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Joint Institute for Nuclear Research in Dubna FRANK LABORATORY OF NEUTRON PHYSICS

NEUTRON ACTIVATION ANALYSIS (NAA) IN LIFE SCIENCES

Prepared by: Kgakgamatso Mmono (NWU) Supervisor: Prof M. V. Frontasyeva. (FLNP)

SUMMER PRACTICE, 24 Septebmer-14 October 2012

OUTLI NE

• 1. I ntroduction
• 2. Neutron Activation Analysis
• 3. Gam m a-Spectrom etry
• 4. Applications of NAA at I BR-2
• 5. Absolute Method
• 6. Conclusion

• I lґja Mikhailovich Frank (1908-1990)
• Founder of FLNP at JI NR (1956)
• The Nobel Prize winner in Physics (1958)
• 1. INTRODUCTION

PIONEERS OF NAA

George de Hevesy 1885-1966 The Nobel Prize in Chemistry 1943 Hilde Levi 1909-2003

• 2. NEUTRON ACTIVATION ANALYSIS
• It is a sensitive multi-element analytical technique used for

both qualitative and quantitative analysis of major, minor, trace and rare elements in samples from almost every field

• f scientific or technical interest.
• NAA was discovered in 1936 when Hevesy and Levi found

that samples containing certain rare earth elem ents becam e highly radioactive after exposure to a source of neutrons.

(a). NAA Methods

• Relative Method usually performed by firstly irradiating

known amounts of the sample and element standards simultaneously followed by comparing their gamma ray spectrums counted under the same conditions.

• ko-standardization method is based on irradiation of a

sample with a neutron flux monitor such as gold and the use of a nuclear constant called the ko-factor.

• The absolute method is a direct analysis of the irradiated

samples without using any element standard reference.

Relative Method

The NAA the method Performed at IBR-2 Reactor the activity can be given by :

[ ]

1

. .

−

=

R S S R s

H C m A A

(b). NAA Principle

Neutron Flux Spectrum

• Thermal (0,025 eV – 0,5 eV)
• Epithermal (0,5 eV – 10 keV)
• Fast (10 keV – 25 MeV)

NEUTRON FLUX

• Differences in neutron flux between samples and

reference elemental standard can be corrected using flux monitors.

• The normalised activity values are used to

calculate the concentration in the sample by :

[ ]

( ) ( )

[ ]

R norm s norm S R R s

A A m m C C . . =

REGATA REGATA

C h3 C h4 C h0 C d S C h1 C h2 BS DC V L R C B U SU SM 32 R d28 d28 D R 1 d16 R 2 BS D D C B A A C C IBM PC R 3

( c) . I BR-2 Pulsed Fast Reactor

( d) . I NAA Procedure

.

.

10

Sample preparation Neutron irradiation of samples Decay of radioactivity Decay of radioactivity Decay periods between 15s – 7 days Decay periods between 15s – 7 days Measurement of γ-ray spectra of samples and standards with HPGe-detector Measurement of γ-ray spectra of samples and standards with HPGe-detector Evaluation of the γ-ray spectra using a computer program Evaluation of the γ-ray spectra using a computer program Calculation of element content giving results in µg/ g Calculation of element content giving results in µg/ g Decay tim e Count tim e

(e). Sample Preparation

Chemical laboratory of the dept. NAA and Applied Research and some equipment for sample preparation.

• 3. GAMMA SPECTROMETRY

Detector Detector Calibration

• 4. APPLICATI ONS OF NNA AT IBR-

2

Logic diagram of software for automation of NAA

• 5. THE ABSOLUTE METHOD
• Consists of absolute gamma ray measurements

and direct calculation of the element concentrations with the help of reactor core simulations and available nuclear data

• Investigated at SAFAR-I Research Reactor
• Monte Carlo N-Particle (MCNP), Fispact

• 6. CONCLUSIONS
• Neutron Activation Analysis (NAA) is a useful method for

the simultaneous determination of major, minor and trace elements of geological, environmental and biological samples in ppb-ppm range with or without chemical separation.

• Automation of neutron activation analysis will im prove the

quality of the laboratory and as well increase the quantity of the samples analysed in the department of neutron activation analysis & Applied Research(DUBNA).