Liquid Scintillation Counting as multi-nuclide screening method Evgeny Taskaev

Common approach – gross alpha/beta, gamma spectrometry: Screening for technogenic and natural radionuclides Common approach – gross alpha/beta, gamma spectrometry: Low counting efficiency - Limited knowledge on isotopic composition, including most toxic nuclides like 3-H, 90-Sr, Isotopes of Ra and Transuranics - High MDA - Radiochemical separation can be involved

Screening for technogenic and natural radionuclides Liquid scintillation counting: - Counting efficiency for a ~ 100% , for beta (> 100 кeV) ~ 100% - Threshold for beta counting – less than 3 кeV - Comparatively short time for sample preparation and counting - Low background – 0.01- 0.5 c/s - Low MDA ~ 10-20 mBq for beta and 5 mBq for alpha emitters (10 h counting with TRI-CARB 2550) - Possibility to estimate energy with resolution ~10 % for alpha emitters and - 5% (150-300 кэВ) when using PERALS system

Liquid scintillation counting Spectra are complicated, peaks are not resolved Counting efficiency depends on chemical composition of the sample

S. Malinovsky, A. Ermakov, I. Kashirin, et all. Scientific-Industrial Association “Radon”, Moscow, Russia Poland

Easy to use with minimal participation of operator SpectraDec(Beta) – software package for processing β and mixed α / β spectra from LS counters Software allows to determine activity of individual nuclides in a sample with several nuclides with overlapping spectra Mathematical modeling of real spectrum. Spectral data from counting of individual nuclides presented in sample are used to model real spectrum Modular structure makes software flexible for integration into another software and to addition of another modules if needed Easy to use with minimal participation of operator

Identification of radionuclides through modeling complex spectra using individual spectra data from nuclide library 3H 14C 137Cs 241Am 90Sr+90Y 4. 3.6 3.2 2.8 2.4 2. 1.6 1.2 0.8 0.4 0. 10 20 30 40 50 60 70 80 90

Creating nuclide library Addition of radionuclide to the library Reference source Radiochemical separation Preparation of quench set Preparation of quench set Counting Counting Mathematical «purification» of spectra Transformation of spectra to software format

Initial spectrum is transformed into groups For counters with linear ADC (TriCarb) – a quasi-arithmetic progression is used For counters with logarithmic ADC (Guardian) – linear combination Ra-226 and its progeny Initial spectrum Transformed spectrum

Individual spectra of 226Ra and its decay products Pb-210 Bi-210 Po-210

Set of quenched samples after transformation Tri-Carb 2550 Linear ADC Guardian 1440 Logarithmic ADC

Determination of Sr-90 in water Sr-90 with Sr-85 tracer Volume, L Nuclide Activity, Bq/sample Bq/m3 Error ± % 8 89Sr ≤ 0.006 ≤ 1.8e-3 - 90Sr 0.021 6.6e-3 29

A90Sr = 245 ± 90 Bq/kg A85Sr = 0.42 Bq in each sample, m soil = 10 g Determination of Sr-90 in soil using Sr-85 tracer 85Sr 90Sr 90Y 85Sr 90Sr 90Y A90Sr = 245 ± 90 Bq/kg A90Sr = 5.2 ± 2.2 Bq/kg A85Sr = 0.42 Bq in each sample, m soil = 10 g

Sr-90 in particulate filter Activity, Bq/sample Error, ± % 89Sr 1.83 3 90Sr 0.16 11

Blind sample spectrum send by Analytics NIST-NEI 1318-12 Pu-239 18.88 Bq/g Pu-241 922.2 Bq/g Am-241 254.9 Bq/g Cm-244 194.4 Bq/g Am-241 Pu-241 Cm-244 Pu-239

Blind sample spectrum send by Analytics H-3 NIST-NEI 1743-7 Fe-55 C o u n t s Ni-63 H-3, Fe-55, Ni-63 G r o u p s

Blind sample spectrum send by Analytics H-3, Tc-99 and Cs-137

Blind sample spectrum send by Analytics H-3, Tc-99 and Cs-137

Blind sample spectrum send by Analytics H-3, Tc-99 and Cs-137

Blind sample spectrum send by Analytics Activity, Bq added found H-3 C o u n t s Tc-99 H-3 714 701 Cs-137 Tc-99 404 390 Cs-137 267 301 G r o u p s

Conclusion SpectraDec(Beta) Enhances LSC capabilities for determination of individual nuclides in complex mixtures Allows to simplify sample prep procedures for many nuclides Combined with simple radiochemical separation and extractive cocktails makes LSC method excellent tool for screening

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