fundamentals of enaa
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Egyptian Atomic Energy Authority-Egypt Second Research Reactor ETRR-2 Department of Neutron Activation Analysis, Frank Laboratory of Neutron Physics Joint Institute for Nuclear Research, Dubna, Russia. Fundamentals of ENAA. Ahmed Ashry Abdel Aal. Supervisor Dr. Marina FRONTASYEVA. - PowerPoint PPT PresentationTRANSCRIPT
Fundamentals of ENAAFundamentals of ENAA
Ahmed Ashry Abdel AalAhmed Ashry Abdel Aal
Egyptian Atomic Energy Authority-Egypt Second Research Reactor ETRR-2Egyptian Atomic Energy Authority-Egypt Second Research Reactor ETRR-2
Department of Neutron Activation Analysis, Frank Laboratory of Neutron Department of Neutron Activation Analysis, Frank Laboratory of Neutron Physics Joint Institute for Nuclear Research, Dubna, RussiaPhysics Joint Institute for Nuclear Research, Dubna, Russia
Supervisor Dr. Supervisor Dr. Marina FRONTASYEVAMarina FRONTASYEVA
Theory of NAA:Theory of NAA:
Neutron capture by a target nucleus followed by the emission of gamma rays
Sources of IrradiationSources of Irradiation Although a variety of irradiation types have been introduced in Although a variety of irradiation types have been introduced in
activation analysis, activation analysis, the nuclear reactorthe nuclear reactor is still the most important is still the most important source of irradiation.source of irradiation.
C h3 C h4
C h0
C dS
C h1 C h2BS
DC VLR C BU
SU
SM
32
R
d28
d28
D
R 1
d16
R 2
BS
D D
C B
A A C C IBMPC
R 3
Scheme of irradiation facility REGATA at the IBR-2 Reactor with irradiation positions:
(1) Ch1 Cadmium Coated
(2) Ch2 conventional channel
Pulsed fast reactor IBR-2 Dubna
Sampling
Sample Preparation
Irradiation
Measurements
Data Analysis
Calculations
Steps of Neutron Activation Analysis
Rate of neutron capture for thermalRate of neutron capture for thermal and epithermal neutrons and epithermal neutrons
R = R = ΦΦthth σσ00 + + ΦΦepiepi ( I + 0.44 ( I + 0.44 σσ00 ) ) σσ00 is the 2200 msis the 2200 ms-1 -1 cross-section cross-section
ΦΦthth is the thermal neutron fluxis the thermal neutron flux ΦΦepiepi is the epithermal neutron flux per unit ln Eis the epithermal neutron flux per unit ln E I I is resonance integral defined as follows: is resonance integral defined as follows:
Where Where σσ(E)(E) is the activation cross section as a function of neutron is the activation cross section as a function of neutron energy, excluding the 1/v contribution.energy, excluding the 1/v contribution.
An example of Gamma-spectra of rock material recorded 6 days after 2 days’ irradiation:A – pile neutron activation; B – epithermal neutron activation(from Epithermal Neutron Activation Analysis of Geological Material, 1971)
Cadmium ratio:
The epithermal activation properties of a nuclide The epithermal activation properties of a nuclide can be conveniently expressed by means of the can be conveniently expressed by means of the cadmium ratio:cadmium ratio:
RCd = th 0 + epi (I + 0.44* 0)
epi (I + 0.44* 0)
This ratio is used To compare ability to activate nuclide by epithermal activation compared to thermal
Advantage Factor Effectiveness of ENAA
Fa = (RCd)d / (RCd)D
d is for interference nuclideD is for the nuclide experimenter is searching
More than 20 trace elements in silicate rocks
have Fa > 20A table of advantage factors for various isotopescan be found in Steinnes, Epithermal NeutronActivation Analysis of Geological Material
Table 1: epithermal activation possibilities for elements which can be Table 1: epithermal activation possibilities for elements which can be determined by reactor Neutron Activation Analysis. The calculated determined by reactor Neutron Activation Analysis. The calculated Advantage Factor are based on RAdvantage Factor are based on RCdCd
AUAU= 3.00, corresponding to R= 3.00, corresponding to RCdCd=72 =72
for a nuclide following 1/v Law.for a nuclide following 1/v Law.
Advantages of ENAA:Advantages of ENAA:
Provides improvement in the precision and sensitivity in instrumental activation analysis
Reduction of high activity levels caused by more numerous major and minor elements
Thermal fission interference of U-235 reduced,
would have produced radioactive daughter products, gamma rays, and fast neutrons
Limitations of ENAA:Limitations of ENAA:
May cause fast fission interference with Thorium-232
Highly active Cadmium which gives off gamma rays.
Needs to be near the core for epithermal flux, Cd lower the neutron flux which nuclear reactor operators may not want.
Cd can melt Cd burnup, becomes less effective over long
periods of use Time needed to take off Cd foil prevents the
detection of short-lived nuclids (half-lives < 20 s).
Sources of uncertainty:Sources of uncertainty:
Possible interference from (n, αPossible interference from (n, α ) and (n,) and (n,PP) reactions will be ) reactions will be more serious in the case of ENAA.more serious in the case of ENAA.Interference from the second order reactions of the typeInterference from the second order reactions of the type
In the In the determination of element No. Z, will in general not be the determination of element No. Z, will in general not be the same as in the case of thermal neutron irradiation.same as in the case of thermal neutron irradiation.If a sample contains a significant amount of light nuclides such If a sample contains a significant amount of light nuclides such as as 11H, moderation of neutrons within the sample might H, moderation of neutrons within the sample might introduce error due to distortion of of the epithermal spectrum.introduce error due to distortion of of the epithermal spectrum.The epithermal neutron energy spectrum may be interfered by The epithermal neutron energy spectrum may be interfered by resonance absorption either by surrounding materials or in the resonance absorption either by surrounding materials or in the sample itself.sample itself.
Applications:Applications: The technique could be used in the The technique could be used in the Determination of Au, As,
Sb in plants. Determination of l, In, Br, Sr, U, Th and Si in geological
samples. Determination of contents of iodine in non-thyroid tissues and
serum. Determination of I, Br and Sr in biological samples. In the determination of Si, the thermal neutron activation cross
section of the reaction Si30(n,) Si31 is small (0.108 b). Moss Biomonitoring of long-lived radionuclides near Chernobyl Determination of Halogens in Soils and Mosses. Foodstuff Quality. NAA in Assessment of the Condition of Natural Ecosystems. Biotechnologies.
References:References: An Overview of Neutron Activation Analysis by Michael D. Glascock, University
of Missouri Research Reactor (MURR) Epithermal neutron activation analysis of Geological materials by E.Steinnes,
Institute of Atomenergi, isotope laboratories, Norway. Instrumental and organizational aspects of a neutron activation analysis
laboratory by Peter Bode, Interfaculaire reactor institute Delft university of technology.
Epithermal Neutron Activation Analysis at the IBR-2 Reactor of the Frank Laboratory of Neutron Physics at the Joint Institute for Nuclear Research (Dubna) M. V. Frontasyeva, Joint Institute for Nuclear Research, Dubna, Russia.
Epithermal Neutron Activation Analysis and its Application in the Miniature Neutron Source Reactor by XIAOLIN HOU,* KE WANG,** CHIFANG CHAI**
More information... http://ocw.mit.edu/NR/rdonlyres/Earth--Atmospheric--and-Planetary-Sciences/12-
091January--IAP--2005/82FA55AA-76A0-4A23-B1E7-1550E587E246/0/enaa.pdf
http://archaeometry.missouri.edu/naa_overview.html http://www.wpi.edu/Academics/Depts/ME/Nuclear/Reactor/Labs/R-naa.html http://www.reak.bme.hu/Wigner_Course/WignerManuals/Budapest/
NEUTRON_ACTIVATION_ANALYSIS.htm. http://www.jeffreycreid.com/Analytical_Methods/NAA_theory.html
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