NUCLEAR DATA FOR NEUTRON ACTIVATION ANALYSIS: NEEDS, DETERMINATION, STATUS. Frans De Corte

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1 Workshop on Nuclear Data for Activation Analysis 7 18 March 2005 Miramare Trieste, Italy NUCLEAR DATA FOR NEUTRON ACTIVATION ANALYSIS: NEEDS, DETERMINATION, STATUS Frans De Corte Laboratory of Analytical Chemistry, Institute for Nuclear Sciences Ghent University Proeftuinstraat 86 B 9000 Gent, Belgium frans.decorte@ugent.be

2 When considering the simple equation (in relative standardization ) for obtaining concentrations via reactor neutron activation analysis: ( ) conc = a ( N p / t m SDCW ) ( N p / t m SDCw ) s a with: a - analyte s - co-irradiated standard N p - net peak area t m measuring time S = 1-exp(-λt irr ); t irr irradiation time D = exp(λt d ); t d decay time C = [1-exp(-λt m )]/ λt m W sample mass w mass of standard WHY ARE NUCLEAR DATA (OTHER THAN THE HALF-LIFE) NEEDED?

3 NEED FOR NUCLEAR DATA IN NAA pre-irradiation: feasibility of determination Advance prediction post-irradiation: interpretation of measured gamma-spectra and identification of isotopes/elements parametric standardization protocols: absolute, k 0, --- corrections: spectral and reaction interferences neutron self-shielding, gamma-attenuation burn-up

4 WHICH NUCLEAR DATA? see fundamental equation of NAA Høgdahl formalism G th φ th σ 0 + G e φ e I 0 ( α ) = N A M θ γε p N p / t m wsdc σ ms -1 (n,γ) cross section; I 0 (α) - resonance integral for non-ideal (1/E 1+α) epithermal flux energy dependence; measurement of α requires nuclear data; φ th, φ e - thermal resp. epithermal neutron flux; determination requires nuclear data; G th, G e - thermal resp. epithermal neutron self-shielding factor; determination requires nuclear data.

5 WHICH NUCLEAR DATA? see fundamental equation of NAA Høgdahl formalism G th φ th G I ( α ) M atomic weight; N A Avogadro s number; θ - isotopic abundance; σ 0 + e φ e 0 = N A M θ γε p N p / t m wsdc ` γ - absolute gamma-intensity; ε p - peak detection effficiency, with correction for gamma-attenuation; requires nuclear data. N p /t m - (net) peak count rate; correction for true-coincidence, reaction & spectral interferences and burn-up requires nuclear data. N p = (N p ) meas /COI true-coincidence correction factor requires gamma-intensities and internal conversion coefficients

6 N p = (N p ) meas /COI COI(A) = 1 L(A) [L( A ) = probability for loss of A] A B γ L (A) = probability that A is followed by transition B = a B (branching ratio of B) x probability that gamma B is emitted = 1 / (1 + α t,b )[α t = total IC coefficient] or IC x probability that gamma B gives a total or partial energy deposition in the detector = ε t,b [total detection efficiency] = a B. ε t,b / (1 + α t,b )

7 NEED FOR NUCLEAR DATA IN NAA pre-irradiation: feasibility of determination N Based on estimation of detectability of analyte peak in gamma-ray spectrum of irradiated matrix, via calculation, for analyte and matrix elements, of p = N A θ M γ wt m SDC [ φ th σ 0 + φ e I 0 ] ε p E.g. : Can phosphorus be determined in semiconductor silicon? Can iodine be determined in milk powder? Can selenium be determined in human blood serum? Can uranium be determined in loess? Can lanthanum be determined in estuarine sediment?

8 APCP NAAPRO

9 NEED FOR NUCLEAR DATA IN NAA post-irradiation: interpretation of measured gamma-spectra and identification of isotopes/elements Example: Peak at ± 0.5 kev is found in gamma-spectrum Search gives 2 possibilities: kev of 198 Au, or kev of 143 Ce if 198 Au: peak at kev should be seen if 143 Ce: peak at kev should be seen check peak ratios: (γε p ) peak1 / (γε p ) peak2

10 NEED FOR NUCLEAR DATA IN NAA parametric standardization protocols: ABSOLUTE STANDARDIZATION (conc ) a = N A M θ a a γ a ( N / Wt SDC ) p [ ( )] G th,aφ thσ 0 + G,a e,aφ ei 0 α ε,a p, a m a (conc ) combined with co-irradiation of neutron flux monitor (m): a = ( N ) p / Wt msdc ( N / wt SDC ) p m a m M M a m θ θ m a γ m γ a σ σ 0,m 0,a ( α) ( α) [ G ] th,mf + G e,mq 0,m ε p,m [ G ] th,af + G e,aq 0,a ε p, a with f = φ th / φ e Q 0 (α) = I o (α) / σ 0

11 NEED FOR NUCLEAR DATA IN NAA parametric standardization protocols: (conc ) a k 0 -STANDARDIZATION = ( N ) p / Wt msdc ( N / wt SDC ) p m a m M M a m θ θ m a γ m γ a σ σ 0,m 0,a ( α) ( α) [ G ] th,mf + G e,mq 0,m ε p,m [ G ] th,af + G e,aq 0,a ε p, a (conc ) a = ( N ) p / Wt m SDC a 1 ( N / wt SDC ) k () a p m m 0,m ( α ) ( α ) [ G ] th,m f + G e,m Q 0,m ε [ G ] th,af + G e,aq 0,a ε p, a p,m With k 0,m (a) defined as: k () a = 0,m M M a m θ θ m a γ γ a m σ σ 0,a 0,m

12 I 0 ( α) = I σ E r α σ α ( E = 0.55eV) ( 2α + 1) Cd 0.1eV α Q 0 ( α) = Q E r α α ( E = 0.55eV) ( 2α + 1) Cd.1eV α Er = effective resonance energy

13 α from Cd-ratio for multi-monitor method (implicit) log minus α is slope of straight line when plotting: ( F R 1).Q ( α) Cd,i Cd,i E α r,i 0,i.G e,i / G th,i versus log E r,i Required: F Cd Cd transmission factor for epithermal neutrons Q 0, Er and F Cd

14 to be updated

15 α from bare triple monitor method (implicit equation) G ( ) ( ) e,1 ( ) e,2 a b.q α a.q α + b.q ( α ) 0,1 G th,1 0,2 G G th,2 0,3 G G e,3 th,3 = 0 a = 1 A A sp,2 sp,1 k k 0,Au 0.Au () 1 () 2 ε ε p,1 p,2 1 b = 1 A A sp,3 sp,1 k k 0,Au 0.Au () 1 () 3 ε ε p,1 p,3 1 Required: A sp = N p / t m SDCw k 0, Q 0 and E r

16 f from Cd-ratio method: f = Q 0 ( ) [ ] α. F R 1 Cd Cd.G e / G th R Cd = A sp / ( ) A sp Cd Required: Q 0, Er and F Cd

17 f from bare dual monitor method: f = G e,1 k k 0,Au 0,Au G () 1 () 2 th,2 ε ε A A p,1 p,2 sp,1 sp,2 Q 0,1 G ( ) sp,1 α G Q ( α) th,1 k k 0,Au 0,Au e,2 A A sp,2 () 1 ε p,1 () 2 ε p, 2 0,2 Required: k 0, Q 0 and Er

18 NEED FOR NUCLEAR DATA IN NAA parametric standardization protocols: k 0 -STANDARDIZATION Experimental measurements of k 0 -factors: k 0,m () a = ( N ) p / wt m SDC ( N / wt SDC ) p m a m ( α ) ( α ) [ G ] th,m f + G e,m Q 0,m ε [ G ] th,af + G e,aq 0,a ε p, a p,m

19 Experimental measurement of k 0 -factors: A priori outlined methodology: Parallel but independent experimental measurement of k 0, Q 0, etc. at INW, Gent and KFKI, Budapest Detection and elimination of systematic errors

20 Experimental measurements of k 0 -factors: INW, Gent and KFKI, Budapest: parallel but independent measurements different target preparation different reactors/irradiation sites ( neutron thermalization) different Ge-detectors ( DT correction) different computer codes for gamma-spectrum analysis

21 Experimental measurements of k 0 -factors: Sample preparation Isotope E γ, kev Measured k0,au (uncertainty in %) KFKI WWR-M Channel: INW THETIS Channel: k0,au recommended (uncert.,%) MILA f = 35 CSÖPI f = 18 3 f = f = 72 KFKI: 1mg NaCl on Al-foil; pellet 6.4mm diam. x 0.2 mm 24 Na DT correction: pulser Spectr. anal. : Hypermet DT correction: DTS Spectr. anal. : Seqal INW: Na2CO3 powder in PE vial; 20mg (Ch.3); 50mg (Ch.15) E-2(2.2) 4.60E-2(1.6) 4.74E-2(2.4) 4.74E-2(1.6) 4.61E-2(2.5) 4.56E-2(1.8) 4.65E-2(1.8) 4.59E-2(0.5) 4.68E-2(0.6) 4.62E-2(0.9)

22 Experimental measurements of k 0 -factors: Measurement of k 0, Q 0, etc.: later contributions/co-operations: LNETI - Sacavém Atominstitut - Wien National Laboratory - Risø SCK - Mol + IRMM - Geel IJS - Ljubljana (+Podgorica) KFA Jülich TUM - Garching DSM - Geleen

23 Choice of comparator/monitor in k 0 -NAA: 197 Au(n,γ) 198 Au, E γ = kev tabulation of k 0,Au (a) Simple conversion: k o,m (a) = k 0,Au (a) / k 0,Au (m) IRMM/Geel - INW/Gent co-operation: NIM A, 1991: Aluminium-gold reference material for the k 0 -standardisation of neutron activation analysis IRMM-530 CRM Al-(0.100±0.002)%Au foil or wire (accuracy-checked at KFKI; increases traceability)

24 Sample preparation Isotope E γ, kev Measured k 0,Au (uncertainty in %) KFKI WWR-M Channel: INW THETIS Channel: k 0,Au recommended (uncert.,%) 15/2 f = 30 17/2 f = 20 3 f = f = 72 KFKI: 20µg CsNO 3 (in H 2 O) on Al-foil; pellet 6.4mm diam. x 0.2 mm 134 Cs DT correction: pulser Spectr. anal. : Hypermet DT correction: DTS Spectr. anal. : Seqal Intern. Compar.: 69m Zn INW: CsCl (in H 2 O) [+Zn (in HNO 3 ] on W41; 0.7mg (Ch.3); 1.7mg (Ch.15); pellet 10 mm diam. x 4 mm E-1(1.0) 4.21E-1(0.7) 4.75E-1(2.1) 4.18E-1(1.8) 4.93E-1(0.3) 4.26E-1(0.4) 4.53E-1(0.2) 3.93E-1(0.5) 4.76E-1(2.0) 4.15E-1(2.0)

25 (conc ) x G G a th,m th,a = g g m a ( N ) p / Wt msdc a 1 ( N / wt SDC ) k () a p ( T ) + G.r( α ) T / T.s ( α ) p,m ( T ) + G.r( α ) T / T.s ( α ) p, a n n m r,m r,a m n 0,m n 0 0 x 0,m 0,a ε ε

26 (conc ) x G G a th,m th,a = g g m a ( N ) p / Wt m SDC a 1 ( N / wt SDC ) k () a p ( T ) + G.r( α ) T / T.s ( α ) p,m ( T ) + G.r( α ) T / T.s ( α ) p, a n n m r,m r,a m n 0,m n 0 0 x 0,m 0,a ε ε g(t n ) ( ) Tn / T0 r α s 0 α ( ) α α = s Er.1eV s = 2Q / π Westcott g-factor; T n neutron temperature modified spectral index measure for epith./thermal cross section for 1/v cross sections (Westcott g = 1)

27 Detailed info on k 0 -NAA

28 General info on k 0 -NAA

29 NEED FOR NUCLEAR DATA IN NAA corrections: spectral interferences Se in presence of Hg: spectral interference: 74 Se(n,γ) 75 Se; E γ = kev 202 Hg(n,γ) 203 Hg; E γ = kev correction essentially requires gamma-intensity data U in loess: spectral interference: 238 U(n,γ) 239 U(β - ) 239 Np; E γ = 228.2, kev 235 U(n,f) 132 Te; E γ = kev correction requires both cross section/resonance integral and gamma-intensity data

30 NEED FOR NUCLEAR DATA IN NAA corrections: reaction interferences P in Si: 31 P(n,γ) 32 P 2 nd order interference: 30 Si(n,γ) 31 Si(β - ) 31 P(n,γ) 32 P Na in presence of Al: Threshold interference 23 Na(n,γ) 24 Na 27 Al(n,α) 24 Na La in estuarine sediment: fission reaction interference: 139 La(n,γ) 140 La 235 U(n,f) 140 Ba(β - ) 140 La correction essentially requires cross section/resonance integral data

31 NEED FOR NUCLEAR DATA IN NAA corrections: neutron self-shielding Bromine (~75%) in flame retardant: possibility of thermal and epithermal neutron self-shielding thermal shielding correction: contains <<exp(-σ abs N)>> terms σ abs =Σ(θ i σ 0,i )/100 elemental absorption cross section; N - nuclei.cm -3 epithermal shielding correction: more complex calculation, based on resonance parameters correction essentially requires cross section/resonance data

32 NEED FOR NUCLEAR DATA IN NAA corrections: gamma-attenuation U in loess: 238 U(n,γ) 239 U; E γ = 74.7 kev if voluminous matrix: possibility of gamma-attenuation [also: spectral interference possible from 75.0 kev Pb KX ray (Pb-castle)] Gamma-attenuation correction: contains <<exp(-µd)>> terms µ linear absorption coefficient (total minus coherent scattering); d thickness of absorbing layer correction essentially requires gamma-absorption coefficients

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35 NEED FOR NUCLEAR DATA IN NAA corrections: Burn-up E.g.: Au at high fluxes / long irradiation times 197 Au(n,γ) 198 Au(n,γ) 199 Au high σ 0 and I 0 values Correction requires cross sections / resonance integrals

36 Sources of Nuclear Data Atomic Weights and Isotopic Abundances

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39 ALSO: M AND θ FROM OTHER DATA COMPILATIONS

40 Sources of Nuclear Data: General Activation and Decay

41 Welcome to the IAEA Nuclear Data Centre

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47 Sources of Nuclear Data: General Activation

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49 Chart of the Nuclides

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52 Zn-68(n,gamma) Mughabghab et al., 1981 (BNL)

53 CRC Handbook of Chemistry and Physics

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55 Mughabghab, 2003

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57 Jef Report 14, 1994

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60 Nuclear Wallet Cards Search

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62 NuDat

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64 Westcott s 0 F. DE CORTE et al: JRNC, 179 (1994) mainly from C.H. WESTCOTT: Effective cross section values for well-moderated thermal reactor spectra Report CRRP-960 of the AECL, Nov 1, 1960 (reprinted 1962) J.I. KIM, E.M. GRYNTAKIS, H.J. BORN: Radiochim. Acta, 22 (1975) 20

65 F. De Corte et al: JRNC, 179 (1994)

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67 Holden, PAC 1999