The Preparation of Monitors and Comparators for k0-INAA using Primary Standard Solutions

P.S. Bedregal, V. R. Poma, M.S. Ubillus

Analytical Techniques Laboratory

Peruvian Institute of Nuclear Energy (IPEN)

7th International k0-Users’ Workshop 3-8 September 2017, Montreal, Canada

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Mathematical Model for concentration calculation:

Amount of comparator

Comparators and flux monitors are irradiated as metals in the way of wires or foils, (Au:IRMM-530, Zr)

There is the option to use primary standard solution.

The quality of the standards should be appropriate for their intended use.

The protocol lab is defined: Comparator: Na standard solution for irradiations 10s – 30min using the pneumatic transfer system: For short live radionuclides determination of any matrix and for short/intermediate/long live radionuclides for siliceous samples irradiation (e.g. clay, soils, sediments, etc.) PE capsule for irradiation

A B C D E F G H I

1 TN Be-01 Be-02 Be-03 Be-04 Be-05 Be-06 Be-07

2 GR-01 Be-08 CI-C2 NN-027NC-006 NN-028 BCF Be-09 GR-02

3 Be-10 Be-11 NN-027 AS-001 A-022 NC-008 A-010 Be-12 Be-13

4 Be-14 Be-15 A-007 A-017 CI-E4 A-021 A-015 Be-16 Be-17

5 Be-18 Be-19 A-019 NC-007 A-023 AS-005 A-008 Be-20 Be-21

6 GR-03 Be-22 CI-C6 NN-027 A-018 NN-029 CI-G6 Be-23 GR-04

7 CI-A7 Be-24 Be-25 Be-26 Be-27 Be-28 Be-29 Be-30 CI-I7

8 GR-05 GR-06 GR-07 GR-08 GR-09

TN

CI

Be Berilio (30)

GR

A Elemento combustible normal (CNEA)

AS Elemento combustible de control(NUKEM)

NN Elemento combustible normal, (NUKEM)

BCF Barra de control fina

Posiciones de irradiación (6)

Grafito (9)

Sistema neumático (1)

Comparator Zn standard solution for irradiations in the core of the reactor, to determine intermediate and long live radionuclides in biological samples:(e.g. tissues, environmental, plants, food, etc.) Aluminum capsule for irradiation

A B C D E F G H I

1 TN Be-01 Be-02 Be-03 Be-04 Be-05 Be-06 Be-07

2 GR-01 Be-08 CI-C2 NN-027NC-006 NN-028 BCF Be-09 GR-02

3 Be-10 Be-11 NN-027 AS-001 A-022 NC-008 A-010 Be-12 Be-13

4 Be-14 Be-15 A-007 A-017 CI-E4 A-021 A-015 Be-16 Be-17

5 Be-18 Be-19 A-019 NC-007 A-023 AS-005 A-008 Be-20 Be-21

6 GR-03 Be-22 CI-C6 NN-027 A-018 NN-029 CI-G6 Be-23 GR-04

7 CI-A7 Be-24 Be-25 Be-26 Be-27 Be-28 Be-29 Be-30 CI-I7

8 GR-05 GR-06 GR-07 GR-08 GR-09

TN

CI

Be Berilio (30)

GR

A Elemento combustible normal (CNEA)

AS Elemento combustible de control(NUKEM)

NN Elemento combustible normal, (NUKEM)

BCF Barra de control fina

Posiciones de irradiación (6)

Grafito (9)

Sistema neumático (1)

Flux Monitors: Multielement secondary standard solution was prepared for Lu – Co – Au Primary standard solution for Mo.

An aliquot of the standard is deposited

Hydraulic press

Pills of Comparator and flux monitors=13 mm diameter

The dispensing of the micropipette play an important role.

Evaluate the way of dispensing the standard solutions using a gravimetric determination of the aliquot and compare it with the volumetric one.

The mass of Na standard irradiate will be: w(g) · [Na+] µg/g e.g. w Na+= 0.20187 · 9994 w Na+= 2017.50 µg

Case 1. Preparation in a gravimetric form: An aliquot of 200 µL

Calibrate balance

Case 2. Preparation in a volumetric form: An aliquot of 200 µL was deposited on the disc of filter paper.

The micropipette was calibrated, according to Eppendorf SOP

n= 10 aliquots were weighed _ n = 0.20129 g

ZnVmL _

exp,

Z= depending of T°C and atmospheric pressure

Eexprandom = 0.22% Epermissible = 0.2%

Eexpsystematic = 0.64% Epermissible = 0.6 %

Case 2. Preparation in a volumetric form: An aliquot of 200 µL was deposited on the disc of filter paper.

T°C = 22 hPa = 1013 Z= 1.0033 µL/mg

VmL = 0.20195 wNa

+ = VmL ·δ [Na

+], g/mL

wNa+

g = 0.20296 wNa

+µg= 0.20296·9994 = 2028.38

Five replicates of NIST SRM 1633b – Coal Fly Ash Five replicates of NIST SRM 2711a– Montana Soil II

Pills of samples were prepared using Licowax/SRM, 1:3 W sample = 0.250 g

10 MW research reactor Open pool research reactor

Ti = 1800 s

SRM - Montana soil

SRM –Coal Fly Ash

Na comparator volumetric

Mo monitor volumetric

Multi monitor volumetric

Na comparator gravimetric

Mo monitor gravimetric

Multi monitor gravimetric

24 pills Φth = 2.2 ·1012 cm-2 s-1

Φe = 4.9 ·1010 cm-2 s-1

Irradiation to 6 MW

f=42, α=0.105, Tn= 77°C

f=49, α=0.075, Tn=80°C

f=50, α=0.083, Tn=80°C

f=38, α=0.118, Tn= 82°C

f=47, α=0.098, Tn= 82°C

f=40, α=0.111, Tn=80°C

Samples/Comparators

Samples/Comparators

Irradiation position parameters obtained in the capsule

0

0.5

1

1.5

2

2.5

3

3.5

As Ba Ce Co Cr Cs Fe Hf K La Lu Na Nd Rb Sb Sc Sm Sr Ta Tb Th U Yb Zn

En values and agreement SRM 1633b

Gravimetric Volumetric

En values

Figure 1

0

0.5

1

1.5

2

2.5

Ag As Ba Ce Co Cr Cs Fe Hf K La Lu Na Nd Rb Sb Sc Sm Sr Ta Tb Th U Yb Zn

En values and agreement SRM 2711a

Gravimetric Volumetric Agreement

Figure 2

The experimental mean of both methods were compared, using the statics |t| (8 degrees of freedom)

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The null hypothesis :both methods give the same results, H0 : µ1 = µ1

Verified if x1 and x2 are significantly different

The critical value t8=2.1 (P=0.05)

SRM 1633b SRM 2711a SRM 1633b SRM 2711a

|t| |t| |t| |t|

Ag 0.08 Nd 0.04 0.02

As 0.00 0.01 Rb 0.07 0.06

Ba 0.10 0.10 Sb 0.27 0.58

Ce 0.30 0.20 Sc 0.30 0.12

Co 0.21 0.10 Sm 0.15 0.09

Cr 0.26 0.10 Sr 0.22 0.07

Cs 0.12 0.07 Ta 0.14 0.17

Fe 0.20 0.15 Tb 0.12 0.61

Hf 0.15 0.08 Th 0.00 0.00

K 0.16 0.08 U 0.22 0.23

La 0.23 0.14 Yb 0.19 0.10

Lu 0.10 0.05 Zn 0.23 0.12

Na 0.22 0.20

Ele Ele

The null hypothesis is accepted to 5% There is no evidence that the gravimetric method of comparator and monitors preparation affect the mass

Uncertainty

Case 1. Gravimetric preparation

wµg ,c

[SRM – Na+]

Balance

Repeatability

Calibration

Quantity ValueStandard

uncertaintyUnits

Relative Std

uncertainty u(x)/x

Type

evaluationDistribution

m 2.028 8.73E-05 mg 4.30E-05 A normal

Conc. Std 9.994 0.005774 mg / g 0.000577697 B triangular

w comparator(ug) 2028.42 0.58

Balance contributionsStandard

uncertainty Units Type Distribution

R 0.0000222 mg A normal

Calib 0.0000844 mg B triangular

Masa combined

standard

unceratinty 8.72708E-05

Uncertainty budget for mass comparators prepared gravimetrically

Uncertainty

Case 2. Volumetric preparation

wµg ,c

[SRM – Na+]

Micropipette

Calibration

random

systematic

density

` ValueStandard

uncertaintyUnits

Relative Std

uncertainty u(x)/x

Type

evaluationDistribution

m 2.028 5.88E-03 mg 2.90E-03 A normal

Conc. Std 9.994 0.005774 mg / g 5.78E-04 B triangular

w comparator(ug) 2028.42 2.95

Balance contributionsStandard

uncertainty Units Type Distribution

syst 0.00573 A normal

random 0.00131 A normal

Masa combined

standard

unceratinty 0.00587784

Uncertainty budget for mass comparators prepared volumetrically

Conclusions

The results obtained with comparators and monitors prepared gravimetrically as well as volumetrically don’t show significant differences. The uncertainty of comparators using volumetric preparation have higher uncertainty that those prepared gravimetrically. Unsatisfactory results are shown for 2 of 23 elements: As and U in SRM 1633b, being larger for those prepared volumetrically. The cause of this low results could be the poor counting statistic. For results of SRM 2711a, Ba and U shown unsatisfactory results showed by En values higher that 1. Results for Cs, La, Na, and Sm shown results slightly above 1. The cause of this could be, as well the poor counting statistic.

The use of standard solutions for comparators and monitors is a good option and alternative, moreover when large quantity of samples must be analyzed (e.g. archaeological samples or environmental samples evaluation).

Conclusions

¡ Thank you for your

attention!