Budget Uncertainty and Minimum Detectable Concentrations for the INAA Laboratory of the ETRR-2

Transcription

1 Budget Uncertainty and Minimum Detectable Concentrations for the INAA Laboratory of the ETRR2 M.Y. Khalil and Kh.. A. Elsakhawy

2 CONTENTS Accreditation of INAA Lab What we wanted to do The ETRR2 What have been done What have we got Conclusion

3 Accreditation Management Requirements: organization chart of the laboratory, quality assurance system, document control, review of requests, tenders and contracts, purchasing services and supplies, service to the client, corrective action, preventive action, control of records.

4 (Accreditation) Technical Requirements: personnel training, environmental conditions, method validation, equipment, estimation of uncertainty of measurements, measurement traceability, sampling, assuring the quality of test and calibration results, reporting the results

5 What we wanted to do To fulfill some of the technical requirements for accreditation of ETRR2 Instrumental Neutron Activation Analysis (INAA) laboratory Estimate the budget uncertainty Traceability measurements (Minimum Detectable Concentration)

6 ETRR2 Main Neutronic Parameters of the ETRR2 2 Core Fuel loading (MTRplate fuel type) Average core cycle length Core maximum thermal flux Average power density Maximum power peaking factor 29 fuel assembly each contain 19 plates 19 full power days 2.3x10 14 n/cm 2.sec 140 W/cm

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8 ETRR2 2 Utilization Neutron Radiography Activation Analysis Isotopes Production Cold Neutrons Production BNCT Silicon Doping

9 What have been done

10 Apparatus High pure germanium detector (HPGD): Relative efficiency of the detector is 100% Energy resolution(fwhm) at Co60 line 1.33 MeV is 2.1 Cooling with liquid nitrogen at temperature (186C( ). ETRR2 2 as a neutron sources: 1 rabbit system ( short irradiation). 2 irradiation grid position (long irradiation).

11 Techniques Relative method Sample and element standards are irradiated simultaneously Absolute method In this case the thermal and epithermal neutron flux must be carefully measured, and their detector efficiency must be very well known K0 method The rate of production of radioactive atoms from stable atoms of interest is related to the activation rate of gold through the socalled k0constant

12 Materials A Reference materials: rocktype P1, CRM, Both from the proficiency test study under the AFRA IV7 7 project B Flux monitors: Gold ( pure and diluted with aluminum (gold 0.1% and the aluminum 99.9%) ) Zirconium (99.99%). Nickel (99.99). Cadmium ( cover sheet and tube 99.99%).

13 Blanks Were used to: 1. Eliminates the Effect of instrumental background, 2. Determines the spectrum baseline, which is the sum of the instrumental background and any signal due to interfering species, 3. Eliminates the Effect of contamination or the impurities in the vials

14 Method Short irradiation( Rabbit system) Sample Irradiated for 60 second with aid of pneumatic facility. Blank polyethylene vial used to control the effect of the background.

15 Long irradiation All samples divided into 4 aluminum cans The cans placed in a sample holder and lowered into the irradiation position. The samples were irradiated for 4 hour and 35 minutes. The sample were kept in hot cell to reach safe handling level.

16 Irradiation grid

17 What have we got

18 Samples irradiated in thermal column Irradiation time, sec Cooling time, hr Counting time, sec Dead time % SAMPLE #1 Gold #1 SAMPLE #2 Gold #2 SAMPLE #3 Gold #3 SAMPLE #7R Gold #7 SAMPLE #8R Gold #8 Sample#9R Gold #

19 Net peak area Element Isotope Peak energy Branching ratio Net peak area Sample #1 Manganese Sodium Potassium Mn56 Na24 K ± ± ±60 60 Gold#1 pure GOLD Au ± Sample #7 R Manganese Sodium Mn56 Na ± ±437 Potassium K ±100

20 Element Isotope Peak energy Branching ratio Net peak area Sample #2 Gold #2 Sample #8 R Sample #3 Gold#2 Sample #9R Gold Cd Manganese Sodium Potassium pure GOLD Manganese Sodium Potassium Manganese Sodium Potassium pure GOLD Manganese Sodium Potassium GOLD +Cd+ Mn56 Na24 K42 Au198 Mn56 Na24 K42 Mn56 Na24 K42 Au198 Mn56 Na24 K42 Au ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±296

21 Samples irradiated in irradiation grid Ist counting 2 nd counting 3 rd counting vail Tirr Td Day Tc Sec Tdead % Td Day Tc Sec Tdead % Td day Tc Sec Tdead %

22 Element Calcium Net peak area Isotope Ca Peak energy KeV Branching ratio % 67.9 Net peak area 10457± Sample #5 Sample #11 R Cobalt Chromium cesium Iron rubidium Calcium Cobalt Chromium cesium Iron rubidium Au+Al Nickel Co Cr Cs Fe Rb Ca Co Cr Cs Fe Rb Au198 Co58 Zr ± ± ± ± Zirconium Zr ± ± ± ± ± ± ± ± ± ± ±716

23 The relative standardization The test and reference samples were irradiated simultaneously or sequentially in short half life under the same conditions. The concentration of the elements of interest calculated by caparison of the activity between the sample and reference standard ard. C unk N m (1 e (1 e λtd std λtm p( unk ) std = Cstd λtd unk λt N p( std ) munk e e std ) m unk )

24 Average concentrations: Element Mn54 Na24 K42 Sc47 Co60 Cr51 Fe59 Rb86 Cs134 Concentration mg/kg g/kg g/kg g/kg mg/kg mg/kg g/kg mg/kg 1.85m g/kg

25 Uncertainty in relative standardization

26 Uncertainty sources Mn54 U mass S U mass Std U net area S U net area Std U flx 0.8 U geometry difference 3.95 U pulse pile up Na K Sc Co Cr51 Fe NON Rb Cs

27 Expanded uncertainty Element Mn54 Na24 K42 Sc47 Co60 Cr51 Fe59 Rb86 Cs134 Expanded uncertainty Concentration ± ± ± ± ± ± ± ± ±0.123

28 Minimum detectable concentration Element Sc47 Co60 MDC Cr51 Cs134 Fe59 Mn54 Na24 Rb86 K

29 The absolute standardization Sample and flux monitors are irradiated simultaneously. The neutron flux measured from the activity of the flux monitors. The concentration computed from the activation equation: Np λm C= mθ Nβ ε( σφ + I φ)( 1 e v i i t ) e (1 e * λt irr λt d λtm e )

30 Neutron flux at thermal column Flux Sample #1 Sample #2 Sample #3 Thermal 2.90E E E+11 Epithermal 2.6 E+8

31 Neutron flux in irradiation grid Flux Thermal Epithermal Fast Sample # E E E+12 Sample # E E E+12

32 Average concentrations Element Mn54 Na24 K42 Co60 Cr51 Fe59 Cs134 Rb86 Concentration 541 mg/kg g/kg g/kg mg/kg m g/kg g/kg mg/kg mg/kg

33 Uncertainty in absolute standardization

34 Uncertainty sources Uflx M U S M Uflx Conc. Uflx Net area U S Net area U geometry diff. U pulse pile up U effici ency Mn Na K Co Cr Cs Fe Rb

35 Expanded Uncertainty Element Mn54 Na24 K42 Co60 Cr51 Fe59 Cs134 Rb86 Expanded uncertainty Concentration ± 34.6 mg/kg ± g/kg ± g/kgg ± mg/kg ± 1 m g/kg ± g/kg ± mg/kg ± mg/kg

36 Minimum detectable concentration Element Co60 Cr51 Cs134 Fe59 Mn54 Na24 Rb86 K42 MDC

37 The k 0 IAEA standardization software. Single comparator standardization. The rate of production of radioactive atoms from stable atoms of interest is related to the activation rate of gold through the socalled s k0constant. relative production rate depends on the specific irradiation facilities and gammaray detectors used Detector calibration. Facility characterization. Sample analysis k 0 = M M C θ aσ aβ a θ σ β a c c c

38 Average concentration Element Ca Co Cr Cs Fe Mn Na Rb K Concentration 32.27± g/kg 11.65± mg/kg 31.81±4.14 mg/kg 1.755±0.31 mg/kg 34.91± g/kg 600.1±20.40 mg/kg 30.24±1.54 g/kg 40.81± mg/kg 13.28±5.4 g/kg MDC, ppm

39 Conclusions The uncertainty budget in the relative standardization ranges from 2% to 11%. The uncertainty budget in k0method ranges from 3% to 15%. uncertainty budget in the absolute method ranges from 6% to 21%. The MDC in relative standardization is the lowest and then the k0iaea standardization and the absolute standardization is the largest MDC

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