) Microwave oven

Radiochemical procedures

Leaching

Removal of materials by dissolution or desorption from solids sample and its components

wetting by intrusion of the leaching solution into the pores

the dissolution of trace constituents from the solid into the pore solution

outward diffusion

Radiochemical procedures

Separation and pre-concentration

Utilize the differences between the distribution

coefficients of the individual constituents of a

mixture between two phases

Macro-micro: major constituent isolated, tracers

remain in the solution

Micro-macro: trace constituent isolated, major

constituents retained in the solution

Micro-micro: trace constituents separated from

one another after isolation

Radiochemical procedures

Precipitation

Formation of a separable solid substance

from a solution

Crystalline precipitate (nucleation, crystal

growth, aging)

Colloidal precipitate: continuous transition

from molecular particles to macroscopic

aggregates

Radiochemical procedures

Volatilisation

Matrix of trace constituents are

separated, depending on which is more

volatile.

Direct distillation of one ore more trace

constituents from the sample

Conversion of the sample constituents into

chemical species that can be separated

by virtue of the difference in their volatilities

Radiochemical procedures

Liquid-liquid extraction

Process of transferring a chemical

compound from one liquid phase to a

second liquid phase, immiscible with the

firs one.

One phase is usually water and the other a

suitable organic solvent

Radiochemical procedures

Ion exchange chromatography

Ion–exchangers are insoluble solid materials, which contain exchangeable cations or anions

Ionic substances are separated on cationic or anionic sites of the material Charged substances are separated via column

materials that carry an opposite charge

The sample ion is exchanged with ions already on the inorganic group of the material

Radiochemical procedures

Extraction chromatography

Stationary phase is an extractant, which coats or is bonded to a porous hydrophobic support, and the mobile phase is a suitable solution of an acid, base or salt.

As stationary phase supports are silica gel, Teflon, etc

The most used extractants are TBP, TOPO, MIBK, etc

Alpha-particle decay

QNN

22

42

22

4A2Z

AZ HeFE

Q 242

223490

23892 HeThU

Alpha-particle decay

Energy of alpha particles (MeV)

Num

ber o

f alp

ha p

artic

les

QNN

22

42

22

4A2Z

AZ HeFE

Alpha particleshave definedenergies

Alpha-particle decay - Th-230

Energy (keV)

Intensity (%)

3829.4 17 1.40E-6 % 14

3877.8 16 3.4E-6 % 3

4248.5 16 1.03E-5 % 22

4278.3 17 8.0E-6 % 20

4371.8 16 9.7E-4 % 13

4438.4 16 0.030 % 15

4479.8 16 0.120 % 12

4620.5 15 23.40 % 10

4687.0 15 76.3 % 3

α242138

22688140

23090 QHeRaTh

Alpha particle spectrometer

242He

• A very large mass

• A high charge

• -particles are easily stopped by a few microns of air.

• A very thin source allows adequate transmission of the -particles to the detector surface

Actinides

All members of the serie resemble actinium in their

chemical and electronic properties

All actinides are radioactive heavy metals

Actinides can exist in many different oxidation

states

89Ac

90Th

91Pa

92U

93Np

94Pu

95Am

96Cm

97Bk

98Cf

99Es

100Fm

101Md

102No

103Lr

Actinides

Th Pa U Np Pu Am Cm

III III III III III III III

IV IV IV IV IV IV IV

V V V V V

VI VI VI VI

VII VII

• The knowledge of the chemical behavior o theactinides in aqueous solution is essential duringthe development of analytical procedure for theirdetermination from complex matrix

Important

the main alpha lines of natural and man-made radionuclides as well as the tracers used lie in the range from 4000 to 6000 keV

insufficient separation leads to spectral overlap of the alpha energies of these radioisotopes and incorrect results obtained

Remeasurement after certain time is incorrect due to decay or ingrowthproducts from alpha sources

Alpha-particle spectra

Typical spectra

Po-209

Po-210

Ra-226

U-238

U-234

U-232

Pu-242

Pu-239+240

Pu-238

Separations

Alpha emitters

Uranium solvent extraction by TBP in toluene

extraction chromatography

Thorium solvent extraction by TOPO in toluene

extraction chromatography

Radium Precipitation as Ba(Ra) sulphate

Polonium extraction chromatography

Separations

Alpha emitters

Plutonium ion-exchange chromatography

extraction chromatography

Americium ion-exchange chromatography

extraction chromatography

Beta decay

19039

9038 eYSr Q

2Q eFeCo 5826

5827

e– electronantineutrino

e+ positronneutrino

Q1, Q2 released energy keV

Important

the main beta emissions occur between 0 and

2400 keV.

insufficient separation leads to spectral overlap

of the beta energies of these radioisotopes and

incorrect results obtained

Contaminants are harder to detect when

compared to the alpha-particle spectrometry

(non-discrete energies of beta particles)

Beta counting

Gas-flow proportional counter

No spectra

RADIOCHEMICAL SEPARATION IS ESSENTIAL

Beta spectra (liquid

scintillation technique)

0

5

10

15

20

25

30

35

40

45

50

0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400

K-40

Sr-89

Sr-90

Y-90

Cs-137

Bi-210

Ac-228

Beta spectrum (Sr-90)

0

10

20

30

40

50

60

0 200 400 600

rela

tive b

eta

in

ten

sit

y

energy (keV)

Nuclide

βmax

keV

βavgkeV

t1/2 decay source

H-3 19 6 12,3 a β–Interaction of cosmic rays with atmosphere

C-14 156 50 5730 a β–Interaction of cosmic rays with atmosphere

K-40 1 312 455 1,277*109 aβ–,

β+ (10 %)Natural

Sr-89 1 492 583 50,6 d β– Fission

Sr-90 546 196 28,5 a β– Fission

Y-90 2 282 934 2,7 d β– Daughter of 90Sr

Cs-137 1 175 188 30 a β– Fission

Pb-210 63 7 22,3 aβ–,

α (2*10-6 %)Member of U decay chain

Bi-210 1 162 389 5 dβ–,

α (1*10-4 %)Member of U decay chain

Ra-228 46 — 5,8 a β– Member of Th decay chain

Ac-228 2 142 391 6 hβ–,

α (6*10-6 %)Member of Th decaychain

Beta emitters

Separations

Beta emitters

Sr-90 leaching,

selective precipitation

Pb-210 Extraction Chromatography by Sr resin

Ra-228 Extraction chromatography by LN resin

Gamma-ray spectrometry

Gama-ray measurements can be done

“without” the radiochemical separation

or tracer(s) addition

standard sample

Gamma-ray spectrum

Determination of uranium by

RNAA

238U(n,) 239U (t1/2 = 23.5 min) 239Np

Irradiated sample + 50 mg U carrier + (3 ml 9 M H2SO4) in 100 ml quartz Kjeldahl flask

Wet ashing with HNO3 over gas flame, then HClO4

Transfer to separatory funnel with 20 ml 5M HNO3

Extract U with 5 mL 50 % TBP in toluene, clean up org. phase 2x with 5 mL 5M HNO3/0.2 % HF

Pipete 5 mL org. phase into 6 mL measuring vial and measureon Ge well-type detector

Gamma-ray spectrum after

radiochemical separation

Treatment of the sample from Sampling to MeasurementMiha Trdin

Knowhow Liquid or solid (soil, food,…)

Sampling

Decomposition

Pre-concentration

Radiochemical separation

Source preparation

http://wallpapersclub.org/246/img/453/air-earth-fire-water-elements.html

Knowhow Gamma-ray spectrometry

Alpha-particle spectrometry

Liquid scintillation technique

Beta counting

Radiochemical neutron activation analysis

SAMPLING

SamplingSampling and sample preparation are two essential steps

They are ALWAYS a part of an analytical process

Sampling – process obtaining a sample

Sample – a portion of material selected from a largerquantity of material

Sample preparation – sample must be prepared foranalysis in the laboratory

The preparation of a sample for analysis must be done very carefully in order to make accurate and precise

analysis / measurement

Sampling process

SAMPLING SAMPLE

RESULT

Responsibility for the sampling (laboratories mostly take responsibility only for the analysis)

Sample preparation must be done accordingly to the requested analysis

Follow the instructon for use radioactive substances

SAMPLE PREPARATION

MEASUREMENT

Sampling Liquid samples

Type of a sample Representative sample

Collection of the grosssamples

Reduction of samples Handling of the sample Filtration Preservation and storage of

samples

Solid samples

Drying, sieving... Homogenization... Reduction, (sub sample

must be homogenous)

Sample preparation must be done accordingly to the requested analysis

Sampling StrategyProcess obtaining a sample – strategy:

Location Quantity of sample Techniques for sample collection Sampling equipment Sample containers Labeling of an individual sample Transportation to the lab ……….

Sampling Standards International

ISO, CEN, ANSI, ASTM,..

National SIST (SI), ON (AT), DIN (DE), ...

Standard cover fields and subfields

Water drinking waterwaste waterenvironmental water

Meant to ensure the comparability of the results obtained after the analysis

Sampling- food

Not all food can be sampled in the same manner Sampling certain food requires specialized equipment (e.g. round cheese)

Storage and transport are important E.g. Fish, mussel, fruit,..

Some samples need to be analyzed “almost immediately” after sampling

E.g. Activity of 210Po (t1/2 = 138.3763(17)days) or 131I (t1/2 = 8.0233(19) days),

Samples must be representative Homogenization Time of sampling Location External contamination (example cabbage)

Sample preparation must be done accordingly to the requested analysis

Example: sampling of cabbage

Example: sampling of cabbage

Samples were collected at the appropriate time

The date and location (GPS) were noted

A reference sample was collected outside the investigated area

For a single sample several plants were collected on several locations of the same field (representative sample)

The outer leaves and roots were removed and each plant was washed to remove external contamination

The plant was cut to 4 parts, 2 parts were kept while 2 were discarded

The parts were dried at 60°C for 4 days.

The plant parts from the same field were combined and grinded in agate mill (avoid contamination)

Sampling- ISO 5567 Water Quality

10 main parts

Guidance on the design of sampling programmes Guidance on the design of sampling programmes and sampling techniques

Guidance on sampling techniques

Guidance on the preservation and handling of water samples

Guidance on sampling from lakes, natural and man-made

Guidance on sampling of drinking water and water used for food and beverage processing Guidance on sampling of drinking water from treatment works and piped distributed systems

Guidance on sampling of rivers and streams

Guidance on sampling of rivers and stream in boiler plants

Guidance on the sampling of wet deposition

Guidance on sampling from marine waters

Guidance on sampling of waste waters

Sampling- ISO 5567 Water Quality

10 additional parts

Guidance on sampling of groundwaters

Guidance on sampling on botton sediments

Guidance on sampling of sludges from sewage and water-treatments works

Guidance on quality assurance of environmental water sampling and handling

Guidance on preservation and handling of sludge and sediment samples Guidance on preservation and handling of sludge and sediment samples

Guidance on biotesting of samples

Guidance on sampling of suspected sediments Guidance on sampling of suspected sediments

Guidance on sampling of groundwater at contaminated sites

Sample is obtained..

WHAT NOW?

Sample preparation (storage)

Liquid samples

Acidification

Addition of a tracer

Solid samples

Lyophilisation

Drying

Addition of a tracer

Good sampling and sample preparation is thebasis of good data !

Tracer(s) An artificial radioisotope of the element of interest

e.g.: 232U for determination of 234U, 235U and 238U229Th, 210Po, 242Pu, 243Am

Stable isotope(s) of the element of intereste.g.: stable isotopes of Pb for determination of 210Pb

Strontium

Radioisotope with the same radiochemical properties as the element of intereste.g.: 133Ba for determination of 226Ra and 228Ra

Lyophilisation (aka. Freeze-drying)

…dehydration process typically used to preserve a perishable material or make the material more convenient for

transport or analysis.

Volatile elements (nuclides) and compounds remain in the sample

Almost no damage to organic material in the sample

Gama-ray measurements can

be done “without” the

radiochemical separation

or tracer(s) addition

Preparation for gamma measurement

Liquid samples

The sample is evaporated or the radionuclides are precipitated

The dry residue is weighted in a plastic container and SEALED

Solid samples

The sample is weighted in a plastic container and SEALED

The measurements can commence

What about alpha-particle

spectrometry?

Preparation for alpha-particle spectrometry and betta counting

Radiochemical separation is ESSENTIAL

Ion exchange and extraction chromatography

Thin-layer sources are required

Good sampling and sample preparation is thebasis of good data !

Preconcentration

Preconcentration Liquid samples

(Co)Precipitation Evaporation

Solid samples

Ashing (not always sensible)

https://www.pinterest.com/pin/389139224023272957/

http://www.imaginelifestyles.com/luxuryliving/2013/12/images-of-exploding-cars

(Co)PrecepitationAs Fe(OH)3Add FeCl3 and ammonia (actinides)

As MnO2Add KMnO4, MnCl2 and ammonia (actinides)

As Ca3(PO4)2Add Ca(NO3)2 (NH4)2HPO4 and ammonia (actinides)

As Pb(SO4)Add Pb2+ and H2SO4(Radium)

As Ba(SO4)Add Ba2+ and H2SO4(Radium)

ALWAYS USE THE PRECIPITATION METHOD MOST SUITABLE FOR THE FOLLOWING RADIOCHEMICAL SEPARATION

TECHNIQUE

Evaporation

Lengthy procedure

No analyte loss

Temperature of evaporation is important

http://www3.pittsfield.net/groups/tamalasebring/weblog/8e254/images/f8283.jpg

Ashing

Reduces the sample

Ceramic crucibles

Temperatures up to 700ºC

Not appropriate for activity concentration determination of volatile radionuclides!!!

DECOMPOSITION

Decomposition of solid samples

ESSENTIAL for radiochemical separation of radionuclides

In most cases lengthy procedure

Several methods, each with its own advantages and disadvantages

IF SOLID RESIDUE REMAINS IN A BAKER OR CRUCIBLE AFTER DECOMPOSITION

RADIUNUCLIDES CAN BE ACOMULATED IN IT(Especially thorium and uranium radioisotopes)

Decomposition (methods)

Classical digestion by mineral acidsHNO3, HF, HCl and HClO4

Microwave digestionHNO3 and HF

Thermal fusionperoxide fusion, lithium borates fusion, Lithium metaborates fusion,….

Classical digestion by mineral acids

ADVANTAGES

Simple

Allows larges quantities of sample

Ashing is not required

DISADVANTAGES

Lengthy

HF

There is always some solid residue left

Microwave digestion

ADVANTAGES

Fast

Simple

DISADVANTAGES

HF

Ashing is required

Allows smaller quantities of sample

There is always some solid residue left

Thermal fusion

ADVANTAGES

Ultra fast

There is no solid residue left

No HF

DISADVANTAGES

Ashing is required to reduce the sample size

Allows smaller quantities of sample

High temperatures(Do not use for activity concentration determination of volatile radionuclides)

Radiochemical separation

Radiochemical separationExtraction chromatography

Ion-exchange chromatography

Liquid-liquid extraction

UTEVA TEVA Sr resin Pb resin

http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_006f/0901b8038006f232.pdf?filepath=liquidseps/pdfs/noreg/177-01509.pdf&fromPage=GetDochttp://www.eichrom.com/products/info/uteva_resin.aspxhttp://www.eichrom.com/products/info/teva_resin.aspxhttp://www.eichrom.com/products/info/sr_resin.aspxhttp://www.eichrom.com/products/info/pb_resin.aspx

Dovex 1x8

Toluene

But how does the

radiochemical separation

looks like?

Radiochemical separation(example)

Sample + U-232 + Th-229 + Pu-242 + Am-243

- Dissolve precipitate in 2M HNO3

- Adjust the oxidation stage:

ascorbic acid, NH2OHHCl, NaNO2

- Add conc. HNO3 → 8M HNO3

- Load sample on Dowex 1x8, 100-200 mesh in 8M HNO3

Radiochemical separation(example)

U+Th+Pu+Am

Loading on Dowex 1x8, 100-200 mesh in 8M HNO3

Eluate(U, Am)

UTEVA -U

TRU - Am

Column(Th, Pu)

Elution of Th with 9M HCl

Elution of Pu with 0.1M NH4I/9M HCl

Source preparation:Coprecipitation with NdF3 / electrodeposition

Radiochemical separation(example)Add NH4OH and precipitate radionuclidesDissolve precipitate in 2M HNO3

Wash with 2M HNO3

UTEVA UTEVA: wash with 9M HCl, 5M HCL/0.05M Oxelute U with 1M HCl

TRU: wash with 2M HNO3 + 0.1M NaNO2TRU

Elute Am with 9M HCl and 4M HCl

Source preparationCoprecipitation with NdF3 / electrodeposition

Radiochemical separation(example)

Liquid – liquid extraction

Fast!

Especially useful in case of radiochemical neutron activation analysis (for example uranium)

Source preparation

Source preparation Micro(co)precipitation

Electrodeposition

Spontaneous deposition

Micro(co)precipitation As barium sulfate (Ra)

As neodymium fluoride (U, Pu, Am, Np, Th,…)

Elrctrodeposition Electrolyte

Time needed: 1-4h

I = 1A

Spontaneous deposition (Polonium)

Silver discs

HCl

Ascorbic acid

Beta counting and liquid

scintillation technique

Beta counting Radiochemical separation is again ESSENTIAL

We can only count (no spectra are available)

Radionuclide of interest is extracted from thesolution by (co)precipitation. The precipitate is then loaded on a planchette by centrifuging

Liquid scintillation technique Radiochemical separation is again ESSENTIAL Result of analysis is a spectra

Radionuclide of interest is after radiochemical separation collected in a glass or plastic vial to which a cocktail is added

Measurement can be performed without adding cocktail if energies are high enough that “Cherenko” radiation can be detected

*cocktail: solvent (historically aromatic organics such as benzene or toluene, but more recently less hazardous solvents are used), typically some form of a surfactant, and small amounts of other additives known as "fluors" or scintillators

Cocktail (solvent,surfactant and

scintillator)

PhotonsPMT SignalSample

β-, α

+ =

Liquid scintillation technique

What about radiochemical

neutron activation analysis?

Radiochemical neutron activation analysis

ADVANTAGES

Low detection limit

DISADVANTAGES

You need a nuclear reactor

Radiation

Mass determination method

Radiochemical neutron activation analysis(example)

Determination of uranium content

Samples are weighted in a small plastic container and sealed

Solution of natural uranium used as reference for mass determination is sealed in a second plastic container

Both containers are put in a plastic tube, closed and irradiated in TrigaMK II reactor for 3-10 minutes at 250 kW

Decomposition of the sample is made in kjeldahl flask to which natural uranium is added to determine the recovery of the radiochemical procedure

Sulfuric and nitric acid are used to decompose the sample

Dry residue is dissolved in nitric acid

Radionuclides are extracted by liquid-liquid extraction to toluen

The sample is then collected in a glass container and measured on a gamma spectrometer

To determine the mass concentration an irradiated standard is used as a reference

Joint Research Centrethe European Commission's

in-house science service

Gamma-ray

spectrometry

Stefaan Pommé

2

Slides 3 to end are the intellectual property of Stefaan Pommé (European Commission, Joint

Research Centre)

“Unauthorised reproduction constitutes a copyright infringement and may lead to

prosecution or civil proceedings“

Copyright notice

3

Review paper

Metrologia 52 (2015) S123

4

Why gamma-ray spectrometry?

• Easy sample preparation

• Non-destructive method

• Relatively fast

• Multi-analysis of radionuclides

• Low running cost in routine laboratory

5

Typical detectors

• High-purity Germanium detector

• NaI scintillator

• Other scintillators (BGO, CZT, plastic, …)

6

NaI scintillator

• no cooling needed

• moderate resolution

• non-linear energy

7

HPGe detector

• cooling to reduce noise

• excellent resolution

• quasi-linear energy

8

Resolution and efficiency

99

Coaxial

Planar

Array detector

Multi-segmented

HPGe: crystal configurations

10

Product catalogues of manufacturers

•Ortec

•Canberra

•(Eurisys)

•DSG

•(PGT)

•(Tennelec)

•(Oxford Instr.)

•….

• K. Debertin and R.G. Helmer, “Gamma-and X-ray spectrometry withsemiconductor detectors“, North-Holland (Elsevier), 1988

• G. Gilmore and J. Hemingway, “Practicalgamma-ray spectrometry“, Wiley, 1995

• M.F. Annunziata Ed., „“Handbook of Radioactivity Analysis, Academic Press, 2003

• R. Jenkins, R.W. Gould and D. Gedcke ,„Quantitative X-ray Spectrometry”, Marcel Dekker Inc., 1995

Literature

11

Basic equation

Pt

CA

Peak area (#counts)

Measurement time (live time)

'Full Energy Peak' efficiency(FEP)

Gamma-ray emission

probability

12

Elaborate formula

K1 = summing correction

K2 = Branching correction

K3 = Equilibrium correction

1 2 3(1 )

d

m

BkgTOT Continuum tPeak

MC tSampleExp

REF MCREF

C C CA e K K K

eP

Combined activities from several gamma-rays

Correction factor from e.g. MonteCarlo

calculation

Reference sample (similar

geometry)

td = decay time (to a reference date)tm = measurement live time

Combined activities from several daughters to give activity of mother

13

Traceability - The Zanzibar effect

It is said that there once lived in Zanzibar a

retired sea-captain who was fanatical about

time. Every day, precisely at noon, he fired a

cannon, the sound of which reverberated over

Zanzibar Town.

"How," he was asked, "can you keep time so

accurately?"

"There is a watch-maker down in the town",

he said, "who keeps a clock in his window

that always shows the exact time. Every day

I check my time against his."

When the watch-maker was asked the same

question he replied,

"There is a retired sea-captain ...."

14

Traceability to the SI

• calibration sources for activity

• emission probability

• half-life

• measurement duration

• reference time (decay correction)

• dead-time corrections

• sample mass

• density (efficiency correction)

• detector-sample geometry

• NMI

• DDEP/ENSDF

• atomic clock

• reference

frequency

• calibrated mass

• chemical analysis

• caliper

Bq

s-Hz

Kg

m

15

Basic steps of -ray spectrometry

Stable set-up

Spectralmeasurements

Energy-FWHMcalibration

Peaklocate & fit

Visual inspection

Backgroundsubtraction

Nuclideidentification

Efficiency &summing effects

Parent-daughtercorrection

Uncertainty & Reporting

16

Efficiency calibration

• Measure full peak efficiency in a calibration source

with several gamma-rays

• Fit an empirical function to the data

• If the “real sample” is different from the

calibration source in shape, mass or composition –

calculate efficiency correction using an efficiency

transfer code

Decay corrections needed!

Beware of coincidence summing corrections!!!

C

tAP

17

Efficiency curve

htt

p:/

/okta

tas.c

h.b

me.h

u/o

kta

tas/k

onyvek/f

izkem

/gam

ma/s

okcsat/

hatk

alib.h

tml

Effic

iency

Energy / keV

Use SI-traceable standard sources

Error on activity is

systematic for

each gamma line

18

Efficiency relative to point at 10 cm

Simulated and measured efficiencies

→ sensitive to geometry and attenuation

Lépy

et

al, M

etr

olo

gia

52,

S123

19

Simulation codes

Codes for calculating efficiency transfer:

EFFTRAN, GESPECOR, DETEFF, ETNA

General purpose Monte Carlo codes:

GEANT, PENELOPE, EGS4 and MCNP

MC

REF

MC

SampleExp

REF

20

True coincidence effects

…destroy smoothness of calibration curve

htt

p:/

/ww

w.iup.u

ni-

bre

men.d

e/P

EP_m

aste

r_th

esis

/thesis

_2007/t

hesis

_chehade.p

df

Eu-152 close to the detector

Eu-152 far from the detector

21

True coincidences

photons detected at the same time

=> loss of 1 and 2, gain of '3' signals

1

2

3

22

Summing-in & summing-out

htt

p:/

/ww

w.iup.u

ni-

bre

men.d

e/P

EP_m

aste

r_th

esis

/thesis

_2007/t

hesis

_chehade.p

df

23

Peak identification & fitting

Different algorithms in deconvolution software

• Genie-2000 (Canberra)

• InterWinner (Eurisys)

• Gamma-Vision (Ortec)

• Gamma-W (Dr. Westmaier)

• Fitzpeaks

• HYPERMET

• + many other more or less home-made ones

24

Most algorithms include

• Gaussian peak

• Linear continuum with step-function

• Linear low-E tail

Debert

in,

and H

elm

er, “

X-r

ay a

nd g

am

ma-r

ay s

pectr

om

etr

y”

25

More complex models

• Gaussian

• Continuum with step

• Long term low-E tail

• Short term low-E-tail

• Hi-E tail

Model is important whenstatistical precision is high

Different shape for x-rays and annihilation peak D

ebert

in,

and H

elm

er, “

X-r

ay a

nd g

am

ma-r

ay s

pectr

om

etr

y”

26

Less tailing with “new generation” HPGe-detectors!

Important to have “nice” well separated peaks

to determine parameters for

tailing

Debert

in,

and H

elm

er, “

X-r

ay a

nd g

am

ma-r

ay s

pectr

om

etr

y”

27

511 keV annihilation peak

Fit different peak shape

Lépy

et

al, M

etr

olo

gia

52,

S123

28

Background & continuum subtraction

Measurement of Background

CPeakBkg

Measurement of sample

Cpeak

CContinuum

BkgNET TOT ContinuumPeakC C C C

29

Danger - uncertainty

Misrepresentation of continuum and peak

shape can create error on peak area

→ fit software is unaware, assumes model is perfect

→ if residuals of fit are not perfectly random,

uncertainty is underestimated!

→ uncertainty doublets often underestimated

Background is not constant and not Poisson

distributed

→ monitor background

→ take big uncertainty margin

30

Understanding background

1. Primordial (since formation of Earth)

238U, 235U, 232Th, 40K

(→226Ra, 222Rn, 210Po, 210Pb)138La, 87Rb, 147Sm, 176Lu, 187Re

2. Anthropogenic (man-made)

Fission: 137Cs, 134Cs, 85Kr, 125Sb, …

Activation: 60Co, 41Ar, …

(pure beta emitters: 90Sr, 3H)

3. Cosmogenic (induced by cosmic rays)

in Ge: 68Ge, 57Co, 58Co, 60Co, 65Zn, 54Mn, 63Ni,55Fe

31

Earth

p e±

nthermnfast±

0.1 2 40 60 200 200 1011

at surface (m-2s-1)

225 m underground

(m-2s-1)

ntherm nfast

<2 <2 0.1 1011

Primary cosmic ray:

90 % p

9 % a

1 % heavier nuclei (up to Fe)

Atmospherep0

p±

p±

103 m-2 s-1

e-e+

m±um

Extremely high energiesfrom outer space,GeV range from sun

p, n, 7Be, 14C, 36Cl, ….

m

m u

up

32

0

10

20

30

40

50

6030

002

3000

330

004

3000

530

006

3000

730

008

3000

930

010

3001

130

012

3001

330

014

3001

530

017

3001

830

019

3002

030

021

3002

230

023

3002

430

025

3002

630

028

3002

9

Time / Measurement No.

Count rate 40-2700 keV 0.01 / d-1

Net count rate at 609 keV / d-1

Radon concentration / Bq·m-3

0

10

20

30

40

50

6030

002

3000

330

004

3000

530

006

3000

730

008

3000

930

010

3001

130

012

3001

330

014

3001

530

017

3001

830

019

3002

030

021

3002

230

023

3002

430

025

3002

630

028

3002

9

Time / Measurement No.

Count rate 40-2700 keV 0.01 / d-1

Net count rate at 609 keV / d-1

Radon concentration / Bq·m-3

0

10

20

30

40

50

6030

002

3000

330

004

3000

530

006

3000

730

008

3000

930

010

3001

130

012

3001

330

014

3001

530

017

3001

830

019

3002

030

021

3002

230

023

3002

430

025

3002

630

028

3002

9

Time / Measurement No.

Count rate 40-2700 keV 0.01 / d-1Count rate 40-2700 keV 0.01 / d-1

Net count rate at 609 keV / d-1Net count rate at 609 keV / d-1

Radon concentration / Bq·m-3Radon concentration / Bq·m-3Radon concentration / Bq·m-3

Data from a low-background detector with

radon in the background

33

Basic activation-decay curve

Activity has to be related to a reference time

td=decay time

activation time

tm= measurement time (real time)

0

0.5

1

1.5

2

2.5

3

0 1 2 3 4 5 6 7 8 9 10Time (days)

Activ

ity (a

.u.)

Half-life: 1 day

34

Decay corrections

• Decay since reference date

• Decay during measurement

dte

(1 )mte

1

mt

35

The problem of erroneous half-lives

Uncertainties often underestimated

Metrologia 52 (2015) S51

36

209Po half-life 50 years in error by 20%

Used as a tracer for polonium in environment

• old: 102 (5) a

• new: 123 (2) a

→ 0.11% error on activity per year

37

Problematic emission probabilities

P of 63.3 keV line following the decay of 234Th (238U decay chain)Without interference at 62.88 keV, P=0.0164(28)%

Table with evaluations and/or recommended data, made October 2010

Reported value Reference4.8 (6)% Nucléide - 20004.80% Mini Table de Radionucléides, 20074.49% Genie-2000

4.1 (7)% ab-Table, Wahl4.1 (7)% PTB-bericht 19984.00 (6)% Nuclides20003.75 (8)% DDEP - 20093.7 (2)% The Raqdiochemical Manual (1998)3.7 (4)% NNDC3.69 (7)% NDS - 20073.6 (1)% PTB-Ra-16/3, 1989

Std.dev: 0.45%Rel Std. dev. 11%

(Max-min)/average: 30%

38

How to measure U-238

• Parameters affecting quantification of 238U via 234Th

using -ray spectrometry.

• Use of correct decay data, suitable detectors, optimised

sample size, enhanced spectral amplification, correction for

peak interferences and control of background.

39

238U decay chain

238U decay chain

Suitable for gamma spec

40

Parent-daughter decay

transient equilibrium (Tp>Td)

41

Parent-daughter decay

secular equilibrium (Tp>>Td) → total activity = 2×parent

Use correct half-life when calculating activity!!!

42

Ingrowth radon

Decay starting at Ra-226

0102030405060708090

100

0 5 10 15 20 25 30Day

Act

ivity

Ra-226, alphaRn-222, alphaPo-218, alphaPb214, betaBi-214, betaPo-214, alphaPb-210, beta

T1/2222Rn: 3.8 days

Secular or transient?

43

Minimum detectable activity

: Increase detector size

→ may also increase background

: Increase sample size

→ may also increase continuum

tm : Longer measurement

→ “only” improves MDA by square root

Reduce background in order to obtain better MDA!

1

m

Bkg

t

CRMDA

1

Case study I Alpha spectrometry

Dr Dr Stefaan PomméInstitute for Reference Materials and Measurements, Geel, Belgium

(stefaan.pomme@ec.europa.eu)

Ljubljana, June 2016

2

•Slides 3 to end are the intellectual property of EC-JRC-IRMM and

Dr. Dr. Stefaan Pommé.

•“Unauthorised reproduction constitutes a copyright infringement and may lead to prosecution or civil

proceedings“

Review paper

• Three typical case studies

3

Reference to case study

4

Reference to case study

5

6

FOR 226Ra ACTIVITY CONCENTRATION IN WATER BY ALPHA SPECTROMETRY

UNCERTAINTY BUDGET

7

226Ra activity concentration in waterby a-spectrometry

Chemical separation of 226Ra

from mineral water

Alpha-particle spectrometry of

solid sources on filter

8

Uncertainty budget for 226Ra activity concentration in water by a-spectrometry

3 major contributors to uncertainty

sample preparation and chemical recovery

solid angle of alpha spectrometer

spectral deconvolution

9

Sample preparation and chemical recovery

10

Sample preparation and chemical recovery determination

133Ba as a tracer for

chemical recovery; measured

by -ray spectrometry

BaSO4 co-precipitation procedure

133Ba226Ra

11

Uncertainty due to sample preparation and chemical recovery

Uncertainty contributions:

standard source 2%weighing 1%counting uncertainty 1%YRa-226/YBa-133 ≥ 1 8%

total uncertainty Rchem 8%

133StdBa

133StdBa

133Std-Ba133StdBa

133sampleBa133sampleBa

133sampleBa

chem RP

mt

mt

PR

12

Solid angle of alpha spectrometer

13

a-particle spectrometry

450 mm2 PIPS detector

source at a distance of 5

mm

High-resolution a-particle

spectrometer

14

Simple case of solid angle Wfor point source

)cos1(2 W

d

Rarctg D

Point source

RD

d

circular detector

15

Uncertainty on the solid angle W

d

)d(

R

)R(2

d

)d(

R

)R()tg(

cos1

)(cos)(

D

D

2

2

2

D

D

22

3

W

W

Uncertainty contributions:

Detector radius RD= 11.95 ± 0.05 mm

Distance source-detector d = 5.0 ± 0.1 mm

uncertainty W 1.3%

(W) for a point source

16

Uncertainty due to source radius

Co-axial homogenous disk source

RS

RD

d

W

n

1i

2

S

D

)cosxy(cosx

sin

R

R

n

2

Uncertainty contribution:

Source radius RS=11±0.5mm

uncertainty W 2.5%

17

Uncertainty source out-of-centre

Eccentric source

a RS

RD

d

dses

)sR(J)sR(J)sa(J

R

R4 sh

0

S1D10

S

D

W

Uncertainty contribution:

Eccentricity a=2 mm

uncertainty W 2%

Calculted with MathCad

18

Activity distribution in sources

...not as homogeneous as could be desired!

0

1

2

3

4

0 5 10 15 20outer radius of region of interest (mm)

rela

tiv

e w

eig

hin

g f

ac

tor

0

1

2

3

4

0 5 10 15 20outer radius of region of interest (mm)

rela

tiv

e w

eig

hin

g f

ac

tor

0

1

2

3

4

5

6

0 5 10 15 20outer radius of region of interest (mm)

rela

tiv

e w

eig

hin

g f

ac

tor

19

Use autoradiographs to calculate the ‘real’ solid angle W

Non-homogeneous, realistic source

Rout

RD

d

Rin

W = weighted mean

of Wrings

20

Solid angle calculated from autoradiographs

0,15

0,17

0,19

0,21

0,23

0,25

0,27

0,29

0,31

0,33

0 2 4 6 8 10 12

equivalent distance from detector symmetry axis, mm

ge

om

etr

y f

ac

tor W/4

RD=11.95mm

d=5mm

a=0-11mm

16 sources

0,24

0,245

0,25

0,255

0,26

0,265

0,27

7 7,2 7,4 7,6 7,8 8 8,2 8,4

equivalent distance from detector symmetry axis, mm

geo

metr

y f

acto

r W/4

standard deviation W 3%

21

Uncertainty budget for the solid angle W

Uncertainty contributions:

radial activity distribution 3%distance 1.2%detector radius and tilt 0.5%external eccentricity 1mm 1%

total uncertainty W 3.4%

22

Spectral deconvolution

23

Spectral deconvolution

B -T-NgN

2

g )10/T(TBN u(N)

7.68 MeV

4.78 MeV5.49 MeV

u(N) = 1-1.5%

Energy, MeV

24

Total uncertainty budget

25

Total uncertainty budget

ComponentUncertainty

(%)

Chemical recovery 8

Solid angle 3.4

Counting statistics (incl. background)

1.5

Counting time 0.005

Dead time 0.005

Half-life (T1/2 = 1600 a) 9.3E-05

Combined uncertainty (quadratic sum) 9.0

26

Conclusions

226Ra activity concentration – measured by a-particle spectrometry

Chemical recovery – major improvement only through better determination of YRa-226/YBa-133

Uncertainty in W – procedure applicable to other a-emitters

27

Chemist in desert …

28

Try to make a comprehensive uncertainty budget

Consider all possible contributors and try to quantify

Conclusions

LiquidscintillationtechniqueMarko Štrok

Outline What is liquid scintillation counting For what radionuclides can be used Advantages and disatvantages of LSC Scintillation process LSC cocktail LSC instrument Beta and alpha LSC spectra Quench Quench correction Food samples preparation for LSC

What is liquid scintillationcounting Scintillation = flash of light produced in

materials when they absorb ionizing radiation Light produced is proportional to the radiation Scintillator = liquid Counting flashes of light with PMT

For what radionuclides?

LSC and radionuclides in food H-3 in water arround NPP and RN monitoring C-14 in food arround NPP Sr-90/89 in water and food arround NPP and

for monitoring Pb-210 (and Po-210) in marine mussels and

fish Ra-226 in water Gross alpha/beta in water for RN monitoring

Advantages of LSC No problems with absorption or selfabsorption Short dead time (~20 ns) – large linear range High counting efficiency (up to 100 %) Applicable to beta and alpha emitters Method of choice for low energy beta emitters

Disadvantages of LSC Sample has to be mixed with LSC cocktail Higher background Lower energy resolution for alpha emitters

compared to alpha spectrometry

Scintillation process3H

Solvent

Primary scintillator

Secondary scintillator

PMT

β

Dipol – dipol interactions

Light (200 – 300 nm)

Molecule collisions

Light (340 – 400 nm)

Light (400 – 470 nm)

LSC cocktail Solvent Primary scintillator Secondary scintillator Surfactants (aqueous samples)

+ Sample

Solvent Fast dissolution of the sample in large amonuts Should accept the energy of radiation decay

Aromatic solvents required for initiation of thescintillation process

PXE

DIPN

benzene

toluene

xylene

pseudocumene

DIPN = 2,6-di-isopropylnaphtalene, PXE = 1-phenyl-1-(3,4-dimethylbenzol)ethane

Primary scintillator Compounds with highly conjugated π-electron

system in heterocyclic molecules Oxazoles, oxadizoles, benzooxazoles and

pyrazolines (emission vavelenght 340-400 nm) Primary scintillator can be excited easily 5-12 g/L

PPO PBD Butyl-PBD

BBOT

BBOT = 2,5-bis-2-(tert-butylbenzooxazolyl)-tiophene, Butyl-PBD = 2-(4-tert-butylphenyl)-5(4-biphenyl)-1,3,4-oxadiazole,

PBD = 2-phenyl-5-biphenyl-1,3,4-oxadiazole, PPO = 2,5-diphenyloxazole

Secondary scintillator Highly conjugated heterocyclic compounds with

emission wavelenght above 400 nm wherePMT‘s have the highest sensitivity

Shifting wavelenght of the primary scintillator 0.5 % of the cocktail

POPOP Bis-MSB

Bis-MSB = p-bis-(o-methylstyryl)-benzene, POPOP = 1,4-bis-2-(5-phenyl-oxazolyl)-benzene

Surfactant Scintillators are non-polar organic compounds To dissolve large amount of polar compounds

such as water, surfactant need to be added Surfactat has polar and non-polar region Can make up to 40 % of cocktail voume

resulting in lower efficiency

Phosphoric acid estersEthoxylated alkylphenol

Sample Transparent With low content of mineral acids or bases Up to 50 % of total volume if it is polar Should be homogeneously mixed with LSC-

cocktail Phase separation causes selfabsorption

LSC instrument

Reduction of background Dark current (PMT noise)

=> coincidence circuitry=> lower temperature

External radiation=> lead shield ( up to 1 T) + copper to absorb lead X rays=> going underground=> guard detector (scintillators, BGO)

Vials=> low K-40 glass vials=> plastic vials (not suitable for all cocktails)=> PTFE vials (for special applications like C-14 dating)

LSC-cocktail=> low background cocktails (like Ultima Gold LLT, uLLT)

Alpha / Beta discrimination Pulse shape analysis (PSA)

Time

Inte

nsi

ty

Beta pulse

Alpha pulse

Selecting optimum PSA value

PSA value

Sp

illo

ve

r

Beta in alpha

Alpha in beta

Measure pure beta and pure alpha emitter Matrix should be the same as for samples

Other features of LSC instrument Pulse amplitude comparison (PAC) Chemiluminescence correction (alkaline

samples, H2O2) Static electricity eliminator Color quench correction

Beta and alpha LSC spectra

Energy (keV)

# c

ou

nts

H-3

C-14

Am-241

Sr-90

Y-90

Calculation of activity Activity:

𝐷𝑃𝑀 =𝐶𝑃𝑀

𝑒𝑓𝑓

1 Bq = 60 DPM

Figure of merit (FOM)

𝐹𝑂𝑀 =𝑒𝑓𝑓2

𝑏𝑘𝑔

Quench3H

Solvent

Primary scintillator

Secondary scintillator

PMT

β

Dipol – dipol interactions

Light (200 – 300 nm)

Molecule collisions

Light (340 – 400 nm)

Light (400 – 470 nm)

Physical quench

Chemical quench

Color quench

Color quench

Chemical quench All samples cause chemical quench Examples:

Weak

• RH

• RF

• ROR

• RCN

• ROH

• RCOOR

• RCl

• H2O

Moderate

• RCOOH

• RNH2

• RCH=CHR

• RBr

• RSR

• RX2

Strong

• RSH

• RCOR

• RNHR

• RCHO

• R2NR

• RI

• RNO2

• RX3

R = alkyl-residue

Color quench Light is absorbed by the colored sample before

it comes to PMT

How to deal with color quench:=> sample dilution=> decoloration with H2O2

Increasing severity of color quench

Why bother with quench? It affects detection efficiency

How to deal with quench:=> prepare samples and standards with the same

quench=> apply quench correction

Energy (keV)

# c

ou

nts

Unquenched spectrum

Quenched spectrum

Quench correction Internal standard Analysis of beta spectrum of the sample Analysis of Compton spectrum of external

standard (Ba-133 or Eu-152)

Internal standard Measure sample Add known amoun of standard and don‘t

change quench Remeasure sample with added standard Calculate results:

𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 =𝑐𝑝𝑚𝑠+𝑠𝑡𝑐𝑝𝑚𝑠

𝑑𝑝𝑚𝑠𝑡

𝑑𝑝𝑚𝑠 =𝑐𝑝𝑚𝑠

𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦

Time consuming, more expensive

Analysis of beta spectrum of thesample Channel ratio method

Problem where to put lower end of channel B

Click to edit Master text stylesSecond level

•Third level

Analysis of beta spectrum of thesample Spectral index of the sample (SIS)

Using quench-induced shift in average beta energy to calculate SIS value

Independent from selection of channels Drawback when samples with low count rate are

measured Not applicable for nuclide mixtures

Click to edit Master text stylesSecond level

•Third level

Analysis of Compton spectrum ofexternal standard Spectral index of external standard (SIE) H-number Spectrum quench parameter of external

standard (SQP(E))

Sensitive to plastic vial effects, not suitable forextreme quench, color quench causes problems

Transformed spectral index of external standard (tSIE)

Click to edit Master text stylesSecond level

•Third level

Analysis of Compton spectrum ofexternal standard SQP(E) Eu-152 standard

Click to edit Master text stylesSecond level

•Third level

Analysis of Compton spectrum ofexternal standard tSIE Ba-133 standard

Click to edit Master text stylesSecond level

•Third level

Analysis of Compton spectrum ofexternal standard tSIE Ba-133 standard

Energy (keV)

# c

ou

nts

tSIE

10 %

20 % of total counts

Click to edit Master text stylesSecond level

•Third level

Quench curve

Quench indicator

(SIS,tSIE, SQP(I), SQP(E),…

Eff

icie

nc

y

Standard + different amount of quencher

Click to edit Master text stylesSecond level

•Third level

Sample preparation H-3 in water

Distillation

Electrolytic enrichment

Low activity

High activityMixing with LSC cocktail

LSC measurementSecond distillation Mixing with LSC cocktail

Click to edit Master text stylesSecond level

•Third level

Sample preparation Pb-210 in food and water

drying

Grinding, homogenising

Food

Pre-concentration

with Mn oxides

LSC measurement

Addition of stable Pb tracer

Mixing with LSC cocktail

Leaching with

HNO3, HCl, H2O2

Water

Centrifugation, dissolution of

precipitate with H2O2 and HCl

Evaporation

Separation on Sr Resin

Addition of stable Pb tracer

Aliquot for chemical

recovery determination

on ICP-MS

Click to edit Master text stylesSecond level

•Third level

Conclusion LSC is very versatile and useful technique Care should be taken with

Sample preparation Selection of adequate cocktail and vials Setting up optimum channel regions to optimize

FOM Adequate quench correction