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Proposal for high sensitive measurements of 238 U and 232 Th with NAA

Proposal for high sensitive measurements of 238 U and 232 Th with NAA. Ezio Previtali INFN Sez. Milano Milano-Bicocca University. ILIAS: JRA1 3rd General Meeting Paris 14th February 2006. Approaches in Low Contamination measurements. What is considered Low Contamination?

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Proposal for high sensitive measurements of 238 U and 232 Th with NAA

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  1. Proposal for high sensitive measurements of 238U and 232Th with NAA Ezio Previtali INFN Sez. Milano Milano-Bicocca University ILIAS: JRA1 3rd General Meeting Paris 14th February 2006

  2. Approaches in Low Contamination measurements What is considered Low Contamination? For future 0nbb decay experiments we consider for some materials: 232Th < 10-12 g/g (< 10 mBq/kg) 238U < 10-12 g/g (< 50 mBq/kg) Bulk measurements: g rays spectroscopy with HPGe ICP-MS (Inductive Coupled Plasma – Mass Spectroscopy) NAA (Neutron Activation Analysis) ...... Surface measurements: Cryogenic detectors Surface barrier detectors LA-MS (Laser Ablation – Mass Spectroscopy) Large area gas ionization chamber ...... Intermediate measurements: Radon emanation from surfaces .....

  3. Bulk Contamination g rays spectroscopy HPGe Neutron Activation Analysis mainly on solids solids and liquids sensitivity on daughters sensitivity on primordial huge amount of materials few tens of kg moderate amount of materials few tens of g long running time measurement few months medium running time measurement few weeks well established technique technique under development complementary approach

  4. NAA status report Borexino: very sensitive measurements on liquids (scintillators and water) 238U 232Th sensitivity for scintillator <9.4 10-17 g/g <2.4 10-15 g/g sensitivity for nylon 2.1 10-12 g/g 5.1 10-12 g/g Majorana: measurements on electroformed copper request sensitivity for 232Th 10-14 g/g results (??) CUORE measurements on copper and lead shields measurements on small parts of CUORE detector

  5. Our goal is: <10-12 g/g NAA on copper (September 2005) • NAA for copper measurements: • the plan is to measure 232Th contamination with high sensitivity • selected sample is a small bar of 9 g (Outokumpu) • 1 week irradiation @ TRIGA reactor of Pavia • 3 weeks stored in the irradiation channel for reduce the activity • after 1 month  activity was 100 mSv/h!!! • measurement was done in Pavia and Milano (single and coincidence) Limit on 232Th (1 s): <10-10 g/g

  6. we need to chemically separate copper samples to reduce activity NAA on copper (January 2006) • New irradiation started before Christmas: • dedicated to measure 232Th contamination with high sensitivity • selected sample is 18x8 bars of 1.1 g (Outokumpu) total copper mass is 162.5 g • 20 hours irradiation @ TRIGA reactor of Pavia (15-12-05) • 28 days stored in the irradiation channel for reduce the activity • preliminary measurements on “solid sample” was done in Pavia gamma ray spectroscopy with HPGe (12-01-06) total activity 200 mSv/h Limit on 232Th (1 s): <8.5 10-12 g/g

  7. NAA on copper (Febbruary 2006) • Chemical treatment for the previous samples: • dedicated to measure 232Th contamination with high sensitivity • separation was done with a chemical “column”) we plan to reduce the activity reducing low Z elements • activity of the separated samples 1 mSv/h strong reduction of Cu and Co sources efficiency on 232Th larger than 96% • preliminary measurements on “diluted sample” was done in Pavia gamma ray spectroscopy with HPGe (03-02-06) Limit on 232Th (1 s): < 9 10-13 g/g we need to further separate copper samples

  8. NAA on copper (future) • During next weeks: • Copper sample will be chemically dissolved again: Nitric acid will be used for dissolve samples Fluoridric acid will be added to increase migration in solution • Various separation methods will be tested Chemical precipitation Extraction of actinides using organic compounds Separation in chemical “columns” • High sensitivity radioactive measurements on extracted solutions Preliminary test in Pavia using a standard HPGe (30% int. efficiency) Final measurements in Milan using a well HPGe (65% int. effiiciency) Coincidence measurements with 2 HPGe detectors is planned • Future developments: • Optimization of the samples preparation • Selection of chemical procedure with evaluation of efficiency • 238U chain analysis • ...........

  9. d ~ 5.8 mm mt ~ 900 (1 mm) h ~ 4.7 mm ms NAA copper byproduct 10-8 Bq/cm2 1.1 10-9 g/g for 1 mm depth  1.3 10-12 g/g volume Actually our sensitivity on 232Th contamination on surfaces is: < 10-8 Bq/cm2 for 1 mm depth With a specific chemical treatment we can strongly improve this limits

  10. NAA on lead Using NAA we try to analyze different types of lead: Roman Plumbum Standard (used in Pavia reactor) Procedure will be the same as copper: Preparation of samples Irradiation at TRIGA reactor Preliminary analysis with HPGe spectroscopy Chemical treatments for select actinides Measurement of solutions  In <5 days

  11. NAA on lead preliminary results Limits on concentration in g/g 232Th 238U Roman lead (9.2g) <5.7 10-10 <1.0 10-9 Plumbum lead (11.5g) <5.6 10-10 <7.0 10-9 Standard lead (4.1g) <2.9 10-10 <2.7 10-9 Sensitivity limitation comes to: presence of some contaminants in samples (..Sb) irradiation procedure needed for 238U analysis Chemical treatments of samples will be start soon

  12. NAA on some materials For small mass samples it is difficult to obtain the necessary limits We measure some small samples to evaluate the contamination • NAA: [ppt] 232Th 238U • Epoxy glue < 200 < 800 • Si chips < 50 <170 • High Vacuum Grease < 5 104 < 103 • ...... Other materials will be measured soon......

  13. Teflon puzzle • NAA: [ppt] 232Th 238U • Berkeley I 70 • Berkeley II 300 <200 • Milano I 140 <150 • Milano II 1500 78 • Milano III 235 <90 • Gerda 3100 60 • HPGe: [ppt] • LNGS <40 <30 • Bolometers: [ppt] • TeO2 <630 <380 232Th results are compatible with ~ 100 ppt contamination for a broken chain (??)

  14. NAA working activity People involved: A. Borio, A. Salvini LENA and University of Pavia M. Clemenza*, E. Previtali University of Milano-Bicocca and INFN Milano *actually under contract with Zaragoza University Formal agreement between: University of Milano-Bicocca University of Pavia LENA Laboratory INFN for R&D on high sensitivity NAA Now we pay half price for the use of the TRIGA reactor!!!!

  15. NAA working activity During next months: a better definition of chemical treatments optimization of the sample preparation improvement in spectroscopy Limits for 232Th for copper (and possibly for lead) < 10-13 g/g Program definition for other elements: 238U, K, ......, Ra Improvement in coincidence methods Test of electrodeposition technique for a activated measurements

  16. What we ask to JRA1? We need support for the NAA R&D program 2 years program It is necessary to have more man power: a fellowship contract can help very much Reactor cost for irradiation: ~18 k€ For chemical treatments some consumable are necessary: Acids, Organic com., ... ~6 k€ Vials, baker,... ~5 k€ Resins, ... ~7 k€ For short living nuclide a new semiautomatic system is needed Cask container ~20 k€ Semiautomatic system ~20 k€ Electrodeposition system: ~12 k€ “Hot” laboratory (for high activity samples)...........??? Travel expenses: ~10 k€

  17. What we ask to JRA1? For future: NAA included in FP7 activity in collaboration with other groups

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