neutron activation analysis

1. NeutronActivationAnalysis
SCONTENTS PAGE
Introduction ………………………………………………………………03
History……………………………………………………………………….04
Principle…………………………………………………………………… .05
Applications…………………………………………...11
Advantages………………………………………….....13
Limitations……………………………………………..14

2. Introduction
Activation Analysis: an analytical technique in
which radiation is induced by bombardment.
Neutron Activation Analysis(NAA): The method
which uses neutron for bombardment.
Nuclear process: used for determining the
concentrations of elements in a vast amount of
materials.

3. History
• NAA was discovered in 1936 by George Charles
de Hevesy and Levi.
• They found that samples containing certain rare
elements became highly radioactive after
exposure to source of neutrons.
• This observation led to the use of induced
radioactivity for the identification of elements

4. Principle
• The specimen is placed into a suitable irradiation
facility bombarded with neutrons, this makes
artificial radioisotopes of the element.
• Irradiation of this radioisotopes leads to emission
of gamma rays.

5. Cont.…
• Sample must be selected carefully. About 50mg
is a sufficient sample.
• Sample is then encapsulated in a vial made of
either polyethylene or quartz.
• The sample and a standard are then packed and
irradiated in a suitable reactor at a
constant(neutron flux)

6. Cont..
• Maximum neutron flux for reactor(uranium
fission) is in the order of 10-12 neutron
• Neutron generated are low kinetic energy
(0.5eV). These are thermal neutron
• Upon irradiation these neutrons interact with
target nucleus

7. Cont..
• This collisions forms a compound nucleus
excited, which de-excite into a stable form by
emitting a prompt particle (prompt gamma
photons).
• The newly formed radioactive nucleus decays by
the emission of the delayed gamma photons. This
decay process is slower than the initial process
and depends on the half life of radioactive
nucleus.

8. Cont..
• Once irradiated the sample is left for a specific
decay period then placed into a detector, which
measure the nuclear decay according to the
emitted particles.

9. Figure: NeutronActivationAnalysis

10. Applications
• Archaeology: to characterize archaeological
specimens and to relate the artifacts to sources.
• Soil science: stable tracers, such as bromides are
analyzed by NAA.
• Geology: By studying the process involved in the
formation of different rocks, through the analysis
of rare earth elements.

11. Cont..
• Environmental analysis: The use of radiotracers
to study the fate of hazardous elements in the
waste material.
• Semiconductor industry: to measures tracer
used as deposit for semiconductor.
• Epidemiology: the use of radiotracers to test new
pharmaceuticals and dosage forms being
developed for commercial distribution.

12. Advantages
• Small sample sizes
• Can analyze multiple elements samples
• Non-destructive
• No need of chemical treatment
• High sensitivity
• High precision

13. Limitations
• Detection limit
• Bulk matrix
• Interferences can occurs when different
component sample elements produce similar
gamma rays.

14. References
• Hamidatou, L, ( 2013). Concept, instrumentation and
technique of neutron activation analysis. Retrieved May 22,
2017. https://www.intechopen.com/.../concepts-
instrumentation-and-techniques-of-neutron-a...
• Sahiner, H,( 2015). Neutron activation analysis. Retrieved Oct
23, 2016. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5