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Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities. LiquiScint 2004 17-18 May - Masaeykova kolej, Thákurova 1, Praha 6. Robert Schupfner Environmental Radioactivity Laboratory (URA) Institute of Analytical Chemistry, Chemo- and Biosensors,

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slide1
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

LiquiScint 2004

17-18 May - Masaeykova kolej, Thákurova 1, Praha 6

Robert SchupfnerEnvironmental Radioactivity Laboratory (URA)

Institute of Analytical Chemistry, Chemo- and Biosensors,

University of Regensburg

robert.schupfner@chemie.uni-regensburg.de

slide2
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Summary

 Radiological Aspects of Decommissioning

 General Conditions of Radioanalytical Methods

 Application of Liquid Scintillation Counting (LSC)

  • 41Ca und 45Ca
  • 55Fe und 59/63Ni
  • 90Sr (90Y)

 Results and Conclusion

robert.schupfner@chemie.uni-regensburg.de

slide3
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Demands of Radiological Safety for the Decommissioning of Nuclear Facilities

 decommissioning personell and members of the public

 before, during and after decommissioning

 long-term ensuring of radioactive waste storage

 complete radiological assessment including activity determination of single radionuclides as basic requirement

robert.schupfner@chemie.uni-regensburg.de

slide4
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Sample Materials

 human excreta: urine, faeces

 metals: steels, alloys

 corrosion products

 building materials: concrete, mortar, bricks

 glass fibres

 organic and inorganic chemical compounds

 organic and inorganic chemical compounds

 environmental materials: soils, sediment, plant, food, ...

robert.schupfner@chemie.uni-regensburg.de

slide5
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Which Analytical Problems Arise during Decommissioning

of Nuclear Facilities ?

 sample materials

 physical decay properties of the radionuclides of interest

 various mixtures of radionuclides

 chemical behaviour

 time scale

 range of activities

robert.schupfner@chemie.uni-regensburg.de

slide6
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Radionuclides of Interest (not complete)

robert.schupfner@chemie.uni-regensburg.de

slide7
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Portions of Available Measurement Methods

robert.schupfner@chemie.uni-regensburg.de

slide8
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Application of Liquid Scintillation Counting (LSC Quantulus 1220)

Active and passive shielding

Minimising the background counting rates:

  • about 1 cpm for 3H, 41Ca, 55Fe, 241Pu
  • about 3 cpm for 14C, 63Ni
  • about 5 cpm for 99Tc, 129I
  • about 7 cpm for 89Sr, 90Y, 45Ca
  • about 2 to 3 cpm for a-emitters

robert.schupfner@chemie.uni-regensburg.de

slide9
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Application of Liquid Scintillation Counting (LSC)

Advantages

 low radiation energies

 high counting efficiency

 low background counting rates

LSC Quantulus 1220

 energy resolution

enables an increased selectivity

 low values of lower limits of detection

 a variety of suitable scintillation cocktails is commercially available

Disadvantages

 as a rule application only after radio-

chemical purification procedure

 increased expense to assure high

quality

 high costs of low background counting

devices (LSC Quantulus 1220)

 energy resolution is rather limited

 increased expense of sample preparation in sample solutions with high salt content

 stability of sample-cocktail mixture in

sample solutions with high salt content

robert.schupfner@chemie.uni-regensburg.de

slide10
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Quality of Radiochemical Analysis Applying LSC

 selective

 low values of detection limits

 accurate and precise

 efficient: fast, reliable, low costs

robert.schupfner@chemie.uni-regensburg.de

slide11
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 41Ca and 45Ca

robert.schupfner@chemie.uni-regensburg.de

slide12
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 41Ca und 45Ca

Decay properties

 dissolution of sample material (concrete)

 radiochemical purification of 41Ca, 45Ca

 optimising the sample preparation with a suitable scintillation cocktail

 activity determination applying LSC Quantulus 1220

robert.schupfner@chemie.uni-regensburg.de

slide13
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 41Ca und 45Ca

Determination of Counting efficiencies of 41Ca versus Content of stable Ca2+ in the Sample Solution

robert.schupfner@chemie.uni-regensburg.de

slide14
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 41Ca und 45Ca

Lower Limit of Detection (lld) of 41Ca versus Content of stable Ca2+ in the Sample Solution

robert.schupfner@chemie.uni-regensburg.de

slide15
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 41Ca und 45Ca

A

B

C

robert.schupfner@chemie.uni-regensburg.de

slide16
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 41Ca und 45Ca

 Minimum lld at about 1200 to 1300 mg Ca2+: 0,05 Bq 41Ca ·(g Ca2+)-1

 value of lld is proportional to the activity A(45Ca) of 45Ca in the sample:

lld (m) = lld (m, A(45Ca)=0) + k· A(45Ca)

with: k 0,008 Bq 41Ca ·(g Ca 2+·Bq 45Ca )-1

 assuming a content of Ca of about 20 % in concrete:

the LSC method tolerates 5,5 to 7,5 g of concrete

 minimum value of about 0,0141Ca ·(g concrete)-1

robert.schupfner@chemie.uni-regensburg.de

slide17
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 55Fe and 59/63Ni

neutron activation sth / barn

54Fe (n,g) 55Fe 2,25

58Ni (n,g) 59Ni 4,6

62Ni (n,g) 63Ni 14,2

robert.schupfner@chemie.uni-regensburg.de

slide18
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 55Fe and 59/63Ni

Decay Properties

robert.schupfner@chemie.uni-regensburg.de

slide19
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 55Fe and 59/63Ni

    • Decontamination factors are sufficiently high.
  • 105 to 109 for 55Fe
  • 104 to 1011 for 63Ni
  • Chemical yield
  • to about 120 mg Fe (92 ± 3) %
  • to about 40 mg Ni (95 ± 5) %

robert.schupfner@chemie.uni-regensburg.de

slide20
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 90Sr (90Y)

89

90

90

Sr

Sr

Y

89

90

90

Starting nuclide

As

Se

Se

Fission yield

4,764%

5,835%

5,835%

90

89

90

Decay Product

Y(stable)

Y(radioactive)

Zr

(stable)

Half Life Time

50,5 d

29,12 a

2,761 d

-2

-1

-5

-1

-1

-1

Decay Constaqnt

1,37·10

d

6,52·10

d

2,51·10

d

-

-

-

b

, (g)

b

b

, (g)

Decay

Energy

583,3

keV

195,7

keV

934,8

keV

-1

-1

-1

Probability Y

1 (

Bq

·s)

1 (

Bq

·s)

1 (

Bq

·s)

 until now: high expense

 development: significant less expense

robert.schupfner@chemie.uni-regensburg.de

slide21
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 90Sr (90Y)

90Y is in radioactive equilibrium with 90Sr

 Determination of chemical yield applying 88Y

88

88

-

Y

Sr + e

y

nuclide

Half life

time

E/keV

i

-1

Decay

/ (Bq s)

g

-radiation

Y-88

106,63

d

898,2

0,94

1836,0

0,9933

ec

-radiation

ca. 11

ca. 1

 90Sr Determination after Liquid -Liqid Eytraction of 90Y

using Di-(2-Ethylhexyl)-phosphate (C16H35O4P) HDEHP

robert.schupfner@chemie.uni-regensburg.de

slide22
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 90Sr (90Y)

Dissolution of Sample Material Containing 90Sr (90Y)

Chemical Yield Tracer 88Y (11 Bq)

Sample Solution

Sr2+, Y3+

Liquid -Liquid Extraction of

90Y, 88Y in HDEHP

Na+, K+, Cs+, Mg2+,Ca2+, Sr2+,Co2+, U, Pu, Am,

and other interfering nuclides

Re-extraction of

90Y, 88Y in 9 m HCl

Washing

Fe3+

LSC

Precipitation of Y(OH)3

robert.schupfner@chemie.uni-regensburg.de

slide23
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 90Sr (90Y)

robert.schupfner@chemie.uni-regensburg.de

slide24
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 90Sr (90Y)

Fig. 1: LSC-Spectrum of 11 Bq 88Y and blank

Fig. 2: LSC-Spectrum of 11 Bq 88Y and 21 Bq 90Y and blank

robert.schupfner@chemie.uni-regensburg.de

slide25
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 90Sr (90Y)

Parameters of determination of 90Sr (90Y) in concrete

Parameter

Material

9,9 g concrete

Dissolution

HCl (32 %)

Analysis

Extraction of Y with HDEHP

Detection

LSC Quantulus

Berthold LB770

90

h

(

Y) / Ips/Bq

0,79 ± 0,02

0,43 ± 0,01

phys.

h

/%

84 ± 7

chem.

range of time /h

< 0,1

1

radiometric

titrimetric

88

Y(ca. 11 Bq)

stable Y

n

/Ipm

about 72

about 0,5

0

life time t

/min

1000

1000

L

lld/Bq/g

0,003

0,0005

ld/Bq/g

0,005

0,0008

robert.schupfner@chemie.uni-regensburg.de

slide26
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 90Sr (90Y)

  •  Successful Participation in Official Comparison Analyses of the Federal Office for Radiation Protection (BfS)
    • Liquid Effluents; Water
    • Human Excretion (urine)  Br: 0,07; sA: 0,05; sB: 0,05
  •  Soil Samples from 5 g to 100 g Br: -0,14; sA: 0,04; sB: 0,05

robert.schupfner@chemie.uni-regensburg.de

slide27
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Example: 90Sr (90Y)

 high and constant values of chemical yield (70 bis 90 %)

 tolerates high amounts of sample material and salt freight ,

up to 100 g of soil

minimum of lower limit of detection at 60 g of soil:

about 1 mBq 90Sr /g (dry weight) applying low-level b-counter LB770;

about 9 mBq 90Sr/g (dry weight) applying low-level LSC Quantulus 1220

 application of the method of isotopic dilution (88Y) makes this analysis

very fast (about 2 to 3 hours per sample and per one technichian)

 increased selectivity with respect to interfering 152Eu in the sample using b-spectrometric abilities of the LSC- detection method

robert.schupfner@chemie.uni-regensburg.de

slide28
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Conclusion

LSC is a important tool relieving analytical problems arising with decommissioning of nuclear facilities

LSC is well suited detecting low-energy radiation emitting radionuclides as 41Ca, 55Fe, 59/63Ni, 241Pu

 In combination with liquid-liquid extraction techniques LSC is well suited detecting 90Sr(90Y) even in complex sample materials

 reliable radiochemical purification procedures are necessary to realise a sufficient selectivity, accuracy, precision, lower limit of detection

 Increased efforts are required to fulfil high quality criteria

 In future much work must be done in further research combining both radiochemical procedures and LSC methods

robert.schupfner@chemie.uni-regensburg.de

slide29

Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Acknowledgement to

 The members of the organising committee for inviting me to the beautyful city of Prague and for their help and for their patience

 Mr. Gesewsky (†) from BfS-IHS for supplying us with the 41Ca solution

 Dr. Günther from PTB, Braunschweig for certification of the 41Ca solution

 All companies supplying us with the scintillation cocktails free of charge

 The Bavarian State Ministry for State Development and Environmental Affairs for financial support

 The Federal Office for Radiation Protection for financial support

 All co-workers of my laboratory

robert.schupfner@chemie.uni-regensburg.de

slide30
Application of LSC Methods on Radiochemical Problems Arising with Decommissioning of Nuclear Facilities

Thank you for your attention and

your patience

If there are further questions, please ask me, I`ll try to answer them.

robert.schupfner@chemie.uni-regensburg.de