Neutron activation analysis

neutron activation analysis

1. Neutron Activation Analysis S CONTENTS PAGE Introduction ………………………………………………………………03 History……………………………………………………………………….04 Principle…………………………………………………………………… .05 Applications…………………………………………...11 Advantages………………………………………….....13 Limit ations……………………………………………..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. P rinciple 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. T his 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: Neutron Activation Analysis

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. R eferences Hamidatou , L, ( ‎ 2013). Concept, instrument ation 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. R etrieved Oct 23, 2016. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5