Proposal for high sensitive measurementsProposal for high sensitive measurementsof of 238238U and U and 232232Th with NAATh with NAA

Ezio PrevitaliEzio PrevitaliINFN Sez. MilanoINFN Sez. Milano

Milano-Bicocca UniversityMilano-Bicocca University

ILIAS: JRA1 3rd General MeetingILIAS: JRA1 3rd General MeetingParis 14th February 2006Paris 14th February 2006

Approaches in Low Contamination measurements

Bulk measurements: rays spectroscopy with HPGeICP-MS (Inductive Coupled Plasma – Mass Spectroscopy)NAA (Neutron Activation Analysis)......

What is considered Low Contamination?For future 0 decay experiments we consider for some materials:

232Th < 10-12 g/g (< 10 mBq/kg)238U < 10-12 g/g (< 50 mBq/kg)

Surface measurements:Cryogenic detectorsSurface barrier detectors LA-MS (Laser Ablation – Mass Spectroscopy)Large area gas ionization chamber......

Intermediate measurements:Radon emanation from surfaces.....

Bulk Contamination

rays spectroscopy HPGerays spectroscopy HPGe Neutron Activation AnalysisNeutron Activation Analysis

mainly on solids solids and liquids

sensitivity on daughters sensitivity on primordial

huge amount of materialsfew tens of kg

moderate amount of materialsfew tens of g

long running time measurementfew months

medium running time measurementfew weeks

well established technique technique under development

complementary approach

NAA status report

Borexino:very sensitive measurements on liquids (scintillators and water)

238U 232Thsensitivity for scintillator <9.4 10-17 g/g <2.4 10-15 g/gsensitivity for nylon 2.1 10-12 g/g 5.1 10-12 g/g

Majorana:measurements on electroformed copperrequest sensitivity for 232Th 10-14 g/gresults (??)

CUOREmeasurements on copper and lead shieldsmeasurements on small parts of CUORE detector

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 Sv/h!!! measurement was done in Pavia and Milano (single and coincidence)

Limit on 232Th (1 :<10-10 g/g

Our goal is:<10-12 g/g

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 Sv/h

Limit on 232Th (1 ):<8.5 10-12 g/g

we need to chemically separate

copper samplesto reduce activity

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 Sv/h

strong reduction of Cu and Co sourcesefficiency on 232Th larger than 96%

preliminary measurements on “diluted sample” was done in Paviagamma ray spectroscopy with HPGe (03-02-06)

Limit on 232Th (1 ):< 9 10-13 g/g

we need to further separatecopper samples

NAA on copper (future)

During next weeks: Copper sample will be chemically dissolved again:

Nitric acid will be used for dissolve samplesFluoridric acid will be added to increase migration in solution

Various separation methods will be tested Chemical precipitationExtraction of actinides using organic compoundsSeparation in chemical “columns”

High sensitivity radioactive measurements on extracted solutionsPreliminary 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• ...........

NAA copper byproduct

h ~ 4.7 mm

d ~ 5.8 mm

mt

ms

(1 m) ~ 900

10-8 Bq/cm2 1.1 10-9 g/g for 1 m depth 1.3 10-12 g/g volume

Actually our sensitivity on 232Th contamination on surfaces is:< 10-8 Bq/cm2 for 1 m depth

With a specific chemical treatment we can strongly improve this limits

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 samplesIrradiation at TRIGA reactorPreliminary analysis with HPGe spectroscopyChemical treatments for select actinidesMeasurement of solutions

In <5 days

NAA on lead preliminary results

Limits on concentration in g/g232Th 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

NAA on some materials

For small mass samples it is difficult to obtain the necessary limitsWe 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......

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 (??)

NAA working activity

People involved:A. Borio, A. Salvini

LENA and University of PaviaM. Clemenza*, E. Previtali

University of Milano-Bicocca and INFN Milano*actually under contract with Zaragoza University

Formal agreement between:University of Milano-BicoccaUniversity of PaviaLENA LaboratoryINFN

for R&D on high sensitivity NAA

Now we pay half price for the use of the TRIGA reactor!!!!

NAA working activity

During next months:a better definition of chemical treatmentsoptimization 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 methodsTest of electrodeposition technique for activated measurements

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

For chemical treatments some consumable are necessary:Acids, Organic com., ... ~6 k€Vials, baker,... ~5 k€Resins, ... ~7 k€

Reactor cost for irradiation: ~18 k€

For short living nuclide a new semiautomatic system is neededCask container ~20 k€Semiautomatic system ~20 k€

Electrodeposition system: ~12 k€

“Hot” laboratory (for high activity samples)...........???

Travel expenses: ~10 k€

What we ask to JRA1?

For future:

NAA included in FP7 activity in collaboration with other groups