Analysis of Radioactive Disequilibrium in Natural Decay Chains due to Processing

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1 Analysis of Radioactive Disequilibrium in Natural Decay Chains due to Processing Hans-Jürgen Lange 1, Rainer Dargel 2 1Canberra GmbH, Walter-Flex-Str. 66, Rüsselsheim Phone: , address: 12 jlange@canberra.com

2 Fundamental basics What do we need for accurate activity measurements of Natural Occuring Radioactive Material?

3 Fundamental basics Information about nuclear decays (nuclear data) nuclide library information Detector efficiency as a function of detector, geometry, matrix, Improvement of background by passive and active shielding, flushing with nitrogen Adjustment of peak fit algorithm. Interactive check! Information about processing of material prior to measurement True Coincidence effects on special energies for certain nuclides

4 0.72% 235 U (T 1/2 =7*10 8 a) 231 Th (T 1/2 =25,6 h) β Pa (T 1/2 =3,3*10 4 a) 227 Ac (T 1/2 =22 a) (1,2%) β - (98,8%) 223 Fr (T 1/2 =22 m) 227 Th (T 1/2 =18,7 d) Based on: U. Schkade, priv.com. Measurement of 235 U and daughters β Ra (T 1/2 =11,4 d) 219 Rn (T 1/2 =3,9 s) Gas! γ : 143,76 kev ; 10,96 % γ : 163,33 kev ; 5,08 % γ : 185,72 kev ; 57,20 % γ : 205,31 kev ; 5,01 % 223 Ra 226 Ra (144,23 kev; 3,22 %) (186,10 kev; 3,51 %) γ : 235,97 kev ; 12,3 % γ : 269,46 kev ; 13,7 % γ : 271,23 kev ; 10,8 % 228 Ac (270,25 kev; 3,46 %)

5 Measurement of 235 U and daughters 219 Rn (T 1/2 =3,9 s) Gas! 215 Po (T 1/2 =1,8 ms) 211 Pb (T 1/2 =36,1 m) β Bi (T 1/2 =2,15 m) (99,68%) β - (0,32%) 207 Tl (T 1/2 =4,8 m) 211 Po (T 1/2 =0,52 s) β Pb (stabil) Additionally 219 At, 215 Bi und 215 At are produced!

6 Measurement of 238 U and daughters 99.27% Recoil loss possible 238 U (T 1/2 =4.5*10 9 a) 234 Th (T 1/2 =24.1 d) β - 234m Pa (T 1/2 =1.2 m) β U (T 1/2 =2.5*10 5 a) 230 Th (T 1/2 =8*10 4 a) γ : 92,37 kev ; 2,42 % γ : 92,79 kev ; 2,39 % γ : 92,6 kev ; 4,81 % Th-Kα1 (93,35 kev; 5,6 %) γ : 1001,03 kev ; 0,839 % γ : 766,37 kev ; 0,316 % γ : 63,28 kev ; 4,1 % 232 Th(63,81 kev; 0,263 %)

7 Measurement of 238 U, 226 Ra and daughters Gas!! 226 Ra (T 1/2 =1600 a) 222 Rn (T 1/2 =3.8 d) 218 Po (T 1/2 =3.05 m) (99,98%) β - (0.02%) 214 Pb (T 1/2 =26.8 m) 218 At (T 1/2 =2 s) β Bi (T 1/2 =19.8 m) γ : 186,10 kev ; 3,51 % 235 U : (185,72 kev; 57,2 %) γ : 295,22 kev ; 18,15 % γ : 351,93 kev ; 35,10 % 211 Bi (351,06 kev; 12,91 %) γ : 609,31 kev ; 44,6 % γ : 1120,29 kev ; 14,7 % γ : 1764,49 kev ; 15,1 %

8 Measurement of 238 U, 226 Ra and daughters - Measurement of the 186,10 kev-linie ; 3,51 % - But interfering with 185,72 kev; 57,2 % of 235 U 1- Use of 235 U-activity from other energy lines and correct the 226 Ra-activity 2- Calculate 238 U-activity from daughter nuclides. Use of natural ration for 238 U/ 235 U=21,7 for 235 U-activity => For 2 equillibrium is essential!

9 Measurement of 238 U, 226 Ra and daughters - Measurement of daughters 214 Pb and 214 Bi - But 222 Rn gaseous => losses 214 Pb γ : 295,22 kev ; 18,15 % γ : 351,93 kev ; 35,10 % Interferenz 211 Bi (351,06 kev; 12,91 %) 214 Bi γ : 609,31 kev ; 44,6 % γ : 1120,29 kev ; 14,7 % γ : 1764,49 kev ; 15,1 % Gastight container for measurement and storage needed!

10 Measurement of 238 U, 210 Pb and daughters 214 Bi (T 1/2 =19.8 m) (0,04%) β - (0.02%) 210 Tl (T 1/2 =1.3 m) 214 Po (T 1/2 =162 µs) β Pb (T 1/2 =22a) (7.5*10-7 %) β - (100%) 206 Hg (T 1/2 =8.1 m) 210 Bi (T 1/2 =5.0 d) β - (5*10-6 %) β Tl (T 1/2 =4.3 m) 210 Po (T 1/2 =138.4 d) β Pb (stabil) γ : 46,54 kev ; 4,25 %

11 Measurement of 232 Th and daughters Efficiencycheck 232 Th (T 1/2 =1,4*10 10 a) 228 Ra (T 1/2 =5,7 a) β Ac (T 1/2 =6,13 h) β Th (T 1/2 =1,9 a) 224 Ra (T 1/2 =3,64 d) 220 Rn (T 1/2 =55,6 s) 216 Po (T 1/2 =0,15 s) γ : 63,81 kev ; 0,263 % Ra Th (63,28 kev; 4,1 %) γ : 209,25 kev ; 3,89 % γ : 338,32 kev ; 11,27 % γ : 911,20 kev ; 25,80 % γ : 968,97 kev ; 15,8 % (338,28 kev; 2,79 %) γ : 240,99 kev; 4,10 % 214 Pb Gas!! (242,00 kev; 7,12 %)

12 Measurement of 232 Th and daughters 216 Po (T 1/2 =0,15 s) 212 Pb (T 1/2 =10,6 h) β Bi (T 1/2 =60,6 m) (36,2%) β - (63,8%) 208 Tl (T 1/2 =3.1 m) 212 Po (T 1/2 =0.3 µs) β Pb (stabil) γ : 238,63 kev ; 43,30 % γ : 300,09 kev ; 3,28 % 227 Th 231 Pa (300,00 kev; 2,70 %) (300,07 kev; 2,47 %) γ : 727,33 kev ; 6,58 % γ : 583,19 kev ; 30,4 % γ : 860,56 kev ; 4,47 % γ : 2614,53 kev ; 35,64 % (Abundance * 0.362) 228 Ac (583,41 kev; 0,111 %)

13 Measurement of natural decay chains Step 1: Step 2: Is there a consistent analysis with all 3 decay chains in equilibrium? Is there a constant factor between the 238 U-chain and the 235 U-chain of 21.7 => easy interpretation Nuclide library with all lines correlated to the progenitor! 235 U, 238 U or 232 Th Abundances and halflives!

14 Measurement of natural decay chains Step 3: What are the nuclides that caused the disequilibrium? Does the disequilibrium comes from: 1- Geochemical processes 2- Effects from processing 3- Gas losses from measurement container Step 4: How do these disequilibria influence radiation protection Examples: U/ 234 U-activity Recoil followed by solution in water Pb- 214 Bi different to 226 Ra due to emanation Pb activity increased by filtering of aerosols or electrostatic effects => Exact analysis of peak areas important

15 Steps to improve accuracy of net peak areas Background reduction (passive/active shielding) Improved efficiency functions and check of results Peak fit algorithm

16 Choice of detector (Calibration factor)

17 Ultra-Low-Level measurements Cellar Collaboration Source: Cellar booklett and priv. Communication M. Köhler

18 Efficiencies for different samples 3,00E-02 2,50E-02 5,00E-02 Ta-ore 3 cm Ta-ore vs Sand Ta-ore vs Sand Efficiency 2,00E-02 4,00E-02 Reihe1 5,00E-02 1,50E-02 Reihe2 Reihe1 3,00E-02 Reihe2 1,00E-02 4,00E-02 2,00E-02 5,00E-03 3,00E-02 0,00E+00 1,00E-02 2,00E ,00E+00 1,00E Energy 600 [kev] Efficiency E fficiency 0,00E+00 Energy [kev} Energy [kev}

19 Fundamental basics x-ray energies of elements Element O Fe Ge Zr Nb I Ta Hg Pb kα1 [ev] kα2 [ev] kβ1 [ev]

function Ta-ore vs Sand 5,00E-02 4,00E-02 Reihe1 Reihe2 Efficiency

20 X-ray fluorescence analysis Output of x-ray fluorescence analysis can be used as input for Monte-Carlo modelling of efficiency function Ta-ore vs Sand 5,00E-02 4,00E-02 Reihe1 Reihe2 Efficiency 3,00E-02 2,00E-02 1,00E-02 0,00E Energy [kev}

21 Validation of efficiency function

22 Validation of efficiency function

23 Validation of peak fit results E r e i g n i s s e Energy [kev]

24 Validation of peak fit results

25 Validation of peak fit results Energy [kev] FWHM Events Energy [kev] FWHM Events ,2 1,6 1,4 7 2,1 0,5 0,4 1,3 0,5 0,8 0,8

26 Time evolution of activity Example of Ra extraction from geothermal facilities D. Degering: Private communication from SAAGAS meeting september, 2010 Batemann, H. 1910, Solution of a System of Differential Equations Occuring in the Theory of Radioactive Transformations, Proc. Cambridge Philos. Soc. 15, Decay Engine, t/application/fulldecay.a spx Degering, D., Köhler, M., SAAGAS meeting, Sept. 2010

27 True Coincidence γ- γ-coincidence X-ray- γ-coincidence γ-β-coincidence More:.. Inhomogenities Input: treatment of material and sample

Gamma Analyst Performance Characteristics (MDAs)

Application Note Gamma Analyst Performance Characteristics (MDAs) Introduction With so much attention being given to environmental issues, the process of sample characterization is challenging today s